Science.gov

Sample records for hybrid composites aged

  1. Isothermal and hygrothermal agings of hybrid glass fiber/carbon fiber composite

    NASA Astrophysics Data System (ADS)

    Barjasteh, Ehsan

    anhydride/epoxy network used in composite-reinforced conductor cables was investigated to determine the extent of thermal oxidative (surface effect) and non-oxidative (bulk effect) degradation. Thermal oxidation tests were performed in air-circulating and vacuum ovens at 180°C and 200ºC (the maximum emergency temperature for ACCC conductors). The extent of oxidation during aging was determined by monitoring the thickness of the oxidized layer. Results showed that the oxidized layer thickness did not increase monotonically as a function of exposure time, and even decreased for a limited period of time. A phenomenological reaction-diffusion model was implemented to predict the thickness of oxidized layer, and the calculated results were compared with measurements for aging times up to 10,000 hours. The accuracy of the reaction-diffusion-based thickness values for the isothermally aged epoxy specimen was affected by the permeability properties of the oxidized material, and to a lesser extent by the degree of oxidation. The diffusivity varied because of changes in the density of the oxidized layer, the macro-void content, crack formation, and the molecular structures. To investigate the effects on diffusivity, the morphology of the oxidized layer and the void content was monitored over time. In addition, the density of the oxidized specimens was calculated by direct measurements of volume and weight during exposure. An empirically based volume-loss model was developed to predict the changes in volume of the specimen as a function of aging times and hence to predict the effects on the oxidized layer thickness. Volume-loss measurements provide an indication of material degradation by demonstrating a direct measurement of shrinkage rates and insight into crack initiation, as opposed to typical weight-loss measurements that provide no insight into material failure. Thermal oxidation of a unidirectional carbon-fiber/glass-fiber hybrid composite was also investigated in this study

  2. Hybridized polymer matrix composites

    NASA Technical Reports Server (NTRS)

    House, E. E.; Hoggatt, J. T.; Symonds, W. A.

    1980-01-01

    The extent to which graphite fibers are released from resin matrix composites that are exposed to fire and impact conditions was determined. Laboratory simulations of those conditions that could exist in the event of an aircraft crash and burn situation were evaluated. The effectiveness of various hybridizing concepts in preventing this release of graphite fibers were also evaluated. The baseline (i.e., unhybridized) laminates examined were prepared from commercially available graphite/epoxy, graphite/polyimide, and graphite/phenolic materials. Hybridizing concepts investigated included resin fillers, laminate coatings, resin blending, and mechanical interlocking of the graphite reinforcement. The baseline and hybridized laminates' mechanical properties, before and after isothermal and humidity aging, were also compared. It was found that a small amount of graphite fiber was released from the graphite/epoxy laminates during the burn and impact conditions used in this program. However, the extent to which the fibers were released is not considered a severe enough problem to preclude the use of graphite reinforced composites in civil aircraft structure. It also was found that several hybrid concepts eliminated this fiber release. Isothermal and humidity aging did not appear to alter the fiber release tendencies.

  3. Hybrid matrix fiber composites

    DOEpatents

    Deteresa, Steven J.; Lyon, Richard E.; Groves, Scott E.

    2003-07-15

    Hybrid matrix fiber composites having enhanced compressive performance as well as enhanced stiffness, toughness and durability suitable for compression-critical applications. The methods for producing the fiber composites using matrix hybridization. The hybrid matrix fiber composites include two chemically or physically bonded matrix materials, whereas the first matrix materials are used to impregnate multi-filament fibers formed into ribbons and the second matrix material is placed around and between the fiber ribbons that are impregnated with the first matrix material and both matrix materials are cured and solidified.

  4. Hybridized polymer matrix composite

    NASA Technical Reports Server (NTRS)

    Stern, B. A.; Visser, T.

    1981-01-01

    Under certain conditions of combined fire and impact, graphite fibers are released to the atmosphere by graphite fiber composites. The retention of graphite fibers in these situations is investigated. Hybrid combinations of graphite tape and cloth, glass cloth, and resin additives are studied with resin systems. Polyimide resins form the most resistant composites and resins based on simple novolac epoxies the least resistant of those tested. Great improvement in the containment of the fibers is obtained in using graphite/glass hybrids, and nearly complete prevention of individual fiber release is made possible by the use of resin additives.

  5. Hybridized polymer matrix composites

    NASA Technical Reports Server (NTRS)

    London, A.

    1981-01-01

    Design approaches and materials are described from which are fabricated pyrostatic graphite/epoxy (Gr/Ep) laminates that show improved retention of graphite particulates when subjected to burning. Sixteen hybridized plus two standard Gr/Ep laminates were designed, fabricated, and tested in an effort to eliminate the release of carbon (graphite) fiber particles from burned/burning, mechanically disturbed samples. The term pyrostatic is defined as meaning mechanically intact in the presence of fire. Graphite particulate retentive laminates were constructed whose constituent materials, cost of fabrication, and physical and mechanical properties were not significantly different from existing Gr/Ep composites. All but one laminate (a Celion graphite/bis-maleimide polyimide) were based on an off-the-shelf Gr/Ep, the AS-1/3501-5A system. Of the 16 candidates studied, four thin (10-ply) and four thick (50-ply) hybridized composites are recommended.

  6. Hybridized polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Henshaw, J.

    1983-01-01

    Methods of improving the fire resistance of graphite epoxy composite laminates were investigated with the objective of reducing the volume of loose graphite fibers disseminated into the airstream as the result of a high intensity aircraft fuel fire. Improvements were sought by modifying the standard graphite epoxy systems without significantly negating their structural effectiveness. The modifications consisted primarily of an addition of a third constituent material such as glass fibers, glass flakes, carbon black in a glassy resin. These additions were designed to encourage coalescense of the graphite fibers and thereby reduce their aerodynamic float characteristics. A total of 38 fire tests were conducted on thin (1.0 mm) and thick (6.0 mm) hybrid panels.

  7. Fracture Resistance of Hybrid Glass Matrix Composite and Its Degradation Due to Thermal Ageing and Thermal Shock

    NASA Astrophysics Data System (ADS)

    Dlouhý, Ivo; Chlup, Zdenêk; Atiq, Shabbar; Boccaccini, Aldo R.

    In brittle matrix composites reinforced by continuous ceramic fibres, the favourable fracture behaviour is provided by the presence of weak fibre/matrix interfaces, which lead to the fibre pullout effect [1]. The thermal stability and high temperature mechanical properties of silicate matrix composites reinforced by carbon and SiC based fibres in oxidising environments have been investigated quite extensively in the past by conducting thermal aging and thermal cycling experiments over a wide range of temperatures [2-5]. A common result of investigations conducted at temperatures in the range 500-700°C is that there is a decrease of tensile and flexural strength of the composites. It has been shown that this is the consequence of oxidation of the fibres, in case of carbon fibre reinforced composites, or of degradation of the fibre/matrix interphase, which is in fact a carbon-rich nanometric interfacial layer, in SiC fibre reinforced composites [2-5].

  8. Intercalated hybrid graphite fiber composite

    NASA Technical Reports Server (NTRS)

    Gaier, James R. (Inventor)

    1993-01-01

    The invention is directed to a highly conductive lightweight hybrid material and methods of producing the same. The hybrid composite is obtained by weaving strands of a high strength carbon or graphite fiber into a fabric-like structure, depositing a layer of carbon onto the structure, heat treating the structure to graphitize the carbon layer, and intercalating the graphitic carbon layer structure. A laminate composite material useful for protection against lightning strikes comprises at least one layer of the hybrid material over at least one layer of high strength carbon or graphite fibers. The composite material of the present invention is compatible with matrix compounds, has a coefficient of thermal expansion which is the same as underlying fiber layers, and is resistant to galvanic corrosion in addition to being highly conductive. These materials are useful in the aerospace industry, in particular as lightning strike protection for airplanes.

  9. Shape Memory Composite Hybrid Hinge

    NASA Technical Reports Server (NTRS)

    Fang, Houfei; Im, Eastwood; Lin, John; Scarborough, Stephen

    2012-01-01

    There are two conventional types of hinges for in-space deployment applications. The first type is mechanically deploying hinges. A typical mechanically deploying hinge is usually composed of several tens of components. It is complicated, heavy, and bulky. More components imply higher deployment failure probability. Due to the existence of relatively moving components among a mechanically deploying hinge, it unavoidably has microdynamic problems. The second type of conventional hinge relies on strain energy for deployment. A tape-spring hinge is a typical strain energy hinge. A fundamental problem of a strain energy hinge is that its deployment dynamic is uncontrollable. Usually, its deployment is associated with a large impact, which is unacceptable for many space applications. Some damping technologies have been experimented with to reduce the impact, but they increased the risks of an unsuccessful deployment. Coalescing strain energy components with shape memory composite (SMC) components to form a hybrid hinge is the solution. SMCs are well suited for deployable structures. A SMC is created from a high-performance fiber and a shape memory polymer resin. When the resin is heated to above its glass transition temperature, the composite becomes flexible and can be folded or packed. Once cooled to below the glass transition temperature, the composite remains in the packed state. When the structure is ready to be deployed, the SMC component is reheated to above the glass transition temperature, and it returns to its as-fabricated shape. A hybrid hinge is composed of two strain energy flanges (also called tape-springs) and one SMC tube. Two folding lines are placed on the SMC tube to avoid excessive strain on the SMC during folding. Two adapters are used to connect the hybrid hinge to its adjacent structural components. While the SMC tube is heated to above its glass transition temperature, a hybrid hinge can be folded and stays at folded status after the temperature

  10. Computer code for intraply hybrid composite design

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1981-01-01

    A computer program is described for intraply hybrid composite design (INHYD). The program includes several composite micromechanics theories, intraply hybrid composite theories, and a hygrothermomechanical theory. These theories provide INHYD with considerable flexibility and capability which the user can exercise through several available options. Key features and capabilities of INHYD are illustrated through selected samples.

  11. Hybrid Composite Cryogenic Tank Structure

    NASA Technical Reports Server (NTRS)

    DeLay, Thomas

    2011-01-01

    A hybrid lightweight composite tank has been created using specially designed materials and manufacturing processes. The tank is produced by using a hybrid structure consisting of at least two reinforced composite material systems. The inner composite layer comprises a distinct fiber and resin matrix suitable for cryogenic use that is a braided-sleeve (and/or a filamentwound layer) aramid fiber preform that is placed on a removable mandrel (outfitted with metallic end fittings) and is infused (vacuum-assisted resin transfer molded) with a polyurethane resin matrix with a high ductility at low temperatures. This inner layer is allowed to cure and is encapsulated with a filamentwound outer composite layer of a distinct fiber resin system. Both inner and outer layer are in intimate contact, and can also be cured at the same time. The outer layer is a material that performs well for low temperature pressure vessels, and it can rely on the inner layer to act as a liner to contain the fluids. The outer layer can be a variety of materials, but the best embodiment may be the use of a continuous tow of carbon fiber (T-1000 carbon, or others), or other high-strength fibers combined with a high ductility epoxy resin matrix, or a polyurethane matrix, which performs well at low temperatures. After curing, the mandrel can be removed from the outer layer. While the hybrid structure is not limited to two particular materials, a preferred version of the tank has been demonstrated on an actual test tank article cycled at high pressures with liquid nitrogen and liquid hydrogen, and the best version is an inner layer of PBO (poly-pphenylenebenzobisoxazole) fibers with a polyurethane matrix and an outer layer of T-1000 carbon with a high elongation epoxy matrix suitable for cryogenic temperatures. A polyurethane matrix has also been used for the outer layer. The construction method is ideal because the fiber and resin of the inner layer has a high strain to failure at cryogenic

  12. Flexural performance of woven hybrid composites

    NASA Astrophysics Data System (ADS)

    Maslinda, A. B.; Majid, M. S. Abdul; Dan-mallam, Y.; Mazawati, M.

    2016-07-01

    This paper describes the experimental investigation of the flexural performance of natural fiber reinforced polymer composites. Hybrid composites consist of interwoven kenaf/jute and kenaf/hemp fibers was prepared by infusion process using epoxy as polymer matrix. Woven kenaf, jute and hemp composites were also prepared for comparison. Both woven and hybrid composites were subjected to three point flexural test. From the result, bending resistance of hybrid kenaf/jute and kenaf/hemp composites was higher compared to their individual fiber. Hybridization with high strength fiber such as kenaf enhanced the capability of jute and hemp fibers to withstand bending load. Interlocking between yarns in woven fabric make pull out fibers nearly impossible and increase the flexural performance of the hybrid composites.

  13. Hybrid composites prepared from Industrial waste: Mechanical and swelling behavior

    PubMed Central

    Ahmed, Khalil

    2013-01-01

    In this assessment, hybrid composites were prepared from the combination of industrial waste, as marble waste powder (MWP) with conventional fillers, carbon black (CB) as well as silica as reinforcing material, incorporated with natural rubber (NR). The properties studied were curing, mechanical and swelling behavior. Assimilation of CB as well as silica into MWP containing NR compound responded in decreasing the scorch time and cure time besides increasing in the torque. Additionally, increasing the CB and silica in their respective NR hybrid composite increases the tensile, tear, modulus, hardness, and cross-link density, but decreases the elongation and swelling coefficient. The degradation property e.g., thermal aging of the hybrid composite was also estimated. The overall behavior at 70 °C aging temperature signified that the replacement of MS by CB and silica improved the aging performance. PMID:25750756

  14. Aging Effects in Polymer Composites

    NASA Technical Reports Server (NTRS)

    Chamis, Chistos C.; McManus, Hugh L.

    1999-01-01

    Simulation of composites degradation due to aging are described. Laminate geometry, material properties, and matrix degradation states are specified as functions of position and time. Matrix shrinkage and property changes are modeled as functions of the degradation states. Aging effects at the laminate, ply, and micro levels are evaluated, to determine failure of any kind. The results obtained show substantial ply stress built up as a result of aging accompanied by comparable laminate strength degradation in matrix dominated composite strengths.

  15. Dry sliding wear of heat treated hybrid metal matrix composites

    NASA Astrophysics Data System (ADS)

    Naveed, Mohammed; Khan, A. R. Anwar

    2016-09-01

    In recent years, there has been an ever-increasing demand for enhancing mechanical properties of Aluminum Matrix Composites (AMCs), which are finding wide applications in the field of aerospace, automobile, defence etc,. Among all available aluminium alloys, Al6061 is extensively used owing to its excellent wear resistance and ease of processing. Newer techniques of improving the hardness and wear resistance of Al6061 by dispersing an appropriate mixture of hard ceramic powder and whiskers in the aluminium alloy are gaining popularity. The conventional aluminium based composites possess only one type of reinforcements. Addition of hard reinforcements such as silicon carbide, alumina, titanium carbide, improves hardness, strength and wear resistance of the composites. However, these composites possessing hard reinforcement do posses several problems during their machining operation. AMCs reinforced with particles of Gr have been reported to be possessing better wear characteristics owing to the reduced wear because of formation of a thin layer of Gr particles, which prevents metal to metal contact of the sliding surfaces. Further, heat treatment has a profound influence on mechanical properties of heat treatable aluminium alloys and its composites. For a solutionising temperature of 5500C, solutionising duration of 1hr, ageing temperature of 1750C, quenching media and ageing duration significantly alters mechanical properties of both aluminium alloy and its composites. In the light of the above, the present paper aims at developing aluminium based hybrid metal matrix composites containing both silicon carbide and graphite and characterize their mechanical properties by subjecting it to heat treatment. Results indicate that increase of graphite content increases wear resistance of hybrid composites reinforced with constant SiC reinforcement. Further heat treatment has a profound influence on the wear resistance of the matrix alloy as well as its hybrid composites

  16. Hybrid Ceramic Matrix Fibrous Composites: an Overview

    NASA Astrophysics Data System (ADS)

    Naslain, R.

    2011-10-01

    Ceramic-Matrix Composites (CMCs) consist of a ceramic fiber architecture in a ceramic matrix, bonded together through a thin interphase. The present contribution is limited to non-oxide CMCs. Their constituents being oxidation-prone, they are protected by external coatings. We state here that CMCs display a hybrid feature, when at least one of their components is not homogeneous from a chemical or microstructural standpoint. Hybrid fiber architectures are used to tailor the mechanical or thermal CMC-properties whereas hybrid interphases, matrices and coatings to improve CMC resistance to aggressive environments.

  17. Polymer hybrid nano/micro composites

    SciTech Connect

    Dzenis, Y.A.; Reneker, D.H.

    1994-12-31

    Nanocomposites based on ceramic and metal matrices attracted considerable attention during the past decade. Polymer based nanocomposites are much less well-known. Recently, a method of electrospinning of thin polymer fibers has been developed. Continuous, oriented fibers with diameters ranging from 50 nanometers to several microns have been prepared from over 30 different synthetic and natural polymers, including high temperature high modulus polyimide and polyaramid (Kevlar) fibers. The possible applications of these small fibers in hybrid polymer hierarchical composites are discussed. Micromechanics models of hybrid composites are developed based on the models for two component composites and on the principle of effective homogeneity. Effective thermoviscoelastic characteristics of nano and microfiber composite as well as nanofiber and microparticulate composites are calculated. ``Strong`` hybrid effects are observed in the dependence of effective moduli, loss factor, creep factor, and thermal expansion coefficient on fractional content of fibers of different diameters. The extrema are located at the higher fractions of larger reinforcing elements. Similarities of composite microstructures having synergistic ``extremal`` properties with some biological composites are noted.

  18. Characterization of Hybrid CNT Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Grimsley, Brian W.; Cano, Roberto J.; Kinney, Megan C.; Pressley, James; Sauti, Godfrey; Czabaj, Michael W.; Kim, Jae-Woo; Siochi, Emilie J.

    2015-01-01

    Carbon nanotubes (CNTs) have been studied extensively since their discovery and demonstrated at the nanoscale superior mechanical, electrical and thermal properties in comparison to micro and macro scale properties of conventional engineering materials. This combination of properties suggests their potential to enhance multi-functionality of composites in regions of primary structures on aerospace vehicles where lightweight materials with improved thermal and electrical conductivity are desirable. In this study, hybrid multifunctional polymer matrix composites were fabricated by interleaving layers of CNT sheets into Hexcel® IM7/8552 prepreg, a well-characterized toughened epoxy carbon fiber reinforced polymer (CFRP) composite. The resin content of these interleaved CNT sheets, as well as ply stacking location were varied to determine the effects on the electrical, thermal, and mechanical performance of the composites. The direct-current electrical conductivity of the hybrid CNT composites was characterized by in-line and Montgomery four-probe methods. For [0](sub 20) laminates containing a single layer of CNT sheet between each ply of IM7/8552, in-plane electrical conductivity of the hybrid laminate increased significantly, while in-plane thermal conductivity increased only slightly in comparison to the control IM7/8552 laminates. Photo-microscopy and short beam shear (SBS) strength tests were used to characterize the consolidation quality of the fabricated laminates. Hybrid panels fabricated without any pretreatment of the CNT sheets resulted in a SBS strength reduction of 70 percent. Aligning the tubes and pre-infusing the CNT sheets with resin significantly improved the SBS strength of the hybrid composite To determine the cause of this performance reduction, Mode I and Mode II fracture toughness of the CNT sheet to CFRP interface was characterized by double cantilever beam (DCB) and end notch flexure (ENF) testing, respectively. Results are compared to the

  19. Influence of defect structure on ferroelectric aging in donor-acceptor hybrid-doped PZT

    NASA Astrophysics Data System (ADS)

    Anil, A.; Vani, K.; Kumar, V.

    2016-06-01

    In the present work, we report the aging effect in manganese (Mn) and niobium (Nb) hybrid-doped PZT composition. Interestingly, it is observed that the ferroelectric aging depends on the acceptor/donor ratio. In hybrid-doped PZT, at high donor dopant concentrations, aging is not observed. The underlying mechanism is correlated with the defect chemistry of the system. It is also observed that tuning the defect chemistry is an effective strategy to realize piezoceramics with enhanced dielectric and piezoelectric characteristics.

  20. Body composition in healthy aging.

    PubMed

    Baumgartner, R N

    2000-05-01

    Health risks in elderly people cannot be evaluated simply in conventional terms of body fatness or fat distribution. Elderly people have less muscle and bone mass, expanded extracellular fluid volumes, and reduced body cell mass compared to younger adults. These nonfat components of body composition play critical roles, influencing cognitive and physical functional status, nutritional and endocrine status, quality of life, and comorbidity in elderly people. Different patterns of "disordered body composition" have different relationships to these outcomes and may require different, tailored approaches to treatment that combine various exercise regimens and dietary supplements with hormone replacement or appetite-stimulating drugs. Skeletal muscle atrophy, or "sarcopenia," is highly prevalent in the elderly population, increases with age, and is strongly associated with disability, independent of morbidity. Elders at greatest risk are those who are simultaneously sarcopenic and obese. The accurate identification of sarcopenic obesity requires precise methods of simultaneously measuring fat and lean components, such as dual-energy X-ray absorptiometry.

  1. Development and characterization of hybrid thermoplastic composites

    NASA Astrophysics Data System (ADS)

    Karkhanis, Priyanka Chandrashekhar

    This work is aimed at studying the possibility of using interply hybrid woven thermoplastic semi-pregs in secondary structures in aircrafts at TenCate Advanced Composites, Netherlands and Purdue University. Three different interply hybrids were designed from combination of Cetex(c) carbon-PPS semi-preg, Owen corning's woven glass with PPS sheets and discontinuous chopped Cetex(c) carbon-PPS semi-preg to get desired flexural, out of plane and bearing properties. The design calculations are done based on classical laminate theory and the selection of materials to be used with carbon-PPS was done based on cost and availability. The Hybrid laminate performances are analyzed and compared to the conventional Cetex (c) Carbon-PPS semi-preg laminates. Observations are reported on three point bend test (European standard 2562), four point bend test(ASTM D6415-99) and bearing test (Airbus standards AITM 1-0009) for the laminates and it was found that hybrid laminates show a reduction of 5-10% in bending stiffness, 20-40% reduction in out-of-plane strength and 2-5%reduction in bearing with a cost reduction of 20-30%. The research identifies and documents the different factors responsible for failures and reduction in strength in the Hybrids.

  2. Manufacturing of aluminium nano hybrid composites: a state of review

    NASA Astrophysics Data System (ADS)

    Madhukar, P.; Selvaraj, N.; Rao, CSP

    2016-09-01

    This paper gives the details of hybrid composites, their fabrication methods and evaluation of mechanical, tribological behaviour and machining characteristics. Investigations on the various aspects of Hybrid composites furnish several conclusions regarding the influence of various parameters on the performance of the composites. Mostly micro structures of the hybrid composites fabricated through casting routes have been found to be stable with the distribution of uniformed reinforce particles. therefore, the hybrid composites can be constructed with various combinations of reinforcements to carry out desirable mechanical properties. The density of Hybrid composites increases with increasing reinforcements such as SiC, TiC, B4C....etc, while incorporation of partial reinforcements like fly ash, mica, rice husk, etc. reduces the density of composites. The study also reports that the hybrid composites can be treated as a replacement for regular composite materials in different advanced applications.

  3. Resin infusion of layered metal/composite hybrid and resulting metal/composite hybrid laminate

    NASA Technical Reports Server (NTRS)

    Cano, Roberto J. (Inventor); Grimsley, Brian W. (Inventor); Weiser, Erik S. (Inventor); Jensen, Brian J. (Inventor)

    2009-01-01

    A method of fabricating a metal/composite hybrid laminate is provided. One or more layered arrangements are stacked on a solid base to form a layered structure. Each layered arrangement is defined by a fibrous material and a perforated metal sheet. A resin in its liquid state is introduced along a portion of the layered structure while a differential pressure is applied across the laminate structure until the resin permeates the fibrous material of each layered arrangement and fills perforations in each perforated metal sheet. The resin is cured thereby yielding a metal/composite hybrid laminate.

  4. Ballistic damage in hybrid composite laminates

    NASA Astrophysics Data System (ADS)

    Phadnis, Vaibhav A.; Pandya, Kedar S.; Naik, Niranjan K.; Roy, Anish; Silberschmidt, Vadim V.

    2015-07-01

    Ballistic damage of hybrid woven-fabric composites made of plain-weave E-glass- fabric/epoxy and 8H satin-weave T300 carbon-fabric/epoxy is studied using a combination of experimental tests, microstructural studies and finite-element (FE) analysis. Ballistic tests were conducted with a single-stage gas gun. Fibre damage and delamination were observed to be dominating failure modes. A ply-level FE model was developed, with a fabric-reinforced ply modelled as a homogeneous orthotropic material with capacity to sustain progressive stiffness degradation due to fibre/matrix cracking, fibre breaking and plastic deformation under shear loading. Simulated damage patterns on the front and back faces of fabric-reinforced composite plates provided an insight into their damage mechanisms under ballistic loading.

  5. PP composites with Hybrid Nanofillers: NTC phenomenon

    SciTech Connect

    Sarlin, Juha; Immonen, Kirsi

    2010-06-02

    Electric conductive plastic composites have a wide potential for commercial applications, some examples are EMI shielding housings and components in automotive industry and in consumer electronics, equipments in health care sector and fuel cell components. A phenomenon in conductive composites, especially in composites with carbon based fillers, is change of thermal induced change in conductivity as a result of morphological transitions. Usually the observed changes are practically irreversible. The phenomenon may cause increasing resistivity, usually called as 'positive temperature coefficient' (PTC) or decreasing resistivity, called 'negative temperature coefficient' (NTC), where the new morphology created by heat treatment is more favorable for electric conductivity compared to the original state. The existence of NTC is a sing of the lost potential in material design and processing. Therefore detailed information about the phenomenon gives us tools to develop high performance conductive materials. It this paper we discuss about NTC phenomenon observed in PP composites with CNT or in-situ synthesized CNT-PANi hybrid nanofiller with an amphiphilic dispersing agent. The goal of the paper is not to present a comprehensive model of this phenomenon; we present some experimental results which may be related to polymer-filler interactions. These details are a part of this complicated phenomenon.

  6. Fabrication and Characterization of SMA Hybrid Composites

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.; Lach, Cynthia L.; Cano, Robert J.

    2001-01-01

    Results from an effort to fabrication shape memory alloy hybrid composite (SMAHC) test specimens and characterize the material system are presented in this study. The SMAHC specimens are conventional composite structures with an embedded SMA constituent. The fabrication and characterization work was undertaken to better understand the mechanics of the material system, address fabrication issues cited in the literature, and provide specimens for experimental validation of a recently developed thermomechanical model for SMAHC structures. Processes and hardware developed for fabrication of the SMAHC specimens are described. Fabrication of a SMA14C laminate with quasi-isotropic lamination and ribbon-type Nitinol actuators embedded in the 0' layers is presented. Beam specimens are machined from the laminate and are the focus of recent work, but the processes and hardware are readily extensible to more practical structures. Results of thermomechanical property testing on the composite matrix and Nitinol ribbon are presented. Test results from the Nitinol include stress-strain behavior, modulus versus temperature. and constrained recovery stress versus temperature and thermal cycle. Complex thermomechanical behaviors of the Nitinol and composite matrix are demonstrated, which have significant implications for modeling of SMAHC structures.

  7. Boron/aluminum graphite/resin advanced fiber composite hybrids

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sullivan, T. L.

    1975-01-01

    Fabrication feasibility and potential of an adhesively bonded metal and resin matrix fiber-composite hybrid are determined as an advanced material for aerospace and other structural applications. The results show that using this hybrid concept makes possible a composite design which, when compared with nonhybrid composites, has greater transverse strength, transverse stiffness, and impact resistance with only a small penalty on density and longitudinal properties. The results also show that laminate theory is suitable for predicting the structural response of such hybrids. The sequence of fracture modes indicates that these types of hybrids can be readily designed to meet fail-safe requirements.

  8. Ultra-high modulus organic fiber hybrid composites

    NASA Technical Reports Server (NTRS)

    Champion, A. R.

    1981-01-01

    An experimental organic fiber, designated Fiber D, was characterized, and its performance as a reinforcement for composites was investigated. The fiber has a modulus of 172 GPa, tensile strength of 3.14 GPa, and density of 1.46 gm/cu cm. Unidirectional Fiber D/epoxy laminates containing 60 percent fiber by volume were evaluated in flexure, shear, and compression, at room temperature and 121 C in both the as fabricated condition and after humidity aging for 14 days at 95 percent RH and 82 C. A modulus of 94.1 GPa, flexure strength of 700 MPa, shear strength of 54 MPa, and compressive strength of 232 MPa were observed at room temperature. The as-fabricated composites at elevated temperature and humidity aged material at room temperature had properties 1 to 20 percent below these values. Combined humidity aging plus evaluated temperature testing resulted in even lower mechanical properties. Hybrid composite laminates of Fiber D with Fiber FP alumina or Thornel 300 graphite fiber were also evaluated and significant increases in modulus, flexure, and compressive strengths were observed.

  9. Tensile failure of hybrid composites: measuring, predicting and understanding

    NASA Astrophysics Data System (ADS)

    Swolfs, Yentl; Verpoest, Ignaas; Gorbatikh, Larissa

    2016-07-01

    Fibre-hybrid composites are attracting an ever-increasing interest from academia and industry. It is therefore vital to develop a solid understanding of their basic mechanical properties. Measuring and predicting the tensile failure of hybrid composites however remains a challenging task. This paper describes how failure develops in unidirectional (UD) hybrid composites, and how this can be predicted using fibre break models. It also provides recommendations for experimental measurements of the hybrid effect, which is a synergetic increase of the failure strain of low elongation fibres when hybridised with higher elongation fibres. Finally, limitations of our understanding of the tensile failure of hybrid composites are discussed and recommendations for future research are proposed.

  10. Effect of Hybridization on Stiffness Properties of Woven Textile Composites

    NASA Astrophysics Data System (ADS)

    Bejan, Liliana; Taranu, Nicolae; Sîrbu, Adriana

    2013-04-01

    The present study focuses on stiffness properties of woven textile reinforced polymeric composites with respect to hybridization, and geometry of reinforcement. The analyzed composites represent combinations of different fibre materials (E-glass, Kevlar 49, carbon HM) in a predetermined fabric geometry (a plane weave embedded in thermosetting polymeric resin) serving controlled properties and required performance. The effects of hybridization on the stiffness properties of woven textile composites have been studied with respect to the fibres materials, the unbalancing degree of fabrics, and the variation of compactness and undulation of yarns. Some undesirable effects in fabric geometry can be overcome by the combined effects of hybridization and compactness.

  11. Method of producing a hybrid matrix fiber composite

    DOEpatents

    Deteresa, Steven J.; Lyon, Richard E.; Groves, Scott E.

    2006-03-28

    Hybrid matrix fiber composites having enhanced compressive performance as well as enhanced stiffness, toughness and durability suitable for compression-critical applications. The methods for producing the fiber composites using matrix hybridization. The hybrid matrix fiber composites comprised of two chemically or physically bonded matrix materials, whereas the first matrix materials are used to impregnate multi-filament fibers formed into ribbons and the second matrix material is placed around and between the fiber ribbons that are impregnated with the first matrix material and both matrix materials are cured and solidified.

  12. Environmental effects on the hybrid glass fiber/carbon fiber composites

    NASA Astrophysics Data System (ADS)

    Tsai, Yun-I.

    2009-12-01

    Fiber reinforced polymer composites (FRPCs) have been widely used to replace conventional metals due to the high specific strength, fatigue resistance, and light weight. In the power distribution industry, an advanced composites rod has been developed to replace conventional steel cable as the load-bearing core of overhead conductors. Such conductors, called aluminum conductor composite core (ACCC) significantly increases the transmitting efficiency of existing power grid system without extensive rebuilding expenses, while meeting future demand for electricity. In general, the service life of such overhead conductors is required to be at least 30 years. Therefore, the long-term endurance of the composite core in various environments must be well-understood. Accelerated aging by hygrothermal exposure was conducted to determine the effect of moisture on the glass fiber (GF)/carbon fiber (CF) hybrid composites. The influence of water immersion and humid air exposure on mechanical properties is investigated. Results indicated that immersion in water is the most severe environment for such hybrid GF/CF composites, and results in greater saturation and degradation of properties. When immersed directly in water, the hybrid GF/CF composites exhibit a moisture uptake behavior that is more complex than composite materials reinforced with only one type of fiber. The unusual diffusion behavior is attributed to a higher packing density of fibers at the annular GF/CF interface, which acts as a temporary moisture barrier. Moisture uptake leads to the mechanical and thermal degradation of such hybrid GF/CF composites. Findings presented here indicate that the degradation is a function of exposure temperature, time, and moisture uptake level. Results also indicate that such hybrid GF/CF composites recover short beam shear (SBS) strength and glass transition temperature (Tg) values comparable to pre-aged samples after removal of the absorbed moisture. In the hygrothermal environment

  13. Evaluation of tensile strength of hybrid fiber (jute/gongura) reinforced hybrid polymer matrix composites

    NASA Astrophysics Data System (ADS)

    Venkatachalam, G.; Gautham Shankar, A.; Vijay, Kumar V.; Chandan, Byral R.; Prabaharan, G. P.; Raghav, Dasarath

    2015-07-01

    The polymer matrix composites attract many industrial applications due to its light weight, less cost and easy for manufacturing. In this paper, an attempt is made to prepare and study of the tensile strength of hybrid (two natural) fibers reinforced hybrid (Natural + Synthetic) polymer matrix composites. The samples were prepared with hybrid reinforcement consists of two different fibers such as jute and Gongura and hybrid polymer consists of polyester and cashew nut shell resins. The hybrid composites tensile strength is evaluated to study the influence of various fiber parameters on mechanical strength. The parameters considered here are the duration of fiber treatment, the concentration of alkali in fiber treatment and nature of fiber content in the composites.

  14. Impact resistance of hybrid composite fan blade materials

    NASA Technical Reports Server (NTRS)

    Friedrich, L. A.

    1974-01-01

    Improved resistance to foreign object damage was demonstrated for hybrid composite simulated blade specimens. Transply metallic reinforcement offered additional improvement in resistance to gelatin projectile impacts. Metallic leading edge protection permitted equivalent-to-titanium performance of the hybrid composite simulated blade specimen for impacts with 1.27 cm and 2.54 cm (0.50 and 1.00 inch) diameter gelatin spheres.

  15. Stabilization of composition fluctuations in mixed membranes by hybrid lipids

    NASA Astrophysics Data System (ADS)

    Safran, Samuel; Palmieri, Benoit

    2013-03-01

    A ternary mixture model is proposed to describe composition fluctuations in mixed membranes composed of saturated, unsaturated and hybrid lipids. The asymmetric hybrid lipid has one saturated and one unsaturated hydrocarbon chain and it can reduce the packing incompatibility between saturated and unsaturated lipids. A methodology to recast the free-energy of the lattice in terms of a continuous isotropic field theory is proposed and used to analyze composition fluctuations above the critical temperature. The effect of hybrid lipids on fluctuations domains rich in saturated/unsaturated lipids is predicted. The correlation length of such fluctuations decreases significantly with increasing amounts of hybrids even if the temperature is maintained close to the critical temperature. This provides an upper bound for the domain sizes expected in rafts stabilized by hybrids, above the critical temperature. When the hybrid composition of the membrane is increased further, a crossover value is found above which ``stripe-like'' fluctuations are observed. The wavelength of these fluctuations decreases with increasing hybrid fraction and tends toward a molecular size in a membrane that contains only hybrids.

  16. Boron/aluminum-graphite/resin advanced fiber composite hybrids

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.; Sullivan, T. L.

    1974-01-01

    An investigation was conducted to determine the fabrication feasibility and to assess the potential of adhesively-bonded metal and resin matrix fiber composite hybrids as an advanced material, for aerospace and other structural applications. The results of fabrication studies and of evaluation of physical and mechanical properties show that using this hybrid concept it is possible to design a composite which, when compared to nonhybrid composites, has improved transverse strength, transverse stiffness, and impact resistance with only a small penalty on density and longitudinal properties. The results also show that laminate theory is suitable for perdicting the structural response of such hybrids. The sequence of fracture modes indicates that these types of hybrids can be readily designed to meet fail-safe requirements.

  17. Experimental determination of material constants of a hybrid composite laminate

    SciTech Connect

    Ihekweazu, S.N.; Lari, S.B.; Unanwa, C.O.

    1999-07-01

    This paper discusses the results of the experimental study that was conducted in order to determine the material properties of a hybrid composite laminate made from Fiberite material MXM-7714/120 (a fabric prepreg consisting of woven Kevlar{reg_sign} 49 reinforcement impregnated with Fiberite 250 F (121 C) curing 7714 epoxy resin) and HYE-2448AIE (a 250 F (121 C) curing epoxy resin impregnated unidirectional graphite tape). First, each of the materials that comprise the hybrid laminate was fabricated separately according to ASTM-D-3039 specification in order to determine their material properties. The materials were then hybridized and the properties were determined. Data from this experiment reveal that a new class of material that can meet desired specifications can be created through hybridization. The data also revealed that the properties of the materials bonded together as a hybrid complement the properties of the constituent members of the hybrid.

  18. Multifunctional Hybrid Carbon Nanotube/Carbon Fiber Polymer Composites

    NASA Technical Reports Server (NTRS)

    Kang, Jin Ho; Cano, Roberto J.; Ratcliffe, James G.; Luong, Hoa; Grimsley, Brian W.; Siochi, Emilie J.

    2016-01-01

    For aircraft primary structures, carbon fiber reinforced polymer (CFRP) composites possess many advantages over conventional aluminum alloys due to their light weight, higher strengthand stiffness-to-weight ratio, and low life-cycle maintenance costs. However, the relatively low electrical and thermal conductivities of CFRP composites fail to provide structural safety in certain operational conditions such as lightning strikes. Despite several attempts to solve these issues with the addition of carbon nanotubes (CNT) into polymer matrices, and/or by interleaving CNT sheets between conventional carbon fiber (CF) composite layers, there are still interfacial problems that exist between CNTs (or CF) and the resin. In this study, hybrid CNT/CF polymer composites were fabricated by interleaving layers of CNT sheets with Hexcel® IM7/8852 prepreg. Resin concentrations from 1 wt% to 50 wt% were used to infuse the CNT sheets prior to composite fabrication. The interlaminar properties of the resulting hybrid composites were characterized by mode I and II fracture toughness testing (double cantilever beam and end-notched flexure test). Fractographical analysis was performed to study the effect of resin concentration. In addition, multi-directional physical properties like thermal conductivity of the orthotropic hybrid polymer composite were evaluated. Interleaving CNT sheets significantly improved the in-plane (axial and perpendicular direction of CF alignment) thermal conductivity of the hybrid composite laminates by 50 - 400%.

  19. Analysis/design of strip reinforced random composites (strip hybrids)

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1978-01-01

    Advanced analysis methods and composite mechanics were applied to a strip-reinforced random composite square panel with fixed ends to illustrate the use of these methods for the a priori assessment of the composite panel when subjected to complex loading conditions. The panel was assumed to be of E-glass random composite. The strips were assumed to be of three advanced unidirectional composites to cover a range of low, intermediate, and high modulus stiffness. The panels were assumed to be subjected to complex loadings to assess their adequacy as load-carrying members in auto body, aircraft engine nacelle and windmill blade applications. The results show that strip hybrid panels can be several times more structurally efficient than the random composite base materials. Some of the results are presented in graphical form and procedures are described for use of these graphs as guides for preliminary design of strip hybrids.

  20. Analysis/design of strip reinforced random composites /strip hybrids/

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1978-01-01

    Results are described which were obtained by applying advanced analysis methods and composite mechanics to a strip-reinforced random composite square panel with fixed ends. This was done in order to illustrate the use of these methods for the apriori assessment of the composite panel when subjected to complex loading conditions. The panel was assumed to be of E-Glass/Random Composite. The strips were assumed to be of three advanced unidirectional composites to cover a range of low, intermediate, and high modulus stiffness. The panels were assumed to be subjected to complex loadings to assess their adequacy as load-carrying members in auto body, aircraft engine nacelle, and windmill blade applications. The results show that strip hybrid panels can be several times more structurally efficient than the random composite base materials. Some of the results are presented in graphical form and procedures are described for use of these graphs as guides for preliminary design of strip hybrids.

  1. Probing Compositional Variation within Hybrid Nanostructures

    SciTech Connect

    Yuhas, Benjamin D.; Habas, Susan E.; Fakra, Sirine C.; Mokari, Taleb

    2010-06-22

    We present a detailed analysis of the structural and magnetic properties of solution-grown PtCo-CdS hybrid structures in comparison to similar free-standing PtCo alloy nanoparticles. X-ray absorption spectroscopy is utilized as a sensitive probe for identifying subtle differences in the structure of the hybrid materials. We found that the growth of bimetallic tips on a CdS nanorod substrate leads to a more complex nanoparticle structure composed of a PtCo alloy core and thin CoO shell. The core-shell architecture is an unexpected consequence of the different nanoparticle growth mechanism on the nanorod tip, as compared to free growth in solution. Magnetic measurements indicate that the PtCo-CdS hybrid structures are superparamagnetic despite the presence of a CoO shell. The use of X-ray spectroscopic techniques to detect minute differences in atomic structure and bonding in complex nanosystems makes it possible to better understand and predict catalytic or magnetic properties for nanoscale bimetallic hybrid materials.

  2. Innovative Technologies to Manufacture Hybrid Metal Foam/Composite Components

    SciTech Connect

    Carrino, L.; Durante, M.; Franchitti, S.; Sorrentino, L.; Tersigni, L.

    2011-01-17

    The aim of this paper is to verify the technological feasibility to realize hybrid metal-foam/composite component and the mechanical performances of the final structure. The hybrid component is composed by a cylindrical core in aluminum foam, the most used between those commercially available, and an outer layer in epoxy/S2-glass, manufactured by filament winding technology.A set of experimental tests have been carried out, to the aim to estimate the improvement of the hybrid component characteristics, compared to the sum of the single components (metal foam cylinder and epoxy/S2-glass tube).

  3. Hybridization induced transparency in composites of metamaterials and atomic media.

    PubMed

    Weis, Peter; Garcia-Pomar, Juan Luis; Beigang, René; Rahm, Marco

    2011-11-01

    We report hybridization induced transparency (HIT) in a composite medium consisting of a metamaterial and a dielectric. We develop an analytic model that explains HIT by coherent coupling between the hybridized local fields of the metamaterial and the dielectric or an atomic system in general. In a proof-of-principle experiment, we evidence HIT in a split ring resonator metamaterial that is coupled to α-lactose monohydrate. Both, the analytic model and numerical calculations confirm and explain the experimental observations. HIT can be considered as a hybrid analogue to electromagnetically induced transparency (EIT) and plasmon-induced transparency (PIT). PMID:22109237

  4. Topologically ordered magnesium-biopolymer hybrid composite structures.

    PubMed

    Oosterbeek, Reece N; Seal, Christopher K; Staiger, Mark P; Hyland, Margaret M

    2015-01-01

    Magnesium and its alloys are intriguing as possible biodegradable biomaterials due to their unique combination of biodegradability and high specific mechanical properties. However, uncontrolled biodegradation of magnesium during implantation remains a major challenge in spite of the use of alloying and protective coatings. In this study, a hybrid composite structure of magnesium metal and a biopolymer was fabricated as an alternative approach to control the corrosion rate of magnesium. A multistep process that combines metal foam production and injection molding was developed to create a hybrid composite structure that is topologically ordered in all three dimensions. Preliminary investigations of the mechanical properties and corrosion behavior exhibited by the hybrid Mg-polymer composite structures suggest a new potential approach to the development of Mg-based biomedical devices.

  5. Fingerprint composition and aging: A literature review.

    PubMed

    Cadd, Samuel; Islam, Meez; Manson, Peter; Bleay, Stephen

    2015-07-01

    Fingerprints have a key role in criminal investigations and are the most commonly used form of evidence worldwide. Significant gaps remain however, in the understanding of fingerprint chemistry, including enhancement reaction mechanisms and the effect of environmental variables and time on composition. Determining the age of a fingerprint is also a relatively unexplored area. A successful method, with reliable and quantitative estimates, would have numerous advantages. Previous unreliable methods have predominantly focused on enhancement success based on physical and chemical changes. This review explores variations in composition due to donor characteristics and environmental variables, and identifies gaps for further research. We also present a qualitative and quantitative summary of the effect of time on composition. Kinetics are presented where known, with summary schematics for reaction mechanisms. Previous studies exploring methods for determining the age of a fingerprint are also discussed, including their advantages and disadvantages. Lastly we propose a potentially more accurate and reliable methodology for determining fingerprint age based on quantitative kinetic changes to the composition of a fingerprint over time.

  6. Micromechanics of intraply hybrid composites: Elastic and thermal properties

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1979-01-01

    Composite micromechanics are used to derive equations for predicting the elastic and thermal properties of unidirectional intraply hybrid composites. The results predicted using these equations are compared with those predicted using approximate equations based on the rule of mixtures, linear laminate theory, finite element analysis and limited experimental data. The comparisons for three different intraply hybrids indicate that all four methods predict approximately the same elastic properties and are in good agreement with measured data. The micromechanics equations and linear laminate theory predict about the same values for thermal expansion coefficients. The micromechanics equations predict through-the-thickness properties which are in good agreement with the finite element results.

  7. Physical aging in graphite epoxy composites

    NASA Technical Reports Server (NTRS)

    Kong, E. S. W.

    1981-01-01

    The matrix dominated mechanical behavior of a graphite epoxy composite was found to be affected by sub Tg annealing. Postcured + or - 45 deg 4S specimens of Thornel 300 graphite/Narmco 5208 epoxy were quenched from above Tg and given a sub Tg annealing at 140 C for times up to 10 to the 5th power min. The ultimate tensile strength, strain to break, and toughness of the composite material were found to decrease as functions of sub Tg annealing time. No weight loss was observed during the sub Tg annealing. The time dependent change in mechanical behavior is explained on the basis of free volume changes that are related to the physical aging of the nonequilibrium glassy network epoxy. The results imply possible changes in composite properties with service time.

  8. Direct oven-tempered hybrid composite-resin laminate veneers.

    PubMed

    Birnbaum, N S

    1992-01-01

    The difficulty in achieving optimal aesthetics of the single-tooth indirect laminate veneer has prompted the author to develop a direct technique for fabricating oven-tempered hybrid composite resin veneers. These restorations exhibit excellent physical properties, marginal integrity, and aesthetics.

  9. Analysis of high velocity impact on hybrid composite fan blades

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1979-01-01

    This paper describes recent developments in the analysis of high velocity impact of composite blades using a computerized capability which consists of coupling a composites mechanics code with the direct-time integration features of NASTRAN. The application of the capability to determine the linear dynamic response of an intraply hybrid composite aircraft engine fan blade is described in detail. The predicted results agree with measured data. The results also show that the impact stresses reach sufficiently high magnitudes to cause failures in the impact region at early times of the impact event.

  10. Analysis of high velocity impact on hybrid composite fan blades

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1979-01-01

    Recent developments in the analysis of high velocity impact of composite blades are described, using a computerized capability which consists of coupling a composites mechanics code with the direct-time integration features of NASTRAN. The application of the capability to determine the linear dynamic response of an interply hybrid composite aircraft engine fan blade is described in detail. The results also show that the impact stresses reach sufficiently high magnitudes to cause failures in the impact region at early times of the impact event.

  11. Novel hybrid coatings with controlled wettability by composite nanoparticle aggregation

    NASA Astrophysics Data System (ADS)

    Hritcu, Doina; Dodi, Gianina; Iordache, Mirabela L.; Draganescu, Dan; Sava, Elena; Popa, Marcel I.

    2016-11-01

    The aim of this study is to evaluate novel hybrid materials as potential candidates for producing coatings with hierarchical roughness and controlled wetting behaviour. Magnetite (Fe3O4) nanoparticles obtained by co-precipitation were embedded in matrices synthesized by radical graft co-polymerization of butyl acrylate (BA), butyl methacrylate (BMA), hexyl acrylate (HA) or styrene (ST) with ethylene glycol di-methacrylate (EGDMA) onto previously modified chitosan bearing surface vinyl groups. The resulting composite particles were characterized regarding their average size, composition and magnetic properties. Hybrid thin films containing suspension of composite particles in ethanol and pre-hydrolysed hexadecyltrimethoxysilane (HDTS) as a coupling/crosslinking agent were deposited by spin coating or spraying. The films were cured by heating and subsequently characterized regarding their morphology (scanning electron microscopy), contact angle with water and adhesion to substrate (scratch test). The structure-property relationship is discussed.

  12. Accelerated aging of polymer composite bridge materials

    NASA Astrophysics Data System (ADS)

    Carlson, Nancy M.; Blackwood, Larry G.; Torres, Lucinda L.; Rodriguez, Julio G.; Yoder, Timothy S.

    1999-05-01

    Accelerated aging research on samples of composite materials and candidate UV protective coatings is determining the effects of six environmental factors on material durability. Candidate fastener materials are being evaluated to determine corrosion rates and crevice corrosion effects at load-bearing joints. This work supports field testing of a 30-ft long, 18-ft wide polymer matrix composite (PMC) bridge at the Idaho National Engineering and Environmental Laboratory. Durability results and sensor data form test with live loads provide information required for determining the cost/benefit measures to use in life-cycle planning, determining a maintenance strategy, establishing applicable inspection techniques, and establishing guidelines, standards and acceptance criteria for PMC bridges for use in the transportation infrastructure.

  13. Accelerated Aging of Polymer Composite Bridge Materials

    SciTech Connect

    Carlson, Nancy Margaret; Blackwood, Larry Gene; Torres, Lucinda Laine; Rodriguez, Julio Gallardo; Yoder, Timothy Scott

    1999-03-01

    Accelerated aging research on samples of composite material and candidate ultraviolet (UV) protective coatings is determining the effects of six environmental factors on material durability. Candidate fastener materials are being evaluated to determine corrosion rates and crevice corrosion effects at load-bearing joints. This work supports field testing of a 30-ft long, 18-ft wide polymer matrix composite (PMC) bridge at the Idaho National Engineering and Environmental Laboratory (INEEL). Durability results and sensor data from tests with live loads provide information required for determining the cost/benefit measures to use in life-cycle planning, determining a maintenance strategy, establishing applicable inspection techniques, and establishing guidelines, standards, and acceptance criteria for PMC bridges for use in the transportation infrastructure.

  14. Physical aging in graphite/epoxy composites

    NASA Technical Reports Server (NTRS)

    Kong, E. S. W.

    1983-01-01

    Sub-Tg annealing has been found to affect the properties of graphite/epoxy composites. The network epoxy studied was based on the chemistry of tetraglycidyl 4,4'-diamino-diphenyl methane (TGDDM) crosslinked by 4,4'-diamino-diphenyl sulfone (DDS). Differential scanning calorimetry, thermal mechanical analysis, and solid-state cross-polarized magic-angle-spinning nuclear magnetic resonance spectroscopy have been utilized in order to characterize this process of recovery towards thermodynamic equilibrium. The volume and enthalpy recovery as well as the 'thermoreversibility' aspects of the physical aging are discussed. This nonequilibrium and time-dependent behavior of network epoxies are considered in view of the increasingly wide applications of TGDDM-DDS epoxies as matrix materials of structural composites in the aerospace industry.

  15. Structural/material similitude concepts for hybrid composite tubes

    SciTech Connect

    Liggett, G.M.

    1995-12-31

    Composites are excellent candidates for replacing steel in deepwater offshore structural components such as risers, tendons, and tethers. They offer weight savings as well as unique tailorability of the design. Hybrid composites, where multiple fiber types embedded in a single matrix, offer even greater tailorability over traditionally reinforced composites. The design of hybrid composite structures, however, is complicated by the number of design variables and the interaction of the constituents of the composite system. Since it is desirable to experimentally test the design and it is not practical to test a full scale riser model, the structural/material similitude concept is applied to create a small scale model with a similar (close to identical) structural response. In this similitude approach, the coefficients of the governing differential equation for a system and a model of the system are compared to develop scaling laws. For composites, these scaling laws depend not just on geometry, but also on constituent properties, and the location and orientation of the constituents in the system. Herein, the concept of similitude is applied to the problem of a composite riser for offshore applications. Several experimental models are designed to match realistic prototype riser service conditions. Variations in the geometric properties and the layup were also analyzed. These models were highly sensitive to changes in inner diameter and the length of prototype tube they each represented, but were less sensitive to changes in angle of the layup.

  16. Development of LaRC 160/NR150B2 polyimide graphite hybrid composites. [for shuttle applications

    NASA Technical Reports Server (NTRS)

    Maximovich, M. G.; Bergren, O.; Lockerby, S.

    1980-01-01

    A method for co-curing NR150B2 and LaRC 160 prepregs into hybrid composites was developed. The processing characteristics and the properties of the hybrid composites were compared with those of laminates fabricated from the individual component prepregs. Resin forms were selected and optimized and a new NR150 formulation was investigated. The new formulation greatly facilitated the processing and the performance of this system. Quality control techniques were evaluated and developed, high quality laminates were fabricated from both individual resin systems, and hybrid laminates were successfully co-cured. Optimum hybrid forms were investigated and several novel approaches were explored. An optimum hybrid system was developed that utilizes a LaRC curing schedule but shows no degradation of mechanical properties after aging 500 hr in air at 260 C.

  17. Water absorption behavior and residual strength assessment of glass/epoxy and glass-carbon/epoxy hybrid composite

    NASA Astrophysics Data System (ADS)

    Mohanty, S. C.; Singh, B. P.; Mahato, K. K.; Rathore, D. K.; Prusty, R. K.; Ray, B. C.

    2016-02-01

    Present investigation is aimed to study the water absorption behaviour and evaluation of residual strength of glass fibre/epoxy (GE) and alternate plies of glass- carbon/epoxy (GCE) hybrid composite. Both the composite systems were exposed to water at 70°C. Specimens were weighed after certain time periods to study the water uptake kinetic. Flexural tests were conducted after 4, 100 and 450 hours of ageing to evaluate the effect of hot water ageing on the mechanical properties of these potential materials. The water uptake kinetic was found to follow Fickian diffusion kinetic for GE as well as GCE hybrid composite but the rate of diffusion was higher for GE composite over GCE composite. The water content was also higher in GE composite over GCE composite after 450 hours of ageing. Significant decrement in flexural strength was observed with the increase in ageing time. Presence of water in the composite also imparted significant embrittlement to the matrix as reflected in the decrease in strain at peak for both the composite systems.

  18. On the development of an intrinsic hybrid composite

    NASA Astrophysics Data System (ADS)

    Kießling, R.; Ihlemann, J.; Riemer, M.; Drossel, W.-G.; Scharf, I.; Lampke, T.; Sharafiev, S.; Pouya, M.; F-X Wagner, M.

    2016-03-01

    Hybrid parts, which combine low weight with high strength, are moving into the focus of the automotive industry, due to their high potential for usage in the field of crash-relevant structures. In this contribution, the development of an intrinsic hybrid composite is presented, with a focus on the manufacturing process, complex simulations of the material behaviour and material testing. The hybrid composite is made up of a continuous fibre- reinforced plastic (FRP), in which a metallic insert is integrated. The mechanical behaviour of the individual components is characterised. For material modelling, an approach is pointed out that enables modelling at large strains by directly connected rheological elements. The connection between the FRP and the metallic insert is realised by a combination of form fit and adhesive bonds. On the one hand, adhesive bonds are generated within a sol gel process. On the other hand, local form elements of the metallic insert are pressed into the FRP. We show how these form elements are generated during the macroscopic forming process. In addition, the applied sol gel process is explained. Finally, we consider design concepts for a specimen type for high strain testing of the resulting interfaces.

  19. Low and high velocity impact response of thick hybrid composites

    NASA Technical Reports Server (NTRS)

    Hiel, Clement; Ishai, Ori

    1993-01-01

    The effects of low and high velocity impact on thick hybrid composites (THC's) were experimentally compared. Test Beams consisted of CFRP skins which were bonded onto an interleaved syntactic foam core and cured at 177 C (350 F). The impactor tip for both cases was a 16 mm (0.625 inch) steel hemisphere. In spite of the order of magnitude difference in velocity ranges and impactor weights, similar relationships between impact energy, damage size, and residual strength were found. The dependence of the skin compressive strength on damage size agree well with analytical open hole models for composite laminates and may enable the prediction of ultimate performance for the damaged composite, based on visual inspection.

  20. Hybrid Composites for LH2 Fuel Tank Structure

    NASA Technical Reports Server (NTRS)

    Grimsley, Brian W.; Cano, Roberto J.; Johnston, Norman J.; Loos, Alfred C.; McMahon, William M.

    2001-01-01

    The application of lightweight carbon fiber reinforced plastics (CFRP) as structure for cryogenic fuel tanks is critical to the success of the next generation of Reusable Launch Vehicles (RLV). The recent failure of the X-33 composite fuel tank occurred in part due to microcracking of the polymer matrix, which allowed cryogen to permeate through the inner skin to the honeycomb core. As part of an approach to solve these problems, NASA Langley Research Center (LaRC) and Marshall Space Flight Center (MSFC) are working to develop and investigate polymer films that will act as a barrier to the permeation of LH2 through the composite laminate. In this study two commercially available films and eleven novel LaRC films were tested in an existing cryogenics laboratory at MSFC to determine the permeance of argon at room temperature. Several of these films were introduced as a layer in the composite to form an interleaved, or hybrid, composite to determine the effects on permeability. In addition, the effects of the interleaved layer thickness, number, and location on the mechanical properties of the composite laminate were investigated. In this initial screening process, several of the films were found to exhibit lower permeability to argon than the composite panels tested.

  1. Chemical Composition of Fresh and Aged Biochars

    NASA Astrophysics Data System (ADS)

    Cooper, W. T.; Hamdan, R.; Mukherjee, A.; Zimmerman, A. R.

    2014-12-01

    It is possible to manipulate the chemical and physical properties of pyrogenic organic matter ('black carbon' or 'biochar') during its production and tailor its composition for intended environmental management applications. In this study biochars made from grass (Tripsacum floridanum), oak (Quercus lobata), and pine (Pinus taeda) at 250 ºC in air and 400 and 650 ºC under N2 were characterized by solid state 13C-NMR spectroscopy and desorption atmospheric pressure photoionization mass spectrometry. Among the biochars produced, those originating from pine showed distinct characteristics, with greater amounts of oxygenated aromatic clusters after low temperature combustion and more condensed aromatic clusters after higher temperature pyrolysis. Although a mixture of small and large aromatic clusters occurred across the temperature profile, cluster size increased and functionality decreased with increasing combustion temperature (Figure 1). At medium and high temperatures, aromatic clusters of up to 60- carbon aromatic rings inter-connected with small chains dominated the biochars examined. These structures are intermediate in size between the linearly condensed structures and the predominantly condensed aromatic clusters proposed in earlier studies. Field aging of the pure biochars for 15 months decreased the total acid functional group content as determined by Boehm titration, but solid-state 13C-NMR analyses suggested the creation and transformation of a range of functional groups via leaching, oxidation, and addition of microbially-produced organic matter. Similar trends were observed when the biochars were mixed with soils, suggesting that the same biochar aging processes occurred in the soil environment. These findings demonstrate that biochar transformations occur over time through a multitude of processes that are both biochar and soil type-dependent.

  2. Aging and quality assurance of Kevlar 49-epoxy composites

    SciTech Connect

    Morgan, R.J.

    1981-05-15

    The aging of Kevlar 49-epoxy composites under the service environment conditions expected by ESA will be insignificant to the best of our knowledge at this time. However, certain precautions in materials acceptance criteria and composite fabrication should be followed.

  3. MoSi2-Base Hybrid Composites from Aeroengine Applications

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G.

    2000-01-01

    Addition of about 30 to 50 vol % of Si3N4 particulate to MoSi2 improved low temperature accelerated oxidation resistance by forming a Si2ON2 protective scale and thereby eliminated catastrophic 'pest failure'. The Si3N4 addition also improved the high temperature creep strength by nearly five orders of magnitude, doubled the room temperature toughness, and significantly lowered the CTE of the MoSi2 which eliminated matrix cracking in SCS-6 reinforced composites even after thermal cycling. The SCS-6 fiber reinforcement improved the room temperature fracture toughness by seven times and impact resistance by five times. The composite exhibited this excellent strength and toughness improvement up to 1673 K. More recently, tape casting was adopted as the preferred processing of MoSi2-base composites due to improved fiber spacing, ability to use small diameter fibers, and for lower cost. Good strength and toughness values were also obtained with fine diameter Hi-Nicalon tow fibers. These hybrid composites remain competitive with ceramic matrix composites as a replacement for Ni-base superalloys in aircraft engine applications.

  4. SMA Hybrid Composites for Dynamic Response Abatement Applications

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.

    2000-01-01

    A recently developed constitutive model and a finite element formulation for predicting the thermomechanical response of Shape Memory Alloy (SMA) hybrid composite (SMAHC) structures is briefly described. Attention is focused on constrained recovery behavior in this study, but the constitutive formulation is also capable of modeling restrained or free recovery. Numerical results are shown for glass/epoxy panel specimens with embedded Nitinol actuators subjected to thermal and acoustic loads. Control of thermal buckling, random response, sonic fatigue, and transmission loss are demonstrated and compared to conventional approaches including addition of conventional composite layers and a constrained layer damping treatment. Embedded SMA actuators are shown to be significantly more effective in dynamic response abatement applications than the conventional approaches and are attractive for combination with other passive and/or active approaches.

  5. Flexural analysis of palm fiber reinforced hybrid polymer matrix composite

    NASA Astrophysics Data System (ADS)

    Venkatachalam, G.; Gautham Shankar, A.; Raghav, Dasarath; Santhosh Kiran, R.; Mahesh, Bhargav; Kumar, Krishna

    2015-07-01

    Uncertainty in availability of fossil fuels in the future and global warming increased the need for more environment friendly materials. In this work, an attempt is made to fabricate a hybrid polymer matrix composite. The blend is a mixture of General Purpose Resin and Cashew Nut Shell Liquid, a natural resin extracted from cashew plant. Palm fiber, which has high strength, is used as reinforcement material. The fiber is treated with alkali (NaOH) solution to increase its strength and adhesiveness. Parametric study of flexure strength is carried out by varying alkali concentration, duration of alkali treatment and fiber volume. Taguchi L9 Orthogonal array is followed in the design of experiments procedure for simplification. With the help of ANOVA technique, regression equations are obtained which gives the level of influence of each parameter on the flexure strength of the composite.

  6. Nonlinear Thermoelastic Model for SMAs and SMA Hybrid Composites

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.

    2004-01-01

    A constitutive mathematical model has been developed that predicts the nonlinear thermomechanical behaviors of shape-memory-alloys (SMAs) and of shape-memory-alloy hybrid composite (SMAHC) structures, which are composite-material structures that contain embedded SMA actuators. SMAHC structures have been investigated for their potential utility in a variety of applications in which there are requirements for static or dynamic control of the shapes of structures, control of the thermoelastic responses of structures, or control of noise and vibrations. The present model overcomes deficiencies of prior, overly simplistic or qualitative models that have proven ineffective or intractable for engineering of SMAHC structures. The model is sophisticated enough to capture the essential features of the mechanics of SMAHC structures yet simple enough to accommodate input from fundamental engineering measurements and is in a form that is amenable to implementation in general-purpose structural analysis environments.

  7. Buckling induced delamination of graphene composites through hybrid molecular modeling

    NASA Astrophysics Data System (ADS)

    Cranford, Steven W.

    2013-01-01

    The efficiency of graphene-based composites relies on mechanical stability and cooperativity, whereby separation of layers (i.e., delamination) can severely hinder performance. Here we study buckling induced delamination of mono- and bilayer graphene-based composites, utilizing a hybrid full atomistic and coarse-grained molecular dynamics approach. The coarse-grain model allows exploration of an idealized model material to facilitate parametric variation beyond any particular molecular structure. Through theoretical and simulation analyses, we show a critical delamination condition, where ΔD∝kL4, where ΔD is the change in bending stiffness (eV), k the stiffness of adhesion (eV/Å4), and L the length of the adhered section (Å).

  8. Experimental Validation of a Thermoelastic Model for SMA Hybrid Composites

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.

    2001-01-01

    This study presents results from experimental validation of a recently developed model for predicting the thermomechanical behavior of shape memory alloy hybrid composite (SMAHC) structures, composite structures with an embedded SMA constituent. The model captures the material nonlinearity of the material system with temperature and is capable of modeling constrained, restrained, or free recovery behavior from experimental measurement of fundamental engineering properties. A brief description of the model and analysis procedures is given, followed by an overview of a parallel effort to fabricate and characterize the material system of SMAHC specimens. Static and dynamic experimental configurations for the SMAHC specimens are described and experimental results for thermal post-buckling and random response are presented. Excellent agreement is achieved between the measured and predicted results, fully validating the theoretical model for constrained recovery behavior of SMAHC structures.

  9. MoSi2-Base Hybrid Composite Passed Engine Test

    NASA Technical Reports Server (NTRS)

    Keith, Theo G., Jr.; Hebsur, Mohan

    1998-01-01

    The intermetallics compound molybdenum disilicide (MoSi2) is an attractive high-temperature structural material for advanced engine applications. It has excellent oxidation resistance, a high melting point, relatively low density, and high thermal conductivity, and it is easily machined. Past research'at the NASA Lewis Research Center has resulted in the development of a hybrid composite consisting of a MoSi2 matrix reinforced with silicon nitride (Si3N4) Particulate and silicon carbide (SiC) fibers. This composite has demonstrated attractive strength, toughness, thermal fatigue, and oxidation resistance, including resistance to "pest" oxidation. These properties attracted the interest of the Office of Naval Research and Pratt & Whitney, and a joint NASA/Navy/Pratt & Whitney effort was developed to continue to mature the MoSi2 Composite technology. A turbine blade outer air seal, which was part of the Integrated High Performance Turbine Engine Technology (IHPTET) program, was chosen as a first component on which to focus. The first tasks of the materials development effort were to develop improved processing methods to reduce costs and to use fine-diameter fibers that enable the manufacturing of complex shapes. Tape-casting methods were developed to fully infiltrate the fine SiC fibers with matrix powders. The resulting composites were hot pressed to 100-percent density. Composites with cross-plied fiber architectures with 30 vol. % hi-nicalon SiC fibers and 30 vol. % nitride particles are now made routinely and demonstrate a good balance of properties. The next task entailed the measurement of a wide variety of mechanical properties to confirm the suitability of this composite in engines. In particular, participants in this effort demonstrated that composites made with Hi-Nicalon fibers had strength and toughness properties equal to or better than those of the composites made with the large-diameter fibers that had been used previously. Another critically

  10. SERS of semiconducting nanoparticles (TIO{sub 2} hybrid composites).

    SciTech Connect

    Rajh, T.; Musumeci, A.; Gosztola, D.; Schiller, T.; Dimitrijevic, N. M.; Mujica, V.; Martin, D.; Center for Nanoscale Materials

    2009-05-06

    Raman scattering of molecules adsorbed on the surface of TiO{sub 2} nanoparticles was investigated. We find strong enhancement of Raman scattering in hybrid composites that exhibit charge transfer absorption with TiO{sub 2} nanoparticles. An enhancement factor up to {approx}10{sup 3} was observed in the solutions containing TiO{sub 2} nanoparticles and biomolecules, including the important class of neurotransmitters such as dopamine and dopac (3,4-dihydroxy-phenylacetic acid). Only selected vibrations are enhanced, indicating molecular specificity due to distinct binding and orientation of the biomolecules coupled to the TiO{sub 2} surface. All enhanced modes are associated with the asymmetric vibrations of attached molecules that lower the symmetry of the charge transfer complex. The intensity and the energy of selected vibrations are dependent on the size and shape of nanoparticle support. Moreover, we show that localization of the charge in quantized nanoparticles (2 nm), demonstrated as the blue shift of particle absorption, diminishes SERS enhancement. Importantly, the smallest concentration of adsorbed molecules shows the largest Raman enhancements suggesting the possibility for high sensitivity of this system in the detection of biomolecules that form a charge transfer complex with metal oxide nanoparticles. The wavelength-dependent properties of a hybrid composite suggest a Raman resonant state. Adsorbed molecules that do not show a charge transfer complex show weak enhancements probably due to the dielectric cavity effect.

  11. Effect of kenaf fiber age on PLLA composite properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The age of the kenaf (Hibiscus cannabinus L.) fiber dictates its pore architecture. The impact of increasing age of plant fiber on the corresponding composite can impact material selection for enhanced composite performance. Bast fibers stems of kenaf, a warm season tropical herbaceous annual plant ...

  12. Tracking accelerated aging of composites with ultrasonic attenuation measurements

    SciTech Connect

    Chinn, D.J.; Durbin, P.F.; Thomas, G.H.; Groves, S.E.

    1996-10-01

    Composite materials are steadily replacing traditional materials in many industries. For many carbon composite materials, particularly in aerospace applications, durability is a critical design parameter which must be accurately characterized. Lawrence Livermore National Laboratory (LLNL) and Boeing Commercial Airplane Group have established a cooperative research and development agreement (CRADA) to assist in the high speed research program at Boeing. LLNL`s expertise in fiber composites, computer modeling, mechanical testing, chemical analysis and nondestructive evaluation (ND) will contribute to the study of advanced composite materials in commercial aerospace applications. Through thermo-mechanical experiments with periodic chemical analysis and nondestructive evaluation, the aging mechanisms in several continuous fiber polymer composites will be studied. Several measurement techniques are being studied for their correlation with aging. This paper describes through-transmission ultrasonic attenuation measurements of isothermally aged composite materials and their use as a tracking parameter for accelerated aging.

  13. Hybrid S2/Carbon Epoxy Composite Armours Under Blast Loads

    NASA Astrophysics Data System (ADS)

    Dolce, F.; Meo, Michele; Wright, A.; French, M.; Bernabei, M.

    2012-06-01

    Civil and military structures, such as helicopters, aircrafts, naval ships, tanks or buildings are susceptible to blast loads as terroristic attacks increases, therefore there is the need to design blast resistant structures. During an explosion the peak pressure produced by shock wave is much greater than the static collapse pressure. Metallic structures usually undergo large plastic deformations absorbing blast energy before reaching equilibrium. Due to their high specific properties, fibre-reinforced polymers are being considered for energy absorption applications in blast resistant armours. A deep insight into the relationship between explosion loads, composite architecture and deformation/fracture behaviour will offer the possibility to design structures with significantly enhanced energy absorption and blast resistance performance. This study presents the results of a numerical investigation aimed at understanding the performance of a hybrid composite (glass/carbon fibre) plate subjected to blast loads using commercial LS-DYNA software. In particular, the paper deals with numerical 3D simulations of damages caused by air blast waves generated by C4 charges on two fully clamped rectangular plates made of steel and hybrid (S2/Carbon) composite, respectively. A Multi Materials Arbitrary Lagrangian Eulerian (MMALE) formulation was used to simulate the shock phenomenon. For the steel plates, the Johnson-Cook material model was employed. For the composite plates both in-plane and out-of-plane failure criteria were employed. In particular, a contact tiebreak formulation with a mixed mode failure criteria was employed to simulate delamination failure. As for the steel plates the results showed that excellent correlation with the experimental data for the two blast load conditions in terms of dynamic and residual deflection for two different C4 charges. For the composite plates the numerical results showed that, as expected, a wider delamination damage was observed

  14. Aging of a Polymer Core Composite Conductor under combined ozone and temperature conditions

    NASA Astrophysics Data System (ADS)

    Middleton, James M.

    The next generation High Temperature Low Sag Polymer Core Composite Conductors (HTLS PCCC) can experience harsh in-service environments including high temperature and highly concentrated ozone. In some extreme cases, it is possible that the conductors will experience temperatures of up to 180°C and ozone concentrations as high as 1% (10,000 ppm). Therefore, the primary goal of this research was to determine the most damaging aging conditions which could negatively affect the in-service life of the conductors. This included characterizing the aging in ozone and at high temperature of the HTLS PCCC hybrid composite rods and neat resin. It was found that exposure to 1% ozone for up to three months at room temperature did not negatively affect the flexural performance of either the neat resin epoxy, or the hybrid composite rods. When aged up to a year at 140°C no detrimental effect on flexural performance of the composite was observed, as opposed to aging at 180°C, which had a very negative effect on the properties. The aging of the epoxy at 140°C was driven almost entirely by temperature and the effect of 1% ozone, even at that temperature, was insignificant for aging times up to ninety days. A finite element model was developed and showed the residual stresses developed after aging at 140°C for a year were minimal, but for temperatures higher than 160°C were substantial. From this it was determined that the aging was thermally driven, and atmospheric high temperatures were the most damaging conditions for the PCCC conductors.

  15. Effect of temperature on the dynamic characteristics of the glass-carbon fiber hybrid composites

    NASA Astrophysics Data System (ADS)

    Hidayat, Yon Afif; Susilo, Didik Djoko; Raharjo, Wijang W.

    2016-03-01

    This study aimed to investigate the effect of temperature on the dynamic characteristics of hybrid composites. Hybrid composites consisting of unsaturated polyester resin and glass fiber reinforced with carbon fiber. The volume fraction used in this study was 0.4. The hybrid composite was made using hand lay-up technique. The dynamic characteristics were obtained through vibration testing. The testing was conducted according to ASTM E756. The variables studied were composite without heating, heating at 100 °C, 200 °C and 280 °C. The experiments were done in three mounting configurations, i.e. upright, downward and horizontal configurations. The natural frequency and damping ratio was determined using half-power bandwidth method. The results showed that heating of composite structure affects the natural frequency and damping ratio of the hybrid composite. Heating until 100 °C will increase the natural frequency of the hybrid composite and decrease the damping ratio, but heating at the temperature above 100 °C will decrease the natural frequency and will damage the hybrid composite structure. The composite mounting configurations do not give significant effect to natural frequency and damping ratio of the hybrid composites.

  16. Fatigue Life Analysis of Tapered Hybrid Composite Flexbeams

    NASA Technical Reports Server (NTRS)

    Murri, Gretchen B.; Schaff, Jeffery R.; Dobyns, Alan L.

