Science.gov

Sample records for sandwich construction

  1. Sandwich Construction Solar Structural Facets

    SciTech Connect

    Diver, R. B.; Grossman, J.W.

    1998-12-22

    Silver/glass mirrors have excellent optical properties but need a method of support in order to be used in concentrating solar thermal systems. In collaboration with the Cummins dish/Stirling development program, they started investigating sandwich construction as a way to integrate silver/glass mirrors into solar optical elements. In sandwich construction, membranes such as sheet metal or plastic are bonded to the front and back of a core (like a sandwich). For solar optical elements, a glass mirror is bonded to one of the membranes. This type of construction has the advantages of a high strength-to-weight ratio, and reasonable material and manufacturing cost. The inherent stiffness of sandwich construction mirror panels also facilitates large panels. This can have cost advantages for both the amount of hardware required as well as reduced installation and alignment costs. In addition, by incorporating the panels into the support structure reductions in the amount of structural support required are potentially possible.

  2. Sandwich construction solar structural facets

    SciTech Connect

    Diver, R.B.; Grossman, J.W.

    1999-07-01

    Silver/glass mirrors have excellent optical properties but need a method of support in order to be used in concentrating solar thermal systems. In collaboration with the Cummins dish/Stirling development program, the authors started investigating sandwich construction as a way to integrate silver/glass mirrors into solar optical elements. In sandwich construction, membranes such as sheet metal or plastic are bonded to the front and back of a core (like a sandwich). For solar optical elements, a glass mirror is bonded to one of the membranes. This type of construction has the advantages of a high strength-to-weight ratio, and reasonable material and manufacturing cost. The inherent stiffness of sandwich construction mirror panels also facilitates large panels. This can have cost advantages for both the amount of hardware required as well as reduced installation and alignment costs. In addition, by incorporating the panels into the support structure reductions in the amount of structural support required are potentially possible. The authors have investigated sandwich construction panels that employ cores of polystyrene, polyvinyl chloride (PVC) and polyurethane foams as well as conventional aluminum and cardboard honeycombs. The authors investigations have involved fabricating 0.5 x 0.6-m (20 x 24-inch) spherical-contour panels and testing their optical properties and environmental durability. The authors have also performed preliminary cost and performance studies. Evaluations included optical testing with the SunLab 2f and VSHOT tools both before and after exposures to environmental chamber testing. The results showed that sandwich mirror panels are potentially very accurate. However, long-term degradation due to creep was evident in all of the foam core facets. The aluminum honeycomb core facets were accurate and durable. In this paper, the design principles that guided the investigations, estimates of cost, and the results of the experimental investigations are

  3. Impulsive Loading of Cellular Media in Sandwich Construction

    NASA Astrophysics Data System (ADS)

    Main, Joseph A.; Gazonas, George A.

    2006-07-01

    Motivated by recent efforts to mitigate blast loading using energy-absorbing materials, this paper investigates the uniaxial crushing of cellular media in sandwich construction under impulsive pressure loading. The cellular core is modeled using a rigid, perfectly-plastic, locking idealization, as in previous studies, and the front and back faces are modeled as rigid, with pressure loading applied to the front face and the back face unrestrained. Predictions of this analytical model show excellent agreement with explicit finite element computations, and the model is used to investigate the influence of the mass distribution between the core and the faces. Increasing the mass fraction in the front face is found to increase the impulse required for complete crushing of the cellular core but also to produce undesirable increases in back-face accelerations. Optimal mass distributions are investigated by maximizing the impulse capacity while limiting the back-face accelerations to a specified level.

  4. Flexural and impact properties of sandwich panels used in surfboard construction

    SciTech Connect

    Manning, J.A.; Crosky, A.G.; Bandyopadhyay, S.

    1993-12-31

    Surfboards represent a particularly simple example of sandwich panel construction and are conventionally made from a preshaped low density polyurethane foam core encased in an E-glass/polyester skin. They are made to minimum weight and thickness and as a result suffer durability problems. The boards are particularly prone to denting due to impact damage, causing principally cosmetic problems. More importantly, they frequently snap under normal service conditions. Recently, there has been considerable interest in the use of higher performance materials for the skins, notably S-glass and epoxy resin, to improve the durability of surfboards. This work examines the failure of simple parallel faced panels fabricated to simulate a section of a surfboard. It is shown that when loaded in four point bending, the panels fail by compression of the core and that this mode of failure produces the same characteristics as seen in service failures. Further, the flexural strength is dominated by the behavior of the core and is not improved appreciably by the use of S-glass or epoxy resin. On the other hand, the impact resistance is improved by the use of S-glass and further improved if epoxy resin is used as the matrix.

  5. Highly efficient construction of oriented sandwich structures for surface-enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Guo, Hongyun; Xu, Weiqing; Zhou, Ji; Xu, Shuping; Lombardi, John R.

    2013-02-01

    The purpose of this study is to solve the problem of low achievement in fabricating sandwich surface-enhanced Raman scattering (SERS) substrates. We demonstrated a highly efficient sandwich structure by the oriented assembly of metal nanoparticles (NPs) on a periodic hexagonal array of metal nanoprisms with 1,4-benzenedithiol (1,4-BDT) as linkers. The metal nanoprism array was prepared by vacuum deposition of metal on a close-packed polystyrene nanosphere pre-patterned substrate. The metal nanoprism array presents different surface properties from the pits left from the removal of polystyrene nanospheres, which causes linkers to selectively adsorb on the metal nanoprism array and sequentially leads to the oriented immobilization of the second-layer metal NPs, avoiding mismatched orientation. These sandwich SERS substrates were characterized by extinction spectroscopy and atomic force microscopy and their enhancement activity was evaluated under different excitation wavelengths. The sandwich structure greatly increases the achievement of ‘hot spots’ to almost 100% of all the metal nanoprisms and enables a large amplification of SERS signals by a factor of ten. This method has the advantages of simplicity, high efficiency, high throughput, controllability and high reproducibility. It has significance in both the study of SERS substrates and the development of plasmonic devices.

  6. A nano-sandwich construct built with graphene nanosheets and carbon nanotubes enhances mechanical properties of hydroxyapatite-polyetheretherketone scaffolds.

    PubMed

    Feng, Pei; Peng, Shuping; Wu, Ping; Gao, Chengde; Huang, Wei; Deng, Youwen; Xiao, Tao; Shuai, Cijun

    2016-01-01

    A nano-sandwich construct was built by combining two-dimensional graphene nanosheets (GNSs) and one-dimensional carbon nanotubes (CNTs) to improve the mechanical properties of hydroxyapatite-polyetheretherketone (HAP-PEEK) scaffolds for bone tissue engineering. In this nano-sandwich construct, the long tubular CNTs penetrated the interlayers of graphene and prevented their aggregation, increasing the effective contact area between the construct and matrix. The combination of GNSs and CNTs in a weight ratio of 2:8 facilitated the dispersion of each other and provided a synergetic effect in enhancing the mechanical properties. The compressive strength and modulus of the scaffolds were increased by 63.58% and 56.54% at this time compared with those of HAP-PEEK scaffolds, respectively. The carbon-based fillers, pulling out and bridging, were also clearly observed in the matrix. Moreover, the dangling of CNTs and their entangling with GNSs further reinforced the mechanical properties. Furthermore, apatite layer formed on the scaffold surface after immersing in simulated body fluid, and the cells attached and spread well on the surface of the scaffolds and displayed good viability, proliferation, and differentiation. These evidence indicate that the HAP-PEEK scaffolds enhanced by GNSs and CNTs are a promising alternative for bone tissue engineering. PMID:27555770

  7. A nano-sandwich construct built with graphene nanosheets and carbon nanotubes enhances mechanical properties of hydroxyapatite-polyetheretherketone scaffolds.

    PubMed

    Feng, Pei; Peng, Shuping; Wu, Ping; Gao, Chengde; Huang, Wei; Deng, Youwen; Xiao, Tao; Shuai, Cijun

    2016-01-01

    A nano-sandwich construct was built by combining two-dimensional graphene nanosheets (GNSs) and one-dimensional carbon nanotubes (CNTs) to improve the mechanical properties of hydroxyapatite-polyetheretherketone (HAP-PEEK) scaffolds for bone tissue engineering. In this nano-sandwich construct, the long tubular CNTs penetrated the interlayers of graphene and prevented their aggregation, increasing the effective contact area between the construct and matrix. The combination of GNSs and CNTs in a weight ratio of 2:8 facilitated the dispersion of each other and provided a synergetic effect in enhancing the mechanical properties. The compressive strength and modulus of the scaffolds were increased by 63.58% and 56.54% at this time compared with those of HAP-PEEK scaffolds, respectively. The carbon-based fillers, pulling out and bridging, were also clearly observed in the matrix. Moreover, the dangling of CNTs and their entangling with GNSs further reinforced the mechanical properties. Furthermore, apatite layer formed on the scaffold surface after immersing in simulated body fluid, and the cells attached and spread well on the surface of the scaffolds and displayed good viability, proliferation, and differentiation. These evidence indicate that the HAP-PEEK scaffolds enhanced by GNSs and CNTs are a promising alternative for bone tissue engineering.