    2002-01-01

    Nonlinear-tapered flexbeam laminates from a full-size composite helicopter rotor hub flexbeam were tested under combined constant axial tension and cyclic bending loads. The two different graphite/glass hybrid configurations tested under cyclic loading failed by delamination in the tapered region. A 2-D finite element model was developed which closely approximated the flexbeam geometry, boundary conditions, and loading. The analysis results from two geometrically nonlinear finite element codes, ANSYS and ABAQUS, are presented and compared. Strain energy release rates (G) obtained from the above codes using the virtual crack closure technique (VCCT) at a resin crack location in the flexbeams are presented for both hybrid material types. These results compare well with each other and suggest that the initial delamination growth from the resin crack toward the thick region of the flexbeam is strongly mode II. The peak calculated G values were used with material characterization data to calculate fatigue life curves and compared with test data. A curve relating maximum surface strain to number of loading cycles at delamination onset compared reasonably well with the test results.

  17. Fatigue Damage Mechanisms in Advanced Hybrid Titanium Composite Laminates

    NASA Technical Reports Server (NTRS)

    Johnson, W. Steven; Rhymer, Donald W.; St.Clair, Terry L. (Technical Monitor)

    2000-01-01

    Hybrid Titanium Composite Laminates (HTCL) are a type of hybrid composite laminate with promise for high-speed aerospace applications, specifically designed for improved damage tolerance and strength at high-temperature (350 F, 177 C). However, in previous testing, HTCL demonstrated a propensity to excessive delamination at the titanium/PMC interface following titanium cracking. An advanced HTCL has been constructed with an emphasis on strengthening this interface, combining a PETI-5/IM7 PMC with Ti-15-3 foils prepared with an alkaline-perborate surface treatment. This paper discusses how the fatigue capabilities of the "advanced" HTCL compare to the first generation HTCL which was not modified for interface optimization, in both tension-tension (R = 0.1) and tension-compression (R=-0.2). The advanced HTCL under did not demonstrate a significant improvement in fatigue life, in either tension-tension or tension-compression loading. However, the advanced HTCL proved much more damage tolerant. The R = 0.1 tests revealed the advanced HTCL to increase the fatigue life following initial titanium ply damage up to 10X that of the initial HTCL at certain stress levels. The damage progression following the initial ply damage demonstrated the effect of the strengthened PMC/titanium interface. Acetate film replication of the advanced HTCL edges showed a propensity for some fibers in the adjacent PMC layers to fail at the point of titanium crack formation, suppressing delamination at the Ti/PMC interface. The inspection of failure surfaces validated these findings, revealing PMC fibers bonded to the majority of the titanium surfaces. Tension compression fatigue (R = -0.2) demonstrated the same trends in cycles between initial damage and failure, damage progression, and failure surfaces. Moreover, in possessing a higher resistance to delamination, the advanced HTCL did not exhibit buckling following initial titanium ply cracking under compression unlike the initial HTCL.

  18. Sulfur-Containing Organic-Inorganic Hybrid Gel Compositions and Aerogels

    NASA Technical Reports Server (NTRS)

    Evans, Owen R. (Inventor); Dong, Wenting (Inventor); Deshpande, Kiranmayi (Inventor)

    2015-01-01

    Methods and materials are described for preparing organic-inorganic hybrid gel compositions where a sulfur-containing cross-linking agent covalently links the organic and inorganic components. The gel compositions are further dried to provide porous gel compositions and aerogels. The mechanical and thermal properties of the dried gel compositions are also disclosed.

  19. Ageing characteristics of aluminium alloy aluminosilicate discontinuous fiber reinforced composites

    SciTech Connect

    Nath, D.; Singh, V.

    1999-03-05

    Development of continuous fiber reinforced metal matrix composites is aimed at providing high specific strength and stiffness needed for aerospace and some critical high temperature structural applications. Considerable efforts have been made, during the last decade, to improve the strength of age-hardening aluminium alloy matrix composites by suitable heat treatment. It has also been well established that age-hardenable aluminium alloy composites show accelerated ageing behavior because of enhanced dislocation density at the fiber/matrix interface resulting from thermal expansion mismatch between ceramic fiber and the metal matrix. The accelerated ageing of aluminium alloy composites either from dislocation density or the residual stress, as a result of thermal expansion mismatch is dependent on the size of whisker and particulate. Investigations have also been made on the effect of volume fraction of particulate on the ageing behavior of aluminium alloys. The present investigation is concerned with characterization of age-hardening behavior of an Al-Si-Cu-Mg(AA 336) alloy alumino-silicate discontinuous fiber-reinforced composites (referred to as aluminium MMCs in the present text) being developed for automotive pistons. An effort is made to study the effect of volume fraction of the reinforcement on age-hardening behavior of this composite.

  20. Analysis of SMA Hybrid Composite Structures using Commercial Codes

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.; Patel, Hemant D.

    2004-01-01

    A thermomechanical model for shape memory alloy (SMA) actuators and SMA hybrid composite (SMAHC) structures has been recently implemented in the commercial finite element codes MSC.Nastran and ABAQUS. The model may be easily implemented in any code that has the capability for analysis of laminated composite structures with temperature dependent material properties. The model is also relatively easy to use and requires input of only fundamental engineering properties. A brief description of the model is presented, followed by discussion of implementation and usage in the commercial codes. Results are presented from static and dynamic analysis of SMAHC beams of two types; a beam clamped at each end and a cantilevered beam. Nonlinear static (post-buckling) and random response analyses are demonstrated for the first specimen. Static deflection (shape) control is demonstrated for the cantilevered beam. Approaches for modeling SMAHC material systems with embedded SMA in ribbon and small round wire product forms are demonstrated and compared. The results from the commercial codes are compared to those from a research code as validation of the commercial implementations; excellent correlation is achieved in all cases.

  1. Analysis of SMA hybrid composite structures using commercial codes

    NASA Astrophysics Data System (ADS)

    Turner, Travis L.; Patel, Hemant D.

    2004-07-01

    A thermomechanical model for shape memory alloy (SMA) actuators and SMA hybrid composite (SMAHC) structures has been recently implemented in the commercial finite element codes MSC.Nastran and ABAQUS. The model may be easily implemented in any code that has the capability for analysis of laminated composite structures with temperature dependent material properties. The model is also relatively easy to use and requires input of only fundamental engineering properties. A brief description of the model is presented, followed by discussion of implementation and usage in the commercial codes. Results are presented from static and dynamic analysis of SMAHC beams of two types; a beam clamped at each end and a cantilevered beam. Nonlinear static (post-buckling) and random response analyses are demonstrated for the first specimen. Static deflection (shape) control is demonstrated for the cantilevered beam. Approaches for modeling SMAHC material systems with embedded SMA in ribbon and small round wire product forms are demonstrated and compared. The results from the commercial codes are compared to those from a research code as validation of the commercial implementations; excellent correlation is achieved in all cases.

  2. Development of hybrid composite co-pultruded structural members

    NASA Astrophysics Data System (ADS)

    Honickman, Hart Noah

    Fibre reinforced polymer (FRP) materials offer many advantages over conventional metallic structural materials due to their high specific strength and stiffness, long fatigue life, and resistance to environmental corrosion. However, these materials present some unique engineering challenges due to their anisotropy and heterogeneity. The connection of these composite parts to adjacent components often results in complex and counter-intuitive states of stress that can be quite difficult to model. Furthermore, since these materials are, in a sense, synthesized during the fabrication of the final part, the mechanical properties that can be expected from FRP structures are largely dependent upon highly skilled workmanship. Pultrusion is a manufacturing technique that is intended for the mass-production of long FRP parts having continuous cross-sectional geometry. Although it has not yet been optimized for the aerospace industry, with some qualification research, pultrusion may prove to offer many benefits over conventional methods of manufacturing composite aircraft parts. The present dissertation investigates the possibility of co-pultruding FRP parts with embedded non-FRP materials (such as metallic materials), which could serve as integral hard points to facilitate serviceable mechanical connections to adjacent parts. It is shown that these hybrid co-pultruded members offer substantial light-weighting benefits over conventional metallic components, while retaining the ability to employ serviceable mechanical fasteners. Simple unidimensional beam models are of great value when validating the results of complex finite element analyses of aircraft wing-stringers, or other similar structural members. It is demonstrated in the present dissertation that classical unidimensional beam-type analytical models often yield unconservative predictions (over-predictions) of stiffness and elastic stability when used for the analyses of FRP beams and columns. In fact, specific

  3. Mechanical Properties of Sisal/Coir Fiber Reinforced Hybrid Composites Fabricated by Cold Pressing Method

    NASA Astrophysics Data System (ADS)

    Akash; Sreenivasa Rao, K. V.; Venkatesha Gupta, N. S.; kumar, D. S. Arun

    2016-09-01

    Bio-composites have less density and are environmental friendly materials that require less energy during production and subsequent machining. This paper reports the mechanical and water absorption properties of sodium hydroxide (NaOH) treated sisal and coir fiber reinforced epoxy resin thermo set hybrid composites. The hybrid composites were prepared by traditional cold pressing method at room temperature with applied pressure of 410.4 kg/cm2 for 3 hours pressurization time. The mechanical properties were characterized according to ASTM standards. Hybrid composites with 40wt% of sisal and coir fiber were found to possess higher tensile strength of 48.2MPa and flexural strength of 76.68 MPa among the fabricated hybrid composite specimens. Absorption of water increases with increasing fiber volume. The experimental result also show that the sisal and coir fibers are promising reinforcement for use in low cost bio-composites which have high strength to weight ratio.

  4. Water aging reverses residual stresses in hydrophilic dental composites.

    PubMed

    Park, J W; Ferracane, J L

    2014-02-01

    Dental composites develop residual stresses during polymerization due to shrinkage. These stresses may change with time because of relaxation and water sorption in the oral environment. This phenomenon is likely dependent on the composition of the materials, specifically their hydrophilic characteristics, and could result in deleterious stresses on restorative materials and tooth structure. The purpose of this experiment was to use the thin ring-slitting method to compare the residual stress generated within composite materials of varying hydrophilicity when aged in wet and dry conditions after polymerization. Water sorption, solubility, elastic modulus, and residual stresses were measured in 6 commercial composites/cements aged in water and dry conditions. The self-adhesive resin cement showed the highest water sorption and solubility. All composites showed initial residual contraction stresses, which were maintained when aged dry. Residual stresses in 2 of the self-adhesive cements and the polyacid-modified composite aged in wet conditions resulted in a net expansion. This experiment verified that residual shrinkage stresses in dental composites can be reversed during aging in water, resulting in a net expansion, with the effect directly related to their hydrophilic properties.

  5. Water aging reverses residual stresses in hydrophilic dental composites.

    PubMed

    Park, J W; Ferracane, J L

    2014-02-01

    Dental composites develop residual stresses during polymerization due to shrinkage. These stresses may change with time because of relaxation and water sorption in the oral environment. This phenomenon is likely dependent on the composition of the materials, specifically their hydrophilic characteristics, and could result in deleterious stresses on restorative materials and tooth structure. The purpose of this experiment was to use the thin ring-slitting method to compare the residual stress generated within composite materials of varying hydrophilicity when aged in wet and dry conditions after polymerization. Water sorption, solubility, elastic modulus, and residual stresses were measured in 6 commercial composites/cements aged in water and dry conditions. The self-adhesive resin cement showed the highest water sorption and solubility. All composites showed initial residual contraction stresses, which were maintained when aged dry. Residual stresses in 2 of the self-adhesive cements and the polyacid-modified composite aged in wet conditions resulted in a net expansion. This experiment verified that residual shrinkage stresses in dental composites can be reversed during aging in water, resulting in a net expansion, with the effect directly related to their hydrophilic properties. PMID:24272790

  6. Fracture toughness of experimental dental composites aged in ethanol.

    PubMed

    Ferracane, J L; Berge, H X

    1995-07-01

    Fracture toughness (KIc) is an intrinsic property which may be related to the ability of a restorative material to resist fracture and abrasion. This property may change for a dental composite restorative due to the effects of various oral solvents. The hypothesis to be tested was that aging in ethanol would cause a reduction in the fracture toughness of dental composites, and that the extent of this reduction might be dependent upon certain compositional variables. The fracture toughnesses of three series of experimental composites with various degrees of conversion, filler volume, and percent of silane-treated fillers were compared after the composites were aged for periods of one month and six months in 75% ethanol/water, a solvent which serves as a food-simulating liquid. An unfilled Bis-GMA/TEGDMA resin served as the control. All composites, with the exception of one subjected to a post-light-curing heat treatment, experienced a significant reduction (from 30 to 56%) in KIc after being aged in 75% ethanol for six months. A similar reduction in KIc of 58% for the unfilled resin suggested that the reduction for the composites was due to a weakening of the resin matrix, which facilitated crack propagation. A simultaneous reduction in microhardness was also demonstrated. One month of aging in ethanol also produced large reductions in KIc for specimens with insufficient cure and minimal filler volume, suggesting that the properties of the resin matrix predominated for these composites.(ABSTRACT TRUNCATED AT 250 WORDS)

  7. INHYD: Computer code for intraply hybrid composite design. A users manual

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1983-01-01

    A computer program (INHYD) was developed for intraply hybrid composite design. A users manual for INHYD is presented. In INHYD embodies several composite micromechanics theories, intraply hybrid composite theories, and an integrated hygrothermomechanical theory. The INHYD can be run in both interactive and batch modes. It has considerable flexibility and capability, which the user can exercise through several options. These options are demonstrated through appropriate INHYD runs in the manual.

  8. Composite Aging Markers Can Be Used for Quantitative Profiling of Aging.

    PubMed

    Shamir, Lior

    2015-01-01

    In the absence of a single marker that reliably reflects biological aging, or even an exact definition of biological age, compound aging scores that combine multiple aging biomarkers into a single composite aging score can quantitatively reflect the age-related changes over time. If aging is viewed as the broad accumulation of alterations over time, a composite score that reflects numerous diverse aspects of these alterations can be used as a quantitative approximation of aging. Profiling the changes of the composite aging score over time shows variations in the pace of aging at different chronological ages, such that the changes over time show distinct stages separated by a short period of rapid aging. These observations are difficult to explain by molecular entropy or stochastic accumulation of irreparable environmental damage alone, as a process driven solely by entropy or stochasticity is not expected to have signs of distinct stages or leaps in aging. These results are in agreement with some previous observations in other organisms, indicating the possibility of the involvement of pathways in the process of aging. Given this evidence, the contention that aging can be driven also by biological pathways should be considered. PMID:26088420

  9. Monotonic and fatigue properties of kenaf /glass hybrid composites under fully reversed cyclic loading

    NASA Astrophysics Data System (ADS)

    Sharba, M. J.; Leman, Z.; Sultan, M. T. H.; Ishak, M. R.; Hanim, M. A. A.

    2015-12-01

    The aim of this work is to investigate the effect of hybridization of kenaf-glass fibers reinforced unsaturated polyester on fatigue life. Three types of composites were fabricated using hands lay-up method, namely, kenaf, glass, and hybrid composites with 30% of weight fraction, the hybrid was mixed with a ratio of kenaf: glass 10:20. Monotonic tests were achieved (Tensile and compression) to determine the fatigue stress levels. Fully reversed fatigue loading was conducted with a stress ratio of -1 and stress levels 55-85% of the ultimate static stresses, all tests were conducted at 10 Hz of frequency. The results proof a positive hybrid composite; also agree with the rule of mixture that can predict the final composite properties. Moreover, it's been observed an improvement in overall mechanical properties of hybrid compared to individual ones.

  10. A compositional and dynamic model for face aging.

    PubMed

    Suo, Jinli; Zhu, Song-Chun; Shan, Shiguang; Chen, Xilin

    2010-03-01

    In this paper, we present a compositional and dynamic model for face aging. The compositional model represents faces in each age group by a hierarchical And-Or graph, in which And nodes decompose a face into parts to describe details (e.g., hair, wrinkles, etc.) crucial for age perception and Or nodes represent large diversity of faces by alternative selections. Then a face instance is a transverse of the And-Or graph-parse graph. Face aging is modeled as a Markov process on the parse graph representation. We learn the parameters of the dynamic model from a large annotated face data set and the stochasticity of face aging is modeled in the dynamics explicitly. Based on this model, we propose a face aging simulation and prediction algorithm. Inversely, an automatic age estimation algorithm is also developed under this representation. We study two criteria to evaluate the aging results using human perception experiments: 1) the accuracy of simulation: whether the aged faces are perceived of the intended age group, and 2) preservation of identity: whether the aged faces are perceived as the same person. Quantitative statistical analysis validates the performance of our aging model and age estimation algorithm.

  11. A compositional and dynamic model for face aging.

    PubMed

    Suo, Jinli; Zhu, Song-Chun; Shan, Shiguang; Chen, Xilin

    2010-03-01

    In this paper, we present a compositional and dynamic model for face aging. The compositional model represents faces in each age group by a hierarchical And-Or graph, in which And nodes decompose a face into parts to describe details (e.g., hair, wrinkles, etc.) crucial for age perception and Or nodes represent large diversity of faces by alternative selections. Then a face instance is a transverse of the And-Or graph-parse graph. Face aging is modeled as a Markov process on the parse graph representation. We learn the parameters of the dynamic model from a large annotated face data set and the stochasticity of face aging is modeled in the dynamics explicitly. Based on this model, we propose a face aging simulation and prediction algorithm. Inversely, an automatic age estimation algorithm is also developed under this representation. We study two criteria to evaluate the aging results using human perception experiments: 1) the accuracy of simulation: whether the aged faces are perceived of the intended age group, and 2) preservation of identity: whether the aged faces are perceived as the same person. Quantitative statistical analysis validates the performance of our aging model and age estimation algorithm. PMID:20075467

  12. Composite Overwrapped Pressure Vessels (COPV) Materials Aging Issues

    NASA Technical Reports Server (NTRS)

    2010-01-01

    This slide presentation reviews some of the issues concerning the aging of the materials in a Composite Overwrapped Pressure Vessels (COPV). The basic composition of the COPV is a Boss, a composite overwrap, and a metallic liner. The lifetime of a COPV is affected by the age of the overwrap, the cyclic fatigue of the metallic liner, and stress rupture life, a sudden and catastrophic failure of the overwrap while holding at a stress level below the ultimate strength for an extended time. There is information about the coupon tests that were performed, and a test on a flight COPV.

  13. Fatigue Life Methodology for Tapered Hybrid Composite Flexbeams

    NASA Technical Reports Server (NTRS)

    urri, Gretchen B.; Schaff, Jeffery R.

    2006-01-01

    Nonlinear-tapered flexbeam specimens from a full-size composite helicopter rotor hub flexbeam were tested under combined constant axial tension and cyclic bending loads. Two different graphite/glass hybrid configurations tested under cyclic loading failed by delamination in the tapered region. A 2-D finite element model was developed which closely approximated the flexbeam geometry, boundary conditions, and loading. The analysis results from two geometrically nonlinear finite element codes, ANSYS and ABAQUS, are presented and compared. Strain energy release rates (G) associated with simulated delamination growth in the flexbeams are presented from both codes. These results compare well with each other and suggest that the initial delamination growth from the tip of the ply-drop toward the thick region of the flexbeam is strongly mode II. The peak calculated G values were used with material characterization data to calculate fatigue life curves for comparison with test data. A curve relating maximum surface strain to number of loading cycles at delamination onset compared well with the test results.

  14. Mechanical Properties of Graphene Nanoplatelet/Carbon Fiber/Epoxy Hybrid Composites: Multiscale Modeling and Experiments

    NASA Technical Reports Server (NTRS)

    Hadden, C. M.; Klimek-McDonald, D. R.; Pineda, E. J.; King, J. A.; Reichanadter, A. M.; Miskioglu, I.; Gowtham, S.; Odegard, G. M.

    2015-01-01

    Because of the relatively high specific mechanical properties of carbon fiber/epoxy composite materials, they are often used as structural components in aerospace applications. Graphene nanoplatelets (GNPs) can be added to the epoxy matrix to improve the overall mechanical properties of the composite. The resulting GNP/carbon fiber/epoxy hybrid composites have been studied using multiscale modeling to determine the influence of GNP volume fraction, epoxy crosslink density, and GNP dispersion on the mechanical performance. The hierarchical multiscale modeling approach developed herein includes Molecular Dynamics (MD) and micromechanical modeling, and it is validated with experimental testing of the same hybrid composite material system. The results indicate that the multiscale modeling approach is accurate and provides physical insight into the composite mechanical behavior. Also, the results quantify the substantial impact of GNP volume fraction and dispersion on the transverse mechanical properties of the hybrid composite while the effect on the axial properties is shown to be insignificant.

  15. Mechanical Properties of Graphene Nanoplatelet/Carbon Fiber/Epoxy Hybrid Composites: Multiscale Modeling and Experiments

    NASA Technical Reports Server (NTRS)

    Hadden, C. M.; Klimek-McDonald, D. R.; Pineda, E. J.; King, J. A.; Reichanadter, A. M.; Miskioglu, I.; Gowtham, S.; Odegard, G. M.

    2015-01-01

    Because of the relatively high specific mechanical properties of carbon fiber/epoxy composite materials, they are often used as structural components in aerospace applications. Graphene nanoplatelets (GNPs) can be added to the epoxy matrix to improve the overall mechanical properties of the composite. The resulting GNP/carbon fiber/epoxy hybrid composites have been studied using multiscale modeling to determine the influence of GNP volume fraction, epoxy crosslink density, and GNP dispersion on the mechanical performance. The hierarchical multiscale modeling approach developed herein includes Molecular Dynamics (MD) and micromechanical modeling, and it is validated with experimental testing of the same hybrid composite material system. The results indicate that the multiscale modeling approach is accurate and provides physical insight into the composite mechanical behavior. Also, the results quantify the substantial impact of GNP volume fraction and dispersion on the transverse mechanical properties of the hybrid composite, while the effect on the axial properties is shown to be insignificant.

  16. Mechanical Properties of Graphene Nanoplatelet Carbon Fiber Epoxy Hybrid Composites: Multiscale Modeling and Experiments

    NASA Technical Reports Server (NTRS)

    Hadden, Cameron M.; Klimek-McDonald, Danielle R.; Pineda, Evan J.; King, Julie A.; Reichanadter, Alex M.; Miskioglu, Ibrahim; Gowtham, S.; Odegard, Gregory M.

    2015-01-01

    Because of the relatively high specific mechanical properties of carbon fiber/epoxy composite materials, they are often used as structural components in aerospace applications. Graphene nanoplatelets (GNPs) can be added to the epoxy matrix to improve the overall mechanical properties of the composite. The resulting GNP/carbon fiber/epoxy hybrid composites have been studied using multiscale modeling to determine the influence of GNP volume fraction, epoxy crosslink density, and GNP dispersion on the mechanical performance. The hierarchical multiscale modeling approach developed herein includes Molecular Dynamics (MD) and micromechanical modeling, and it is validated with experimental testing of the same hybrid composite material system. The results indicate that the multiscale modeling approach is accurate and provides physical insight into the composite mechanical behavior. Also, the results quantify the substantial impact of GNP volume fraction and dispersion on the transverse mechanical properties of the hybrid composite, while the effect on the axial properties is shown to be insignificant.

  17. Mechanical behavior of glass fiber polyester hybrid composite filled with natural fillers

    NASA Astrophysics Data System (ADS)

    Gupta, G.; Gupta, A.; Dhanola, A.; Raturi, A.

    2016-09-01

    Now-a-days, the natural fibers and fillers from renewable natural resources offer the potential to act as a reinforcing material for polymer composite material alternative to the use of synthetic fiber like as; glass, carbon and other man-made fibers. Among various natural fibers and fillers like banana, wheat straw, rice husk, wood powder, sisal, jute, hemp etc. are the most widely used natural fibers and fillers due to its advantages like easy availability, low density, low production cost and reasonable physical and mechanical properties This research work presents the effect of natural fillers loading with 5%, 10% and 15% on mechanical behavior of polyester based hybrid composites. The result of test depicted that hybrid composite has far better properties than single fibre glass reinforced composite under impact and flexural loads. However it is found that the hybrid composite have better strength as compared to single glass fibre composites.

  18. In vitro aging of a heat/pressure-cured composite.

    PubMed

    Drummond, J L; Savers, E E

    1993-05-01

    Specimens of a heat/pressure-cured microfill composite were aged in saline or distilled water at 37 degrees C up to 12 mon to determine if the flexure strength was affected by the aging media. No significant difference in the flexure strength was observed between the controls and the 12 mon aged specimens. Cyclic testing in distilled water resulted in a lower flexure strength at fracture than that observed for the aged specimens. This lower strength is attributed to fatigue of the silane bond, the resin matrix, and/or the filler particles.

  19. Age hardening of 6061/alumina-silica fiber composite

    SciTech Connect

    Khangaonkar, P.R.; Shamsul, J.B.; Azmi, R.

    1994-12-31

    Continuous alumina-silica fiber (Altex of Sumitomo) which yields high performance composites with some aluminium alloys was tried for squeeze cast 6061 based composites with volume fractions of 0.5 and 0.32, and the matrix microhardness and resistivity changes during age hardening were studied. The matrix in the composites hardened much more than the unreinforced alloy. Microhardness increases of up to 70 VPN above the solution treated condition at various aging temperatures were observed. The resistivity variation indicated an appreciable state of internal stress which continued to persist even when hardness fell by overaging. Energy dispersive X-ray analysis indicated that the regions close to the fibers had a higher silicon content than the matrix, and amorphous silica in the fiber may have a role in the formation of an enriched layer which may help the bonding and strength in the composite.

  20. Durability of polymeric composites after elevated temperature aging

    NASA Astrophysics Data System (ADS)

    Poole, Eric Luther

    The Compression After Impact (CAI) strength of polymeric composites after long term elevated temperature aging is studied. Aging temperatures range from 149sp°C to 204sp°C (300sp°F to 400sp°F). Two types of matrix material are studied, a thermoset bismaleimide (5260) and a thermoplastic polyimide (K3B). Glass transition temperature (Tsb{g}) and fracture toughness are measured after aging. Microscopy and Secondary Ion Mass Spectroscopy (SIMS) are used to evaluate the aged composites. Out-of-plane bending of the CAI specimens during compression is measured by shadow moire. Moire interferometry is used to determine in-plane displacement and strain fields around the impact damage. Results show that the CAI strength degrades with aging for both K3B and 5260. The 5260 matrix suffers from thermo-oxidative degradation at higher temperatures. Surface decomposition causes weight loss and reduces mechanical properties. The CAI strength of the K3B matrix composite also decreases after aging. Evidence of an oxidation reaction is found in the K3B polymer by SIMS, but no weight loss is associated with this chemical reaction. Measured changes in fracture toughness and Tsb{g} do not correlate with CAI strength degradation. Stiffness changes due to aging are insignificant in this study. The degradation region is measured by microscopy near the surface of composites after long aging times. The depth of the degradation zone is dependent on aging time. Degradation growth is modeled with finite elements using diffusion/reaction governing equations. Finite element results agree well with the experimental data.

  1. Reverse Aging of Composite Materials for Aeronautical Applications

    NASA Astrophysics Data System (ADS)

    lannone, Michele

    2008-08-01

    Hygro-thermal ageing of polymer matrix composite materials is a major issue for all the aeronautical structures. For carbon-epoxy composites generally used in aeronautical applications the major effect of ageing is the humidity absorption, which induces a plasticization effect, generally decreasing Tg and elastic moduli, and finally design allowables. A thermodynamical and kinetic study has been performed, aimed to establish a program of periodic heating of the composite part, able to reversing the ageing effect by inducing water desorption. The study was founded on a simple model based on Fick's law, coupled with a concept of "relative saturation coefficient" depending on the different temperature of the composite part and the environment. The behaviour of some structures exposed to humidity and "reverse aged" by heating has been virtually tested. The conclusion of the study allowed to issue a specific patent application for aeronautical structures to be designed on the basis of a "humidity free" concept which allows the use of higher design allowables; having as final results lighter composite structures with a simplified certification process.

  2. Thermomechanical response of shape memory alloy hybrid composites

    NASA Astrophysics Data System (ADS)

    Turner, Travis L.

    2000-10-01

    This study examines the use of embedded shape memory alloy (SMA) actuators for adaptive control of the themomechanical response of composite structures. Control of static and dynamic responses are demonstrated including thermal buckling, thermal post-buckling, vibration, sonic fatigue, and acoustic transmission. A thermomechanical model is presented for analyzing such shape memory alloy hybrid composite (SMAHC) structures exposed to thermal and mechanical loads. Also presented are (1) fabrication procedures for SMAHC specimens, (2) characterization of the constituent materials for model quantification, (3) development of the test apparatus for conducting static and dynamic experiments on specimens with and without SMA, (4) discussion of the experimental results, and (5) validation of the analytical and numerical tools developed in the study. The constitutive model developed to describe the mechanics of a SMAHC lamina captures the material nonlinearity with temperature of the SMA and matrix material if necessary. It is in a form that is amenable to commercial finite element (FE) code implementation. The model is valid for constrained, restrained, or free recovery configurations with appropriate measurements of fundamental engineering properties. This constitutive model is used along with classical lamination theory and the FE method to formulate the equations of motion for panel-type structures subjected to steady-state thermal and dynamic mechanical loads. Mechanical loads that are considered include acoustic pressure, inertial (base acceleration), and concentrated forces. Four solution types are developed from the governing equations including thermal buckling, thermal post-buckling, dynamic response, and acoustic transmission/radiation. These solution procedures are compared with closed-form and/or other known solutions to benchmark the numerical tools developed in this study. Practical solutions for overcoming fabrication issues and obtaining repeatable

  3. Biomechanical characteristics of polymeric UHMWPE composites with hybrid matrix and dispersed fillers

    NASA Astrophysics Data System (ADS)

    Panin, Sergey; Kornienko, Lyudmila; Shilko, Sergey; Thuc, Nguyen Xuan; Korchagin, Mikhail; Chaikina, Marina

    2015-11-01

    In order to develop artificial joint implants some biomechanical properties of composites with UHMWPE and hybrid (polymer-polymeric) "UHMWPE+PTFE" matrix with dispersed fillers were studied. A comparative analysis of the effectiveness of adding hydroxyapatite micron- and nanopowders as a biocompatible filler was carried out. It was shown that under dry sliding friction the wear rate of nanocomposites with the hybrid matrix is lower as compared with composites with the non-hybrid one. Mechanical activation of components further enhances the durability of nano- and microcomposites to almost double it without any significant reduction in the strength characteristics.

  4. Long-term ageing and materials degradation of hybrid mica compressive seals for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Chou, Yeong-Shyung; Stevenson, J. W.

    Hybrid phlogopite mica seals with silver interlayers were evaluated in long-term isothermal ageing tests in a dual environment consisting of dilute hydrogen versus air at 800 °C. High-temperature leak tests with helium showed very stable leakage of 0.01-0.02 sccm cm -1 for 28,366 h under a low applied compressive stress of 82 kPa (12 psi). Post-mortem SEM and EDS analyses of the mica showed minimum degradation in terms of changes in microstructure and chemical composition, although there appeared to be some Ag migration and segregation at interstices between mica flakes. Fluorine was also found to be released from mica. Overall, the low, constant leakage through the hybrid mica/Ag seals clearly demonstrated a very promising candidate for SOFC sealing.

  5. Long-term ageing and materials degradation of hybrid mica compressive seals for solid oxide fuel cells

    SciTech Connect

    Chou, Y. S.; Stevenson, Jeffry W.

    2009-06-15

    Hybrid phlogopite mica seals with silver interlayers were evaluated in long term isothermal ageing tests in a dual environment consisting of dilute hydrogen vs. air at 800 degrees C. High-temperature leak tests with helium showed very stable leakage of 0.01-0.02 sccm/cm for 28366 hrs under a low applied compressive stress of 82 kPa (12 psi). Post-mortem SEM and EDS analyses of the mica showed minimum degradation in terms of changes in microstructure and chemical composition, although there appeared to be some Ag migration and segregation at interstices between mica flakes. Fluorine was also found to be released from mica. Overall, the low, constant leakage through the hybrid mica/Ag seals clearly demonstrated a very promising candidate for SOFC sealing.

  6. Optimization of Wear Behavior of Magnesium Alloy AZ91 Hybrid Composites Using Taguchi Experimental Design

    NASA Astrophysics Data System (ADS)

    Girish, B. M.; Satish, B. M.; Sarapure, Sadanand; Basawaraj

    2016-06-01

    In the present paper, the statistical investigation on wear behavior of magnesium alloy (AZ91) hybrid metal matrix composites using Taguchi technique has been reported. The composites were reinforced with SiC and graphite particles of average size 37 μm. The specimens were processed by stir casting route. Dry sliding wear of the hybrid composites were tested on a pin-on-disk tribometer under dry conditions at different normal loads (20, 40, and 60 N), sliding speeds (1.047, 1.57, and 2.09 m/s), and composition (1, 2, and 3 wt pct of each of SiC and graphite). The design of experiments approach using Taguchi technique was employed to statistically analyze the wear behavior of hybrid composites. Signal-to-noise ratio and analysis of variance were used to investigate the influence of the parameters on the wear rate.

  7. Hybrid composites - State-of-the-art review: Analysis, design, application and fabrication

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.

    1977-01-01

    The review covers hybrid composites that consist of two or more different types of fibers (or fiber composites) in a frequently repeated pattern in a laminate. The fibers considered are boron, graphite, glass, and Kevlar; the resins considered include mostly structural epoxies, with some utilization of polyimides and thermoplastics. The review shows that considerable data have been generated for the tensile strength properties, as well as tensile and thermal fatigue, of interply hybrids, and for the impact resistance of interply and intraply hybrids. The rule of mixtures appears to be adequate for predicting longitudinal and transverse mechanical properties of unidirectional interply hybrids, and linear laminate theory appears to be adequate for predicting the elastic response of hybrids.

  8. Vibration and Operational Characteristics of a Composite-Steel (Hybrid) Gear

    NASA Technical Reports Server (NTRS)

    Handschuh, Robert F.; LaBerge, Kelsen E.; DeLuca, Samuel; Pelagalli, Ryan

    2014-01-01

    Hybrid gears have been tested consisting of metallic gear teeth and shafting connected by composite web. Both free vibration and dynamic operation tests were completed at the NASA Glenn Spur Gear Fatigue Test Facility, comparing these hybrid gears to their steel counterparts. The free vibration tests indicated that the natural frequency of the hybrid gear was approximately 800 Hz lower than the steel test gear. The dynamic vibration tests were conducted at five different rotational speeds and three levels of torque in a four square test configuration. The hybrid gears were tested both as fabricated (machined, composite layup, then composite cure) and after regrinding the gear teeth to the required aerospace tolerance. The dynamic vibration tests indicated that the level of vibration for either type of gearing was sensitive to the level of load and rotational speed.

  9. Flexural fatigue behavior of machinable and light-activated hybrid composites for esthetic restorations.

    PubMed

    Yoshida, Keiichi; Morimoto, Nobuko; Tsuo, Yukiko; Atsuta, Mitsuru

    2004-08-15

    The purpose of this study was to determine the flexural strength and flexural fatigue strength of a machinable composite (GN-I) and three hybrid composites (Artglass, Estenia, and Gradia). Specimens (2 x 2 x 25 mm) were polymerized in a laboratory photo-curing unit and then immersed in water at 37 degrees C for 24 h, 6 months, and 1 year. After each immersion period, flexural strengths (4-PFS) were measured at a cross-head speed of 1 mm/min in 4-point bending (span = 20 mm; distance between inside loading points = 10 mm). The cyclic fatigue test was performed at 2.0 Hz on a fatigue tester. The staircase method was employed for flexural fatigue strength (FFS) using a 5000 cyclic load limitation, 5-MPa stress increment, and 20 specimens for each material. Both 4-PFS and FFS of the machinable composite after all immersion periods were significantly greater than those of the three hybrid composites. The FFS results followed the same pattern as those of the 4-PFS. The Estenia material exhibited the highest 4-PFS and FFS after 24 h of immersion among three hybrid composites, whereas after 1 year of immersion, all three composites showed almost identical 4-PFS and FFS statistically. A strong correlation was observed between 4-PFS and FFS of the machinable composite and three hybrid resin composites.

  10. Piezoelectric properties of the new generation active matrix hybrid (micro-nano) composites

    NASA Astrophysics Data System (ADS)

    Parali, Levent; Şabikoğlu, İsrafil; Kurbanov, Mirza A.

    2014-11-01

    A hybrid piezoelectric composite structure is obtained by addition of nano-sized BaTiO3, SiO2 to the micro-sized PZT and polymers composition. Although the PZT material itself has excellent piezoelectric properties, PZT-based composite variety is limited. Piezoelectric properties of PZT materials can be varied with an acceptor or a donor added to the material. In addition, varieties of PZT-based sensors can be increased with doping polymers which have physical-mechanical, electrophysical, thermophysical and photoelectrical properties. The active matrix hybrid structure occurs when bringing together the unique piezoelectric properties of micro-sized PZT with electron trapping properties of nano-sized insulators (BaTiO3 or SiO2), and their piezoelectric, mechanic and electromechanic properties significantly change. In this study, the relationship between the piezoelectric constant and the coupling factor values of microstructure (PZT-PVDF) and the hybrid structure (PZT-PVDF-BaTiO3) composite are compared. The d33 value and the coupling factor of the hybrid structure have shown an average of 54 and 62% increase according to microstructure composite, respectively. In addition, the d33 value and the coupling factor of the hybrid structure (PZT-HDPE-SiO2) have exhibited about 68 and 52% increase according to microstructure composite (PZT-HDPE), respectively.

  11. Development of flax/carbon fibre hybrid composites for enhanced properties.

    PubMed

    Dhakal, H N; Zhang, Z Y; Guthrie, R; Macmullen, J; Bennett, N

    2013-07-01

    Uni-directional (UD) and cross-ply (CP) cellulosic flax fibre epoxy composites were produced by hybridising UD carbon fibre prepreg onto flax system. A compression moulding technique was used to produce both flax and carbon/flax hybridised laminates. The effect of carbon fibre hybridisation on the water absorption behaviour, thermal and mechanical properties of both UD and CP flax specimens were investigated by means of water absorption, tensile, thermogravemetric analysis and flexural testing. The results showed that water absorption behaviour of hybrid samples are markedly improved compared to those without hybridisation. Similarly, the thermal stability, tensile and flexural properties of the hybrid composites are significantly improved in comparison with UD and CP flax composites without hybridisation. The experimental results suggest that cellulosic flax fibre reinforcement contributed to improve the toughness properties by promoting crack propagation whereas the carbon fibre contributed in improving thermal stability, water absorption behaviour and the overall strength and the stiffness of the hybrid composites.

  12. Finite Element Analysis of Adaptive-Stiffening and Shape-Control SMA Hybrid Composites

    NASA Technical Reports Server (NTRS)

    Gao, Xiu-Jie; Turner, Travis L.; Burton, Deborah; Brinson, L. Catherine

    2005-01-01

    The usage of shape memory materials has extended rapidly to many fields, including medical devices, actuators, composites, structures and MEMS devices. For these various applications, shape memory alloys (SMAs) are available in various forms: bulk, wire, ribbon, thin film, and porous. In this work, the focus is on SMA hybrid composites with adaptive-stiffening or morphing functions. These composites are created by using SMA ribbons or wires embedded in a polymeric based composite panel/beam. Adaptive stiffening or morphing is activated via selective resistance heating or uniform thermal loads. To simulate the thermomechanical behavior of these composites, a SMA model was implemented using ABAQUS user element interface and finite element simulations of the systems were studied. Several examples are presented which show that the implemented model can be a very useful design and simulation tool for SMA hybrid composites.

  13. Finite element analysis of adaptive-stiffening and shape-control SMA hybrid composites

    NASA Astrophysics Data System (ADS)

    Gao, Xiujie; Turner, Travis L.; Burton, Deborah; Brinson, L. Catherine

    2005-05-01

    The usage of shape memory materials has extended rapidly to many fields, including medical devices, actuators, composites, structures and MEMS devices. For these various applications, shape memory alloys (SMAs) are available in various forms: bulk, wire, ribbon, thin film, and porous. In this work, the focus is on SMA hybrid composites with adaptive-stiffening or morphing functions. These composites are created by using SMA ribbons or wires embedded in a polymeric based composite panel/beam. Adaptive stiffening or morphing is activated via selective resistance heating or uniform thermal loads. To simulate the thermomechanical behavior of these composites, a SMA model was implemented using ABAQUS' user element interface and finite element simulations of the systems were studied. Several examples are presented which show that the implemented model can be a very useful design and simulation tool for SMA hybrid composites.

  14. Aging of composite insulators; Simulation by electrical tests

    SciTech Connect

    de Tourreil, C.H. ); Lambeth, P.J.

    1990-07-01

    To assess the long-term performance of 72 kV and 230 kV composite long rod insulators different laboratory aging tests have been developed. This paper reports two principal diagnostic tests used to measure the performance of the insulators, the quick flashover salt fog (QFO SF), and the rapid flashover clean fog (RFO CF) tests. The aging processes were: cement coating and clean fog, salt fog, and cement coating and salt fog. Similar sets of insulators were aged also in the field for over three years, and all the insulators evaluated in the laboratory. The cement/salt fog aging process was found to be the most controllable and realistic, when the results were assessed by means of the RFO CF test.

  15. Effect of natural fibers and bio-resins on mechanical properties in hybrid and non-hybrid composites

    NASA Astrophysics Data System (ADS)

    Fragassa, Cristiano

    2016-05-01

    The aim of the present experimental investigation was to perform a comparative analysis concerning the influence on mechanical properties of natural fibers and/or bio-resins in reinforced thermoset composites. Flax and basalt fibers were selected as natural reinforcements, as single constituents or in hybrid combination. Glass synthetic fibers were used for comparison. Eco-friendly matrixes, both epoxy or vinylester, were considered and compared with composites based on traditional resins. Samples were fabricated by hand lay-up and resin infusion techniques. Cures were accelerated and controlled by applying heat and pressure in autoclave. Tensile, flexural and impact tests were carried out according to ASTM standards.

  16. Hybrid Gear Preliminary Results-Application of Composites to Dynamic Mechanical Components

    NASA Technical Reports Server (NTRS)

    Handschuh, Robert F.; Roberts Gary D.; Sinnamon, R.; Stringer, David B.; Dykas, Brian D.; Kohlman, Lee W.

    2012-01-01

    Composite spur gears were fabricated and then tested at NASA Glenn Research Center. The composite material served as the web of the gear between the gear teeth and a metallic hub for mounting to the torque-applying shaft. The composite web was bonded only to the inner and outer hexagonal features that were machined from an initially all-metallic aerospace quality spur gear. The Hybrid Gear was tested against an all-steel gear and against a mating Hybrid Gear. As a result of the composite to metal fabrication process used, the concentricity of the gears were reduced from their initial high-precision value. Regardless of the concentricity error, the hybrid gears operated successfully for over 300 million cycles at 10000 rpm and 490 in.*lbs torque. Although the design was not optimized for weight, the composite gears were found to be 20% lighter than the all-steel gears. Free vibration modes and vibration/noise tests were also conduct to compare the vibration and damping characteristic of the Hybrid Gear to all-steel gears. The initial results indicate that this type of hybrid design may have a dramatic effect on drive system weight without sacrificing strength.

  17. Fracture properties of aged and post-processed dental composites.

    PubMed

    Drummond, J L; Botsis, J; Zhao, D; Samyn, J

    1998-04-01

    The purpose of this study was to determine the flexure strength (sigma f), Young's modulus (E), and fracture toughness (KIC) of five dental composites after aging in water and air. The composites were, by weight, 75% or 79% glass filler and 25% or 21% resin composed of 60% Bis-GMA and 40% TEG-DMA. The filler was either strontium glass (75Sr or 79Sr) or a combination, by weight, of 90% strontium glass and 10% colloidal silica (75Sr10 or 79Sr10). The specimens, 2 x 4 x 70 mm bars, were aged in either air or distilled water at 37 degrees C and were tested in their respective aging media at a loading rate of 1.22 mm/s. The sigma f and E were tested in four-point loading and the KIC in three-point loading. The addition of the fillers to the unfilled resin resulted in a statistically significant increase in the flexure strength, flexure modulus, and fracture toughness. Aging in air had minimal effect on these properties. However, testing and aging in water led to a significant decrease in the mechanical properties in the first 6 months, but had limited effect from 6 to 12 months.

  18. Lamination residual stresses in hybrid composites, part 1

    NASA Technical Reports Server (NTRS)

    Daniel, I. M.; Liber, T.

    1976-01-01

    An experimental investigation was conducted to study lamination residual stresses for various material and loading parameters. The effects of hybridization on residual stresses and residual properties after thermal cycling under load were determined in angle-ply graphite/Kevlar/epoxy and graphite/S-glass/epoxy laminates. Residual strains in the graphite plies are not appreciably affected by the type and number of hybridizing plies. Computed residual stresses at room temperature in the S-glass plies reach values up to seventy-five percent of the transverse strength of the material. Computed residual stresses in the graphite plies exceed the static strength by approximately ten percent. In the case of Kevlar plies, computed residual stresses far exceed the static strength indicating possible early failure of these plies. Static testing of the hybrids above indicates that failure is governed by the ultimate strain of the graphite plies. In thermally cycled hybrids, in general, residual moduli were somewhat lower and residual strengths were higher than initial values.

  19. Secondary metabolite composition in Citrus x Poncirus trifoliata hybrids

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Poncirus trifoliata L.Raf is used as a parent in citrus rootstock breeding because it confers desirable characteristics, such as disease resistance and cold hardiness. However, fruit of P. trifoliata hybrids typically have unpleasant flavor. The objective of this study was to determine the chemical ...

  20. Composite Organic Radical - Inorganic Hybrid Cathode for Lithium-ion Batteries

    SciTech Connect

    Huang, Qian; Cosimbescu, Lelia; Koech, Phillip K.; Choi, Daiwon; Lemmon, John P.

    2013-07-01

    A new organic radical inorganic hybrid cathode comprised of PTMA/LiFePO4 composite system is developed and reported for the first time. The hybrid cathodes demonstrate high pulse power capability resulting in a significant improvement over the pure PTMA or LiFePO4 cathode which is very promising for transportation and other high pulse power applications that require long cycle life and lower cost.

  1. Finite Element Analysis of Adaptive-Stiffening and Shape-Control SMA Hybrid Composites

    NASA Technical Reports Server (NTRS)

    Gao, Xiujie; Burton, Deborah; Turner, Travis L.; Brinson, Catherine

    2005-01-01

    Shape memory alloy hybrid composites with adaptive-stiffening or morphing functions are simulated using finite element analysis. The composite structure is a laminated fiber-polymer composite beam with embedded SMA ribbons at various positions with respect to the neutral axis of the beam. Adaptive stiffening or morphing is activated via selective resistance heating of the SMA ribbons or uniform thermal loads on the beam. The thermomechanical behavior of these composites was simulated in ABAQUS using user-defined SMA elements. The examples demonstrate the usefulness of the methods for the design and simulation of SMA hybrid composites. Keywords: shape memory alloys, Nitinol, ABAQUS, finite element analysis, post-buckling control, shape control, deflection control, adaptive stiffening, morphing, constitutive modeling, user element

  2. Properties of glass/carbon fiber reinforced epoxy hybrid polymer composites

    NASA Astrophysics Data System (ADS)

    Patel, R. H.; Sevkani, V. R.; Patel, B. R.; Patel, V. B.

    2016-05-01

    Composite Materials are well known for their tailor-made properties. For the fabrication of composites different types of reinforcements are used for different applications. Sometimes for a particular application, one type of reinforcement may not fulfill the requirements. Therefore, more than one type of reinforcements may be used. Thus, the idea of hybrid composites arises. Hybrid composites are made by joining two or more different reinforcements with suitable matrix system. It helps to improve the properties of composite materials. In the present work glass/carbon fiber reinforcement have been used with a matrix triglycidyl ether of tris(m-hydroxy phenyl) phosphate epoxy resin using amine curing agent. Different physical and mechanical properties of the glass, carbon and glass/carbon fiber reinforced polymeric systems have been found out.

  3. Preliminary burn and impact tests of hybrid polymeric composites. [preventing graphite fiber release

    NASA Technical Reports Server (NTRS)

    Tompkins, S. S.; Brewer, W. D.

    1978-01-01

    Free graphite fibers released into the environment from resin matrix composite components, as a result of fire and/or explosion, pose a potential hazard to electrical equipment. An approach to prevent the fibers from becoming airborne is to use hybrid composite materials which retain the fibers at the burn site. Test results are presented for three hybrid composites that were exposed to a simulation of an aircraft fire and explosion. The hybrid systems consisted of 16 plies of graphite-epoxy with two plies of Kevlar-, S-glass-, or boron-epoxy on each face. Two different test environments were used. In one environment, specimens were heated by convection only, and then impacted by a falling mass. In the other environment, specimens were heated by convection and by radiation, but were not impacted. The convective heat flux was about 100-120 kW/m in both environments and the radiative flux was about 110 kW/sq m.

  4. Effect of energy density on color stability in dental resin composites under accelerated aging.

    PubMed

    Zamarripa, Eliezer; Ancona, Adriana L; D'Accorso, Norma B; Macchi, Ricardo L; Abate, Pablo F

    2008-01-01

    The effects of the energy density that is used for polymerization on properties of dental resin composites are well known. However, few studies relate color stability to this factor. The aim of this study was to assess color changes (deltaE*), in vitro, in terms of accelerated aging under UV exposure of specimens prepared with different energy densities. Four commercial dental resin composites were included in the study. Thirty six specimens were prepared for each one of them, following the procedure established by ISO 4049 Standard, and assigned to three groups: A (3.75 J/cm2), B (9 J/cm2), C (24 J/cm2). Each group was further subdivided into four subgroups: 1 (no aging), 2 (500 hours aging), 3 (1000 hours aging) and 4 (1500 hours aging). The results were analyzed by means of ANOVA and Tukey's test (alpha = 0.05) to determine the effect of the factors. Correlation was performed in order to determine the possible relationship among variables. Energy density is not a significant factor in color stability. However aging is directly proportional to color changes. deltaE* depends on filler size; hybrid material presented deltaE* of 2.1(0.5), 2.4(0.6) and 3.3(0.3) at 500, 1000 and 1500 hours of accelerated aging respectively, and nanofilled material showed deltaE* of 3.0(0.6), 4.5(1.2) and 5.9(0.6) at the same times respectively. It can be concluded that deltaE* does not depend on energy density; however other factors are involved in color change. Further studies in this area are warranted.

  5. On the axial and interfacial shear stresses due to thermal mismatch in hybrid composites

    SciTech Connect

    Rossettos, J.N.; Shen, X.

    1994-12-31

    An analytical model is formulated which attempts to account for the axial and the interfacial shear stresses which can develop in hybrid fiber composites due to the mismatch in coefficients of thermal expansion and Youngs modulus. A finite width hybrid composite monolayer with alternating high modulus and low modulus fibers is considered. To properly account for the interfacial shear between fiber and matrix, a modified shear lag model is used, which permits extensional deformation in the matrix in the fiber direction. Typical stresses due solely to temperature changes are calculated, and show steep boundary layer edge stresses at free corners.

  6. Development of hierarchical magnesium composites using hybrid microwave sintering.

    PubMed

    Habibi, Meisam Kouhi; Joshi, Shailendra P; Gupta, Manoj

    2011-01-01

    In this work, hierarchical magnesium based composites with a micro-architecture comprising reinforcing constituent that is a composite in itself were fabricated using powder metallurgy route including microwave assisted rapid sintering technique and hot extrusion. Different level-I composite particles comprises sub-micron pure aluminum (Al) matrix containing Al2O3 particles of different length scale (from micrometer to nanometer size). Microstructural characterization of the hierarchical composites revealed reasonably uniform distribution of level-I composite particles and significant grain refinement compared to monolithic Mg. Hierarchical composite configurations exhibited different mechanical performance as a function of Al2O3 length scale. Among the different hierarchical formulations synthesized, the hierarchical configuration with level-I composition comprising Al and nano-Al2O3 (0.05 microm) exhibited the highest improvement in tensile yield strength (0.2% YS), ultimate tensile strength (UTS), tensile failure strain (FS), compressive yield strength (0.2% CYS) and ultimate compressive strength (UCS) (+96%, +80%, +42%, +80%, and +83%) as compared to monolithic Mg. An attempt has been made in the present study to correlate the effect of different length scales of Al2O3 particulates on the microstructural and mechanical response of magnesium. PMID:24427874

  7. Mechanical performance of hybrid polyester composites reinforced Cloisite 30B and kenaf fibre

    NASA Astrophysics Data System (ADS)

    Bonnia, N. N.; Surip, S. N.; Ratim, S.; Mahat, M. M.

    2012-06-01

    Hybridization of rubber toughened polyester-kenaf nanocomposite was prepared by adding various percentage of kenaf fiber with 4% Cloisite 30B in unsaturated polyester resin. Composite were prepared by adding filler to modified polyester resin subsequently cross-linked using methyl ethyl ketone peroxide and the accelerator cobalt octanoate 1%. Three per hundred rubbers (phr) of liquid natural rubber (LNR) were added in producing this composite. This composite expected to be applied in the interior of passenger cars and truck cabins. This is a quality local product from a combination of good properties polyester and high performance natural fiber, kenaf that is suitable for many applications such as in automotive sector and construction sector. The mechanical and thermal properties of composite were characterized using Durometer Shore-D hardness test, Izod impact test, Scanning electron microscopy, thermogravimetry (TGA) and differential scanning calorimetry (DSC). Result shows that addition of LNR give good properties on impact, flexural and hardness compare to without LNR composite. DSC curve shows that all composition of composites is fully cured and good in thermal properties. Addition of higher percentage of kenaf will lead the composite to elastic behavior and decrease the toughened properties of the composite. Hybrid system composite showed the flexural properties within the flexural properties of kenaf - polyester and Cloisite 30B.

  8. Mechanical behavior of polyester-based woven jute/glass hybrid composites

    NASA Astrophysics Data System (ADS)

    Ahsan, Q.; Tanju, S.

    2012-06-01

    In polymer composite fabrication system, hybridization of jute fibers with synthetic fibers is one of the techniques adopted to overcome some of the limitations (poor mechanical properties and moisture resistance) that have been identified for jute fiber reinforced composites. In the present study, the effect of hybridization on mechanical properties of jute and glass mat reinforced polyester composites has been evaluated experimentally. The composites were made of glass mat, jute mat and varying layers of jute and glass mat in the polyester matrix by applying hand lay-up technique at room temperature (250C). The values of mechanical properties obtained from tensile, flexural and interlaminar shear strength (ILSS) tests show significant improvement with the increase of glass fiber content in hybrid composites. But the positive contribution from glass mat in increasing of ILSS of composite is limited to some extent and the optimum ILSS is achieved when glass-jute incorporated in composite as 50-50 weight basis. SEM images were used to study the modes of fracture, fiber-matrix adhesion, and jute-glass layer adhesion. The fracture surfaces resulted from different tests clearly show that cracks propagate throughout the polyester matrix by tearing the jute mat and delaminating the glass mat.

  9. Properties of Multifunctional Hybrid Carbon Nanotube/Carbon Fiber Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Cano, Roberto J.; Kang, Jin Ho; Grimsley, Brian W.; Ratcliffe, James G.; Siochi, Emilie J.

    2016-01-01

    For aircraft primary structures, carbon fiber reinforced polymer (CFRP) composites possess many advantages over conventional aluminum alloys due to their light weight, higher strength- and stiffness-to-weight ratios, and low life-cycle maintenance costs. However, the relatively low electrical and thermal conductivities of CFRP composites fail to provide structural safety in certain operational conditions such as lightning strikes. Carbon nanotubes (CNT) offer the potential to enhance the multi-functionality of composites with improved thermal and electrical conductivity. In this study, hybrid CNT/carbon fiber (CF) polymer composites were fabricated by interleaving layers of CNT sheets with Hexcel® IM7/8852 prepreg. Resin concentrations from 1 wt% to 50 wt% were used to infuse the CNT sheets prior to composite fabrication. The interlaminar properties of the resulting hybrid composites were characterized by mode I and II fracture toughness testing. Fractographical analysis was performed to study the effect of resin concentration. In addition, multi-directional physical properties like thermal conductivity of the orthotropic hybrid polymer composite were evaluated.

  10. Sensing and actuating capabilities of a shape memory polymer composite integrated with hybrid filler

    NASA Astrophysics Data System (ADS)

    Lu, Haibao; Yu, Kai; Liu, Yanju; Leng, Jinsong

    2010-06-01

    In this paper, hybrid fillers, including carbon black (CB) and chopped short carbon fibers (SCF), are integrated into a styrene-based shape memory polymer (SMP) with sensing and actuating capabilities. The hybrid filler is expected to transform insulating SMP into conducting. Static mechanical properties of the SMP composites containing various filler concentrations of hybrid filler reinforcement are studied first, and it is theoretically and experimentally confirmed that the mechanical properties are significantly improved by a factor of filler content of SCF. The excellent electrical properties of this novel type of SMP composite are determined by a four-point-probe method. As a consequence, the sensing properties of SMP composite filled with 5 wt% CB and 2 wt% SCF are characterized by functions of temperature and strain. These two experimental results both aid the use of SMP composites as sensors that respond to changes in temperature or mechanical loads. On the other hand, the actuating capability of SMP composites is also validated and demonstrated. The dynamic mechanical analysis result reveals that the output strength of SMP composites is improved with an increase in filler content of SCF. The actuating capability of SMP composites is subsequently demonstrated in a series of photographs.

  11. Syndiotactic Polystyrene/Hybrid Silica Spheres of POSS Siloxane Composites Exhibiting Ultralow Dielectric Constant.

    PubMed

    Joseph, Angel Mary; Nagendra, Baku; Surendran, K P; Gowd, E Bhoje

    2015-09-01

    Homogeneously dispersed hybrid silica/syndiotactic polystyrene composites were investigated for low-κ dielectric applications. The composites were prepared by a solution blending method, and their microstructures were analyzed by SEM, TEM, and AFM. Crystallization and phase transformation behavior of sPS were investigated using differential scanning calorimetry and wide-angle X-ray diffraction. These composites exhibited improved thermal stability and reduced thermal expansion coefficients. Promising dielectric properties were observed for the composites in the microwave frequency region with a dielectric constant (κ = 1.95) and loss (tan δ = 10(-4)) at 5 GHz. PMID:26287385

  12. Stone Composition as a Function of Age and Sex

    PubMed Central

    Rule, Andrew D.; Krambeck, Amy E.; Williams, James C.; Bergstralh, Eric J.; Mehta, Ramila A.; Moyer, Thomas P.

    2014-01-01

    Background and objectives Kidney stones are heterogeneous but often grouped together. The potential effects of patient demographics and calendar month (season) on stone composition are not widely appreciated. Design, setting, participants, & measurements The first stone submitted by patients for analysis to the Mayo Clinic Metals Laboratory during 2010 was studied (n=43,545). Stones were classified in the following order: any struvite, any cystine, any uric acid, any brushite, majority (≥50%) calcium oxalate, or majority (≥50%) hydroxyapatite. Results Calcium oxalate (67%) was the most common followed by hydroxyapatite (16%), uric acid (8%), struvite (3%), brushite (0.9%), and cystine (0.35%). Men accounted for more stone submissions (58%) than women. However, women submitted more stones than men between the ages of 10–19 (63%) and 20–29 (62%) years. Women submitted the majority of hydroxyapatite (65%) and struvite (65%) stones, whereas men submitted the majority of calcium oxalate (64%) and uric acid (72%) stones (P<0.001). Although calcium oxalate stones were the most common type of stone overall, hydroxyapatite stones were the second most common before age 55 years, whereas uric acid stones were the second most common after age 55 years. More calcium oxalate and uric acid stones were submitted in the summer months (July and August; P<0.001), whereas the season did not influence other stone types. Conclusions It is well known that calcium oxalate stones are the most common stone type. However, age and sex have a marked influence on the type of stone formed. The higher number of stones submitted by women compared with men between the ages of 10 and 29 years old and the change in composition among the elderly favoring uric acid have not been widely appreciated. These data also suggest increases in stone risk during the summer, although this is restricted to calcium oxalate and uric acid stones. PMID:25278549

  13. Effect of fiber loading on flexural strength of hybrid sisal/hemp-HDPE composites

    NASA Astrophysics Data System (ADS)

    Aggarwal, Lakshya; Sinha, Shishir; Gupta, V. K.

    2015-05-01

    The continuing demand for sustainable materials and increasing environmental concerns have led to intense research in the field of natural fiber reinforced composites. Natural fibers are favored over synthetic fibers as reinforcement due to positive environmental benefits such as raw material utilization at source and easy disposable of the biodegradable fiber. In the present work, we have investigated flexural behavior of hybrid natural fiber reinforced HDPE composites. The matrix comprises of 50-50 ratio of virgin and recycled HDPE and the content of fibers (sisal and hemp) in the composite is varied from 10 to 30%. The natural fibers were mercerized with NaOH solution and chemically treated with maleic anhydride. The flexural specimens were prepared by injection moulding process and the testing was conducted in accordance to ASTM D790 standards. It is revealed that the flexural strength of the hybrid composite increases with the increase in fibers content when compared to specimen containing 100% HDPE.

  14. Aptamer-gelatin composite for a trigger release system mediated by oligonucleotide hybridization.

    PubMed

    Soontornworajit, Boonchoy; Srakaew, Prangkamol; Naramitpanich, Pajaree

    2014-01-01

    Nucleic acid aptamers not only specifically bind to their target proteins with high affinity but also form intermolecular hybridization with their complementary oligonucleotides (CO). The hybridization can interrupt aptamer/protein interaction due to the changes of aptamer secondary structure which rely on hybridization length and base-pairing positions. Herein we aim to use this unique property of the aptamers, when combined with gelatin to develop a novel composite with desirable protein release profiles. Platelet-derived growth factor-BB (PDGF-BB) and its aptamer were used as target molecules. Prior to performing the release study, the effects of CO on aptamer-protein interaction were observed by surface plasmon resonance (SPR). The SPR sensorgram indicated that the aptamer dissociated from the bounded proteins when it hybridized with the CO. The aptamer was then immobilized onto streptavidin coated polystyrene particles via biotin/streptavidin interaction. Then, PDGF-BB and aptamer functionalized particles were mixed with gelatin solution and cast as small pieces of composite. The success of the composite preparation was confirmed by flow cytometry and microscopy. PDGF-BB release at several time points was quantified by ELISA. The results showed that the aptamer-gelatin composite could slow the release rate of the proteins from the composite due to strong binding of proteins and aptamers. Once the CO was added to the system, the release rate was significantly enhanced because the aptamer hybridized with the CO and lost its active secondary structure. Therefore, the proteins were triggered to release out from the composite. This work suggests a promising strategy for controlling the release of bioactive molecules in medical treatments.

  15. Learning science in small multi-age groups: the role of age composition

    NASA Astrophysics Data System (ADS)

    Kallery, Maria; Loupidou, Thomais

    2016-06-01

    The present study examines how the overall cognitive achievements in science of the younger children in a class where the students work in small multi-age groups are influenced by the number of older children in the groups. The context of the study was early-years education. The study has two parts: The first part involved classes attended by pre-primary children aged 4-6. The second part included one primary class attended by students aged 6-8 in addition to the pre-primary classes. Students were involved in inquiry-based science activities. Two sources of data were used: Lesson recordings and children's assessments. The data from both sources were separately analyzed and the findings plotted. The resulting graphs indicate a linear relationship between the overall performance of the younger children in a class and the number of older ones participating in the groups in each class. It seems that the age composition of the groups can significantly affect the overall cognitive achievements of the younger children and preferentially determines the time within which this factor reaches its maximum value. The findings can be utilized in deciding the age composition of small groups in a class with the aim of facilitating the younger children's learning in science.

  16. Computational Thermomechanical Modelling of Early-Age Silicate Composites

    NASA Astrophysics Data System (ADS)

    Vala, J.; Št'astník, S.; Kozák, V.

    2009-09-01

    Strains and stresses in early-age silicate composites, widely used in civil engineering, especially in fresh concrete mixtures, in addition to those caused by exterior mechanical loads, are results of complicated non-deterministic physical and chemical processes. Their numerical prediction at the macro-scale level requires the non-trivial physical analysis based on the thermodynamic principles, making use of micro-structural information from both theoretical and experimental research. The paper introduces a computational model, based on a nonlinear system of macroscopic equations of evolution, supplied with certain effective material characteristics, coming from the micro-scale analysis, and sketches the algorithm for its numerical analysis.

  17. Thermally conductive polyamide 6/carbon filler composites based on a hybrid filler system

    NASA Astrophysics Data System (ADS)

    Ha, Sung Min; Kwon, O. Hwan; Gyeong Oh, Yu; Kim, Yong Seok; Lee, Sung-Goo; Won, Jong Chan; Cho, Kwang Soo; Gak Kim, Byoung; Yoo, Youngjae

    2015-12-01

    We explored the use of a hybrid filler consisting of graphite nanoplatelets (GNPs) and single walled carbon nanotubes (SWCNTs) in a polyamide 6 (PA 6) matrix. The composites containing PA 6, powdered GNP, and SWCNT were melt-processed and the effect of filler content in the single filler and hybrid filler systems on the thermal conductivity of the composites was examined. The thermal diffusivities of the composites were measured by the standard laser flash method. Composites containing the hybrid filler system showed enhanced thermal conductivity with values as high as 8.8 W (m · K)-1, which is a 35-fold increase compared to the thermal conductivity of pure PA 6. Thermographic images of heat conduction and heat release behaviors were consistent with the thermal conductivity results, and showed rapid temperature jumps and drops, respectively, for the composites. A composite model based on the Lewis-Nielsen theory was developed to treat GNP and SWCNT as two separate types of fillers. Two approaches, the additive and multiplicative approaches, give rather good quantitative agreement between the predicted values of thermal conductivity and those measured experimentally.

  18. Kenaf-glass fiber reinforced unsaturated polyester hybrid composites: Tensile properties

    NASA Astrophysics Data System (ADS)

    Zhafer, S. F.; Rozyanty, A. R.; Shahnaz, S. B. S.; Musa, L.; Zuliahani, A.

    2016-07-01

    The use of natural fibers in composite is rising in recent years due their lightweight, non-abrasive, combustible, non-toxic, low cost and biodegradable properties. However, in comparison with synthetic fibers, the mechanical properties of natural fibers are lower. Therefore, the inclusion of synthetic fibers could improve the mechanical performance of natural fiber based composites. In this study, kenaf bast fiber and glass fiber at different weight percentage loading were used as reinforcement to produce hybrid composites. Unsaturated polyester (UP) resin was used as matrix and hand lay-up process was performed to apply the UP resin on the hybrid kenaf bast/glass fiber composite. Effect of different fiber loading on tensile strength, tensile modulus and elongation at break of the hybrid composite was studied. It has been found that the highest value of tensile strength and modulus was achieved at 10 wt.% kenaf/10 wt.% glass fiber loading. It was concluded that addition of glass fiber has improved the tensile properties of kenaf bast fiber based UP composites.

  19. Hybrid visibility compositing and masking for illustrative rendering☆

    PubMed Central

    Bruckner, Stefan; Rautek, Peter; Viola, Ivan; Roberts, Mike; Sousa, Mario Costa; Gröller, M. Eduard

    2010-01-01

    In this paper, we introduce a novel framework for the compositing of interactively rendered 3D layers tailored to the needs of scientific illustration. Currently, traditional scientific illustrations are produced in a series of composition stages, combining different pictorial elements using 2D digital layering. Our approach extends the layer metaphor into 3D without giving up the advantages of 2D methods. The new compositing approach allows for effects such as selective transparency, occlusion overrides, and soft depth buffering. Furthermore, we show how common manipulation techniques such as masking can be integrated into this concept. These tools behave just like in 2D, but their influence extends beyond a single viewpoint. Since the presented approach makes no assumptions about the underlying rendering algorithms, layers can be generated based on polygonal geometry, volumetric data, point-based representations, or others. Our implementation exploits current graphics hardware and permits real-time interaction and rendering. PMID:20862189

  20. Hybrid composite based on poly(vinyl alcohol) and fillers from renewable resources

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hybrid composite laminates consisting of polyvinyl alcohol (PVA) as continuous phase (33% by weight) and lignocellulosic fillers, derived from sugarcane bagasse, apple and orange waste (22% by weight) were molded in a carver press in the presence of water and glycerol such as platicizers agents. Cor...

  1. Hybrid composite based on poly(vinyl alcohol) and fillers from renewable resources

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hybrid composite laminates consisting of polyvinyl alcohol (PVA) as continuous phase and lignocellulosic fibres, derived from sugarcane bagasse, apple and orange waste were moulded in a carver press in the presence of water and glycerol such as platicizers agents. Corn starch was introduced as a bio...

  2. Enhanced dielectric performance in polymer composite films with carbon nanotube-reduced graphene oxide hybrid filler.

    PubMed

    Kim, Jin-Young; Kim, TaeYoung; Suk, Ji Won; Chou, Harry; Jang, Ji-Hoon; Lee, Jong Ho; Kholmanov, Iskandar N; Akinwande, Deji; Ruoff, Rodney S

    2014-08-27

    The electrical conductivity and the specific surface area of conductive fillers in conductor-insulator composite films can drastically improve the dielectric performance of those films through changing their polarization density by interfacial polarization. We have made a polymer composite film with a hybrid conductive filler material made of carbon nanotubes grown onto reduced graphene oxide platelets (rG-O/CNT). We report the effect of the rG-O/CNT hybrid filler on the dielectric performance of the composite film. The composite film had a dielectric constant of 32 with a dielectric loss of 0.051 at 0.062 wt% rG-O/CNT filler and 100 Hz, while the neat polymer film gave a dielectric constant of 15 with a dielectric loss of 0.036. This is attributed to the increased electrical conductivity and specific surface area of the rG-O/CNT hybrid filler, which results in an increase in interfacial polarization density between the hybrid filler and the polymer.

  3. Identifying anticancer peptides by using improved hybrid compositions

    PubMed Central

    Li, Feng-Min; Wang, Xiao-Qian

    2016-01-01

    Cancer is one of the main causes of threats to human life. Identification of anticancer peptides is important for developing effective anticancer drugs. In this paper, we developed an improved predictor to identify the anticancer peptides. The amino acid composition (AAC), the average chemical shifts (acACS) and the reduced amino acid composition (RAAC) were selected to predict the anticancer peptides by using the support vector machine (SVM). The overall prediction accuracy reaches to 93.61% in jackknife test. The results indicated that the combined parameter was helpful to the prediction for anticancer peptides. PMID:27670968

  4. A NEW VIEW OF VEGA'S COMPOSITION, MASS, AND AGE

    SciTech Connect

    Yoon, Jinmi; Peterson, Deane M.; Kurucz, Robert L.; Zagarello, Robert J. E-mail: dpeterson@astro.sunysb.ed E-mail: rzagarello@mail.astro.sunysb.ed

    2010-01-01

    We present estimates of Vega's composition, mass, and age based on a simultaneous fit of high-resolution metal line profiles, the wings of the Balmer lines, the absolute visible/near-IR fluxes, and high angular resolution triple phase data from the Navy Prototype Optical Interferometer to gravity-darkened Roche models. This substantially expands our earlier analysis. We determine that Vega has a much lower mass, 2.135 +- 0.074 M{sub sun}, than generally assumed. This strongly supports the contention that Vega is metal-poor throughout (Z approx 0.008), suggesting it was formed that way. Assuming a uniform composition equal to that derived for the surface, and the luminosity and radius obtained here, we derive a best estimate of Vega's age, 455 +- 13 Myr, and mass, 2.157 +- 0.017 M{sub sun}, by fitting to standard isochrones. We continue to argue that Vega is much too old to be coeval with other members of the Castor moving group and is thus unlikely to be a member. The updated chemical abundances continue to support the conclusion that Vega is a lambda Boo star.

  5. Effects of resin formulation and nanofiller surface treatment on the properties of experimental hybrid resin composite.

    PubMed

    Musanje, Lawrence; Ferracane, Jack L

    2004-08-01

    This study evaluated the effects of nanofiller surface treatment and resin viscosity on the early and long-term properties of experimental hybrid composites. Three resin formulations (low, medium and high viscosity) were prepared by varying the ratio of TEGDMA:UDMA:bis-GMA (47:33:16 wt%; 30:33:33 wt%; 12:33:51 wt%). Composites contained 71.3 wt% silanated strontium glass (1-3 microm) and 12.6 wt% of either silanated or unsilanated silica (OX-50; 0.04 microm). Specimens (n=10) for flexural strength, flexural modulus, fracture toughness and Knoop hardness were tested after 24 h, 1 and 6 months exposure to water at 37 degrees C. Degree of conversion (DC) was determined 24 h after photoinitiation using FTIR. Resin viscosity only had a marginal influence on the mechanical response of composites but it can be adjusted to achieve a balance between DC and mechanical properties. Adding non-bonded nanofiller to hybrid composites had no systematic effect on DC. Non-bonded nanofillers had no significant effect on the long-term properties of hybrid composites. PMID:15046897

  6. Three-dimensional hybrid-stress finite element analysis of composite laminates with cracks and cutouts

    NASA Technical Reports Server (NTRS)

    Wang, S. S.

    1985-01-01

    A three-dimensional hybrid-stress finite element analysis of composite laminates containing cutouts and cracks is presented. Fully three-dimensional, hexahedral isoparametric elements of the hybrid-stress model are formulated on the basis of the Hellinger-Reissner variational principle. Traction-free edges, cutouts, and crack surfaces are modeled by imposition of exact traction boundary conditions along element surfaces. Special boundary and surface elements are constructed by introducing proper constraints on assumed stress functions. The Lagrangian multiplier technique is used to enforce ply-interface continuity conditions in hybrid bimaterial composite elements for modeling the interface region in a composite laminate. Two examples are given to illustrate the capability of the present method of approach: (1) the well-known delamination problem in an angle-ply laminate, and (2) the important problem of a composite laminate containing a circular hole. Results are presented in detail for each case. Implications of interlaminar and intralaminar crack initiation, growth and fracture in composites containing cracks and cutouts are discussed.

  7. Color stability of repaired composite submitted to accelerated artificial aging.

    PubMed

    Souza, Ana Beatriz Silva; Silame, Francisca Daniele Jardilino; Alandia-Roman, Carla Cecilia; Cruvinel, Diogo Rodrigues; Garcia, Lucas da Fonseca Roberti; Pires-de-Souza, Fernanda de Carvalho Panzeri

    2012-01-01

    The aim of this study was to evaluate the color stability (ΔE) of nanoparticulate composite, with consideration for the type of surface treatment performed before repair. A Teflon matrix was used to fabricate 50 test specimens from composite. After initial color readout, the specimens were submitted to 100 hours of accelerated artificial aging (AAA). The samples were divided into five groups (n = 10), according to the surface treatment performed: sandblasting with aluminum oxide powder, phosphoric acid, and an adhesive system (Group 1); sandblasting with aluminum oxide powder, phosphoric acid, and a flowable composite (Group 2); abrasion with a diamond bur, phosphoric acid, and an adhesive system (Group 3); abrasion with a diamond bur, phosphoric acid, and a nanoparticulate composite (Group 4); and a control group (Group 5). After repair, a new color readout was taken, the test specimens were submitted to a new AAA cycle (300 hours), and the final color readout was taken. Comparison of the ΔE means (one-way ANOVA and Tukey tests, p < 0.05) demonstrated no statistically significant differences among the groups (p > 0.05) after 100 hours of AAA. After repair, Group 1 (4.61 ± 2.03) presented the highest color alteration with a statistically significant difference compared with the other groups (p < 0.05). After 300 hours, Group 4 specimens (13.84 ± 0.71) presented the lowest color alteration in comparison with the other groups, with a statistically significant difference (p < 0.05). It was concluded that the repair performed in Group 4 provided greater esthetic recovery, made possible by the regression in the ΔE values of the restorations after repair, and less color alteration of the restorations over the course of time. PMID:23032241

  8. Behaviour of hybrid jute-glass/epoxy composite tubes subjected to lateral loading

    NASA Astrophysics Data System (ADS)

    Khalid, A. A.

    2015-12-01

    Experimental work on hybrid and non-hybrid composite tubes subjected to lateral loading has been carried out using jute, glass and hybrid jute-glass/epoxy materials. Tubes of 200 mm length with 110 mm inner diameter were fabricated by hand lay-up method to investigate the effect of material used and the number of layers on lateral-load-displacement relations and on the failure mode. Crush force efficiency and the specific energy absorption of the composite tubes were calculated. Results show that the six layers glass/epoxy tubes supported load higher 10.6% than that of hybrid jute-glass/ epoxy made of two layers of jute/epoxy four layers of glass/epoxy. It has been found that the specific energy absorption of the glass/epoxy tubes is found higher respectively 11.6% and 46% than hybrid jute-glass/epoxy and jute/epoxy tubes. The increase in the number of layers from two to six increases the maximum lateral load from 0.53KN to 1.22 KN for jute/epoxy and from 1.35 KN to 3.87 KN for the glass/epoxy tubes. The stacking sequence of the hybrid tubes influenced on the maximum lateral load and the absorbed energy. The maximum load obtained for the six layers jute-glass/epoxy tubes of different staking sequence varies between 1.88 KN to 3.46 KN. Failure mechanisms of the laterally loaded composite tubes were also observed and discussed.

  9. Hybrid local FEM/global LISA modeling of damped guided wave propagation in complex composite structures

    NASA Astrophysics Data System (ADS)

    Shen, Yanfeng; Cesnik, Carlos E. S.

    2016-09-01

    This paper presents a new hybrid modeling technique for the efficient simulation of guided wave generation, propagation, and interaction with damage in complex composite structures. A local finite element model is deployed to capture the piezoelectric effects and actuation dynamics of the transmitter, while the global domain wave propagation and interaction with structural complexity (structure features and damage) are solved utilizing a local interaction simulation approach (LISA). This hybrid approach allows the accurate modeling of the local dynamics of the transducers and keeping the LISA formulation in an explicit format, which facilitates its readiness for parallel computing. The global LISA framework was extended through the 3D Kelvin-Voigt viscoelasticity theory to include anisotropic damping effects for composite structures, as an improvement over the existing LISA formulation. The global LISA framework was implemented using the compute unified device architecture running on graphic processing units. A commercial preprocessor is integrated seamlessly with the computational framework for grid generation and material property allocation to handle complex structures. The excitability and damping effects are successfully captured by this hybrid model, with experimental validation using the scanning laser doppler vibrometry. To demonstrate the capability of our hybrid approach for complex structures, guided wave propagation and interaction with a delamination in a composite panel with stiffeners is presented.

  10. Hybrid local FEM/global LISA modeling of damped guided wave propagation in complex composite structures

    NASA Astrophysics Data System (ADS)

    Shen, Yanfeng; Cesnik, Carlos E. S.

    2016-09-01

    This paper presents a new hybrid modeling technique for the efficient simulation of guided wave generation, propagation, and interaction with damage in complex composite structures. A local finite element model is deployed to capture the piezoelectric effects and actuation dynamics of the transmitter, while the global domain wave propagation and interaction with structural complexity (structure features and damage) are solved utilizing a local interaction simulation approach (LISA). This hybrid approach allows the accurate modeling of the local dynamics of the transducers and keeping the LISA formulation in an explicit format, which facilitates its readiness for parallel computing. The global LISA framework was extended through the 3D Kelvin–Voigt viscoelasticity theory to include anisotropic damping effects for composite structures, as an improvement over the existing LISA formulation. The global LISA framework was implemented using the compute unified device architecture running on graphic processing units. A commercial preprocessor is integrated seamlessly with the computational framework for grid generation and material property allocation to handle complex structures. The excitability and damping effects are successfully captured by this hybrid model, with experimental validation using the scanning laser doppler vibrometry. To demonstrate the capability of our hybrid approach for complex structures, guided wave propagation and interaction with a delamination in a composite panel with stiffeners is presented.

  11. Synthesis and characterization of hybrid silica/PMMA nanoparticles and their use as filler in dental composites.

    PubMed

    Canché-Escamilla, G; Duarte-Aranda, S; Toledano, M

    2014-09-01

    The effect of hybrid silica/poly(methylmethacrylate) (PMMA) nanoparticles on the properties of composites for dental restoration was evaluated. Hybrid nanoparticles with silica as core and PMMA as shell were obtained by a seeded emulsion polymerization process. Fourier transform infrared spectrum of the hybrid nanoparticles shows an intense peak at 1,730 cm(-1), corresponding to carbonyl groups (CO) of the ester. The thermal stability of the hybrid particles decreases with increasing amounts of PMMA and the residual mass at 700°C corresponds to the silica content in the hybrid particles. Composites were obtained by dispersing nanoparticles (silica or hybrid), as fillers, in a resin-bis glycidyl dimethacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) (40%/60% (w/w)). The paste was then placed in a mold and polymerized under light irradiation. During the preparation of the composites, with the hybrid nanoparticles, the monomers swell the PMMA shell and after photo-curing, a semi-interpenetrating network (semi-IPN) is obtained around the silica core. The properties of the composites, obtained using the hybrid nanoparticles, depend on the filler content and the amount of PMMA in the semi-IPN matrix. For composites with similar inorganic filler contents, the composites with low amounts of PMMA shell had higher modulus than those in which silica was used as the filler.

  12. Impact Strength and Flexural Properties Enhancement of Methacrylate Silane Treated Oil Palm Mesocarp Fiber Reinforced Biodegradable Hybrid Composites

    PubMed Central

    Ibrahim, Nor Azowa; Ariffin, Hidayah; Yunus, Wan Md. Zin Wan

    2014-01-01

    Natural fiber as reinforcement filler in polymer composites is an attractive approach due to being fully biodegradable and cheap. However, incompatibility between hydrophilic natural fiber and hydrophobic polymer matrix restricts the application. The current studies focus on the effects of incorporation of silane treated OPMF into polylactic acid (PLA)/polycaprolactone (PCL)/nanoclay/OPMF hybrid composites. The composites were prepared by melt blending technique and characterize the composites with Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). FTIR spectra indicated that peak shifting occurs when silane treated OPMF was incorporated into hybrid composites. Based on mechanical properties results, incorporation of silane treated OPMF enhances the mechanical properties of unmodified OPMF hybrid composites with the enhancement of flexural and impact strength being 17.60% and 48.43%, respectively, at 10% fiber loading. TGA thermogram shows that incorporation of silane treated OPMF did not show increment in thermal properties of hybrid composites. SEM micrographs revealed that silane treated OPMF hybrid composites show good fiber/matrix adhesion as fiber is still embedded in the matrix and no cavity is present on the surface. Water absorption test shows that addition of less hydrophilic silane treated OPMF successfully reduces the water uptake of hybrid composites. PMID:25254230

  13. Impact strength and flexural properties enhancement of methacrylate silane treated oil palm mesocarp fiber reinforced biodegradable hybrid composites.

    PubMed

    Eng, Chern Chiet; Ibrahim, Nor Azowa; Zainuddin, Norhazlin; Ariffin, Hidayah; Yunus, Wan Md Zin Wan

    2014-01-01

    Natural fiber as reinforcement filler in polymer composites is an attractive approach due to being fully biodegradable and cheap. However, incompatibility between hydrophilic natural fiber and hydrophobic polymer matrix restricts the application. The current studies focus on the effects of incorporation of silane treated OPMF into polylactic acid (PLA)/polycaprolactone (PCL)/nanoclay/OPMF hybrid composites. The composites were prepared by melt blending technique and characterize the composites with Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). FTIR spectra indicated that peak shifting occurs when silane treated OPMF was incorporated into hybrid composites. Based on mechanical properties results, incorporation of silane treated OPMF enhances the mechanical properties of unmodified OPMF hybrid composites with the enhancement of flexural and impact strength being 17.60% and 48.43%, respectively, at 10% fiber loading. TGA thermogram shows that incorporation of silane treated OPMF did not show increment in thermal properties of hybrid composites. SEM micrographs revealed that silane treated OPMF hybrid composites show good fiber/matrix adhesion as fiber is still embedded in the matrix and no cavity is present on the surface. Water absorption test shows that addition of less hydrophilic silane treated OPMF successfully reduces the water uptake of hybrid composites. PMID:25254230

  14. Impact strength and flexural properties enhancement of methacrylate silane treated oil palm mesocarp fiber reinforced biodegradable hybrid composites.

    PubMed

    Eng, Chern Chiet; Ibrahim, Nor Azowa; Zainuddin, Norhazlin; Ariffin, Hidayah; Yunus, Wan Md Zin Wan

    2014-01-01

    Natural fiber as reinforcement filler in polymer composites is an attractive approach due to being fully biodegradable and cheap. However, incompatibility between hydrophilic natural fiber and hydrophobic polymer matrix restricts the application. The current studies focus on the effects of incorporation of silane treated OPMF into polylactic acid (PLA)/polycaprolactone (PCL)/nanoclay/OPMF hybrid composites. The composites were prepared by melt blending technique and characterize the composites with Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). FTIR spectra indicated that peak shifting occurs when silane treated OPMF was incorporated into hybrid composites. Based on mechanical properties results, incorporation of silane treated OPMF enhances the mechanical properties of unmodified OPMF hybrid composites with the enhancement of flexural and impact strength being 17.60% and 48.43%, respectively, at 10% fiber loading. TGA thermogram shows that incorporation of silane treated OPMF did not show increment in thermal properties of hybrid composites. SEM micrographs revealed that silane treated OPMF hybrid composites show good fiber/matrix adhesion as fiber is still embedded in the matrix and no cavity is present on the surface. Water absorption test shows that addition of less hydrophilic silane treated OPMF successfully reduces the water uptake of hybrid composites.

  15. Optical properties of supra-nano spherical filled resin composites compared to nanofilled, nano-hybrid and micro-hybrid composites.

    PubMed

    Perez, María M; Hita-Iglesias, Cristina; Ghinea, Razvan; Yebra, Ana; Pecho, Oscar E; Ionescu, Ana M; Crespo, Almudena; Hita, Enrique

    2016-01-01

    This study aimed to evaluate and compare the optical properties of supra-nano spherical filled resin composites and the nanofilled, nano-hybrid and microhybrid composites using the Kubelka-Munk Theory. Diffuse reflectance of samples (Shade A2) was measured against white and black backgrounds, using a spectroradiometer, using a viewing booth with D65 illuminant and d/0º geometry. S and K coefficients and T were calculated using Kubelka-Munk's equations. The spectral behavior of S, K and T was similar for all dental resin composites analyzed (VAF close to 100%), even though they were, generally, statistically different (p≤0.05). The K-M T values overestimate the real value of Transmittance of the resin composites. Supra-nano spherical filled resin composites show the highest scattering and Transmittance when compared with the others materials, probably due to the shape and size of the filler. Such difference should be taken into consideration in a clinical situation to reproduce natural esthetic restorations.

  16. Studies on Effective Elastic Properties of CNT/Nano-Clay Reinforced Polymer Hybrid Composite

    NASA Astrophysics Data System (ADS)

    Thakur, Arvind Kumar; Kumar, Puneet; Srinivas, J.

    2016-02-01

    This paper presents a computational approach to predict elastic propertiesof hybrid nanocomposite material prepared by adding nano-clayplatelets to conventional CNT-reinforced epoxy system. In comparison to polymers alone/single-fiber reinforced polymers, if an additional fiber is added to the composite structure, it was found a drastic improvement in resultant properties. In this regard, effective elastic moduli of a hybrid nano composite are determined by using finite element (FE) model with square representative volume element (RVE). Continuum mechanics based homogenization of the nano-filler reinforced composite is considered for evaluating the volumetric average of the stresses and the strains under different periodic boundary conditions.A three phase Halpin-Tsai approach is selected to obtain the analytical result based on micromechanical modeling. The effect of the volume fractions of CNTs and nano-clay platelets on the mechanical behavior is studied. Two different RVEs of nano-clay platelets were used to investigate the influence of nano-filler geometry on composite properties. The combination of high aspect ratio of CNTs and larger surface area of clay platelets contribute to the stiffening effect of the hybrid samples. Results of analysis are validated with Halpin-Tsai empirical formulae.

  17. Effect of different bleaching regimens on the flexural strength of hybrid composite resin

    PubMed Central

    Feiz, Atiyeh; Samanian, Noushmehr; Davoudi, Amin; Badrian, Hamid

    2016-01-01

    Background: The entire effects of different bleaching regimens on the mechanical properties of composite resins have remained unknown. The purpose of this study was to evaluate the effects of different bleaching regimens on the flexural strength (FS) of hybrid composite resins. Materials and Methods: In this in vitro study, 80 bar-shaped specimens of hybrid composite resins were fabricated and randomly divided into four groups, 20 specimens in each group. First group (C) was considered as control. The other groups were treated by home bleaching (HB) agent, in-office bleaching (IB) agent, and the combination regimens (HIB), respectively. The FS was evaluated by three-point bending test by using a Universal Testing Machine. All data were analyzed by using Statistical Package for the Social Sciences (SPSS) software version 18, analysis of variance (ANOVA), and Turkey's post hoc statistical tests (α = 0.05). Results: The maximum mean value of FS was seen in HB group with significant differences to other groups (P < 0.05). Also, the minimum FS was observed in group HIB. Conclusion: Application of different bleaching regimens does not have any adverse effect on the FS of hybrid composite resins. However, the administration of HB regimens seemed to have lesser negative impact on the FS. PMID:27099423

  18. Tribological performance of Graphene/Carbon nanotube hybrid reinforced Al2O3 composites

    PubMed Central

    Yazdani, Bahareh; Xu, Fang; Ahmad, Iftikhar; Hou, Xianghui; Xia, Yongde; Zhu, Yanqiu

    2015-01-01

    Tribological performance of the hot-pressed pure Al2O3 and its composites containing various hybrid contents of graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs) were investigated under different loading conditions using the ball-on-disc method. Benchmarked against the pure Al2O3, the composite reinforced with a 0.5 wt% GNP exhibited a 23% reduction in the friction coefficient along with a promising 70% wear rate reduction, and a hybrid reinforcement consisting of 0.3 wt.% GNPs + 1 wt.% CNTs resulted in even better performance, with a 86% reduction in the wear rate. The extent of damage to the reinforcement phases caused during wear was studied using Raman spectroscopy. The wear mechanisms for the composites were analysed based on the mechanical properties, brittleness index and microstructural characterizations. The excellent coordination between GNPs and CNTs contributed to the excellent wear resistance property in the hybrid GNT-reinforced composites. GNPs played the important role in the formation of a tribofilm on the worn surface by exfoliation; whereas CNTs contributed to the improvement in fracture toughness and prevented the grains from being pulled out during the tribological test. PMID:26100097

  19. Edge crack growth of thermally aged graphite/polyimide composites

    NASA Technical Reports Server (NTRS)

    Nelson, J. B.

    1984-01-01

    Laminates of Celion 6000/LARC-160 and Celion 6000/PMR-15 graphite/polyimide composite materials were aged in air at temperatures of 202, 232, 260 and 288 C for various times up to 15,000 hours. Three unidirectional specimen types were studied: short beam shear (SBS), flexure, and 153 mm square panels. The interior region of the square panels exhibited little or no property degradation, whereas both laminate materials degraded and cracked preferentially at the specimen edge perpendicular to the fibers. Using a dye penetrant, the specimens were X-rayed and the crack depth measured as a function of time and temperature. A time temperature superposition of the crack data was successfully performed using an Arrhenius form for the shift factor. A direct correlation was found for edge crack depth and SBS strength for the LARC-160 laminates but the correlation for PMR-15 laminates was more complex.

  20. Alteration of lunar optical properties: age and composition effects.

    PubMed

    Adams, J B; McCord, T B

    1971-02-12

    A model for lunar surface processes is presented which explains the main albedo and color contrasts and the temporal changes in these optical properties. Evidence from Apollo 11 and Apollo 12 samples and telescopic spectral reflectivity measurements indicates that the maria are similar in mineralogy on a regional scale and that the highlands are consistent with an anorthositic-gabbro composition. Bright craters and rays in both regions expose materials that are relatively crystalline compared with their backgrounds, which are richer in dark glass. With age, bright craters and rays in the maria darken in place by meteorite impact-induced vitrification and mixing with the surrounding material. Highland bright craters and rays may, however, darken primarily through regional contamination by iron- and titanium-rich mare material.

  1. Alteration of lunar optical properties: age and composition effects.

    PubMed

    Adams, J B; McCord, T B

    1971-02-12

    A model for lunar surface processes is presented which explains the main albedo and color contrasts and the temporal changes in these optical properties. Evidence from Apollo 11 and Apollo 12 samples and telescopic spectral reflectivity measurements indicates that the maria are similar in mineralogy on a regional scale and that the highlands are consistent with an anorthositic-gabbro composition. Bright craters and rays in both regions expose materials that are relatively crystalline compared with their backgrounds, which are richer in dark glass. With age, bright craters and rays in the maria darken in place by meteorite impact-induced vitrification and mixing with the surrounding material. Highland bright craters and rays may, however, darken primarily through regional contamination by iron- and titanium-rich mare material. PMID:17734782

  2. Charge transport in hybrid nanorod-polymer composite photovoltaiccells

    SciTech Connect

    Huynh, Wendy U.; Dittmer, Janke J.; Teclemariam, Nerayo; Milliron, Delia; Alivisatos, A. Paul; Barnham, Keith W.J.

    2002-06-21

    Charge transport in composites of inorganic nanorods and aconjugated polymer is investigated using a photovoltaic device structure.We show that the current-voltage (I-V) curves in the dark can be modelledusing the Shockley equation modified to include series and shuntresistance at low current levels, and using an improved model thatincorporates both the Shockley equation and the presence of a spacecharge limited region at high currents. Under illumination, theefficiency of photocurrent generation is found to be dependent on appliedbias. Furthermore, the photocurrent-light intensity dependence was foundto be sublinear. An analysis of the shunt resistance as a function oflight intensity suggests that the photocurrent as well as the fill factoris diminished as a result of increased photoconductivity of the activelayer at high light intensity. By studying the intensity dependence ofthe open circuit voltage for nanocrystals with different diameters andthus ! band gaps, it was inferred that Fermi-level pinning occurs at theinterface between the aluminum electrode and the nanocrystal.

  3. In vivo animal models of body composition in aging

    SciTech Connect

    Yasumura, S. |; Jones, K.; Spanne, P.; Schidlovsky, G.; Wielopolski, L.; Ren, X.; Glaros, D.; Xatzikonstantinou, Y. |

    1992-12-31

    We developed several techniques that provide data on body elemental composition from in vivo measurements in rats. These methods include total body potassium by whole-body counting of endogenous {sup 40}K; total body calcium (TBCa), sodium and chloride by in vivo neutron activation analysis and total body phosphorus (TBP) and nitrogen (TBN) by photon activation analysis. These elements provide information on total body fat, total body protein and skeletal mass. Measurements were made in 6-, 12- and 24-month-old rats. TBN Increased slightly between 6 and 12 months but was significantly lower by 24 months, indicating a substantial loss in total body protein. Working at the National Synchrotron light Source, we studied rat femurs by computed microtomography (CMT), and the elemental profile of the femur cortex by synchrotron-radiation induced X-ray emission (SRIXE). Although there were no significant changes in TBCA and TBP, indices of skeletal mass, CMT revealed a marked increase in the size and number of cavities in the endosteal region of the femur cortex with increasing age. The SRIXE analysis of this cortical bone revealed a parallel decrease in the endosteal Ca/P ratio. Thus, there are major alterations in bone morphology and regional elemental composition despite only modest changes in total skeletal mass.

  4. Dry Process for Manufacturing Hybridized Boron Fiber/Carbon Fiber Thermoplastic Composite Materials from a Solution Coated Precursor

    NASA Technical Reports Server (NTRS)

    Belvin, Harry L. (Inventor); Cano, Roberto J. (Inventor)

    2003-01-01

    An apparatus for producing a hybrid boron reinforced polymer matrix composite from precursor tape and a linear array of boron fibers. The boron fibers are applied onto the precursor tapes and the precursor tape processed within a processing component having an impregnation bar assembly. After passing through variable-dimension forming nip-rollers, the precursor tape with the boron fibers becomes a hybrid boron reinforced polymer matrix composite. A driving mechanism is used to pulled the precursor tape through the method and a take-up spool is used to collect the formed hybrid boron reinforced polymer matrix composite.

  5. Effects of fibers on the color change and stability of resin composites after accelerated aging.

    PubMed

    Tuncdemir, Ali Riza; Aykent, Filiz

    2012-01-01

    Composite resins were reinforced with glass and polyethylene fibers in this study, and the effect of fiber reinforcement on the color change of composite resins was investigated. After accelerated aging, the effect of fiber reinforcement on the color stability of composite resins was also examined. There were three experimental groups (n=12 disks per group): non-fiber-reinforced composite (non-FRC control), polyethylene fiber (Ribbond-THM)-reinforced composite, and glass fiber (everstick NET)-reinforced composite. According to the critical remarks of color change of National Bureau of Standarts (NSB), glass fiber-reinforced anterior composites showed trace color change and polyethylene-fiber reinforced composites showed slight color change before accelerated aging. After accelerated aging, both control and fiber-reinforced composite groups showed noticeable color change. It was concluded that both the types of fiber reinforcement and composite resin influenced the color change of fiber-reinforced composite resins.

  6. In vivo wear pattern of experimental light-cured hybrid composite resins.

    PubMed

    Okamoto, A; Sekiya, K; Fukushima, M; Iwaku, M

    1993-12-01

    This study evaluated the effect of various types of microfiller on the in vivo wear resistance of composite resins. Experimental light-cured composites with two different microfiller systems were prepared: (1) 56 wt % fine quartz filler, 21 wt% organic filler and 3 wt% colloidal silica filler (Hybrid type 1), and (2) 64 wt% fine quartz filler and 21 wt% colloidal silica filler (Hybrid type 2). The resin monomer consisted of 50 wt % Bis-GMA and 50 wt% TEGDMA. These materials were placed in 2 mm diameter cylindrical cavities located in the OCA (occlusal contact area) or the CFA (contact free area) in cast gold-silver-palladium alloy full coverage crowns, which were temporarily set in a volunteer patient's mouth. The crowns were removed at monthly intervals for SEM observation. Hybrid type 1, which contained organic fillers, showed bulk fractures in the OCA, by the second month of the experiment. However, reinforcement of the resin matrix by dispersion of microfiller provided Hybrid type 2 with superior wear resistance for up to two months.

  7. High-Temperature Fatigue of a Hybrid Aluminum Metal Matrix Composite

    NASA Astrophysics Data System (ADS)

    Clark, J. T.; Sanders, P. G.

    2014-01-01

    An aluminum metal matrix composite (MMC) brake drum was tested in fatigue at room temperature and extreme service temperatures. At room temperature, the hybrid composite did not fail and exceeded estimated vehicle service times. At higher temperatures (62 and 73 pct of the matrix eutectic), fatigue of a hybrid particle/fiber MMC exhibited failure consistent with matrix overloading. Overaging of the A356 matrix coupled with progressive fracture of the SiC particles combined to create the matrix overload condition. No evidence of macro-fatigue crack initiation or growth was observed, and the matrix-particle interface appeared strong with no debonding, visible matrix phases, or porosity. An effective medium model was constructed to test the hypothesis that matrix overloading was the probable failure mode. The measured particle fracture rate was fit using realistic values of the SiC Weibull strength and modulus, which in turn predicted cycles to failure within the range observed in fatigue testing.

  8. Flexural Properties of E Glass and TR50S Carbon Fiber Reinforced Epoxy Hybrid Composites

    NASA Astrophysics Data System (ADS)

    Dong, Chensong; Sudarisman; Davies, Ian J.

    2013-01-01

    A study on the flexural properties of E glass and TR50S carbon fiber reinforced hybrid composites is presented in this paper. Specimens were made by the hand lay-up process in an intra-ply configuration with varying degrees of glass fibers added to the surface of a carbon laminate. These specimens were then tested in the three-point bend configuration in accordance with ASTM D790-07 at three span-to-depth ratios: 16, 32, and 64. The failure modes were examined under an optical microscope. The flexural behavior was also simulated by finite element analysis, and the flexural modulus, flexural strength, and strain to failure were calculated. It is shown that although span-to-depth ratio shows an influence on the stress-strain relationship, it has no effect on the failure mode. The majority of specimens failed by either in-plane or out-of-plane local buckling followed by kinking and splitting at the compressive GFRP side and matrix cracking combined with fiber breakage at the CFRP tensile face. It is shown that positive hybrid effects exist for the flexural strengths of most of the hybrid configurations. The hybrid effect is noted to be more obvious when the hybrid ratio is small, which may be attributed to the relative position of the GFRP layer(s) with respect to the neutral plane. In contrast to this, flexural modulus seems to obey the rule of mixtures equation.

  9. A review of composite material applications in the automotive industry for the electric and hybrid vehicle

    NASA Technical Reports Server (NTRS)

    Bauer, J. L.

    1979-01-01

    A review is made of the state-of-the-art in regard to the use of composite materials for reducing the structural mass of automobiles. Reduction of mass provides, in addition to other engineering improvements, increased performance/range advantages that are particularly needed in the electric and hybrid vehicle field. Problems encountered include the attainment of mass production techniques and the prevention of environmental hazards.

  10. Chemical composition and in situ dry matter and fiber disappearance of sorghum x Sudangrass hybrids.

    PubMed

    Beck, P A; Hutchison, S; Gunter, S A; Losi, T C; Stewart, C B; Capps, P K; Phillips, J M

    2007-02-01

    Three sorghum x Sudangrass hybrids were planted in twelve 0.2-ha plots to test the effect of date of harvest and hybrid on plant maturity, DM yield, chemical composition, and in situ DM and fiber disappearance. Sweet Sunny Sue (a non-brown midrib (BMR) hybrid; nonBMR), NutriPlus BMR (a BMR hybrid; NP-BMR), and Dry Stalk BMR (a BMR hybrid; DS-BMR) were planted on 26 June 2003 at 22.4 kg of seed/ha. Beginning 34 d after planting, plant height and phenological growth stage were assessed weekly in 10 random, 0.5-m(2) quadrats per plot. Plants were clipped to 2.5 cm in height and analyzed for CP, NDF, and ADF using near-infrared spectroscopy. Composite samples harvested from each plot on d 34, 48, and 63 were incubated in the rumen of 3 steers to determine the in situ disappearance of DM and NDF in a 3 x 3 Latin square. Forage yield was greater (P < or =0.02) for nonBMR than NP-BMR on d 41 and 55 and tended (P = 0.08) to be greater on d 48. The DS-BMR hybrid produced more (P = 0.04) forage DM than the NP-BMR on d 48. When DM yield was regressed on growth stage at harvest, BMR hybrids were predicted to produce 265 kg/ha more DM (P < 0.01) than nonBMR, at the late-boot stage. At all harvest dates, NDF concentrations were less (P < or =0.02) for BMR than nonBMR. The DS-BMR had greater (P < or =0.02) NDF concentrations than NP-BMR on d 41, 48, 55, and 63. Detergent fiber concentrations were predicted to be greater (P < 0.01) in nonBMR than BMR when regressed on growth stage at harvest, but the magnitude of the differences in fiber concentration diminished with growth stage. The A fractions of DM and NDF were greater (P < 0.01) and the C fraction was less (P < 0.01) for BMR hybrids than nonBMR. The B fraction of DM was not affected (P = 0.15) by hybrid type. The B fraction of NDF was not different (P = 0.28) on d 34 but was greater (P < 0.01) on d 48 and 63 for BMR than nonBMR. Effective degradability of NDF and DM was greater (P < 0.02) for BMR than nonBMR on all harvest

  11. Physico-mechanical and tribological properties of Grewia Optiva fiber/bio-particulates hybrid polymer composites

    NASA Astrophysics Data System (ADS)

    Kumar, Sandeep; Gangil, Brijesh; Patel, Vinay Kumar

    2016-05-01

    Lack of resources and increasing environmental issues has received widespread attention for the development of natural fiber/ particulate reinforced hybrid polymer composites. In the present investigation the authors use (GO) Grewia Optiva as the main reinforcement and rice husk/wheat straw as additional particulates for improving the mechanical and wear properties of polymer composites. The samples were prepared by hand layup technique according to ASTM standards. The results indicated that incorporation of wheat straw with GO polymer materials exhibited better hardness (2.5 times harder) and less wear (0.85 times) than mono GO fiber polymer composites (GOFRP). Moreover, Rice husk filled GOFRP shows superior impact energy among the all set of composites. Water absorption behavior was also discussed in this investigation.

  12. Low Working-Temperature Acetone Vapor Sensor Based on Zinc Nitride and Oxide Hybrid Composites.

    PubMed

    Qu, Fengdong; Yuan, Yao; Guarecuco, Rohiverth; Yang, Minghui

    2016-06-01

    Transition-metal nitride and oxide composites are a significant class of emerging materials that have attracted great interest for their potential in combining the advantages of nitrides and oxides. Here, a novel class of gas sensing materials based on hybrid Zn3 N2 and ZnO composites is presented. The Zn3 N2 /ZnO (ZnNO) composites-based sensor exhibits selectivity and high sensitivity toward acetone vapor, and the sensitivity is dependent on the nitrogen content of the composites. The ZnNO-11.7 described herein possesses a low working temperature of 200 °C. The detection limit (0.07 ppm) is below the diabetes diagnosis threshold (1.8 ppm). In addition, the sensor shows high reproducibility and long-term stability.

  13. Graphene-Based Hybrid Composites for Efficient Thermal Management of Electronic Devices.

    PubMed

    Shtein, Michael; Nadiv, Roey; Buzaglo, Matat; Regev, Oren

    2015-10-28

    Thermal management has become a critical aspect in next-generation miniaturized electronic devices. Efficient heat dissipation reduces their operating temperatures and insures optimal performance, service life, and efficacy. Shielding against shocks, vibrations, and moisture is also imperative when the electronic circuits are located outdoors. Potting (or encapsulating) them in polymer-based composites with enhanced thermal conductivity (TC) may provide a solution for both thermal management and shielding challenges. In the current study, graphene is employed as a filler to fabricate composites with isotropic ultrahigh TC (>12 W m(-1) K(-1)) and good mechanical properties (>30 MPa flexural and compressive strength). To avoid short-circuiting the electronic assemblies, a dispersion of secondary ceramic-based filler reduces the electrical conductivity and synergistically enhances the TC of composites. When utilized as potting materials, these novel hybrid composites effectively dissipate the heat from electronic devices; their operating temperatures decrease from 110 to 37 °C, and their effective thermal resistances are drastically reduced, by up to 90%. The simple filler dispersion method and the precise manipulation of the composite transport properties via hybrid filling offer a universal approach to the large-scale production of novel materials for thermal management and other applications. PMID:26445279

  14. Age-dependent morphological and compositional variations on Ceres

    NASA Astrophysics Data System (ADS)

    Jaumann, Ralf

    2016-04-01

    Extended smooth plains cover the interior of a number of craters on Ceres. Smooth plains appear on different topographic levels associated with pits and flow-like features that overrun crater rims. The material forming these plains also ponds in depressions and smaller craters and cover the pre-existing surface creating distinct geological boundaries. Ikapati crater shows smooth plains on different topographic levels associated with pits and flow-like features that overrun crater rims. The material forming these plains, ponds in depressions and smaller craters and cover the pre-existing surface creating a distinct geological boundary. The interior of Occator also exhibits extended plains of ponded material, multiple flows originating from the center overwhelming the mass wasting deposits from the rim, dome-like features, vents cracks and fissures. Furthermore, crater densities on Occator's floor are lower than those on the ejecta blanket indicating a post-impact formation age of the flows. The flows to the northeast appear to originate from the central region and move slightly uphill. This indicates either a feeding zone that pushes the flows forward by supplying low-viscosity material or a depression of the crater center, possibly after discharging a subsurface reservoir. The plains and flows as well as some areas surrounding the craters appear spectrally blue. Both plains and flow material are characterized in camera and spectrometer visible spectra by a slightly negative slope with a gradual drop off up to 10% in reflectance from 0.5μm to 1μm. Although the spectral variations in the visible are subtle, they are clearly expressed in the color ratio composite. The crater densities of 20 locations across the surface of Ceres with different spectral behavior were analyzed in order to investigate the age dependence of spectral surface features. The results indicate that bluish material is mainly associated with the youngest impact craters on Ceres (< 0.5 Ga) while

  15. Uranium isotopic composition and absolute ages of Allende chondrules

    NASA Astrophysics Data System (ADS)

    Brennecka, G. A.; Budde, G.; Kleine, T.

    2015-11-01

    A handful of events, such as the condensation of refractory inclusions and the formation of chondrules, represent important stages in the formation and evolution of the early solar system and thus are critical to understanding its development. Compared to the refractory inclusions, chondrules appear to have a protracted period of formation that spans millions of years. As such, understanding chondrule formation requires a catalog of reliable ages, free from as many assumptions as possible. The Pb-Pb chronometer has this potential; however, because common individual chondrules have extremely low uranium contents, obtaining U-corrected Pb-Pb ages of individual chondrules is unrealistic in the vast majority of cases at this time. Thus, in order to obtain the most accurate 238U/235U ratio possible for chondrules, we separated and pooled thousands of individual chondrules from the Allende meteorite. In this work, we demonstrate that no discernible differences exist in the 238U/235U compositions between chondrule groups when separated by size and magnetic susceptibility, suggesting that no systematic U-isotope variation exists between groups of chondrules. Consequently, chondrules are likely to have a common 238U/235U ratio for any given meteorite. A weighted average of the six groups of chondrule separates from Allende results in a 238U/235U ratio of 137.786 ± 0.004 (±0.016 including propagated uncertainty on the U standard [Richter et al. 2010]). Although it is still possible that individual chondrules have significant U isotope variation within a given meteorite, this value represents our best estimate of the 238U/235U ratio for Allende chondrules and should be used for absolute dating of these objects, unless such chondrules can be measured individually.

  16. The concept of a novel hybrid smart composite reinforced with radially aligned zigzag carbon nanotubes on piezoelectric fibers

    NASA Astrophysics Data System (ADS)

    Ray, M. C.

    2010-03-01

    A new hybrid piezoelectric composite (HPZC) reinforced with zigzag single-walled carbon nanotubes (CNTs) and piezoelectric fibers is proposed. The novel constructional feature of this composite is that the uniformly aligned CNTs are radially grown on the surface of piezoelectric fibers. A micromechanics model is derived to estimate the effective piezoelectric and elastic properties. It is found that the effective piezoelectric coefficient e31 of the proposed HPZC, which accounts for the in-plane actuation, is significantly higher than that of the existing 1-3 piezoelectric composite without reinforcement with carbon nanotubes and the previously reported hybrid piezoelectric composite (Ray and Batra 2009 ASME J. Appl. Mech. 76 034503).

  17. Sex chromosome loss and aging: In situ hybridization studies on human interphase nuclei

    SciTech Connect

    Guttenbach, M.; Koschorz, B.; Bernthaler, U.

    1995-11-01

    A total of 1,000 lymphocyte interphase nuclei per proband from 90 females and 138 males age 1 wk to 93 years were analyzed by in situ hybridization for loss of the X and Y chromosomes, respectively. Both sex chromosomes showed an age-dependent loss. In males, Y hypoploidy was very low up to age 15 years (0.05%) but continuously increased to a frequency of 1.34% in men age 76-80 years. In females, the baseline level for X chromosome loss is much higher than that seen for the Y chromosome in males. Even prepubertal females show a rate of X chromosome loss on the order of 1.5%-2.5%, rising to {approximately}4.5%-5% in women older than 75 years. Dividing the female probands into three biological age groups on the basis of sex hormone function (<13 years, 13-51 years, and >51 years), a significant correlation of X chromosome loss versus age could clearly be demonstrated in women beyond age 51 years. Females age 51-91 years showed monosomy X at a rate from 3.2% to 5.1%. In contrast to sex chromosomal loss, the frequency of autosomal monosomies does not change during the course of aging: chromosome 1 and chromosome 17 monosomic cells were found with a constant incidence of 1.2% and 1%, respectively. These data also indicate that autosome loss in interphase nuclei is not a function of chromosome size. 34 refs., 5 figs., 6 tabs.

  18. Effect of winding layer and speed on kenaf/glass fiber hybrid reinforced acrylonitrile butadiene styrene (ABS) composites

    NASA Astrophysics Data System (ADS)

    Khoni, Norizzahthul Ainaa Abdul; Sharifah Shahnaz S., B.; Ghazali, Che Mohd Ruzaidi

    2016-07-01

    The usage of natural fiber is becoming significant in composite industries due to their good performance. Single and continuous natural fibers have relatively high mechanical properties; especially their young modulus can be as high as glass fibers. Filament winding is a method to produce technically aligned composites which have high fibers content. The properties of filament winding can be tailored to meet the end product requirements. This research studied the compression properties of kenaf/glass fibers hybrid reinforced composites. Kenaf/glass fibers hybrid composite samples were fabricated by filament winding technique and their properties were compared with the properties of neat kenaf fiber and glass fibers composites. The kenaf/glass fiber hybrid composites exhibited higher strength compared to the neat glass fibers composites. Composites of helical pattern, which produced at low winding speed showed better compression resistance than hoop pattern winding, which produced at high winding speed. As predicted, kenaf composite showed highest water absorption; followed by kenaf/glass fiber hybrid composites while neat glass fiber has lowest water absorption capability.

  19. The penetrometer - A technique for monitoring composite propellant ageing characteristics

    NASA Astrophysics Data System (ADS)

    Faulkner, G. S.

    The monitoring of the natural and accelerated aging of rubbery composite propellants by using a non-destructive mechanical properties tester, the 'penetrometer', is presented. This capability facilitates predictions of rocket-motor service life and also detects motors that may not have been stored correctly. The probe is inserted into the conduit of a motor and held in place by an integral, motor-specific, air-bag. The indenter is then driven into the charge in a low-stress region. Information obtained from the test is displayed graphically on a microcomputer, analyzed, and stored. It is concluded that, because not all of the rocket motors will have seen the same environment depending on the individual motor history, it will be possible to extend the lifetime before disposal since the charge can now be tested. This in turn will lead to financial savings if the charge's life can be said to have 'X' years of life left and does not need to be withdrawn from service.

  20. Age and Gender Related Changes in the Normal Human Brain using Hybrid Diffusion Imaging (HYDI)

    PubMed Central

    Wu, Yu-Chien; Field, Aaron S.; Whalen, Paul J.; Alexander, Andrew L.

    2011-01-01

    Diffusion tensor imaging has been widely used to study brain diseases, disorders, development and aging. However, few studies have explored the effects of aging on diffusion imaging measures with higher b-values. Further the water diffusion in biological tissues appears bi-exponential although this also has not been explored with aging. In this study, hybrid diffusion imaging (HYDI) was used to study fifty-two healthy subjects with an age range from 18 to 72 years. The HYDI diffusion-encoding scheme consisted of five concentric q-space shells with b-values raging from 0 to 9375 s/mm2. Quantitative diffusion measures were investigated as a function of age and gender using both region-of-interest (whole brain white matter, genu and splenium of corpus callosum, posterior limb of the internal capsule) and whole-brain voxel based analyses. Diffusion measures included measures of the diffusion probability density function (zero displacement probability, and mean squared displacement), bi-exponential diffusion (i.e. volume fractions of fast/slow diffusion compartments and fast/slow diffusivities), and DTI measures (fractional anisotropy, mean diffusivity, axial diffusivity and radial diffusivity). The bi-exponential volume fraction, the fast diffusivity, and the axial diffusivity measures (f1, D1 and Da) were found to be more sensitive to normal aging than the restricted, slow and radial diffusion measures (Po, D2 and Dr). The bi-exponential volume fraction, f1, showed the most widespread age-dependence in the voxel-based analyses although both FA and mean diffusivity did show changes in frontal white matter regions that may be associated with age-related decline. PMID:20932911

  1. Spatial reference memory in normal aging Fischer 344 × Brown Norway F1 hybrid rats.

    PubMed

    McQuail, Joseph A; Nicolle, Michelle M

    2015-01-01

    Fischer 344 × Brown Norway F1 (F344 × BN-F1) hybrid rats express greater longevity with improved health relative to aging rodents of other strains; however, few behavioral reports have thoroughly evaluated cognition across the F344 × BN-F1 lifespan. Consequently, this study evaluated spatial reference memory in F344 × BN-F1 rats at 6, 18, 24, or 28 months of age in the Morris water maze. Reference memory decrements were observed between 6 and 18 months and 18 and 24 months. At 28 months, spatial learning was not worse than 24 months, but swim speed was significantly slower. Reliable individual differences revealed that ∼50% of 24- to 28-month-old rats performed similarly to 6 months, whereas others were spatial learning impaired. Aged rats were impaired at learning within daily training sessions but not impaired at retaining information between days of training. Aged rats were also slower to learn to escape onto the platform, regardless of strategy. In summary, these data clarify the trajectory of cognitive decline in aging F344 × BN-F1 rats and elucidate relevant behavioral parameters.

  2. In situ composition and luminescence of terbium coordination polymers/PEMA hybrid thick films

    NASA Astrophysics Data System (ADS)

    Yan, Bing; Wang, Qian-Ming

    2004-12-01

    Some terbium coordination polymers with infinite chain polymeric structures were in situ composed with ethyl methacrylate (EMA). With the polymerization of EMA monomer and the formation of terbium coordination polymers of methylbenzoic acid and 2-chloro benzoic acid, the transparent hybrid thick films composed by [Tb(OMBA)3]n ([Tb(MMBA)3]n, [Tb(OCBA)3]n) and poly ethyl methacrylate (PEMA) have been achieved. The luminescence properties and energy transfer for these polymeric composite films were studied with absorption spectra, fluorescent excitation and emission spectra in detail. All the hybrid thick films composed with terbium coordination polymers show the characteristic strong green emission of terbium ions, which implies the same energy transfer mechanism as the pure complex and the hybrid composite film is a suitable substrate for the luminescence of terbium ions. In the range of composing concentration of luminescent species (0.005, 0.01, 0.025, 0.05, 0.1 and 0.2 mmol/7.5 ml EMA), emission intensities increases with the increasing of corresponding composing concentration and concentration quenching effect has not taken place.

  3. Cathodoluminescence characterization of polystyrene-BaZrO3 hybrid composites

    NASA Astrophysics Data System (ADS)

    Savchyn, V. P.; Popov, A. I.; Aksimentyeva, O. I.; Klym, H.; Horbenko, Yu. Yu.; Serga, V.; Moskina, A.; Karbovnyk, I.

    2016-07-01

    The radiation properties and the electronic structure of hybrid composites based on suspension polystyrene (PS) and nanocrystals of BaZrO3 (BZO) (d < 50 nm) have been studied using luminescent spectroscopy and x-ray analysis. A strong cathodoluminescence (CL) in BZO-nanocrystals is observed in temperature range 80-293 K. It is modified in BZO-PS composites: both the low- and a high-energy bands (near 4 eV) appear, together with a significant reduction in the CL intensity. A decrease of the lattice parameter a for BZO phase in the composite and the modification of CL spectra indicate for changes in the nanocrystalline structure induced by the polymer.

  4. In vitro performance of lipid-PLGA hybrid nanoparticles as an antigen delivery system: lipid composition matters

    PubMed Central

    2014-01-01

    Due to the many beneficial properties combined from both poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) and liposomes, lipid-PLGA hybrid NPs have been intensively studied as cancer drug delivery systems, bio-imaging agent carriers, as well as antigen delivery vehicles. However, the impact of lipid composition on the performance of lipid-PLGA hybrid NPs as a delivery system has not been well investigated. In this study, the influence of lipid composition on the stability of the hybrid NPs and in vitro antigen release from NPs under different conditions was examined. The uptake of hybrid NPs with various surface charges by dendritic cells (DCs) was carefully studied. The results showed that PLGA NPs enveloped by a lipid shell with more positive surface charges could improve the stability of the hybrid NPs, enable better controlled release of antigens encapsulated in PLGA NPs, as well as enhance uptake of NPs by DC. PMID:25232295

  5. In vitro performance of lipid-PLGA hybrid nanoparticles as an antigen delivery system: lipid composition matters

    NASA Astrophysics Data System (ADS)

    Hu, Yun; Ehrich, Marion; Fuhrman, Kristel; Zhang, Chenming

    2014-08-01

    Due to the many beneficial properties combined from both poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) and liposomes, lipid-PLGA hybrid NPs have been intensively studied as cancer drug delivery systems, bio-imaging agent carriers, as well as antigen delivery vehicles. However, the impact of lipid composition on the performance of lipid-PLGA hybrid NPs as a delivery system has not been well investigated. In this study, the influence of lipid composition on the stability of the hybrid NPs and in vitro antigen release from NPs under different conditions was examined. The uptake of hybrid NPs with various surface charges by dendritic cells (DCs) was carefully studied. The results showed that PLGA NPs enveloped by a lipid shell with more positive surface charges could improve the stability of the hybrid NPs, enable better controlled release of antigens encapsulated in PLGA NPs, as well as enhance uptake of NPs by DC.

  6. A hybrid method based upon nonlinear Lamb wave response for locating a delamination in composite laminates.

    PubMed

    Yelve, Nitesh P; Mitra, Mira; Mujumdar, P M; Ramadas, C

    2016-08-01

    A new hybrid method based upon nonlinear Lamb wave response in time and frequency domains is introduced to locate a delamination in composite laminates. In Lamb wave based nonlinear method, the presence of damage is shown by the appearance of higher harmonics in the Lamb wave response. The proposed method not only uses this spectral information but also the corresponding temporal response data, for locating the delamination. Thus, the method is termed as a hybrid method. The paper includes formulation of the method and its application to locate a Barely Visible Impact Damage (BVID) induced delamination in a Carbon Fiber Reinforced Polymer (CFRP) laminate. The method gives the damage location fairly well. It is a baseline free method, as it does not need data from the pristine specimen. PMID:27115575

  7. Hydrogen storage behaviors of Ni-doped graphene Oxide/MIL-101 hybrid composites.

    PubMed

    Lee, Seul-Yi; Park, Soo-Jin

    2013-01-01

    In this work, Ni-doped graphene oxide/MIL-101 hybrid composites (Ni--GO/MIL) were prepared to investigate their hydrogen storage behaviors. Ni--GO/MIL was synthesized by adding Ni--GO in situ during the synthesis of MIL-101 using a hydrothermal process, which was conducted by conventional convection heating with Cr(III) ion as a metal center and telephthalic acid as organic ligands. The crystalline structures and morphologies were measured by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The specific surface area and micropore volume were investigated by N2/77 K adsorption isotherms using the Brunauer-Emmett-Teller (BET) method and Dubinin-Radushkevic (D-R) equation, respectively. The hydrogen storage capacity was investigated by BEL-HP at 77 K and 1 bar. The obtained results show that Ni--GO/MIL presents new directions for achieving novel hybrid materials with higher hydrogen storage capacity.

  8. A hybrid method based upon nonlinear Lamb wave response for locating a delamination in composite laminates.

    PubMed

    Yelve, Nitesh P; Mitra, Mira; Mujumdar, P M; Ramadas, C

    2016-08-01

    A new hybrid method based upon nonlinear Lamb wave response in time and frequency domains is introduced to locate a delamination in composite laminates. In Lamb wave based nonlinear method, the presence of damage is shown by the appearance of higher harmonics in the Lamb wave response. The proposed method not only uses this spectral information but also the corresponding temporal response data, for locating the delamination. Thus, the method is termed as a hybrid method. The paper includes formulation of the method and its application to locate a Barely Visible Impact Damage (BVID) induced delamination in a Carbon Fiber Reinforced Polymer (CFRP) laminate. The method gives the damage location fairly well. It is a baseline free method, as it does not need data from the pristine specimen.

  9. Projected equations of motion approach to hybrid quantum/classical dynamics in dielectric-metal composites

    NASA Astrophysics Data System (ADS)

    McMillan, Ryan J.; Stella, Lorenzo; Grüning, Myrta

    2016-09-01

    We introduce a hybrid method for dielectric-metal composites that describes the dynamics of the metallic system classically while retaining a quantum description of the dielectric. The time-dependent dipole moment of the classical system is mimicked by the introduction of projected equations of motion (PEOM), and the coupling between the two systems is achieved through an effective dipole-dipole interaction. To benchmark this method, we model a test system (semiconducting quantum dot-metal nanoparticle hybrid). We begin by examining the energy absorption rate, showing agreement between the PEOM method and the analytical rotating wave approximation (RWA) solution. We then investigate population inversion and show that the PEOM method provides an accurate model for the interaction under ultrashort pulse excitation where the traditional RWA breaks down.

  10. Simulation of ultrasonic inspection of curved composites using a hybrid semi-analytical/numerical code

    NASA Astrophysics Data System (ADS)

    Reverdy, Frédéric; Mahaut, Steve; Dominguez, Nicolas; Dubois, Philippe

    2015-03-01

    Carbon Fiber reinforced composites are increasingly used in structural parts in the aeronautics industry, as they allow to reduce the weight of aircrafts while maintaining high mechanical performances. However, such structures can be complicated to inspect due to their complex geometries and complex composite properties, leading to highly heterogeneous and anisotropic materials. Different potential damages and manufacturing flaws related to these parts are to be detected: porosities, ply waviness, delaminations after impact. Ultrasonic inspection, which is commonly used to test the full volume of composite panels, thus has to cope with both complex wave propagation (within anisotropic parts whose crystallographic orientation varies according to the layers structure) and flaw interaction (local distortion of plies such as ply waviness, small pores, structural noise due to periodicity patterns…). Developing NDT procedures for those parts therefore requires simulation tools to help for understanding those phenomena, and to optimize probes and techniques. Within the CIVA multi-techniques platform, CEA-LIST has developed semi-analytical tools for ultrasonic techniques, which have the advantages of high computational efficiency (fast calculations), but with limited range of application due to some hypothesis (for instance, homogenization approaches which don't allow to take account of structural noise). On the other hand, numerical methods such as finite element (FEM) or finite difference in time domain (FDTD) are more suitable to compute ultrasonic wave propagation and defect scattering in complex materials such as composite but require more computational efforts. Hybrid methods couple semi-analytical solutions and numerical computations in limited spatial domains to handle complex cases with high computation performances. In CIVA we have integrated a hybrid model that combines the semi-analytical methods developed at CEA to FDTD codes developed at Airbus Group

  11. Hybrid carbon-glass fiber/toughened epoxy thick composites subject to drop-weight and ballistic impacts

    NASA Astrophysics Data System (ADS)

    Sevkat, Ercan

    The goals of this study are to investigate the low velocity and ballistic impact response of thick-section hybrid fiber composites at room temperature. Plain-woven S2-Glass and IM7 Graphite fabrics are chosen as fiber materials reinforcing the SC-79 epoxy. Four different types of composites consisting of alternating layers of glass and graphite woven fabric sheets are considered. Tensile tests are conducted using 98 KN (22 kip) MTS testing machine equipped with environmental chamber. Low-velocity impact tests are conducted using an Instron-Dynatup 8250 impact test machine equipped with an environmental chamber. Ballistic impact tests are performed using helium pressured high-speed gas-gun. Tensile tests results were used to define the material behavior of the hybrid and non-hybrid composites in Finite Element modeling. The low velocity and ballistic impact tests showed that hybrid composites performance was somewhere between non-hybrid woven composites. Using woven glass fabrics as outer skin improved the impact performance of woven graphite composite. However hybrid composites are prone to delamination especially between dissimilar layers. The ballistic limit velocity V50 hybrid composites were higher that of woven graphite composite and lower than that of woven glass composite. Both destructive cross-sectional micrographs and nondestructive ultrasonic techniques are used to evaluate the damage created by impact. The Finite Element code LS-DYNA is chosen to perform numerical simulations of low velocity and ballistic impact on thick-section hybrid composites. The damage progression in these composites shows anisotropic nonlinearity. The material model to describe this behavior is not available in LS-DYNA material library. Initially, linear orthotropic material with damage (Chan-Chan Model) is employed to simulate some of the experimental results. Then, user-defined material subroutine is incorporated into LS-DYNA to simulate the nonlinear behavior. The

  12. Parametric Study of Dry Sliding Wear Behavior of Hybrid Metal Matrix Composite Produced by a Novel Process

    NASA Astrophysics Data System (ADS)

    Sharma, Pardeep; Sharma, Satpal; Khanduja, Dinesh

    2015-07-01

    In the present research work, silicon nitride (Si3N4) and graphite (Gr) ceramic powders are ball milled to obtain homogeneous mixing and consistent density of combined powder. The ball-milled powder is used as reinforcement for hybrid composite development by stir casting process in the inert atmosphere. After mixing by ball milling for 100 hours, the density of ball-milled (Si3N4 + Gr) powder is measured as 2.81 g/cm3, which is approximately equal to the density of aluminum (2.7 g/cm3). The microstructures and hardness of the manufactured hybrid composites are analyzed and compared with Si3N4- and Gr-reinforced composites. Scanning electron micrograph reveals a reasonably uniform dispersion of ball-milled (Si3N4 + Gr) reinforcement in the metal matrix composites. Hardness results reveal that hybrid composites have more hardness than Gr-reinforced and lower hardness than Si3N4-reinforced composites. The dry sliding wear behavior of aluminum matrix hybrid composites has also been investigated. Response surface methodology is used to develop wear model of hybrid composites using reinforcement percentage ( R), load ( L), sliding speed ( S), and sliding distance ( D) as the process parameters. The results of wear investigation show that increase in sliding speed ( S) and percentage reinforcement ( R) reduce the wear, while increase in sliding distance ( D) or load ( L) increases the wear of the hybrid composites. Further, the load-sliding distance and load-sliding speed interactions increase the wear, while the wear reduces due to sliding speed-sliding distance interaction in the high range. The errors between the modeled and experimental results are found within 3 to 7 pct.

  13. Perspectives on State-of-the-Art Carbon Nanotube/Polyaniline and Graphene/Polyaniline Composites for Hybrid Supercapacitor Electrodes.

    PubMed

    Srikanth, Vadali V S S; Ramana, Gedela Venkata; Kumar, Puttapati Sampath

    2016-03-01

    Supercapacitors are attractive alternative energy storage sources. They offer high energy/power density with other characteristics like fast discharge/charge time, long operation stability, safety etc. In a supercapacitor, working electrode material is the principal constituent. At present there are numerous electrode materials (with properties) suitable for their use in hybrid type supercapacitors. Carbon/polyaniline (PANi) composites are one class of such electrode materials. Here, perspectives on state-of-the-art carbon/PANi composites namely carbon nanotube/polyaniline and graphene/polyaniline composites expedient as hybrid type supercapacitor electrode materials will be presented. PMID:27455650

  14. Perspectives on State-of-the-Art Carbon Nanotube/Polyaniline and Graphene/Polyaniline Composites for Hybrid Supercapacitor Electrodes.

    PubMed

    Srikanth, Vadali V S S; Ramana, Gedela Venkata; Kumar, Puttapati Sampath

    2016-03-01

    Supercapacitors are attractive alternative energy storage sources. They offer high energy/power density with other characteristics like fast discharge/charge time, long operation stability, safety etc. In a supercapacitor, working electrode material is the principal constituent. At present there are numerous electrode materials (with properties) suitable for their use in hybrid type supercapacitors. Carbon/polyaniline (PANi) composites are one class of such electrode materials. Here, perspectives on state-of-the-art carbon/PANi composites namely carbon nanotube/polyaniline and graphene/polyaniline composites expedient as hybrid type supercapacitor electrode materials will be presented.

  15. Age and Social Composition Factors as Explanations for Cleavages in Socio-Political Values.

    ERIC Educational Resources Information Center

    Tedin, Kent L.

    1978-01-01

    This analysis tested for the effects of age vs social composition in explaining variation in four attitudinal dependent variables. Using a sample especially drawn to study generational differences, and employing a multivariate statistical model, it was found that age differences were only modestly reduced by social composition variables. (Author)

  16. Hybrid Three-Dimensional (3-D) Woven Thick Composite Architectures in Bending

    NASA Astrophysics Data System (ADS)

    Pankow, Mark; Quabili, Ashiq; Yen, Chian-Fong

    2013-11-01

    In this study, three 3-dimensional (3-D) woven composite materials were examined to determine how yarn tow configurations affect the flexural response of the structure. Woven fabric preforms were manufactured with a Z-fiber architecture in 2-3 in. thicknesses. These preforms contained S-2 Glass (AGY, Aiken, SC, USA), carbon, and Twaron (Teijin Aramid, Arnhem, The Netherlands) yarns in different architectures creating a hybrid material system. Due to the thickness of the material, these samples required a significant span length (30 in.). The results showed a change in the strength and degradation after failure with the addition of carbon layers in tension.

  17. Thermoplastic impact property improvement in hybrid natural fibre epoxy composite bumper beam

    NASA Astrophysics Data System (ADS)

    Davoodi, M. M.; Sapuan, S. M.; Ali, Aidy; Ahmad, D.; Khalina, A.

    2010-05-01

    Utilization of thermoset resin as a bumper beam composite matrix is currently more dominated in car manufacturer suppliers, because of availability, easy processing, low material cost and production equipment investment. Moreover, low viscosity, shrinkage and excellent flow facilitate better fibre impregnation and proper surface resin wetting. Three-dimensional cross linking curing increase impact, creep and environmental stress cracking resistance properties. Low impact properties of natural fibre epoxy composite, are main issues in its employment for automotive structural components. Impact properties in epoxy composite bumper beam could be increased by modifying the resin, reinforcement and manufacturing process as well as geometry parameters such as cross section, thickness, added ribs and fixing method optimizations could strengthen impact resistance. There are two main methods, flexibilisation and toughening, as modifying the resin in order to improve the impact properties of epoxy composite, which form single phase or two-phase morphology to make modifier as epoxy or from separate phase to keep the thermo-mechanical properties. Liquid rubber, thermoplastic, core shell particle and rigid particle are different methods of toughening improvements. In this research, thermoplastic toughening has used to improve impact properties in hybrid natural fibre epoxy composite for automotive bumper beam and has achieved reasonable impact improvements.

  18. RTA-treated carbon fiber/copper core/shell hybrid for thermally conductive composites.

    PubMed

    Yu, Seunggun; Park, Bo-In; Park, Cheolmin; Hong, Soon Man; Han, Tae Hee; Koo, Chong Min

    2014-05-28

    In this paper, we demonstrate a facile route to produce epoxy/carbon fiber composites providing continuous heat conduction pathway of Cu with a high degree of crystal perfection via electroplating, followed by rapid thermal annealing (RTA) treatment and compression molding. Copper shells on carbon fibers were coated through electroplating method and post-treated via RTA technique to reduce the degree of imperfection in the Cu crystal. The epoxy/Cu-plated carbon fiber composites with Cu shell of 12.0 vol % prepared via simple compression molding, revealed 18 times larger thermal conductivity (47.2 W m(-1) K(-1)) in parallel direction and 6 times larger thermal conductivity (3.9 W m(-1) K(-1)) in perpendicular direction than epoxy/carbon fiber composite. Our novel composites with RTA-treated carbon fiber/Cu core/shell hybrid showed heat conduction behavior of an excellent polymeric composite thermal conductor with continuous heat conduction pathway, comparable to theoretical values obtained from Hatta and Taya model.

  19. Composition of Ultra High Energy Cosmic Rays Observed by Telescope Array in Hybrid Mode

    NASA Astrophysics Data System (ADS)

    Hanlon, William; Telescope Array Collaboration

    2016-03-01

    The energy spectrum of cosmic rays exhibits several important features such as the knee (E ~10 15 . 5 eV), ankle (E ~10 18 . 7 eV), and high energy suppression (E ~10 19 . 8 eV). Cosmic ray chemical composition is the key to understanding their galactic and extragalactic sources as well as the origin of particle production and acceleration mechanisms. Energy dependent chemical composition is a fundamental input for models of cosmic ray sources and interstellar transport which may lead to competing explanations of the observed spectral features. Understanding composition will therefore allow one to distinguish between the different scenarios of cosmic ray origin, a decades old problem in astrophysics. In this talk we will describe measurements of ultra high energy cosmic ray composition performed by Telescope Array (TA) using Xmax measured in extended air showers (EAS) simultaneously observed by the TA surface array and TA fluorescence stations (called hybrid mode). Showers with primary energies above 1018 eV will be considered. We will also discuss improved methods of comparing the measured composition to EAS models.

  20. Ferroelectric/ferromagnetic ceramic composite and its hybrid permittivity stemming from hopping charge and conductivity inhomogeneity

    NASA Astrophysics Data System (ADS)

    Zheng, Hui; Li, Lu; Xu, Zhaojun; Weng, Wenjian; Han, Gaorong; Ma, Ning; Du, Piyi

    2013-01-01

    Exploring the nature of multiferroic ceramic composite with dual high performances is much important to take full advantage of its novel dielectric properties. In this paper, Ni0.5Zn0.5291Fe2O4/BaTiO3 ceramic composite is proposed and successfully prepared from BTO and NZFO powders which are obtained by sol-gel process and citric acid combustion method, respectively. Results show that with increasing BTO content from 0 to 25 vol. % in the matrix of NZFO, the permittivity of the composite decreases from 220 k to 100 k at low frequencies (˜40 Hz) and contrarily from 20 to 100 at high frequencies (˜100 MHz). It is mainly ascribed to the instant polarization in NZFO at low frequencies and the polarization in the perovskite phase of BTO at sufficiently high frequencies. The permittivity of the ferrite and composite is shown to be compatible with a hybrid model proposed, which concerns hopping charges between Fe2+ and Fe3+, conductivity heterogeneity at the grain boundaries of the ferrite, and changes in the conductivities of the two phases induced by interdiffusion of the ions between the two phases. The composition dependence of the permittivity is agreeable with Kirkpatrick's compound law with the percolation threshold of NZFO to be about 55 vol. %.

  1. Computational investigation on thermal conductivity behavior of Al 6061-SiC-Gr hybrid metal matrix composites

    NASA Astrophysics Data System (ADS)

    Krishna, S. A. Mohan; Shridhar, T. N.; Krishnamurthy, L.

    2015-10-01

    Metal matrix composites (MMCs) are regarded to be one of the most principal classifications in composite materials. The thermal characterization of hybrid MMCs has become increasingly important in a wide range of applications. Thermal conductivity is one of the most important properties of MMCs. Since nearly all MMCs are used in various temperature ranges, measurement of thermal conductivity as a function of temperature is necessary in order to know the behavior of the material. In the present research, evaluation of thermal conductivity has been accomplished for aluminum alloy (Al) 6061, silicon carbide (SiC) and graphite (Gr) hybrid MMCs from room temperature to 300∘C. Al-based composites reinforced with SiC and Gr particles have been prepared by stir casting technique. The thermal conductivity behavior of hybrid composites with different percentage compositions of reinforcements has been investigated using laser flash technique. The results have indicated that the thermal conductivity of the different compositions of hybrid MMCs decreases by the addition of Gr with SiC and Al 6061. Few empirical models have been validated concerning with the evaluation of thermal conductivity of composites. Using the experimental values namely density, thermal conductivity, specific heat capacity and enthalpy at varying temperature ranges, computational investigation has been carried out to evaluate the thermal gradient and thermal flux.

  2. Computational investigation on thermal expansivity behavior of Al 6061-SiC-Gr hybrid metal matrix composites

    NASA Astrophysics Data System (ADS)

    Mohan Krishna, S. A.; Shridhar, T. N.; Krishnamurthy, L.

    2015-08-01

    Metal matrix composites (MMCs) have been regarded as one of the most principal classifications in composite materials. The thermal characterization of hybrid MMCs has been increasingly important in a wide range of applications. The coefficient of thermal expansion is one of the most important properties of MMCs. Since nearly all MMCs are used in various temperature ranges, measurement of coefficient of thermal expansion (CTE) as a function of temperature is necessary in order to know the behavior of the material. In this research paper, the evaluation of thermal expansivity has been accomplished for Al 6061, silicon carbide (SiC) and Graphite (Gr) hybrid MMCs from room temperature to 300°C. Aluminum (Al)-based composites reinforced with SiC and Gr particles have been prepared by stir casting technique. The thermal expansivity behavior of hybrid composites with different percentage compositions of reinforcements has been investigated. The results have indicated that the thermal expansivity of the different compositions of hybrid MMCs decreases by the addition of Gr with SiC and Al 6061. Few empirical models have been validated for the evaluation of thermal expansivity of composites. Using the experimental values namely modulus of elasticity, Poisson's ratio and thermal expansivity, computational investigation has been carried out to evaluate the thermal parameters namely thermal displacement, thermal strain and thermal stress.

  3. In vitro microleakage of glass-ionomer composite resin hybrid materials.

    PubMed

    Rodrigues, J A; De Magalhães, C S; Serra, M C; Rodrigues Júnior, A L

    1999-01-01

    The purpose of this study was to evaluate the microleakage of six glass-ionomer composite resin hybrid materials compared with a glass-ionomer cement and a composite resin. Standardized class 5 dentin cavities were prepared on root surfaces of 240 extracted human teeth that were randomly assigned to eight groups and restored using the following restorative systems: (I) Vitremer, (II) Compoglass, (III) Photac-Fil Aplicap, (IV) Variglass, (V) Dyract, (VI) Fuji II LC, (VII) Ketac-Fil Aplicap, and (VIII) Z100. The teeth were thermocycled, placed in a 2% methylene blue solution, and sectioned with diamond disks. Dye penetration was scored on a scale of 0-3. Results showed no significant differences among groups VIII, IV, I, V, VI, III, and II. There were also no significant differences among groups VI, III, II, and VII.

  4. On the Design, Characterization and Simulation of Hybrid Metal-Composite Interfaces

    NASA Astrophysics Data System (ADS)

    Kießling, R.; Ihlemann, J.; Pohl, M.; Stommel, M.; Dammann, C.; Mahnken, R.; Bobbert, M.; Meschut, G.; Hirsch, F.; Kästner, M.

    2016-09-01

    Multi-material lightweight designs are a key feature for the development of innovative and resource-efficient products. In the development of a hybrid composite, the interface between the joined components has to be considered in detail as it represents a typical location of the initialization of failure. This contribution gives an overview of the simulative engineering of metal-composite interfaces. To this end, several design aspects on the microscale and macroscale are explained and methods to model the mechanical behavior of the interface within finite element simulations. This comprises the utilization of cohesive elements with a continuum description of the interface. Likewise, traction-separation based cohesive elements, i.e. a zero-thickness idealization of the interface, are outlined and applied to a demonstration example. Within these finite element simulations, the constitutive behavior of the connected components has to be described by suitable material models. Therefore, inelastic material models at large strains are formulated based on rheological models.

  5. Measurement and Prediction of the Thermomechanical Response of Shape Memory Alloy Hybrid Composite Beams

    NASA Technical Reports Server (NTRS)

    Davis, Brian; Turner, Travis L.; Seelecke, Stefan

    2008-01-01

    An experimental and numerical investigation into the static and dynamic responses of shape memory alloy hybrid composite (SMAHC) beams is performed to provide quantitative validation of a recently commercialized numerical analysis/design tool for SMAHC structures. The SMAHC beam specimens consist of a composite matrix with embedded pre-strained SMA actuators, which act against the mechanical boundaries of the structure when thermally activated to adaptively stiffen the structure. Numerical results are produced from the numerical model as implemented into the commercial finite element code ABAQUS. A rigorous experimental investigation is undertaken to acquire high fidelity measurements including infrared thermography and projection moire interferometry for full-field temperature and displacement measurements, respectively. High fidelity numerical results are also obtained from the numerical model and include measured parameters, such as geometric imperfection and thermal load. Excellent agreement is achieved between the predicted and measured results of the static and dynamic thermomechanical response, thereby providing quantitative validation of the numerical tool.

  6. Investigation of the Thermomechanical Response of Shape Memory Alloy Hybrid Composite Beams

    NASA Technical Reports Server (NTRS)

    Davis, Brian A.

    2005-01-01

    Previous work at NASA Langley Research Center (LaRC) involved fabrication and testing of composite beams with embedded, pre-strained shape memory alloy (SMA) ribbons. That study also provided comparison of experimental results with numerical predictions from a research code making use of a new thermoelastic model for shape memory alloy hybrid composite (SMAHC) structures. The previous work showed qualitative validation of the numerical model. However, deficiencies in the experimental-numerical correlation were noted and hypotheses for the discrepancies were given for further investigation. The goal of this work is to refine the experimental measurement and numerical modeling approaches in order to better understand the discrepancies, improve the correlation between prediction and measurement, and provide rigorous quantitative validation of the numerical model. Thermal buckling, post-buckling, and random responses to thermal and inertial (base acceleration) loads are studied. Excellent agreement is achieved between the predicted and measured results, thereby quantitatively validating the numerical tool.

  7. The development, fabrication, and material characterization of polypropylene composites reinforced with carbon nanofiber and hydroxyapatite nanorod hybrid fillers

    PubMed Central

    Liao, Cheng Zhu; Wong, Hoi Man; Yeung, Kelvin Wai Kwok; Tjong, Sie Chin

    2014-01-01

    This study focuses on the design, fabrication, microstructural and property characterization, and biocompatibility evaluation of polypropylene (PP) reinforced with carbon nanofiber (CNF) and hydroxyapatite nanorod (HANR) fillers. The purpose is to develop advanced PP/CNF–HANR hybrids with good mechanical behavior, thermal stability, and excellent biocompatibility for use as craniofacial implants in orthopedics. Several material-examination techniques, including X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, tensile tests, and impact measurement are used to characterize the microstructural, mechanical, and thermal properties of the hybrids. Furthermore, osteoblastic cell cultivation and colorimetric assay are also employed for assessing their viability on the composites. The CNF and HANR filler hybridization yields an improvement in Young’s modulus, impact strength, thermal stability, and biocompatibility of PP. The PP/2% CNF–20% HANR hybrid composite is found to exhibit the highest elastic modulus, tensile strength, thermal stability, and biocompatibility. PMID:24648729

  8. Niobium oxide-polydimethylsiloxane hybrid composite coatings for tuning primary fibroblast functions.

    PubMed

    Young, Matthew D; Tran, Nhiem; Tran, Phong A; Jarrell, John D; Hayda, Roman A; Born, Chistopher T

    2014-05-01

    This study evaluates the potential of niobium oxide-polydimethylsiloxane (PDMS) composites for tuning cellular response of fibroblasts, a key cell type of soft tissue/implant interfaces. In this study, various hybrid coatings of niobium oxide and PDMS with different niobium oxide concentrations were synthesized and characterized using scanning electron microscopy, X-ray photoelectron spectrometry (XPS), and contact angle goniometry. The coatings were then applied to 96-well plates, on which primary fibroblasts were seeded. Fibroblast viability, proliferation, and morphology were assessed after 1, 2, and 3 days of incubation using WST-1 and calcein AM assays along with fluorescent microscopy. The results showed that the prepared coatings had distinct surface features with submicron spherical composites covered in a polymeric layer. The water contact angle measurement demonstrated that the hybrid surfaces were much more hydrophobic than the original pure niobium oxide and PDMS. The combination of surface roughness and chemistry resulted in a biphasic cellular response with maximum fibroblast density on substrate with 40 wt % of niobium oxide. The results of the current study indicate that by adjusting the concentration of niobium oxide in the coating, a desirable cell response can be achieved to improve tissue/implant interfaces.

  9. SERS of semiconducting nanoparticles (TiO{sub 2} hybrid composites).

    SciTech Connect

    Musumeci, A.; Gosztola, D.; Schiller, T.; Dimitrijevic, N.; Mujica, V.; Martin, D.; Rajh, T.