  8. A nano-sandwich construct built with graphene nanosheets and carbon nanotubes enhances mechanical properties of hydroxyapatite–polyetheretherketone scaffolds

    PubMed Central

    Feng, Pei; Peng, Shuping; Wu, Ping; Gao, Chengde; Huang, Wei; Deng, Youwen; Xiao, Tao; Shuai, Cijun

    2016-01-01

    A nano-sandwich construct was built by combining two-dimensional graphene nanosheets (GNSs) and one-dimensional carbon nanotubes (CNTs) to improve the mechanical properties of hydroxyapatite–polyetheretherketone (HAP–PEEK) scaffolds for bone tissue engineering. In this nano-sandwich construct, the long tubular CNTs penetrated the interlayers of graphene and prevented their aggregation, increasing the effective contact area between the construct and matrix. The combination of GNSs and CNTs in a weight ratio of 2:8 facilitated the dispersion of each other and provided a synergetic effect in enhancing the mechanical properties. The compressive strength and modulus of the scaffolds were increased by 63.58% and 56.54% at this time compared with those of HAP–PEEK scaffolds, respectively. The carbon-based fillers, pulling out and bridging, were also clearly observed in the matrix. Moreover, the dangling of CNTs and their entangling with GNSs further reinforced the mechanical properties. Furthermore, apatite layer formed on the scaffold surface after immersing in simulated body fluid, and the cells attached and spread well on the surface of the scaffolds and displayed good viability, proliferation, and differentiation. These evidence indicate that the HAP–PEEK scaffolds enhanced by GNSs and CNTs are a promising alternative for bone tissue engineering. PMID:27555770

  9. Cross Cell Sandwich Core

    NASA Technical Reports Server (NTRS)

    Ford, Donald B. (Inventor)

    2004-01-01

    A sandwich core comprises two faceplates separated by a plurality of cells. The cells are comprised of walls positioned at oblique angles relative to a perpendicular axis extending through the faceplates. The walls preferably form open cells and are constructed from open cells and are constructed from rows of ribbons. The walls may be obliquely angled relative to more than one plane extending through the perpendicular axis.

  10. Transport and kinetics in sandwiched membrane bioreactors.

    PubMed

    Jeong, Y S; Vieth, W R; Matsuura, T

    1991-01-01

    A bioreactor in which living yeast cells are sandwiched between an ultrafiltration membrane and a reverse osmosis membrane was constructed, and experiments were performed for the conversion of substrate glucose to product ethanol. A set of equations that include both transport through a series of barrier layers and bioreaction rate were developed to predict the performance of the sandwich bioreactor. The above equations were solved by using numerical values for the transport parameter and the bioreaction rate constant, and the results are compared with the experimental data.

  11. Salads, Sandwiches and Desserts.

    ERIC Educational Resources Information Center

    Marine Corps Inst., Washington, DC.

    Developed as part of the Marine Corps Institute (MCI) correspondence training program, this course on salads, sandwiches, and desserts is designed to provide Marine food service personnel with a general background in the proper techniques for the preparation of these items. Introductory materials include specific information for MCI students and a…

  12. "If They're the Customer, I'm the Meat in the Sandwich": An Exploration of Tertiary Teachers' Metaphorical Constructions of Teaching

    ERIC Educational Resources Information Center

    Emerson, Lisa; Mansvelt, Juliana

    2014-01-01

    Metaphors are a primary influence on the way we perceive and construct our world; they are also a way of revealing beliefs and attitudes that might otherwise be difficult to identify. Furthermore, metaphor has been found to be an effective way of shifting people's beliefs, attitudes and behaviour. This paper details the findings of a pilot…

  13. Structural Analysis of Sandwich Foam Panels

    SciTech Connect

    Kosny, Jan; Huo, X. Sharon

    2010-04-01

    The Sandwich Panel Technologies including Structural Insulated Panels (SIPs) can be used to replace the conventional wooden-frame construction method. The main purpose of this Cooperative Research and Development Agreement (CRADA) between UT-Battelle, LLC and SGI Venture, Inc. was to design a novel high R-value type of metal sandwich panelized technology. This CRADA project report presents design concept discussion and numerical analysis results from thermal performance study of this new building envelope system. The main objective of this work was to develop a basic concept of a new generation of wall panel technologies which will have R-value over R-20 will use thermal mass to improve energy performance in cooling dominated climates and will be 100% termite resistant. The main advantages of using sandwich panels are as follows: (1) better energy saving structural panels with high and uniform overall wall R-value across the elevation that could not be achieved in traditional walls; and (2) reducing the use of raw materials or need for virgin lumber. For better utilization of these Sandwich panels, engineers need to have a thorough understanding of the actual performance of the panels and system. Detailed analysis and study on the capacities and deformation of individual panels and its assembly have to be performed to achieve that goal. The major project activity was to conduct structural analysis of the stresses, strains, load capacities, and deformations of individual sandwich components under various load cases. The analysis simulated the actual loading conditions of the regular residential building and used actual material properties of the steel facings and foam.

  14. HYBRID-SANDWICHED REINFORCEMENT WITH GEOSYNTHETICS

    NASA Astrophysics Data System (ADS)

    Yasuhara, Kazuya; Yamazaki, Shinji; Sakakibara, Tsutomu

    Advantageous aspects of sandwich-type reinforced earth structures combined with geosynthetics and sand mat are highlighted in this paper. Those aspects were elucidated by two kinds of laboratory tests : (1) large consolidation tests for improvement of hydraulic conductivity and (2) model footing tests on improvement of bearing capacity and deformation characteristics for reinforced earth structures, including both vertical permeability and horizontal transmissibility characteristics of geosynthetics results from both laboratory tests indicated the following: i) Hydraulic conductivity of geosynthetics used for this type of earth reinforcement can be maintained for a long period. Such conductivity sometimes disappears, particularly because of clogging when geosynthetics are adopted in embankment construction using fine-grained soils. This fact indicates that the sand mats which are laid above and beneath geosynthetics play a salient role in preventing clogging of geosynthetics that occurs by intrusion of fines from cohesive soils. ii) Sandwich-type reinforcement combined with geosynthetics and sand mats increases stability and decreases deformation of earth structures. In particular, the sandwich structure is effective for providing toughness, which has remained an important issue for reducing infrastructural maintenance and costs. In the later part of the paper, conventionally available stability analysis was carried out to propose the design procedure for reinforced earth structures and at the same time numerical analysis was also conducted to ensure the applicability of the hybrid-sandwiched earth reinforcement newly proposed in the current paper. Finally, based on the horizontal placement by means of HBS described in the current paper, the vertical drain procedure using the sandwich structures for accelerating consolidation and increasing stability of soft soils is also suggested for the future research and investigation.

  15. Facesheet Delamination of Composite Sandwich Materials at Cryogenic Temperatures

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.; Odegard, Gregory M.; Herring, Helen M.

    2003-01-01

    The next generation of space transportation vehicles will require advances in lightweight structural materials and related design concepts to meet the increased demands on performance. One potential source for significant structural weight reduction is the replacement of traditional metallic cryogenic fuel tanks with new designs for polymeric matrix composite tanks. These new tank designs may take the form of thin-walled sandwich constructed with lightweight core and composite facesheets. Life-time durability requirements imply the materials must safely carry pressure loads, external structural loads, resist leakage and operate over an extremely wide temperature range. Aside from catastrophic events like tank wall penetration, one of the most likely scenarios for failure of a tank wall of sandwich construction is the permeation of cryogenic fluid into the sandwich core and the subsequent delamination of the sandwich facesheet due to the build-up of excessive internal pressure. The research presented in this paper was undertaken to help understand this specific problem of core to facesheet delamination in cryogenic environments and relate this data to basic mechanical properties. The experimental results presented herein provide data on the strain energy release rate (toughness) of the interface between the facesheet and the core of a composite sandwich subjected to simulated internal pressure. A unique test apparatus and associated test methods are described and the results are presented to highlight the effects of cryogenic temperature on the measured material properties.

  16. Wire and Packing Tape Sandwiches

    ERIC Educational Resources Information Center

    Rabinowitz, Sandy

    2009-01-01

    In this article, the author describes how students can combine craft wire with clear packing tape to create a two-dimensional design that can be bent and twisted to create a three-dimensional form. Students sandwich wire designs between two layers of tape. (Contains 1 online resource.)