    2009-04-13

    Raman scattering of molecules adsorbed on the surface of TiO{sub 2} nanoparticles was investigated. We find strong enhancement of Raman scattering in hybrid composites that exhibit charge transfer absorption with TiO{sub 2} nanoparticles. An enhancement factor up to {approx}10{sup 3} was observed in the solutions containing TiO{sub 2} nanoparticles and biomolecules, including the important class of neurotransmitters such as dopamine and dopac (3,4-dihydroxy-phenylacetic acid). Only selected vibrations are enhanced, indicating molecular specificity due to distinct binding and orientation of the biomolecules coupled to the TiO{sub 2} surface. All enhanced modes are associated with the asymmetric vibrations of attached molecules that lower the symmetry of the charge transfer complex. The intensity and the energy of selected vibrations are dependent on the size and shape of nanoparticle support. Moreover, we show that localization of the charge in quantized nanoparticles (2 nm), demonstrated as the blue shift of particle absorption, diminishes SERS enhancement. Importantly, the smallest concentration of adsorbed molecules shows the largest Raman enhancements suggesting the possibility for high sensitivity of this system in the detection of biomolecules that form a charge transfer complex with metal oxide nanoparticles. The wavelength-dependent properties of a hybrid composite suggest a Raman resonant state. Adsorbed molecules that do not show a charge transfer complex show weak enhancements probably due to the dielectric cavity effect.

  10. Complex roles of hybrid lipids in the composition, order, and size of lipid membrane domains.

    PubMed

    Hassan-Zadeh, Ebrahim; Baykal-Caglar, Eda; Alwarawrah, Mohammad; Huang, Juyang

    2014-02-11

    Hybrid lipids (HL) are phospholipids with one saturated chain and one unsaturated chain. HL are hypothesized to act as linactants (i.e., 2D surfactants) in cell membranes, reducing line tension and creating nanoscopic lipid domains. Here we compare three hybrid lipids of different chain unsaturation (16:0-18:1PC (POPC), 16:0-18:2PC (PLPC), and 16:0-20:4PC (PAPC)) in their abilities to alter the composition, line tension, order, and compactness of lipid domains. We found that the liquid-ordered (Lo) and liquid-disordered (Ld) lipid domains in PAPC/di18:0PC(DSPC)/cholesterol and PLPC/DSPC/cholesterol mixtures are micrometer-sized, and only the POPC/DSPC/cholesterol system has nanoscopic domains. The results indicate that some HLs with polyunsaturated chains are not linactants, and the monounsaturated POPC displays both properties of weak linactants and "Ld-phase" lipids such as di18:1PC (DOPC). The obtained phase boundaries from giant unilamellar vesicles (GUV) show that both POPC and PLPC partition well in the Lo phases. Our MD simulations reveal that these hybrid lipids decrease the order and compactness of Lo domains. Thus, hybrid lipids distinguish themselves from other lipid groups in this combined "partitioning and loosening" ability, which could explain why the Lo domains of GUVs, which often do not contain HL, are more compact than the raft domains in cell membranes. Our line tension measurement and Monte Carlo simulation both show that even the monounsaturated POPC is a weak linactant with only modest ability to occupy domain boundaries and reduce line tension. A more important property of HLs is that they can reduce physical property differences of Lo and Ld bulk domains, which also reduces line tension at domain boundaries.

  11. TiO2 micro-nano-hybrid surface to alleviate biological aging of UV-photofunctionalized titanium.

    PubMed

    Iwasa, Fuminori; Tsukimura, Naoki; Sugita, Yoshihiko; Kanuru, Rajita Kodali; Kubo, Katsutoshi; Hasnain, Hafiz; Att, Wael; Ogawa, Takahiro

    2011-01-01

    Bioactivity and osteoconductivity of titanium degrade over time after surface processing. This time-dependent degradation is substantial and defined as the biological aging of titanium. UV treatment has shown to reactivate the aged surfaces, a process known as photofunctionalization. This study determined whether there is a difference in the behavior of biological aging for titanium with micro-nano-hybrid topography and titanium with microtopography alone, following functionalization. Titanium disks were acid etched to create micropits on the surface. Micro-nano-hybrid surfaces were created by depositioning 300-nm diameter TiO(2) nodules onto the micropits using a previously established self-assembly protocol. These disks were stored for 8 weeks in the dark to allow sufficient aging, then treated with UV light for 48 hours. Rat bone marrow-derived osteoblasts were cultured on fresh disks (immediately after UV treatment), 3-day-old disks (disks stored for 3 days after UV treatment), and 7-day- old disks. The rates of cell attachment, spread, proliferation, and levels of alkaline phosphatase activity, and calcium deposition were reduced by 30%-50% on micropit surfaces, depending on the age of the titanium. In contrast, 7-day-old hybrid surfaces maintained equivalent levels of bioactivity compared with the fresh surfaces. Both micropit and micro-nano-hybrid surfaces were superhydrophilic immediately after UV treatment. However, after 7 days, the micro-nano- hybrid surfaces became hydrorepellent, while the micropit surfaces remained hydrophilic. The sustained bioactivity levels of the micro-nano-hybrid surfaces were nullified by treating these surfaces with Cl(-)anions. A thin TiO(2) coating on the micropit surface without the formation of nanonodules did not result in the prevention or alleviation of the time-dependent decrease in biological activity. In conclusion, the micro-nano-hybrid titanium surfaces may slow the rate of time-dependent degradation of titanium

  12. TiO2 micro-nano-hybrid surface to alleviate biological aging of UV-photofunctionalized titanium.

    PubMed

    Iwasa, Fuminori; Tsukimura, Naoki; Sugita, Yoshihiko; Kanuru, Rajita Kodali; Kubo, Katsutoshi; Hasnain, Hafiz; Att, Wael; Ogawa, Takahiro

    2011-01-01

    Bioactivity and osteoconductivity of titanium degrade over time after surface processing. This time-dependent degradation is substantial and defined as the biological aging of titanium. UV treatment has shown to reactivate the aged surfaces, a process known as photofunctionalization. This study determined whether there is a difference in the behavior of biological aging for titanium with micro-nano-hybrid topography and titanium with microtopography alone, following functionalization. Titanium disks were acid etched to create micropits on the surface. Micro-nano-hybrid surfaces were created by depositioning 300-nm diameter TiO(2) nodules onto the micropits using a previously established self-assembly protocol. These disks were stored for 8 weeks in the dark to allow sufficient aging, then treated with UV light for 48 hours. Rat bone marrow-derived osteoblasts were cultured on fresh disks (immediately after UV treatment), 3-day-old disks (disks stored for 3 days after UV treatment), and 7-day- old disks. The rates of cell attachment, spread, proliferation, and levels of alkaline phosphatase activity, and calcium deposition were reduced by 30%-50% on micropit surfaces, depending on the age of the titanium. In contrast, 7-day-old hybrid surfaces maintained equivalent levels of bioactivity compared with the fresh surfaces. Both micropit and micro-nano-hybrid surfaces were superhydrophilic immediately after UV treatment. However, after 7 days, the micro-nano- hybrid surfaces became hydrorepellent, while the micropit surfaces remained hydrophilic. The sustained bioactivity levels of the micro-nano-hybrid surfaces were nullified by treating these surfaces with Cl(-)anions. A thin TiO(2) coating on the micropit surface without the formation of nanonodules did not result in the prevention or alleviation of the time-dependent decrease in biological activity. In conclusion, the micro-nano-hybrid titanium surfaces may slow the rate of time-dependent degradation of titanium

  13. Proposition of an Accelerated Ageing Method for Natural Fibre/Polylactic Acid Composite

    NASA Astrophysics Data System (ADS)

    Zandvliet, Clio; Bandyopadhyay, N. R.; Ray, Dipa

    2015-10-01

    Natural fibre composite based on polylactic acid (PLA) composite is of special interest because it is entirely from renewable resources and biodegradable. Some samples of jute/PLA composite and PLA alone made 6 years ago and kept in tropical climate on a shelf shows too fast ageing degradation. In this work, an accelerated ageing method for natural fibres/PLA composite is proposed and tested. Experiment was carried out with jute and flax fibre/PLA composite. The method was compared with the standard ISO 1037-06a. The residual flexural strength after ageing test was compared with the one of common wood-based panels and of real aged samples prepared 6 years ago.

  14. Analysis of the mechanical and thermal properties of jute and glass fiber as reinforcement epoxy hybrid composites.

    PubMed

    Braga, R A; Magalhaes, P A A

    2015-11-01

    This work describes the study to investigate and compare the mechanical and thermal properties of raw jute and glass fiber reinforced epoxy hybrid composites. To improve the mechanical properties, jute fiber was hybridized with glass fiber. Epoxy resin, jute and glass fibers were laminated in three weight ratios (69/31/0, 68/25/7 and 64/18/19) respectively to form composites. The tensile, flexural, impact, density, thermal and water absorption tests were carried out using hybrid composite samples. This study shows that the addition of jute fiber and glass fiber in epoxy, increases the density, the impact energy, the tensile strength and the flexural strength, but decreases the loss mass in function of temperature and the water absorption. Morphological analysis was carried out to observe fracture behavior and fiber pull-out of the samples using scanning electron microscope.

  15. Analysis of the mechanical and thermal properties of jute and glass fiber as reinforcement epoxy hybrid composites.

    PubMed

    Braga, R A; Magalhaes, P A A

    2015-11-01

    This work describes the study to investigate and compare the mechanical and thermal properties of raw jute and glass fiber reinforced epoxy hybrid composites. To improve the mechanical properties, jute fiber was hybridized with glass fiber. Epoxy resin, jute and glass fibers were laminated in three weight ratios (69/31/0, 68/25/7 and 64/18/19) respectively to form composites. The tensile, flexural, impact, density, thermal and water absorption tests were carried out using hybrid composite samples. This study shows that the addition of jute fiber and glass fiber in epoxy, increases the density, the impact energy, the tensile strength and the flexural strength, but decreases the loss mass in function of temperature and the water absorption. Morphological analysis was carried out to observe fracture behavior and fiber pull-out of the samples using scanning electron microscope. PMID:26249589

  16. Influence of weave structures on the tribological properties of hybrid Kevlar/PTFE fabric composites

    NASA Astrophysics Data System (ADS)

    Gu, Dapeng; Yang, Yulin; Qi, Xiaowen; Deng, Wei; Shi, Lei

    2012-09-01

    The existing research of the woven fabric self-lubricating liner mainly focus on the tribological performance improvements and the service life raised by changing different fiber type combinations, adding additive modification, and performing fiber surface modification. As fabric composites, the weave structures play an important role in the mechanical and tribological performances of the liners. However, hardly any literature is available on the friction and wear behavior of such composites with different weave structures. In this paper, three weave structures (plain, twill 1/3 and satin 8/5) of hybrid Kevlar/PTFE fabric composites are selected and pin-on-flat linear reciprocating wear studies are done on a CETR tester under different pressures and different frequencies. The relationship between the tensile strength and the wear performance are studied. The morphologies of the worn surfaces under the typical test conditions are analyzed by means of scanning electron microscopy (SEM). The analysis results show that at 10 MPa, satin 8/5 performs the best in friction-reduction and antiwear performance, and plain is the worst. At 30 MPa, however, the antiwear performance is reversed and satin 8/5 does not even complete the 2 h wear test at 16 Hz. There is no clear evidence proving that the tensile strength has an influence on the wear performance. So the different tribological performance of the three weave structures of fabric composites may be attributed to the different PTFE proportions in the fabric surface and the different wear mechanisms. The fabric composites are divided into three regions: the lubrication region, the reinforced region and the bonding region. The major mechanisms are fatigue wear and the shear effects of the friction force in the lubrication region. In the reinforced region fiber-matrix de-bonding and fiber breakage are involved. The proposed research proposes a regional wear model and further indicates the wear process and the wear mechanism

  17. Environmental aging degradation in continuous fiber ceramic composites

    SciTech Connect

    Plucknett, K.P.; Lin, H.T.; Braski, D.N.; Becher, P.F.

    1995-12-31

    The thermal stability of two-continuous fiber ceramic composites (CFCC`s) has been assessed. A Nicalon/CaO-Al{sub 2}O{sub 3}-SiO{sub 2} (CAS) glass-ceramic composite has been subjected to unstressed, oxidation heat treatments between 375 and 1200{degrees}C, after which the material was tested in flexure at room temperature. The static fatigue behavior of a chemical vapor infiltrated (CVI) Nicalon/SiC ceramic matrix composite has been assessed in air, between 425 and 1150{degrees}C, both with and without protective seal coating. Severe property degradation was observed due to oxidation of the graphite fiber/matrix interlayer in both CFCC`s.

  18. Effect of different polishing systems on the surface roughness of nano-hybrid composites

    PubMed Central

    Patel, Brijesh; Chhabra, Naveen; Jain, Disha

    2016-01-01

    Objective: The study aimed to investigate the influence of different polishing systems on the surface roughness of nano-hybrid composite resins. Background: Different shapes of polishing systems are available according to the site of work. To minimize variability, a new system with single shape is developed that can be utilized in both anterior as well as posterior teeth. Materials and Methods: Seventy composite discs were fabricated using Teflon well (10 mm × 3 mm). Two main group of nano-hybrid composite Group I — Filtek Z350 and Group II — Tetric N-Ceram were used (n = 35 for each group). Both groups were further divided into four subgroups. Subgroup a — OneGloss (n = 10), Subgroup b - PoGo (n = 10), Subgroup c — Sof-Lex spiral (n = 10), Subgroup d - Mylar strip (control, n = 5). Samples were polished according to the manufacturer's recommendations. Surface roughness test was performed using contact profilometer. The obtained data were analyzed using the one-way analysis of variance test. Result: Tetric N-Ceram produced smoother surfaces than Filtek Z350 (P < 0.05). Mylar strip and “PoGo” created equally smooth surfaces, while significantly rougher surfaces were obtained after applications of “Sof-Lex spiral” and “OneGloss” (P < 0.05). Conclusion: Polishing ability of Tetric N-Ceram is better than Filtek Z350 XT. “PoGo” seems to be a better polishing system than “OneGloss” and “Sof-Lex Spiral.” PMID:26957791

  19. High-precision CTE measurement of hybrid C/SiC composite for cryogenic space telescopes

    NASA Astrophysics Data System (ADS)

    Enya, K.; Yamada, N.; Imai, T.; Tange, Y.; Kaneda, H.; Katayama, H.; Kotani, M.; Maruyama, K.; Naitoh, M.; Nakagawa, T.; Onaka, T.; Suganuma, M.; Ozaki, T.; Kume, M.; Krödel, M. R.

    2012-01-01

    This paper presents highly precise measurements of thermal expansion of a "hybrid" carbon-fiber reinforced silicon carbide composite, HB-Cesic® - a trademark of ECM, in the temperature region of ˜310-10 K. Whilst C/SiC composites have been considered to be promising for the mirrors and other structures of space-borne cryogenic telescopes, the anisotropic thermal expansion has been a potential disadvantage of this material. HB-Cesic® is a newly developed composite using a mixture of different types of chopped, short carbon-fiber, in which one of the important aims of the development was to reduce the anisotropy. The measurements indicate that the anisotropy was much reduced down to 4% as a result of hybridization. The thermal expansion data obtained are presented as functions of temperature using eighth-order polynomials separately for the horizontal (XY-) and vertical (Z-) directions of the fabrication process. The average CTEs and their dispersion (1σ) in the range 293-10 K derived from the data for the XY- and Z-directions were 0.805 ± 0.003 × 10-6 K-1 and 0.837 ± 0.001 × 10-6 K-1, respectively. The absolute accuracy and the reproducibility of the present measurements are suggested to be better than 0.01 × 10-6 K-1 and 0.001 × 10-6 K-1, respectively. The residual anisotropy of the thermal expansion was consistent with our previous speculation regarding carbon-fiber, in which the residual anisotropy tended to lie mainly in the horizontal plane.

  20. Hybrid carbon fiber/carbon nanotube composites for structural damping applications.

    PubMed

    Tehrani, M; Safdari, M; Boroujeni, A Y; Razavi, Z; Case, S W; Dahmen, K; Garmestani, H; Al-Haik, M S

    2013-04-19

    Carbon nanotubes (CNTs) were grown on the surface of carbon fibers utilizing a relatively low temperature synthesis technique; graphitic structures by design (GSD). To probe the effects of the synthesis protocols on the mechanical properties, other samples with surface grown CNTs were prepared using catalytic chemical vapor deposition (CCVD). The woven graphite fabrics were thermally shielded with a thin film of SiO2 and CNTs were grown on top of this film. Raman spectroscopy and electron microscopy revealed the grown species to be multi-walled carbon nanotubes (MWCNTs). The damping performance of the hybrid CNT-carbon fiber-reinforced epoxy composite was examined using dynamic mechanical analysis (DMA). Mechanical testing confirmed that the degradations in the strength and stiffness as a result of the GSD process are far less than those encountered through using the CCVD technique and yet are negligible compared to the reference samples. The DMA results indicated that, despite the minimal degradation in the storage modulus, the loss tangent (damping) for the hybrid composites utilizing GSD-grown MWCNTs improved by 56% compared to the reference samples (based on raw carbon fibers with no surface treatment or surface grown carbon nanotubes) over the frequency range 1-60 Hz. These results indicated that the energy dissipation in the GSD-grown MWCNTs composite can be primarily attributed to the frictional sliding at the nanotube/epoxy interface and to a lesser extent to the stiff thermal shielding SiO2 film on the fiber/matrix interface. PMID:23518871

  1. FT-IR Photoacoustic Spectroscopy Applied to the Curing and Aging of Composites

    NASA Astrophysics Data System (ADS)

    Jones, Roger W.; Sweterlitsch, Jeffrey J.; Wagner, Anthony J.; McClelland, John F.; Hsu, David K.; Polis, Daniel L.; Sovinski, Marjorie F.

    2005-04-01

    Fourier-transform infrared photoacoustic spectroscopy has been applied to carbon-fiber composites to test whether bulk physical properties of the composites could be determined using the near-surface-sensitive photoacoustic approach. Both the cure levels of carbon fiber/cyanate ester composites and the interlaminar shear strengths of artificially aged carbon fiber/epoxy composites were successfully measured. Standard errors of cross validation were 3.46% cure for a sample set ranging from 8% to 95% cured and 1.60 MPa for aged samples with strengths ranging from 22 to 77 MPa.

  2. Some Exploitation Properties of Wood Plastic Hybrid Composites Based on Polypropylene and Plywood Production Waste

    NASA Astrophysics Data System (ADS)

    Kajaks, Janis; Kalnins, Karlis; Uzulis, Sandris; Matvejs, Juris

    2015-12-01

    polypropylenewood hybrid composites (WPHC) physical-mechanical and other exploitation properties.

  3. The effects of stress and physical aging on the creep compliance of a polymeric composite

    NASA Technical Reports Server (NTRS)

    Gates, Thomas E.; Feldman, Mark

    1993-01-01

    An experimental study was performed to determine the effects of stress and physical aging on the matrix dominated viscoelastic properties of IM7/8320, a high temperature fiber reinforced thermoplastic composite. Established creep/aging test techniques developed for polymers were adapted for testing of the composite material. The transverse and shear compliance for an orthotropic plate were found from creep compliance measurements at constant, sub-Tg temperatures. These compliance terms were shown to be effected by physical aging. Aging time shift factors and shift rates were found to be a function of applied stress.

  4. Hybrid composites of calcium phosphate granules, fibrin glue, and bone marrow for skeletal repair.

    PubMed

    Le Nihouannen, Damien; Goyenvalle, Eric; Aguado, Eric; Pilet, Paul; Bilban, Melitta; Daculsi, Guy; Layrolle, Pierre

    2007-05-01

    Synthetic bone substitutes, such as calcium phosphate ceramics, give good results in clinical applications. In order to adapt to surgical sites, bioceramics come in the form of blocks or granules, and are either dense or porous. Combining these bioceramics with fibrin glue provides a mouldable and self-hardening composite biomaterial with the biochemical properties of each component. Critical-sized defects in the femoral condyle of rabbits were filled with TricOs/fibrin glue/bone marrow hybrid/composite material. The TricOs granules (1-2 mm) were composed of hydroxyapatite and beta tricalcium phosphate (60/40 in weight). The fibrin glue was composed of fibrinogen, thrombin and other biological factors and mixed with MBCP granules either simultaneously or sequentially. Bone marrow was also added to the MBCP/fibrin composite prior to filling the defects. After 3, 6, 12, and 24 weeks of implantation, the newly-formed bone was analysed with histology, histomorphometry and mechanical tests. The newly-formed bone had grown centripetally. Simultaneous application of fibrin glue showed better results for mechanical properties than sequential application after 6 weeks. Around 40% of bone had formed after 24 weeks in the three groups. Although the addition of bone marrow did not improve bone formation, the MBCP/fibrin material could be used in clinical bone filling applications. PMID:17117470

  5. Influence of Sea Water Aging on the Mechanical Behaviour of Acrylic Matrix Composites

    NASA Astrophysics Data System (ADS)

    Davies, P.; Le Gac, P.-Y.; Le Gall, M.

    2016-07-01

    A new matrix resin was recently introduced for composite materials, based on acrylic resin chemistry allowing standard room temperature infusion techniques to be used to produce recyclable thermoplastic composites. This is a significant advance, particularly for more environmentally-friendly production of large marine structures such as boats. However, for such applications it is essential to demonstrate that composites produced with these resins resist sea water exposure in service. This paper presents results from a wet aging study of unreinforced acrylic and glass and carbon fibre reinforced acrylic composites. It is shown that the acrylic matrix resin is very stable in seawater, showing lower property losses after seawater aging than those of a commonly-used epoxy matrix resin. Carbon fibre reinforced acrylic also shows good property retention after aging, while reductions in glass fibre reinforced composite strengths suggest that specific glass fibre sizing may be required for optimum durability.

  6. Dependence of SERS enhancement on the chemical composition and structure of Ag/Au hybrid nanoparticles.

    PubMed

    Chaffin, Elise; O'Connor, Ryan T; Barr, James; Huang, Xiaohua; Wang, Yongmei

    2016-08-01

    Noble metal nanoparticles (NPs) such as silver (Ag) and gold (Au) have unique plasmonic properties that give rise to surface enhanced Raman scattering (SERS). Generally, Ag NPs have much stronger plasmonic properties and, hence, provide stronger SERS signals than Au NPs. However, Ag NPs lack the chemical stability and biocompatibility of comparable Au NPs and typically exhibit the most intense plasmonic resonance at wavelengths much shorter than the optimal spectral region for many biomedical applications. To overcome these issues, various experimental efforts have been devoted to the synthesis of Ag/Au hybrid NPs for the purpose of SERS detections. However, a complete understanding on how the SERS enhancement depends on the chemical composition and structure of these nanoparticles has not been achieved. In this study, Mie theory and the discrete dipole approximation have been used to calculate the plasmonic spectra and near-field electromagnetic enhancements of Ag/Au hybrid NPs. In particular, we discuss how the electromagnetic enhancement depends on the mole fraction of Au in Ag/Au alloy NPs and how one may use extinction spectra to distinguish between Ag/Au alloyed NPs and Ag-Au core-shell NPs. We also show that for incident laser wavelengths between ∼410 nm and 520 nm, Ag/Au alloyed NPs provide better electromagnetic enhancement than pure Ag, pure Au, or Ag-Au core-shell structured NPs. Finally, we show that silica-core Ag/Au alloy shelled NPs provide even better performance than pure Ag/Au alloy or pure solid Ag and pure solid Au NPs. The theoretical results presented will be beneficial to the experimental efforts in optimizing the design of Ag/Au hybrid NPs for SERS-based detection methods. PMID:27497571

  7. Dependence of SERS enhancement on the chemical composition and structure of Ag/Au hybrid nanoparticles

    NASA Astrophysics Data System (ADS)

    Chaffin, Elise; O'Connor, Ryan T.; Barr, James; Huang, Xiaohua; Wang, Yongmei

    2016-08-01

    Noble metal nanoparticles (NPs) such as silver (Ag) and gold (Au) have unique plasmonic properties that give rise to surface enhanced Raman scattering (SERS). Generally, Ag NPs have much stronger plasmonic properties and, hence, provide stronger SERS signals than Au NPs. However, Ag NPs lack the chemical stability and biocompatibility of comparable Au NPs and typically exhibit the most intense plasmonic resonance at wavelengths much shorter than the optimal spectral region for many biomedical applications. To overcome these issues, various experimental efforts have been devoted to the synthesis of Ag/Au hybrid NPs for the purpose of SERS detections. However, a complete understanding on how the SERS enhancement depends on the chemical composition and structure of these nanoparticles has not been achieved. In this study, Mie theory and the discrete dipole approximation have been used to calculate the plasmonic spectra and near-field electromagnetic enhancements of Ag/Au hybrid NPs. In particular, we discuss how the electromagnetic enhancement depends on the mole fraction of Au in Ag/Au alloy NPs and how one may use extinction spectra to distinguish between Ag/Au alloyed NPs and Ag-Au core-shell NPs. We also show that for incident laser wavelengths between ˜410 nm and 520 nm, Ag/Au alloyed NPs provide better electromagnetic enhancement than pure Ag, pure Au, or Ag-Au core-shell structured NPs. Finally, we show that silica-core Ag/Au alloy shelled NPs provide even better performance than pure Ag/Au alloy or pure solid Ag and pure solid Au NPs. The theoretical results presented will be beneficial to the experimental efforts in optimizing the design of Ag/Au hybrid NPs for SERS-based detection methods.

  8. Dependence of SERS enhancement on the chemical composition and structure of Ag/Au hybrid nanoparticles.

    PubMed

    Chaffin, Elise; O'Connor, Ryan T; Barr, James; Huang, Xiaohua; Wang, Yongmei

    2016-08-01

    Noble metal nanoparticles (NPs) such as silver (Ag) and gold (Au) have unique plasmonic properties that give rise to surface enhanced Raman scattering (SERS). Generally, Ag NPs have much stronger plasmonic properties and, hence, provide stronger SERS signals than Au NPs. However, Ag NPs lack the chemical stability and biocompatibility of comparable Au NPs and typically exhibit the most intense plasmonic resonance at wavelengths much shorter than the optimal spectral region for many biomedical applications. To overcome these issues, various experimental efforts have been devoted to the synthesis of Ag/Au hybrid NPs for the purpose of SERS detections. However, a complete understanding on how the SERS enhancement depends on the chemical composition and structure of these nanoparticles has not been achieved. In this study, Mie theory and the discrete dipole approximation have been used to calculate the plasmonic spectra and near-field electromagnetic enhancements of Ag/Au hybrid NPs. In particular, we discuss how the electromagnetic enhancement depends on the mole fraction of Au in Ag/Au alloy NPs and how one may use extinction spectra to distinguish between Ag/Au alloyed NPs and Ag-Au core-shell NPs. We also show that for incident laser wavelengths between ∼410 nm and 520 nm, Ag/Au alloyed NPs provide better electromagnetic enhancement than pure Ag, pure Au, or Ag-Au core-shell structured NPs. Finally, we show that silica-core Ag/Au alloy shelled NPs provide even better performance than pure Ag/Au alloy or pure solid Ag and pure solid Au NPs. The theoretical results presented will be beneficial to the experimental efforts in optimizing the design of Ag/Au hybrid NPs for SERS-based detection methods.

  9. Age and composition of igneous rocks, Edna Mountain quadrangle, Humboldt County, Nevada

    USGS Publications Warehouse

    Erickson, Ralph L.; Silberman, Miles L.; Marsh, S.P.

    1978-01-01

    Six pulses of igneous activity ranging in age from Jurassic to Pliocene have been identified in the Edna Mountain quadrangle, Humboldt County, Nev. Porphyritic syenite am! quartz monzonite of Jurassic age (146-164 million years) at Buffalo Mountain are highly potassic through a wide range in SiO2 content from olivine-bearing syenite to quartz-rich monzonite, and their composition contrasts sharply with plutons elsewhere in north-central Nevada. Granodiorite and quartz monzonite plutons of Cretaceous age (88- 106 m.y.) are chemically and mineralogically similar to other calc-alkaline plutons in north-central Nevada. Four episodes of Tertiary volcanism include rhyolite ashflow tuffs and slightly younger andesitic basalt flows and tuffs of Oligocene age, rhyolite vitrophyre of late Miocene age, and olivine basalt flows of Pliocene age. Their age and mineralogical and chemical compositions are similar to other Tertiary volcanic rocks in north-central Nevada.

  10. Effect of nanocomposite composition on shear and elongational rheological behavior of PLA/MMT hybrids

    NASA Astrophysics Data System (ADS)

    Garofalo, Emilia; Scarfato, Paola; Di Maio, Luciano; Incarnato, Loredana

    2014-05-01

    The present work focuses on the possibility of conveniently tuning materials in PLA based nanocomposites in order to improve their processability in manufacturing processes where extensional flow is mainly involved. Nanocomposites at a constant silicate loading were produced by melt compounding, using a commercial polylactide grade (PLA 4032D) and two different organo-silicates (Cloisite 30B and Nanofil SE3010). A morphological characterization in solid and molten state, realized by TEM investigations and shear rheological measurements, firstly pointed out the influence of composition on the nanostructure of the hybrid systems. All the samples were then submitted to uniaxial stretching and the rheological response of the different nanocomposites was correlated to the initial nanostructure and the different polymer-clay affinity.

  11. Shear-lag analysis of a hybrid, unidirectional composite with fiber damage

    NASA Technical Reports Server (NTRS)

    Goree, J. G.; Dharani, L. R.

    1983-01-01

    Development of a method of analysis capable of predicting accurately the fracture behavior of unidirectional hybrid (buffer strip) composite laminates was studied. Three particular solutions are discussed in detail: broken fibers in a unidirectional half-plane; adjoined half planes of different fiber and matrix properties; and the solution of two half planes bounding a third distinct region of finite width. This finite width region represents a buffer strip and primary attention is given to the potential of this strip to arrest a crack that originates in one of the half planes. A materials modeling approach using the classical shear lag assumption to describe the stress transfer between fibers was analyzed. Explicit fiber and matrix properties of the three regions are retained, and changes in the laminate behavior as a function of the relative material properties, buffer strip width, and initial crack length are discussed.

  12. Magnetic composites based on hybrid spheres of aluminum oxide and superparamagnetic nanoparticles of iron oxides

    NASA Astrophysics Data System (ADS)

    Braga, Tiago P.; Vasconcelos, Igor F.; Sasaki, José M.; Fabris, J. D.; de Oliveira, Diana Q. L.; Valentini, Antoninho

    2010-03-01

    Materials containing hybrid spheres of aluminum oxide and superparamagnetic nanoparticles of iron oxides were obtained from a chemical precursor prepared by admixing chitosan and iron and aluminum hydroxides. The oxides were first characterized with scanning electron microscopy, X-ray diffraction, and Mössbauer spectroscopy. Scanning electron microscopy micrographs showed the size distribution of the resulting spheres to be highly homogeneous. The occurrence of nano-composites containing aluminum oxides and iron oxides was confirmed from powder X-ray diffraction patterns; except for the sample with no aluminum, the superparamagnetic relaxation due to iron oxide particles were observed from Mössbauer spectra obtained at 298 and 110 K; the onset six line-spectrum collected at 20 K indicates a magnetic ordering related to the blocking relaxation effect for significant portion of small spheres in the sample with a molar ratio Al:Fe of 2:1.

  13. Structural Acoustic Response of a Shape Memory Alloy Hybrid Composite Panel (Lessons Learned)

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.

    2002-01-01

    This study presents results from an effort to fabricate a shape memory alloy hybrid composite (SMAHC) panel specimen and test the structure for dynamic response and noise transmission characteristics under the action of thermal and random acoustic loads. A method for fabricating a SMAHC laminate with bi-directional SMA reinforcement is described. Glass-epoxy unidirectional prepreg tape and Nitinol ribbon comprise the material system. Thermal activation of the Nitinol actuators was achieved through resistive heating. The experimental hardware required for mechanical support of the panel/actuators and for establishing convenient electrical connectivity to the actuators is presented. Other experimental apparatus necessary for controlling the panel temperature and acquiring structural acoustic data are also described. Deficiency in the thermal control system was discovered in the process of performing the elevated temperature tests. Discussion of the experimental results focuses on determining the causes for the deficiency and establishing means for rectifying the problem.

  14. Hybrid composite laminates reinforced with Kevlar/carbon/glass woven fabrics for ballistic impact testing.

    PubMed

    Randjbaran, Elias; Zahari, Rizal; Jalil, Nawal Aswan Abdul; Majid, Dayang Laila Abang Abdul

    2014-01-01

    Current study reported a facile method to investigate the effects of stacking sequence layers of hybrid composite materials on ballistic energy absorption by running the ballistic test at the high velocity ballistic impact conditions. The velocity and absorbed energy were accordingly calculated as well. The specimens were fabricated from Kevlar, carbon, and glass woven fabrics and resin and were experimentally investigated under impact conditions. All the specimens possessed equal mass, shape, and density; nevertheless, the layers were ordered in different stacking sequence. After running the ballistic test at the same conditions, the final velocities of the cylindrical AISI 4340 Steel pellet showed how much energy was absorbed by the samples. The energy absorption of each sample through the ballistic impact was calculated; accordingly, the proper ballistic impact resistance materials could be found by conducting the test. This paper can be further studied in order to characterise the material properties for the different layers.

  15. Mechanical properties of hybrid (medium modulus graphite, Thornel P-55 Kevlar/Epoxy) composites

    SciTech Connect

    Raghava, R.S.; Peters, S.T.

    1987-01-01

    This paper treats the mechanical behavior of hybrid (Thornel P-55-Kevlar/Epoxy) composites under ambient conditions and under hostile environments. Interply (core/shell) and intraply tubes (5.75'' I.D.) were filament wound and NOL rings were machined from them. Apparently modulus and apparent strength were measured using the split D (ASTM D2290) test. The influence of boiling water exposure (2 hrs and 24 hrs) on short beam shear strength, apparent modulus, and apparent strength was also evaluated at room temperature and the fracture toughness for above configurations was measured at room temperature. Scanning electron microscopy was used to examine failure modes. 6 references, 4 figures, 3 tables.

  16. Fabrication of alumina filled hybrid buckypaper composites and their enhancement of microwave absorbing performance

    NASA Astrophysics Data System (ADS)

    Miao, Hsin-Yuan; Liu, Jih-Hsin; Saravanan, L.

    2015-06-01

    Alumina (Al2O3)-filled multiwalled carbon nanotube buckypapers (BPs) with different Al2O3 loadings (5-50 wt%) were successfully synthesised. Structural and morphological analysis performed with x-ray diffraction and field-emission scanning electron microscopy, respectively, confirmed the presence of stable α-phase Al2O3 particles in the Al2O3-BP composites. The formation of flexible Al2O3-BP hybrid nanocomposites (5-15 wt%) was attributed to the strong interfacial polarisation and high conductivity; compared with pure Al2O3 and BP. The nanocomposites with optimised alumina loadings demonstrated enhanced microwave absorption (>90%) and a broader absorption bandwidth in the investigated high-frequency region.

  17. Effect of Impact Damage and Open Hole on Compressive Strength of Hybrid Composite Laminates

    NASA Technical Reports Server (NTRS)

    Hiel, Clement; Brinson, H. F.

    1993-01-01

    Impact damage tolerance is a frequently listed design requirement for composites hardware. The effect of impact damage and open hole size on laminate compressive strength was studied on sandwich beam specimens which combine CFRP-GFRP hybrid skins and a syntactic foam core. Three test specimen configurations have been investigated for this study. The first two were sandwich beams which were loaded in pure bending (by four point flexure). One series had a skin damaged by impact, and the second series had a circular hole machined through one of the skins. The reduction of compressive strength with increasing damage (hole) size was compared. Additionally a third series of uniaxially loaded open hole compression coupons were tested to generate baseline data for comparison with both series of sandwich beams.

  18. Hybrid Composite Laminates Reinforced with Kevlar/Carbon/Glass Woven Fabrics for Ballistic Impact Testing

    PubMed Central

    Randjbaran, Elias; Zahari, Rizal; Abdul Jalil, Nawal Aswan; Abang Abdul Majid, Dayang Laila

    2014-01-01

    Current study reported a facile method to investigate the effects of stacking sequence layers of hybrid composite materials on ballistic energy absorption by running the ballistic test at the high velocity ballistic impact conditions. The velocity and absorbed energy were accordingly calculated as well. The specimens were fabricated from Kevlar, carbon, and glass woven fabrics and resin and were experimentally investigated under impact conditions. All the specimens possessed equal mass, shape, and density; nevertheless, the layers were ordered in different stacking sequence. After running the ballistic test at the same conditions, the final velocities of the cylindrical AISI 4340 Steel pellet showed how much energy was absorbed by the samples. The energy absorption of each sample through the ballistic impact was calculated; accordingly, the proper ballistic impact resistance materials could be found by conducting the test. This paper can be further studied in order to characterise the material properties for the different layers. PMID:24955400

  19. Effect of Impact Damage and Open Hole on Compressive Strength of Hybrid Composite Laminates

    SciTech Connect

    Hiel, C.; Brinson, H.F.

    1993-05-01

    Impact damage tolerance is a frequently listed design requirement for composites hardware. The effect of impact damage and open hole size on laminate compressive strength was studied on sandwich beam specimens which combine CFRP-GFRP hybrid skins and a syntactic foam core. Three test specimen configurations have been investigated for this study. The first two were sandwich beams which were loaded in pure bending (by four point flexure). One series had a skin damaged by impact, and the second series had a circular hole machined through one of the skins. The reduction of compressive strength with increasing damage (hole) size was compared. Additionally a third series of uniaxially loaded open hole compression coupons were tested to generate baseline data for comparison with both series of sandwich beams.

  20. Bioinspired synthesis of fluorescent calcium carbonate/carbon dot hybrid composites.

    PubMed

    Guo, Shanshan; Yang, Miao; Chen, Min; Zhang, Juan; Liu, Kang; Ye, Ling; Gu, Wei

    2015-05-01

    Herein, we report a novel method to synthesise fluorescent calcium carbonate/carbon dots (CaCO3/CDs) by simply mixing CaCl2 and Na2CO3 solutions in the presence of CDs. There are two roles of CDs in this easy and cost-effective biomimetic strategy, that is as the template to direct the formation and assembly of calcite nanocrystals into hierarchical spheres with diameters in the range of 200-300 nm and simultaneously as the phosphor to enable the CaCO3 to emit blue fluorescence under UV (365 nm) irradiation with a quantum yield of 56.2%. The CaCO3/CD hybrid composites possessing unique fluorescence properties are potentially useful in various applications.

  1. Composit, Nanoparticle-Based Anode material for Li-ion Batteries Applied in Hybrid Electric (HEV's)

    SciTech Connect

    Dr. Malgorzata Gulbinska

    2009-08-24

    Lithium-ion batteries are promising energy storage devices in hybrid and electric vehicles with high specific energy values ({approx}150 Wh/kg), energy density ({approx}400 Wh/L), and long cycle life (>15 years). However, applications in hybrid and electric vehicles require increased energy density and improved low-temperature (<-10 C) performance. Silicon-based anodes are inexpensive, environmentally benign, and offer excellent theoretical capacity values ({approx}4000 mAh/g), leading to significantly less anode material and thus increasing the overall energy density value for the complete battery (>500 Wh/L). However, tremendous volume changes occur during cycling of pure silicon-based anodes. The expansion and contraction of these silicon particles causes them to fracture and lose electrical contact to the current collector ultimately severely limiting their cycle life. In Phase I of this project Yardney Technical Products, Inc. proposed development of a carbon/nano-silicon composite anode material with improved energy density and silicon's cycleability. In the carbon/nano-Si composite, silicon nanoparticles were embedded in a partially-graphitized carbonaceous matrix. The cycle life of anode material would be extended by decreasing the average particle size of active material (silicon) and by encapsulation of silicon nanoparticles in a ductile carbonaceous matrix. Decreasing the average particle size to a nano-region would also shorten Li-ion diffusion path and thus improve rate capability of the silicon-based anodes. Improved chemical inertness towards PC-based, low-temperature electrolytes was expected as an additional benefit of a thin, partially graphitized coating around the active electrode material.

  2. Long-term water-aging of whisker-reinforced polymer-matrix composites.

    PubMed

    Xu, H H K

    2003-01-01

    Long-term water exposure may degrade polymer-matrix composites. This study investigated the water-aging of whisker composites. It was hypothesized that whiskers would provide stable and substantial reinforcement, and that whisker type would affect water-aging resistance. Silica-fused Si(3)N(4) and SiC whiskers were incorporated into a resin. The specimens were tested by three-point flexure and nano-indentation vs. water-aging for 1 to 730 days. After 730 days, SiC composite had a strength (mean +/- SD; n = 6) of 185 +/- 33 MPa, similar to 146 +/- 44 MPa for Si(3)N(4) composite (p = 0.064); both were significantly higher than 67 +/- 23 MPa for an inlay/onlay control (p < 0.001). Compared with 1 day, the strength of the SiC composite showed no decrease, while that of the Si(3)N(4) composite decreased. The decrease was due to whisker weakening rather than to resin degradation or interface breakdown. Whisker composites also had higher moduli than the controls. In conclusion, silica-fused whiskers bonded to polymer matrix and resisted long-term water attack, resulting in much stronger composites than the controls after water-aging.

  3. Proteomic Analysis Reveals Different Involvement of Embryo and Endosperm Proteins during Aging of Yliangyou 2 Hybrid Rice Seeds

    PubMed Central

    Zhang, Ying-Xue; Xu, Heng-Heng; Liu, Shu-Jun; Li, Ni; Wang, Wei-Qing; Møller, Ian M.; Song, Song-Quan

    2016-01-01

    Seed aging is a process that results in a delayed germination, a decreased germination percentage, and finally a total loss of seed viability. However, the mechanism of seed aging is poorly understood. In the present study, Yliangyou 2 hybrid rice (Oryza sativa L.) seeds were artificially aged at 100% relative humidity and 40°C, and the effect of artificial aging on germination, germination time course and the change in protein profiles of embryo and endosperm was studied to understand the molecular mechanism behind seed aging. With an increasing duration of artificial aging, the germination percentage and germination rate of hybrid rice seeds decreased. By comparing the protein profiles from the seeds aged for 0, 10 and 25 days, a total of 91 and 100 protein spots were found to show a significant change of more than 2-fold (P < 0.05) in abundance, and 71 and 79 protein spots were identified, in embryos and endosperms, respectively. The great majority of these proteins increased in abundance in embryos (95%) and decreased in abundance in endosperms (99%). In embryos, most of the identified proteins were associated with energy (30%), with cell defense and rescue (28%), and with storage protein (18%). In endosperms, most of the identified proteins were involved in metabolism (37%), in energy (27%), and in protein synthesis and destination (11%). The most marked change was the increased abundance of many glycolytic enzymes together with the two fermentation enzymes pyruvate decarboxylase and alcohol dehydrogenase in the embryos during aging. We hypothesize that the decreased viability of hybrid rice seeds during artificial aging is caused by the development of hypoxic conditions in the embryos followed by ethanol accumulation. PMID:27708655

  4. Age-related changes in hematology and plasma chemistry values of hybrid striped bass (Morone chrysops X Morone saxatilis).

    PubMed

    Hrubec, Terry C.; Smith, Stephen A.; Robertson, John L.

    2001-01-01

    Hybrid striped bass (Morone chrysops X Morone saxatilis ) are an important aquaculture species yet there are few diagnostic tools available to assess their health. Hematology and clinical chemistry analyses are not used extensively in fish medicine due to the lack of reference intervals for various fish species, and because factors such as age can affect blood values. There is little published information regarding age-related changes in blood values of juvenile fish. It is important to evaluate juvenile fish, as this is the time they are raised in aquaculture settings. Determining age-related changes in the blood values of fishes would further develop clinical pathology as a diagnostic tool, enhancing both fish medicine and the aquaculture industry. The results of standard hematology and clinical chemistry analysis were evaluated in juvenile hybrid striped bass at 4, 6, 9, 15, and 19 months of age. Values for PCV and RBC indices were significantly lower, and plasma protein concentration was significantly higher in younger fish. Total WBC and lymphocyte counts were significantly higher in fish at 6 and 9 months of age, while neutrophil and monocyte counts were higher at 6, 9, and 15 months. Eosinophil counts were significantly higher in 9-month-old fish. The majority of hematologic values fell within previously established reference intervals, indicating that only slight modification to the intervals is necessary for evaluating hematologic results of hybrid striped bass at different ages. The following analytes deviated sufficiently from adult reference intervals to warrant separate reference values: plasma protein concentration at 4 months, WBC and lymphocyte counts at 15 and 19 months, and thrombocyte-like-cells at 9 months of age. Values for most biochemical analytes were significantly different among age groups except for creatinine and potassium concentrations. Comparisons with reference intervals were not made for biochemical analytes, because established

  5. Essential oil composition of Citrus meyerii Y. Tan. and Citrus medica L. cv. Diamante and their lemon hybrids.

    PubMed

    Verzera, Antonella; Trozzi, Alessandra; Zappalá, Mario; Condurso, Cettina; Cotroneo, Antonella

    2005-06-15

    In this paper we report the volatile fraction composition of Citrus meyerii Y. Tan. and Citrus medica L. cv. Diamante and two new lemon hybrids obtained by cross-breeding them with the tetraploid Citrus limon Burm. cv. Cavone. Both parent and hybrid oils were laboratory-extracted from the peel fruits and analyzed by HRGC-MS and HRGC-FID. Sixty-three components were fully characterized by mass spectra, linear retention indices, and injection of standards. The average composition as single components for all the oils analyzed is reported. Moreover, the data obtained were statistically analyzed. Since limonene is by far the main component of all the essential oils examined, analysis of variance and multivariate analysis gave interesting information on the similarities and differences between the oils analyzed. The new hybrid oils analyzed have potential commercial value because they could be an acceptable alternative to the valuable lemon oil.

  6. Material Degradation during Isothermal Aging and Thermal Cycling of Hybrid Mica Seal with Ag Interlayer under SOFC Exposure Conditions

    SciTech Connect

    Chou, Y. S.; Stevenson, Jeffry W.; Hardy, John S.; Singh, Prabhakar

    2006-11-01

    Hybrid phlogopite mica seals with silver interlayers were evaluated in terms of materials degradation in a combined isothermal ageing and thermal cycling test. The hybrid mica seal was composed of a phlogopite mica paper sandwiched between two Ag foils. The hybrid micas were first aged at 800oC for ~1,000 hrs in a moist, dilute hydrogen fuel (~2.7% H2/bal. Ar + ~3% H2O), followed by short-term thermal cycling between ~100oC and 800oC. The combined test was repeated for 3 times for a total of 4,000 hrs ageing at 800oC and 119 thermal cycles. The results of high temperature leak rate tests showed very good thermal stability and thermal cycle stability with 800oC leak rates of ~0.02-0.03 sccm/cm. A hybrid mica seal tested in a high water content fuel (30 v% H2O/70 v% H2) demonstrated similar leakage during isothermal ageing and subsequent thermal cycles. Post-mortem analyses showed no extensive reaction between Ag and phlogopite mica as well as no significant mica degradation. Simple calculations to estimate the effect of measured leakage on the open circuit voltage and the total fuel loss for various SOFC stack sizes suggest very small fuel losses for the current hybrid mica seals, indicating that they are good candidates for SOFC sealing applications. Corresponding author: Yeong-Shyung Chou Tel: 509-375-2527, Fax: 509-375-2186, E-mail: yeong-shyung.chou@pnl.gov

  7. Hypoxia affects performance traits and body composition of juvenile hybrid striped bass (Morone chrysops x M. saxatilis)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Performance traits and body composition of juvenile hybrid striped bass (Morone chrysops x M. saxatilis) in response to hypoxia were evaluated in replicate tanks maintained at constant dissolved oxygen concentrations that averaged 23.0 +/- 2.3%, 39.7 +/- 3.0%, and 105.5 +/- 9.5% dissolved oxygen sat...

  8. Variability in fatty acid and triacylglycerol composition of the oil of coconut (Cocos nucifera L.) hybrids and their parentals.

    PubMed

    Laureles, Lucita R; Rodriguez, Felicito M; Reaño, Consorcia E; Santos, Gerardo A; Laurena, Antonio C; Mendoza, Evelyn Mae Tecson

    2002-03-13

    The fatty acid profiles and triacylglycerol (TAG) compositions of oils from the solid endosperm of different Philippine coconut hybrids and their parentals were determined by using gas chromatography (GC) and high-performance liquid chromatography (HPLC). In general, varietal differences in fatty acid composition were observed. Lauric acid (C12) content was significantly higher in the hybrids PCA 15-8 (50.45%) and PCA 15-9 (50.26%) by about 3.16% points as compared to other hybrids, and higher in Tacunan Green Dwarf (50.50%) among the parentals. Among the fatty acids, lauric acid exhibited the least variation. In general, none of the hybrids had higher fatty acid content than their parentals. The HPLC chromatogram of triacylglycerols (TAG) showed 8 major peaks which differ in carbon number (CN) by two: identified as TAG CN 30, 32, 34, 36, 38, 40, 42, and 44. TAGs CN 30 (4.08%) and CN 34 (19.20%) were found to be significantly higher in PCA 15-9 than in the other hybrids. CN 36 was highest (21.94-23.66%) in all hybrids and parentals. The TAG CNs varied significantly among hybrids and parents, i.e., in CN 30, 32, and 34, which are high in medium chain triacylglycerols (MCTs), and in CN 30 (for parentals only), 40, 42, and 44 (the latter two for parentals only), and none in CN 36. MCTs calculated for two hybrids and their parents ranged from 13.81% to 20.55%.

  9. Effects of real-time thermal aging on graphite/polyimide composites

    NASA Technical Reports Server (NTRS)

    Haskins, J. F.; Kerr, J. R.

    1985-01-01

    As part of a program to evaluate high-temperature advanced composites for use on supersonic cruise transport aircraft, two graphite/polyimide composites have been aged at elevated temperatures for times up to 5.7 years. Work on the first, HT-S/710 graphite/polyimide, was started in 1974. Evaluation of the second polyimide, Celion 6000/LARC-160, began in 1980. Baseline properties are presented, including unnotched and notched tensile data as a function of temperature, compression, flexure, shear, and constant-amplitude fatigue data at R = 0.1 and R = -1. Tensile specimens were aged in ovens where pressure and aging temperatures were controlled for various times up to and including 50,000 hours. Changes in tensile strength were determined and plotted as a function of aging time. The HT-S/710 composite aged at 450 F and 550 F if compared to the Celion 6000/LARC-160 composite aged at 350 F and 450 F. After tensile testing, many of the thermal aging specimens were examined using a scanning electron microscope. Results of these studies are presented, and changes in properties and degradation mechanisms during high-temperature aging are discussed and illustrated using metallographic techniques.

  10. Evaluation of the bond strength between aged composite cores and luting agent

    PubMed Central

    2015-01-01

    PURPOSE The aim of this study was to evaluate effect of different surface treatment methods on the bond strength between aged composite-resin core and luting agent. MATERIALS AND METHODS Seventy-five resin composites and also seventy-five zirconia ceramic discs were prepared. 60 composite samples were exposed to thermal aging (10,000 cycles, 5 to 55℃) and different surface treatment. All specimens were separated into 5 groups (n=15): 1) Intact specimens 2) Thermal aging-air polishing 3) Thermal aging- Er:YAG laser irradiation 4) Thermal aging- acid etching 5) Thermal-aging. All specimens were bonded to the zirconia discs with resin cement and fixed to universal testing machine and bond strength testing loaded to failure with a crosshead speed of 0.5 mm/min. The fractured surface was classified as adhesive failure, cohesive failure and adhesive-cohesive failure. The bond strength data was statistically compared by the Kruskal-Wallis method complemented by the Bonferroni correction Mann-Whitney U test. The probability level for statistical significance was set at α=.05. RESULTS Thermal aging and different surface treatment methods have significant effect on the bond strength between composite-resin cores and luting-agent (P<.05). The mean baseline bond strength values ranged between 7.07 ± 2.11 and 26.05 ± 6.53 N. The highest bond strength of 26.05 ± 6.53 N was obtained with Group 3. Group 5 showed the lowest value of bond strength. CONCLUSION Appropriate surface treatment method should be applied to aged composite resin cores or aged-composites restorations should be replaced for the optimal bond strength and the clinical success. PMID:25932308

  11. Sea Water Ageing of GFRP Composites and the Dissolved salts

    NASA Astrophysics Data System (ADS)

    Chakraverty, A. P.; Mohanty, U. K.; Mishra, S. C.; Satapathy, A.

    2015-02-01

    This paper houses the effect of sea water immersion on glass fibre reinforced polymer (GFRP) composites. The major sources of interest are study of sea water absorption, penetration of the dissolved salts, details of chemical and physical bonds at the interface, variations of mechanical properties and study of failure mechanisms as revealed through SEM fractographs. Eighteen ply GFRP composites are immersed in sea water for a period of one year in steps of two months durations. It is revealed that the moisture absorption transforms from a Fickian to non-Fickian behavior with lapse of time. The dissolved salt 'K' shows highest depth of penetration after one year of immersion while 'Na' shows a least depth of penetration, as revealed from the EDS spectra. It is also revealed that 'Ca' seems to have a sudden burst in the rate of penetration even surpassing that of 'K'. This trend can be attributed to the combined effect of ionic mobility of the various dissolved salts and the probable interaction between 'K' and the -OH group of epoxy resin. This interaction between dissolved 'K' and the -OH group in the polymer could have arrested the further advancement of 'K' salts in the polymer, resulting in comparatively high rates of 'Ca' penetration. The mechanical properties such as inter laminar shear stress (ILSS), stress and strain at rupture, glass transition temperature (Tg) and elastic modulus show a decreasing trend with the increased duration of immersion. As revealed from the SEM fractographs pot- holing, fiber pull-out, matrix crack etc. are seen to be the major reason for failure of the immersed samples under load.

  12. Effects of different polishing methods on color stability of resin composites after accelerated aging.

    PubMed

    Sirin Karaarslan, Emine; Bulbul, Mehmet; Yildiz, Esma; Secilmis, Asli; Sari, Fatih; Usumez, Aslihan

    2013-01-01

    The purpose of this study was to evaluate the effect of polishing procedures on the color stability of different types of composites after aging. Forty disk-shaped specimens (Ø10×2 mm) were prepared for each composite resin type (an ormocer, a packable, a nanohybrid, and a microhybrid) for a total of 160 specimens. Each composite group was divided into four subgroups according to polishing method (n=10): control (no finishing and polishing), polishing disk, polishing wheel, and glaze material. Color parameters (L*, a*, and b*) and surface roughness were measured before and after accelerated aging. Of the polishing methods, glazed specimens showed the lowest color change (∆E*), ∆L*, and ∆b* values (p<0.05). Of the composite resins, the microhybrid composite showed the lowest ∆E* value, whereas the ormocer showed the highest (p<0.05). For all composite types, the surface roughness of their control groups decreased after aging (p<0.05). In conclusion, all composite resins showed color changes after accelerated aging, with the use of glaze material resulting in the lowest color change.

  13. Hybrid-Wing-Body Vehicle Composite Fuselage Analysis and Case Study

    NASA Technical Reports Server (NTRS)

    Mukhopadhyay, Vivek

    2014-01-01

    Recent progress in the structural analysis of a Hybrid Wing-Body (HWB) fuselage concept is presented with the objective of structural weight reduction under a set of critical design loads. This pressurized efficient HWB fuselage design is presently being investigated by the NASA Environmentally Responsible Aviation (ERA) project in collaboration with the Boeing Company, Huntington Beach. The Pultruded Rod-Stiffened Efficient Unitized Structure (PRSEUS) composite concept, developed at the Boeing Company, is approximately modeled for an analytical study and finite element analysis. Stiffened plate linear theories are employed for a parametric case study. Maximum deflection and stress levels are obtained with appropriate assumptions for a set of feasible stiffened panel configurations. An analytical parametric case study is presented to examine the effects of discrete stiffener spacing and skin thickness on structural weight, deflection and stress. A finite-element model (FEM) of an integrated fuselage section with bulkhead is developed for an independent assessment. Stress analysis and scenario based case studies are conducted for design improvement. The FEM model specific weight of the improved fuselage concept is computed and compared to previous studies, in order to assess the relative weight/strength advantages of this advanced composite airframe technology

  14. Biosensor based on polyaniline-Prussian Blue/multi-walled carbon nanotubes hybrid composites.

    PubMed

    Zou, Yongjin; Sun, Li-Xian; Xu, Fen

    2007-05-15

    In this work, a novel route for fabrication polyaniline (PANI)-Prussian Blue (PB) hybrid composites is proposed by the spontaneous redox reaction in the FeCl(3)-K(3)[Fe(CN)(6)] and the aniline solution. With the introduction of multi-walled carbon nanotubes (MWNTs), the PANI-PB/MWNTs system shows synergy between the PANI-PB and MWNTs which amplified the H(2)O(2) sensitivity greatly. A linear range from 8 x1 0(-8) to 1 x 10(-5)M and a high sensitivity 508.1 8 microA microM cm(2) for H(2)O(2) detection are obtained. The composites also show good stability in neutral solution. A glucose biosensor was further constructed by immobilizing glucose oxidase (GOD) with Nafion and glutaraldehyde on the electrode surface. The performance factors influencing the resulted biosensor were studied in detail. The biosensor exhibits excellent response performance to glucose with the linear range from 1 to 11 mM and a detection limit of 0.01 mM. Furthermore, the biosensor shows rapid response, high sensitivity, good reproducibility, long-term stability and freedom of interference from other co-existing electroactive species. PMID:17141494

  15. Analysis of SMA Hybrid Composite Structures in MSC.Nastran and ABAQUS

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.; Patel, Hemant D.

    2005-01-01

    A thermoelastic constitutive model for shape memory alloy (SMA) actuators and SMA hybrid composite (SMAHC) structures was recently implemented in the commercial finite element codes MSC.Nastran and ABAQUS. The model may be easily implemented in any code that has the capability for analysis of laminated composite structures with temperature dependent material properties. The model is also relatively easy to use and requires input of only fundamental engineering properties. A brief description of the model is presented, followed by discussion of implementation and usage in the commercial codes. Results are presented from static and dynamic analysis of SMAHC beams of two types; a beam clamped at each end and a cantilever beam. Nonlinear static (post-buckling) and random response analyses are demonstrated for the first specimen. Static deflection (shape) control is demonstrated for the cantilever beam. Approaches for modeling SMAHC material systems with embedded SMA in ribbon and small round wire product forms are demonstrated and compared. The results from the commercial codes are compared to those from a research code as validation of the commercial implementations; excellent correlation is achieved in all cases.

  16. Design, fabrication, and testing of a SMA hybrid composite jet engine chevron

    NASA Astrophysics Data System (ADS)

    Turner, Travis L.; Cabell, Randolph H.; Cano, Roberto J.; Fleming, Gary A.

    2006-03-01

    Control of jet noise continues to be an important research topic. Exhaust nozzle chevrons have been shown to reduce jet noise, but parametric effects are not well understood. Additionally, thrust loss due to chevrons at cruise suggests significant benefit from deployable chevrons. The focus of this study is development of an active chevron concept for the primary purpose of parametric studies for jet noise reduction in the laboratory and technology development to leverage for full scale systems. The active chevron concept employed in this work consists of a laminated composite structure with embedded shape memory alloy (SMA) actuators, termed a SMA hybrid composite (SMAHC). The actuators are embedded on one side of the middle surface such that thermal excitation generates a moment and deflects the structure. A brief description of the chevron design is given followed by details of the fabrication approach. Results from bench top tests are presented and correlated with numerical predictions from a model for such structures that was recently implemented in MSC.Nastran and ABAQUS. Excellent performance and agreement with predictions is demonstrated. Results from tests in a representative flow environment are also presented. Excellent performance is again achieved for both open- and closed-loop tests, the latter demonstrating control to a specified immersion into the flow. The actuation authority and immersion performance is shown to be relatively insensitive to nozzle pressure ratio (NPR). Very repeatable immersion control with modest power requirements is demonstrated.

  17. Measurement and Prediction of the Thermomechanical Response of Shape Memory Alloy Hybrid Composite Beams

    NASA Technical Reports Server (NTRS)

    Davis, Brian; Turner, Travis L.; Seelecke, Stefan

    2005-01-01

    Previous work at NASA Langley Research Center (LaRC) involved fabrication and testing of composite beams with embedded, pre-strained shape memory alloy (SMA) ribbons within the beam structures. That study also provided comparison of experimental results with numerical predictions from a research code making use of a new thermoelastic model for shape memory alloy hybrid composite (SMAHC) structures. The previous work showed qualitative validation of the numerical model. However, deficiencies in the experimental-numerical correlation were noted and hypotheses for the discrepancies were given for further investigation. The goal of this work is to refine the experimental measurement and numerical modeling approaches in order to better understand the discrepancies, improve the correlation between prediction and measurement, and provide rigorous quantitative validation of the numerical analysis/design tool. The experimental investigation is refined by a more thorough test procedure and incorporation of higher fidelity measurements such as infrared thermography and projection moire interferometry. The numerical results are produced by a recently commercialized version of the constitutive model as implemented in ABAQUS and are refined by incorporation of additional measured parameters such as geometric imperfection. Thermal buckling, post-buckling, and random responses to thermal and inertial (base acceleration) loads are studied. The results demonstrate the effectiveness of SMAHC structures in controlling static and dynamic responses by adaptive stiffening. Excellent agreement is achieved between the predicted and measured results of the static and dynamic thermomechanical response, thereby providing quantitative validation of the numerical tool.

  18. Design, fabrication, and testing of a SMA hybrid composite jet engine chevron

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.; Cabell, Randolph H.; Cano, Roberto J.; Fleming, Gary A.

    2006-01-01

    Control of jet noise continues to be an important research topic. Exhaust nozzle chevrons have been shown to reduce jet noise, but parametric effects are not well understood. Additionally, thrust loss due to chevrons at cruise suggests significant benefit from deployable chevrons. The focus of this study is development of an active chevron concept for the primary purpose of parametric studies for jet noise reduction in the laboratory and technology development to leverage for full scale systems. The active chevron concept employed in this work consists of a laminated composite structure with embedded shape memory alloy (SMA) actuators, termed a SMA hybrid composite (SMAHC). The actuators are embedded on one side of the middle surface such that thermal excitation generates a moment and deflects the structure. A brief description of the chevron design is given followed by details of the fabrication approach. Results from bench top tests are presented and correlated with numerical predictions from a model for such structures that was recently implemented in MSC.Nastran and ABAQUS. Excellent performance and agreement with predictions is demonstrated. Results from tests in a representative flow environment are also presented. Excellent performance is again achieved for both open- and closed-loop tests, the latter demonstrating control to a specified immersion into the flow. The actuation authority and immersion performance is shown to be relatively insensitive to nozzle pressure ratio (NPR). Very repeatable immersion control with modest power requirements is demonstrated.

  19. Spin-triplet electron transport in hybrid superconductor heterostructures with a composite ferromagnetic interlayer

    NASA Astrophysics Data System (ADS)

    Sheyerman, A. E.; Constantinian, K. Y.; Ovsyannikov, G. A.; Kislinskii, Yu. V.; Shadrin, A. V.; Kalabukhov, A. V.; Khaydukov, Yu. N.

    2015-06-01

    Hybrid YBa2Cu3O7 - x /SrRuO3/La0.7Sr0.3MnO3/Au-Nb superconductor mesastructures with a composite manganite-ruthenate ferromagnetic interlayer are studied using electrophysical, magnetic, and microwave methods. The supercurrent in the mesastructure is observed when the interlayer thickness is much larger than the coherence length of ferromagnetic materials. The peak on the dependence of the critical current density on the interlayer material thickness corresponds to the coherence length, which is in qualitative agreement with theoretical predictions for a system with spit-triplet superconducting correlations. The magnetic-field dependence of the critical current is determined by penetration of magnetic flux quanta and by the magnetic domain structure, as well as by the field dependence of disorientation of the magnetization vectors of the layers in the composite magnetic interlayer. It is found that the supercurrent exists in magnetic fields two orders of magnitude stronger than the field corresponding to entry of a magnetic flux quantum into the mesastructure. The current-phase relation (CPR) of the supercurrent of mesastructures is investigated upon a change in the magnetic field from zero to 30 Oe; the ratio of the second CPR harmonic to the first, determined from the dependence of the Shapiro steps on the microwave radiation amplitude, does not exceed 50%.

  20. Spin-triplet electron transport in hybrid superconductor heterostructures with a composite ferromagnetic interlayer

    SciTech Connect

    Sheyerman, A. E. Constantinian, K. Y.; Ovsyannikov, G. A.; Kislinskii, Yu. V.; Shadrin, A. V.; Kalabukhov, A. V.; Khaydukov, Yu. N.

    2015-06-15

    Hybrid YBa{sub 2}Cu{sub 3}O{sub 7−x}/SrRuO{sub 3}/La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/Au-Nb superconductor mesastructures with a composite manganite-ruthenate ferromagnetic interlayer are studied using electrophysical, magnetic, and microwave methods. The supercurrent in the mesastructure is observed when the interlayer thickness is much larger than the coherence length of ferromagnetic materials. The peak on the dependence of the critical current density on the interlayer material thickness corresponds to the coherence length, which is in qualitative agreement with theoretical predictions for a system with spit-triplet superconducting correlations. The magnetic-field dependence of the critical current is determined by penetration of magnetic flux quanta and by the magnetic domain structure, as well as by the field dependence of disorientation of the magnetization vectors of the layers in the composite magnetic interlayer. It is found that the supercurrent exists in magnetic fields two orders of magnitude stronger than the field corresponding to entry of a magnetic flux quantum into the mesastructure. The current-phase relation (CPR) of the supercurrent of mesastructures is investigated upon a change in the magnetic field from zero to 30 Oe; the ratio of the second CPR harmonic to the first, determined from the dependence of the Shapiro steps on the microwave radiation amplitude, does not exceed 50%.

  1. Preparation and characterization of functional material based on hybrid polymer composites

    NASA Astrophysics Data System (ADS)

    Agusu, La; Amiruddin; Taswito, Chen Chen; Herdianto; Zamrun, Muh.

    2016-08-01

    The microstructures and properties of hybrid polymer composites based on polyaniline (PANi)/γ-Fe2O3 nanoparticles/TiO2/carbon have been investigated for multifunctional applications such as heavy metal removal and initial study for radar absorbing material application. γ-Fe2O3 nanoparticles with spherical shape were synthetized by a coprecipitation method from iron sand. By activating the polyethylene glycol (PEG-400) coated carbon of coconut shell, the homogenous shape and size of carbon was achieved. Then, γ- Fe2O3, TiO2, and carbon were mixed with PANi by an in situ polymerization method at low temperature 0-5 oC. Characterization process involved XRD, SEM, FTIR, VSM, and DC conductivity measurements. For radar absorber application, the functionalized polymer composites showed good electrical conductivity 0.45 S/cm to absorb the incoming electromagnetic energy. An efficient and effective reduction of Pb2+ ion from the water has been achieved by using this material.

  2. Classroom Age Composition and Vocabulary Development Among At-Risk Preschoolers

    PubMed Central

    Guo, Ying; Tompkins, Virginia; Justice, Laura; Petscher, Yaacov

    2016-01-01

    Research Findings The purpose of this exploratory study was to examine the relationship between classroom age composition and preschoolers’ vocabulary gains over an academic year and also to examine whether these relations were moderated by classroom quality. In this study (N = 130 children in 16 classrooms representing a subset of all children enrolled in these classrooms), results showed a significant cross-level interaction between classroom age composition and children’s age, suggesting positive effects of greater variance in classroom age composition for younger but not older children. The interaction between behavior management (1 dimension of classroom quality) and classroom age composition was also significant, indicating that a wider distribution of classroom age composition was positively related to children’s vocabulary gains within classrooms characterized by better behavior management. Practice or Policy Findings underscore the importance of children’s social interactions with more knowledgeable conversational partners in promoting their vocabulary development and signify the need to help teachers learn how to manage children’s behaviors so as to provide a classroom that is optimal for child learning.

  3. The effect of environmental aging on the fracture toughness of dental composites.

    PubMed

    Pilliar, R M; Vowles, R; Williams, D F

    1987-03-01

    The effect of aging four commercially-available dental composites in water or ethanol at 37 degrees C for periods of up to 28 days was assessed by measuring changes in the materials' plane-strain fracture toughness (KIC). The results, obtained by means of a mini Short Rod Fracture Toughness Test specimen design, suggest that while water aging does not produce significant changes in KIC, aging in ethanol does cause significant increases in fracture toughness for three of the four dental composites studied. In view of previously-reported loss of wear resistance for dental composites aged in ethanol solutions, the present study emphasizes the difficulties in using fracture toughness to predict wear properties.

  4. Continuous Carbon Nanotube-Ultrathin Graphite Hybrid Foams for Increased Thermal Conductivity and Suppressed Subcooling in Composite Phase Change Materials.

    PubMed

    Kholmanov, Iskandar; Kim, Jaehyun; Ou, Eric; Ruoff, Rodney S; Shi, Li

    2015-12-22

    Continuous ultrathin graphite foams (UGFs) have been actively researched recently to obtain composite materials with increased thermal conductivities. However, the large pore size of these graphitic foams has resulted in large thermal resistance values for heat conduction from inside the pore to the high thermal conductivity graphitic struts. Here, we demonstrate that the effective thermal conductivity of these UGF composites can be increased further by growing long CNT networks directly from the graphite struts of UGFs into the pore space. When erythritol, a phase change material for thermal energy storage, is used to fill the pores of UGF-CNT hybrids, the thermal conductivity of the UGF-CNT/erythritol composite was found to increase by as much as a factor of 1.8 compared to that of a UGF/erythritol composite, whereas breaking the UGF-CNT bonding in the hybrid composite resulted in a drop in the effective room-temperature thermal conductivity from about 4.1 ± 0.3 W m(-1) K(-1) to about 2.9 ± 0.2 W m(-1) K(-1) for the same UGF and CNT loadings of about 1.8 and 0.8 wt %, respectively. Moreover, we discovered that the hybrid structure strongly suppresses subcooling of erythritol due to the heterogeneous nucleation of erythritol at interfaces with the graphitic structures.

  5. Continuous Carbon Nanotube-Ultrathin Graphite Hybrid Foams for Increased Thermal Conductivity and Suppressed Subcooling in Composite Phase Change Materials.

    PubMed

    Kholmanov, Iskandar; Kim, Jaehyun; Ou, Eric; Ruoff, Rodney S; Shi, Li

    2015-12-22

    Continuous ultrathin graphite foams (UGFs) have been actively researched recently to obtain composite materials with increased thermal conductivities. However, the large pore size of these graphitic foams has resulted in large thermal resistance values for heat conduction from inside the pore to the high thermal conductivity graphitic struts. Here, we demonstrate that the effective thermal conductivity of these UGF composites can be increased further by growing long CNT networks directly from the graphite struts of UGFs into the pore space. When erythritol, a phase change material for thermal energy storage, is used to fill the pores of UGF-CNT hybrids, the thermal conductivity of the UGF-CNT/erythritol composite was found to increase by as much as a factor of 1.8 compared to that of a UGF/erythritol composite, whereas breaking the UGF-CNT bonding in the hybrid composite resulted in a drop in the effective room-temperature thermal conductivity from about 4.1 ± 0.3 W m(-1) K(-1) to about 2.9 ± 0.2 W m(-1) K(-1) for the same UGF and CNT loadings of about 1.8 and 0.8 wt %, respectively. Moreover, we discovered that the hybrid structure strongly suppresses subcooling of erythritol due to the heterogeneous nucleation of erythritol at interfaces with the graphitic structures. PMID:26529570

  6. In vitro and in vivo toxicity of rinsed and aged nanocellulose-polypyrrole composites.

    PubMed

    Ferraz, Natalia; Strømme, Maria; Fellström, Bengt; Pradhan, Sulena; Nyholm, Leif; Mihranyan, Albert

    2012-08-01

    Novel composites of nanocellulose and the conducting polymer polypyrrole (PPy) are herein suggested as potential candidates for active ion-extraction membranes in electrochemically controlled hemodialysis. This study has defined processing parameters to obtain a biocompatible nanocellulose-PPy composite, and for the first time, the effect of the composite aging on cell viability has been studied. The influence of rinsing and extraction process steps, as well as aging under different conditions (i.e. in air, at -20°C and in argon), on the electroactivity and cytotoxicity of a PPy-nanocellulose composite has been investigated. The biocompatibility evaluation was based on indirect toxicity assays with fibroblasts and monocyte cell lines and an acute toxicity test in mice, while the electroactivity was evaluated by cyclic voltammetry experiments. The as-prepared composite did not induce any cytotoxic response in vitro or in vivo. Extensive rinsing and 48 h incubation in biological buffer previous to the preparation of the culture medium extracts were, however, necessary to obtain a noncytotoxic composite. The as-prepared composite was also found to exhibit acceptable electrochemical performance, which was retained upon 4 weeks storage in argon atmosphere. It was shown that aging of the composite had a negative effect on biocompatibility, regardless of the storage condition. Thus, to allow for longtime storage of electroactive nanocellulose-PPy hemodialysis membranes, the degradation of PPy upon storage must be controlled. The present results show that the biocompatibility of PPy composites depends on the rinsing and pretreatment of the composite material as well as the aging of the material.

  7. Tailoring plant lipid composition: designer oilseeds come of age.

    PubMed

    Napier, Johnathan A; Graham, Ian A

    2010-06-01

    Plant neutral lipids such as seed oil triacylglycerols play a key role in many aspects of human life, ranging from providing essential nutrition to acting as biolubricants. There is also growing interest in using plant oils as a replacement for petrochemicals, either for fuel or as a chemical feedstock. Considerable effort has been focused on modifying the fatty acid composition of seed oils and/or increasing the levels of storage triacylglycerol. Certainly, it is now possible to successfully modify the profile of plant oils via transgenic metabolic engineering to generate something approaching a 'designer oil'. This is specifically true for the accumulation of omega-3 long chain polyunsaturated fatty acids that now stand at levels equivalent to those found in native marine organisms. However, it is equally clear that a holistic understanding of plant lipid metabolism is still lacking, mainly owing to the continually emerging complexity and interplay between pathways, recently exemplified by the identification of the ROD1 phosphatidylcholine:diacylglycerol cholinephosphotransferase involved in the channelling of unsaturated fatty acids into storage oil. The new approaches and outcomes described here will inform new paradigms and hasten the arrival of truly predictive biology in this vital field.

  8. An Introduced Hybrid Graphene/Polyaniline Composites for Improvement of Supercapacitor

    NASA Astrophysics Data System (ADS)

    Tayel, Mazhar B.; Soliman, Moataz M.; Ebrahim, Shaker; Harb, Mohamed E.