  17. High temperature structural sandwich panels

    NASA Astrophysics Data System (ADS)

    Papakonstantinou, Christos G.

    High strength composites are being used for making lightweight structural panels that are being employed in aerospace, naval and automotive structures. Recently, there is renewed interest in use of these panels. The major problem of most commercial available sandwich panels is the fire resistance. A recently developed inorganic matrix is investigated for use in cases where fire and high temperature resistance are necessary. The focus of this dissertation is the development of a fireproof composite structural system. Sandwich panels made with polysialate matrices have an excellent potential for use in applications where exposure to high temperatures or fire is a concern. Commercial available sandwich panels will soften and lose nearly all of their compressive strength temperatures lower than 400°C. This dissertation consists of the state of the art, the experimental investigation and the analytical modeling. The state of the art covers the performance of existing high temperature composites, sandwich panels and reinforced concrete beams strengthened with Fiber Reinforced Polymers (FRP). The experimental part consists of four major components: (i) Development of a fireproof syntactic foam with maximum specific strength, (ii) Development of a lightweight syntactic foam based on polystyrene spheres, (iii) Development of the composite system for the skins. The variables are the skin thickness, modulus of elasticity of skin and high temperature resistance, and (iv) Experimental evaluation of the flexural behavior of sandwich panels. Analytical modeling consists of a model for the flexural behavior of lightweight sandwich panels, and a model for deflection calculations of reinforced concrete beams strengthened with FRP subjected to fatigue loading. The experimental and analytical results show that sandwich panels made with polysialate matrices and ceramic spheres do not lose their load bearing capability during severe fire exposure, where temperatures reach several

  18. Development of biobased sandwich structures for mass transit application

    NASA Astrophysics Data System (ADS)

    Munusamy, Sethu Raaj

    Efforts to increase the biobased content in sandwich composites are being investigated to reduce the dependence on synthetically produced or mined, energy-intensive materials for numerous composite applications. Vegetable oil-based polyurethane foams are gaining recognition as good substitutes for synthetic counter parts while utilizing bast fiber to replace fiberglass is also gaining credence. In this study, soy oil-based polyurethane foam was evaluated as a core in a sandwich construction with facesheets of hybridized kenaf and E-glass fibers in a vinyl ester resin matrix to replace traditionally used plywood sheeting on steel frame for mass transit bus flooring systems. As a first step towards implementation, the static performance of the biobased foam was compared to 100% synthetic foam. Secondly, biobased sandwich structures were processed and their static performance was compared to plywood. The biobased sandwich composites designed and processed were shown to hold promise towards replacing plywood for bus flooring applications by displaying an increase of 130% for flexural strength and 135% for flexural modulus plus better indentation values.

  19. A general small-deflection theory for flat sandwich plates

    NASA Technical Reports Server (NTRS)

    Libove, Charles; Batdorf, S B

    1948-01-01

    A small-deflection theory is developed for the elastic behavior of orthotropic flat plates in which deflections due to shear are taken into account. In this theory, which covers all types of flat sandwich construction, a plate is characterized by seven physical constants (five stiffnesses and two Poisson ratios) of which six are independent. Both the energy expression and the differential equations are developed. Boundary conditions corresponding to simply supported, clamped, and elastically restrained edges are considered.

  20. Compressive strength after blast of sandwich composite materials

    PubMed Central

    Arora, H.; Kelly, M.; Worley, A.; Del Linz, P.; Fergusson, A.; Hooper, P. A.; Dear, J. P.

    2014-01-01

    Composite sandwich materials have yet to be widely adopted in the construction of naval vessels despite their excellent strength-to-weight ratio and low radar return. One barrier to their wider use is our limited understanding of their performance when subjected to air blast. This paper focuses on this problem and specifically the strength remaining after damage caused during an explosion. Carbon-fibre-reinforced polymer (CFRP) composite skins on a styrene–acrylonitrile (SAN) polymer closed-cell foam core are the primary composite system evaluated. Glass-fibre-reinforced polymer (GFRP) composite skins were also included for comparison in a comparable sandwich configuration. Full-scale blast experiments were conducted, where 1.6×1.3 m sized panels were subjected to blast of a Hopkinson–Cranz scaled distance of 3.02 m kg−1/3, 100 kg TNT equivalent at a stand-off distance of 14 m. This explosive blast represents a surface blast threat, where the shockwave propagates in air towards the naval vessel. Hopkinson was the first to investigate the characteristics of this explosive air-blast pulse (Hopkinson 1948 Proc. R. Soc. Lond. A 89, 411–413 (doi:10.1098/rspa.1914.0008)). Further analysis is provided on the performance of the CFRP sandwich panel relative to the GFRP sandwich panel when subjected to blast loading through use of high-speed speckle strain mapping. After the blast events, the residual compressive load-bearing capacity is investigated experimentally, using appropriate loading conditions that an in-service vessel may have to sustain. Residual strength testing is well established for post-impact ballistic assessment, but there has been less research performed on the residual strength of sandwich composites after blast. PMID:24711494

  1. Compressive strength after blast of sandwich composite materials.

    PubMed

    Arora, H; Kelly, M; Worley, A; Del Linz, P; Fergusson, A; Hooper, P A; Dear, J P

    2014-05-13

    Composite sandwich materials have yet to be widely adopted in the construction of naval vessels despite their excellent strength-to-weight ratio and low radar return. One barrier to their wider use is our limited understanding of their performance when subjected to air blast. This paper focuses on this problem and specifically the strength remaining after damage caused during an explosion. Carbon-fibre-reinforced polymer (CFRP) composite skins on a styrene-acrylonitrile (SAN) polymer closed-cell foam core are the primary composite system evaluated. Glass-fibre-reinforced polymer (GFRP) composite skins were also included for comparison in a comparable sandwich configuration. Full-scale blast experiments were conducted, where 1.6×1.3 m sized panels were subjected to blast of a Hopkinson-Cranz scaled distance of 3.02 m kg(-1/3), 100 kg TNT equivalent at a stand-off distance of 14 m. This explosive blast represents a surface blast threat, where the shockwave propagates in air towards the naval vessel. Hopkinson was the first to investigate the characteristics of this explosive air-blast pulse (Hopkinson 1948 Proc. R. Soc. Lond. A 89, 411-413 (doi:10.1098/rspa.1914.0008)). Further analysis is provided on the performance of the CFRP sandwich panel relative to the GFRP sandwich panel when subjected to blast loading through use of high-speed speckle strain mapping. After the blast events, the residual compressive load-bearing capacity is investigated experimentally, using appropriate loading conditions that an in-service vessel may have to sustain. Residual strength testing is well established for post-impact ballistic assessment, but there has been less research performed on the residual strength of sandwich composites after blast.

  2. Composite Sandwich Technologies Lighten Components

    NASA Technical Reports Server (NTRS)

    2010-01-01

    Leveraging its private resources with several Small Business Innovation Research (SBIR) contracts with both NASA and the U.S. Department of Defense, WebCore Technologies LLC, of Miamisburg, Ohio, developed a fiber-reinforced foam sandwich panel it calls TYCOR that can be used for a wide variety of industrial and consumer applications. Testing at Glenn Research Center?s Ballistic Impact Facility demonstrated that the technology was able to exhibit excellent damage localization and stiffness during impact. The patented and trademarked material has found use in many demanding applications, including marine, ground transportation, mobile shelters, bridges, and most notably, wind turbines.

  3. Facesheet Wrinkling in Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Ley, Robert P.; Lin, Weichuan; Mbanefo, Uy

    1999-01-01

    The purpose of this paper is to provide a concise summary of the state-of-the-art for the analysis of the facesheet wrinkling mode of failure in sandwich structures. This document is not an exhaustive review of the published research related to facesheet wrinkling. Instead, a smaller number of key papers are reviewed in order to provide designers and analysts with a working understanding of the state-of-the-art. Designers and analysts should use this survey to guide their judgement when deciding which one of a wide variety of available facesheet wrinkling design formulas is applicable to a specific design problem.

  4. Advanced robust design optimization of FRP sandwich floor panels

    NASA Astrophysics Data System (ADS)

    Awad, Z. K.; Gonzalez, F.; Aravinthan, T.

    2010-06-01

    FRP composite is now being used in the construction of main structural elements, such as the FRP sandwich panel for flooring system and bridges. The objective of this research is to use multi-objective optimization and robust design techniques to minimize the weight of the FRP sandwich floor panel design as well as maximizing the natural frequency. An Australian manufactures has invented a new FRP composite panel suitable for civil engineering constructions. This research work aims to develop an optimal design of structural fibre composite sandwich floor panel by coupling a Finite Element FE and robust design optimization method. The design variables are the skin plies thickness and the core thickness as a robust variable. Results indicate that there is a trade-off between the objectives. The robust design technique is used then to select a set of candidate geometry, which has a high natural frequency, low weight and low standard deviation. The design simulation was formulated by depending on the EUROCOMP standard design constraints.