    2016-01-01

    Supercapacitors represent an attractive alternative for portable electronics and automotive applications due to their high capacitance, specific power and extended life. In fact, the growing demand of portable systems and hybrid electric vehicles, memory protection in complementary metal-oxide-semiconductor (CMOS), logic circuit, videocassette recorders (VCRs), compact disc (CD) players, personal computers (PCs), uninterruptible power supply (UPS) in security alarm systems, remote sensing, smoke detectors, etc. require high power in short-term pulses. Therefore, in the last 20 years, supercapacitors have been required for the development of large and small devices driven by electrical power. In this paper, graphene oxide (GO) was synthesized by improved Hummers method. Two polyaniline (PANI)/graphene oxide nanocomposites electrode materials were prepared from aniline, GO and ammoniumpersulfate (APS) by in situ chemical polymerization with the mass ratios (mGO:mAniline) 10:90 and 30: 70 in ice bath. The crystal structure and the surface topography of all materials were characterized by means of x-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), Raman spectroscopy and scanning electron microscopy (SEM). The electrochemical properties of the composites were evaluated by cyclic voltammetry (CV), charge-discharge measurements and electrical impedance spectroscopy (EIS), respectively. The results show that the composites have similar and enhanced cyclic voltammetry performance compared with pure PANI based electrode material. The graphene/PANI composite synthesized with the mass ratio (mANI:mGO) 90:10 possessed good capacitive behavior with a specific capacitance as high as 1509.35 F/g at scan rate of 1 mV/s in scanning potential window from -0.8 V to 0.8 V.

  9. Effect of acidic solutions on the surface degradation of a micro-hybrid composite resin.

    PubMed

    Münchow, Eliseu A; Ferreira, Ana Cláudia A; Machado, Raissa M M; Ramos, Tatiana S; Rodrigues-Junior, Sinval A; Zanchi, Cesar H

    2014-01-01

    Composite resins may undergo wear by the action of chemical substances (e.g., saliva, alcohol, bacterial acids) of the oral environment, which may affect the material's structure and surface properties. This study evaluated the effect of acidic substances on the surface properties of a micro-hybrid composite resin (Filtek Z-250). Eighty specimens were prepared, and baseline hardness and surface roughness (KMN0 and Ra0, respectively) were measured. The specimens were subjected to sorption (SO) and solubility (SL) tests according to ISO 4049:2009, but using different storage solutions: deionized water; 75/25 vol% ethanol/water solution; lactic acid; propionic acid; and acetic acid. The acids were used in two concentrations: PA and 0.02 N. pH was measured for all solutions and final hardness (KMN1) and surface roughness (Ra1) were measured. Data were analyzed with paired t-tests and one-way ANOVA and Tukey's test (a=5%). All solutions decreased hardness and increased the Ra values, except for the specimens stored in water and 0.02 N lactic acid, which maintained the hardness. All solutions produced similar SO and SL phenomena, except for the 0.02 N lactic acid, which caused lower solubility than the other solutions. Ethanol showed the highest pH (6.6) and the 0.02 N lactic acid the lowest one (2.5). The solutions affected negatively the surface properties of the composite resin; in addition, an acidic pH did not seem to be a significant factor that intensifies the surface degradation phenomena. PMID:25250496

  10. Investigation of mechanical properties of modern dental composites after artificial aging for one year.

    PubMed

    Hahnel, Sebastian; Henrich, Anne; Bürgers, Ralf; Handel, Gerhard; Rosentritt, Martin

    2010-01-01

    This in vitro study investigated the aging behavior of dental composites with regard to surface roughness (SR), Vickers hardness (VH) and flexural strength (FS), and the study elucidated the impact of artificial aging parameters. One hundred and sixty-five rectangular specimens were prepared from five composites (Filtek Supreme XT, Filtek Silorane, CeramX, Quixfil, experimental ormocer) and subjected to various artificial aging protocols (storage in distilled water/ethanol/artificial saliva for 7, 90 and 365 days; thermal cycling, 2 x 3000 cycles 5/55 degrees C). SR, VH and FS were determined at baseline and after each aging treatment. Means and standard deviations were calculated; statistical analysis was performed using three-way ANOVA and the Tukey-Kramer multiple comparison test (alpha=.05). The results showed a significant influence in the composite and aging duration on mechanical parameters; the aging medium did not have a significant influence on VH and FS, but there was a significant influence on SR. The highest overall VH was found for theexperimental ormocer; Filtek Silorane yielded the lowest values. For FS, the significantly highest values were found for Filtek Silorane, and the lowest values were found for the experimental ormocer. Prolonged aging periods (90 or 365 days) or thermal cycling led to significant decreases in both VH and FS and significant increases in SR. The findings of the current study indicate that composites differ significantly for SR and its mechanical properties with regard to FS and VH, as well as in aging behavior. Generally, artificial aging leads to a significant decrease in mechanical properties, which underlines the relevance of continuous improvement of dental composites.

  11. Effect of in vivo loading on bone composition varies with animal age

    PubMed Central

    Aido, Marta; Kerschnitzki, Michael; Hoerth, Rebecca; Checa, Sara; Spevak, Lyudmila; Boskey, Adele; Fratzl, Peter; Duda, Georg N.; Wagermaier, Wolfgang; Willie, Bettina M.

    2015-01-01

    Loading can increase bone mass and size and this response is reduced with aging. It is unclear, however how loading affects bone mineral and matrix properties. Fourier Transform Infrared Imaging and high resolution synchrotron scanning small angle X-ray scattering were used to study how bone’s microscale and nanoscale compositional properties were altered in the tibial midshaft of young, adult, and elderly female C57Bl/6J mice after two weeks of controlled in vivo compressive loading in comparison to physiological loading. The effect of controlled loading on bone composition varied with animal age, since it predominantly influenced the bone composition of elderly mice. Interestingly, controlled loading led to enhanced collagen maturity in elderly mice. In addition, although the rate of bone formation was increased by controlled loading based on histomorphometry, the newly formed tissue had similar material quality to new bone tissue formed during physiological loading. Similar to previous studies, our data showed that bone composition was animal and tissue age dependent during physiological loading. The findings that the new tissue formed in response to controlled loading and physiological loading had similar bone composition and that controlled loading enhanced bone composition in elderly mice further supports the use of physical activity as a noninvasive treatment to enhance bone quality as well as maintain bone mass in individuals suffering from age-related bone loss. PMID:25639943

  12. Surface and interface properties of carbon fiber composites under cyclical aging

    NASA Astrophysics Data System (ADS)

    Lv, Xinying; Wang, Rongguo; Liu, Wenbo; Jiang, Long

    2011-10-01

    Carbon fiber-reinforced BMI composites have been subjected to combination accelerated aging comprising a hygrothermal process, a thermal-oxidative process, and a freezing process in order to simulate their responses under complicated service environments. This cyclical condition, including the freezing process, has not been investigated by other researchers so far. The effects of this combination accelerated aging on the mechanical properties have been characterized by FTIR, SEM/EDXA, XRD, and moisture-uptake determination. The results indicated that combination accelerated aging had great effects on the mechanical properties of the composite, the network structure of the BMI matrix, and the moisture uptake by the composite. After a third cycle of accelerated aging, moisture reached the center layer of the composite and as a result led to an obvious decrease in ILSS due to deterioration of the carbon fiber-BMI interface. Sufficient moisture absorption on the composite surface made the network structure of the BMI matrix more open, which facilitated stress relaxation and the creation of micro-cracks, with a consequent obvious decrease in flexural strength. With increasing number of combined-action accelerated aging cycles, ever more moisture was absorbed during each hygrothermal process due to the plasticizing effect of water, and micro-cracks propagated as a result of internal stresses caused by the hygrothermal process, the thermal-oxidative process, and the freezing process of each cycle. XRD analysis indicated that moisture penetrated through the amorphous region of the BMI matrix.

  13. Learning Science in Small Multi-Age Groups: The Role of Age Composition

    ERIC Educational Resources Information Center

    Kallery, Maria; Loupidou, Thomais

    2016-01-01

    The present study examines how the overall cognitive achievements in science of the younger children in a class where the students work in small multi-age groups are influenced by the number of older children in the groups. The context of the study was early-years education. The study has two parts: The first part involved classes attended by…

  14. Environmental Aging of Scotch-Weld(TradeMark) AF-555M Structural Adhesive in Composite to Composite Bonds

    NASA Technical Reports Server (NTRS)

    Hou, Tan-Hung; Miner, Gilda A.; Lowther, Sharon E.; Connell, John W.; Baughman, James M.

    2010-01-01

    Fiber reinforced resin matrix composites have found increased usage in recent years. Due to the lack of service history of these relatively new material systems, their long-term aging performance is not well established. In this study, adhesive bonds were prepared by the secondary bonding of Scotch-Weld(TradeMark) AF-555M between pre-cured adherends comprised of T800H/3900-2 uni-directional laminate. The adherends were co-cured with wet peel-ply for surface preparation. Each bond-line of single-lap-shear (SLS) specimen was measured to determine thickness and inspected visually for voids. A three-year environmental aging plan for the SLS specimens at 82 C and 85% relative humidity was initiated. SLS strengths were measured for both controls and aged specimens at room temperature and 82 C. The aging results of strength retention and failure modes to date are reported.

  15. Anorexic effect of peripheral cholecystokinin (CCK) varies with age and body composition (short communication).

    PubMed

    Balaskó, Márta; Soós, Sz; Párniczky, A; Koncsecskó-Gáspár, M; Székely, M; Pétervári, E

    2012-06-01

    Obesity of middle-aged mammals is followed at old age by anorexia and cachexia leading to sarcopenia. Complex age- and body composition-related alterations in the regulation of energy homeostasis may be assumed in the background. We aimed to test the possible contribution of age- and body composition-related changes of satiety responses to catabolic brain-gut-axis peptide cholecystokinin (CCK) to these alterations in energy balance during aging. Male Wistar rats (6-8 animals/group) aged 2 months (juvenile), 3 months (young adult), 6 or 12 months (early or late middle-aged), and 24 months (old) were injected intraperitoneally with 5 μg CCK-8 prior to re-feeding after 48-h food-deprivation. CCK suppressed re-feeding in young adult (26.8%), early middle-aged (35.5%), and old (31.4%) animals, but not in juvenile or late middle-aged rats (one-way ANOVA). CCK-resistance of 12 months old rats was prevented by life-long calorie-restriction: CCK suppressed their re-feeding by 46.8%. Conversely, in highfat diet-induced obese 6 months old rats CCK failed to suppress re-feeding. In conclusion, age-related changes in satiety responsiveness to CCK may contribute to the age-related obesity of middle-aged as well as to the anorexia of old animals. CCK-responsiveness is also influenced by body composition: calorie-restriction prevents the resistance to CCK, pre-existing obesity enhances it.

  16. High-volume-fraction Cu/Al2O3-SiC hybrid interpenetrating phase composite

    NASA Astrophysics Data System (ADS)

    Saidi, Hesam; Roudini, Ghodratollah; Afarani, Mahdi Shafiee

    2015-10-01

    Metal matrix particulate interpenetrating phase composites are a class of composites materials with three-dimensional internal connections of matrix and reinforcements. This kind of microstructure affects the mechanical and physical properties of the composites. In this study, Al2O3-SiC hybrid preforms were produced by polyurethane foams removal (replica method) within mean pore size of 30 pores per inch (ppi), and sintering at 1200 °C. Subsequently, the molten copper was infiltrated into the preforms by squeeze casting method. The microstructure, density, porosity, bending strength and thermal shock resistance of the preforms were investigated. Then, the composites microstructure and compressive strength were studied. The results showed that with SiC concentration increasing, the density, flexural strength and thermal shock resistance of the preforms were improved. Also the composites compressive strengths were changed with variation of SiC concentration.

  17. Highly sensitive piezo-resistive graphite nanoplatelet-carbon nanotube hybrids/polydimethylsilicone composites with improved conductive network construction.

    PubMed

    Zhao, Hang; Bai, Jinbo

    2015-05-13

    The constructions of internal conductive network are dependent on microstructures of conductive fillers, determining various electrical performances of composites. Here, we present the advanced graphite nanoplatelet-carbon nanotube hybrids/polydimethylsilicone (GCHs/PDMS) composites with high piezo-resistive performance. GCH particles were synthesized by the catalyst chemical vapor deposition approach. The synthesized GCHs can be well dispersed in the matrix through the mechanical blending process. Due to the exfoliated GNP and aligned CNTs coupling structure, the flexible composite shows an ultralow percolation threshold (0.64 vol %) and high piezo-resistive sensitivity (gauge factor ∼ 10(3) and pressure sensitivity ∼ 0.6 kPa(-1)). Slight motions of finger can be detected and distinguished accurately using the composite film as a typical wearable sensor. These results indicate that designing the internal conductive network could be a reasonable strategy to improve the piezo-resistive performance of composites.

  18. Highly sensitive piezo-resistive graphite nanoplatelet-carbon nanotube hybrids/polydimethylsilicone composites with improved conductive network construction.

    PubMed

    Zhao, Hang; Bai, Jinbo

    2015-05-13

    The constructions of internal conductive network are dependent on microstructures of conductive fillers, determining various electrical performances of composites. Here, we present the advanced graphite nanoplatelet-carbon nanotube hybrids/polydimethylsilicone (GCHs/PDMS) composites with high piezo-resistive performance. GCH particles were synthesized by the catalyst chemical vapor deposition approach. The synthesized GCHs can be well dispersed in the matrix through the mechanical blending process. Due to the exfoliated GNP and aligned CNTs coupling structure, the flexible composite shows an ultralow percolation threshold (0.64 vol %) and high piezo-resistive sensitivity (gauge factor ∼ 10(3) and pressure sensitivity ∼ 0.6 kPa(-1)). Slight motions of finger can be detected and distinguished accurately using the composite film as a typical wearable sensor. These results indicate that designing the internal conductive network could be a reasonable strategy to improve the piezo-resistive performance of composites. PMID:25898271

  19. Gel spinning of PVA composite fibers with high content of multi-walled carbon nanotubes and graphene oxide hybrids

    NASA Astrophysics Data System (ADS)

    Wei, Yizhe; Lai, Dengpan; Zou, Liming; Ling, Xinlong; Lu, Hongwei; Xu, Yongjing

    2015-07-01

    In this report, poly (vinyl alcohol) (PVA) composite fibers with high content of multi-walled carbon nanotubes and graphene oxide (MWCNTs-GO) hybrids were prepared by gel spinning, and were characterized by TGA, DSC, SEM, XL-2 yarn strength tester and electrical conductivity measurement. The total content of MWCNTs-GO hybrids in the PVA composite fibers, which is up to 25 wt%, was confirmed by TGA analysis. The DSC measurement shows that the melting and crystallization peaks decreased after the addition of nano-fillers. This is due to the reason that the motion of PVA chains is completely confined by strong hydrogen bonding interaction between PVA and nano-fillers. After the addtion of GO, the dispersibility of MWCNTs in composite fibers improved slightly. And the tensile strength and Young's modulus increased by 38% and 67%, respectively. This is caused by the increased hydrogen bonding interaction and synergistic effect through hybridization of MWCNTs and GO. More significantly, the electrical conductivity of PVA/MWCNTs/GO composite fibers enhanced by three orders of magnitude with the addition of GO.

  20. One-step in situ synthesis of graphene–TiO{sub 2} nanorod hybrid composites with enhanced photocatalytic activity

    SciTech Connect

    Sun, Mingxuan Li, Weibin; Sun, Shanfu; He, Jia; Zhang, Qiang; Shi, Yuying

    2015-01-15

    Chemically bonded graphene/TiO{sub 2} nanorod hybrid composites with superior dispersity were synthesized by a one-step in situ hydrothermal method using graphene oxide (GO) and TiO{sub 2} (P25) as the starting materials. The as-prepared samples were characterized by XRD, XPS, TEM, FE-SEM, EDX, Raman, N{sub 2} adsorption, and UV–vis DRS techniques. Enhanced light absorption and a red shift of absorption edge were observed for the composites in the ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS). Their effective photocatalytic activity was evaluated by the photodegradation of methylene blue under visible light irradiation. An enhancement of photocatalytic performance was observed over graphene/TiO{sub 2} nanorod hybrid composite photocatalysts, as 3.7 times larger than that of pristine TiO{sub 2} nanorods. This work demonstrated that the synthesis of TiO{sub 2} nanorods and simultaneous conversion of GO to graphene “without using reducing agents” had shown to be a rapid, direct and clean approach to fabricate chemically bonded graphene/TiO{sub 2} nanorod hybrid composites with enhanced photocatalytic performance.

  1. Marginal and internal adaptation of Class II ormocer and hybrid resin composite restorations before and after load cycling.

    PubMed

    Kournetas, N; Chakmakchi, M; Kakaboura, A; Rahiotis, C; Geis-Gerstorfer, J

    2004-09-01

    To overcome the shortcomings of the conventional composite restorative materials, ormocer materials have been introduced over the past few years. The purpose of this study was to evaluate the marginal and internal adaptation of two ormocer restorative systems (Admira, Voco and Definite, Degussa) compared to a hybrid composite one (TPH Spectrum, Dentsply/ DeTrey), before and after load cycling in Class II restorations. Standardized Class II restorations with cervical margins on enamel were divided into three groups ( n=16). Teeth of each group were filled with one of the restoratives tested and its respective bonding agent. Each group was divided into two equal subgroups. The marginal and internal adaptation of the first subgroup was evaluated after 7-day water storage at room temperature and of the second after cyclic loading in a mastication simulator (1.2x10(6) cycles, 49 N, 1.6 Hz). The occlusal and cervical marginal evaluation was conducted by videomicroscope and ranked as "excellent" and "not excellent". One thin section (150 microm), in mesial-distal direction, of each restoration, was examined under metallographic microscope to determine the quality of internal adaptation. The occlusal and cervical adaptation of both ormocer restorative systems was similar and clearly worse compared with the hybrid composite restorative one before as well as after load cycling. Concerning internal adaptation, no gap-free ormocer restorations were detected, whereas all Spectrum restorations presented perfect adaptation. The bonding agents of the ormocers formed layers with unacceptable features (pores, fractures) whereas that of the hybrid composite achieved perfect bonding layer even after loading. The rheological characteristics of the bonding agents of the ormocer restorative systems are proposed to be responsible for their inferior marginal and internal quality in Class II restorations compared with the hybrid composite one.

  2. Penetration of carbon-fabric-reinforced composites by edge cracks during thermal aging

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.; Kamvouris, John E.

    1994-01-01

    Thermo-oxidative stability (TOS) test results are significantly influenced by the formation and growth or presence of interlaminar and interlaminar cracks in the cut edges of all carbon-fiber-crosslinked high-temperature polymer matrix composites(exp 1-5) (i.e., unidirectional, crossplied, angle-plied, and fabric composites). The thermo-oxidative degradation of these composites is heavily dependent on the surface area that is exposed to the harmful environment and on the surface-to-volume ratio of the structure under study. Since the growth of cracks and voids on the composite surfaces significantly increases the exposed surface areas, it is imperative that the interaction between the aging process and the formation of new surface area as the aging time progresses be understood.

  3. Effects of physical aging on long-term creep of polymers and polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Brinson, L. Catherine; Gates, Thomas S.

    1994-01-01

    For many polymeric materials in use below the glass transition temperature, the long term viscoelastic behavior is greatly affected by physical aging. To use polymer matrix composites as critical structural components in existing and novel technological applications, this long term behavior of the material system must be understood. Towards that end, this study applied the concepts governing the mechanics of physical aging in a consistent manner to the study of laminated composite systems. Even in fiber-dominated lay-ups the effects of physical aging are found to be important in the long-term behavior of the composite. The basic concepts describing physical aging of polymers are discussed. Several aspects of physical aging which have not been previously documented are also explored in this study, namely the effects of aging into equilibrium and a relationship to the time-temperature shift factor. The physical aging theory is then extended to develop the long-term compliance/modulus of a single lamina with varying fiber orientation. The latter is then built into classical lamination theory to predict long-time response of general oriented lamina and laminates. It is illustrated that the long term response can be counterintuitive, stressing the need for consistent modeling efforts to make long term predictions of laminates to be used in structural situations.

  4. Fluorescence intensity of resin composites and dental tissues before and after accelerated aging: a comparative study.

    PubMed

    Takahashi, Marcos Kenzo; Vieira, Sergio; Rached, Rodrigo Nunes; de Almeida, Janaina Bertoncelo; Aguiar, Marcelo; de Souza, Evelise Machado

    2008-01-01

    This study quantitatively evaluated the fluorescence intensity of resin composites with different opacities and translucencies and determined changes in fluorescence after accelerated aging, using human enamel and dentin as controls. Six microhybrid and nanofilled composites, each in three different shades, were tested. Ten sound human incisors were used to obtain enamel and dentin specimens separately. Fluorescence measurements were obtained with a fluorescence spectrophotometer before (baseline) and after accelerated aging at 150 kJ energy for 120 hours. One-way analysis of variance (ANOVA) and Games-Howell multiple comparison tests were performed at a significance level of 0.05. Student's t-test was also used for comparison before and after aging. At baseline, there was no statistically significant difference (p>0.05) between the fluorescence intensity of dentin and any of the shades of Charisma or Opallis, Esthet-X dentin shade or Vit-l-escence enamel, or the translucent shades. After accelerated aging, all shades of the 4 Seasons, enamel and the translucent shades of Esthet-X had fluorescence intensities statistically similar to that of aged dentin (p>0.05). A significant reduction in fluorescence after aging (p<0.05) was observed for all the materials, except for human enamel and translucent Filtek Supreme XT. Accelerated aging reduced fluorescence in most of the composites evaluated.

  5. Effect of Thermally Softened Bronze Matrix on the Fracturing Behavior of Diamond Particles in Hybrid Sprayed Bronze/Diamond Composite

    NASA Astrophysics Data System (ADS)

    Na, Hyuntaek; Bae, Gyuyeol; Kang, Kicheol; Kim, Hyungjun; Kim, Jay-Jung; Lee, Changhee

    2010-09-01

    In our previous study (Na et al., Compos Sci Technol 69:463-468, 2009), optimized thickness of protective nickel film was proposed for smaller diamond feedstock to obtain reduced impact stress and uniform flight behavior of particles during kinetic (or cold) spraying. However, in this study, nickel-coated diamond particles were severely fractured with increasing particle size due to high kinetic energy. Hence, an innovative hybrid spraying technique (a combination of kinetic and thermal spraying) was introduced to embed relatively large diamond particles into the bronze matrix. Size distributions of the diamond particles in the composite coatings were analyzed by scanning electron microscopy, an electron probe micro analyzer, and image analysis methods. In addition, impact behaviors of diamond particles in kinetic and hybrid gas flows were simulated through finite element analysis (ABAQUS/Explicit 6.7-2). Diamond fracturing was significantly minimized by the reduced impact energy afforded by the thermally softened bronze matrix through hybrid spraying.

  6. Design and analysis of variable-twist tiltrotor blades using shape memory alloy hybrid composites

    NASA Astrophysics Data System (ADS)

    Park, Jae-Sang; Kim, Seong-Hwan; Jung, Sung Nam; Lee, Myeong-Kyu

    2011-01-01

    The tiltrotor blade, or proprotor, acts as a rotor in the helicopter mode and as a propeller in the airplane mode. For a better performance, the proprotor should have different built-in twist distributions along the blade span, suitable for each operational mode. This paper proposes a new variable-twist proprotor concept that can adjust the built-in twist distribution for given flight modes. For a variable-twist control, the present proprotor adopts shape memory alloy hybrid composites (SMAHC) containing shape memory alloy (SMA) wires embedded in the composite matrix. The proprotor of the Korea Aerospace Research Institute (KARI) Smart Unmanned Aerial Vehicle (SUAV), which is based on the tiltrotor concept, is used as a baseline proprotor model. The cross-sectional properties of the variable-twist proprotor are designed to maintain the cross-sectional properties of the original proprotor as closely as possible. However, the torsion stiffness is significantly reduced to accommodate the variable-twist control. A nonlinear flexible multibody dynamic analysis is employed to investigate the dynamic characteristics of the proprotor such as natural frequency and damping in the whirl flutter mode, the blade structural loads in a transition flight and the rotor performance in hover. The numerical results show that the present proprotor is designed to have a strong similarity to the baseline proprotor in dynamic and load characteristics. It is demonstrated that the present proprotor concept could be used to improve the hover performance adaptively when the variable-twist control using the SMAHC is applied appropriately.

  7. Shear bond strength of orthodontic brackets to aged resin composite surfaces: effect of surface conditioning.

    PubMed

    Bayram, Mehmet; Yesilyurt, Cemal; Kusgöz, Adem; Ulker, Mustafa; Nur, Metin

    2011-04-01

    The aim of this study was to investigate the effects of surface conditioning protocols on the shear bond strength (SBS) of metal brackets to aged composite resin surfaces in vitro. Ninety composite resin discs, 6 mm in diameter and 2 mm in height, were prepared and treated with an ageing procedure. After ageing, the specimens were randomly assigned to one of the following groups: (1) control with no surface treatment, (2) 38 per cent phosphoric acid gel, (3) 9.6 per cent hydrofluoric acid gel, (4) airborne aluminium trioxide particle abrasion, (5) sodium bicarbonate particle abrasion, and (6) diamond bur. The metal brackets were bonded to composite surfaces by means of an orthodontic adhesive (Transbond XT). All specimens were stored in water for 1 week at 37°C and then thermocycled (1000 cycles, 5-55°C) prior to SBS testing. SBS values and residual adhesive on the composite surface were evaluated. Analysis of variance showed a significant difference (P = 0.000) between the groups. Group 6 had the highest mean SBS (10.61 MPa), followed by group 4 (10.29 MPa). The results of this study suggest that a clinically acceptable bond strength can be achieved by surface conditioning of aged resin composite via the application of hydrofluoric acid, aluminium trioxide particle abrasion, sodium bicarbonate particle abrasion, or a diamond bur. PMID:20660131

  8. Age-specific profiles of tissue-level composition and mechanical properties in murine cortical bone.

    PubMed

    Raghavan, Mekhala; Sahar, Nadder D; Kohn, David H; Morris, Michael D

    2012-04-01

    There is growing evidence that bone composition and tissue-level mechanical properties are significant determinants of skeletal integrity. In the current study, Raman spectroscopy and nanoindentation testing were co-localized to analyze tissue-level compositional and mechanical properties in skeletally mature young (4 or 5 months) and old (19 months) murine femora at similar spatial scales. Standard multivariate linear regression analysis revealed age-dependent patterns in the relationships between mechanical and compositional properties at the tissue scale. However, changes in bone material properties with age are often complex and nonlinear, and can be missed with linear regression and correlation-based methods. A retrospective data mining approach was implemented using non-linear multidimensional visualization and classification to identify spectroscopic and nanoindentation metrics that best discriminated bone specimens of different age-classes. The ability to classify the specimens into the correct age group increased by using combinations of Raman and nanoindentation variables (86-96% accuracy) as compared to using individual measures (59-79% accuracy). Metrics that best classified 4 or 5 month and 19 month specimens (2-age classes) were mineral to matrix ratio, crystallinity, modulus and plasticity index. Metrics that best distinguished between 4, 5 and 19 month specimens (3-age classes) were mineral to matrix ratio, crystallinity, modulus, hardness, cross-linking, carbonate to phosphate ratio, creep displacement and creep viscosity. These findings attest to the complexity of mechanisms underlying bone tissue properties and draw attention to the importance of considering non-linear interactions between tissue-level composition and mechanics that may work together to influence material properties with age. The results demonstrate that a few non-linearly combined compositional and mechanical metrics provide better discriminatory information than a single metric

  9. Influence of artificial ageing on surface properties and Streptococcus mutans adhesion to dental composite materials.

    PubMed

    Hahnel, Sebastian; Henrich, Anne; Rosentritt, Martin; Handel, Gerhard; Bürgers, Ralf

    2010-02-01

    The aim of this in vitro study was to investigate the influence of artificial ageing on the surface properties and early Streptococcus mutans adhesion to current dental composites for the direct restoration of class II defects. Three hundred and thirty specimens each were prepared from five dental composites, and were randomly allotted to various artificial ageing protocols (storage in distilled water/ethanol/artificial saliva for 7/90/365 days; thermal cycling, 6,000 cycles 5/55 degrees C). Prior and after each treatment, surface roughness (R(a)) and hydrophobicity were determined, and S. mutans adhesion (ATCC 25175; 2.5 h, 37 degrees C) was simulated with and without prior exposition to human whole saliva (2 h, 37 degrees C). Adherence of S. mutans was determined fluorometrically. Means and standard deviations were calculated, and analyzed using three-way ANOVA and post-hoc analysis (alpha = 0.05). For both R(a) and S. mutans adherence to uncoated and saliva-coated specimens, significant influences of the composite material, the ageing medium and the ageing duration have been observed; for surface hydrophobicity, significant influences of the composite material and the ageing duration were found. For uncoated specimens, significant increases in S. mutans adhesion were observed with prolonged artificial ageing, whereas significant decreases in S. mutans adhesion were found for the saliva-coated specimens. The data indicate influences of the artificial ageing method on surface parameters such as R(a) and hydrophobicity as well as microbial adhesion. The results underline the relevance of saliva coating on the outcome of studies simulating microbial adhesion, and highlight differences in the susceptibility of dental composites for the adhesion of oral bacteria.

  10. Pt-TiO2/MWCNTs Hybrid Composites for Monitoring Low Hydrogen Concentrations in Air

    PubMed Central

    Trocino, Stefano; Donato, Andrea; Latino, Mariangela; Donato, Nicola; Leonardi, Salvatore Gianluca; Neri, Giovanni

    2012-01-01

    Hydrogen is a valuable fuel for the next energy scenario. Unfortunately, hydrogen is highly flammable at concentrations higher than 4% in air. This aspect makes the monitoring of H2 leaks an essential issue for safety reasons, especially in the transportation field. In this paper, nanocomposites based on Pt-doped TiO2/multiwalled carbon nanotubes (MWCNTs) have been introduced as sensitive materials for H2 at low temperatures. Pt-TiO2/MWNTs nanocomposites with different composition have been prepared by a simple wet chemical procedure and their morphological, microstructural and electrical properties were investigated. Resistive thick-film devices have been fabricated printing the hybrid nanocomposites on alumina substrates provided with Pt interdigitated electrodes. Electrical tests in air have shown that embedding MWCNTs in the TiO2 matrix modify markedly the electrical conductivity, providing a means to decrease the resistance of the sensing layer. Pt acts as a catalytic additive. Pt-TiO2/MWNTs-based sensors were found to be sensitive to hydrogen at concentrations between 0.5 and 3% in air, satisfying the requisites for practical applications in hydrogen leak detection devices.

  11. Determination of phenolic compounds in air by using cyclodextrin-silica hybrid microporous composite samplers.

    PubMed

    Mauri-Aucejo, Adela R; Ponce-Català, Patricia; Belenguer-Sapiña, Carolina; Amorós, Pedro

    2015-03-01

    An analytical method for the determination of phenolic compounds in air samples based on the use of cyclodextrin-silica hybrid microporous composite samplers is proposed. The method allows the determination of phenol, guaiacol, cresol isomers, eugenol, 4-ethylphenol and 4-ethylguaiacol in workplaces according to the Norm UNE-EN 1076:2009 for active sampling. Therefore, the proposed method offers an alternative for the assessment of the occupational exposure to phenol and cresol isomers. The detection limits of the proposed method are lower than those for the NIOSH Method 2546. Storage time of samples almost reaches 44 days. Recovery values for phenol, guaiacol, o-cresol, m-cresol, p-cresol, 4-ethylguaiacol, eugenol and 4-ethylphenol are 109%, 99%, 102%, 94%, 94%, 91%, 95% and 102%, respectively with a coefficient of variation below 6%. The method has been applied to the assessment of exposure in different areas of a farm and regarding the quantification of these compounds in the vapors generated by burning incense sticks and an essential oil marketed as air fresheners. The acquired results are comparable with those provided from a reference method for a 95% of confidence level. The possible use of these samplers for the sampling of other toxic compounds such as phthalates is evaluated by qualitative analysis of extracts from incense sticks and essential oil samples.

  12. Assumed--stress hybrid elements with drilling degrees of freedom for nonlinear analysis of composite structures

    NASA Technical Reports Server (NTRS)

    Knight, Norman F., Jr. (Principal Investigator)

    1996-01-01

    The goal of this research project is to develop assumed-stress hybrid elements with rotational degrees of freedom for analyzing composite structures. During the first year of the three-year activity, the effort was directed to further assess the AQ4 shell element and its extensions to buckling and free vibration problems. In addition, the development of a compatible 2-node beam element was to be accomplished. The extensions and new developments were implemented in the Computational Structural Mechanics Testbed COMET. An assessment was performed to verify the implementation and to assess the performance of these elements in terms of accuracy. During the second and third years, extensions to geometrically nonlinear problems were developed and tested. This effort involved working with the nonlinear solution strategy as well as the nonlinear formulation for the elements. This research has resulted in the development and implementation of two additional element processors (ES22 for the beam element and ES24 for the shell elements) in COMET. The software was developed using a SUN workstation and has been ported to the NASA Langley Convex named blackbird. Both element processors are now part of the baseline version of COMET.

  13. Carboxymethyl cellulose-hydroxyapatite hybrid hydrogel as a composite material for bone tissue engineering applications.

    PubMed

    Pasqui, Daniela; Torricelli, Paola; De Cagna, Milena; Fini, Milena; Barbucci, Rolando

    2014-05-01

    Natural bone is a complex inorganic-organic nanocomposite material, in which hydroxyapatite (HA) nanocrystals and collagen fibrils are well organized into hierarchical architecture over several length scales. In this work, we reported a new hybrid material (CMC-HA) containing HA drown in a carboxymethylcellulose (CMC)-based hydrogel. The strategy for inserting HA nanocrystals within the hydrogel matrix consists of making the freeze-dried hydrogel to swell in a solution containing HA microcrystals. The composite CMC-HA hydrogel has been characterized from a physicochemical and morphological point of view by means of FTIR spectroscopy, rheological measurements, and field emission scanning electron microscopy (FESEM). No release of HA was measured in water or NaCl solution. The distribution of HA crystal on the surface and inside the hydrogel was determined by time of flight secondary ion mass spectrometry (ToF-SIMS) and FESEM. The biological performance of CMC-HA hydrogel were tested by using osteoblast MG63 line and compared with a CMC-based hydrogel without HA. The evaluation of osteoblast markers and gene expression showed that the addition of HA to CMC hydrogel enhanced cell proliferation and metabolic activity and promoted the production of mineralized extracellular matrix.

  14. Stress analysis and damage evaluation of flawed composite laminates by hybrid-numerical methods

    NASA Technical Reports Server (NTRS)

    Yang, Yii-Ching

    1992-01-01

    Structural components in flight vehicles is often inherited flaws, such as microcracks, voids, holes, and delamination. These defects will degrade structures the same as that due to damages in service, such as impact, corrosion, and erosion. It is very important to know how a structural component can be useful and survive after these flaws and damages. To understand the behavior and limitation of these structural components researchers usually do experimental tests or theoretical analyses on structures with simulated flaws. However, neither approach has been completely successful. As Durelli states that 'Seldom does one method give a complete solution, with the most efficiency'. Examples of this principle is seen in photomechanics which additional strain-gage testing can only average stresses at locations of high concentration. On the other hand, theoretical analyses including numerical analyses are implemented with simplified assumptions which may not reflect actual boundary conditions. Hybrid-Numerical methods which combine photomechanics and numerical analysis have been used to correct this inefficiency since 1950's. But its application is limited until 1970's when modern computer codes became available. In recent years, researchers have enhanced the data obtained from photoelasticity, laser speckle, holography and moire' interferometry for input of finite element analysis on metals. Nevertheless, there is only few of literature being done on composite laminates. Therefore, this research is dedicated to this highly anisotropic material.

  15. Preparation and ageing-resistant properties of polyester composites modified with functional nanoscale additives.

    PubMed

    Guo, Gang; Shi, Qiwu; Luo, Yanbing; Fan, Rangrang; Zhou, Liangxue; Qian, Zhiyong; Yu, Jie

    2014-01-01

    This study investigated ageing-resistant properties of carboxyl-terminated polyester (polyethylene glycol terephthalate) composites modified with nanoscale titanium dioxide particles (nano-TiO2). The nano-TiO2 was pretreated by a dry coating method, with aluminate coupling agent as a functional grafting additive. The agglomeration resistance was evaluated, which exhibited significant improvement for the modified nanoparticles. Then, the effects of the modified nano-TiO2 on the crosslinking and ageing-resistant properties of the composites were studied. With a real-time Fourier transform infrared (FT-IR) measurement, the nano-TiO2 displayed promoting effect on the crosslinking of polyester resin with triglycidyl isocyanurate (TGIC) as crosslinking agent. Moreover, the gloss retention, colour aberration and the surface morphologies of the composites during accelerated UV ageing (1500 hours) were investigated. The results demonstrated much less degree of ageing degradation for the nanocomposites, indicating an important role of the nano-TiO2 in improving the ageing-resistant properties of synthetic polymer composites. PMID:24872802

  16. Preparation and ageing-resistant properties of polyester composites modified with functional nanoscale additives.

    PubMed

    Guo, Gang; Shi, Qiwu; Luo, Yanbing; Fan, Rangrang; Zhou, Liangxue; Qian, Zhiyong; Yu, Jie

    2014-01-01

    This study investigated ageing-resistant properties of carboxyl-terminated polyester (polyethylene glycol terephthalate) composites modified with nanoscale titanium dioxide particles (nano-TiO2). The nano-TiO2 was pretreated by a dry coating method, with aluminate coupling agent as a functional grafting additive. The agglomeration resistance was evaluated, which exhibited significant improvement for the modified nanoparticles. Then, the effects of the modified nano-TiO2 on the crosslinking and ageing-resistant properties of the composites were studied. With a real-time Fourier transform infrared (FT-IR) measurement, the nano-TiO2 displayed promoting effect on the crosslinking of polyester resin with triglycidyl isocyanurate (TGIC) as crosslinking agent. Moreover, the gloss retention, colour aberration and the surface morphologies of the composites during accelerated UV ageing (1500 hours) were investigated. The results demonstrated much less degree of ageing degradation for the nanocomposites, indicating an important role of the nano-TiO2 in improving the ageing-resistant properties of synthetic polymer composites.

  17. Preparation and ageing-resistant properties of polyester composites modified with functional nanoscale additives

    NASA Astrophysics Data System (ADS)

    Guo, Gang; Shi, Qiwu; Luo, Yanbing; Fan, Rangrang; Zhou, Liangxue; Qian, Zhiyong; Yu, Jie

    2014-05-01

    This study investigated ageing-resistant properties of carboxyl-terminated polyester (polyethylene glycol terephthalate) composites modified with nanoscale titanium dioxide particles (nano-TiO2). The nano-TiO2 was pretreated by a dry coating method, with aluminate coupling agent as a functional grafting additive. The agglomeration resistance was evaluated, which exhibited significant improvement for the modified nanoparticles. Then, the effects of the modified nano-TiO2 on the crosslinking and ageing-resistant properties of the composites were studied. With a real-time Fourier transform infrared (FT-IR) measurement, the nano-TiO2 displayed promoting effect on the crosslinking of polyester resin with triglycidyl isocyanurate (TGIC) as crosslinking agent. Moreover, the gloss retention, colour aberration and the surface morphologies of the composites during accelerated UV ageing (1500 hours) were investigated. The results demonstrated much less degree of ageing degradation for the nanocomposites, indicating an important role of the nano-TiO2 in improving the ageing-resistant properties of synthetic polymer composites.

  18. Preparation and ageing-resistant properties of polyester composites modified with functional nanoscale additives

    PubMed Central

    2014-01-01

    This study investigated ageing-resistant properties of carboxyl-terminated polyester (polyethylene glycol terephthalate) composites modified with nanoscale titanium dioxide particles (nano-TiO2). The nano-TiO2 was pretreated by a dry coating method, with aluminate coupling agent as a functional grafting additive. The agglomeration resistance was evaluated, which exhibited significant improvement for the modified nanoparticles. Then, the effects of the modified nano-TiO2 on the crosslinking and ageing-resistant properties of the composites were studied. With a real-time Fourier transform infrared (FT-IR) measurement, the nano-TiO2 displayed promoting effect on the crosslinking of polyester resin with triglycidyl isocyanurate (TGIC) as crosslinking agent. Moreover, the gloss retention, colour aberration and the surface morphologies of the composites during accelerated UV ageing (1500 hours) were investigated. The results demonstrated much less degree of ageing degradation for the nanocomposites, indicating an important role of the nano-TiO2 in improving the ageing-resistant properties of synthetic polymer composites. PMID:24872802

  19. Constitutive Modeling and Testing of Polymer Matrix Composites Incorporating Physical Aging at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Veazie, David R.

    1998-01-01

    Advanced polymer matrix composites (PMC's) are desirable for structural materials in diverse applications such as aircraft, civil infrastructure and biomedical implants because of their improved strength-to-weight and stiffness-to-weight ratios. For example, the next generation military and commercial aircraft requires applications for high strength, low weight structural components subjected to elevated temperatures. A possible disadvantage of polymer-based composites is that the physical and mechanical properties of the matrix often change significantly over time due to the exposure of elevated temperatures and environmental factors. For design, long term exposure (i.e. aging) of PMC's must be accounted for through constitutive models in order to accurately assess the effects of aging on performance, crack initiation and remaining life. One particular aspect of this aging process, physical aging, is considered in this research.

  20. Minor and trace element composition and age of Yukon probable-microtektites

    NASA Technical Reports Server (NTRS)

    Boundy-Sanders, S. Q.; Hervig, R. L.

    1993-01-01

    Major, minor, and trace element composition of the candidate micro tektites from Yukon Territory suggest a possible impact site of hydrothermally altered limestone and sand or chert, or possibly a carbonatite. Their REE/chondrite curve is similar in character to, but higher than, shale composites of North America, Australia, and Europe. Relative to these same composites, the Yukon droplets are enriched in Y, F, S, Sr, P, Mn, Mg, and Ca. They are depleted in Rb, Li, Th, Nb, Ti, K, Na, Fe, Si, and Al. Biostratigraphic constraints on the droplets indicate they are Middle to Late Devonian, more likely Middle Devonian, in age.

  1. Effects of Age, Walking Speed, and Body Composition on Pedometer Accuracy in Children

    ERIC Educational Resources Information Center

    Duncan, J. Scott; Schofield, Grant; Duncan, Elizabeth K.; Hinckson, Erica A.

    2007-01-01

    The objective of this study was to investigate the effects of age group, walking speed, and body composition on the accuracy of pedometer-determined step counts in children. Eighty-five participants (43 boys, 42 girls), ages 5-7 and 9-11 years, walked on a treadmill for two-minute bouts at speeds of 42, 66, and 90 m[middle dot]min[superscript -1]…

  2. A novel ZnO@Ag@Polypyrrole hybrid composite evaluated as anode material for zinc-based secondary cell

    NASA Astrophysics Data System (ADS)

    Huang, Jianhang; Yang, Zhanhong; Feng, Zhaobin; Xie, Xiaoe; Wen, Xing

    2016-04-01

    A novel ZnO@Ag@Polypyrrole nano-hybrid composite has been synthesized with a one-step approach, in which silver-ammonia complex ion serves as oxidant to polymerize the pyrrole monomer. X-ray diffraction (XRD) and infrared spectroscopy (IR) show the existence of metallic silver and polypyrrole. The structure of nano-hybrid composites are characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM), which demonstrates that the surface of ZnO is decorated with nano silver grain coated with polypyrrole. When evaluated as anode material, the silver grain and polypyrrole layer not only suppress the dissolution of discharge product, but also helps to uniform electrodeposition due to substrate effect and its good conductivity, thus shows better cycling performance than bare ZnO electrode does.

  3. A novel ZnO@Ag@Polypyrrole hybrid composite evaluated as anode material for zinc-based secondary cell

    PubMed Central

    Huang, Jianhang; Yang, Zhanhong; Feng, Zhaobin; Xie, Xiaoe; Wen, Xing

    2016-01-01

    A novel ZnO@Ag@Polypyrrole nano-hybrid composite has been synthesized with a one-step approach, in which silver-ammonia complex ion serves as oxidant to polymerize the pyrrole monomer. X-ray diffraction (XRD) and infrared spectroscopy (IR) show the existence of metallic silver and polypyrrole. The structure of nano-hybrid composites are characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM), which demonstrates that the surface of ZnO is decorated with nano silver grain coated with polypyrrole. When evaluated as anode material, the silver grain and polypyrrole layer not only suppress the dissolution of discharge product, but also helps to uniform electrodeposition due to substrate effect and its good conductivity, thus shows better cycling performance than bare ZnO electrode does. PMID:27074985

  4. A novel ZnO@Ag@Polypyrrole hybrid composite evaluated as anode material for zinc-based secondary cell.

    PubMed

    Huang, Jianhang; Yang, Zhanhong; Feng, Zhaobin; Xie, Xiaoe; Wen, Xing

    2016-01-01

    A novel ZnO@Ag@Polypyrrole nano-hybrid composite has been synthesized with a one-step approach, in which silver-ammonia complex ion serves as oxidant to polymerize the pyrrole monomer. X-ray diffraction (XRD) and infrared spectroscopy (IR) show the existence of metallic silver and polypyrrole. The structure of nano-hybrid composites are characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM), which demonstrates that the surface of ZnO is decorated with nano silver grain coated with polypyrrole. When evaluated as anode material, the silver grain and polypyrrole layer not only suppress the dissolution of discharge product, but also helps to uniform electrodeposition due to substrate effect and its good conductivity, thus shows better cycling performance than bare ZnO electrode does.

  5. Analysis of a hybrid balanced laminate as a structural material for thick composite beams with axial stiffeners

    NASA Astrophysics Data System (ADS)

    Modak, Partha; Hossain, M. Jamil; Ahmed, S. Reaz

    2016-07-01

    An accurate stress analysis has been carried out to investigate the suitability of a hybrid balanced laminate as a structural material for thick composite beams with axial stiffeners. Three different balanced laminates composed of dissimilar ply material as well as fiber orientations are considered for a thick beam on simple supports with stiffened lateral ends. A displacement potential based elasticity approach is used to obtain the numerical solution of the corresponding elastic fields. The overall laminate stresses as well as individual ply stresses are analysed mainly in the perspective of laminate hybridization. Both the fiber material and ply angle of individual laminas are found to play dominant roles in defining the design stresses of the present composite beam.

  6. Composites of hybrids BaTiO3/carbon nanotubes/polyvinylidene fluoride with high dielectric properties

    NASA Astrophysics Data System (ADS)

    Fan, Benhui; Bai, Jinbo

    2015-11-01

    High dielectric composites were prepared based on polyvinylidene fluoride (PVDF) and hybrids BaTiO3-carbon nanotubes (H-BT-CNTs) with a special structure. The hybrids that BT was a core and CNTs grew outside were fabricated by chemical vapor deposition. Due to the special structure, composite’s dielectric permittivity reached 1777 at 100 Hz and 80 at 1 MHz, while loss tangent maintained as 6 at 100 Hz and 0.56 at 1 MHz, respectively. Moreover, dielectric permittivity and ac conductivity of composite were further enhanced after annealing process at moderate temperature. These improved properties were originated from the reformation of conductive network and BT-CNTs structure inside PVDF matrix.

  7. Body composition during fetal development and infancy through the age of 5 years.

    PubMed

    Toro-Ramos, T; Paley, C; Pi-Sunyer, F X; Gallagher, D

    2015-12-01

    Fetal body composition is an important determinant of body composition at birth, and it is likely to be an important determinant at later stages in life. The purpose of this work is to provide a comprehensive overview by presenting data from previously published studies that report on body composition during fetal development in newborns and the infant/child through 5 years of age. Understanding the changes in body composition that occur both in utero and during infancy and childhood, and how they may be related, may help inform evidence-based practice during pregnancy and childhood. We describe body composition measurement techniques from the in utero period to 5 years of age, and identify gaps in knowledge to direct future research efforts. Available literature on chemical and cadaver analyses of fetal studies during gestation is presented to show the timing and accretion rates of adipose and lean tissues. Quantitative and qualitative aspects of fetal lean and fat mass accretion could be especially useful in the clinical setting for diagnostic purposes. The practicality of different pediatric body composition measurement methods in the clinical setting is discussed by presenting the assumptions and limitations associated with each method that may assist the clinician in characterizing the health and nutritional status of the fetus, infant and child. It is our hope that this review will help guide future research efforts directed at increasing the understanding of how body composition in early development may be associated with chronic diseases in later life. PMID:26242725

  8. A general templated method to homogeneous and composition-tunable hybrid TiO2 nanocomposite fibers.

    PubMed

    Xu, Ximing; Li, Xiaona; Lin, Pingyong; Chen, Ting; Yuan, Rusheng; Ding, Zhengxin; Wu, Ling; Wang, Xuxu; Li, Zhaohui

    2011-03-01

    Sequential impregnations of metal ions and titanium tetraisopropoxide (TTIP) into activated carbon fibers (ACF) followed by a solvothermal treatment has been found to be a general method in the preparations of homogeneous and composition-tunable hybrid TiO(2) hierarchical nanocomposite fibers like WO(3)/TiO(2), Fe(2)O(3)/TiO(2) and SnO(2)/TiO(2). PMID:21225065

  9. Negative permittivity and permeability spectra of Cu/yttrium iron garnet hybrid granular composite materials in the microwave frequency range

    SciTech Connect

    Tsutaoka, Takanori Fukuyama, Koki; Kinoshita, Hideaki; Kasagi, Teruhiro; Yamamoto, Shinichiro; Hatakeyama, Kenichi

    2013-12-23

    The relative complex permittivity and permeability spectra of the coagulated copper and yttrium iron garnet (Cu/YIG) hybrid granular composite materials have been studied in the microwave range. The insulator to metal transition was observed at the percolation threshold of Cu particle content (φ{sub Cu} = 16.0 vol. %) in the electrical conductivity. In the percolation threshold, the low frequency plasmonic state caused by the metallic Cu particle networks was observed. The percolated Cu/YIG granular composites show simultaneous negative permittivity and permeability spectra under external magnetic fields.

  10. A comparison of measured and calculated thermal stresses in a hybrid metal matrix composite spar cap element

    NASA Technical Reports Server (NTRS)

    Jenkins, J. M.; Taylor, A. H.; Sakata, I. F.

    1985-01-01

    A hybrid spar of titanium with an integrally brazed composite, consisting of an aluminum matrix reinforced with boron-carbide-coated fibers, was heated in an oven and the resulting thermal stresses were measured. Uniform heating of the spar in an oven resulted in thermal stresses arising from the effects of dissimilar materials and anisotropy of the metal matrix composite. Thermal stresses were calculated from a finite element structural model using anisotropic material properties deduced from constituent properties and rules of mixtures. Comparisons of calculated thermal stresses with measured thermal stresses on the spar are presented. It was shown that failure to account for anisotropy in the metal matrix composite elements would result in large errors in correlating measured and calculated thermal stresses. It was concluded that very strong material characterization efforts are required to predict accurate thermal stresses in anisotropic composite structures.

  11. In Situ Response of Nanostructured Hybrid Fluoridated Restorative Composites on Enamel Demineralization, Surface Roughness and Ion Release.

    PubMed

    Melo, Mary A S; Codes, Bruna M; Passos, Vanara F; Lima, Juliana P M; Rodrigues, Lidiany K A

    2014-12-01

    Recurrent caries at the tooth-restoration margins is the main reason for composite failure. Fluoride-releasing nanohybrid composite resin may reduce the recurrent caries rates. A fluoride-releasing resin (FCR) and non-fluoride-releasing resin (CR) were tested using an in situ model. Demineralization (ΔS), ion release and surface roughness of composite specimens were determined. The F concentration in the group FCR was higher than the CR group. ΔS (Mean ± SD) was 2579 ± 1582 and 1705 ± 1292, respectively, for FCR and CR. Surfaces roughness was altered by biofilm accumulation. The hybrid fluorated restorative composites containing nanoparticles have a slight anticaries action without alteration of surface smoothness of the material. PMID:26466443

  12. NiZn ferrite/Fe hybrid epoxy-based composites: extending magnetic properties to high frequency

    NASA Astrophysics Data System (ADS)

    Wang, Yunqi; Grant, Patrick S.

    2014-08-01

    Hybrid ferromagnetic composites composed of Ni0.4Zn0.6Fe2O4 ferrite powder and Fe particles in an epoxy matrix with various composition ratios were prepared by a simple mould casting route. Planetary ball milling was then introduced to pre-grind Fe and NiZn ferrite filler mixtures before casting, which resulted in fragmentation of the NiZn ferrites and modification of the Fe morphology from spherical particles to sub-micron flakes. Composites containing the ball-milled fillers exhibited a remarkable improvement in electromagnetic properties over the as-supplied materials, especially in the suppression of dielectric and magnetic loss. By combining the characteristics of high resonant frequency of the Fe and low energy losses of the ferrite, an optimum mixture of ball-milled 15 vol% NiZn ferrite and 38 vol% Fe in a hybrid epoxy-based composite gave an approximately one order of magnitude higher extended operating bandwidth over a ferrite-only containing composite, suppressing dielectric and magnetic loss tangents to approximately 10-2 up to 150 MHz without significant deterioration of permeability. This approach of manipulating multi-phase ferromagnetic material fractions and their structure provide for flexibility in the development of bespoke electromagnetic materials for applications in electrically small antenna and metamaterials.

  13. Light-weight sandwich panel honeycomb core with hybrid carbon-glass fiber composite skin for electric vehicle application

    NASA Astrophysics Data System (ADS)

    Cahyono, Sukmaji Indro; Widodo, Angit; Anwar, Miftahul; Diharjo, Kuncoro; Triyono, Teguh; Hapid, A.; Kaleg, S.

    2016-03-01

    The carbon fiber reinforced plastic (CFRP) composite is relative high cost material in current manufacturing process of electric vehicle body structure. Sandwich panels consisting polypropylene (PP) honeycomb core with hybrid carbon-glass fiber composite skin were investigated. The aim of present paper was evaluate the flexural properties and bending rigidity of various volume fraction carbon-glass fiber composite skins with the honeycomb core. The flexural properties and cost of panels were compared to the reported values of solid hybrid Carbon/Glass FRP used for the frame body structure of electric vehicle. The finite element model of represented sandwich panel was established to characterize the flexural properties of material using homogenization technique. Finally, simplified model was employed to crashworthiness analysis for engine hood of the body electric vehicle structure. The good cost-electiveness of honeycomb core with hybrid carbon-glass fiber skin has the potential to be used as a light-weight alternative material in body electric vehicle fabricated.

  14. Reinforcement of natural rubber hybrid composites based on marble sludge/Silica and marble sludge/rice husk derived silica

    PubMed Central

    Ahmed, Khalil; Nizami, Shaikh Sirajuddin; Riza, Nudrat Zahid

    2013-01-01

    A research has been carried out to develop natural rubber (NR) hybrid composites reinforced with marble sludge (MS)/Silica and MS/rice husk derived silica (RHS). The primary aim of this development is to scrutinize the cure characteristics, mechanical and swelling properties of such hybrid composite. The use of both industrial and agricultural waste such as marble sludge and rice husk derived silica has the primary advantage of being eco-friendly, low cost and easily available as compared to other expensive fillers. The results from this study showed that the performance of NR hybrid composites with MS/Silica and MS/RHS as fillers is extremely better in mechanical and swelling properties as compared with the case where MS used as single filler. The study suggests that the use of recently developed silica and marble sludge as industrial and agricultural waste is accomplished to provide a probable cost effective, industrially prospective, and attractive replacement to the in general purpose used fillers like china clay, calcium carbonate, and talc. PMID:25685484

  15. Enhancement of Thermoelectric Properties of PEDOT:PSS and Tellurium-PEDOT:PSS Hybrid Composites by Simple Chemical Treatment

    NASA Astrophysics Data System (ADS)

    Jin Bae, Eun; Hun Kang, Young; Jang, Kwang-Suk; Yun Cho, Song

    2016-01-01

    The thermoelectric properties of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and tellurium-PEDOT:PSS (Te-PEDOT:PSS) hybrid composites were enhanced via simple chemical treatment. The performance of thermoelectric materials is determined by their electrical conductivity, thermal conductivity, and Seebeck coefficient. Significant enhancement of the electrical conductivity of PEDOT:PSS and Te-PEDOT:PSS hybrid composites from 787.99 and 11.01 to 4839.92 and 334.68 S cm-1, respectively was achieved by simple chemical treatment with H2SO4. The power factor of the developed materials could be effectively tuned over a very wide range depending on the concentration of the H2SO4 solution used in the chemical treatment. The power factors of the developed thermoelectric materials were optimized to 51.85 and 284 μW m-1 K-2, respectively, which represent an increase of four orders of magnitude relative to the corresponding parameters of the untreated thermoelectric materials. Using the Te-PEDOT:PSS hybrid composites, a flexible thermoelectric generator that could be embedded in textiles was fabricated by a printing process. This thermoelectric array generates a thermoelectric voltage of 2 mV using human body heat.

  16. Enhancement of Thermoelectric Properties of PEDOT:PSS and Tellurium-PEDOT:PSS Hybrid Composites by Simple Chemical Treatment

    PubMed Central

    Jin Bae, Eun; Hun Kang, Young; Jang, Kwang-Suk; Yun Cho, Song

    2016-01-01

    The thermoelectric properties of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and tellurium-PEDOT:PSS (Te-PEDOT:PSS) hybrid composites were enhanced via simple chemical treatment. The performance of thermoelectric materials is determined by their electrical conductivity, thermal conductivity, and Seebeck coefficient. Significant enhancement of the electrical conductivity of PEDOT:PSS and Te-PEDOT:PSS hybrid composites from 787.99 and 11.01 to 4839.92 and 334.68 S cm−1, respectively was achieved by simple chemical treatment with H2SO4. The power factor of the developed materials could be effectively tuned over a very wide range depending on the concentration of the H2SO4 solution used in the chemical treatment. The power factors of the developed thermoelectric materials were optimized to 51.85 and 284 μW m−1 K−2, respectively, which represent an increase of four orders of magnitude relative to the corresponding parameters of the untreated thermoelectric materials. Using the Te-PEDOT:PSS hybrid composites, a flexible thermoelectric generator that could be embedded in textiles was fabricated by a printing process. This thermoelectric array generates a thermoelectric voltage of 2 mV using human body heat. PMID:26728992

  17. Reduction of the impact of atmospheric ageing effects on spin coated γ-CuCl nanocrystalline hybrid films

    NASA Astrophysics Data System (ADS)

    Alam, M. M.; Daniels, S.; McNally, P. J.

    2016-01-01

    γ-CuCl (Eg = 3.395 eV at 4 K) is an ionic I-VII compound semiconductor material with the zincblende structure at room temperature. This is one of the most studied inorganic materials for excitonic related linear/non-linear optical processes due to its large excitonic binding energy. One challenge linked with the use of CuCl is that it is sensitive to moist air i.e. CuCl is not stable in ambient conditions; it forms oxyhalides of Cu++ within a few hours or days of exposure to air. Therefore the use of CuCl for long-term applications is limited. To eliminate this drawback we have investigated the use of spin-coated organic-inorganic CuCl hybrid films. In an organic-inorganic hybrid film, the inorganic material is mixed with organic materials (polymer) to improve its physical, chemical, thermal and electrical properties, process simplicity, and stability. The impacts of atmospheric ageing effects on nanocrystalline CuCl hybrid films were investigated in order to avoid extra capping layer to protect CuCl degradation and extended its use in large scale applications. We show that CuCl-based hybrid films produced in this fashion have useful lifetimes of up to 3 months, which is approximately a two orders of magnitude improvement in the previously published usable lifetimes for optical emission in these materials, opening up the possibility that organic-inorganic CuCl hybrid films can indeed be useful materials for optoelectronic applications.

  18. Paternal-age effects on sperm aneuploidy investigated in mice and humans by three-chromosome fluorescence in situ hybridization

    SciTech Connect

    Wyrobek, A.J.; Lowe, X.; Holland, N.T.

    1994-09-01

    We conducted a cross-species comparison of the effects of paternal age on sperm aneuploidy in mice and humans. A new murine assay was developed to detect sperm hyperhaploidy and polyploidy for chromosomes X, Y, and 8 using fluorescence in situ hybridization with chromosome-specific DNA probes, to serve as a direct corollate to the three-chromosome method developed early for human sperm. Sperm aneuploidy was evaluated in eight male B6C3F1 male mice (aged 22.5-30.5 mo) and compared to young controls (2.4 mo). The aged group showed significant ({approximately}2.0-fold) increases in hyperhaploidies involving chromosomes X, Y and 8, with the greatest effects seen in the oldest animals. Sperm aneuploidy was also evaluated in two groups of healthy men who differed in mean age [46.8{plus_minus}3.1 (n=4) vs. 28.5{plus_minus}5.0 (n=10) yrs], using the three-chromosome method. The older group showed a statistically significant increase in hyperhaploid sperm for both sex chromosomes. Additional controlled human studies are planned. Taken together, the murine and human data are consistent with a positive effect of paternal age on sperm aneuploidy. In both species, the strongest age effect was observed for hyperhaploidies of chromosome Y. Future studies are needed to investigate the shape of the age-effect curve and to evaluate chromosomal differences, especially for humans in their late reproductive years.

  19. Mechanical properties and fabrication of small boat using woven glass/sugar palm fibres reinforced unsaturated polyester hybrid composite

    NASA Astrophysics Data System (ADS)

    Misri, S.; Leman, Z.; Sapuan, S. M.; Ishak, M. R.

    2010-05-01

    In recent years, sugar palm fibre has been found to have great potential to be used as fibre reinforcement in polymer matrix composites. This research investigates the mechanical properties of woven glass/sugar palm fibres reinforced unsaturated polyester hybrid composite. The composite specimens made of different layer of fibres such as strand mat, natural and hand woven of sugar palm fibres. The composites were fabricated using a compression moulding technique. The tensile and impact test was carried out in accordance to ASTM 5083 and ASTM D256 standard. The fibre glass boat is a familiar material used in boat industry. A lot of research on fabrication process such as lay-up, vacuum infusion mould and resin transfer mould has been conducted. Hybrid material of sugar palm fibre and fibre glass was used in fabricating the boat. This research investigates the method selection for fabrication of small boat application of natural fibre composites. The composite specimens made of different layer of fibres; woven glass fibre, strand mat, natural and hand woven of woven sugar palm fibres were prepared. The small boat were fabricated using a compression moulding and lay up technique. The results of the experiment showed that the tensile strength, tensile modulus, elongation at break value and impact strength were higher than the natural woven sugar palm fibre. The best method for fabricating the small boat was compression moulding technique. As a general conclusion, the usage of glass fibre had improved the tensile properties sugar palm fibre composites and compression moulding technique is suitable to be used in making a small boat application of natural fibre composites.

  20. The composite dynamic method as evidence for age-specific waterfowl mortality

    USGS Publications Warehouse

    Burnham, Kenneth P.; Anderson, David R.

    1979-01-01

    For the past 25 years estimation of mortality rates for waterfowl has been based almost entirely on the composite dynamic life table. We examined the specific assumptions for this method and derived a valid goodness of fit test. We performed this test on 45 data sets representing a cross section of banded sampled for various waterfowl species, geographic areas, banding periods, and age/sex classes. We found that: (1) the composite dynamic method was rejected (P <0.001) in 37 of the 45 data sets (in fact, 29 were rejected at P <0.00001) and (2) recovery and harvest rates are year-specific (a critical violation of the necessary assumptions). We conclude that the restrictive assumptions required for the composite dynamic method to produce valid estimates of mortality rates are not met in waterfowl data. Also we demonstrate that even when the required assumptions are met, the method produces very biased estimates of age-specific mortality rates. We believe the composite dynamic method should not be used in the analysis of waterfowl banding data. Furthermore, the composite dynamic method does not provide valid evidence for age-specific mortality rates in waterfowl.

  1. Critical interparticle distance for the remarkably enhanced dielectric constant of BaTiO3-Ag hybrids filled polyvinylidene fluoride composites

    NASA Astrophysics Data System (ADS)

    Luo, Suibin; Yu, Shuhui; Fang, Fang; Lai, Maobai; Sun, Rong; Wong, Ching-Ping

    2014-06-01

    Discrete nano Ag-deposited BaTiO3 (BT-Ag) hybrids with varied Ag content were synthesized, and the hybrids filled polyvinylidene fluoride (PVDF) composites were prepared. The effect of Ag content on the dielectric properties of the composites were analyzed based on the diffused electrical double layer theory. Results showed that with a higher Ag content in BT-Ag hybrids, the dielectric constant of BT-Ag/PVDF composites increases fast with the filler loading, while the dielectric loss and conductivity showed a suppressed and moderate increase. The dielectric constant of BT-0.61Ag/PVDF (61 wt. % of Ag in BT-Ag hybrid) composites reached 613, with the dielectric loss of 0.29 at 1 kHz. It was deduced that remarkably enhanced dielectric constant appeared when the interparticle distance decreased to a critical value of about 20 nm.

  2. Body Composition and Physiological Responses of Masters Female Swimmers 20 to 70 Years of Age.

    ERIC Educational Resources Information Center

    Vaccaro, Paul; And Others

    1984-01-01

    Female masters swimmers ranging in age from 20 to 69 were chosen for a study of their body composition and physiological responses at rest and during exercise. Two training groups were formed that differed on the basis of frequency, duration, and intensity of swimming workouts. Results are discussed. (Author/DF)

  3. Age-related changes in body composition in laboratory rats: Strain and gender comparisons

    EPA Science Inventory

    Long Evans (LE), Sprague Dawley (SD), Fischer 344 (F344), and Brown Norway (BN) rats are all commonly used as laboratory research subjects. These strains have been studied under many conditions, but few studies have measured changes in body composition as the animals age. Underst...

  4. Classroom Age Composition and Vocabulary Development among At-Risk Preschoolers

    ERIC Educational Resources Information Center

    Guo, Ying; Tompkins, Virginia; Justice, Laura; Petscher, Yaacov

    2014-01-01

    Research Findings: The purpose of this exploratory study was to examine the relationship between classroom age composition and preschoolers' vocabulary gains over an academic year and also to examine whether these relations were moderated by classroom quality. In this study (N = 130 children in 16 classrooms representing a subset of all…

  5. Evaluation of commercial lithium-ion cells based on composite positive electrode for plug-in hybrid electric vehicle applications. Part I: Initial characterizations

    SciTech Connect

    Matthieu Dubarry; Cyril Truchot; Mikael Cugnet; Bor Yann Liaw; Kevin Gering; Sergiy Sazhin; David Jamison; Christopher Michelbacher

    2011-12-01

    Evaluating commercial Li-ion batteries presents some unique benefits. One of them is to use cells made from established fabrication process and form factor, such as those offered by the 18650 cylindrical configuration, to provide a common platform to investigate and understand performance deficiency and aging mechanism of target chemistry. Such an approach shall afford us to derive relevant information without influence from processing or form factor variability that may skew our understanding on cell-level issues. A series of 1.9 Ah 18650 lithium ion cells developed by a commercial source using a composite positive electrode comprising (LiMn1/3Ni1/3Co1/3O2 + LiMn2O4) is being used as a platform for the investigation of certain key issues, particularly path-dependent aging and degradation in future plug-in hybrid electric vehicle (PHEV) applications, under the US Department of Energy's Applied Battery Research (ABR) program. Here we report in Part I the initial characterizations of the cell performance and Part II some aspects of cell degradation in 2C cycle aging. The initial characterizations, including cell-to-cell variability, are essential for life cycle performance characterization in the second part of the report when cell-aging phenomena are discussed. Due to the composite nature of the positive electrode, the features (or signature) derived from the incremental capacity (IC) of the cell appear rather complex. In this work, the method to index the observed IC peaks is discussed. Being able to index the IC signature in details is critical for analyzing and identifying degradation mechanism later in the cycle aging study.

  6. Surface structural changes of naturally aged silicone and EPDM composite insulators

    SciTech Connect

    Vlastos, A.E. ); Gubanski, S.M. )

    1991-04-01

    In a long-term outdoor test with high direct and alternating voltages, silicone and EPDM rubber composite insulators have, at the beginning, shown a superior performance to that of glass and porcelain insulators. In the long-term test, however, the silicone rubber composite insulator has, in spite of the ageing of both insulator types, kept its good performance, while the performance of the EPDM rubber composite insulator was drastically deteriorated. In order to get a better insight into results obtained, the wettability and the surface structural changes of the insulators were studied by the drop deposition method (using a goniometer) and by advanced techniques such as SEM, ESCA, FTIR and SIMS respectively. The results show that the differences in performance have to be found in the differences in the surface structural changes and in the dynamic ability of the surface to compensate the ageing.

  7. Cytotoxicity of urethane dimethacrylate composites before and after aging and leaching.

    PubMed

    Mohsen, N M; Craig, R G; Hanks, C T

    1998-02-01

    The in vitro cytotoxicity of urethane dimethacrylate composites cured at different times by visible light and after different aging times and extraction treatments was evaluated using succinic dehydrogenase activity in the mitochondria of a fibroblastic cell line to reflect cell viability. In addition, extractable chemicals associated with cell response were identified. The composite samples were tested untreated, polished, or extracted with water or 75% ethanol-water. Balb/c 3T3 fibroblasts were used as the cell culture system while MTT-formazan production was used as the toxicity parameter. Cell viability was calculated as a percentage of Teflon controls. Identification of the chemicals was measured by extracting the composites with 75% ethanol-water, separating the extract by HPLC, and identifying the fractions with mass spectroscopy. In general, cell viability increased continuously with curing time for differently treated samples at high aging times (288 h) while it decreased when the composites were not aged (0 h). In addition, for 75% ethanol or water-extracted composites, cell viability increased within the first 24 h of aging and reached a plateau after 72 h. Lowest cytotoxicity occurred when the samples were extracted with the 75% ethanol solution. The highest cytotoxic effects were found when the samples were untreated. Slightly reduced cytotoxic effects were seen with polished composites. The results suggest that curing the light-activated composites for a minimum of 150 s and post-curing for 24 h is required to attain comparable biocompatibility with the Teflon control. Removing the oxygen-inhibited layer from these composites decreased the cytotoxicity by 33% while extracting the composites with 75% ethanol-water decreased it by 77%. Chemicals released from the surface accounted for approximately 40% of cellular response while about 60% of the response was due to chemical components released from the bulk. The primary leachable component from the

  8. Age-dependent changes in matrix composition and organization at the ligament-to-bone insertion.

    PubMed

    Wang, I-Ning E; Mitroo, Siddarth; Chen, Faye H; Lu, Helen H; Doty, Stephen B

    2006-08-01

    Injuries to the anterior cruciate ligament (ACL) often occur at the ligament-to-bone insertion site; thus, an in-depth understanding of the native insertion is critical in identifying the etiology of failure and devising optimal treatment protocols for ACL injuries. The objective of this study is to conduct a systematic characterization of the ACL-to-bone interface, focusing on structural and compositional changes as a function of age. Using a bovine model, three age groups were studied: Neonatal (1-7 days old), Immature (2-6 months old), and Mature (2-5 years old). The distribution of types I, II, X collagen, decorin, cartilage oligomeric matrix protein (COMP), glycosaminoglycan (GAG), alkaline phosphatase (ALP) activity, and minerals at the ACL-to-bone insertion were examined. Additionally, cell aspect ratio, size, and distribution across the insertion were quantified. The ACL-to-bone insertion is divided into four regions: ligament, nonmineralized interface, mineralized interface, and bone. Both region-dependent and age-dependent structural and compositional changes at the insertion site were observed in this study. The interface in the skeletally immature group resembled articular cartilage, while the adult interface was similar to fibrocartilaginous tissue. Age-dependent changes in extracellular matrix composition (type X collagen, sulfated glycosaminoglycan), cellularity, ALP activity, and mineral distribution were also found. Marked differences in collagen fiber orientation between the femoral and tibial insertions were observed, and these differences became more pronounced with age.

  9. Researching Hybrid Learning Communities in the Digital Age through Educational Ethnography

    ERIC Educational Resources Information Center

    James, Nalita; Busher, Hugh

    2013-01-01

    This paper discusses the complexities of investigating the experiences of participants in hybrid (online/offline) learning communities through educational ethnography. In these communities, people construct small cultures in the liminal spaces or "border crossings" between the virtually real and "actually" real, using computer-mediated and…

  10. Influence of reinforcement type on the mechanical behavior and fire response of hybrid composites and sandwich structures

    NASA Astrophysics Data System (ADS)

    Giancaspro, James William

    Lightweight composites and structural sandwich panels are commonly used in marine and aerospace applications. Using carbon, glass, and a host of other high strength fiber types, a broad range of laminate composites and sandwich panels can be developed. Hybrid composites can be constructed by laminating multiple layers of varying fiber types while sandwich panels are manufactured by laminating rigid fiber facings onto a lightweight core. However, the lack of fire resistance of the polymers used for the fabrication remains a very important problem. The research presented in this dissertation deals with an inorganic matrix (Geopolymer) that can be used to manufacture laminate composites and sandwich panels that are resistant up to 1000°C. This dissertation deals with the influence of fiber type on the mechanical behavior and the fire response of hybrid composites and sandwich structures manufactured using this resin. The results are categorized into the following distinct studies. (i) High strength carbon fibers were combined with low cost E-glass fibers to obtain hybrid laminate composites that are both economical and strong. The E-glass fabrics were used as a core while the carbon fibers were placed on the tension face and on both tension and compression faces. (ii) Structural sandwich beams were developed by laminating various types of reinforcement onto the tension and compression faces of balsa wood cores. The flexural behavior of the beams was then analyzed and compared to beams reinforced with organic composite. The effect of core density was evaluated using oak beams reinforced with inorganic composite. (iii) To measure the fire response, balsa wood sandwich panels were manufactured using a thin layer of a fire-resistant paste to serve for fire protection. Seventeen sandwich panels were fabricated and tested to measure the heat release rates and smoke-generating characteristics. The results indicate that Geopolymer can be effectively used to fabricate both

  11. Magneto-rheological response of elastomer composites with hybrid-magnetic fillers

    NASA Astrophysics Data System (ADS)

    Aloui, Sahbi; Klüppel, Manfred

    2015-02-01

    We study the magneto-rheological response of hybrid-magnetic elastomer composites consisting of two different magnetic filler particles at fixed overall concentration. Thereby, we focus on an optimization of mechanical and magnetic properties by combining highly reinforcing magnetic nano-particles (MagSilica) with micro-sized carbonyl-iron particles (CIP), which exhibit high switch ability in a magnetic field. We observe a symbiotic interaction of both filler types, especially in the case when an orientation of the magnetic filler particles is achieved due to curing in an external magnetic field. The orientation effect is significant only for the micro-sized CIP particles with high saturation magnetization, indicating that the induced magnetic moment for the nano-sized particles is too small for delivering sufficient attraction between the particles in an external magnetic field. A pronounced switching behavior is observed for the non-cross-linked melts with 15 and 20 vol.% CIP, whereby the small strain modulus increases by more than 50%. For the sample without the coupling agent silane, one even observes a relative modulus increase of about 140%, which can be related to the combined effect of a higher mobility of the particles without a silane layer and the ability of the particles to come in close contact when they are arranged in strings along the field lines. For the cross-linked samples, a maximum switching effect of about 30% is achieved for the system with pure CIP. This magneto-sensitivity decreases successively if CIP is replaced by MagSilica, while the tensile strength of the systems increases significantly. The use of silane reduces the switching effect, but it is necessary for a good mechanical performance by delivering strong chemical bonding of the magnetic filler particles to the polymer matrix.

  12. A paper based graphene-nanocauliflower hybrid composite for point of care biosensing

    NASA Astrophysics Data System (ADS)

    Burrs, S. L.; Sidhu, R.; Bhargava, M.; Kiernan-Lewis, J.; Schwalb, N.; Rong, Y.; Gomes, C.; Claussen, J.; Vanegas, D. C.; McLamore, E. S.

    2016-05-01

    Graphene paper has diverse applications in printed circuit board electronics, bioassays, 3D cell culture, and biosensing. Although development of nanometal-graphene hybrid composites is commonplace in the sensing literature, to date there are only a few examples of nanometal-decorated graphene paper for use in biosensing. In this manuscript, we demonstrate the synthesis and application of Pt nano cauliflower-functionalized graphene paper for use in electrochemical biosensing of small molecules (glucose, acetone, methanol) or detection of pathogenic bacteria (Escherichia coli O157:H7). Raman spectroscopy, scanning electron microscopy and energy dispersive spectroscopy were used to show that graphene oxide deposited on nanocellulose crystals was partially reduced by both thermal and chemical treatment. Fractal platinum nanostructures were formed on the reduced graphene oxide paper, producing a conductive paper with an extremely high electroactive surface area, confirmed by cyclic voltammetry and electrochemical impedance spectroscopy. To show the broad applicability of the material, the platinum surface was functionalized with three different biomaterials: 1) glucose oxidase (via chitosan encapsulation); 2) a DNA aptamer (via covalent linking), or 3) a chemosensory protein (via his linking). We demonstrate the application of this device for point of care biosensing. The detection limit for both glucose (0.08 +/- 0.02 μM) and E. coli O157:H7 (1.3 +/- 0.1 CFU mL-1) were competitive with, or superior to, previously reported devices in the biosensing literature. The response time (6 sec for glucose and 10 min for E. coli) were also similar to silicon biochip and commercial electrode sensors. The results demonstrate that the nanocellulose-graphene-nanoplatinum material is an excellent paper-based platform for development of electrochemical biosensors targeting small molecules or whole cells for use in point of care biosensing.

  13. Fabrication, testing, and analysis of anisotropic carbon/glass hybrid composites: volume 1: technical report.

    SciTech Connect

    Wetzel, Kyle K. (Wetzel Engineering, Inc. Lawrence, Kansas); Hermann, Thomas M. (Wichita state University, Wichita, Kansas); Locke, James (Wichita state University, Wichita, Kansas)

    2005-11-01

    Anisotropic carbon/glass hybrid composite laminates have been fabricated, tested, and analyzed. The laminates have been fabricated using vacuum-assisted resin transfer molding (VARTM). Five fiber complexes and a two-part epoxy resin system have been used in the study to fabricate panels of twenty different laminate constructions. These panels have been subjected to physical testing to measure density, fiber volume fraction, and void fraction. Coupons machined from these panels have also been subjected to mechanical testing to measure elastic properties and strength of the laminates using tensile, compressive, transverse tensile, and in-plane shear tests. Interlaminar shear strength has also been measured. Out-of-plane displacement, axial strain, transverse strain, and inplane shear strain have also been measured using photogrammetry data obtained during edgewise compression tests. The test data have been reduced to characterize the elastic properties and strength of the laminates. Constraints imposed by test fixtures might be expected to affect measurements of the moduli of anisotropic materials; classical lamination theory has been used to assess the magnitude of such effects and correct the experimental data for the same. The tensile moduli generally correlate well with experiment without correction and indicate that factors other than end constraints dominate. The results suggest that shear moduli of the anisotropic materials are affected by end constraints. Classical lamination theory has also been used to characterize the level of extension-shear coupling in the anisotropic laminates. Three factors affecting the coupling have been examined: the volume fraction of unbalanced off-axis layers, the angle of the off-axis layers, and the composition of the fibers (i.e., carbon or glass) used as the axial reinforcement. The results indicate that extension/shear coupling is maximized with the least loss in axial tensile stiffness by using carbon fibers oriented 15{sup

  14. Temperature effect during humid ageing on interfaces of glass and carbon fibers reinforced epoxy composites.

    PubMed

    Ray, B C

    2006-06-01

    Weight change behavior of fiber-reinforced polymer composites in humid and thermal environments appears to be a complex phenomena. The state of fiber/matrix interface is believed to influence the nature of diffusion modes. A significant weakening often appears at the interface during the hygrothermal ageing. It effects the moisture uptake kinetics and also the reduction of mechanical properties. The importance of temperature at the time of conditioning plays an important role in environmental degradation of such composite materials. An attempt has been made here to evaluate the deleterious effect of temperature on shear strength of carbon/epoxy and glass/epoxy composites during hygrothermal conditionings. Mechanical tests were conducted at room temperature to assess the effectiveness of the relaxation process in the nullification of environmentally-induced damage in the composites.

  15. Analysis of aging of commercial composite metal oxide - Li4Ti5O12 battery cells

    NASA Astrophysics Data System (ADS)

    Svens, Pontus; Eriksson, Rickard; Hansson, Jörgen; Behm, Mårten; Gustafsson, Torbjörn; Lindbergh, Göran

    2014-12-01

    Commercial battery cells with Li4Ti5O12 negative electrode and composite metal oxide positive electrode have been analyzed with respect to aging mechanisms. Electrochemical impedance spectroscopy (EIS), differential capacity analysis (dQ/dV), differential voltage analysis (dV/dQ) and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) were used to identify different ageing mechanisms such as lithium inventory loss, loss of active electrode material and surface film growth. The active material of the positive electrode was also examined by X-ray diffraction (XRD). Aging mechanisms were studied for both calendar-aged and cycle-aged cells. Data from half cells prepared from post mortem harvested electrode material, using lithium foil as negative electrode and pouch material as encapsulation, were used as reference to full cell data. Electrochemical analysis of full and half cells combined with material analysis showed to be a powerful method to identify aging mechanisms in this type of commercial cells. The calendar-aged cell showed insignificant aging while the cycle-aged cell showed noticeable loss of positive electrode active material and loss of cyclable lithium, but only minor loss of negative electrode active material. The results imply that Li4Ti5O12 negative electrode material is a good alternative to other materials if high energy density is not the primary goal.

  16. Resin composite characterizations following a simplified protocol of accelerated aging as a function of the expiration date.

    PubMed

    D'Alpino, Paulo Henrique Perlatti; Vismara, Marcus Vinícius Gonçalves; Mello, Luciano Marcelo de Medeiros; Di Hipólito, Vinicius; González, Alejandra Hortencia Miranda; Graeff, Carlos Frederico de Oliveira

    2014-07-01

    This study evaluated the mechanical, thermal, and morphological characteristics of different classifications of dental composites as a function of the material condition (new, aged and expired). Specimens were obtained according to these factors: Composites: Filtek P60, Filtek Z250, Filtek Z350XT, and Filtek Silorane; and Material conditions: new, aged, and expired. The syringe composites underwent an accelerated aging protocol (Arrhenius model). The flexural strength (FS) and flexural modulus (E) were obtained. The thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were also performed and the glass transition temperature (Tg) and the weight loss calculated. Topographic analysis of the composites was performed under SEM. The material conditions influenced the mechanical properties of the composites. The silorane composite exhibited a characteristic thermal behavior different from that of the methacrylates. In general, the Tg increased after the accelerated aging protocol and decreased for expired ones, compared to the new composites. A significant increase in FS of Filtek Z350XT after aging was accompanied by an increase in the Tg. The filler packings were in accordance with the manufacture׳s information. The topographic aspects of the composites were modified as a function of the material condition. The mechanical properties of the composites following a simplified protocol of accelerated aging varied as a function of the expiration date. The silorane composite presented a characteristic thermal behavior. Although the dental manufacturers may not be able to control variables as storage temperature and transportation conditions, these effects on the composite clinical performance can be minimized if properly considered.

  17. Improved dielectric and mechanical properties of polystyrene-hybrid silica sphere composite induced through bifunctionalization at the interface.

    PubMed

    Sasikala, Thottunkal S; Nair, Bindu P; Pavithran, Chorappan; Sebastian, Mailadil T

    2012-06-26

    Hybrid silica spheres (HS) of size 270-350 nm with vinyl and aminopropyl surface groups were incorporated in polystyrene (PS), and its effect on dielectric properties, coefficient of thermal expansion (CTE), and strength of PS-HS composite was studied. Incorporation of HS in PS followed a decrease in the dielectric constant from 3.2 for PS to 2.6 for composite with 7.5 vol % HS. The decrease in the dielectric constant was attributed to (i) increased interfacial porosity, (ii) formation of anhydrous HS having low dielectric constant, during hot processing of the composites, and (iii) dispersion and preservation of the anhydrous HS in the hydrophobic matrix. The dielectric constant of the composites with HS content up to 7.5 vol % does not vary much with temperature in the range from -20 to 65 °C. These composites also exhibited reduced CTE and improved flexural strength/stiffness due to good interfacial bonding through HS vinyl groups and dispersion of the filler in the matrix. The dielectric loss increased with HS content, and the loss measured for 7.5 vol % PS-HS composite was 6 × 10(-3), as compared to 10(-4) for PS. At HS loading above 7.5 vol %, the tendency of HS to agglomerate and form percolated structure lead to an increase in the dielectric constant and decrease in the mechanical properties of the composites. PMID:22616660

  18. Characterization and modeling of viscoelastic composite laminates with nonisothermal physical aging

    NASA Astrophysics Data System (ADS)

    Bradshaw, Roger Dean

    Advanced fiber-reinforced composite materials are often used at temperatures that lead to time-dependent material behavior; such behavior must be understood and accounted for to ensure adequate design. This dissertation considers the time-dependence caused by physical aging, which is the evolution towards the equilibrium state in glassy solids, and its effect upon the mechanical response of a viscoelastic composite laminate. A predictive methodology is presented to determine the laminate stress-strain response to a general loading function during an arbitrary time-temperature history. This characterization assumes that the material is thermorheologically simple, that it remains linear viscoelastic, and that effective time theory can be used to incorporate the effects of physical aging. The first portion of the dissertation studies physical aging. A new method for recovering isothermal aging parameters that utilizes both load and unload test data is demonstrated; the results compare favorably to the traditional approach. The Kohlrausch compliance function, commonly used in physical aging studies, is shown to be an invalid material function at long times; a Prony series is a preferable representation. This method is then extended to characterize nonisothermal physical aging. It is demonstrated that a new parameter, called "effective aging time," adequately describes the nonisothermal aging state. A model to predict this parameter given the thermal history is presented and shown to adequately describe experimental results. Once the effective aging time is known, classical lamination theory (CLT) can be used with linear viscoelasticity to predict mechanical response. An approach is presented to calculate modulus behavior (convenient for CLT) from compliance behavior (typical result of testing). A prediction method is developed to incorporate the resulting modulus functions into CLT while maintaining the distinct aging behavior in the shear and transverse directions for

  19. Adjusting Measured Weight Loss of Aged Graphite Fabric/PMR-15 Composites

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.

    1998-01-01

    The purposes of this study were to evaluate the growth of the surface damage layer in polymer matrix composites (PMC's) fabricated with graphite fabric reinforcement and to determine the effects of the cut-surface degradation on the overall thermo-oxidative (TOS) stability of these materials. Four important conclusions were made about the TOS behavior of T650-35/PNIR- 15 fabric-reinforced composites: (1) Three stages of composite weight loss were seen on the plot of weight loss versus aging time; (2) the depth of the cut-edge damage is related to the composite thickness; (3) the actual weight loss realized by a mechanical test specimen that has had all the aging-induced cut-edge damage removed during the preparation process is significantly less than the weight loss measured using specimens with a high percentage of cut edges exposed to the damaging environment; and (4) an extrapolation of a section of the weight loss curve can be used to obtain a more correct estimate of the actual weight loss after extended periods of aging at elevated temperatures.

  20. Modeling of electric resistance of shape memory alloys: self-sensing for temperature and actuation control of active hybrid composites

    NASA Astrophysics Data System (ADS)

    Nissle, Sebastian; Hübler, Moritz; Gurka, Martin

    2016-04-01

    For actuation purposes active hybrid structures made of fiber reinforced polymers (FRP) and shape memory alloys (SMA) enable substantial savings concerning weight, space and cost. Such structures allow realizing new functions which are more or less impossible with commonly used systems consisting of the structure and the actuator as separated elements, e.g. morphing winglets in aeronautics. But there are also some challenges that still need to be addressed. For the successful application of SMA FRP composites a precise control of temperature is essential, as this is the activating quantity to reach the required deformation of the structure without overloading the active material. However, a direct measurement of the temperature is difficult due to the complete integration of SMA in the hybrid structure. Also the deformation of the structure which depends on the temperature, the stiffness of the hybrid structure and external loads is hard to determine. An opportunity for controlling the activation is provided by the special behavior of the electrical resistance of SMA. During the phase transformation of the SMA - also causing the actuation travel - the resistance drops with rising temperature. This behavior can be exploited for control purposes, especially as the electrical resistance can be easily measured during the activation done by Joule heating. As shown in this contribution, theoretical modelling and experimental tests provide a load-independent self-sensing control-concept of SMA-FRP-hybrid-structures.

  1. Aging and serum MCP-1 are associated with gut microbiome composition in a murine model

    PubMed Central

    Conley, Melissa N.; Wong, Carmen P.; Duyck, Kyle M.; Hord, Norman; Ho, Emily

    2016-01-01

    Introduction. Age is the primary risk factor for major human chronic diseases, including cardiovascular disorders, cancer, type 2 diabetes, and neurodegenerative diseases. Chronic, low-grade, systemic inflammation is associated with aging and the progression of immunosenescence. Immunosenescence may play an important role in the development of age-related chronic disease and the widely observed phenomenon of increased production of inflammatory mediators that accompany this process, referred to as “inflammaging.” While it has been demonstrated that the gut microbiome and immune system interact, the relationship between the gut microbiome and age remains to be clearly defined, particularly in the context of inflammation. The aim of our study was to clarify the associations between age, the gut microbiome, and pro-inflammatory marker serum MCP-1 in a C57BL/6 murine model. Results. We used 16S rRNA gene sequencing to profile the composition of fecal microbiota associated with young and aged mice. Our analysis identified an association between microbiome structure and mouse age and revealed specific groups of taxa whose abundances stratify young and aged mice. This includes the Ruminococcaceae, Clostridiaceae, and Enterobacteriaceae. We also profiled pro-inflammatory serum MCP-1 levels of each mouse and found that aged mice exhibited elevated serum MCP-1, a phenotype consistent with inflammaging. Robust correlation tests identified several taxa whose abundance in the microbiome associates with serum MCP-1 status, indicating that they may interact with the mouse immune system. We find that taxonomically similar organisms can exhibit differing, even opposite, patterns of association with the host immune system. We also find that many of the OTUs that associate with serum MCP-1 stratify individuals by age. Discussion. Our results demonstrate that gut microbiome composition is associated with age and the pro-inflammatory marker, serum MCP-1. The correlation between age

  2. Aging and serum MCP-1 are associated with gut microbiome composition in a murine model.

    PubMed

    Conley, Melissa N; Wong, Carmen P; Duyck, Kyle M; Hord, Norman; Ho, Emily; Sharpton, Thomas J

    2016-01-01

    Introduction. Age is the primary risk factor for major human chronic diseases, including cardiovascular disorders, cancer, type 2 diabetes, and neurodegenerative diseases. Chronic, low-grade, systemic inflammation is associated with aging and the progression of immunosenescence. Immunosenescence may play an important role in the development of age-related chronic disease and the widely observed phenomenon of increased production of inflammatory mediators that accompany this process, referred to as "inflammaging." While it has been demonstrated that the gut microbiome and immune system interact, the relationship between the gut microbiome and age remains to be clearly defined, particularly in the context of inflammation. The aim of our study was to clarify the associations between age, the gut microbiome, and pro-inflammatory marker serum MCP-1 in a C57BL/6 murine model. Results. We used 16S rRNA gene sequencing to profile the composition of fecal microbiota associated with young and aged mice. Our analysis identified an association between microbiome structure and mouse age and revealed specific groups of taxa whose abundances stratify young and aged mice. This includes the Ruminococcaceae, Clostridiaceae, and Enterobacteriaceae. We also profiled pro-inflammatory serum MCP-1 levels of each mouse and found that aged mice exhibited elevated serum MCP-1, a phenotype consistent with inflammaging. Robust correlation tests identified several taxa whose abundance in the microbiome associates with serum MCP-1 status, indicating that they may interact with the mouse immune system. We find that taxonomically similar organisms can exhibit differing, even opposite, patterns of association with the host immune system. We also find that many of the OTUs that associate with serum MCP-1 stratify individuals by age. Discussion. Our results demonstrate that gut microbiome composition is associated with age and the pro-inflammatory marker, serum MCP-1. The correlation between age

  3. Physical aging effects on the compressive linear viscoelastic creep of IM7/K3B composite

    NASA Technical Reports Server (NTRS)

    Veazie, David R.; Gates, Thomas S.

    1995-01-01

    An experimental study was undertaken to establish the viscoelastic behavior of 1M7/K3B composite in compression at elevated temperature. Creep compliance, strain recovery and the effects of physical aging on the time dependent response was measured for uniaxial loading at several isothermal conditions below the glass transition temperature (T(g)). The IM7/K3B composite is a graphite reinforced thermoplastic polyimide with a T(g) of approximately 240 C. In a composite, the two matrix dominated compliance terms associated with time dependent behavior occur in the transverse and shear directions. Linear viscoelasticity was used to characterize the creep/recovery behavior and superposition techniques were used to establish the physical aging related material constants. Creep strain was converted to compliance and measured as a function of test time and aging time. Results included creep compliance master curves, physical aging shift factors and shift rates. The description of the unique experimental techniques required for compressive testing is also given.

  4. Effect ofartificial accelerated aging on color stability and surface roughness of indirect composites.

    PubMed

    Zanin, Fabíola Rejane; Garcia, Lucas da Fonseca Roberti; Casemiro, Luciana Assirati; Pires-de-Souza, Fernanda de Carvalho Panzeri

    2008-03-01

    Direct and indirect composite resins have different forms of polymerization. Some materials require a post-cure system associating light and heat enhancing clinical properties. This study assessed the changes in color and surface roughness of three indirect composite resins after accelerated aging. Twelve specimens (15 x 2 mm) were obtained for each tested material. Subsequently, the first measurements for roughness tests and colorimetric spectrophotometry (CIE L*a*b* scale) were performed. Specimens were subject to accelerated aging for 384 hours. New measurements were then performed to evaluate the resulting change. Accelerated aging produced color change and increased surface roughness in all composite resins. Solidex resin showed color changes above the clinically accepted value (DeltaE = 4.31 +/- 0.22), and roughness values (Ra = 0.088 +/- 0.008 microm) statistically lower than that of Artglass (Ra = 0.141 +/- 0.026 microm) and Targis (Ra = 0.124 +/- 0.02 microm) (p<0.001). All the indirect resins tested showed color change and increased roughness after accelerated aging. Solidex showed color stability above a quantitative level considered clinically acceptable and lower roughness values compared to the other resins.

  5. Effects of physical aging on long-term behavior of composites

    NASA Technical Reports Server (NTRS)

    Brinson, L. Catherine

    1993-01-01

    The HSCT plane, envisioned to have a lifetime of over 60,000 flight hours and to travel at speeds in excess of Mach 2, is the source of intensive study at NASA. In particular, polymer matrix composites are being strongly considered for use in primary and secondary structures due to their high strength to weight ratio and the options of property tailoring. However, an added difficulty in the use of polymer based materials is that their properties change significantly over time, especially at the elevated temperatures that will be experienced during flight, and prediction of properties based on irregular thermal and mechanical loading is extremely difficult. This study focused on one aspect of long-term polymer composite behavior: physical aging. When a polymer is cooled to below its glass transition temperature, the material is not in thermodynamic equilibrium and the free volume and enthalpy evolve over time to approach their equilibrium values. During this time, the mechanical properties change significantly and this change is termed physical aging. This work begins with a review of the concepts of physical aging on a pure polymer system. The effective time theory, which can be used to predict long term behavior based on short term data, is mathematically formalized. The effects of aging to equilibrium are proven and discussed. The theory developed for polymers is then applied first to a unidirectional composite, then to a general laminate. Comparison to experimental data is excellent. It is shown that the effects of aging on the long-term properties of composites can be counter-intuitive, stressing the importance of the development and use of a predictive theory to analyze structures.

  6. Synergistic Effects of Physical Aging and Damage on Long-Term Behavior of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Brinson, L. Cate

    1999-01-01

    The research consisted of two major parts, first modeling and simulation of the combined effects of aging and damage on polymer composites and secondly an experimental phase examining composite response at elevated temperatures, again activating both aging and damage. For the simulation, a damage model for polymeric composite laminates operating at elevated temperatures was developed. Viscoelastic behavior of the material is accounted for via the correspondence principle and a variational approach is adopted to compute the temporal stresses within the laminate. Also, the effect of physical aging on ply level stress and on overall laminate behavior is included. An important feature of the model is that damage evolution predictions for viscoelastic laminates can be made. This allows us to track the mechanical response of the laminate up to large load levels though within the confines of linear viscoelastic constitutive behavior. An experimental investigation of microcracking and physical aging effects in polymer matrix composites was also pursued. The goal of the study was to assess the impact of aging on damage accumulation, in ten-ns of microcracking, and the impact of damage on aging and viscoelastic behavior. The testing was performed both at room and elevated temperatures on [+/- 45/903](sub s) and [02/903](sub s) laminates, both containing a set of 90 deg plies centrally located to facilitate investigation of microcracking. Edge replication and X-ray-radiography were utilized to quantify damage. Sequenced creep tests were performed to characterize viscoelastic and aging parameters. Results indicate that while the aging times studied have limited ]Influence on damage evolution, elevated temperature and viscoelastic effects have a profound effect on the damage mode seen. Some results are counterintuitive, including the lower strain to failure for elevated temperature tests and the catastrophic failure mode observed for the [+/- 45/9O3](sub s), specimens. The

  7. Conception axiomatique des joints hybrides a recouvrement simple en materiaux composites

    NASA Astrophysics Data System (ADS)

    Ouellet, Marc

    Minimizing weight is a primary objective in every system design in the aerospace and automotive industry. Therefore, the use of composite materials has become an integral part of the design of mechanical components. However, in composite structure design, their complexity normally makes it impossible to design them as a single part. This leads to the necessity of using joints. Sadly, these joints introduce discontinuities in the stress distribution within the components and are often the sites of stress concentration. Therefore, they may limit the performance of a structure, in addition to increasing the overall mass significantly due to the use of mechanical fasteners such as bolts and rivets. This is why bonded joints are increasingly popular. They are much lighter than bolted or riveted joints and are often more rigid. Unfortunately, it is very difficult to inspect a bonded joint for defects since the presence of cracks in the adhesive cannot be observed with the naked eye. The main objective of this work is to propose a new design methodology for hybrid joints. To accomplish this, it is necessary to establish reliable analysis tools to improve our understanding of the behavior of these joints when subjected to an external force. A better understanding of the interactions between the parameters is also required. To improve our knowledge on the subject, a literature review was conducted. This review was structured as to emphasize on the behavior of hybrid single lap joints when subjected to an external force in tension. Following this literature review, an analysis of the stress distribution within the joint was carried out using a finite element model. The model and the results were compared with those from two papers in order to validate the quality of representation. Subsequently, a modification was made to an existing analytical model in order to add the bolts' preload as a parameter. These two models, namely the finite element model and the analytical model

  8. The effects of environmental aging on the durability of glass/epoxy composites

    NASA Astrophysics Data System (ADS)

    Kajorncheappunngam, Somjai

    1999-11-01

    Glass fiber reinforced plastics (GFRPs) are beginning to be used as structural materials in construction. However, their mechanical properties can degrade after prolonged exposure to the environment. Understanding this degradation was the focus of this research. Epoxy neat resin and glass/epoxy composite samples were soaked in four different solutions (distilled water, saturated salt solution, 5 M NaOH, and 1 M HCl solution) for 5 months. The samples were also subjected to a combination of temperature and sustained load at room temperature and at 60°C. The glass transition temperature (Tg), storage modulus, tensile strength, and strain at failure were measured. The fracture surface of samples used in the tensile test were examined using a SEM. Results showed that immersion in aging media lowers Tg and enhances apparent phase separation in the samples due to polymer plasticization. At the elevated temperature, the Tg and the stiffness increased owing to continued resin curing. Sustained load, at the level used, had little effect on the mechanical behavior of the aged samples. At room temperature, water had the greatest influence in reducing the stiffness of epoxy neat resin samples. Combined effect of elevated temperature and sustained load caused an increase in Tg and a gain in stiffness in both epoxy neat resin and composite samples. This result is attributed more to the effect of temperature rather than to the effect of sustained load. At room temperature, glass/epoxy composite samples soaked in acid solution showed the highest reduction in tensile strength; this failure was the result of fiber damage. Other composite samples soaked in water and alkali were found to fail by adhesive failure mode. At 60°C, alkali was found to be the most damaging solution to glass/epoxy composite samples in terms of tensile strength. Here the composite samples failed under fiber failure mode while the composite samples soaked in water and acid solution failed under adhesive

  9. Individual Aerosol Particles from Biomass Burning in Southern Africa Compositions and Aging of Inorganic Particles. 2; Compositions and Aging of Inorganic Particles

    NASA Technical Reports Server (NTRS)

    Li, Jia; Posfai, Mihaly; Hobbs, Peter V.; Buseck, Peter R.

    2003-01-01

    Individual aerosol particles collected over southern Africa during the SAFARI 2000 field study were studied using transmission electron microscopy and field-emission scanning electron microscopy. The sizes, shapes, compositions, mixing states, surface coatings, and relative abundances of aerosol particles from biomass burning, in boundary layer hazes, and in the free troposphere were compared, with emphasis on aging and reactions of inorganic smoke particles. Potassium salts and organic particles were the predominant species in the smoke, and most were internally mixed. More KCl particles occur in young smoke, whereas more K2SO4 and KNO3 particles were present in aged smoke. This change indicates that with the aging of the smoke, KCl particles from the fires were converted to K2SO4 and KNO3 through reactions with sulfur- and nitrogen- bearing species from biomass burning as well as other sources. More soot was present in smoke from flaming grass fires than bush and wood fires, probably due to the predominance of flaming combustion in grass fires. The high abundance of organic particles and soluble salts can affect the hygroscopic properties of biomass-burning aerosols and therefore influence their role as cloud condensation nuclei. Particles from biomass burning were important constituents of the regional hazes.

  10. Effect of surface treatments on shear bond strength of resin composite bonded to CAD/CAM resin-ceramic hybrid materials

    PubMed Central

    Güngör, Merve Bankoğlu; Bal, Bilge Turhan; Ünver, Senem; Doğan, Aylin

    2016-01-01

    PURPOSE The purpose of this study was to assess the effect of surface treatments on shear bond strength of resin composite bonded to thermocycled and non-thermocycled CAD/CAM resin-ceramic hybrid materials. MATERIALS AND METHODS 120 specimens (10×10×2 mm) from each material were divided into 12 groups according to different surface treatments in combination with thermal aging procedures. Surface treatment methods were airborne-particle abrasion (abraded with 50 micron alumina particles), dry grinding (grinded with 125 µm grain size bur), and hydrofluoric acid (9%) and silane application. According to the thermocycling procedure, the groups were assigned as non-thermocycled, thermocycled after packing composites, and thermocycled before packing composites. The average surface roughness of the non-thermocycled specimens were measured after surface treatments. After packing composites and thermocycling procedures, shear bond strength (SBS) of the specimens were tested. The results of surface roughness were statistically analyzed by 2-way Analysis of Variance (ANOVA), and SBS results were statistically analyzed by 3-way ANOVA. RESULTS Surface roughness of GC were significantly lower than that of LU and VE (P<.05). The highest surface roughness was observed for dry grinding group, followed by airborne particle abraded group (P<.05). Comparing the materials within the same surface treatment method revealed that untreated surfaces generally showed lower SBS values. The values of untreated LU specimens showed significantly different SBS values compared to those of other surface treatment groups (P<.05). CONCLUSION SBS was affected by surface treatments. Thermocycling did not have any effect on the SBS of the materials except acid and silane applied GC specimens, which were subjected to thermocycling before packing of the composite resin. PMID:27555894

  11. Fracture toughness of human femoral neck: effect of microstructure, composition, and age.

    PubMed

    Yeni, Y N; Norman, T L

    2000-05-01

    The effects of porosity and pore size; osteonal area, size, and density; mineral content; water content; wet and dry apparent densities; and age on mode I (tensile) and mode II (shear) strain energy release rate were investigated for femoral neck cortical bone from human cadavers aged >/=50 years. The results suggest that porosity- and density-based parameters that are related to bone quantity are more consistently determinant for femoral neck fracture toughness than morphology-based parameters that are related to microstructural organization. Bone features examined here were more explanatory for shear than tension fracture toughness. Tension and shear fracture toughness did not change with age, unlike in previous reports investigating the femoral and tibial shaft. It was concluded that the femoral neck is different from the femoral and tibial shaft in terms of its microstructure and composition and in its relationship of fracture toughness to its constituents and age. PMID:10773590

  12. Hybrid-particulate composites based on an epoxy matrix, a reactive rubber, and glass beads: Morphology, viscoelastic, and mechanical properties

    SciTech Connect

    Maazouz, A.; Sautereau, H.; Gerard, J.F. . Lab. des Materiaux Macromoleculaires)

    1993-10-20

    The deformation and fracture behaviors of hybrid-particulate epoxy composites have been examined. These materials were based on a DGEBA/DDA matrix with various volume fractions of glass beads and different rubber contents. Young's modulus, yield stress, dynamic mechanical spectra, and fracture energy have been determined at room temperature. The Kerner model fits well the Young's modulus for the hybrid complexes with various glass bead contents. The analysis of the relaxation peak recorded from viscoelastic measurements allow us to discuss the influence of the introduction of the glass beads on the mobility of macromolecular chains and the characteristics of the rubber-separated phase. The fracture energy displays a strong improvement and synergism effect due to the presence of both kinds of particles. The toughening mechanisms were discussed.

  13. Effect of different light-curing devices and aging procedures on composite knoop microhardness.

    PubMed

    Voltarelli, Fernanda Regina; dos Santos-Daroz, Claudia Batitucci; Alves, Marcelo Corrêa; Peris, Alessandra Rezende; Marchi, Giselle Maria

    2009-01-01

    The aim of this study was to evaluate the effect of light-curing devices (Halogen/HAL, Light Emitting Diodes/LED, Argon Laser/LAS and Plasma Arc/PAC) and aging procedures (Mechanical Cycling/MC, Thermal Cycling/TC, Storage/S, MC+TC and MC+TC+S) on the micro-hardness of bottom/B and top/T surfaces of 2-mm-high composite resin cylinders. The Knoop microhardness test (25 g, 20 s) on both B and T was performed before and after each aging procedure. For B and T, before aging procedures, PAC showed reduced polymerization effectiveness when compared with HAL. In the T, after TC, PAC and LAS had also showed reduced polymerization effectiveness when compared to HAL and LED. For all light-curing devices, MC+TC+S and S affected the Knoop microhardness values. In the B, no difference could be observed among the aging procedures for PAC. From all light-curing units, PAC may have rendered composites of reduced quality and the storage aging procedures were the most harmful to the polymer hardness.

  14. Aging of Secondary Organic Aerosol from β-Pinene: Changes in Chemical Composition, Density and Morphology

    NASA Astrophysics Data System (ADS)

    Sarrafzadeh, M.; Hastie, D. R.

    2013-12-01

    Biogenic volatile organic compounds (VOC) are emitted in large quantities into the atmosphere. These VOC, which includes β-pinene, can react to produce secondary organic aerosols (SOA), which contribute to a substantial fraction of ambient organic aerosols and are known to adversely affect visibility, climate and health. Despite this, the current knowledge regarding the SOA composition, their physical properties and the chemical aging processes they undergo in the atmosphere is limited. In this study, chemical aging of SOA generated from the photooxidation of β-pinene was investigated in the York University smog chamber. The formation and aging of both gas and particle phase products were analyzed using an atmospheric pressure chemical ionization triple quadrupole mass spectrometer. The density of secondary organic matter was also simultaneously measured over the course of the aging experiments, allowing us to improve our understanding in changes in particle composition that may occur. In addition, particle phase and shape was investigated for generated particles from β-pinene oxidation by scanning electron microscope (SEM). Results of this work, including particle density and morphology will be presented as well as comparisons of gas and particle phase products time profiles during aging.

  15. [On the change in the isotopic composition of living beings during aging and evolution].

    PubMed

    Gladyshev, G P

    2013-01-01

    The article notes that the change in the isotopic composition of living beings during aging and in the evolution was predicted on the basis of the "principle of stability of matter". This principle was formulated by the author in the late 70's of the last century. New quantitative estimates were made, confirming the above prediction. To date, there are many studies that confirm those previously formulated approval by the author. These facts are a new confirmation of the thermodynamic theory of the origin of life, its evolution and aging of living beings.

  16. The effect of aging, temperature and brine composition on the mechanical strength of chalk

    NASA Astrophysics Data System (ADS)

    Korsnes, Reidar Inge; Nermoen, Anders; Stødle, Trond; Vika Storm, Eirik; Vadla Madland, Merete

    2014-05-01

    Chalk strength has been of great focus for several research communities since the 1980s when the Ekofisk subsidence problem was discovered. Sea water injection was initiated in 1987 to improve the oil production and to re-pressurize the reservoirs to halt the subsidence. The oil production was improved significantly, but the reservoir compaction in the water saturated regions continued, in contrast to the regions with no water breakthrough. This observation indicates a water weakening effect of the chalk. Extensive studies have been performed during the last decades to enlighten how the brine chemistry alters the rock mechanical properties. These studies have shown that the elastic bulk modulus, yield strength, creep and the deformation rate at constant stress conditions depend on the pore fluid composition. In general, the injected brine is in non-equilibrium with the rock surface inducing alteration of the rock mineralogy. In this study we examined two aspects of the mechanical strength, namely the bulk modulus and the onset of yield during hydrostatic stress loading with 0.7 MPa pore pressure. The test program consisted of aged and un-aged cores, ambient and 130°C test temperature, and four brine compositions: MgCl2, NaCl, Na2SO4, and synthetic sea water (SSW) at ion strengths of 0.657 M. The aging was performed by submerging saturated cores in a closed container with the respective test brine for three weeks at 130°C. Un-aged cores were saturated the same day as they were tested. For each brine composition we present four test setups; (a) aged and tested at 130°C, (b) aged and tested at ambient temperature, (c) un-aged and tested at 130°C, and (d) un-aged and tested at ambient conditions. The main results from our study are: 1. By using NaCl and MgCl2 as saturating brines, neither the test temperature nor the aging procedure affected the yield stress and bulk modulus significantly. 2. Using Na2SO4, the yield point and bulk moduli were reduced if the core

  17. Fatigue and Damage Tolerance Analysis of a Hybrid Composite Tapered Flexbeam

    NASA Technical Reports Server (NTRS)

    Murri, Gretchen B.; Schaff, Jeffrey R.; Dobyns, Al

    2001-01-01

    The behavior of nonlinear tapered composite flexbeams under combined axial tension and cyclic bending loading was studied using coupon test specimens and finite element (FE) analyses. The flexbeams used a hybrid material system of graphite/epoxy and glass/epoxy and had internal dropped plies, dropped in an overlapping stepwise pattern. Two material configurations, differing only in the use of glass or graphite plies in the continuous plies near the midplane, were studied. Test specimens were cut from a full-size helicopter tail-rotor flexbeam and were tested in a hydraulic load frame under combined constant axialtension load and transverse cyclic bending loads. The first determination damage observed in the specimens occurred at the area around the tip of the outermost ply-drop group in the tapered region of the flexbeam, near the thick end. Delaminations grew slowly and stably, toward the thick end of the flexbeam, at the interfaces above and below the dropped-ply region. A 2D finite element model of the flexbeam was developed. The model was analyzed using a geometrically non-linear analysis with both the ANSYS and ABAQUS FE codes. The global responses of each analysis agreed well with the test results. The ANSYS model was used to calculate strain energy release rates (G) for delaminations initiating at two different ply-ending locations. The results showed that delaminations were more inclined to grow at the locations where they were observed in the test specimens. Both ANSYS and ABAQUS were used to calculate G values associated with delamination initiating at the observed location but growing in different interfaces, either above or below the ply-ending group toward the thick end, or toward the thin end from the tip of the resin pocket. The different analysis codes generated the same trends and comparable peak values, within 5-11 % for each delamination path. Both codes showed that delamination toward the thick region was largely mode II, and toward the thin

  18. Isotopic composition analysis and age dating of uranium samples by high resolution gamma ray spectrometry

    NASA Astrophysics Data System (ADS)

    Apostol, A. I.; Pantelica, A.; Sima, O.; Fugaru, V.

    2016-09-01

    Non-destructive methods were applied to determine the isotopic composition and the time elapsed since last chemical purification of nine uranium samples. The applied methods are based on measuring gamma and X radiations of uranium samples by high resolution low energy gamma spectrometric system with planar high purity germanium detector and low background gamma spectrometric system with coaxial high purity germanium detector. The "Multigroup γ-ray Analysis Method for Uranium" (MGAU) code was used for the precise determination of samples' isotopic composition. The age of the samples was determined from the isotopic ratio 214Bi/234U. This ratio was calculated from the analyzed spectra of each uranium sample, using relative detection efficiency. Special attention is paid to the coincidence summing corrections that have to be taken into account when performing this type of analysis. In addition, an alternative approach for the age determination using full energy peak efficiencies obtained by Monte Carlo simulations with the GESPECOR code is described.

  19. Effect of mat pilates exercise on postural alignment and body composition of middle-aged women.

    PubMed

    Lee, Hyo Taek; Oh, Hyun Ok; Han, Hui Seung; Jin, Kwang Youn; Roh, Hyo Lyun

    2016-06-01

    [Purpose] This study attempted to examine whether Pilates is an effective exercise for improving the postural alignment and health of middle-aged women. [Subjects and Methods] The participants in this study were 36 middle-aged women (20 in the experimental group, 16 in the control group). The experimental group participated in Pilates exercise sessions three times a week for 12 weeks. Body alignment and composition measurements before and after applying the Pilates exercise program were performed with a body composition analyzer and a three-dimensional scanner. [Results] Postural alignment in the sagittal and horizontal planes was enhanced in the Pilates exercise group. Trunk alignment showed correlations with body fat and muscle mass. [Conclusion] The Pilates exercises are performed symmetrically and strengthen the deep muscles. Moreover, the results showed that muscle mass was correlated with trunk postural alignment and that the proper amount of muscle is critical in maintaining trunk postural alignment.

  20. Effect of mat pilates exercise on postural alignment and body composition of middle-aged women

    PubMed Central

    Lee, Hyo Taek; Oh, Hyun Ok; Han, Hui Seung; Jin, Kwang Youn; Roh, Hyo Lyun

    2016-01-01

    [Purpose] This study attempted to examine whether Pilates is an effective exercise for improving the postural alignment and health of middle-aged women. [Subjects and Methods] The participants in this study were 36 middle-aged women (20 in the experimental group, 16 in the control group). The experimental group participated in Pilates exercise sessions three times a week for 12 weeks. Body alignment and composition measurements before and after applying the Pilates exercise program were performed with a body composition analyzer and a three-dimensional scanner. [Results] Postural alignment in the sagittal and horizontal planes was enhanced in the Pilates exercise group. Trunk alignment showed correlations with body fat and muscle mass. [Conclusion] The Pilates exercises are performed symmetrically and strengthen the deep muscles. Moreover, the results showed that muscle mass was correlated with trunk postural alignment and that the proper amount of muscle is critical in maintaining trunk postural alignment. PMID:27390396

  1. Effect of mat pilates exercise on postural alignment and body composition of middle-aged women.

    PubMed

    Lee, Hyo Taek; Oh, Hyun Ok; Han, Hui Seung; Jin, Kwang Youn; Roh, Hyo Lyun

    2016-06-01

    [Purpose] This study attempted to examine whether Pilates is an effective exercise for improving the postural alignment and health of middle-aged women. [Subjects and Methods] The participants in this study were 36 middle-aged women (20 in the experimental group, 16 in the control group). The experimental group participated in Pilates exercise sessions three times a week for 12 weeks. Body alignment and composition measurements before and after applying the Pilates exercise program were performed with a body composition analyzer and a three-dimensional scanner. [Results] Postural alignment in the sagittal and horizontal planes was enhanced in the Pilates exercise group. Trunk alignment showed correlations with body fat and muscle mass. [Conclusion] The Pilates exercises are performed symmetrically and strengthen the deep muscles. Moreover, the results showed that muscle mass was correlated with trunk postural alignment and that the proper amount of muscle is critical in maintaining trunk postural alignment. PMID:27390396

  2. On the Use of Accelerated Aging Methods for Screening High Temperature Polymeric Composite Materials

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.; Grayson, Michael A.

    1999-01-01

    A rational approach to the problem of accelerated testing of high temperature polymeric composites is discussed. The methods provided are considered tools useful in the screening of new materials systems for long-term application to extreme environments that include elevated temperature, moisture, oxygen, and mechanical load. The need for reproducible mechanisms, indicator properties, and real-time data are outlined as well as the methodologies for specific aging mechanisms.

  3. The Effects of Fiber Surface Modification and Thermal Aging on Composite Toughness And its Measurement

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.; Madhukar, Madhu; Papadopoulos, Demetrios; Inghram, Linda; McCorkle, Linda

    1997-01-01

    A detailed experimental study was conducted to establish the structure-property relationships between elevated temperature aging and (I) fiber-matrix bonding, (2) Mode II interlaminar fracture toughness, and (3) failure modes of carbon fiber/PMR-15 composites. The fiber-matrix adhesion was varied by using carbon fibers with different surface treatments. Short beam shear tests were used to quantify the interfacial shear strength afforded by the use of the different fiber surface treatments. The results of the short beam shear tests definitely showed that, for aging times up to 1000 hr, the aging process caused no observable changes in the bulk of the three composite materials that---would degrade the shear properties of the material. Comparisons between the interlaminar shear strength (ILSS) measured by the short beam shear tests and the GII c test results, as measured by the ENF test, indicated that the differences in the surface treatments significantly affected the fracture properties while the effect of the aging process was probably limited to changes at the starter crack tip. The fracture properties changed due to a shift in the fracture from an interfacial failure to a failure within the matrix when the fiber was changed from AU-4 to AS-4 or AS-4G. There appears to be an effect of the fiber/matrix bonding on the thermo-oxidative stability of the composites that were tested. The low bonding afforded by the AU-4 fiber resulted in weight losses about twice those experienced by the AS-4 reinforced composites, the ones with the best TOS.

  4. Synthesis of g-C3N4/NaTaO3 Hybrid Composite Photocatalysts and Their Photocatalytic Activity Under Simulated Solar Light Irradiation.

    PubMed

    Kim, Tae-Ho; Jo, Yong-Hyun; Soo-Wohn; Adhikari, Rajesh; Cho, Sung-Hun

    2015-09-01

    This Paper reports the photocatalytic activity of g-C3N4/NaTaO3 hybrid composite photocatalysts synthesized by ball-mill method. The g-C3N4 and NaTaO3 were individually prepared by Solid state reaction and microwave hydrothermal process, respectively. The g-C3N4/NaTaO3 composite showed the enhanced photocatalytic activity for degradation of rhodamine B dye (Rh. B) under simulated solar light irradiation. The results revealed that the band-gap energy absorption edge of hybrid composite samples was shifted to a longer wavelength as compared to NaTaO3 and the 50 wt% g-C3N4/NaTaO3 hybrid composite exhibited the highest percentage (99.6%) of degradation of Rh. B and the highest reaction rate constant (0.013 min(-1)) in 4 h which could be attributed to the enhanced absorption of the hybrid composite photocatalyst in the UV-Vis region. Hence, these results suggest that the g-C3N4/NaTaO3 hybrid composite exhibits enhanced photocatalytic activity for the degradation of rhodamine B under simulated solar light irradiation in comparison to the commercial NaTaO3. PMID:26716296

  5. Synthesis of g-C3N4/NaTaO3 Hybrid Composite Photocatalysts and Their Photocatalytic Activity Under Simulated Solar Light Irradiation.

    PubMed

    Kim, Tae-Ho; Jo, Yong-Hyun; Soo-Wohn; Adhikari, Rajesh; Cho, Sung-Hun

    2015-09-01

    This Paper reports the photocatalytic activity of g-C3N4/NaTaO3 hybrid composite photocatalysts synthesized by ball-mill method. The g-C3N4 and NaTaO3 were individually prepared by Solid state reaction and microwave hydrothermal process, respectively. The g-C3N4/NaTaO3 composite showed the enhanced photocatalytic activity for degradation of rhodamine B dye (Rh. B) under simulated solar light irradiation. The results revealed that the band-gap energy absorption edge of hybrid composite samples was shifted to a longer wavelength as compared to NaTaO3 and the 50 wt% g-C3N4/NaTaO3 hybrid composite exhibited the highest percentage (99.6%) of degradation of Rh. B and the highest reaction rate constant (0.013 min(-1)) in 4 h which could be attributed to the enhanced absorption of the hybrid composite photocatalyst in the UV-Vis region. Hence, these results suggest that the g-C3N4/NaTaO3 hybrid composite exhibits enhanced photocatalytic activity for the degradation of rhodamine B under simulated solar light irradiation in comparison to the commercial NaTaO3.

  6. Physicochemical composition of osteoporotic bone in the trichothiodystrophy premature aging mouse determined by confocal Raman microscopy.

    PubMed

    van Apeldoorn, Aart A; de Boer, Jan; van Steeg, Harry; Hoeijmakers, Jan H J; Otto, Cees; van Blitterswijk, Clemens A

    2007-01-01

    Although it has been established that premature aging trichothiodystrophy (TTD) mice display typical signs of osteoporosis, exact changes in physicochemical properties of these mice have not been elucidated. We used confocal Raman microscopy and histology to study femora of TTD mice. We measured femora isolated from xeroderma pigmentosum group A (XPA)/TTD double mutant mice to establish that Raman microscopy can be applied to measure differences in bone composition. Raman data from XPA/TTD mice showed remarkable changes in bone mineral composition. Moreover, we observed a severe form of osteoporosis, with strongly reduced cortical bone thickness. We used Raman microscopy to analyze bone composition in eight wild-type and eight TTD animals, and observed decreased levels of phosphate and carbonate in the cortex of femora isolated from TTD mice. In contrast, the bands representing the bone protein matrix were not affected in these mice.

  7. Long-term influence of physical aging processes in epoxy matrix composites

    NASA Technical Reports Server (NTRS)

    Kong, E. S. W.

    1981-01-01

    Selected mechanical properties of (plus or minus 45 degree sub 4s) graphite/epoxy composites were found to be affected by sub T sub g annealing. Postcured specimens of Thornel 300 graphite/Narmco 5208 epoxy were sub T sub G annealed at 413 K (140 C) for ca. 10 to the first through 10 to the fifth powers min., with a prior quenching from above T sub g. The ultimate tensile strength, strain-to-break, and toughness of the composite were found to decrease as a function of sub T sub g annealing time. The time-dependent change in properties can be explained on the basis of physical aging which is related to free volume changes in the non-equilibrium glassy state of network epoxies. The results imply possible changes in composite properties with service time.

  8. Age-dependent changes in the sphingolipid composition of CD4+ T cell membranes and immune synapses implicate glucosylceramides in age-related T cell dysfunction

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sphingolipid (SL4) composition can influence the biophysical properties of cell membranes. Additionally, specific SL modulate signaling pathways involved in proliferation, senescence, and apoptosis. We investigated age-dependent changes in the SL composition of CD4+ T cells, and the impact of these ...

  9. Thermo-mechanical characterization of siliconized E-glass fiber/hematite particles reinforced epoxy resin hybrid composite

    NASA Astrophysics Data System (ADS)

    V. R., Arun prakash; Rajadurai, A.

    2016-10-01

    In this present work hybrid polymer (epoxy) matrix composite has been strengthened with surface modified E-glass fiber and iron(III) oxide particles with varying size. The particle sizes of 200 nm and <100 nm has been prepared by high energy ball milling and sol-gel methods respectively. To enhance better dispersion of particles and improve adhesion of fibers and fillers with epoxy matrix surface modification process has been done on both fiber and filler by an amino functional silane 3-Aminopropyltrimethoxysilane (APTMS). Crystalline and functional groups of siliconized iron(III) oxide particles were characterized by XRD and FTIR spectroscopy analysis. Fixed quantity of surface treated 15 vol% E-glass fiber was laid along with 0.5 and 1.0 vol% of iron(III) oxide particles into the matrix to fabricate hybrid composites. The composites were cured by an aliphatic hardener Triethylenetetramine (TETA). Effectiveness of surface modified particles and fibers addition into the resin matrix were revealed by mechanical testing like tensile testing, flexural testing, impact testing, inter laminar shear strength and hardness. Thermal behavior of composites was evaluated by TGA, DSC and thermal conductivity (Lee's disc). The scanning electron microscopy was employed to found shape and size of iron(III) oxide particles adhesion quality of fiber with epoxy matrix. Good dispersion of fillers in matrix was achieved with surface modifier APTMS. Tensile, flexural, impact and inter laminar shear strength of composites was improved by reinforcing surface modified fiber and filler. Thermal stability of epoxy resin was improved when surface modified fiber was reinforced along with hard hematite particles. Thermal conductivity of epoxy increased with increase of hematite content in epoxy matrix.

  10. Difference in Leukocyte Composition between Women before and after Menopausal Age, and Distinct Sexual Dimorphism

    PubMed Central

    Chen, Chang; Yang, Peixuan; Ye, Shu; Tan, Xuerui

    2016-01-01

    There are sex differences in many inflammatory and immune diseases, and the differences tend to diminish after menopause. The underlying reasons are unclear, but sex hormone levels are likely to be an important factor. Blood leukocyte count and composition provide an indicator of the inflammatory and immune status of an individual. We performed a cross-sectional analysis of blood leukocyte data from 46,879 individuals (26,212 men and 20,667 women, aged 18 to 93 years) who underwent a routine health checkup. In women aged around 50 years, neutrophil percentage (NE%) dropped whilst lymphocyte percentage (LY%) rose. Accordingly, women before age 50 had significantly higher NE%, lower LY%, and higher neutrophil-to-lymphocyte ratio (NLR) than women of 51–70 years of age (p = 1.35×10−82, p = 5.32×10−100, and p = 1.25×10−26, respectively). In age groups of <50 years, women had higher NE%, lower LY% and higher NLR than men (p = 1.82×10−206, p = 1.46×10−69, and p = 2.30×10−118, respectively), whereas in age groups of >51 years, it was the reverse (p = 1.92×10−15, p = 1.43×10−84, and p = 1.51×10−48, respectively). These results show that blood leukocyte composition differs between women before and after menopausal age, with distinct sexual dimorphism. PMID:27657912

  11. Sources of variability in peat composition and the role of peat age

    NASA Astrophysics Data System (ADS)

    Leifeld, Jens

    2016-04-01

    During peat formation decaying plant material undergoes partial decomposition that continuously transform its organic matter. As part of this transformation, aromatic moieties such as plant-borne polyphenols are considered to accumulate relative to more labile compounds such as carbohydrates. Here, 13C CPMAS-NMR data from 71 peat samples from sites across Europe (61°48' N - 46°49' N) are analyzed for their variability. Sites differ in their degree of peat disturbance and range from natural to long-term drained and thus strongly degraded. Application of a molecular mixing model to the NMR data indicated that, on average, peat consists by 27, 22, 21, 18, and 11 % of carbohydrates, aliphatics, aromatics, proteins, and char, respectively. Compositional variability was most pronounced for aromatics and carbohydrates. So far, half of the samples was age-dated using 14C. Calibrated 14C ages in the data set range from recent to c. 10000 years BP. Relationships between peat composition and age were non-linear and highly significant. Aromatic moieties accumulated with increasing peat age whereas O-containing moieties relatively declined, in line with a decrease in molar O/C ratios. The relative accumulation of aromatics was 250 % during 10000 years whereas O-containing moieties declined relatively by 65 %. About half of this selective accumulation and degradation occurred during the first 2000 years of peat accumulation, thereby reflecting higher microbial transformation rates during initial phases of built-up. Char content increased with peat age, possibly indicating selective preservation of char during peat formation. C/N ratios correlated significantly but bi-modal with age. The analysis shows that peat age is a reliable proxy for organic matter transformation in peatlands. Because rates and degree of transformation are derived from multiple sites, the found relationships seem to reveal a general pattern, at least for the studied boreal and temperate systems.

  12. Specimen geometry effects on graphite/PMR-15 composites during thermo-oxidative aging

    NASA Technical Reports Server (NTRS)

    Bowles, K. J.; Meyers, A.

    1986-01-01

    Studies were conducted to establish the effects of specimen geometry on the thermo-oxidative stability and the mechanical properties retention of unidirectional Celion 12000 graphite fiber reinforced PMR-15 polyimide composites. Weight loss, flexural strength and interlaminar shear strength are measured at isothermal aging times as long as 1639 hr at a temperature of 316 C for three different specimen geometries. It is found that the three different types of specimen surfaces exhibit different values of weight loss/unit area. The mechanical properties retention is also found to be dependent on geometry for these composites. The interlaminar shear strength decreases significantly over the complete range of aging times. The flexural strength retention starts showing geometric dependency after about 1000 hr of aging at 316C. Weight loss fluxes, associated with the three different types of exposed surfaces, are calculated and used to develop an empirical mathematical model for predicting the weight loss behavior of unidirectional composites of arbitrary geometries. Data are presented comparing experimentally determined weight loss with weight loss values predicted using the empirical model.

  13. Does Human Milk Modulate Body Composition in Late Preterm Infants at Term-Corrected Age?

    PubMed Central

    Giannì, Maria Lorella; Consonni, Dario; Liotto, Nadia; Roggero, Paola; Morlacchi, Laura; Piemontese, Pasqua; Menis, Camilla; Mosca, Fabio

    2016-01-01

    (1) Background: Late preterm infants account for the majority of preterm births and are at risk of altered body composition. Because body composition modulates later health outcomes and human milk is recommended as the normal method for infant feeding, we sought to investigate whether human milk feeding in early life can modulate body composition development in late preterm infants; (2) Methods: Neonatal, anthropometric and feeding data of 284 late preterm infants were collected. Body composition was evaluated at term-corrected age by air displacement plethysmography. The effect of human milk feeding on fat-free mass and fat mass content was evaluated using multiple linear regression analysis; (3) Results: Human milk was fed to 68% of the infants. According to multiple regression analysis, being fed any human milk at discharge and at  term-corrected and being fed exclusively human milk at term-corrected age were positively associated with fat-free mass content(β = −47.9, 95% confidence interval (CI) = −95.7; −0.18; p = 0.049; β = −89.6, 95% CI = −131.5; −47.7; p < 0.0001; β = −104.1, 95% CI = −151.4; −56.7, p < 0.0001); (4) Conclusion: Human milk feeding appears to be associated with fat-free mass deposition in late preterm infants. Healthcare professionals should direct efforts toward promoting and supporting breastfeeding in these vulnerable infants. PMID:27782098

  14. Body Composition, Sarcopenia, and Suicidal Ideation in Elderly Koreans: Hallym Aging Study

    PubMed Central

    2016-01-01

    This study was conducted to assess the relationship between body composition and suicidal ideation among the Korean elderly population (n = 302; ≥ 65 years) who participated in the Hallym Aging Study in 2010. Body composition was measured using dual-energy X-ray absorptiometry, and obesity was measured by the indices of body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), waist-to-height ratio (WHtR), and body fat percentage. Sarcopenia was defined as presence of both low muscle mass and low muscle function. Suicidal ideation was assessed using the Beck Scale for Suicide Ideation. We found no differences in body composition measures between subjects with suicidal ideation and those without. In the logistic regression analyses, there were no significant relationships for suicidal ideation according to body composition measures, including BMI, WC, WHR, WHtR, and body fat percentage in both sexes. After adjusting for age, smoking status, alcohol drinking, regular exercise, medical comorbidities, monthly income, education level, and presence of depressive symptoms, the odds ratio (OR) of suicidal ideation was higher in elderly men with sarcopenia compared to those without, whereas no significant relationships were observed in elderly women (OR 8.28, 95% confidence interval [CI] 1.20–61.34 in men; OR 0.79, 95% CI 0.07–8.43 in women). Sarcopenia is closely associated with an increased risk of suicidal ideation in elderly men. PMID:27051246

  15. Behavioural early-life exposures and body composition at age 15 years

    PubMed Central

    Leary, S D; Lawlor, D A; Davey Smith, G; Brion, M J; Ness, A R

    2015-01-01

    Background/Objectives: Previous studies have demonstrated associations between some early-life exposures and later obesity, but most have used body mass index in childhood or adulthood as the outcome. The objective of this study was to investigate whether early-life exposures were associated with directly measured fat and lean mass in adolescence. Subjects/Methods: This study used data on 4750 mother–offspring pairs, collected as a part of the Avon Longitudinal Study of Parents and Children, Bristol, UK between 1991 and 1992; associations between behavioural exposures occurring from conception up to 5 years of age (maternal and paternal smoking during pregnancy, breastfeeding, age at introduction to solids, dietary patterns and physical inactivity during early childhood) and offspring body composition measured by dual-energy X-ray absorptiometry at ~15 years were assessed. Results: After full adjustment for potential confounders, maternal smoking during pregnancy, having a junk food diet and spending more time watching television in early childhood were all associated with higher fat mass at age 15, whereas maternal smoking, having a healthy diet and playing computer games more frequently in early childhood were all associated with a higher lean mass at age 15. Associations with paternal smoking were generally weaker for both fat and lean mass, but as there was no strong statistical evidence for maternal vs paternal differences, confounding by social factors rather than a direct effect of maternal smoking cannot be ruled out. Early feeding was not associated with fat or lean mass at age 15. Conclusions: This study does not provide compelling evidence for associations between most early-life factors and body composition in adolescence. However, possible associations with dietary patterns and physical inactivity in early childhood require further investigation in other cohorts that have direct measurements of adolescent body composition. PMID:25664839

  16. Enhanced dielectric properties of poly(vinylidene fluoride) composites filled with nano iron oxide-deposited barium titanate hybrid particles

    NASA Astrophysics Data System (ADS)

    Zhang, Changhai; Chi, Qingguo; Dong, Jiufeng; Cui, Yang; Wang, Xuan; Liu, Lizhu; Lei, Qingquan

    2016-09-01

    We report enhancement of the dielectric permittivity of poly(vinylidene fluoride) (PVDF) generated by depositing magnetic iron oxide (Fe3O4) nanoparticles on the surface of barium titanate (BT) to fabricate BT–Fe3O4/PVDF composites. This process introduced an external magnetic field and the influences of external magnetic field on dielectric properties of composites were investigated systematically. The composites subjected to magnetic field treatment for 30 min at 60 °C exhibited the largest dielectric permittivity (385 at 100 Hz) when the BT–Fe3O4 concentration is approximately 33 vol.%. The BT–Fe3O4 suppressed the formation of a conducting path in the composite and induced low dielectric loss (0.3) and low conductivity (4.12 × 10‑9 S/cm) in the composite. Series-parallel model suggested that the enhanced dielectric permittivity of BT–Fe3O4/PVDF composites should arise from the ultrahigh permittivity of BT–Fe3O4 hybrid particles. However, the experimental results of the BT–Fe3O4/PVDF composites treated by magnetic field agree with percolation theory, which indicates that the enhanced dielectric properties of the BT–Fe3O4/PVDF composites originate from the interfacial polarization induced by the external magnetic field. This work provides a simple and effective way for preparing nanocomposites with enhanced dielectric properties for use in the electronics industry.

  17. Enhanced dielectric properties of poly(vinylidene fluoride) composites filled with nano iron oxide-deposited barium titanate hybrid particles

    PubMed Central

    Zhang, Changhai; Chi, Qingguo; Dong, Jiufeng; Cui, Yang; Wang, Xuan; Liu, Lizhu; Lei, Qingquan

    2016-01-01

    We report enhancement of the dielectric permittivity of poly(vinylidene fluoride) (PVDF) generated by depositing magnetic iron oxide (Fe3O4) nanoparticles on the surface of barium titanate (BT) to fabricate BT–Fe3O4/PVDF composites. This process introduced an external magnetic field and the influences of external magnetic field on dielectric properties of composites were investigated systematically. The composites subjected to magnetic field treatment for 30 min at 60 °C exhibited the largest dielectric permittivity (385 at 100 Hz) when the BT–Fe3O4 concentration is approximately 33 vol.%. The BT–Fe3O4 suppressed the formation of a conducting path in the composite and induced low dielectric loss (0.3) and low conductivity (4.12 × 10−9 S/cm) in the composite. Series-parallel model suggested that the enhanced dielectric permittivity of BT–Fe3O4/PVDF composites should arise from the ultrahigh permittivity of BT–Fe3O4 hybrid particles. However, the experimental results of the BT–Fe3O4/PVDF composites treated by magnetic field agree with percolation theory, which indicates that the enhanced dielectric properties of the BT–Fe3O4/PVDF composites originate from the interfacial polarization induced by the external magnetic field. This work provides a simple and effective way for preparing nanocomposites with enhanced dielectric properties for use in the electronics industry. PMID:27633958

  18. Enhanced dielectric properties of poly(vinylidene fluoride) composites filled with nano iron oxide-deposited barium titanate hybrid particles.

    PubMed

    Zhang, Changhai; Chi, Qingguo; Dong, Jiufeng; Cui, Yang; Wang, Xuan; Liu, Lizhu; Lei, Qingquan

    2016-01-01

    We report enhancement of the dielectric permittivity of poly(vinylidene fluoride) (PVDF) generated by depositing magnetic iron oxide (Fe3O4) nanoparticles on the surface of barium titanate (BT) to fabricate BT-Fe3O4/PVDF composites. This process introduced an external magnetic field and the influences of external magnetic field on dielectric properties of composites were investigated systematically. The composites subjected to magnetic field treatment for 30 min at 60 °C exhibited the largest dielectric permittivity (385 at 100 Hz) when the BT-Fe3O4 concentration is approximately 33 vol.%. The BT-Fe3O4 suppressed the formation of a conducting path in the composite and induced low dielectric loss (0.3) and low conductivity (4.12 × 10(-9) S/cm) in the composite. Series-parallel model suggested that the enhanced dielectric permittivity of BT-Fe3O4/PVDF composites should arise from the ultrahigh permittivity of BT-Fe3O4 hybrid particles. However, the experimental results of the BT-Fe3O4/PVDF composites treated by magnetic field agree with percolation theory, which indicates that the enhanced dielectric properties of the BT-Fe3O4/PVDF composites originate from the interfacial polarization induced by the external magnetic field. This work provides a simple and effective way for preparing nanocomposites with enhanced dielectric properties for use in the electronics industry. PMID:27633958

  19. Enhanced dielectric properties of poly(vinylidene fluoride) composites filled with nano iron oxide-deposited barium titanate hybrid particles.

    PubMed

    Zhang, Changhai; Chi, Qingguo; Dong, Jiufeng; Cui, Yang; Wang, Xuan; Liu, Lizhu; Lei, Qingquan

    2016-09-16

    We report enhancement of the dielectric permittivity of poly(vinylidene fluoride) (PVDF) generated by depositing magnetic iron oxide (Fe3O4) nanoparticles on the surface of barium titanate (BT) to fabricate BT-Fe3O4/PVDF composites. This process introduced an external magnetic field and the influences of external magnetic field on dielectric properties of composites were investigated systematically. The composites subjected to magnetic field treatment for 30 min at 60 °C exhibited the largest dielectric permittivity (385 at 100 Hz) when the BT-Fe3O4 concentration is approximately 33 vol.%. The BT-Fe3O4 suppressed the formation of a conducting path in the composite and induced low dielectric loss (0.3) and low conductivity (4.12 × 10(-9) S/cm) in the composite. Series-parallel model suggested that the enhanced dielectric permittivity of BT-Fe3O4/PVDF composites should arise from the ultrahigh permittivity of BT-Fe3O4 hybrid particles. However, the experimental results of the BT-Fe3O4/PVDF composites treated by magnetic field agree with percolation theory, which indicates that the enhanced dielectric properties of the BT-Fe3O4/PVDF composites originate from the interfacial polarization induced by the external magnetic field. This work provides a simple and effective way for preparing nanocomposites with enhanced dielectric properties for use in the electronics industry.

  20. Long-Term Isothermal Aging Effects on Carbon Fabric-Reinforced PMR-15 Composites: Compression Strength

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.; Roberts, Gary D.; Kamvouris, John E.

    1996-01-01

    A study was conducted to determine the effects of long-term isothermal thermo-oxidative aging on the compressive properties of T-650-35 fabric reinforced PMR-15 composites. The temperatures that were studied were 204, 260, 288, 316, and 343 C. Specimens of different geometries were evaluated. Cut edge-to-surface ratios of 0.03 to 0.89 were fabricated and aged. Aging times extended to a period in excess of 15,000 hours for the lower temperature runs. The unaged and aged specimens were tested in compression in accordance with ASTM D-695. Both thin and thick (plasma) specimens were tested. Three specimens were tested at each time/temperature/geometry condition. The failure modes appeared to be initiated by fiber kinking with longitudinal, interlaminar splitting. In general, it appears that the thermo-oxidative degradation of the compression strength of the composite material may occur by both thermal (time-dependent) and oxidative (weight-loss) mechanisms. Both mechanisms appear to be specimen-thickness dependent.

  1. Hybrid composite membranes based on polyethylene separator and Al2O3 nanoparticles for lithium-ion batteries.

    PubMed

    Shin, Won-Kyung; Lee, Yoon-Sung; Kim, Dong-Won

    2013-05-01

    A hybrid composite membrane is prepared by coating nano-sized Al2O3 powder (13 and 50 nm) and poly(vinylidene fluoride-co-hexafluoropropene) (P(VdF-co-HFP)) binder on both sides of polyethylene separator. The composite membrane shows better thermal stability and improved wettability for organic liquid electrolyte than polyethylene separator, due to the presence of heat-resistant Al2O3 particles with high-surface area in the coating layer. By using the composite membrane, the lithium-ion cells composed of carbon anode and LiNi1/3Co1/3Mn1/3O2 cathode are assembled and their cycling performances are evaluated. The cells assembled with the composite membranes are proven to have better capacity retention than the cell prepared with polyethylene separator, due to the enhanced ability to retain the electrolyte solution in the cell. The cell assembled with the composite membrane containing 13 nm-sized Al2O3 particles has an initial discharge capacity of 173.2 mA h g(-1) with good capacity retention. PMID:23858932

  2. Structure Design of the 3-D Braided Composite Based on a Hybrid Optimization Algorithm

    NASA Astrophysics Data System (ADS)

    Zhang, Ke

    Three-dimensional braided composite has the better designable characteristic. Whereas wide application of hollow-rectangular-section three-dimensional braided composite in engineering, optimization design of the three-dimensional braided composite made by 4-step method were introduced. Firstly, the stiffness and damping characteristic analysis of the composite is presented. Then, the mathematical models for structure design of the three-dimensional braided composite were established. The objective functions are based on the specific damping capacity and stiffness of the composite. The design variables are the braiding parameters of the composites and sectional geometrical size of the composite. The optimization problem is solved by using ant colony optimization (ACO), contenting the determinate restriction. The results of numeral examples show that the better damping and stiffness characteristic could be obtained. The method proposed here is useful for the structure design of the kind of member and its engineering application.

  3. Elevation of oxidative-damage biomarkers during aging in F2 hybrid mice: protection by chronic oral intake of resveratrol.

    PubMed

    Wong, Yee Ting; Gruber, Jan; Jenner, Andrew M; Ng, Mary Pei-Ern; Ruan, Runsheng; Tay, Francis Eng Hock

    2009-03-15

    Resveratrol (RSV), a naturally occurring phytoalexin that can be found in red wine, berries, and peanuts, has been shown to extend both mean and maximum life span in model organisms. RSV has also been reported to shift the physiology of middle-aged mice on a high-calorie diet toward that of mice on a standard diet. These beneficial effects of RSV have been suggested to resemble caloric restriction. Our study in F2 four-way cross-hybrid mice was the first to evaluate the effects of aging and long-term RSV treatment (14.09+/-3.4 mg/L in drinking water for 6 or 12 months) on biomarkers of oxidative damage to DNA, 8-hydroxy-2'-deoxyguanosine (8OHdG); lipid, 8-iso-prostaglandin(2 alpha) (8-iso-PGF(2 alpha)); and protein, protein carbonyl content (PCC). There was a significant age-dependent accumulation of oxidative damage to DNA, lipid, and protein as well as a clear increase in urine 8-iso-PGF(2 alpha) levels in the majority of mouse tissues. Rates of age-dependent increases in damage biomarkers varied between tissues. Chronic RSV treatment elevated total RSV plasma levels and reduced the observed age-dependent accumulation of (1) 8OHdG in liver and heart, (2) 8-iso-PGF(2 alpha) in heart and urine, and (3) PCC in liver and kidney. However, a 12-month RSV intake resulted in significant elevation of 8-iso-PGF(2 alpha) and PCC in kidney. Our studies demonstrate that RSV treatment consistently attenuated oxidative damage in tissues where age-related oxidative damage accumulation was prominent, but also suggested that chronic RSV treatment may induce nephrotoxicity.

  4. Compositional dynamics of the human intestinal microbiota with aging: implications for health.

    PubMed

    Lakshminarayanan, B; Stanton, C; O'Toole, P W; Ross, R P

    2014-11-01

    The human gut contains trillions of microbes which form an essential part of the complex ecosystem of the host. This microbiota is relatively stable throughout adult life, but may fluctuate over time with aging and disease. The gut microbiota serves a number of functions including roles in energy provision, nutrition and also in the maintenance of host health such as protection against pathogens. This review summarizes the age-related changes in the microbiota of the gastrointestinal tract (GIT) and the link between the gut microbiota in health and disease. Understanding the composition and function of the gut microbiota along with the changes it undergoes overtime should aid the design of novel therapeutic strategies to counteract such alterations. These strategies include probiotic and prebiotic preparations as well as targeted nutrients, designed to enrich the gut microbiota of the aging population.

  5. Colour stability, opacity and cross-link density of composites submitted to accelerated artificial aging.

    PubMed

    Mundim, Fabrício Mariano; Pires-de-Souza, Fernanda de Carvalho Panzeri; Garcia, Lucas da Fonseca Roberti; Consani, Simonides

    2010-06-01

    The study evaluated the influence of accelerated artificial aging on colour stability, opacity and cross-link density of resin-based composites (RBCs). Seven specimens were obtained of five RBCs (Heliomolar, 4 Seasons, Tetric Evo Ceram, SR Adoro), which were submitted to colour stability and opacity analysis and cross-link density evaluation. All tests were performed before and after aging. After statistical analysis (one-way ANOVA; Tukey; p<0.05), it was observed that QuiXfil and SR Adoro presented colour alteration values above those that are clinically acceptable (deltaE=5.77 and 4.34 respectively) and the variation in opacity was lowest for SR Adoro. There was an increase in the cross-link density of all studied materials after aging.

  6. Aging processes in precipitation-hardening composite materials based on a D16 aluminum alloy

    NASA Astrophysics Data System (ADS)

    Chernyshova, T. A.; Kobeleva, L. I.

    2010-09-01

    Aging of composite materials (CMs) based on an aluminum D16 alloy and reinforced by Al3Ti intermetallic inclusions (0-10 vol %) having formed upon an in situ reaction and by SiC particles (0-30 vol %) ≤3 or 28 μm in size is studied. Oxide ceramic nanoparticles (0.1 wt %) are used to modify the structure of the CMs. The structures of the CMs before and after aging are analyzed by optical microscopy and scanning electron microscopy on a microscope equipped with an X-ray energy dispersive spectrometer. The hardness of the CMs is measured. The overall hardening of aged CMs is shown to result from a competition between the hardening effects induced by the formation of Guinier-Preston zones and the precipitation of the high-temperature θ and S phases. These effects are controlled by the dislocation density in the matrix.

  7. Myosin heavy chain composition in the rat diaphragm - Effect of age and exercise training

    NASA Technical Reports Server (NTRS)

    Gosselin, Luc E.; Betlach, Michael; Vailas, Arthur C.; Greaser, Marion L.; Thomas, D. P.