  5. Development and Evaluation of Stitched Sandwich Panels

    NASA Technical Reports Server (NTRS)

    Stanley, Larry E.; Adams, Daniel O.; Reeder, James R. (Technical Monitor)

    2001-01-01

    This study explored the feasibility and potential benefits provided by the addition of through-the-thickness reinforcement to sandwich structures. Through-the-thickness stitching is proposed to increase the interlaminar strength and damage tolerance of composite sandwich structures. A low-cost, out-of-autoclave processing method was developed to produce composite sandwich panels with carbon fiber face sheets, a closed-cell foam core, and through-the-thickness Kevlar stitching. The sandwich panels were stitched in a dry preform state, vacuum bagged, and infiltrated using Vacuum Assisted Resin Transfer Molding (VARTM) processing. For comparison purposes, unstitched sandwich panels were produced using the same materials and manufacturing methodology. Test panels were produced initially at the University of Utah and later at NASA Langley Research Center. Four types of mechanical tests were performed: flexural testing, flatwise tensile testing, core shear testing, and edgewise compression testing. Drop-weight impact testing followed by specimen sectioning was performed to characterize the damage resistance of stitched sandwich panels. Compression after impact (CAI) testing was performed to evaluate the damage tolerance of the sandwich panels. Results show significant increases in the flexural stiffness and strength, out-of-plane tensile strength, core shear strength, edgewise compression strength, and compression-after-impact strength of stitched sandwich structures.

  6. Sound transmission loss of composite sandwich panels

    NASA Astrophysics Data System (ADS)

    Zhou, Ran

    Light composite sandwich panels are increasingly used in automobiles, ships and aircraft, because of the advantages they offer of high strength-to-weight ratios. However, the acoustical properties of these light and stiff structures can be less desirable than those of equivalent metal panels. These undesirable properties can lead to high interior noise levels. A number of researchers have studied the acoustical properties of honeycomb and foam sandwich panels. Not much work, however, has been carried out on foam-filled honeycomb sandwich panels. In this dissertation, governing equations for the forced vibration of asymmetric sandwich panels are developed. An analytical expression for modal densities of symmetric sandwich panels is derived from a sixth-order governing equation. A boundary element analysis model for the sound transmission loss of symmetric sandwich panels is proposed. Measurements of the modal density, total loss factor, radiation loss factor, and sound transmission loss of foam-filled honeycomb sandwich panels with different configurations and thicknesses are presented. Comparisons between the predicted sound transmission loss values obtained from wave impedance analysis, statistical energy analysis, boundary element analysis, and experimental values are presented. The wave impedance analysis model provides accurate predictions of sound transmission loss for the thin foam-filled honeycomb sandwich panels at frequencies above their first resonance frequencies. The predictions from the statistical energy analysis model are in better agreement with the experimental transmission loss values of the sandwich panels when the measured radiation loss factor values near coincidence are used instead of the theoretical values for single-layer panels. The proposed boundary element analysis model provides more accurate predictions of sound transmission loss for the thick foam-filled honeycomb sandwich panels than either the wave impedance analysis model or the

  7. Graphene-antenna sandwich photodetector.

    PubMed

    Fang, Zheyu; Liu, Zheng; Wang, Yumin; Ajayan, Pulickel M; Nordlander, Peter; Halas, Naomi J

    2012-07-11

    Nanoscale antennas sandwiched between two graphene monolayers yield a photodetector that efficiently converts visible and near-infrared photons into electrons with an 800% enhancement of the photocurrent relative to the antennaless graphene device. The antenna contributes to the photocurrent in two ways: by the transfer of hot electrons generated in the antenna structure upon plasmon decay, as well as by direct plasmon-enhanced excitation of intrinsic graphene electrons due to the antenna near field. This results in a graphene-based photodetector achieving up to 20% internal quantum efficiency in the visible and near-infrared regions of the spectrum. This device can serve as a model for merging the light-harvesting characteristics of optical frequency antennas with the highly attractive transport properties of graphene in new optoelectronic devices. PMID:22703522

  8. Properties of polyurethane foam/coconut coir fiber as a core material and as a sandwich composites component

    NASA Astrophysics Data System (ADS)

    Azmi, M. A.; Abdullah, H. Z.; Idris, M. I.

    2013-12-01

    This research focuses on the fabrication and characterization of sandwich composite panels using glass fiber composite skin and polyurethane foam reinforced coconut coir fiber core. The main objectives are to characterize the physical and mechanical properties and to elucidate the effect of coconut coir fibers in polyurethane foam cores and sandwich composite panels. Coconut coir fibers were used as reinforcement in polyurethane foams in which later were applied as the core in sandwich composites ranged from 5 wt% to 20 wt%. The physical and mechanical properties found to be significant at 5 wt% coconut coir fiber in polyurethane foam cores as well as in sandwich composites. It was found that composites properties serve better in sandwich composites construction.

  9. Feedback sandwiches affect perceptions but not performance.

    PubMed

    Parkes, Jay; Abercrombie, Sara; McCarty, Teresita

    2013-08-01

    The feedback sandwich technique-make positive comments; provide critique; end with positive comments-is commonly recommended to feedback givers despite scant evidence of its efficacy. These two studies (N = 20; N = 350) of written peer feedback with third-year medical students on clinical patient note-writing assignments indicate that students think feedback sandwiches positively impact subsequent performance when there is no evidence that they do. The effort necessary to produce feedback sandwiches and students' unwarranted confidence in their performance impact have implications for teaching about how to give feedback.

  10. Fiber Composite Sandwich Thermostructural Behavior - Computational Simulation

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.; Aiello, Robert A.; Murthy, Pappu L. N.

    1988-01-01

    Four computational simulation methods with different levels of sophistication were used to simulate thermal behavior and structural changes of composite sandwich panels with a honeycomb core subjected to a variety of environmental effects. The models on thich these methods are based include three-dimensional finite-element modeling, three-dimensional finite-element modeling assuming a homogeneous core, laminate theory, and simple equations for predicting the equivalent properties of the honeycomb core. A procedure was developed and embedded in a composite mechanics computer code, which made it possile to conduct parametric studies to determine 'optimum' composite sandwich configurations for specific applications. The procedure was applied for the evaluation of composite sandwich behavior at the global, local, laminate, ply, and micromechanics levels when the composite sandwich is subjected to hygral, thermal, and mechanical loading environments.

  11. Precast concrete sandwich panels subjected to impact loading

    NASA Astrophysics Data System (ADS)

    Runge, Matthew W.

    Precast concrete sandwich panels are a relatively new product in the construction industry. The design of these panels incorporates properties that allow for great resilience against temperature fluctuation as well as the very rapid and precise construction of facilities. The concrete sandwich panels investigated in this study represent the second generation of an ongoing research and development project. This second generation of panels have been engineered to construct midsized commercial buildings up to three stories in height as well as residential dwellings. The panels consist of a double-tee structural wythe, a foam core and a fascia wythe, joined by shear connectors. Structures constructed from these panels may be subjected to extreme loading including the effects of seismic and blast loading in addition to wind. The aim of this work was to investigate the behaviour of this particular sandwich panel when subjected to structural impact events. The experimental program consisted of fourteen concrete sandwich panels, five of which were considered full-sized specimens (2700 mm X 1200mm X 270 mm) and nine half-sized specimens (2700mm X 600mm X 270 mm) The panels were subjected to impact loads from a pendulum impact hammer where the total energy applied to the panels was varied by changing the mass of the hammer. The applied loads, displacements, accelerations, and strains at the mid-span of the panel as well as the reaction point forces were monitored during the impact. The behaviour of the panels was determined primarily from the experimental results. The applied loads at low energy levels that caused little to no residual deflection as well as the applied loads at high energy levels that represent catastrophic events and thus caused immediate failure were determined from an impact on the structural and the fascia wythes. Applied loads at intermediate energy levels representing extreme events were also used to determine whether or not the panels could withstand

  12. Experimental study of acoustical characteristics of honeycomb sandwich structures

    NASA Astrophysics Data System (ADS)

    Peters, Portia Renee

    Loss factor measurements were performed on sandwich panels to determine the effects of different skin and core materials on the acoustical properties. Results revealed inserting a viscoelastic material in the core's mid-plane resulted in the highest loss factor. Panels constructed with carbon-fiber skins exhibited larger loss factors than glass-fiber skins. Panels designed to achieve subsonic wave speed did not show a significant increase in loss factor above the coincidence frequency. The para-aramid core had a larger loss factor value than the meta-aramid core. Acoustic absorption coefficients were measured for honeycomb sandwiches designed to incorporate multiple sound-absorbing devices, including Helmholtz resonators and porous absorbers. The structures consisted of conventional honeycomb cores filled with closed-cell polyurethane foams of various densities and covered with perforated composite facesheets. Honeycomb cores filled with higher density foam resulted in higher absorption coefficients over the frequency range of 50 -- 1250 Hz. However, this trend was not observed at frequencies greater than 1250 Hz, where the honeycomb filled with the highest density foam yielded the lowest absorption coefficient among samples with foam-filled cores. The energy-recycling semi-active vibration suppression method (ERSA) was employed to determine the relationship between vibration suppression and acoustic damping for a honeycomb sandwich panel. Results indicated the ERSA method simultaneously reduced the sound transmitted through the panel and the panel vibration. The largest reduction in sound transmitted through the panel was 14.3% when the vibrations of the panel were reduced by 7.3%. The influence of different design parameters, such as core density, core material, and cell size on wave speeds of honeycomb sandwich structures was experimentally analyzed. Bending and shear wave speeds were measured and related to the transmission loss performance for various material

  13. Piezoelectrically-induced guided wave propagation for health monitoring of honeycomb sandwich structures

    NASA Astrophysics Data System (ADS)

    Song, Fei

    Honeycomb sandwich structures have been widely used in marine and aerospace applications due to their high strength/stiffness-to-weight ratio. However, an excessive load or repeated loading in the core tends to induce debonding along the skin-core interface, threatening the integrity and safety of the whole structure. This dissertation focuses on development of guided wave strategies for health monitoring of honeycomb sandwich structures, based on a piezoelectric actuator/sensor network. The honeycomb sandwich panels, which are composed of aluminum alloy (T6061) skins and hexagonal-celled Nomex core, are specifically considered in the study. First, elastic wave propagation mechanism in honeycomb sandwich structures is numerically and experimentally investigated, based on a piezoelectric actuator/sensor system. Influences of cell geometry parameters upon wave propagation are also discussed. Some wave propagation characteristics, such as wave group velocity dispersion relation and mode tuning capabilities, in the honeycomb composite panels are experimentally characterized. Secondly, effects of skin-core debonding upon the leaky guided wave propagation in honeycomb sandwich structures are studied by the finite element simulation. An appropriate signal difference coefficient is defined to represent the differential features caused by debonding. By means of probability analysis of differential features of transmitted guided waves and the image fusion, the final image of the structure is constructed with improved detection precision. A multilevel sensor network strategy is proposed to detect multiple debondings in the honeycomb sandwich structure. Thirdly, an analytical model considering coupled piezo-elastodynamics is developed to quantitatively describe dynamic load transfer between a surface-bonded piezoelectric wafer actuator and a prestressed plate. The finite element method is used to evaluate the accuracy of the analytical prediction. Effects of prestresses on the

  14. Fatigue studies of polyurethane sandwich structures

    NASA Astrophysics Data System (ADS)

    Sharma, S. C.; Krishna, M.; Narasimha Murthy, H. N.; Sathyamoorthy, M.; Bhattacharya, Debes

    2004-10-01

    The fatigue characteristics of polyurethane foam-cored (PUF) composite sandwich structures were investigated using three-point bending tests carried out according to ASTM C 393. Three types of specimens (epoxy/glass-PUF-epoxy/glass, polyester/glass-PUF-polyester/glass, and epoxy/glass-PUF-polyester/glass) were considered for investigation. Experimental results indicate that degradation of stiffness occurs due to debonding and sliding between the skin and the foam during fatigue cycles. Epoxy/glass-PUF-epoxy/glass sandwich structures exhibit higher bending strength along with higher stiffness degradation than the other two types of sandwich panels, due to higher initial fatigue loading. The lowest fatigue properties have been obtained for the polyester/glass-PUF-polyester/glass sandwich panel specimens. Better performance of the epoxy/glass-PUF-epoxy/glass sandwich panels is most likely due to the superior properties of the outer thin skins. Most of the specimens fail within the foam region and not at the skin level. This situation is possibly due to debonding between the foam and the skin. The fatigue damage development in the foam and skin has been investigated using scanning electron microscopy.

  15. Transient Thermal Testing and Analysis of a Thermally Insulating Structural Sandwich Panel

    NASA Technical Reports Server (NTRS)

    Blosser, Max L.; Daryabeigi, Kamran; Bird, Richard K.; Knutson, Jeffrey R.

    2015-01-01

    A core configuration was devised for a thermally insulating structural sandwich panel. Two titanium prototype panels were constructed to illustrate the proposed sandwich panel geometry. The core of one of the titanium panels was filled with Saffil(trademark) alumina fibrous insulation and the panel was tested in a series of transient thermal tests. Finite element analysis was used to predict the thermal response of the panel using one- and two-dimensional models. Excellent agreement was obtained between predicted and measured temperature histories.

  16. Impact resistance of composite laminated sandwich plates

    NASA Astrophysics Data System (ADS)

    Kim, Chun-Gon; Jun, Eui-Jin

    1992-01-01

    Investigated are the effects of face layup sequence and core density of a sandwich plate on the impact delamination area of the laminated facesheet. The sandwich plate is made of graphite/epoxy faces and Nomex honeycomb core. The size and shape of delamination due to impact at each interply location have been measured by the room temperature deply technique. The shape of the interply delamination under impact is, in general, found to be two-lobed. The shape exhibits very peculiar regularity under various experimental conditions. The quantitative measurement of delamination size has shown that the face layup with small relative orientation between adjacent plies and high density core are desirable in sandwich plates to reduce the impact delamination.

  17. Radiant heating tests of several liquid metal heat-pipe sandwich panels

    SciTech Connect

    Camarda, C.J.; Basiulis, A.

    1983-08-01

    Integral heat pipe sandwich panels, which synergistically combine the thermal efficiency of heat pipes and the structural efficiency of honeycomb sandwich construction, were conceived as a means of alleviating thermal stress problems in the Langley Scramjet Engine. Test panels which utilized two different wickable honeycomb cores, facesheets with screen mesh sintered to the internal surfaces, and a liquid metal working fluid (either sodium or potassium) were tested by radiant heating at various heat load levels. The heat pipe panels reduced maximum temperature differences by 31 percent with sodium working fluid and 45 percent with potassium working fluid. Results indicate that a heat pipe sandwich panel is a potential, simple solution to the engine thermal stress problem. Other interesting applications of the concept include: cold plates for electronic component and circuit card cooling, radiators for large space platforms, low distortion large area structures (e.g., space antennas) and laser mirrors.

  18. Analysis of Stainless Steel Sandwich Panels with a Metal Foam Core for Lightweight Fan Blade Design

    NASA Technical Reports Server (NTRS)

    Min, James B.; Ghosn, Louis J.; Lerch, Bradley A.; Raj, Sai V.; Holland, Frederic A., Jr.; Hebsur, Mohan G.

    2004-01-01

    The quest for cheap, low density and high performance materials in the design of aircraft and rotorcraft engine fan and propeller blades poses immense challenges to the materials and structural design engineers. The present study investigates the use of a sandwich foam fan blade mae up of solid face sheets and a metal foam core. The face sheets and the metal foam core material were an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. The resulting structures possesses a high stiffness while being lighter than a similar solid construction. The material properties of 17-4 PH metal foam are reviewed briefly to describe the characteristics of sandwich structure for a fan blade application. A vibration analysis for natural frequencies and a detailed stress analysis on the 17-4 PH sandwich foam blade design for different combinations of kin thickness and core volume are presented with a comparison to a solid titanium blade.

  19. Mechanical and thermal buckling analysis of rectangular sandwich panels under different edge conditions

    NASA Technical Reports Server (NTRS)

    Ko, William L.

    1994-01-01

    The combined load (mechanical or thermal load) buckling equations were established for orthotropic rectangular sandwich panels under four different edge conditions by using the Rayleigh-Ritz method of minimizing the total potential energy of a structural system. Two-dimensional buckling interaction curves and three-dimensional buckling interaction surfaces were constructed for high-temperature honeycomb-core sandwich panels supported under four different edge conditions. The interaction surfaces provide overall comparison of the panel buckling strengths and the domains of symmetrical and antisymmetrical buckling associated with the different edge conditions. In addition, thermal buckling curves of these sandwich panels are presented. The thermal buckling conditions for the cases with and without thermal moments were found to be identical for the small deformation theory.