    1992-01-01

    The effects of aging and exercise training on the myosin heavy chain (MHC) composition were determined in both the costal and crural diaphragm regions of female Fischer 344 rats. Treadmill running at 75 percent maximal oxygen consumption resulted in similar increases in plantaris muscle citrate synthase activity in both young (5 mo) and old (23mo) trained animals (P less than 0.05). It was found that the ratio of fast to slow MHC was significantly higher (P less than 0.005) in the crural compared with costal diaphragm region in both age groups. A significant age-related increase in persentage of slow MHC was observed in both diaphragm regions. The relative proportion of slow MHC in either costal or crural region was not changed by exercise training.

  8. Investigation of aging mechanisms of high power Li-ion cells used for hybrid electric vehicles

    NASA Astrophysics Data System (ADS)

    Bourlot, Sandrine; Blanchard, Philippe; Robert, Stéphanie

    High power lithium-ion batteries need to exhibit long service life to meet targets of automotive applications. This article describes the deep investigation of the so-called VL6P cells, high power lithium-ion cells mass produced by Johnson Controls - Saft (JC-S), in order to understand the root causes of their aging. Cells aged by calendar and cycle life are investigated here compared to fresh cells. Among the results of the different analyses, the most significant is that more active lithium is detected in negative electrode after aging. This tends to indicate that effect of aging is due to increase of positive electrode limitation. Results of this investigation will allow JC-S to continue to improve life of the lithium-ion cells.

  9. Composites Associated with Pulp-Protection Material: Color-Stability Analysis after Accelerated Artificial Aging

    PubMed Central

    Cruvinel, Diogo Rodrigues; Garcia, Lucas da Fonseca Roberti; Consani, Simonides; de Carvalho Panzeri Pires-de-Souza, Fernanda

    2010-01-01

    Objectives: This study assessed the color stability of two composites associated with two pulp protectors submitted to accelerated artificial aging (AAA). Methods: 60 test specimens were made with 0.5 mm of protection material (calcium hydroxide - CH or glass ionomer cement - GIC) and 2.5 mm of restoration material (Concept or QuixFil) and divided into 3 groups (n=10) according to the type of protection material/composite, and the control group (no protection). After polishing, color readings were obtained with a spectrophotometer (PCB 6807 Byk Gardner) before and after AAA for 384 hours, and L*, a*, and b* coordinates and total color variation (ΔE) were analyzed (2-way ANOVA, Bonferroni, α=05). Results: Composites placed on CH presented lower L* levels than those on GIC, which presented higher L* values than the control group and lower b* values than those of the CH group. The Concept composite presented higher ΔE levels for all groups, differing statistically from QuixFil, except when placed on GIC. Conclusions: It was concluded that the protection material could affect the color stability and AAA is a factor that enhances this effect, depending on the type of composite used. PMID:20046473

  10. Color and opacity of composites protected with surface sealants and submitted to artificial accelerated aging

    PubMed Central

    Aguilar, Fabiano Gamero; Roberti Garcia, Lucas da Fonseca; Cruvinel, Diogo Rodrigues; Sousa, Ana Beatriz Silva; de Carvalho Panzeri Pires-de-Souza, Fernanda

    2012-01-01

    Objectives: To evaluate the color similarity, stability and opacity of composites (TPH, Charisma, and Concept, shade A2) protected with surface sealants (Fortify Plus and Biscover) and cyanoacrylate (Super Bonder). Methods: Forty specimens of each composite were made and separated into 4 groups (n=10) according to the surface protection: GI - without sealant; GII - cyanoacrylate; GIII - Fortify Plus; GIV - Biscover. Color and opacity readings were taken before and after Artificial Acelerated Aging (AAA) and the values obtained for color stability were submitted to statistical analysis by 2-way ANOVA and Bonferroni’s test (P<.05). The values acquired for color similarity were submitted to 1-way ANOVA and Tukey’s test (P<.05). The specimen sufaces were compared before and after AAA using Scanning Electronic Microscopy (SEM). Results: Studied composites did not present the same values for the coordinates L*, a* and b * before AAA, indicating that there was no color similarity among them. All composites presented color alteration after AAA with clinically unacceptable values. Protected groups presented lower opacity variation after AAA, in comparison with the control goup. SEM evaluation demonstrated that AAA increased the surface irregularities in all of the studied groups. Conclusion: Surface sealants were not effective in maintaining composite color, but were able to maintain opacity. PMID:22229004

  11. Age, education, and earnings in the course of Brazilian development: does composition matter?

    PubMed Central

    de Lima Amaral, Ernesto Friedrich; Potter, Joseph E.; Hamermesh, Daniel S.; Rios-Neto, Eduardo Luiz Goncalves

    2015-01-01

    BACKGROUND The impacts of shifts in the age distribution of the working-age population have been studied in relation to the effect of the baby boom generation on the earnings of different cohorts in the U.S. However, this topic has received little attention in the context of the countries of Asia and Latin America, which are now experiencing substantial shifts in their age-education distributions. OBJECTIVE In this analysis, we estimate the impact of the changing relative size of the adult male population, classified by age and education groups, on the earnings of employed men living in 502 Brazilian local labor markets during four time periods between 1970 and 2000. METHODS Taking advantage of the huge variation across Brazilian local labor markets and demographic census micro-data, we used fixed effects models to demonstrate that age education group size depresses earnings. RESULTS These effects are more detrimental among age-education groups with higher education, but they are becoming less negative over time. The decrease in the share of workers with the lowest level of education has not led to gains in the earnings of these workers in recent years. CONCLUSIONS These trends might be a consequence of technological shifts and increasing demand for labor with either education or experience. Compositional shifts are influential, which suggests that this approach could prove useful in studying this central problem in economic development. PMID:26146484

  12. Structure and composition of arytenoid cartilage of the bullfrog (Lithobates catesbeianus) during maturation and aging.

    PubMed

    Laureano, Priscila Eliane dos Santos; Oliveira, Kris Daiana Silva; de Aro, Andrea Aparecida; Gomes, Laurecir; Pimentel, Edson Rosa; Esquisatto, Marcelo Augusto Marretto

    2015-10-01

    The aging process induces progressive and irreversible changes in the structural and functional organization of animals. The objective of this study was to evaluate the effects of aging on the structure and composition of the extracellular matrix of the arytenoid cartilage found in the larynx of male bullfrogs (Lithobates catesbeianus) kept in captivity for commercial purposes. Animals at 7, 180 and 1080 days post-metamorphosis (n=10/age) were euthanized and the cartilage was removed and processed for structural and biochemical analysis. For the structural analyses, cartilage sections were stained with picrosirius, toluidine blue, Weigert's resorcin-fuchsin and Von Kossa stain. The sections were also submitted to immunohistochemistry for detection of collagen types I and II. Other samples were processed for the ultrastructural and cytochemical analysis of proteoglycans. Histological sections were used to chondrocyte count. The number of positive stainings for proteoglycans was quantified by ultrastructural analysis. For quantification and analysis of glycosaminoglycans were used the dimethyl methylene blue and agarose gel electrophoresis methods. The chloramine T method was used for hydroxyproline quantification. At 7 days, basophilia was observed in the pericellular and territorial matrix, which decreased in the latter over the period studied. Collagen fibers were arranged perpendicular to the major axis of the cartilaginous plate and were thicker in older animals. Few calcification areas were observed at the periphery of the cartilage specimens in 1080-day-old animals. Type II collagen was present throughout the stroma at the different ages. Elastic fibers were found in the stroma and perichondrium and increased with age in the two regions. Proteoglycan staining significantly increased from 7 to 180 days and reduced at 1080 days. The amount of total glycosaminoglycans was higher in 180-day-old animals compared to the other ages, with marked presence of

  13. The Effects of Fiber Surface Modification and Thermal Aging on Composite Toughness and Its Measurement

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.; Madhukar, Madhu; Papadopolous, Demetrios S.; Inghram, Linda; Mccorkle, Linda

    1995-01-01

    A detailed experimental study was conducted to establish the structure-property relationships between elevated temperature aging and fiber-matrix bonding, Mode 2 interlaminar fracture toughness, and failure modes of carbon fiber/PMR-15 composites. The fiber-matrix adhesion was varied by using carbon fibers with different surface treatments. Short beam shear tests were used to quantify the interfacial shear strength afforded by the use of the different fiber surface treatments. The results of the short beam shear tests showed that, for times up to 1000 hr, the aging process caused no changes in the bulk of the three composite materials that would degrade the shear properties of the material. Comparisons between the interlaminar shear strengths (ILSS) measured by the short beam shear tests and the GIIC test results, as measured by the ENF test, indicated that the differences in the surface treatments significantly affected the fracture properties while the effect of the aging process was probably limited to changes at the starter crack tip. The fracture properties changed due to a shift in the fracture from an interfacial failure to a failure within the matrix when the fiber was changed from AU-4 to AS-4 or AS-4G. There appears to be an effect of the fiber/matrix bonding on the thermo-oxidative stability of the composites that were tested. The low bonding afforded by the AU 1 fiber resulted in weight losses about twice those experienced by the AS 1 reinforced composites, the ones with the best TOS.

  14. Synthesis and properties of poly(methyl methacrylate-2-acrylamido-2-methylpropane sulfonic acid)/PbS hybrid composite

    SciTech Connect

    Preda, N.; Rusen, E.; Musuc, A.; Enculescu, M.; Matei, E.; Marculescu, B.; Fruth, V.; Enculescu, I.

    2010-08-15

    The synthesis of a new hybrid composite based on PbS nanoparticles and poly(methyl methacrylate-2-acrylamido-2-methylpropane sulfonic acid) [P(MMA-AMPSA)] copolymer is reported. The chemical synthesis consists in two steps: (i) a surfactant-free emulsion copolymerization between methyl methacrylate and 2-acrylamido-2-methylpropane sulfonic acid and (ii) the generation of PbS particles in the presence of the P(MMA-AMPSA) latex, from the reaction between lead nitrate and thiourea. The composite was studied by scanning electron microscopy (SEM), X-ray diffraction, FTIR spectroscopy, thermogravimetric analysis and differential scanning calorimetry. The microstructure observed using SEM proves that the PbS nanoparticles are well dispersed in the copolymer matrix. The X-ray diffraction measurements demonstrate that the PbS nanoparticles have a cubic rock salt structure. It was also found that the inorganic semiconductor nanoparticles improve the thermal stability of the copolymer matrix.

  15. Energy Spectrum and Composition of Ultra High Energy Cosmic Ray Showers Using Hybrid Analysis from Telescope Array

    NASA Astrophysics Data System (ADS)

    Jui, Charles; Allen, Monica; Abu-Zayyad, Tareq; Stokes, Benjamin; Ivanov, Dmitri

    2013-04-01

    The Telescope Array (TA) consists of 38 fluorescence telescopes spread over three detector sites. The three sites at located the periphery of a surface array of 507 scintillation counters, covering 700 square km, with a spacing of 1.2 km. TA is designed to study the energy spectrum, composition, and arrival direction anisotropy of ultrahigh energy cosmic rays (UHECR). A unique feature of TA is that one of three fluorescence detector (FD) sites, Middle Drum (MD), is instrumented with 14 refurbished telescopes from the High Resolution Fly's Eye (HiRes) experiment. This commonality provides TA with a direct link back to the HiRes experiment and data. Using the scintillator detector data in conjunction with the MD data improves the geometrical reconstruction and hence provides a more accurate reconstruction of the energy of the primary particle and shower profile. The Middle Drum hybrid spectrum composition results will be presented.

  16. Reduced leakage current and improved ferroelectricity in magneto-electric composite ceramics prepared with microwave assisted radiant hybrid sintering

    SciTech Connect

    Upadhyay, Sanjay Kumar; Reddy, V. Raghavendra E-mail: vrreddy.ugcdaecsr@nic.in; Gupta, S. M.; Chauhan, N.; Gupta, Ajay

    2015-04-15

    Structural, electrical and magnetic properties of magneto-electric composite ceramics viz., 0.9 BaTi{sub 0.95}Sn{sub 0.05}O{sub 3} (BTSO)- 0.1 Ni{sub 0.8}Zn{sub 0.2}Fe{sub 2}O{sub 4} (NZFO) prepared with microwave assisted radiant hybrid sintering (MARH) are reported. Phase purity and isovalent substitution of Ti{sup 4+} by Sn{sup 4+} of the samples is confirmed from x-ray diffraction and {sup 119}Sn Mossbauer measurements respectively. Significant suppression of leakage current and improvement of ferroelectricity is observed for the composites prepared with MARH. The observed results are explained in terms of uniform dispersion of ferrite (NZFO) phase in the ferroelectric (BTSO) matrix as evidenced from back-scattered scanning electron micrographs.

  17. Novel Hybrid Ablative/Ceramic Layered Composite for Earth Re-entry Thermal Protection: Microstructural and Mechanical Performance

    NASA Astrophysics Data System (ADS)

    Triantou, K.; Mergia, K.; Marinou, A.; Vekinis, G.; Barcena, J.; Florez, S.; Perez, B.; Pinaud, G.; Bouilly, J.-M.; Fischer, W. P. P.

    2015-04-01

    In view of spacecraft re-entry applications into planetary atmospheres, hybrid thermal protection systems based on layered composites of ablative materials and ceramic matrix composites are investigated. Joints of ASTERM™ lightweight ablative material with Cf/SiC (SICARBON™) were fabricated using commercial high temperature inorganic adhesives. Sound joints without defects are produced and very good bonding of the adhesive with both base materials is observed. Mechanical shear tests under ambient conditions and in liquid nitrogen show that mechanical failure always takes place inside the ablative material with no decohesion of the interface of the adhesive layer with the bonded materials. Surface treatment of the ablative surface prior to bonding enhances both the shear strength and the ultimate shear strain by up to about 60%.

  18. Reduced leakage current and improved ferroelectricity in magneto-electric composite ceramics prepared with microwave assisted radiant hybrid sintering

    NASA Astrophysics Data System (ADS)

    Upadhyay, Sanjay Kumar; Reddy, V. Raghavendra; Gupta, S. M.; Chauhan, N.; Gupta, Ajay

    2015-04-01

    Structural, electrical and magnetic properties of magneto-electric composite ceramics viz., 0.9 BaTi0.95Sn0.05O3 (BTSO)- 0.1 Ni0.8Zn0.2Fe2O4 (NZFO) prepared with microwave assisted radiant hybrid sintering (MARH) are reported. Phase purity and isovalent substitution of Ti4+ by Sn4+ of the samples is confirmed from x-ray diffraction and 119Sn Mossbauer measurements respectively. Significant suppression of leakage current and improvement of ferroelectricity is observed for the composites prepared with MARH. The observed results are explained in terms of uniform dispersion of ferrite (NZFO) phase in the ferroelectric (BTSO) matrix as evidenced from back-scattered scanning electron micrographs.

  19. Hybrid α-Fe2O3@Ni(OH)2 nanosheet composite for high-rate-performance supercapacitor electrode.

    PubMed

    Jiang, Hong; Ma, Haifeng; Jin, Ying; Wang, Lanfang; Gao, Feng; Lu, Qingyi

    2016-01-01

    In this study, we report a facile fabrication of ultrathin two-dimensional (2D) nanosheet hybrid composite, α-Fe2O3 nanosheet@Ni(OH)2 nanosheet, by a two-step hydrothermal method to achieve high specific capacitance and good stability performance at high charging/discharging rates when serving as electrode material of supercapacitors. The α-Fe2O3@Ni(OH)2 hybrid electrode not only has a smooth decrease of the specific capacitance with increasing current density, compared with the sharp decline of single component of Ni(OH)2 electrode, but also presents excellent rate capability with a specific capacitance of 356 F/g at a current density of 16 A/g and excellent cycling stability (a capacity retention of 93.3% after 500 cycles), which are superior to the performances of Ni(OH)2 with a lower specific capacitance of 132 F/g and a lower capacity retention of 81.8% at 16 A/g. The results indicate such hybrid structure would be promising as excellent electrode material for good performances at high current densities in the future. PMID:27553663

  20. Hybrid α-Fe2O3@Ni(OH)2 nanosheet composite for high-rate-performance supercapacitor electrode

    PubMed Central

    Jiang, Hong; Ma, Haifeng; Jin, Ying; Wang, Lanfang; Gao, Feng; Lu, Qingyi

    2016-01-01

    In this study, we report a facile fabrication of ultrathin two-dimensional (2D) nanosheet hybrid composite, α-Fe2O3 nanosheet@Ni(OH)2 nanosheet, by a two-step hydrothermal method to achieve high specific capacitance and good stability performance at high charging/discharging rates when serving as electrode material of supercapacitors. The α-Fe2O3@Ni(OH)2 hybrid electrode not only has a smooth decrease of the specific capacitance with increasing current density, compared with the sharp decline of single component of Ni(OH)2 electrode, but also presents excellent rate capability with a specific capacitance of 356 F/g at a current density of 16 A/g and excellent cycling stability (a capacity retention of 93.3% after 500 cycles), which are superior to the performances of Ni(OH)2 with a lower specific capacitance of 132 F/g and a lower capacity retention of 81.8% at 16 A/g. The results indicate such hybrid structure would be promising as excellent electrode material for good performances at high current densities in the future. PMID:27553663

  1. Hybrid α-Fe2O3@Ni(OH)2 nanosheet composite for high-rate-performance supercapacitor electrode

    NASA Astrophysics Data System (ADS)

    Jiang, Hong; Ma, Haifeng; Jin, Ying; Wang, Lanfang; Gao, Feng; Lu, Qingyi

    2016-08-01

    In this study, we report a facile fabrication of ultrathin two-dimensional (2D) nanosheet hybrid composite, α-Fe2O3 nanosheet@Ni(OH)2 nanosheet, by a two-step hydrothermal method to achieve high specific capacitance and good stability performance at high charging/discharging rates when serving as electrode material of supercapacitors. The α-Fe2O3@Ni(OH)2 hybrid electrode not only has a smooth decrease of the specific capacitance with increasing current density, compared with the sharp decline of single component of Ni(OH)2 electrode, but also presents excellent rate capability with a specific capacitance of 356 F/g at a current density of 16 A/g and excellent cycling stability (a capacity retention of 93.3% after 500 cycles), which are superior to the performances of Ni(OH)2 with a lower specific capacitance of 132 F/g and a lower capacity retention of 81.8% at 16 A/g. The results indicate such hybrid structure would be promising as excellent electrode material for good performances at high current densities in the future.

  2. Preparation and Evaluation of Hybrid Composites of Chemical Fuel and Multi-walled Carbon Nanotubes in the Study of Thermopower Waves.

    PubMed

    Hwang, Hayoung; Yeo, Taehan; Cho, Yonghwan; Shin, Dongjoon; Choi, Wonjoon

    2015-01-01

    When a chemical fuel at a certain position in a hybrid composite of the fuel and a micro/nanostructured material is ignited, chemical combustion occurs along the interface between the fuel and core materials. Simultaneously, dynamic changes in thermal and chemical potentials across the micro/nanostructured materials result in concomitant electrical energy generation induced by charge transfer in the form of a high-output voltage pulse. We demonstrate the entire procedure of a thermopower wave experiment, from synthesis to evaluation. Thermal chemical vapor deposition and the wet impregnation process are respectively employed for the synthesis of a multi-walled carbon nanotube array and a hybrid composite of picric acid/sodium azide/multi-walled carbon nanotubes. The prepared hybrid composites are used to fabricate a thermopower wave generator with connecting electrodes. The combustion of the hybrid composite is initiated by laser heating or Joule-heating, and the corresponding combustion propagation, direct electrical energy generation, and real-time temperature changes are measured using a high-speed microscopy system, an oscilloscope, and an optical pyrometer, respectively. Furthermore, the crucial strategies to be adopted in the synthesis of hybrid composite and initiation of their combustion that enhance the overall thermopower wave energy transfer are proposed. PMID:25938793

  3. Alpha Trianguli Australis (K2 II-III) - Hybrid or composite?

    NASA Technical Reports Server (NTRS)

    Ayres, T. R.

    1985-01-01

    The prototype hybrid-spectrum giant Alpha Trianguli Australis exhibits a far-ultraviolet continuum which is considerably bluer than would be expected of a star of its optical colors, suggesting the presence of a previously unrecognized companion. If the K-type primary is as luminous as indicated by the widths of its Ca II and H-alpha lines, the companion could be an early F-type dwarf that only recently has arrived on the main sequence. Indeed, the flux of C IV from Alpha TrA - an important measure of hybridness - would not be inconsistent with that expected from a very young chromospherically active F star.

  4. Compositional differences between near-isogenic GM and conventional maize hybrids are associated with backcrossing practices in conventional breeding.

    PubMed

    Venkatesh, Tyamagondlu V; Cook, Kevin; Liu, Bing; Perez, Timothy; Willse, Alan; Tichich, Ryan; Feng, Ping; Harrigan, George G

    2015-02-01

    Here, we show that differences between genetically modified (GM) and non-GM comparators cannot be attributed unequivocally to the GM trait, but arise because of minor genomic differences in near-isogenic lines. Specifically, this study contrasted the effect of three GM traits (drought tolerance, MON 87460; herbicide resistance, NK603; insect protection, MON 89034) on maize grain composition relative to the effects of residual genetic variation from backcrossing. Important features of the study included (i) marker-assisted backcrossing to generate genetically similar inbred variants for each GM line, (ii) high-resolution genotyping to evaluate the genetic similarity of GM lines to the corresponding recurrent parents and (iii) introgression of the different GM traits separately into a wide range of genetically distinct conventional inbred lines. The F1 hybrids of all lines were grown concurrently at three replicated field sites in the United States during the 2012 growing season, and harvested grain was subjected to compositional analysis. Proximates (protein, starch and oil), amino acids, fatty acids, tocopherols and minerals were measured. The number of statistically significant differences (α = 0.05), as well as magnitudes of difference, in mean levels of these components between corresponding GM variants was essentially identical to that between GM and non-GM controls. The largest sources of compositional variation were the genetic background of the different conventional inbred lines (males and females) used to generate the maize hybrids and location. The lack of any compositional effect attributable to GM suggests the development of modern agricultural biotechnology has been accompanied by a lack of any safety or nutritional concerns.

  5. Mechanism of high dielectric performance of polymer composites induced by BaTiO3-supporting Ag hybrid fillers

    NASA Astrophysics Data System (ADS)

    Fang, Fang; Yang, Wenhu; Yu, Shuhui; Luo, Suibin; Sun, Rong

    2014-03-01

    BaTiO3-supporting Ag hybrid particles (BT-Ag) with varied fraction of Ag were synthesized by reducing silver nitrate in the glycol solution containing BaTiO3 (BT) suspensions. The Ag nano particles with a size of about 20 nm were discretely grown on the surface of the BT. The dielectric performance of the composites containing the BT-Ag as fillers in the matrix of polyvinylidene fluoride (PVDF) was investigated. The relative permittivity (ɛr) of the BT-Ag/PVDF composites increased prominently with the increase of BT-Ag loading amount, and the typical conductive path of the conductor/polymer system was not observed even with a high loading of BT-Ag. The ɛr at 100 Hz for the three BT-(0.31, 0.49, 0.61)Ag/PVDF composites at room temperature were 283, 350, and 783, respectively. The ɛr of the composites was enhanced by more than 3 times compared with that of the composite containing untreated BT nanoparticles at frequencies over 1 kHz and the loss tangent (tan δ) was less than 0.1 which should be attributed to the low conductivity of the composites. Theoretical calculations based on the effective medium percolation theory model and series-parallel model suggested that the enhanced permittivity of BT-Ag/PVDF composites should arise from the ultrahigh permittivity of BT-Ag fillers, which was over 104 and associated with the content of Ag deposited on the surface of BT.

  6. Quantifying the aging response and nutrient composition for muscles of the beef round.

    PubMed

    Dixon, C L; Woerner, D R; Tokach, R J; Chapman, P L; Engle, T E; Tatum, J D; Belk, K E

    2012-03-01

    The objective of this study was to determine the optimal postmortem aging period and nutrient composition for Beef Value Cuts of the round. Forty USDA Select and 40 Premium USDA Choice beef carcasses were selected from a commercial beef packing plant in Colorado over a 12-wk period. The bottom and inside rounds were collected from both sides of each carcass for further fabrication into the following muscles: adductor, gastrocnemius, gracilis, pectineus, and superficial digital flexor. Each pair of muscles was cut into 7 steaks and randomly assigned to 1 of the following aging periods: 2, 4, 6, 10, 14, 21, and 28 d, and placed in refrigerated storage (2°C, never frozen). Upon completion of the designated aging period, steaks were removed from storage, cooked to a peak internal temperature of 72°C, and evaluated using Warner-Bratzler shear force (WBSF). A 2-way interaction was detected (P < 0.05) between individual muscle and postmortem aging period. The WBSF of all muscles except the superficial digital flexor decreased with increased time of postmortem aging. Quality grade did not affect (P > 0.05) WBSF values for the adductor, gastrocnemius, pectineus, and superficial digital flexor muscles. Exponential decay models were used to predict the change in WBSF from 2 to 28 d postmortem (aging response). The adductor, gastrocnemius, Select gracilis, Premium Choice gracilis, and pectineus required 21, 14, 23, 23, and 25 d, respectively, to complete the majority of the aging response. To determine the nutrient composition of the adductor, gastrocnemius, gracilis, pectineus, semimembranosus, and superficial digital flexor, bottom and inside rounds were collected from 10 USDA Select and 10 Premium USDA Choice carcasses and fabricated into the respective muscles, cut into 2.54-cm cubes, frozen (-20°C), and then homogenized. The adductor, gracilis, pectineus, semimembranosus, and superficial digital flexor were analyzed for DM, moisture, CP, and ash percentages. All

  7. Quantifying the aging response and nutrient composition for muscles of the beef round.

    PubMed

    Dixon, C L; Woerner, D R; Tokach, R J; Chapman, P L; Engle, T E; Tatum, J D; Belk, K E

    2012-03-01

    The objective of this study was to determine the optimal postmortem aging period and nutrient composition for Beef Value Cuts of the round. Forty USDA Select and 40 Premium USDA Choice beef carcasses were selected from a commercial beef packing plant in Colorado over a 12-wk period. The bottom and inside rounds were collected from both sides of each carcass for further fabrication into the following muscles: adductor, gastrocnemius, gracilis, pectineus, and superficial digital flexor. Each pair of muscles was cut into 7 steaks and randomly assigned to 1 of the following aging periods: 2, 4, 6, 10, 14, 21, and 28 d, and placed in refrigerated storage (2°C, never frozen). Upon completion of the designated aging period, steaks were removed from storage, cooked to a peak internal temperature of 72°C, and evaluated using Warner-Bratzler shear force (WBSF). A 2-way interaction was detected (P < 0.05) between individual muscle and postmortem aging period. The WBSF of all muscles except the superficial digital flexor decreased with increased time of postmortem aging. Quality grade did not affect (P > 0.05) WBSF values for the adductor, gastrocnemius, pectineus, and superficial digital flexor muscles. Exponential decay models were used to predict the change in WBSF from 2 to 28 d postmortem (aging response). The adductor, gastrocnemius, Select gracilis, Premium Choice gracilis, and pectineus required 21, 14, 23, 23, and 25 d, respectively, to complete the majority of the aging response. To determine the nutrient composition of the adductor, gastrocnemius, gracilis, pectineus, semimembranosus, and superficial digital flexor, bottom and inside rounds were collected from 10 USDA Select and 10 Premium USDA Choice carcasses and fabricated into the respective muscles, cut into 2.54-cm cubes, frozen (-20°C), and then homogenized. The adductor, gracilis, pectineus, semimembranosus, and superficial digital flexor were analyzed for DM, moisture, CP, and ash percentages. All

  8. Fingermark initial composition and aging using Fourier transform infrared microscopy (μ-FTIR).

    PubMed

    Girod, Aline; Xiao, Linda; Reedy, Brian; Roux, Claude; Weyermann, Céline

    2015-09-01

    This study investigated fingermark residues using Fourier transform infrared microscopy (μ-FTIR) in order to obtain fundamental information about the marks' initial composition and aging kinetics. This knowledge would be an asset for fundamental research on fingermarks, such as for dating purposes. Attenuated total reflection (ATR) and single-point reflection modes were tested on fresh fingermarks. ATR proved to be better suited and this mode was subsequently selected for further aging studies. Eccrine and sebaceous material was found in fresh and aged fingermarks and the spectral regions 1000-1850cm(-1) and 2700-3600cm(-1) were identified as the most informative. The impact of substrates (aluminium and glass slides) and storage conditions (storage in the light and in the dark) on fingermark aging was also studied. Chemometric analyses showed that fingermarks could be grouped according to their age regardless of the substrate when they were stored in an open box kept in an air-conditioned laboratory at around 20°C next to a window. On the contrary, when fingermarks were stored in the dark, only specimens deposited on the same substrate could be grouped by age. Thus, the substrate appeared to influence aging of fingermarks in the dark. Furthermore, PLS regression analyses were conducted in order to study the possibility of modelling fingermark aging for potential fingermark dating applications. The resulting models showed an overall precision of ±3 days and clearly demonstrated their capability to differentiate older fingermarks (20 and 34 days old) from newer ones (1, 3, 7 and 9 days old) regardless of the substrate and lighting conditions. These results are promising from a fingermark dating perspective. Further research is required to fully validate such models and assess their robustness and limitations in uncontrolled casework conditions. PMID:26254626

  9. One-year water-ageing of calcium phosphate composite containing nano-silver and quaternary ammonium to inhibit biofilms.

    PubMed

    Cheng, Lei; Zhang, Ke; Zhou, Chen-Chen; Weir, Michael D; Zhou, Xue-Dong; Xu, Hockin H K

    2016-09-29

    Dental composites are commonly used restorative materials; however, secondary caries due to biofilm acids remains a major problem. The objectives of this study were (1) to develop a composite containing quaternary ammonium dimethacrylate (QADM), nanoparticles of silver (NAg), and nanoparticles of amorphous calcium phosphate (NACP), and (2) to conduct the first investigation of the mechanical properties, biofilm response and acid production vs water-ageing time from 1 day to 12 months. A 4 × 5 design was utilized, with four composites (NACP-QADM composite, NACP-NAg composite, NACP-QADM-NAg composite, and a commercial control composite), and five water-ageing time periods (1 day, and 3, 6, 9, and 12 months). After each water-ageing period, the mechanical properties of the resins were measured in a three-point flexure, and antibacterial properties were tested via a dental plaque biofilm model using human saliva as an inoculum. After 12 months of water-ageing, NACP-QADM-NAg had a flexural strength and elastic modulus matching those of the commercial control (P>0.1). Incorporation of QADM or NAg into the NACP composite greatly reduced biofilm viability, metabolic activity and acid production. A composite containing both QADM and NAg possessed a stronger antibacterial capability than one with QADM or NAg alone (P<0.05). The anti-biofilm activity was maintained after 12 months of water-ageing and showed no significant decrease with increasing time (P>0.1). In conclusion, the NACP-QADM-NAg composite decreased biofilm viability and lactic acid production, while matching the load-bearing capability of a commercial composite. There was no decrease in its antibacterial properties after 1 year of water-ageing. The durable antibacterial and mechanical properties indicate that NACP-QADM-NAg composites may be useful in dental restorations to combat caries.

  10. Comparison of corn silage hybrids for yield, nutrient composition, in vitro digestibility, and milk yield by dairy cows.

    PubMed

    Thomas, E D; Mandebvu, P; Ballard, C S; Sniffen, C J; Carter, M P; Beck, J

    2001-10-01

    A study was undertaken to compare Novartis N29-F1, a dual-purpose 90-d relative maturity corn hybrid, and Novartis NX3018, a 90-d relative maturity leafy corn silage hybrid for dry matter (DM) yield, in vitro digestibility, plant components, nutrient composition, and lactational performance by Holstein cows. The two corn hybrids were planted in replicated 15.2- x 321-m plots. Plant population and DM yield were similar between the two corn hybrids. Novartis NX3018 had higher content of crude protein and ash, a higher proportion of leaves and stalks, and a lower proportion of grain compared with Novartis N29-F1. The cob, grain, and leaves of Novartis NX3018 had higher in vitro true DM and neutral detergent fiber disappearances compared with the respective plant components of Novartis N29-F1. Thirty-eight midlactation multiparous Holstein cows (78 +/- 23.0 days in milk) producing 47.2 +/- 8.9 kg of milk per cow per day were blocked and assigned randomly to one of two total mixed ration (TMR) containing (DM basis) approximately 26% Novartis N29-F1 or Novartis NX3018 corn silage. Cows were housed in a free-stall barn and group fed ad libitum. The lactation study was conducted as a crossover design with two 28-d periods. Samples and data were collected during the final 7 d of each period. The total mixed rations were formulated using the Cornell-Penn-Miner Dairy nutrition model. Cows that were fed the total mixed rations containing Novartis NX3018 corn silage produced higher yields of milk 3.5% fat-corrected milk (FCM), milk crude protein, and milk lactose compared to cows that were fed the TMR containing Novartis N29-F1 corn silage. In conclusion, the Novartis NX3018 corn hybrid was leafier and more digestible in vitro, and when fed to dairy cows as silage, promoted higher milk yield compared with the Novartis N29-F1 corn hybrid.

  11. Hybrid composites made of multiwalled carbon nanotubes functionalized with Fe3O4 nanoparticles for tissue engineering applications

    NASA Astrophysics Data System (ADS)

    Cunha, C.; Panseri, S.; Iannazzo, D.; Piperno, A.; Pistone, A.; Fazio, M.; Russo, A.; Marcacci, M.; Galvagno, S.

    2012-11-01

    A straightforward technique for functionalization of multiwalled carbon nanotubes (MWCNTs) with magnetite (Fe3O4) nanoparticles was developed. Iron oxide nanoparticles were deposited on MWCNT surfaces by a deposition-precipitation method using Fe3+/Fe2+ salts precursors in basic solution. The characterizations by HRTEM, XRD, SEM/EDX, AAS and TPR analyses confirmed the successful formation of magnetic iron oxide nanoparticles on the MWCNT surface. Fe3O4/MWCNT hybrid composites were analysed in vitro by incubation with mesenchymal stem cells for 1, 3 and 7 days, either in the presence or absence of a static magnetic field. Analysis of cell proliferation was performed by the MTT assay, quantification of cellular stress was performed by the Lactate Dehydrogenase assay and analysis of cell morphology was performed by actin immunofluorescence and scanning electron microscopy. Results demonstrate that the introduction of magnetite into the MWCNT structure increases biocompatibility of oxidized MWCNTs. In addition, the presence of a static magnetic field further increases Fe3O4/MWCNT influence on cell behaviour. These results demonstrate this novel Fe3O4/MWCNT hybrid composite has good potential for tissue engineering applications.

  12. Effects of precursor thermal aging and fiber arrangement on the properties of carbon/carbon (C/C) composites

    SciTech Connect

    Ma, C.C.M.; Chang, W.C.; Tai, N.H.

    1993-12-31

    Carbon/carbon composites fabricated by the pyrolysis of high strength carbon fiber fabrics reinforced phenolic resin were investigated. A liquid impregnation process has been used to fabricate composite precursor for 2-D carbon/carbon composite and an unique pultrusion process also used to fabricate the 1-D carbon/carbon composite precursor. Effects of thermal aging of the precursor on flexural strength of the resulted carbon/carbon composites are studied. Results shows that suitable thermal aging improves the flexural properties of carbon/carbon composites in this study. And based on the SEM examination and flexural tests, they show that the 2-D plain woven fiber arrangement results the significant degradation of the carbon fiber and the decreasing of composites flexural properties.

  13. Color stability of modern composites subjected to different periods of accelerated artificial aging.

    PubMed

    Drubi-Filho, Brahim; Garcia, Lucas da Fonseca Roberti; Cruvinel, Diogo Rodrigues; Sousa, Ana Beatriz Silva; Pires-de-Souza, Fernanda de Carvalho Panzeri

    2012-01-01

    The aim of this study was to evaluate the color stability of composites subjected to different periods of accelerated artificial aging (AAA). A polytetrafluorethylene matrix (10 x 2 mm) was used to fabricate 24 test specimens of three different composites (n=8): Tetric Ceram (Ivoclar/Vivadent); Filtek P90 and Z250 (3M ESPE), shade A3. After light activation for 20 s (FlashLite 1401), polishing and initial color readout (Spectrophotometer PCB 687; BYK Gardner), the test specimens were subjected to AAA (C-UV; Comexim), in 8-h cycles: 4 h exposure to UV-B rays at 50°C and 4 h condensation at 50°C. At the end of each cycle, color readouts were taken and the test ended when the mean value of ΔE attained a level ≥3.30. Tetric Ceram presented alteration in ΔE equal to 3.33 in the first aging cycle. For Filtek P90 and Z250, two (ΔE=3.60) and four (ΔE=3.42) AAA cycles were necessary. After each cycle, there was a reduction of luminosity in all the samples (ΔL). It was concluded that a short period of AAA was sufficient to promote clinically unacceptable color alteration in composites, and that this alteration was material-dependent. PMID:23306237

  14. Color stability of modern composites subjected to different periods of accelerated artificial aging.

    PubMed

    Drubi-Filho, Brahim; Garcia, Lucas da Fonseca Roberti; Cruvinel, Diogo Rodrigues; Sousa, Ana Beatriz Silva; Pires-de-Souza, Fernanda de Carvalho Panzeri

    2012-01-01

    The aim of this study was to evaluate the color stability of composites subjected to different periods of accelerated artificial aging (AAA). A polytetrafluorethylene matrix (10 x 2 mm) was used to fabricate 24 test specimens of three different composites (n=8): Tetric Ceram (Ivoclar/Vivadent); Filtek P90 and Z250 (3M ESPE), shade A3. After light activation for 20 s (FlashLite 1401), polishing and initial color readout (Spectrophotometer PCB 687; BYK Gardner), the test specimens were subjected to AAA (C-UV; Comexim), in 8-h cycles: 4 h exposure to UV-B rays at 50°C and 4 h condensation at 50°C. At the end of each cycle, color readouts were taken and the test ended when the mean value of ΔE attained a level ≥3.30. Tetric Ceram presented alteration in ΔE equal to 3.33 in the first aging cycle. For Filtek P90 and Z250, two (ΔE=3.60) and four (ΔE=3.42) AAA cycles were necessary. After each cycle, there was a reduction of luminosity in all the samples (ΔL). It was concluded that a short period of AAA was sufficient to promote clinically unacceptable color alteration in composites, and that this alteration was material-dependent.

  15. Oil productivity and composition of sunflower as a function of hybrid and planting date

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sunflower (Helianthus annuus L.) is potential cash crop for the southeastern United States for production of cooking oil or biodiesel. Two years of experiments were conducted to evaluate the effect of location (five locations in Mississippi), planting date (April 20, May 20, and June 20), and hybrid...

  16. Hybrid composites, state-of-the-art review: Analysis, design, application and fabrication

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Lark, R. F.

    1977-01-01

    The areas of constituents and types of hybrids, analytical methods, design methods, applications, and fabrication procedures are discussed. The review summarizes significant contributions in each area and points out areas for further research. The description of each significant contribution is supplemented with pertinent illustrations and references.

  17. Pedestrian dynamics in single-file movement of crowd with different age compositions

    NASA Astrophysics Data System (ADS)

    Cao, Shuchao; Zhang, Jun; Salden, Daniel; Ma, Jian; Shi, Chang'an; Zhang, Ruifang

    2016-07-01

    An aging population is bringing new challenges to the management of escape routes and facility design in many countries. This paper investigates pedestrian movement properties of crowd with different age compositions. Three pedestrian groups are considered: young student group, old people group, and mixed group. It is found that traffic jams occur more frequently in mixed group due to the great differences of mobilities and self-adaptive abilities among pedestrians. The jams propagate backward with a velocity 0.4 m /s for global density ρg≈1.75 m-1 and 0.3 m /s for ρg>2.3 m-1 . The fundamental diagrams of the three groups are obviously different from each other and cannot be unified into one diagram by direct nondimensionalization. Unlike previous studies, three linear regimes in mixed group but only two regimes in young student group are observed in the headway-velocity relation, which is also verified in the fundamental diagram. Different ages and mobilities of pedestrians in a crowd cause the heterogeneity of system and influence the properties of pedestrian dynamics significantly. It indicates that the density is not the only factor leading to jams in pedestrian traffic. The composition of crowd has to be considered in understanding pedestrian dynamics and facility design.

  18. Pedestrian dynamics in single-file movement of crowd with different age compositions.

    PubMed

    Cao, Shuchao; Zhang, Jun; Salden, Daniel; Ma, Jian; Shi, Chang'an; Zhang, Ruifang

    2016-07-01

    An aging population is bringing new challenges to the management of escape routes and facility design in many countries. This paper investigates pedestrian movement properties of crowd with different age compositions. Three pedestrian groups are considered: young student group, old people group, and mixed group. It is found that traffic jams occur more frequently in mixed group due to the great differences of mobilities and self-adaptive abilities among pedestrians. The jams propagate backward with a velocity 0.4m/s for global density ρ_{g}≈1.75m^{-1} and 0.3m/s for ρ_{g}>2.3m^{-1}. The fundamental diagrams of the three groups are obviously different from each other and cannot be unified into one diagram by direct nondimensionalization. Unlike previous studies, three linear regimes in mixed group but only two regimes in young student group are observed in the headway-velocity relation, which is also verified in the fundamental diagram. Different ages and mobilities of pedestrians in a crowd cause the heterogeneity of system and influence the properties of pedestrian dynamics significantly. It indicates that the density is not the only factor leading to jams in pedestrian traffic. The composition of crowd has to be considered in understanding pedestrian dynamics and facility design.

  19. Pedestrian dynamics in single-file movement of crowd with different age compositions.

    PubMed

    Cao, Shuchao; Zhang, Jun; Salden, Daniel; Ma, Jian; Shi, Chang'an; Zhang, Ruifang

    2016-07-01

    An aging population is bringing new challenges to the management of escape routes and facility design in many countries. This paper investigates pedestrian movement properties of crowd with different age compositions. Three pedestrian groups are considered: young student group, old people group, and mixed group. It is found that traffic jams occur more frequently in mixed group due to the great differences of mobilities and self-adaptive abilities among pedestrians. The jams propagate backward with a velocity 0.4m/s for global density ρ_{g}≈1.75m^{-1} and 0.3m/s for ρ_{g}>2.3m^{-1}. The fundamental diagrams of the three groups are obviously different from each other and cannot be unified into one diagram by direct nondimensionalization. Unlike previous studies, three linear regimes in mixed group but only two regimes in young student group are observed in the headway-velocity relation, which is also verified in the fundamental diagram. Different ages and mobilities of pedestrians in a crowd cause the heterogeneity of system and influence the properties of pedestrian dynamics significantly. It indicates that the density is not the only factor leading to jams in pedestrian traffic. The composition of crowd has to be considered in understanding pedestrian dynamics and facility design. PMID:27575153

  20. Depth versus age: new perspectives from the chemical compositions of ancient crust

    NASA Astrophysics Data System (ADS)

    Humlera, Eric; Langmuirb, Charles; Dauxc, Vaiérie

    1999-11-01

    Petrological data provide a new approach to an evaluation of the depth-age problem for ancient seafloor. The correlations among basalt chemical composition, axial depth and mantle temperature at current ocean ridges allow the determination of initial depth and mantle temperature for any portion of ancient seafloor that was created at a spreading center, provided the chemical composition of the ancient crust is determined. It is then possible to calculate a petrologically constrained depth at any age, which can be compared to observed depths and depths from the classical half space models. We evaluate data from DSDP and ODP drill holes on crust older than 80 Ma, considering chemical composition, back-tracked depth and crustal thickness. The data are complex, and interpretation of their chemical composition requires consideration of alteration, absence of glass compositions, data quality, and the influence of off-axis volcanism and near-ridge hot spots. To check and expand the data set, we develop and use trace element proxies for major element compositions, since many trace element ratios are less influenced by alteration and by variable proportions of phenocrysts. The twenty drill holes for which reliable data can be obtained are well distributed around the globe, and include multiple sites on old crust in the Atlantic, Pacific and Indian ocean basins. Comparison of the chemical and crustal distributions between ancient and current N-MORB show that the oceanic crust older than 80 Ma has significantly lower Na 8.0,Zr/Y, Sm/Yb N, and higher CaO/Al 2O 3,Fe 8.0 and crustal thickness. Quantitative modeling of these results suggests that the mantle was hotter in this time period by about 50°C, that the cruss was several hundred meters shallower and 1-2 km thicker. These observations show that half to two thirds of the observed flattening relative to a half space model is due to the change in mantle temperature and crustal composition. Thus, only a few hundred meters of

  1. Free radical entrapment and crystallinity of resin composites after accelerated aging as a function of the expiration date.

    PubMed

    D'Alpino, Paulo Henrique Perlatti; Vismara, Marcos Vinícius Gonçalves; González, Alejandra Hortencia Miranda; Graeff, Carlos Frederico de Oliveira

    2014-08-01

    This study evaluated the spin concentration and the crystallinity in different classifications of dental composites as a function of the material condition (new, aged and expired). Specimens were obtained according to the factors: composites: Filtek P60, Filtek Z250, Filtek Z350XT, and Filtek Silorane; and material conditions: new, aged, and expired. The syringe composites underwent an accelerated aging protocol (Arrhenius model). The magnetic properties of the composites were characterized using Electron Paramagnetic Resonance (EPR) and the concentration of spins (number of spins/mass) was calculated. The crystallinity of the composites tested was characterized with X-ray diffraction (XRD). Filtek P60 and Filtek Z250 presented similarities in terms of spin concentration and crystallinity, irrespective of the material condition. The aging protocol influenced the composite Filtek Z350XT that exhibited a significant increase in the spin concentration. Besides, lower intensity peaks of the organic matrix and amorphous silica were also observed for both aged and expired Filtek Z350XT. Although a significant lower spin concentration was observed for the silorane composite in comparison to that of the methacrylates, a decrease in the relative intensity of peaks of the amorphous region related to the organic components in the diffractograms was observed. The material conditions tested influence the crystallinity and the magnetic properties of the composites evaluated.

  2. Hybrid nanostructured microporous carbon-mesoporous carbon doped titanium dioxide/sulfur composite positive electrode materials for rechargeable lithium-sulfur batteries

    NASA Astrophysics Data System (ADS)

    Zegeye, Tilahun Awoke; Kuo, Chung-Feng Jeffrey; Wotango, Aselefech Sorsa; Pan, Chun-Jern; Chen, Hung-Ming; Haregewoin, Atetegeb Meazah; Cheng, Ju-Hsiang; Su, Wei-Nien; Hwang, Bing-Joe

    2016-08-01

    Herein, we design hybrid nanostructured microporous carbon-mesoporous carbon doped titanium dioxide/sulfur composite (MC-Meso C-doped TiO2/S) as a positive electrode material for lithium-sulfur batteries. The hybrid MC-Meso C-doped TiO2 host material is produced by a low-cost, hydrothermal and annealing process. The resulting conductive material shows dual microporous and mesoporous behavior which enhances the effective trapping of sulfur and polysulfides. The hybrid MC-Meso C-doped TiO2/S composite material possesses rutile TiO2 nanotube structure with successful carbon doping while sulfur is uniformly distributed in the hybrid MC-Meso C-doped TiO2 composite materials after the melt-infusion process. The electrochemical measurement of the hybrid material also shows improved cycle stability and rate performance with high sulfur loading (61.04%). The material delivers an initial discharge capacity of 802 mAh g-1 and maintains it at 578 mAh g-1 with a columbic efficiency greater than 97.1% after 140 cycles at 0.1 C. This improvement is thought to be attributed to the unique hybrid nanostructure of the MC-Meso C-doped TiO2 host and the good dispersion of sulfur in the narrow pores of the MC spheres and the mesoporous C-doped TiO2 support.

  3. Hybrid nanostructured microporous carbon-mesoporous carbon doped titanium dioxide/sulfur composite positive electrode materials for rechargeable lithium-sulfur batteries

    NASA Astrophysics Data System (ADS)

    Zegeye, Tilahun Awoke; Kuo, Chung-Feng Jeffrey; Wotango, Aselefech Sorsa; Pan, Chun-Jern; Chen, Hung-Ming; Haregewoin, Atetegeb Meazah; Cheng, Ju-Hsiang; Su, Wei-Nien; Hwang, Bing-Joe

    2016-08-01

    Herein, we design hybrid nanostructured microporous carbon-mesoporous carbon doped titanium dioxide/sulfur composite (MC-Meso C-doped TiO2/S) as a positive electrode material for lithium-sulfur batteries. The hybrid MC-Meso C-doped TiO2 host material is produced by a low-cost, hydrothermal and annealing process. The resulting conductive material shows dual microporous and mesoporous behavior which enhances the effective trapping of sulfur and polysulfides. The hybrid MC-Meso C-doped TiO2/S composite material possesses rutile TiO2 nanotube structure with successful carbon doping while sulfur is uniformly distributed in the hybrid MC-Meso C-doped TiO2 composite materials after the melt-infusion process. The electrochemical measurement of the hybrid material also shows improved cycle stability and rate performance with high sulfur loading (61.04%). The material delivers an initial discharge capacity of 802 mAh g-1 and maintains it at 578 mAh g-1 with a columbic efficiency greater than 97.1% after 140 cycles at 0.1 C. This improvement is thought to be attributed to the unique hybrid nanostructure of the MC-Meso C-doped TiO2 host and the good dispersion of sulfur in the narrow pores of the MC spheres and the mesoporous C-doped TiO2 support.

  4. Characterization of radiation-induced aging in silica-reinforced polysiloxane composites

    NASA Astrophysics Data System (ADS)

    Chien, Allen; Maxwell, Robert; Chambers, David; Balazs, Bryan; LeMay, James

    2000-11-01

    Changes in crosslink density and chemical structure of silica-reinforced silicone polymer composites due to aging in gamma radiation environments were examined in this study. Solvent swelling was utilized to determine the individual contributions of the matrix polymer and filler phase to the overall crosslink density of silica-reinforced silicone polymer composites. The results show how polymer-filler hydrogen bonding dominates the overall crosslink density of the material. Air-irradiated samples displayed decreased hydrogen bonding at the polymer-filler interface, while vacuum irradiation revealed the opposite effect. These results were supported by solid-state NMR experiments that correlated the motional dynamics of the polymer chains with crosslink density through T2 relaxation time measurements. GC/MS analysis was used to identify degradation products formed as a result of irradiation and speculate upon likely degradation mechanisms.

  5. Effect of postpolymerization method on the color stability of composite resins submitted to ultraviolet aging.

    PubMed

    Santos, Paulo Henrique dos; Souza, Fernando Isquierdo de; Guedes, Ana Paula Albuquerque; Pavan, Sabrina

    2012-06-01

    The aim of this research was to evaluate the effect of postpolymerization method on the color stability of resin-based composites. Samples of direct and indirect restorative materials were polymerized with two photo-curing units (Visio photo-curing oven system and LED Elipar Freelight 2). All samples were submitted to an initial chromatic analysis using a spectrometer and submitted to ultraviolet-accelerated artificial aging. The direct material showed less color change than the indirect material, independent of the photo-activation method used. Samples photo cured with the LED system showed less change than those photo cured with the Visio system. The postpolymerization oven did not improve the color stability of direct and indirect resin-based composites.

  6. Lamb Wave Stiffness Characterization of Composites Undergoing Thermal-Mechanical Aging

    NASA Technical Reports Server (NTRS)

    Seale, Michael D.; Madaras, Eric I.

    2004-01-01

    The introduction of new, advanced composite materials into aviation systems requires a thorough understanding of the long term effects of combined thermal and mechanical loading upon those materials. Analytical methods investigating the effects of intense thermal heating combined with mechanical loading have been investigated. The damage mechanisms and fatigue lives were dependent on test parameters as well as stress levels. Castelli, et al. identified matrix dominated failure modes for out-of-phase cycling and fiber dominated damage modes for in-phase cycling. In recent years, ultrasonic methods have been developed that can measure the mechanical stiffness of composites. To help evaluate the effect of aging, a suitably designed Lamb wave measurement system is being used to obtain bending and out-of-plane stiffness coefficients of composite laminates undergoing thermal-mechanical loading. The system works by exciting an antisymmetric Lamb wave and calculating the velocity at each frequency from the known transducer separation and the measured time-of-flight. The same peak in the waveforms received at various distances is used to measure the time difference between the signals. The velocity measurements are accurate and repeatable to within 1% resulting in reconstructed stiffness values repeatable to within 4%. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the dispersion curve. A mechanical scanner is used to move the sensors over the surface to map the time-of-flight, velocity, or stiffnesses of the entire specimen. Access to only one side of the material is required and no immersion or couplants are required because the sensors are dry coupled to the surface of the plate. In this study, the elastic stiffnesses D(sub 11), D(sub 22), A(sub 44), and A(sub 55) as well as time-of-flight measurements for composite samples that have undergone combined thermal and mechanical aging for

  7. Time-Dependent Behavior of a Graphite/Thermoplastic Composite and the Effects of Stress and Physical Aging

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.; Feldman, Mark

    1995-01-01

    Experimental studies were performed to determine the effects of stress and physical aging on the matrix dominated time dependent properties of IM7/8320 composite. Isothermal tensile creep/aging test techniques developed for polymers were adapted for testing of the composite material. Time dependent transverse and shear compliance's for an orthotropic plate were found from short term creep compliance measurements at constant, sub-T(8) temperatures. These compliance terms were shown to be affected by physical aging. Aging time shift factors and shift rates were found to be a function of temperature and applied stress.

  8. Detection of transverse cracking in a hybrid composite laminate using acoustic emission

    NASA Astrophysics Data System (ADS)

    Jong, Hwai-Jiang

    Transverse cracking detection in a uniaxially-loaded symmetric cross-ply hybrid laminate containing 0° IM7/8552 carbon/epoxy and a very thin 90° 52/8552 glass/epoxy layer is studied using the acoustic emission (AE) technique. By conducting modal-based AE experiments and analysis, we investigate some parameters that can be used as the waveform signatures to identify transverse crack growth in the hybrid laminate. Wave dispersion relations of the hybrid laminate are established, and a comparison with those from a material homogenization model based on the equivalent stiffness is made. It is found that material homogenization is not accurate for predicting wave dispersion in the hybrid laminate. Wave dispersion for a homogeneous IM7/8552 unidirectional plate is also constructed. Cut-off frequencies belonging to various wave modes are discussed concerning their significance in interpreting AE signals. The wave attenuation behaviors that exist in the hybrid laminate and in the homogeneous IM7/8552 plate are compared and discussed using the finite element method (FEM). The use of singular elements dealing with the high strain gradient near the crack tip is addressed for convergence purposes. It is shown by the FEM results and demonstrated in the AE experiments that wave attenuation in the cross-ply hybrid laminate is much stronger than in the plain IM7/8552 plate. A simple calibration method for the AE sensors is discussed. Some important aspects in conducting an AE experiment, such as the sensor averaging effect and sensor frequency response range, are addressed. A new source location method based on the waveform's first peak search and the associated primary frequency content is proposed. The accuracy of the source location method is verified by pencil-lead break experiments. The so-called symmetric energy fraction (SEF) of the AE signals in conjunction with the finite element analysis result in identification of the transverse cracking event. Lastly, a material

  9. Synthesis of Cu-Deficient and Zn-Graded Cu-In-Zn-S Quantum Dots and Hybrid Inorganic-Organic Nanophosphor Composite for White Light Emission.

    PubMed

    Ilaiyaraja, P; Mocherla, Pavana S V; Srinivasan, T K; Sudakar, C

    2016-05-18

    Cu-deficient graded-zinc Cu-In-Zn-S (CIZS) quantum dots (QDs) were synthesized by a two-step solvothermal method. These CIZS QDs exhibited size and composition tunable photoluminescence characteristics with emission color tunable from greenish-yellow to orange to red with a relatively high quantum yield between 45 and 60%. Novel white-light-emitting (WLE) hybrid composite is fabricated by integrating the blue-emissive 1,4-bis-2-(5-phenyl oxazolyl)-benzene (POPOP) organic fluorophore and quaternary CIZS inorganic QDs. Integrating CIZS QDs with POPOP fluorophore resulted in series of tunable emission colors with CIE coordinates lying in a straight line between the coordinates of the end member. WLE was shown for hybrid mixture comprising 0.5 nM of POPOP and 3 mg/mL of CIZS QDs with color coordinates (0.3312, 0.3324). Thin films of this hybrid mixture in PMMA matrix coated on UV-LED or on glass substrates with UV backlit light also showed broadband WLE with ideal CIE color coordinates of (0.34, 0.33), high color-rendering index value of 92, and correlated color temperature value of 5143 K. The hybrid composite exhibit Forster resonance energy transfer cascading from POPOP to CIZS which results in emission covering the entire visible spectral range. POPOP and CIZS QDs hybrid composite is a versatile material for WLED applications. PMID:27135154

  10. Hybrid local FEM/global LISA modeling of guided wave propagation and interaction with damage in composite structures

    NASA Astrophysics Data System (ADS)

    Shen, Yanfeng; Cesnik, Carlos E. S.

    2015-03-01

    This paper presents a hybrid modeling technique for the efficient simulation of guided wave propagation and interaction with damage in composite structures. This hybrid approach uses a local finite element model (FEM) to compute the excitability of guided waves generated by piezoelectric transducers, while the global domain wave propagation, wave-damage interaction, and boundary reflections are modeled with the local interaction simulation approach (LISA). A small-size multi-physics FEM with non-reflective boundaries (NRB) was built to obtain the excitability information of guided waves generated by the transmitter. Frequency-domain harmonic analysis was carried out to obtain the solution for all the frequencies of interest. Fourier and inverse Fourier transform and frequency domain convolution techniques are used to obtain the time domain 3-D displacement field underneath the transmitter under an arbitrary excitation. This 3-D displacement field is then fed into the highly efficient time domain LISA simulation module to compute guided wave propagation, interaction with damage, and reflections at structural boundaries. The damping effect of composite materials was considered in the modified LISA formulation. The grids for complex structures were generated using commercial FEM preprocessors and converted to LISA connectivity format. Parallelization of the global LISA solution was achieved through Compute Unified Design Architecture (CUDA) running on Graphical Processing Unit (GPU). The multi-physics local FEM can reliably capture the detailed dimensions and local dynamics of the piezoelectric transducers. The global domain LISA can accurately solve the 3-D elastodynamic wave equations in a highly efficient manner. By combining the local FEM with global LISA, the efficient and accurate simulation of guided wave structural health monitoring procedure is achieved. Two numerical case studies are presented: (1) wave propagation in a unidirectional CFRP composite plate

  11. Light Plains in the South-Pole Aitken Basin: Surface Ages and Mineralogical Composition

    NASA Astrophysics Data System (ADS)

    Thiessen, F.; Hiesinger, H.; van der Bogert, C. H.; Pasckert, J. H.; Robinson, M. S.

    2012-04-01

    We studied light plains in the north-eastern South-Pole Aitken basin to investigate their origin, ages, and mineralogical composition. Light plains, also known as the Cayley Formation, occur on the near- and farside of the Moon. Due to their smooth texture, lower crater densities, and occurrence as crater fills, they were thought to be of volcanic origin [e.g., 1]. However, Apollo 16 samples of light plains deposits were in fact highly brecciated rocks [2]. Therefore, the Imbrium and Orientale impacts were thought to have formed light plains because they reshaped the surface thousands of kilometers from their impact sites. Subsequent studies revealed varying surface ages of light plains [e.g., 3] and different mineralogical compositions, which are in some cases more highland-like and in others more mare-like. Hence, an origin solely from the Imbrium and/or Orientale impacts is unlikely. Thus, the question whether light plains formed due to large impacts or regional cratering, or through endogenic processes remains open. We performed crater size-frequency measurements [e.g., 4] on Lunar Reconnaissance Orbiter Wide Angle Camera images and obtained absolute model ages between 3.43 and 3.81 Ga. We observed neither a distinctive peak of light plains ages nor clustering of similar ages in any specific regions of the studied area. Due to the fact that the derived ages vary as much as 380 Ma, an origin by a single event seems unlikely. Moreover, some ages even post-date the Imbrium and Orientale impacts, and thus an origin related to those impacts is not likely. Examination of multispectral data from Clementine [5] shows that the Ti abundances vary between 0.2 and 3 wt % and Fe abundances between 12.5 and 19 wt %. We observed a regional difference in distribution: light plains units within the Apollo basin have lower Fe and Ti values and are more highland-like, whereas light plains outside the Apollo basin show higher Fe and Ti values and are more mare-like. Furthermore, M

  12. Association of Eating Behavior With Nutritional Status and Body Composition in Primary School-Aged Children.

    PubMed

    Tay, Chee Wee; Chin, Yit Siew; Lee, Shoo Thien; Khouw, Ilse; Poh, Bee Koon

    2016-07-01

    Problematic eating behaviors during childhood may lead to positive energy balance and obesity. Therefore, this study aims to investigate the association of eating behaviors with nutritional status and body composition in Malaysian children aged 7 to 12 years. A total of 1782 primary schoolchildren were randomly recruited from 6 regions in Malaysia. The multidimensional Children's Eating Behaviour Questionnaire (CEBQ) was reported by parents to determine the 8 different dimensions of eating styles among children. Body mass index (BMI), BMI-for-age Z-score, waist circumference, and body fat percentage were assessed. Linear regression analyses revealed that both food responsiveness and desire to drink subscales were positively associated with a child's body adiposity, whereas satiety responsiveness, slowness in eating, and emotional undereating subscales were negatively associated with adiposity (all P < .05). A multidimensional eating style approach based on the CEBQ is needed to promote healthy eating behaviors in order to prevent excessive weight gain and obesity problems among Malaysian children. PMID:27252248

  13. Association of Eating Behavior With Nutritional Status and Body Composition in Primary School-Aged Children.

    PubMed

    Tay, Chee Wee; Chin, Yit Siew; Lee, Shoo Thien; Khouw, Ilse; Poh, Bee Koon

    2016-07-01

    Problematic eating behaviors during childhood may lead to positive energy balance and obesity. Therefore, this study aims to investigate the association of eating behaviors with nutritional status and body composition in Malaysian children aged 7 to 12 years. A total of 1782 primary schoolchildren were randomly recruited from 6 regions in Malaysia. The multidimensional Children's Eating Behaviour Questionnaire (CEBQ) was reported by parents to determine the 8 different dimensions of eating styles among children. Body mass index (BMI), BMI-for-age Z-score, waist circumference, and body fat percentage were assessed. Linear regression analyses revealed that both food responsiveness and desire to drink subscales were positively associated with a child's body adiposity, whereas satiety responsiveness, slowness in eating, and emotional undereating subscales were negatively associated with adiposity (all P < .05). A multidimensional eating style approach based on the CEBQ is needed to promote healthy eating behaviors in order to prevent excessive weight gain and obesity problems among Malaysian children.

  14. Effect of Nanoclay Reinforcement on the Friction Braking Performance of Hybrid Phenolic Friction Composites

    NASA Astrophysics Data System (ADS)

    Singh, Tej; Patnaik, Amar; Satapathy, Bhabani K.; Kumar, Mukesh; Tomar, Bharat S.

    2013-03-01

    Friction composite formulation consisting of decreasing nanoclay/lapinus fibres content, increasing graphite/aramid fibres content, and master batch of phenolic/barite is designed, fabricated, and characterized for their mechanical, thermo-mechanical, and tribological studies in braking situations. A standard test protocol is adopted for evaluating braking performance. The nanoclay content (≤2.25 wt.%) enhances hardness, impact strength, storage, and loss modulus characteristics of the friction composites. Such composites exhibit higher friction stability as well as variability coefficient. However, composites with higher content of nanoclay (~2.75 wt.%) exhibit moderate level of stability coefficient and minimum variability coefficient. Fade performance improves with nanoclay content whereas friction fluctuations increase continuously with increasing nanoclay content. The disc temperature continuously rises with nanoclay contents, it becomes maximum for nanoclay content 2.75 wt.%. The same composition found to be effective in arresting temperature rise, arrests fading, improves recovery, moderate stability with minimum variability coefficient, and higher level of μ-performance hence recommended. The wear performance deteriorates with lapinus/nanoclay content and improves with the amount of aramid/graphite in the friction composites. Worn surface morphology study (using SEM) reveals the associated wear mechanisms responsible for wear of investigated composites. XRD study confirms the presence and dispersion of nanoclay with other composite ingredients.

  15. Hybrid Processing with Powders and Solutions: A Novel Approach to Deposit Composite Coatings

    NASA Astrophysics Data System (ADS)

    Joshi, S. V.; Sivakumar, G.

    2015-10-01

    Thermal spraying employing either solution precursor or suspension feedstock offers an exciting opportunity to obtain coatings with microstructures and characteristics that differ vastly compared to those conventionally produced using spray-grade powders. Both solution precursor plasma spray and suspension plasma spray techniques have been explored extensively in recent years for depositing wide ranging ceramic coatings for various functional applications. Encouraged by the properties achieved using the above solution-based feedstocks, a hybrid approach involving dual injection of solutions and powders, either simultaneously or sequentially, has been proposed and demonstrated to yield novel coating architectures. Although prior work on such hybrid processing is very limited, this overview seeks to present the concept, outline associated challenges, and demonstrate its efficacy to realize coatings with exciting and unusual properties using some illustrative examples.

  16. Optimization of hybrid laminated composites using the multi-objective gravitational search algorithm (MOGSA)

    NASA Astrophysics Data System (ADS)

    Hemmatian, Hossein; Fereidoon, Abdolhossein; Assareh, Ehsanolah

    2014-09-01

    The multi-objective gravitational search algorithm (MOGSA) technique is applied to hybrid laminates to achieve minimum weight and cost. The investigated laminate is made of glass-epoxy and carbon-epoxy plies to combine the economical attributes of the first with the light weight and high-stiffness properties of the second in order to make the trade-off between the cost and weight as the objective functions. The first natural flexural frequency was considered as a constraint. The results obtained using the MOGSA, including the Pareto set, optimum stacking sequences and number of plies made of either glass or carbon fibres, were compared with those using the genetic algorithm (GA) and ant colony optimization (ACO) reported in the literature. The comparisons confirmed the advantages of hybridization and showed that the MOGSA outperformed the GA and ACO in terms of the functions' value and constraint accuracy.

  17. A hybrid Brownian dynamics/constitutive model for yielding, aging, and rejuvenation in deforming polymeric glasses.

    PubMed

    Zou, Weizhong; Larson, Ronald G

    2016-08-10

    We present a hybrid model for polymeric glasses under deformation that combines a minimal model of segmental dynamics with a beads-and-springs model of a polymer, solved by Brownian dynamics (BD) simulations, whose relaxation is coupled to the segmental dynamics through the drag coefficient of the beads. This coarse-grained model allows simulations that are much faster than molecular dynamics and successfully capture the entire range of mechanical response including yielding, plastic flow, strain-hardening, and incomplete strain recovery. The beads-and-springs model improves upon the dumbbell model for glassy polymers proposed by Fielding et al. (Phys. Rev. Lett., 2012, 108, 048301) by capturing the small elastic recoil seen experimentally without the use of ad hoc adjustments of parameters required in the model of Fielding et al. With appropriate choice of parameters, predictions of creep, recovery, and segmental relaxation are found to be in good agreement with poly(methylmethacrylate) (PMMA) data of Lee et al. (Science, 2009, 323, 231-234). Our model shows dramatic differences in behavior of the segmental relaxation time between extensional creep and steady extension, and between extension and shear. The non-monotonic response of the segmental relaxation time to extensional creep and the small elastic recovery after removal of stress are shown to arise from sub-chains that are trapped between folds, and that become highly oriented and stretched at strains of order unity, connecting the behavior of glassy polymers under creep to that of dilute polymer solutions under fast extensional flows. We are also able to predict the effects of polymer pre-orientation in the parallel or orthogonal direction on the subsequent response to extensional deformation. PMID:27453365

  18. Core-shell nanostructured hybrid composites for volatile organic compound detection

    PubMed Central

    Tung, Tran Thanh; Losic, Dusan; Park, Seung Jun; Feller, Jean-Francois; Kim, TaeYoung

    2015-01-01

    We report a high-performance chemiresistive sensor for detection of volatile organic compound (VOC) vapors based on core-shell hybridized nanostructures of Fe3O4 magnetic nanoparticles (MNPs) and poly(3,4-ethylenedioxythiophene) (PEDOT)-conducting polymers. The MNPs were prepared using microwave-assisted synthesis in the presence of polymerized ionic liquids (PILs), which were used as a linker to couple the MNP and PEDOT. The resulting PEDOT–PIL-modified Fe3O4 hybrids were then explored as a sensing channel material for a chemiresistive sensor to detect VOC vapors. The PEDOT–PIL-modified Fe3O4 sensor exhibited a tunable response, with high sensitivity (down to a concentration of 1 ppm) and low noise level, to VOCs; these VOCs include acetone vapor, which is present in the exhaled breath of potential lung cancer patients. The present sensor, based on the hybrid nanostructured sensing materials, exhibited a 38.8% higher sensitivity and an 11% lower noise level than its PEDOT–PIL-only counterpart. This approach of embedding MNPs in conducting polymers could lead to the development of new electronic noses, which have significant potential for the use in the early diagnosis of lung cancer via the detection of VOC biomarkers. PMID:26357471

  19. Experimental and Numerical Investigations of Textile Hybrid Composites Subjected to Low Velocity Impact Loadings

    PubMed Central

    Chandekar, Gautam S.; Kelkar, Ajit D.

    2014-01-01

    In the present study experimental and numerical investigations were carried out to predict the low velocity impact response of four symmetric configurations: 10 ply E Glass, 10 ply AS4 Carbon, and two Hybrid combinations with 1 and 2 outer plies of E Glass and 8 and 6 inner plies of Carbon. All numerical investigations were performed using commercial finite element software, LS-DYNA. The test coupons were manufactured using the low cost Heated Vacuum Assisted Resin Transfer Molding (H-VARTM©) technique. Low velocity impact testing was carried out using an Instron Dynatup 8250 impact testing machine. Standard 6 × 6 Boeing fixture was used for all impact experiments. Impact experiments were performed over progressive damage, that is, from incipient damage till complete failure of the laminate in six successive impact energy levels for each configuration. The simulation results for the impact loading were compared with the experimental results. For both nonhybrid configurations, it was observed that the simulated results were in good agreement with the experimental results, whereas, for hybrid configurations, the simulated impact response was softer than the experimental response. Maximum impact load carrying capacity was also compared for all four configurations based on their areal density. It was observed that Hybrid262 configuration has superior impact load to areal density ratio. PMID:24719573

  20. Body and carcass composition of Angus and Charolais steers as affected by age and nutrition.

    PubMed

    Coleman, S W; Evans, B C; Guenther, J J

    1993-01-01

    The objectives of this study were to examine the effects of a low vs moderate rate of gain during the growing phase on empty body and carcass composition during finishing of Angus and Charolais steers of two ages. Forty-eight Angus and 48 Charolais steers that were either spring-born (OLDER) or fall-born (YOUNGER) were fed two diets (alfalfa pellets [CON] or cubed grass-alfalfa hay, wheat straw, cottonseed hulls, and soybean meal [RES]) for a growing period followed by a conventional feedlot period. The feedlot period started when the YOUNGER-CON steers weighed the same as the OLDER-RES steers. At that time, an interaction of age x diet occurred in empty body fat content (P < .10), whereas breed and age x diet affected carcass fat content (P < .01). OLDER-CON steers were larger (average 378 kg empty BW) and fatter than the other, smaller groups (average 222 kg). Angus carcasses were fatter than Charolais carcasses (P < .01). At the end of the finishing phase, compensating steers (OLDER-RES) had fatter carcasses than OLDER-CON steers. Empty body fat content was affected by a breed x age x diet interaction (P < .10). Allometric regressions (Y = aXb) of fat on empty BW indicated that empty body fat accretion was greater in Angus than in Charolais and in YOUNGER than in OLDER steers. A breed x age x diet interaction (P < .10) indicated that OLDER-Angus had higher fat accretive rates than YOUNGER-Angus, whereas OLDER-CON-Charolais steers deposited fat more slowly than the remaining groups. These data suggest that steers receiving feedlot diets at light weights, whether young in age or previously restricted, accumulate fat more rapidly than do larger steers. This feeding strategy may be an advantage in late-maturing types, but moderate growth through approximately 75% of slaughter weight is recommended for early-maturing types.

  1. Moisture absorption and hygrothermal aging in a bismaleimide resin and its carbon fiber composites

    NASA Astrophysics Data System (ADS)

    Bao, Li-Rong

    Moisture absorption and hygrothermal aging in a commercial bismaleimide (BMI) resin (Cytec 5250-4 RTM) and its carbon fiber composites were systematically studied in this work. The neat resin displays a distinct two-stage absorption behavior, with an initial fast diffusion followed by a gradual increase in weight gain over an extended timescale. The true equilibrium uptake was not reached after two years. The second-stage diffusion is associated with moisture enhanced structural relaxation in the resin. Since water is a good plasticizer, it significantly decreases the glass transition temperature and enhances segmental mobility. Hence, the resin network can slowly relax in response to the swelling stresses created by absorbed moisture, resulting in additional uptake. As the resin is deep in the glassy state, the relaxation process is much slower than diffusion. Therefore, the first stage and second stage are diffusion and relaxation controlled, respectively. A simple mathematical model has been developed to describe this absorption behavior. Though a phenomenological model, this two-stage model can be quantitatively correlated with relaxation theories in the glassy stage. The general application of this model has also been demonstrated. Cyclic absorption experiments indicate that the structural relaxation is irreversible upon desorption. The material response under cyclic absorption conditions is solely determined by the absorption cycles, not the desorption cycles. This phenomenon is consistent with the plasticizing effect of water. Two types of reinforcements are used in the composites, namely, uni-weave and woven fabrics. The diffusivity and water uptake level of the composites are compared with those of the flash in an attempt to deduce the interface effect. In the case of the uni-weave composite, which is essentially a uni-directional fiber composite, the composite diffusivity and uptake level can be predicted from those of the neat resin and the fiber volume

  2. Role of physical activity and sleep duration in growth and body composition of preschool-aged children

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The impact of physical activity patterns and sleep duration on growth and body composition of preschool-aged children remains unresolved. Aims were (1) to delineate cross-sectional associations among physical activity components, sleep, total energy expenditure (TEE), and body size and composition; ...