  20. Radiant heating tests of several liquid metal heat-pipe sandwich panels

    NASA Technical Reports Server (NTRS)

    Camarda, C. J.; Basiulis, A.

    1983-01-01

    Integral heat-pipe sandwich panels, which synergistically combine the thermal efficiency of heat pipes and the structural efficiency of honeycomb sandwich construction, were conceived as a means of alleviating thermal stress problems in the Langley Scramjet Engine. Test panels which utilized two different wickable honeycomb cores, facesheets with screen mesh sintered to the internal surfaces, and a liquid metal working fluid (either sodium or potassium) were tested by radiant heating at various heat-load levels. The heat-pipe panels reduced maximum temperature differences by 31 percent with sodium working fluid and 45 percent with potassium working fluid. Results indicate that a heat-pipe sandwich panel is a potential, simple solution to the engine thermal stress problem. Other interesting applications of the concept include: cold plates for electronic component and circuit card cooling, radiators for large space platforms, low-distortion large area structures (e.g., space antennas) and laser mirrors.

  1. Radiant heating tests of several liquid metal heat-pipe sandwich panels

    NASA Technical Reports Server (NTRS)

    Camarda, C. J.; Basiulis, A.

    1983-01-01

    Integral heat pipe sandwich panels, which synergistically combine the thermal efficiency of heat pipes and the structural efficiency of honeycomb sandwich construction, were conceived as a means of alleviating thermal stress problems in the Langley Scramjet Engine. Test panels which utilized two different wickable honeycomb cores, facesheets with screen mesh sintered to the internal surfaces, and a liquid metal working fluid (either sodium or potassium) were tested by radiant heating at various heat load levels. The heat pipe panels reduced maximum temperature differences by 31 percent with sodium working fluid and 45 percent with potassium working fluid. Results indicate that a heat pipe sandwich panel is a potential, simple solution to the engine thermal stress problem. Other interesting applications of the concept include: cold plates for electronic component and circuit card cooling, radiators for large space platforms, low distortion large area structures (e.g., space antennas) and laser mirrors.

  2. Long-term hygrothermal effects on damage tolerance of hybrid composite sandwich panels

    NASA Technical Reports Server (NTRS)

    Ishai, Ori; Hiel, Clement; Luft, Michael

    1995-01-01

    A sandwich construction, composed of hybrid carbon-glass fiber-reinforced plastic skins and a syntactic foam core, was selected as the design concept for a wind tunnel compressor blade application, where high damage tolerance and durability are of major importance. Beam specimens were prepared from open-edge and encapsulated sandwich panels which had previously been immersed in water at different temperatures for periods of up to about two years in the extreme case. Moisture absorption and strength characteristics, as related to time of exposure to hygrothermal conditions, were evaluated for the sandwich specimens and their constituents (skins and foam). After different exposure periods, low-velocity impact damage was inflicted on most sandwich specimens and damage characteristics were related to impact energy. Eventually, the residual compressive strengths of the damaged (and undamaged) beams were determined flexurally. Test results show that exposure to hygrothermal conditions leads to significant strength reductions for foam specimens and open-edge sandwich panels, compared with reference specimens stored at room temperature. In the case of skin specimens and for beams prepared from encapsulated sanwich panels that had previously been exposed to hygrothermal conditions, moisture absorption was found to improve strength as related to the reference case. The beneficial effect of moisture on skin performance was, however, limited to moisture contents below 1% (at 50 C and lower temperatures). Above this moisture level and at higher temperatures, strength degradation of the skin seems to prevail.

  3. Analysis of Stainless Steel Sandwich Panels with a Metal Foam Care for Lightweight Fan Blade Design

    NASA Technical Reports Server (NTRS)

    Min, James B.; Ghosn, Louis J.; Lerch, Bradley A.; Raj, Sai V.; Holland, Frederic A., Jr.; Hebsur, Mohan G.

    2004-01-01

    The quest for cheap, low density and high performance materials in the design of aircraft and rotorcraft engine fan and propeller blades poses immense challenges to the materials and structural design engineers. Traditionally, these components have been fabricated using expensive materials such as light weight titanium alloys, polymeric composite materials and carbon-carbon composites. The present study investigates the use of P sandwich foam fan blade made up of solid face sheets and a metal foam core. The face sheets and the metal foam core material were an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. The stiffness of the sandwich structure is increased by separating the two face sheets by a foam core. The resulting structure possesses a high stiffness while being lighter than a similar solid construction. Since the face sheets carry the applied bending loads, the sandwich architecture is a viable engineering concept. The material properties of 17-4 PH metal foam are reviewed briefly to describe the characteristics of the sandwich structure for a fan blade application. A vibration analysis for natural frequencies and P detailed stress analysis on the 17-4 PH sandwich foam blade design for different combinations of skin thickness and core volume %re presented with a comparison to a solid titanium blade.

  4. Nonlinear dynamic analysis of sandwich panels

    NASA Technical Reports Server (NTRS)

    Lush, A. M.

    1984-01-01

    Two analytical techniques applicable to large deflection dynamic response calculations for pressure loaded composite sandwich panels are demonstrated. One technique utilizes finite element modeling with a single equivalent layer representing the face sheets and core. The other technique utilizes the modal analysis computer code DEPROP which was recently modified to include transverse shear deformation in a core layer. The example problem consists of a simply supported rectangular sandwich panel. Included are comparisons of linear and nonlinear static response calculations, in addition to dynamic response calculations.

  5. Donor-acceptor heteroleptic open sandwiches.

    PubMed

    Merino, Gabriel; Beltrán, Hiram I; Vela, Alberto

    2006-02-01

    A series of donor-acceptor heteroleptic open sandwiches with formula CpM-M'Pyl (M = B, Al, Ga; M' = Li, Na; Cp = cyclopentadienyl; Pyl = pentadienyl) has been designed in silico using density functional theory. The most stable complexes are those containing boron as a donor atom. A molecular orbital analysis shows that the s character of the lone pair located at the group 13 element is mainly responsible for the complex stabilization. It is also found that the surrounding medium has a similar effect on these sandwiches such as in the "classical" donor-acceptor complexes, showing a decrement in the group 13 element-alkaline metal bond lengths.

  6. Stresses in edge stiffened anisotropic sandwich plate

    NASA Astrophysics Data System (ADS)

    Rao, Koganti M.; Rao, Y. U. M.

    Hybrid-stress finite elements are used to study the static behavior of an edge stiffened anisotropic sandwich plate subjected to cylindrical bending. The stress concentration factors at the interface of core and stiffener are evaluated. The analysis of the simply-supported sandwich indicates that the state of stress at the interface of core and stiffener is increased and that the edge stiffener induces clamping conditions. The faces and stiffener at the edge are, respectively, subjected to negative and positive transverse shear, causing considerable bending action in faces about their own centroidal axis.

  7. High Strain Rate Response of Sandwich Composites with Nanophased Cores

    NASA Astrophysics Data System (ADS)

    Mahfuz, Hassan; Uddin, Mohammed F.; Rangari, Vijaya K.; Saha, Mrinal C.; Zainuddin, Shaik; Jeelani, Shaik

    2005-05-01

    Polyurethane foam materials have been used as core materials in a sandwich construction with S2-Glass/SC-15 facings. The foam material has been manufactured from liquid polymer precursors of polyurethane. The precursors are made of two components; part-A (diphenylmethane diisocyanate) and part-B (polyol). In one set of experiments, part-A was mixed with part-B to manufacture the foam. In another set, TiO2 nanoparticles have been dispersed in part-A through ultrasonic cavitation technique. The loading of nanoparticles was 3% by weight of the total polymer precursor. The TiO2 nanoparticles were spherical in shape, and were about 29 nm in diameter. Sonic cavitation was carried out with a vibrasound liquid processor at 20 kHz frequency with a power intensity of about 100 kW/m2. The two categories of foams manufactured in this manner were termed as neat and nanophased. Sandwich composites were then fabricated using these two categories of core materials using a co-injection resin transfer molding (CIRTM) technique. Test samples extracted from the panel were subjected to quasi-static as well as high strain rate loadings. Rate of loading varied from 0.002 s-1 to around 1300 s-1. It has been observed that infusion of nanoparticles had a direct correlation with the cell geometry. The cell dimensions increased by about 46% with particle infusion suggesting that nanoparticles might have worked as catalysts during the foaming process. Correspondingly, enhancement in thermal properties was also noticed especially in the TGA experiments. There was also a significant improvement in mechanical properties due to nanoparticle infusion. Average increase in sandwich strength and energy absorption with nanophased cores was between 40 60% over their neat counterparts. Details of manufacturing and analyses of thermal and mechanical tests are presented in this paper.

  8. Insert Design and Manufacturing for Foam-Core Composite Sandwich Structures

    NASA Astrophysics Data System (ADS)

    Lares, Alan

    Sandwich structures have been used in the aerospace industry for many years. The high strength to weight ratios that are possible with sandwich constructions makes them desirable for airframe applications. While sandwich structures are effective at handling distributed loads such as aerodynamic forces, they are prone to damage from concentrated loads at joints or due to impact. This is due to the relatively thin face-sheets and soft core materials typically found in sandwich structures. Carleton University's Uninhabited Aerial Vehicle (UAV) Project Team has designed and manufactured a UAV (GeoSury II Prototype) which features an all composite sandwich structure fuselage structure. The purpose of the aircraft is to conduct geomagnetic surveys. The GeoSury II Prototype serves as the test bed for many areas of research in advancing UAV technologies. Those areas of research include: low cost composite materials manufacturing, geomagnetic data acquisition, obstacle detection, autonomous operations and magnetic signature control. In this thesis work a methodology for designing and manufacturing inserts for foam-core sandwich structures was developed. The results of this research work enables a designer wishing to design a foam-core sandwich airframe structure, a means of quickly manufacturing optimized inserts for the safe introduction of discrete loads into the airframe. The previous GeoSury II Prototype insert designs (v.1 & v.2) were performance tested to establish a benchmark with which to compare future insert designs. Several designs and materials were considered for the new v.3 inserts. A plug and sleeve design was selected, due to its ability to effectively transfer the required loads to the sandwich structure. The insert material was chosen to be epoxy, reinforced with chopped carbon fibre. This material was chosen for its combination of strength, low mass and also compatibility with the face-sheet material. The v.3 insert assembly is 60% lighter than the

  9. Engineering Sandwich Courses in British Technological Universities

    ERIC Educational Resources Information Center

    Moore, J. P.; Urry, S. A.

    1971-01-01

    The development of sandwich courses, a review of their progress and a consideration of the problems associated with their operation are described. These courses are integrated so that industrial training is required and is interspersed between academic segments. (Author/TS)

  10. Wave propagation in metamaterial lattice sandwich plates

    NASA Astrophysics Data System (ADS)

    Fang, Xin; Wen, Jihong; Yin, Jianfei; Yu, Dianlong

    2016-04-01

    This paper designed a special acoustic metamaterial 3D Kagome lattice sandwich plate. Dispersion properties and vibration responses of both traditional plate and metamaterial plate are investigated based on FEA methods. The traditional plate does not have low-frequency complete bandgaps, but the metamaterial plate has low-frequency complete bandgap (at 620Hz) coming from the symmetrical local cantilever resonators. The bandgap frequency is approximate to the first-order natural frequency of the oscillator. Complex wave modes are analyzed. The dispersion curves of longitudinal waves exist in the flexural bandgap. The dispersion properties demonstrate the metamaterial design is advantageous to suppress the low-frequency flexural wave propagation in lattice sandwich plate. The flexural vibrations near the bandgap are also suppressed efficiently. The longitudinal excitation stimulates mainly longitudinal waves and lots of low-frequency flexural vibration modes are avoided. Furthermore, the free edge effects in metamaterial plate provide new method for damping optimizations. The influences of damping on vibrations of the metamaterial sandwich plate are studied. Damping has global influence on the wave propagation; stronger damping will induce more vibration attenuation. The results enlighten us damping and metamaterial design approaches can be unite in the sandwich plates to suppress the wave propagations.

  11. Feedback Sandwiches Affect Perceptions but Not Performance

    ERIC Educational Resources Information Center

    Parkes, Jay; Abercrombie, Sara; McCarty, Teresita

    2013-01-01

    The feedback sandwich technique-make positive comments; provide critique; end with positive comments-is commonly recommended to feedback givers despite scant evidence of its efficacy. These two studies (N = 20; N = 350) of written peer feedback with third-year medical students on clinical patient note-writing assignments indicate that students…

  12. Understanding Successful Sandwich Placements: A Bourdieusian Approach

    ERIC Educational Resources Information Center

    Clark, Martyn; Zukas, Miriam

    2016-01-01

    Sandwich placements and other integrated work and study schemes are increasingly advocated as a key means by which universities can promote students' employability. However, there is little understanding of how successful placements work in terms of facilitating learning and development. Drawing on three longitudinal case studies of students who…

  13. Impact-damaged graphite-thermoplastic trapezoidal-corrugation sandwich and semi-sandwich panels

    NASA Technical Reports Server (NTRS)

    Jegley, D.

    1993-01-01

    The results of a study of the effects of impact damage on compression-loaded trapezoidal-corrugation sandwich and semi-sandwich graphite-thermoplastic panels are presented. Sandwich panels with two identical face sheets and a trapezoidal corrugated core between them, and semi-sandwich panels with a corrugation attached to a single skin are considered in this study. Panels were designed, fabricated and tested. The panels were made using the manufacturing process of thermoforming, a less-commonly used technique for fabricating composite parts. Experimental results for unimpacted control panels and panels subjected to impact damage prior to loading are presented. Little work can be found in the literature about these configurations of thermoformed panels.

  14. Design of an electro-Fenton system with a novel sandwich film cathode for wastewater treatment.

    PubMed

    Fan, Yan; Ai, Zhihui; Zhang, Lizhi

    2010-04-15

    In this study, we demonstrate an electro-Fenton (E-Fenton) system constructed with a novel sandwich film cathode (SFC). For the fabrication of SFC, Fe(2+)-chitosan (Fe-CHI) was first deposited on foam nickel (Fe-CHI/Ni). Then two pieces of Fe-CHI/Ni was used to fasten one piece of activated carbon fiber (ACF) to obtain a Fe-CHI/Ni|ACF|Fe-CHI/Ni sandwich film cathode. We interestingly found that this SFC based E-Fenton system could effectively degrade rodamine B with in situ generating both hydrogen peroxide and iron ions. Its degradation efficiency was significantly higher than those of the E-Fenton systems constructed with composite cathodes of carbon nanotubes with Fe@Fe(2)O(3) core-shell nanowires or Cu(2)O nanocubes reported in our previous studies. Hydrogen peroxide electrogenerated through the reduction of O(2) adsorbed on the sandwich film cathode and the iron ions produced by the leakage from Fe(2+)-chitosan film during the E-Fenton reaction were, respectively, monitored, providing clues to understand the high efficiency of this novel SFC based E-Fenton system. More importantly, this low-cost sandwich film cathode was very stable and could be reused without catalytic activity decrease, suggesting its potential application in the wastewater treatment.

  15. Sound Transmission through a Cylindrical Sandwich Shell with Honeycomb Core

    NASA Technical Reports Server (NTRS)

    Tang, Yvette Y.; Robinson, Jay H.; Silcox, Richard J.

    1996-01-01

    Sound transmission through an infinite cylindrical sandwich shell is studied in the context of the transmission of airborne sound into aircraft interiors. The cylindrical shell is immersed in fluid media and excited by an oblique incident plane sound wave. The internal and external fluids are different and there is uniform airflow in the external fluid medium. An explicit expression of transmission loss is derived in terms of modal impedance of the fluids and the shell. The results show the effects of (a) the incident angles of the plane wave; (b) the flight conditions of Mach number and altitude of the aircraft; (c) the ratios between the core thickness and the total thickness of the shell; and (d) the structural loss factors on the transmission loss. Comparisons of the transmission loss are made among different shell constructions and different shell theories.

  16. Applications of thin-film sandwich crystallization platforms

    PubMed Central

    Axford, Danny; Aller, Pierre; Sanchez-Weatherby, Juan; Sandy, James

    2016-01-01

    Examples are shown of protein crystallization in, and data collection from, solutions sandwiched between thin polymer films using vapour-diffusion and batch methods. The crystallization platform is optimal for both visualization and in situ data collection, with the need for traditional harvesting being eliminated. In wells constructed from the thinnest plastic and with a minimum of aqueous liquid, flash-cooling to 100 K is possible without significant ice formation and without any degradation in crystal quality. The approach is simple; it utilizes low-cost consumables but yields high-quality data with minimal sample intervention and, with the very low levels of background X-ray scatter that are observed, is optimal for microcrystals. PMID:27050266

  17. Buckling optimisation of sandwich cylindrical panels

    NASA Astrophysics Data System (ADS)

    Abouhamzeh, M.; Sadighi, M.

    2016-06-01

    In this paper, the buckling load optimisation is performed on sandwich cylindrical panels. A finite element program is developed in MATLAB to solve the governing differential equations of the global buckling of the structure. In order to find the optimal solution, the genetic algorithm Toolbox in MATLAB is implemented. Verifications are made for both the buckling finite element code and also the results from the genetic algorithm by comparisons to the results available in literature. Sandwich cylindrical panels are optimised for the buckling strength with isotropic or orthotropic cores with different boundary conditions. Results are presented in terms of stacking sequence of fibers in the face sheets and core to face sheet thickness ratio.