  3. Optimal training dataset composition for SVM-based, age-independent, automated epileptic seizure detection.

    PubMed

    Bogaarts, J G; Gommer, E D; Hilkman, D M W; van Kranen-Mastenbroek, V H J M; Reulen, J P H

    2016-08-01

    Automated seizure detection is a valuable asset to health professionals, which makes adequate treatment possible in order to minimize brain damage. Most research focuses on two separate aspects of automated seizure detection: EEG feature computation and classification methods. Little research has been published regarding optimal training dataset composition for patient-independent seizure detection. This paper evaluates the performance of classifiers trained on different datasets in order to determine the optimal dataset for use in classifier training for automated, age-independent, seizure detection. Three datasets are used to train a support vector machine (SVM) classifier: (1) EEG from neonatal patients, (2) EEG from adult patients and (3) EEG from both neonates and adults. To correct for baseline EEG feature differences among patients feature, normalization is essential. Usually dedicated detection systems are developed for either neonatal or adult patients. Normalization might allow for the development of a single seizure detection system for patients irrespective of their age. Two classifier versions are trained on all three datasets: one with feature normalization and one without. This gives us six different classifiers to evaluate using both the neonatal and adults test sets. As a performance measure, the area under the receiver operating characteristics curve (AUC) is used. With application of FBC, it resulted in performance values of 0.90 and 0.93 for neonatal and adult seizure detection, respectively. For neonatal seizure detection, the classifier trained on EEG from adult patients performed significantly worse compared to both the classifier trained on EEG data from neonatal patients and the classier trained on both neonatal and adult EEG data. For adult seizure detection, optimal performance was achieved by either the classifier trained on adult EEG data or the classifier trained on both neonatal and adult EEG data. Our results show that age

  4. Ultrafast synthesis of MoS2 or WS2-reduced graphene oxide composites via hybrid microwave annealing for anode materials of lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Youn, Duck Hyun; Jo, Changshin; Kim, Jae Young; Lee, Jinwoo; Lee, Jae Sung

    2015-11-01

    An ultrafast and simple strategy to synthesize metal sulfides (MoS2 and WS2) anchored on reduced graphene oxide (RGO) composites is reported as anode materials for lithium ion batteries (LIBs). Metal sulfide nanocrystals with homogeneous dispersion onto conducting RGO sheets are obtained in only 45 s by hybrid microwave annealing (HMA) method. The synthesized materials, especially MoS2/RGO composite, exhibit a high Li capacity, an excellent rate capability, and a stable cycling performance, comparable to the reported best MS2/carbon composite electrodes. The results highlight the effectiveness of HMA method to fabricate the metal sulfide/RGO composites with excellent electric properties.

  5. Effect of cyclical thermal to mechanical properties of Hybrid Laminate Composites (HLC) with skin recycle polypropylene/natural fiber/halloysite and core PP/KF composites

    NASA Astrophysics Data System (ADS)

    Sri Suharty, Neng; Ismail, Hanafi; Suci Handayani, Desi; Diharjo, Kuncoro; Rachman Wibowo, Fajar; Arnita Wuri, Margaretha

    2016-02-01

    This research has successfully synthesized six hybrid laminate composites (HLC). These HLC consist of two layers skin composites and one layer of core PP/KF composites. There are sticked with epoxy adhesive by using cold press method. In this research 6 types of skin are used, namely the rPP (recycled polypropylene, HC1); rPP/DVB/PP-g-AA/KF (HC2); rPP/DVB/PP-g-AA/Hall (HC3); rPP/DVB/PP-g-AA/Hall+ZB (HC4); rPP/DVB/PP-g-AA/KF/Hall (HC5) and rPP/DVB/PP-g-AA/KF/Hall+ZB (HC6) composites. The mechanical properties assessment tensile strength (TS) of various HLC before and after cyclical thermal (CT) was done by ASTM D638. While testing the flame retardant: such as time to ignition (TTI) and burning rate (BR) was done by ASTM D635. Heat stability of HLC can be recognized by conducting the CT treatment. It is to determine the effect of fluctuating heat loads on mechanical properties of HLC materials. The TS result of five HLCs (HC2, HC3, HC4, HC5 and HC6) before CT treatment were higher than HC1 (blank HLC). Those five HLC are also able to increase the TTI and reduce the BR compared to HC1. The CT treatment conditions performed at 45 oC as much as 125 times. After CT treatment, the TS values only slightly decline compared to before CT treatment.

  6. Characterizing microscale aluminum composite layer properties on silicon solar cells with hybrid 3D scanning force measurements

    PubMed Central

    Bae, Sung-Kuk; Choi, Beomjoon; Chung, Haseung; Shin, Seungwon; Song, Hee-eun; Seo, Jung Hwan

    2016-01-01

    This article presents a novel technique to estimate the mechanical properties of the aluminum composite layer on silicon solar cells by using a hybrid 3-dimensional laser scanning force measurement (3-D LSFM) system. The 3-D LSFM system measures the material properties of sub-layers constituting a solar cell. This measurement is critical for realizing high-efficient ultra-thin solar cells. The screen-printed aluminum layer, which significantly affects the bowing phenomenon, is separated from the complete solar cell by removing the silicon (Si) layer with deep reactive ion etching. An elastic modulus of ~15.1 GPa and a yield strength of ~35.0 MPa for the aluminum (Al) composite layer were obtained by the 3-D LSFM system. In experiments performed for 6-inch Si solar cells, the bowing distances decreased from 12.02 to 1.18 mm while the Si layer thicknesses increased from 90 to 190 μm. These results are in excellent agreement with the theoretical predictions for ultra-thin Si thickness (90 μm) based on the obtained Al composite layer properties. PMID:26948248

  7. Characterizing microscale aluminum composite layer properties on silicon solar cells with hybrid 3D scanning force measurements

    NASA Astrophysics Data System (ADS)

    Bae, Sung-Kuk; Choi, Beomjoon; Chung, Haseung; Shin, Seungwon; Song, Hee-Eun; Seo, Jung Hwan

    2016-03-01

    This article presents a novel technique to estimate the mechanical properties of the aluminum composite layer on silicon solar cells by using a hybrid 3-dimensional laser scanning force measurement (3-D LSFM) system. The 3-D LSFM system measures the material properties of sub-layers constituting a solar cell. This measurement is critical for realizing high-efficient ultra-thin solar cells. The screen-printed aluminum layer, which significantly affects the bowing phenomenon, is separated from the complete solar cell by removing the silicon (Si) layer with deep reactive ion etching. An elastic modulus of ~15.1 GPa and a yield strength of ~35.0 MPa for the aluminum (Al) composite layer were obtained by the 3-D LSFM system. In experiments performed for 6-inch Si solar cells, the bowing distances decreased from 12.02 to 1.18 mm while the Si layer thicknesses increased from 90 to 190 μm. These results are in excellent agreement with the theoretical predictions for ultra-thin Si thickness (90 μm) based on the obtained Al composite layer properties.

  8. Characterizing microscale aluminum composite layer properties on silicon solar cells with hybrid 3D scanning force measurements.

    PubMed

    Bae, Sung-Kuk; Choi, Beomjoon; Chung, Haseung; Shin, Seungwon; Song, Hee-eun; Seo, Jung Hwan

    2016-01-01

    This article presents a novel technique to estimate the mechanical properties of the aluminum composite layer on silicon solar cells by using a hybrid 3-dimensional laser scanning force measurement (3-D LSFM) system. The 3-D LSFM system measures the material properties of sub-layers constituting a solar cell. This measurement is critical for realizing high-efficient ultra-thin solar cells. The screen-printed aluminum layer, which significantly affects the bowing phenomenon, is separated from the complete solar cell by removing the silicon (Si) layer with deep reactive ion etching. An elastic modulus of ~15.1 GPa and a yield strength of ~35.0 MPa for the aluminum (Al) composite layer were obtained by the 3-D LSFM system. In experiments performed for 6-inch Si solar cells, the bowing distances decreased from 12.02 to 1.18 mm while the Si layer thicknesses increased from 90 to 190 μm. These results are in excellent agreement with the theoretical predictions for ultra-thin Si thickness (90 μm) based on the obtained Al composite layer properties. PMID:26948248

  9. Characterizing microscale aluminum composite layer properties on silicon solar cells with hybrid 3D scanning force measurements.

    PubMed

    Bae, Sung-Kuk; Choi, Beomjoon; Chung, Haseung; Shin, Seungwon; Song, Hee-eun; Seo, Jung Hwan

    2016-03-07

    This article presents a novel technique to estimate the mechanical properties of the aluminum composite layer on silicon solar cells by using a hybrid 3-dimensional laser scanning force measurement (3-D LSFM) system. The 3-D LSFM system measures the material properties of sub-layers constituting a solar cell. This measurement is critical for realizing high-efficient ultra-thin solar cells. The screen-printed aluminum layer, which significantly affects the bowing phenomenon, is separated from the complete solar cell by removing the silicon (Si) layer with deep reactive ion etching. An elastic modulus of ~15.1 GPa and a yield strength of ~35.0 MPa for the aluminum (Al) composite layer were obtained by the 3-D LSFM system. In experiments performed for 6-inch Si solar cells, the bowing distances decreased from 12.02 to 1.18 mm while the Si layer thicknesses increased from 90 to 190 μm. These results are in excellent agreement with the theoretical predictions for ultra-thin Si thickness (90 μm) based on the obtained Al composite layer properties.

  10. Hydrothermal synthesis and characterization of hybrid Al/ZnO-GO composite for significant photodegrdation of dyes

    NASA Astrophysics Data System (ADS)

    Lellala, Kashinath; Namratha, K.; Sudhakar, K.; Byrappa, K.

    2016-05-01

    In the present work, undoped and doped Aluminum/Zinc Oxide - graphene oxide (Al/ZnO-GO) nanocomposite have been successfully synthesized by hydrothermal method from zinc acetate and aluminum nitrate solutions without using of any surfactant/stabilizing agents. The results show that the composites of GO nanosheets are decorated densely by Al/ZnO nanoparticles, which displays a good morphology and blend between GO and Al/ZnO. Hybrid composites exhibit an enhanced photocatalytic performance in reduction of dyes under UV-Vis radiation better than bare ZnO-GO and GO for methylene blue dye. The hydrothermal method leads to particles with a higher crystalline due to ambient temperature of the reaction and autogenously pressure conditions, which alters the phases and crystallizations of the nanocomposite. The optical band gap is narrowed to lower energy values due to controlled addition of aluminum and GO in the composite. The improved optical property in Al-doped ZnO flower decorated on GO can be attributed to the decrease in oxygen deficiency after Al doping. XRD, FTIR, UV-Vis spectroscopy, Raman, and Field Emission Scanning Electron Microscopy characterized the effects of Al doping on the structural characteristics and optical properties on the ZnO-GO.

  11. A study on verifying the effectiveness of 4-week composite weight-loss dietary supplement ingestion on body composition and blood lipid changes in middle-aged women

    PubMed Central

    Chun, Yoonseok; Lee, Namju; Park, Sok; Sung, Suhyun; Jung, Matthew; Kim, Jongkyu

    2015-01-01

    Purpose The purpose of this study was to investigate the effectiveness of a composite weight-loss dietary supplement on body composition and blood lipid changes in middle-aged women. Methods Thirty seven middle-aged women living in the Kyunggi area participated in this study and they were randomly divided into 2 groups (Dietary supplement ingestion group; DG, n = 20 and Placebo group; PG, n = 17). Blood draw and dual energy x-ray (DEXA) measurements were conducted to examine changes in body composition and blood lipids. Results There were no significant changes in weight and BMI in both groups. There was an interaction between the composite weight-loss dietary supplement intake and lean body mass in DG and there was a significant decrease in percent body fat in DG. Blood lipid changes in the study results showed that there was no significant difference in TC, TG, and LDL in both groups; however, there was a significant interaction between the composite weight-loss dietary supplement intake and HDL-C as well as an increase in the HDL-C of DG. Conclusion In conclusion, it seems that 4-week ingestion of the composite weight-loss dietary supplement decreased body fat, increased lean body mass, and increased HDL-C. Therefore, the composite weight-loss dietary supplement is expected to prevent obesity and induce health improvements in middle-aged women. PMID:26527460

  12. Microstructure and mechanical properties of composite resins subjected to accelerated artificial aging.

    PubMed

    dos Reis, Andréa Cândido; de Castro, Denise Tornavoi; Schiavon, Marco Antônio; da Silva, Leandro Jardel; Agnelli, José Augusto Marcondes

    2013-01-01

    The aim of this study was to investigate the influence of accelerated artificial aging (AAA) on the microstructure and mechanical properties of the Filtek Z250, Filtek Supreme, 4 Seasons, Herculite, P60, Tetric Ceram, Charisma and Filtek Z100. composite resins. The composites were characterized by Fourier-transform Infrared spectroscopy (FTIR) and thermal analyses (Differential Scanning Calorimetry - DSC and Thermogravimetry - TG). The microstructure of the materials was examined by scanning electron microscopy. Surface hardness and compressive strength data of the resins were recorded and the mean values were analyzed statistically by ANOVA and Tukey's test (α=0.05). The results showed significant differences among the commercial brands for surface hardness (F=86.74, p<0.0001) and compressive strength (F=40.31, p<0.0001), but AAA did not affect the properties (surface hardness: F=0.39, p=0.53; compressive strength: F=2.82, p=0.09) of any of the composite resins. FTIR, DSC and TG analyses showed that resin polymerization was complete, and there were no differences between the spectra and thermal curve profiles of the materials obtained before and after AAA. TG confirmed the absence of volatile compounds and evidenced good thermal stability up to 200 °C, and similar amounts of residues were found in all resins evaluated before and after AAA. The AAA treatment did not significantly affect resin surface. Therefore, regardless of the resin brand, AAA did not influence the microstructure or the mechanical properties.

  13. The history of mare volcanism in the Orientale Basin: Mare deposit ages, compositions and morphologies

    NASA Technical Reports Server (NTRS)

    Kadel, S. D.; Greeley, R.; Neukum, G.; Wagner, R.

    1993-01-01

    The eruptive history of mare basalts in the Orientale Basin has been studied, using Lunar Orbiter 4 high-resolution photographs, Zond 8 photographs, and recently acquired Galileo EM-1 multispectral images. This work represents a refined set of compositional data incorporating the use of a linear mixing model for mare compositions, crater count data, and a comprehensive morphologic analysis of Orientale Basin mare deposits. Evidence for multiple eruptive episodes has been found, with compositions ranging from medium- to high-Ti basalt (less than 4 to greater than 6 wt. percent TiO2). Eruptive styles included flood, rille-forming, and shield-forming eruptions. Impact crater densities of mare units in the Orientale Basin enable determination of the ages of these deposits, using the method of Neukum et al. Earliest eruptions of mare basalt in the basin occurred at greater than or equal to 3.80 Ga and the latest eruptions occurred at about 2.3-2.5 Ga. Hence, mare volcanism occurred over a period of nearly 1.5 Ga.

  14. An in vitro evaluation of microleakage in class V preparations restored with Hybrid versus Silorane composites

    PubMed Central

    Umer, Fahad; Naz, Farah; Khan, Farhan Raza

    2011-01-01

    Aim: To compare the difference in microleakage values using conventional and new low-shrink Silorane composites using the dye penetration method. Background: With improvement in adhesive technology, problems associated with composites have been largely overcome. However, microleakage due to polymerization shrinkage still remains a challenge. New Silorane-based composites are alleged to have less than 1% polymerization shrinkage, which would potentially decrease the microleakage, and hence, resolve this longstanding issue. Materials and Methods: The teeth were randomly divided into three groups (A,B, and C). Group A was restored with conventional composite (Valux™ Plus), with a total-etch protocol, Group B was restored with conventional composite, with a self-etch protocol, and group C were restored with a silorane-based composite (Filtek TMP90). Thermocycling at 200 cycles between 5 and 55°C ± 2°C with a dwell time of 60 seconds was conducted. The teeth were stained with methylene blue dye and then sectioned and viewed under a dissection microscope, afer which the microleakage was evaluated. Results: The interexaminer reliability was evaluated using the kappa score, which was acceptable (61 – 78%). The total-etch group performed statistically and significantly better (P < 0.001) at the occlusal margin and was marginally and statistically significant (P = 0.05) at the gingival margin compared to the self-etch conventional and Silorane groups. Conclusions: The Silorane composite did not perform better than the conventional composites, however, it may have its uses and requires further research. PMID:21814346

  15. Anthropometric characteristics and body composition in Mexican older adults: age and sex differences.

    PubMed

    López-Ortega, Mariana; Arroyo, Pedro

    2016-02-14

    Anthropometric reference data for older adults, particularly for the oldest old, are still limited, especially in developing countries. The aim of the present study was to describe sex- and age-specific distributions of anthropometric measurements and body composition in Mexican older adults. The methods included in the present study were assessment of height, weight, BMI, calf circumference (CC), waist circumference (WC) and hip circumference (HC) as well as knee height in a sample of 8883 Mexican adults aged 60 years and above and the estimation of sex- and age-specific differences in these measures. Results of the study (n 7865, 54% women) showed that men are taller, have higher BMI, and larger WC than women, whereas women presented higher prevalence of obesity and adiposity. Overall prevalence of underweight was 2·3% in men and 4·0% in women, with increasing prevalence with advancing age. Significant differences were found by age group for weight, height, WC, HC, CC, BMI and knee height (P<0·001), but no significant differences in waist-hip circumference were observed. Significant differences between men and women were found in height, weight, circumferences, BMI and knee height (P<0·001). These results, which are consistent with studies of older adults in other countries, can be used for comparison with other Mexican samples including populations living in the USA and other countries with similar developmental and socio-economic conditions. This information can also be used as reference in clinical settings as a tool for detection of individuals at risk of either underweight or overweight and obesity.

  16. Photothermal initiation of hybrid organic/inorganic metastable interstitial composites: synergistic effects on the dynamics of energy release.

    PubMed

    Mileham, Melissa L; Park, Chi-Dong; van de Burgt, Lambertus J; Kramer, Michael P; Stiegman, A E

    2008-12-11

    The organic high-energy material pentaerythritol tetranitrate (PETN) was incorporated at low concentrations into Al (100 nm)/Fe(2)O(3) metastable intersitital composites (MIC) to form a hybrid organic/inorganic high-energy material. Studies of the dynamics of energy release were carried out by initiating the reaction photothermally with a single 8 ns pulse of the 1064 nm fundamental of a Nd:YAG laser. The reaction dynamics were measured using time-resolved spectroscopy of the light emitted from the deflagrating material. Two parameters were measured: the time to initiation and the duration of the deflagration. The presence of small amounts of PETN (16 mg/g of MIC) results in a dramatic decrease in the initiation time. This is attributed to a contribution to the temperature of the reacting system from the combustion of the PETN that, at lower loadings, appears to follow an Arrhenius dependence. The presence of PETN was also found to reduce the energy density required for single-pulse photothermal initiation by an order of magnitude, suggesting that hybrid materials such as this may be engineered to optimize their use as an efficient photodetonation medium. PMID:18942803

  17. Photothermal initiation of hybrid organic/inorganic metastable interstitial composites: synergistic effects on the dynamics of energy release.

    PubMed

    Mileham, Melissa L; Park, Chi-Dong; van de Burgt, Lambertus J; Kramer, Michael P; Stiegman, A E

    2008-12-11

    The organic high-energy material pentaerythritol tetranitrate (PETN) was incorporated at low concentrations into Al (100 nm)/Fe(2)O(3) metastable intersitital composites (MIC) to form a hybrid organic/inorganic high-energy material. Studies of the dynamics of energy release were carried out by initiating the reaction photothermally with a single 8 ns pulse of the 1064 nm fundamental of a Nd:YAG laser. The reaction dynamics were measured using time-resolved spectroscopy of the light emitted from the deflagrating material. Two parameters were measured: the time to initiation and the duration of the deflagration. The presence of small amounts of PETN (16 mg/g of MIC) results in a dramatic decrease in the initiation time. This is attributed to a contribution to the temperature of the reacting system from the combustion of the PETN that, at lower loadings, appears to follow an Arrhenius dependence. The presence of PETN was also found to reduce the energy density required for single-pulse photothermal initiation by an order of magnitude, suggesting that hybrid materials such as this may be engineered to optimize their use as an efficient photodetonation medium.

  18. Fabrication of metal-organic frameworks and graphite oxide hybrid composites for solid-phase extraction and preconcentration of luteolin.

    PubMed

    Wang, Yang; Wu, Yichun; Ge, Huali; Chen, Huanhuan; Ye, Guiqin; Hu, Xiaoya

    2014-05-01

    A novel solid-phase extraction sorbent, metal-organic frameworks and graphite oxide hybrid composite, was prepared by a solvothermal technique. The morphology and properties of the resultant material were examined by Fourier transform infrared spectroscopy, X-ray diffraction and field emission scanning electron microscopy. To evaluate the extraction performance of the resultant sorbent, luteolin was chosen as a model analyte. The extraction conditions were optimized. Based on these, a convenient and efficient solid-phase extraction procedure for the determination of luteolin was established and the subsequent quantification step was performed by square wave anodic stripping voltammetry. Under the optimal conditions, the oxidation current increased linearly with increasing the concentration of luteolin in the range of 5.0 × 10(-9)-5.0 × 10(-7)molL(-1) with a correlation coefficient of 0.9983 and a detection limit of 7.9 × 10(-10)molL(-1). The relative standard deviation of seven successive scans was 4.20% for 5.0 × 10(-8)molL(-1) luteolin. This work not only proposes a useful method for sample pretreatment, but also reveals the great potential of metal-organic frameworks based hybrid materials as an excellent sorbent in solid-phase extraction.

  19. Monoclinic Hydroxyapatite Nanoplates Hybrid Composite with Improved Compressive Strength, and Porosity for Bone Defect Repair: Biomimetic Synthesis and Characterization.

    PubMed

    Xue, Bo; Farghaly, Ahmed A; Guo, Zhenzhao; Zhao, Pengg; Li, Hong; Zhou, Changren; Li, Lihua

    2016-03-01

    Calcium phosphate cement (CPC) has been used for bone restoration despite its intrinsic fragile property. In order to enhance the CPC mechanical properties, biopolymers were introduced as filler to prepare CPC based cements. Chitosan/tetracalcium phosphate (TTCP)/dicalcium phosphate anhydrous (DCPA) based cement for bone repair has been prepared in the study. Solidification of the prepared cement was carried out in a simulate body fluid at 37 degrees C. The introduction of chitosan improved the mechanical performance of the as-prepared CPC hybrid nanocomposite. FTIR, SEM, TEM, HRTEM, XRD, and SAED were used to characterize the CPC nanocomposite. Data simulations have been performed to assist in determining the crystalline phase/s in the CPC hybrid nanocomposite. Based on the SAED, HRTEM measurements and data simulations, a monoclinic phase of hydroxyapatite (HAP) with a plate-like structure was obtained in the CPC system, which is believed to be responsible for the observed enhancement in CPC mechanical properties. The obtained composite has a biocompatibility comparable to that of commercial sample. PMID:27455626

  20. Input Files and Procedures for Analysis of SMA Hybrid Composite Beams in MSC.Nastran and ABAQUS

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.; Patel, Hemant D.

    2005-01-01

    A thermoelastic constitutive model for shape memory alloys (SMAs) and SMA hybrid composites (SMAHCs) was recently implemented in the commercial codes MSC.Nastran and ABAQUS. The model is implemented and supported within the core of the commercial codes, so no user subroutines or external calculations are necessary. The model and resulting structural analysis has been previously demonstrated and experimentally verified for thermoelastic, vibration and acoustic, and structural shape control applications. The commercial implementations are described in related documents cited in the references, where various results are also shown that validate the commercial implementations relative to a research code. This paper is a companion to those documents in that it provides additional detail on the actual input files and solution procedures and serves as a repository for ASCII text versions of the input files necessary for duplication of the available results.

  1. Fabrication of single/multi-walled hybrid buckypaper composites and their enhancement of electromagnetic interference shielding performance

    NASA Astrophysics Data System (ADS)

    Lu, Shaowei; Shao, Junyan; Ma, Keming; Wang, Xiaoqiang; Zhang, Lu; Meng, Qingshi

    2016-11-01

    Multi-walled carbon nanotubes and single-walled carbon nanotubes show great potential for the application as an electromagnetic interference shielding material. In this paper, the electromagnetic interference shielding the effectiveness of a composite surface coated single/multi-walled carbon nanotube hybrid buckypaper was measured, which showed an average shielding effectiveness of ~55 dB with a buckypaper thickness of 50 µm, and bukypaper density of 0.76 g cm‑3, it is much higher than other carbon nanotube/resin materials when sample thickness is on the similar order. The structural, specific surface area and conductivity of the buckypapers were examined by field-emission scanning electron microscopy, specific surface area analyzer and four probes resistance tester, respectively.

  2. Tree age-dependent changes in photosynthetic and respiratory CO2 exchange in leaves of micropropagated diploid, triploid and hybrid aspen.

    PubMed

    Pärnik, Tiit; Ivanova, Hiie; Keerberg, Olav; Vardja, Rael; Niinemets, Ulo

    2014-06-01

    The growth rate of triploid European aspen (Populus tremula L.) and hybrid aspen (P. tremula × Populus tremuloides Michx.) significantly exceeds that of diploid aspen, but the underlying physiological controls of the superior growth rates of these genotypes are not known. We tested the hypothesis that the superior growth rate of triploid and hybrid aspen reflects their greater net photosynthesis rate. Micropropagated clonal plants varying in age from 2.5 to 19 months were used to investigate the ploidy and plant age interaction. The quantum yield of net CO2 fixation (Φ) in leaves of young 2.5-month-old hybrid aspen was lower than that of diploid and triploid trees. However, Φ in 19-month-old hybrid aspen was equal to that in triploid aspen and higher than that in diploid aspen. Φ and the rate of light-saturated net photosynthesis (ANS) increased with plant age, largely due to higher leaf dry mass per unit area in older plants. ANS in leaves of 19-month-old trees was highest in hybrid, medium in triploid and lowest in diploid aspen. Light-saturated photosynthesis had a broad temperature optimum between 20 and 35 °C. Rate of respiration in the dark (RDS) did not vary among the genotypes in 2.5-month-old plants, and the shape of the temperature response was also similar. RDS increased with plant age, but RDS was still not significantly different among the leaves of 19-month-old diploid and triploid aspen, but it was significantly lower in leaves of 19-month-old hybrid plants. The initial differences in the growth of plants with different ploidy were minor up to the age of 19 months, but during the next 2 years, the growth rate of hybrid aspen exceeded that of triploid plants by 2.7 times and of diploid plants by five times, in line with differences in ANS of 19-month-old plants of these species. It is suggested that differences in photosynthesis and growth became more pronounced with tree aging, indicating that ontogeny plays a key role in the expression of

  3. Facile synthesis of hybrid CNTs/NiCo2S4 composite for high performance supercapacitors

    PubMed Central

    Li, Delong; Gong, Youning; Pan, Chunxu

    2016-01-01

    In this work, a novel carbon nanotubes (CNTs)/NiCo2S4 composite for high performance supercapacitors was prepared via a simple chemical bath deposition combined with a post-anion exchange reaction. The morphologies and phase structures of the composites were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS) and low-temperature sorption of nitrogen (BET). The electro-chemical tests revealed that the CNT/NiCo2S4 composite exhibited high electrochemical performance, because the CNTs were used as a conductive network for the NiCo2S4 hexagonal nanoplates. Compared with pure NiCo2S4 and the mechanically mixed CNTs/NiCo2S4 composite, the CNTs/NiCo2S4 composite electrode material exhibited excellent supercapacitive performance, such as a high specific capacitance up to 1537 F/g (discharge current density of 1 A/g) and an outstanding rate capability of 78.1% retention as the discharge current density increased to 100 A/g. It is therefore expected to be a promising alternative material in the area of energy storage. PMID:27406239

  4. Facile synthesis of hybrid CNTs/NiCo2S4 composite for high performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Li, Delong; Gong, Youning; Pan, Chunxu

    2016-07-01

    In this work, a novel carbon nanotubes (CNTs)/NiCo2S4 composite for high performance supercapacitors was prepared via a simple chemical bath deposition combined with a post-anion exchange reaction. The morphologies and phase structures of the composites were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS) and low-temperature sorption of nitrogen (BET). The electro-chemical tests revealed that the CNT/NiCo2S4 composite exhibited high electrochemical performance, because the CNTs were used as a conductive network for the NiCo2S4 hexagonal nanoplates. Compared with pure NiCo2S4 and the mechanically mixed CNTs/NiCo2S4 composite, the CNTs/NiCo2S4 composite electrode material exhibited excellent supercapacitive performance, such as a high specific capacitance up to 1537 F/g (discharge current density of 1 A/g) and an outstanding rate capability of 78.1% retention as the discharge current density increased to 100 A/g. It is therefore expected to be a promising alternative material in the area of energy storage.

  5. Facile synthesis of hybrid CNTs/NiCo2S4 composite for high performance supercapacitors.

    PubMed

    Li, Delong; Gong, Youning; Pan, Chunxu

    2016-01-01

    In this work, a novel carbon nanotubes (CNTs)/NiCo2S4 composite for high performance supercapacitors was prepared via a simple chemical bath deposition combined with a post-anion exchange reaction. The morphologies and phase structures of the composites were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS) and low-temperature sorption of nitrogen (BET). The electro-chemical tests revealed that the CNT/NiCo2S4 composite exhibited high electrochemical performance, because the CNTs were used as a conductive network for the NiCo2S4 hexagonal nanoplates. Compared with pure NiCo2S4 and the mechanically mixed CNTs/NiCo2S4 composite, the CNTs/NiCo2S4 composite electrode material exhibited excellent supercapacitive performance, such as a high specific capacitance up to 1537 F/g (discharge current density of 1 A/g) and an outstanding rate capability of 78.1% retention as the discharge current density increased to 100 A/g. It is therefore expected to be a promising alternative material in the area of energy storage. PMID:27406239

  6. Macroscopic Mechanical Characterization of SMAs Fiber-Reinforced Hybrid Composite Under Uniaxial Loading

    NASA Astrophysics Data System (ADS)

    Lei, Hongshuai; Wang, Zhenqing; Tong, Liyong; Tang, Xiaojun

    2013-10-01

    This paper presents an experimental and theoretical investigation on the macroscopic mechanical behavior of shape memory alloys (SMAs) fiber-reinforced glass/resin composite subject to uniaxial loading at ambient temperature. A series of unidirectional SMAs reinforced composite laminates is fabricated through vacuum-assisted resin injection. Scanning electron microscopy is conducted to evaluate the interfacial cohesive quality between SMAs fiber and matrix. A theoretical model is proposed based on the SMAs phase transformation model and rule of mixture. Uniaxial tensile tests are performed to study the effects of weak interface and SMAs fiber volume fraction on the effective modulus of composite. Failure morphology of composite is discussed based on the observation using digital HF microscope. Due to the effects of phase transformation and weak interface, the overall stiffness of SMAs composite at the second stage is on average 10% lower than theoretical results. The rupture elongation of experimental result is approximately 13% higher than theoretical result. The local interfacial debonding between SMAs fiber and glass/resin matrix is the main failure mode.

  7. A hybrid Brownian Dynamics model for yielding, aging, and rejuvenation in deforming polymeric glasses

    NASA Astrophysics Data System (ADS)

    Zou, Weizhong; Larson, Ronald

    2015-03-01

    We describe the rheology of polymeric glasses by combining a simple constitutive equation for the fast segmental modes, borrowed from Fielding, et al., with Brownian dynamics (BD) simulations of the slow polymer modes. The BD simulations determine the polymeric stress from ensembles of finitely extensible bead-spring chains, where the bead drag coefficient is governed by solutions to the equation for segmental relaxation. Thus the model treats the short glassy segmental mode as ``solvent'' for the polymer modes. With rubbery modulus for the slow-relaxing polymer modes as one of our model parameters, stress-dependent relaxation, physical aging, flow rejuvenation as well as strain-hardening and recovery can be successfully accounted for in uniaxial extension and steady shear, without the use of an artificial ``crinkle factor'' used to account for recoil dynamics in previous work. Our simulation results remarkably agree with the experimental data from Lee et al. A comparison between our model and the barrier-hopping theory is also made. The authors acknowledge discussions with M. E. Cates and S. M. Fielding.

  8. Radio frequency shielding behaviour of silane treated Fe2O3/E-glass fibre reinforced epoxy hybrid composite

    NASA Astrophysics Data System (ADS)

    Arun prakash, V. R.; Rajadurai, A.

    2016-10-01

    In this work, radio frequency shielding behaviour of polymer (epoxy) matrixes composed of E-glass fibres and Fe2O3 fillers have been studied. The principal aim of this project is to prepare suitable shielding material for RFID application. When RFID unit is pasted on a metal plate without shielding material, the sensing distance is reduced, resulting in a less than useful RFID system. To improve RF shielding of epoxy, fibres and fillers were utilized. Magnetic behaviour of epoxy polymer composites was measured by hysteresis graphs (B-H) followed by radio frequency identifier setup. Fe2O3 particles of sizes 800, 200 and 100 nm and E-glass fibre woven mat of 600 g/m2 were used to make composites. Particle sizes of 800 nm and 200 nm were prepared by high-energy ball milling, whereas particles of 100 nm were prepared by sol-gel method. To enhance better dispersion of particles within the epoxy matrix, a surface modification process was carried out on fillers by an amino functional coupling agent called 3-Aminopropyltrimethoxysilane (APTMS). Crystalline and functional groups of siliconized Fe2O3 particles were characterized by XRD and FTIR spectroscopy analysis. Variable quantity of E-glass fibre (25, 35, and 45 vol%) was laid down along with 0.5 and 1.0 vol% of 800, 200, and 100 nm size Fe2O3 particles into the matrix, to fabricate the hybrid composites. Scanning electron microscopy and transmission electron microscopy images reveal the shape and size of Fe2O3 particles for different milling times and particle dispersion in the epoxy matrix. The maximum improved sensing distance of 45.2, 39.4 and 43.5 % was observed for low-, high-, and ultra-high radio frequency identifier setup along with shielding composite consist of epoxy, 1 vol% 200 nm Fe2O3 particles and 45 vol% of E-glass fibre.

  9. Hybrid freeform TIR optics construction in Cartesian coordinate system: a new composite ray mapping method

    NASA Astrophysics Data System (ADS)

    Ma, Donglin; Feng, Zexin; Wang, Chengliang; Liang, Rongguang

    2015-09-01

    In this paper, we propose a new composite ray mapping method to design freeform total internal reflective (TIR) optics for LED illumination. We sample the ray intensity distribution into rectangular grids which have the best topological match to those rectangular grids on the target surface. With the multiple-to-one mapping relationships between the source intensity distribution and target irradiance distribution, we can construct the freeform TIR surfaces and freeform refractive surface using Snell's law. Compared to our previous design using uv-θϕ composite ray mapping method, this design approach is expected to have much less surface error and improve the illumination uniformity further because of the better topological match. In addition, due to the overlapping mechanism by multiple-to-one (composite) ray mapping, the method could lead to a more robust freeform optics compared to traditional freeform optics designs.

  10. Interlaminar Fracture toughness in Glass-Cellulose Reinforced Epoxy hybrid composites

    NASA Astrophysics Data System (ADS)

    Uppin, Vinayak S.; Ashok; AnanthJoshi; Sridhar, I.; Shivakumar Gouda, P. S.

    2016-09-01

    Laminates of fibre reinforced compositesare weak in through thicknessbut strong in fibre direction, this lead to development of hybridizationconcept in polymer composites. In this work a new method of disperssing cellulose micro particleson unidirectional (UD) Glass fibre epoxy composite using semi-automated draw down coating technique was adopted to enhance fracture toughness.Test results show that by adding cellulose increases the load carrying competency by 32% in mode-I as compare to Glass- Epoxy composite samples. Imrovement in interlaminar critical energy release rates (GiC and GnC) up to 55% in Mode -I and 19 %in Mode -II respectively was also observed. This enahancement in fracture toughnees is due to the amount of fiber bridging seen during crack initiation and propagation.

  11. A mass reduction effort of the electric and hybrid vehicle. [composite door panels

    NASA Technical Reports Server (NTRS)

    Freeman, R. B.; Jahnle, H. A.

    1980-01-01

    Weight reduction, cost competitiveness, and elimination of the intrusion beam resulted from the redesign and fabrication using composite materials of the door outer panel and intrusion beam from a Chevrolet Impala. The basis of the redesign involved replacing these two steel parts with a single compression molding using the unique approach of simultaneously curing a sheet molding compound outside panel with a continuous glass fiber intrusion strap. A weight reduction of nearly 11 pounds per door was achieved. Additional weight savings are possible by taking advantage of the elimination of the intrusion beam to design thinner door structures. The parts consolidation approach allows the composite structure to be cost competitive with the original steel design for both the lower production car models and for the near to midterm production vehicles using current state of the art composite production techniques. The design, prototype fabrication, costing, material, properties and compression molding production requirements are discussed.

  12. Compositional assessments of key maize populations: B73 hybrids of the nested association mapping founder lines and diverse landrace inbred lines

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The present study provides an assessment of compositional diversity in maize B73 hybrids derived from both the nested association mapping (NAM) founder lines and from a geographically diverse collection of landrace accessions from North and South America. The NAM founders represent a key population...

  13. Preparation of Pt Ag alloy nanoisland/graphene hybrid composites and its high stability and catalytic activity in methanol electro-oxidation

    PubMed Central

    2011-01-01

    In this article, PtAg alloy nanoislands/graphene hybrid composites were prepared based on the self-organization of Au@PtAg nanorods on graphene sheets. Graphite oxides (GO) were prepared and separated to individual sheets using Hummer's method. Graphene nano-sheets were prepared by chemical reduction with hydrazine. The prepared PtAg alloy nanomaterial and the hybrid composites with graphene were characterized by SEM, TEM, and zeta potential measurements. It is confirmed that the prepared Au@PtAg alloy nanorods/graphene hybrid composites own good catalytic function for methanol electro-oxidation by cyclic voltammograms measurements, and exhibited higher catalytic activity and more stability than pure Au@Pt nanorods and Au@AgPt alloy nanorods. In conclusion, the prepared PtAg alloy nanoislands/graphene hybrid composites own high stability and catalytic activity in methanol electro-oxidation, so that it is one kind of high-performance catalyst, and has great potential in applications such as methanol fuel cells in near future. PMID:21982417

  14. Preparation of Pt Ag alloy nanoisland/graphene hybrid composites and its high stability and catalytic activity in methanol electro-oxidation.

    PubMed

    Feng, Lili; Gao, Guo; Huang, Peng; Wang, Xiansong; Zhang, Chunlei; Zhang, Jiali; Guo, Shouwu; Cui, Daxiang

    2011-01-01

    In this article, PtAg alloy nanoislands/graphene hybrid composites were prepared based on the self-organization of Au@PtAg nanorods on graphene sheets. Graphite oxides (GO) were prepared and separated to individual sheets using Hummer's method. Graphene nano-sheets were prepared by chemical reduction with hydrazine. The prepared PtAg alloy nanomaterial and the hybrid composites with graphene were characterized by SEM, TEM, and zeta potential measurements. It is confirmed that the prepared Au@PtAg alloy nanorods/graphene hybrid composites own good catalytic function for methanol electro-oxidation by cyclic voltammograms measurements, and exhibited higher catalytic activity and more stability than pure Au@Pt nanorods and Au@AgPt alloy nanorods. In conclusion, the prepared PtAg alloy nanoislands/graphene hybrid composites own high stability and catalytic activity in methanol electro-oxidation, so that it is one kind of high-performance catalyst, and has great potential in applications such as methanol fuel cells in near future. PMID:21982417

  15. Preparation of Pt Ag alloy nanoisland/graphene hybrid composites and its high stability and catalytic activity in methanol electro-oxidation

    NASA Astrophysics Data System (ADS)

    Feng, Lili; Gao, Guo; Huang, Peng; Wang, Xiansong; Zhang, Chunlei; Zhang, Jiali; Guo, Shouwu; Cui, Daxiang

    2011-10-01

    In this article, PtAg alloy nanoislands/graphene hybrid composites were prepared based on the self-organization of Au@PtAg nanorods on graphene sheets. Graphite oxides (GO) were prepared and separated to individual sheets using Hummer's method. Graphene nano-sheets were prepared by chemical reduction with hydrazine. The prepared PtAg alloy nanomaterial and the hybrid composites with graphene were characterized by SEM, TEM, and zeta potential measurements. It is confirmed that the prepared Au@PtAg alloy nanorods/graphene hybrid composites own good catalytic function for methanol electro-oxidation by cyclic voltammograms measurements, and exhibited higher catalytic activity and more stability than pure Au@Pt nanorods and Au@AgPt alloy nanorods. In conclusion, the prepared PtAg alloy nanoislands/graphene hybrid composites own high stability and catalytic activity in methanol electro-oxidation, so that it is one kind of high-performance catalyst, and has great potential in applications such as methanol fuel cells in near future.

  16. Novel polymer and inorganic/organic hybrid composite materials for proton exchange membrane applications

    NASA Astrophysics Data System (ADS)

    Yang, Zhiwei

    In this study, various novel proton exchange membranes (PEM) have been synthesized and investigated for high temperature PEM applications. Sulfonic acid functionalized polysilsesquioxane hybrid membranes with the empirical formula of R-Si-(O)1.5 consist of a highly cross-linked Si-O backbone and pendant organic side chain R, which is terminated in a proton conducting functional group (i.e., sulfonic acid). The membranes exhibited excellent proton conductivities (sigma) of >10-2 S/cm under low humidity conditions and a wide range of temperatures. The fuel cell (FC) performance of the membranes under low humidity conditions has been evaluated. Acid-doped linear meta-polyaniline membranes have been prepared through solution casting of m-PANI. The obtained membrane shows good proton conductivities at temperatures above 100°C, achieving 10-2.7 S/cm under 120°C and practically no humidity conditions. The effects of doping acids, doping levels and humidity on the conductivity are discussed. Polyethylenimine (PEI)/SiO2 nanocomposites membranes have been synthesized through sol-gel processes. The introduction of SiO2 clusters into high molecule weight, linear PEI greatly improved its thermal stability at high temperatures and O2 atmosphere. During the sol-gel processes, trifluoromethanesulfonimide (HTFSI) was added to dope the amine groups of PEI and form immobilized proton-conducting ionic liquids, which provide the hybrid membranes with proton-conducting behavior. The resultant membranes show good proton conductivities at high temperatures and low to zero humidity conditions. The effects of temperature, humidity and mobility of active groups on the conductivity are discussed. Various organic amine/HTFSI ionic group functionalized polysilsesquioxane hybrid membranes have been prepared. The Si-O backbone provides excellent thermal/chemical/mechanical properties and the HTFSI-doped amine end groups provide the proton conducting properties. The membranes exhibited proton

  17. A hybrid method for damage detection and quantification in advanced X-COR composite structures

    NASA Astrophysics Data System (ADS)

    Neerukatti, Rajesh Kumar; Rajadas, Abhishek; Borkowski, Luke; Chattopadhyay, Aditi; Huff, Daniel W.

    2016-04-01

    Advanced composite structures, such as foam core carbon fiber reinforced polymer composites, are increasingly being used in applications which require high strength, high in-plane and flexural stiffness, and low weight. However, the presence of in situ damage due to manufacturing defects and/or service conditions can complicate the failure mechanisms and compromise their strength and reliability. In this paper, the capability of detecting damages such as delaminations and foam-core separations in X-COR composite structures using non-destructive evaluation (NDE) and structural health monitoring (SHM) techniques is investigated. Two NDE techniques, flash thermography and low frequency ultrasonics, were used to detect and quantify the damage size and locations. Macro fiber composites (MFCs) were used as actuators and sensors to study the interaction of Lamb waves with delaminations and foam-core separations. The results indicate that both flash thermography and low frequency ultrasonics were capable of detecting damage in X-COR sandwich structures, although low frequency ultrasonic methods were capable of detecting through thickness damages more accurately than flash thermography. It was also observed that the presence of foam-core separations significantly changes the wave behavior when compared to delamination, which complicates the use of wave based SHM techniques. Further, a wave propagation model was developed to model the wave interaction with damages at different locations on the X-COR sandwich plate.

  18. Hybrid boron nitride-natural fiber composites for enhanced thermal conductivity

    NASA Astrophysics Data System (ADS)

    Xia, Changlei; Garcia, Andres C.; Shi, Sheldon Q.; Qiu, Ying; Warner, Nathaniel; Wu, Yingji; Cai, Liping; Rizvi, Hussain R.; D’Souza, Nandika A.; Nie, Xu

    2016-10-01

    Thermal conductivity was dramatically increased after adding natural fiber into hexagonal boron nitride (hBN)/epoxy composites. Although natural fiber does not show high-thermal conductivity itself, this study found that the synergy of natural fiber with hBN could significantly improve thermal conductivity, compared with that solely using hBN. A design of mixtures approach using constant fibers with increasing volume fractions of hBN was examined and compared. The thermal conductivity of the composite containing 43.6% hBN, 26.3% kenaf fiber and 30.1% epoxy reached 6.418 W m‑1 K‑1, which was 72.3% higher than that (3.600 W m‑1 K‑1) of the 69.0% hBN and 31.0% epoxy composite. Using the scanning electron microscope (SEM) and micro computed tomography (micro-CT), it was observed that the hBN powders were well distributed and ordered on the fiber surfaces enhancing the ceramic filler’s interconnection, which may be the reason for the increase in thermal conductivity. Additionally, the results from mechanical and dynamic mechanical tests showed that performances dramatically improved after adding kenaf fibers into the hBN/epoxy composite, potentially benefiting the composite’s use as an engineered material.

  19. Hybrid boron nitride-natural fiber composites for enhanced thermal conductivity

    PubMed Central

    Xia, Changlei; Garcia, Andres C.; Shi, Sheldon Q.; Qiu, Ying; Warner, Nathaniel; Wu, Yingji; Cai, Liping; Rizvi, Hussain R.; D’Souza, Nandika A.; Nie, Xu

    2016-01-01

    Thermal conductivity was dramatically increased after adding natural fiber into hexagonal boron nitride (hBN)/epoxy composites. Although natural fiber does not show high-thermal conductivity itself, this study found that the synergy of natural fiber with hBN could significantly improve thermal conductivity, compared with that solely using hBN. A design of mixtures approach using constant fibers with increasing volume fractions of hBN was examined and compared. The thermal conductivity of the composite containing 43.6% hBN, 26.3% kenaf fiber and 30.1% epoxy reached 6.418 W m−1 K−1, which was 72.3% higher than that (3.600 W m−1 K−1) of the 69.0% hBN and 31.0% epoxy composite. Using the scanning electron microscope (SEM) and micro computed tomography (micro-CT), it was observed that the hBN powders were well distributed and ordered on the fiber surfaces enhancing the ceramic filler’s interconnection, which may be the reason for the increase in thermal conductivity. Additionally, the results from mechanical and dynamic mechanical tests showed that performances dramatically improved after adding kenaf fibers into the hBN/epoxy composite, potentially benefiting the composite’s use as an engineered material. PMID:27703226

  20. Hybrid Zinc Oxide Nanorods/Carbon Nanotubes Composite for Nitrogen Dioxide Gas Sensing

    NASA Astrophysics Data System (ADS)

    Oweis, Rami J.; Albiss, B. A.; Al-Widyan, M. I.; Al-Akhras, M.-Ali

    2014-09-01

    This study reports on the synthesis and fabrication of hybrid nanocomposite based on single-walled carbon nanotubes-ZnO nanorods (SWCNT-ZnONR) as resistive gas sensors for NO2 detection. The sensor was prepared using the standard simple and cost-effective hydrothermal process. The sensor was characterized by x-ray diffraction (XRD) and scanning electron microscopy. The findings revealed enhanced porous SWCNT-ZnONR nanocomposites due to the high porosity of the SWCNT. It was also found that the sensor exhibited average response and recovery times of about 70 s and 100 s, respectively. The XRD peak at 26° indicated that the SWCNT pattern was not disturbed, while sensitivity increased with temperature up to 150°C, at which the sensitivity was maximum. Similarly, the sensor sensitivity increased with NO2 concentration at all levels examined. Moreover, the results indicate that the sensor shows significant promise for NO2 gas sensing applications.

  1. Physical aging and its influence on the reliability of network epoxies and epoxy-matrix composites

    NASA Technical Reports Server (NTRS)

    Heinemann, K.

    1983-01-01

    The matrix-dominated physical and mechanical properties of a carbon fiber reinforced epoxy composite and a neat epoxy resin were found to be affected by sub-Tg annealing in nitrogen and dark atmosphere. Postcured specimens of Thornel 300 carbon-fiber/Fiberite 934 epoxy as well as Fiberite 934 epoxy resin were quenched from above Tg and given annealing at 140 C, 110 C, or 80 C, for time up to one-hundred thousand minutes. No weight loss was observed during annealing at these temperatures. Significant variations were found in density, modulus, hardness, damping, moisture absorption ability, thermal expansivity. Moisture-epoxy interactious were also studied. The kinetics of aging as well as the molecular aggregation during this densification process were monitored by differential scanning calorimetry, dynamic mechanical analysis, density gradient column, microhardness tester, Instron, and solid-state nuclear magnetic resonance spectroscopy.

  2. Aging results for PRD 49 III/epoxy and Kevlar 49/epoxy composite pressure vessels

    NASA Technical Reports Server (NTRS)

    Hamstad, M. A.

    1983-01-01

    Kevlar 49/epoxy composite is growing in use as a structural material because of its high strength-to-weight ratio. Currently, it is used for the Trident rocket motor case and for various pressure vessels on the Space Shuttle. In 1979, the initial results for aging of filament-wound cylindrical pressure vessels which were manufactured with preproduction Kevlar 49 (Hamstad, 1979) were published. This preproduction fiber was called PRD 49 III. This report updates the continuing study to 10-year data and also presents 7.5-year data for spherical pressure vessels wound with production Kevlar 49. For completeness, this report will again describe the specimens of the original study with PRD 49 as well as specimens for the new study with Kevlar 49.

  3. Ultrasensitive electrochemical detection of DNA hybridization using Au/Fe3O4 magnetic composites combined with silver enhancement.

    PubMed

    Bai, Yu-Hui; Li, Jin-Yi; Xu, Jing-Juan; Chen, Hong-Yuan

    2010-07-01

    A novel method is described for the highly effective amplifying electrochemical response of DNA based on oligonucleotides functionalized with Au/Fe(3)O(4) nanocomposites by the aid of silver (Ag) enhancement. Via electrostatic layer-by-layer (LBL) assembly, the prepared Fe(3)O(4) nanoparticles form nano-clusters coated with a bilayer composed of polystyrene sulfonate sodium salt (PSS) and poly(diallyldimethylammonium chloride) (PDDA), which are in favor of adsorbing lots of gold nanoparticles (AuNPs) on the surface. The application of magnetic Fe(3)O(4) made the procedures much more simple, convenient and feasible. The resulting composites were then used as labels via the Au-S bond for the DNA hybridization, followed by catalytic deposition of silver on the gold tags. Such an assay is then combined with a sensitive anodic stripping voltammetry (ASV) measurement of multiple silver nanoparticle tracers. A 27-mer sequence DNA target is detected at a glassy carbon (GC) electrode with a detection limit down to ca. 100 aM, which is 800 times lower than that obtained using gold nanoparticles only as labels in the control experiments. This Fe(3)O(4)/PSS/PDDA/Au composite offers a great promising future for the ultrasensitive detection of other biorecognition events.

  4. Mixed-hybrid and vertex-discontinuous-Galerkin finite element modeling of multiphase compositional flow on 3D unstructured grids

    NASA Astrophysics Data System (ADS)

    Moortgat, Joachim; Firoozabadi, Abbas

    2016-06-01

    Problems of interest in hydrogeology and hydrocarbon resources involve complex heterogeneous geological formations. Such domains are most accurately represented in reservoir simulations by unstructured computational grids. Finite element methods accurately describe flow on unstructured meshes with complex geometries, and their flexible formulation allows implementation on different grid types. In this work, we consider for the first time the challenging problem of fully compositional three-phase flow in 3D unstructured grids, discretized by any combination of tetrahedra, prisms, and hexahedra. We employ a mass conserving mixed hybrid finite element (MHFE) method to solve for the pressure and flux fields. The transport equations are approximated with a higher-order vertex-based discontinuous Galerkin (DG) discretization. We show that this approach outperforms a face-based implementation of the same polynomial order. These methods are well suited for heterogeneous and fractured reservoirs, because they provide globally continuous pressure and flux fields, while allowing for sharp discontinuities in compositions and saturations. The higher-order accuracy improves the modeling of strongly non-linear flow, such as gravitational and viscous fingering. We review the literature on unstructured reservoir simulation models, and present many examples that consider gravity depletion, water flooding, and gas injection in oil saturated reservoirs. We study convergence rates, mesh sensitivity, and demonstrate the wide applicability of our chosen finite element methods for challenging multiphase flow problems in geometrically complex subsurface media.

  5. Large-area electrochromic coatings: Composites of polyaniline and polyacrylate-silica hybrid sol-gel materials

    SciTech Connect

    Jang, G.W.; Chen, C.; Gumbs, R.W.; Wei, Y.; Yeh, J.M.

    1996-08-01

    A low-cost technique for fabricating large-area electrochromic coatings is described. Polyaniline was incorporated into polyacrylate-silica hybrid sol-gel networks using suspended particles or solutions. A solution of polyaniline and poly[methyl methacrylate-co-3-(trimethoxysilyl)propyl methacrylate] can be spray- or brush-coated on transparent indium-tin oxide substrates to form robust electrochromic coatings. Silane functional groups on the polyacrylate chain act as coupling and cross-linking agents to improve surface adhesion and mechanical properties of the resulting composite coatings. These coatings showed reversible transparent to green color change when polarized at potentials between {minus}0.4 and +0.4 V vs. Ag/AgCl in a 0.2 M LiClO{sub 4}/acetonitrile electrolyte solution. The cycle lifetimes of polyaniline films were improved by incorporating the polymer in the polyacrylate-silica matrix. Electrochromic switching was demonstrated for the composite coatings in large-area all-solid-state devices.

  6. Formation and aging of secondary organic aerosol from toluene: changes in chemical composition, volatility, and hygroscopicity

    DOE PAGES

    Hildebrandt Ruiz, L.; Paciga, A. L.; Cerully, K. M.; Nenes, A.; Donahue, N. M.; Pandis, S. N.

    2015-07-24

    Secondary organic aerosol (SOA) is transformed after its initial formation, but this chemical aging of SOA is poorly understood. Experiments were conducted in the Carnegie Mellon environmental chamber to form secondary organic aerosol (SOA) from the photo-oxidation of toluene and other small aromatic volatile organic compounds (VOCs) in the presence of NOx under different oxidizing conditions. The effects of the oxidizing condition on organic aerosol (OA) composition, mass yield, volatility, and hygroscopicity were explored. Higher exposure to the hydroxyl radical resulted in different OA composition, average carbon oxidation state (OSc), and mass yield. The OA oxidation state generally increased duringmore » photo-oxidation, and the final OA OSc ranged from -0.29 to 0.16 in the performed experiments. The volatility of OA formed in these different experiments varied by as much as a factor of 30, demonstrating that the OA formed under different oxidizing conditions can have a significantly different saturation concentration. There was no clear correlation between hygroscopicity and oxidation state for this relatively hygroscopic SOA.« less

  7. Formation and aging of secondary organic aerosol from toluene: changes in chemical composition, volatility, and hygroscopicity

    NASA Astrophysics Data System (ADS)

    Hildebrandt Ruiz, L.; Paciga, A. L.; Cerully, K. M.; Nenes, A.; Donahue, N. M.; Pandis, S. N.

    2015-07-01

    Secondary organic aerosol (SOA) is transformed after its initial formation, but this chemical aging of SOA is poorly understood. Experiments were conducted in the Carnegie Mellon environmental chamber to form secondary organic aerosol (SOA) from the photo-oxidation of toluene and other small aromatic volatile organic compounds (VOCs) in the presence of NOx under different oxidizing conditions. The effects of the oxidizing condition on organic aerosol (OA) composition, mass yield, volatility, and hygroscopicity were explored. Higher exposure to the hydroxyl radical resulted in different OA composition, average carbon oxidation state (OSc), and mass yield. The OA oxidation state generally increased during photo-oxidation, and the final OA OSc ranged from -0.29 to 0.16 in the performed experiments. The volatility of OA formed in these different experiments varied by as much as a factor of 30, demonstrating that the OA formed under different oxidizing conditions can have a significantly different saturation concentration. There was no clear correlation between hygroscopicity and oxidation state for this relatively hygroscopic SOA.

  8. The Effects of Age on the Yield and Composition of the Essential Oils of Calendula officinalis

    NASA Astrophysics Data System (ADS)

    Okoh, O. O.; Sadimenko, A. A.; Afolayan, A. J.

    The variations in the yield and composition of the essential oils from Calendula officinalis L. (Asteraceae) cultivated in Alice, Eastern Cape of South Africa are reported. Essential oils of this plant were obtained by hydrodistillation using the Clevenger apparatus and analysis was performed by GC-MS. The yield in essential oil showed a maximum at the full flowering stage (0.97%) and a minimum during the pre-flowering stage (0.13%). The compositions also showed different patterns at different phases of the vegetative cycle. Sesquiterpenes (α-cadinene, α-cadinol, T-muurolol and epi-bicyclosesquiphellandrene) and monoterpenes (limonene, 1, 8-cineole and trans-β-ocimene) showed the highest correlations with the age of the plant. Aiming the use of essential oil as a food ingredient, the most interesting stage is the post-flowering period, the essential oil at this time being rich in α-cadinene, α-cadinol, t-muurolol, limonene, 1,8-cineole, with P-cymene present at lower levels. α-cadinene is an important flavouring agent in baked foods, candy and chewing gum and also used as a fragrance in cosmetics and detergents. T-muurolol and α-cadinol are important antimicrobial agents.

  9. Accelerated Aging Experiments for Prognostics of Damage Growth in Composite Materials

    NASA Technical Reports Server (NTRS)

    Saxena, Abhinav; Goebel, Kai Frank; Larrosa, Cecilia C.; Janapati, Vishnuvardhan; Roy, Surajit; Chang, Fu-Kuo

    2011-01-01

    Composite structures are gaining importance for use in the aerospace industry. Compared to metallic structures their behavior is less well understood. This lack of understanding may pose constraints on their use. One possible way to deal with some of the risks associated with potential failure is to perform in-situ monitoring to detect precursors of failures. Prognostic algorithms can be used to predict impending failures. They require large amounts of training data to build and tune damage model for making useful predictions. One of the key aspects is to get confirmatory feedback from data as damage progresses. These kinds of data are rarely available from actual systems. The next possible resource to collect such data is an accelerated aging platform. To that end this paper describes a fatigue cycling experiment with the goal to stress carbon-carbon composite coupons with various layups. Piezoelectric disc sensors were used to periodically interrogate the system. Analysis showed distinct differences in the signatures of growing failures between data collected at conditions. Periodic X-radiographs were taken to assess the damage ground truth. Results after signal processing showed clear trends of damage growth that were correlated to damage assessed from the X-ray images.

  10. Lipid composition of the Antarctic fish Pleuragramma antarcticum. Influence of age class

    NASA Astrophysics Data System (ADS)

    Mayzaud, P.; Chevallier, J.; Tavernier, E.; Moteki, M.; Koubbi, P.

    2011-08-01

    Larvae and juvenile stages of Pleuragramma antarcticum have been collected in the Dumont D’Urville Sea (East Antarctica) during summer 2008 on board the TRV Umitaka Maru during the CEAMARC survey. Detailed analyses of their lipid class and fatty acid compositions were carried out. P. antarcticum showed a pronounced ontogenic lipid accumulation with increasing size. Larvae displayed a dominance of polar lipids (83% of total lipids) and low percentage of triglycerides (7%). Conversely juveniles showed an increasing accumulation of triglycerides (up to 72.4%). The fatty acid composition of polar lipids remained rather stable between stages with 22:6n-3 and 20:5n-3 as dominant contributors. The relatively minor ontogenic changes, e.g. increase of monounsaturated and decrease of C18 polyunsaturated fatty acids, may reflect the influence of differences in diet. Triglycerides showed that all three age classes are well segregated in term of fatty acid composition. Larvae triglycerides are characterized by significant percentages of 16:0, 20:5n-3, 20:6n-3 and to a minor extent 18:4n-3, which suggest a prymnesiophyte based diet. Juveniles are characterized by larger percentages of C20:1 and C22:1 acids, considered as markers of Calanus type copepods. The increasing contribution of 18:1n-9 in the triglycerides of the older juveniles suggests a gradual and increasing shift from a copepod dominant diet to an euphausiid dominant diet. Fatty acid trophic markers pattern suggests a shift from a phytophagous and omnivorous diet for larvae to a carnivorous diet for juveniles.

  11. Hybrid organic-inorganic composites for applications in Vis-NIR photodiodes

    NASA Astrophysics Data System (ADS)

    Luszczynska, Beata; Szymanski, Marek Z.

    2015-10-01

    Active layers of bulk heterojunction are extensively studied because of their great potential for application in low-cost optoelectronic devices like photovoiltaic cells and photodiodes. The performance of such devices is strongly influenced by the formed nanostructures which determine the transport ability of the organic composite. We investigated the charge carrier transport properties of two organic composites: poly(3-hexyothiophene) (P3HT) with (6,6)-phenyl-C60-butyric acid methyl ester (60PCBM)and poly(triarylamine) (PTTA) blended with 60PCBM. The optimised organic blend was used as a matrix material for Cu-In-Se nanocrystals. Adding Cu-In-Se nanocrystals to a P3HT/60PCBM bulk heterojunction leads to a significant improvement of the maximum external quantum efficiency of the investigated system from 48% to 70% (at wavelength 520 nm).

  12. Using crystal ages and compositions to evaluate the generation of rhyolite at Tarawera, New Zealand

    NASA Astrophysics Data System (ADS)

    Klemetti, E.; Cooper, K.

    2008-12-01

    melting of a granitic mush/protolith to the point where all of the plagioclase melts while preserving zircon in the liquid or (2) preferential segregation of liquid with entrained zircon while leaving major phases behind as crystal residue; both processes would be followed by new crystallization of major phases. We suggest that mechanism (2) is more likely to have produced the rhyolite magma at Tarawera. This is supported by simple batch melting models of a silicic crystal mush (plagioclase, quartz, amphibole, biotite and orthopyroxene) to determine the state of zircon saturation during the melting. These models suggest that during melt production by heating a crystal mush network (initial Zr content of 90 ppm), pre-existing zircons will become unstable after ~70% melt is produced even at temperatures as low as ~750°C, leaving ~30% residue of major phases crystals in the melt. This residual plagioclase is more than can be accounted for in the 226Ra-230Th-238U plagioclase age data, unless the crystal mush was itself produced very recently (<10 ka). Not only does this model (suggested previously by Bachmann et al., 2004 based solely on geochemical constraints) allow for young major phases and a larger age range of trace phases, it also could help explain the overall dioritic composition of plutons as rhyolitic liquids (with their zircon) are extracted from crystal mush networks and erupted.

  13. Age-related changes in intramuscular and subcutaneous fat content and fatty acid composition in growing pigs using longitudinal data.

    PubMed

    Bosch, L; Tor, M; Reixach, J; Estany, J

    2012-07-01

    The evolution of intramuscular fat (IMF) and subcutaneous backfat (SB) content and fatty acid composition with age was investigated. A repeated sampling scheme (n=517) for longissimus dorsi (LM) and SB specimens was performed from 160 to 220 days on 216 purebred Duroc barrows. IMF content increased linearly with age at a rate of 0.05%/day, with major compositional changes occurring in C18:1 and C18.2, which increased and decreased by around 4%, respectively. Backfat thickness increase rate declined with age, showing similar compositional changes to IMF but halved in magnitude. Fat content itself also influenced fat composition. At a fixed age, both saturated (SFA) (C16:0) and monounsaturated (MUFA) (C18:1) increased with IMF but only SFA (C16:0 and C18:0) with SB. Aging mostly affected MUFA while fatness SFA. A delay in age at slaughter will enhance IMF and C18:1 in relation to overall fatness but at expense of decreasing body and loin growth rate.

  14. Development of hybrid braided composite rods for reinforcement and health monitoring of structures.

    PubMed

    Rana, Sohel; Zdraveva, Emilija; Pereira, Cristiana; Fangueiro, Raul; Correia, A Gomes

    2014-01-01

    In the present study, core-reinforced braided composite rods (BCRs) were developed and characterized for strain sensing capability. A mixture of carbon and glass fibre was used in the core, which was surrounded by a braided cover of polyester fibres. Three compositions of core with different carbon fibre/glass fibre weight ratios (23/77, 47/53, and 100/0) were studied to find out the optimum composition for both strain sensitivity and mechanical performance. The influence of carbon fibre positioning in BCR cross-section on the strain sensing behaviour was also investigated. Strain sensing property of BCRs was characterized by measuring the change in electrical resistance with flexural strain. It was observed that BCRs exhibited increase (positive response) or decrease (negative response) in electrical resistance depending on carbon fibre positioning. The BCR with lowest amount of carbon fibre was found to give the best strain sensitivity as well as the highest tensile strength and breaking extension. The developed BCRs showed reversible strain sensing behaviour under cyclic flexural loading with a maximum gauge factor of 23.4 at very low strain level (0.55%). Concrete beams reinforced with the optimum BCR (23/77) also exhibited strain sensing under cyclic flexural strain, although the piezoresistive behaviour in this case was irreversible.

  15. Development of Hybrid Braided Composite Rods for Reinforcement and Health Monitoring of Structures

    PubMed Central

    Zdraveva, Emilija; Pereira, Cristiana; Fangueiro, Raul; Correia, A. Gomes

    2014-01-01

    In the present study, core-reinforced braided composite rods (BCRs) were developed and characterized for strain sensing capability. A mixture of carbon and glass fibre was used in the core, which was surrounded by a braided cover of polyester fibres. Three compositions of core with different carbon fibre/glass fibre weight ratios (23/77, 47/53, and 100/0) were studied to find out the optimum composition for both strain sensitivity and mechanical performance. The influence of carbon fibre positioning in BCR cross-section on the strain sensing behaviour was also investigated. Strain sensing property of BCRs was characterized by measuring the change in electrical resistance with flexural strain. It was observed that BCRs exhibited increase (positive response) or decrease (negative response) in electrical resistance depending on carbon fibre positioning. The BCR with lowest amount of carbon fibre was found to give the best strain sensitivity as well as the highest tensile strength and breaking extension. The developed BCRs showed reversible strain sensing behaviour under cyclic flexural loading with a maximum gauge factor of 23.4 at very low strain level (0.55%). Concrete beams reinforced with the optimum BCR (23/77) also exhibited strain sensing under cyclic flexural strain, although the piezoresistive behaviour in this case was irreversible. PMID:24574867

  16. Effect of age and diet composition on activity of pancreatic enzymes in birds.

    PubMed

    Brzęk, Paweł; Ciminari, M Eugenia; Kohl, Kevin D; Lessner, Krista; Karasov, William H; Caviedes-Vidal, Enrique

    2013-07-01

    Digestive enzymes produced by the pancreas and intestinal epithelium cooperate closely during food hydrolysis. Therefore, activities of pancreatic and intestinal enzymes processing the same substrate can be hypothesized to change together in unison, as well as to be adjusted to the concentration of their substrate in the diet. However, our knowledge of ontogenetic and diet-related changes in the digestive enzymes of birds is limited mainly to intestinal enzymes; it is largely unknown whether they are accompanied by changes in activities of enzymes produced by the pancreas. Here, we analyzed age- and diet-related changes in activities of pancreatic enzymes in five passerine and galloanserine species, and compared them with simultaneous changes in activities of intestinal enzymes. Mass-specific activity of pancreatic amylase increased with age in young house sparrows but not in zebra finches, in agreement with changes in typical dietary starch content and activity of intestinal maltase. However, we found little evidence for the presence of adaptive, diet-related modulation of pancreatic enzymes in both passerine and galloanserine species, even though in several cases the same birds adaptively modulated activities of their intestinal enzymes. In general, diet-related changes in mass-specific activities of pancreatic and intestinal enzymes were not correlated. We conclude that activity of pancreatic enzymes in birds is under strong genetic control, which enables evolutionary adjustment to typical diet composition but is less adept for short term, diet-related flexibility.

  17. Development and Characterization of SiC)/ MoSi2-Si3N4(p) Hybrid Composites

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G.

    1998-01-01

    Intermetallic compound MoSi2 has long been known as a high temperature material that has excellent oxidation resistance and electrical/thermal conductivity. Also its low cost, high melting point (2023 C), relatively low density (6.2 g/cu cm versus 9 g/cu cm for current engine materials), and ease of machining, make it an attractive structural material. However, the use of MoSi2 has been hindered due to its poor toughness at low temperatures, poor creep resistance at high temperatures, and accelerated oxidation (also known as 'pest' oxidation) at temperatures between approximately 450 and 550 C. Continuous fiber reinforcing is very effective means of improving both toughness and strength. Unfortunately, MoSi2 has a relatively high coefficient of thermal expansion (CTE) compared to potential reinforcing fibers such as SiC. The large CTE mismatch between the fiber and the matrix resulted in severe matrix cracking during thermal cycling. Addition of about 30 to 50 vol % of Si3N4 particulate to MoSi2 improved resistance to low temperature accelerated oxidation by forming a Si2ON2 protective scale and thereby eliminating catastrophic 'pest failure'. The Si3N4 addition also improved the high temperature creep strength by nearly five orders of magnitude, doubled the room temperature toughness and significantly lowered the CTE of the MoSi2 and eliminated matrix cracking in SCS-6 reinforced composites even after thermal cycling. The SCS-6 fiber reinforcement improved the room temperature fracture toughness by seven times and impact resistance by five times. The composite exhibited excellent strength and toughness improvement up to 1400 C. More recently, tape casting was adopted as the preferred processing of MoSi2-base composites for improved fiber spacing, ability to use small diameter fibers, and for lower cost. Good strength and toughness values were also obtained with fine diameter Hi-Nicalon tow fibers. This hybrid composite remains competitive with ceramic matrix

  18. Aging Versus Postmenopausal Osteoporosis: Bone Composition and Maturation Kinetics at Actively-Forming Trabecular Surfaces of Female Subjects Aged 1 to 84 Years.

    PubMed

    Paschalis, Eleftherios P; Fratzl, Peter; Gamsjaeger, Sonja; Hassler, Norbert; Brozek, Wolfgang; Eriksen, Erik F; Rauch, Frank; Glorieux, Francis H; Shane, Elizabeth; Dempster, David; Cohen, Adi; Recker, Robert; Klaushofer, Klaus

    2016-02-01

    Bone strength depends on the amount of bone, typically expressed as bone mineral density (BMD), determined by dual-energy X-ray absorptiometry (DXA), and on bone quality. Bone quality is a multifactorial entity including bone structural and material compositional properties. The purpose of the present study was to examine whether bone material composition properties at actively-forming trabecular bone surfaces in health are dependent on subject age, and to contrast them with postmenopausal osteoporosis patients. To achieve this, we analyzed by Raman microspectroscopy iliac crest biopsy samples from healthy subjects aged 1.5 to 45.7 years, paired biopsy samples from females before and immediately after menopause aged 46.7 to 53.6 years, and biopsy samples from placebo-treated postmenopausal osteoporotic patients aged 66 to 84 years. The monitored parameters were as follows: the mineral/matrix ratio; the mineral maturity/crystallinity (MMC); nanoporosity; the glycosaminoglycan (GAG) content; the lipid content; and the pyridinoline (Pyd) content. The results indicate that these bone quality parameters in healthy, actively-forming trabecular bone surfaces are dependent on subject age at constant tissue age, suggesting that with advancing age the kinetics of maturation (either accumulation, or posttranslational modifications, or both) change. For most parameters, the extrapolation of models fitted to the individual age dependence of bone in healthy individuals was in rough agreement with their values in postmenopausal osteoporotic patients, except for MMC, lipid, and Pyd content. Among these three, Pyd content showed the greatest deviation between healthy aging and disease, highlighting its potential to be used as a discriminating factor.

  19. Lamb wave characterization of the effects of long-term thermal-mechanical aging on composite stiffness

    NASA Technical Reports Server (NTRS)

    Seale, M. D.; Madaras, E. I.

    1999-01-01

    Lamb waves offer a promising method of evaluating damage in composite materials. The Lamb wave velocity is directly related to the material parameters, so an effective tool exists to monitor damage in composites by measuring the velocity of these waves. The Lamb Wave Imager (LWI) uses a pulse/receive technique that excites an antisymmetric Lamb mode and measures the time-of-flight over a wide frequency range. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the dispersion curve. In this study, the time-of-flight as well as the elastic stiffnesses D11, D22, A44, and A55 for composite samples which have undergone combined thermal and mechanical aging are obtained. The samples examined include a baseline specimen with 0 cycles, specimens which have been aged 2350 and 3530 cycles at high strain levels, and one specimen aged 3530 cycles at low strain levels.

  20. Lamb wave characterization of the effects of long-term thermal-mechanical aging on composite stiffness.

    PubMed

    Seale, M D; Madaras, E I

    1999-09-01

    Lamb waves offer a promising method of evaluating damage in composite materials. The Lamb wave velocity is directly related to the material parameters, so an effective tool exists to monitor damage in composites by measuring the velocity of these waves. The Lamb Wave Imager (LWI) uses a pulse/receive technique that excites an antisymmetric Lamb mode and measures the time-of-flight over a wide frequency range. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the dispersion curve. In this study, the time-of-flight as well as the elastic stiffnesses D11, D22, A44, and A55 for composite samples which have undergone combined thermal and mechanical aging are obtained. The samples examined include a baseline specimen with 0 cycles, specimens which have been aged 2350 and 3530 cycles at high strain levels, and one specimen aged 3530 cycles at low strain levels.