  18. Fiber Composite Sandwich Thermostructural Behavior: Computational Simulation

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Aiello, R. A.; Murthy, P. L. N.

    1986-01-01

    Several computational levels of progressive sophistication/simplification are described to computationally simulate composite sandwich hygral, thermal, and structural behavior. The computational levels of sophistication include: (1) three-dimensional detailed finite element modeling of the honeycomb, the adhesive and the composite faces; (2) three-dimensional finite element modeling of the honeycomb assumed to be an equivalent continuous, homogeneous medium, the adhesive and the composite faces; (3) laminate theory simulation where the honeycomb (metal or composite) is assumed to consist of plies with equivalent properties; and (4) derivations of approximate, simplified equations for thermal and mechanical properties by simulating the honeycomb as an equivalent homogeneous medium. The approximate equations are combined with composite hygrothermomechanical and laminate theories to provide a simple and effective computational procedure for simulating the thermomechanical/thermostructural behavior of fiber composite sandwich structures.

  19. Ultrasonic Spectroscopy of Stainless Steel Sandwich Panels

    NASA Technical Reports Server (NTRS)

    Cosgriff, Laura M.; Lerch, Bradley A.; Hebsur, Mohan G.; Baaklini, George Y.; Ghosn, Louis J.

    2003-01-01

    Enhanced, lightweight material systems, such as 17-4PH stainless steel sandwich panels are being developed for use as fan blades and fan containment material systems for next generation engines. In order to improve the production for these systems, nondestructive evaluation (NDE) techniques, such as ultrasonic spectroscopy, are being utilized to evaluate the brazing quality between the 17-4PH stainless steel face plates and the 17-4PH stainless steel foam core. Based on NDE data, shear tests are performed on sections representing various levels of brazing quality from an initial batch of these sandwich structures. Metallographic characterization of brazing is done to corroborate NDE findings and the observed shear failure mechanisms.

  20. BMI Sandwich Wing Box Analysis and Test

    NASA Technical Reports Server (NTRS)

    Palm, Tod; Mahler, Mary; Shah, Chandu; Rouse, Marshall; Bush, Harold; Wu, Chauncey; Small, William J.

    2000-01-01

    A composite sandwich single bay wing box test article was developed by Northrop Grumman and tested recently at NASA Langley Research Center. The objectives for the wing box development effort were to provide a demonstration article for manufacturing scale up of structural concepts related to a high speed transport wing, and to validate the structural performance of the design. The box concept consisted of highly loaded composite sandwich wing skins, with moderately loaded composite sandwich spars. The dimensions of the box were chosen to represent a single bay of the main wing box, with a spar spacing of 30 inches, height of 20 inches constant depth, and length of 64 inches. The bismaleimide facesheet laminates and titanium honeycomb core chosen for this task are high temperature materials able to sustain a 300F service temperature. The completed test article is shown in Figure 1. The tests at NASA Langley demonstrated the structures ability to sustain axial tension and compression loads in excess of 20,000 lb/in, and to maintain integrity in the thermal environment. Test procedures, analysis failure predictions, and test results are presented.

  1. Mechanical and thermal buckling analysis of sandwich panels under different edge conditions

    NASA Technical Reports Server (NTRS)

    Ko, William L.

    1993-01-01

    By using the Rayleigh-Ritz method of minimizing the total potential energy of a structural system, combined load (mechanical or thermal load) buckling equations are established for orthotropic rectangular sandwich panels supported under four different edge conditions. Two-dimensional buckling interaction curves and three dimensional buckling interaction surfaces are constructed for high-temperature honeycomb-core sandwich panels supported under four different edge conditions. The interaction surfaces provide easy comparison of the panel buckling strengths and the domains of symmetrical and antisymmetrical buckling associated with the different edge conditions. Thermal buckling curves of the sandwich panels also are presented. The thermal buckling conditions for the cases with and without thermal moments were found to be identical for the small deformation theory. In sandwich panels, the effect of transverse shear is quite large, and by neglecting the transverse shear effect, the buckling loads could be overpredicted considerably. Clamping of the edges could greatly increase buckling strength more in compression than in shear.

  2. Sandwich-like layer-by-layer assembly of gold nanoparticles with tunable SERS properties

    PubMed Central

    Bai, Lu; Zhao, Guizhe

    2016-01-01

    Summary Sandwich-like layer-by-layer thin films consisting of polyelectrolytes and gold nanoparticles were utilized to construct surface-enhanced Raman scattering (SERS) substrates with tunable SERS properties. It is found that both the size of the nanoparticles in the layers and the interlayer distance significantly influence the SERS performance of the multilayered thin film. These simple, low-cost, easily processable and controllable SERS substrates have a promising future in the field of molecular sensing. PMID:27547620

  3. Sandwich-like layer-by-layer assembly of gold nanoparticles with tunable SERS properties.

    PubMed

    Liu, Zhicheng; Bai, Lu; Zhao, Guizhe; Liu, Yaqing

    2016-01-01

    Sandwich-like layer-by-layer thin films consisting of polyelectrolytes and gold nanoparticles were utilized to construct surface-enhanced Raman scattering (SERS) substrates with tunable SERS properties. It is found that both the size of the nanoparticles in the layers and the interlayer distance significantly influence the SERS performance of the multilayered thin film. These simple, low-cost, easily processable and controllable SERS substrates have a promising future in the field of molecular sensing. PMID:27547620

  4. Mode I Toughness Measurements of Core/Facesheet Bonds in Honeycomb Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Nettles, Alan T.; Ratcliffe, James G.

    2006-01-01

    Composite sandwich structures will be used in many future applications in aerospace, marine and offshore industries due to the fact that the strength and stiffness to mass ratios surpass any other structural type. Sandwich structure also offers advantages over traditional stiffened panels such as ease of manufacturing and repair. During the last three decades, sandwich structure has been used extensively for secondary structure in aircraft (fuselage floors, rudders and radome structure). Sandwich structure is also used as primary structure in rotorcraft, the most common example being the trailing edge of rotor blades. As with other types of composite construction, sandwich structure exhibits several types of failure mode such as facesheet wrinkling, core crushing and sandwich buckling. Facesheet/core debonding has also been observed in the marine and aerospace industry. During this failure mode, peel stresses applied to an existing facesheet/core debond or an interface low in toughness, results in the facesheet being peeled from the core material, possibly leading to a significant loss in structural integrity of the sandwich panel. In an incident during a test on a liquid hydrogen fuel tank of the X-33 prototype vehicle, the outer graphite/epoxy facesheet and honeycomb core became debonded from the inner facesheet along significant areas, leading to failure of the tank. As a consequence of the accident; significant efforts were made to characterize the toughness of the facesheet/core bond. Currently, the only standardized method available for assessing the quality of the facesheet/core interface is the climbing drum peel test (ASTM D1781). During this test a sandwich beam is removed from a panel and the lip of one of the facesheets is attached to a drum, as shown in Fig. 1. The drum is then rotated along the sandwich beam, causing the facesheet to peel from the core. This method has two major drawbacks. First, it is not possible to obtain quantitative fracture data

  5. Analytical determination of the ultimate strength of sandwich beams

    NASA Astrophysics Data System (ADS)

    Theotokoglou, Efstathios E.

    1996-09-01

    An analytical determination of the ultimate strength of a typical GRP/PVC sandwich beam has been performed. These beams represent common building practise in marine applications. Equations describing the behaviour of a sandwich panel under beam loading and various failure modes have been developed. The method has been applied to predict the ultimate load for a simple supported sandwich beam. The critical loads have been compared with those from the experimental investigation of a typical bulkhead-to-hull GRP/PVC sandwich T-joint under pull out forces.

  6. Buckling Analysis of Debonded Sandwich Panel Under Compression

    NASA Technical Reports Server (NTRS)

    Sleight, David W.; Wang, John T.

    1995-01-01

    A sandwich panel with initial through-the-width debonds is analyzed to study the buckling of its faceskin when subject to an in-plane compressive load. The debonded faceskin is modeled as a beam on a Winkler elastic foundation in which the springs of the elastic foundation represent the sandwich foam. The Rayleigh-Ritz and finite-difference methods are used to predict the critical buckling load for various debond lengths and stiffnesses of the sandwich foam. The accuracy of the methods is assessed with a plane-strain finite-element analysis. Results indicate that the elastic foundation approach underpredicts buckling loads for sandwich panels with isotropic foam cores.

  7. Elastic constants for superplastically formed/diffusion-bonded sandwich structures

    NASA Technical Reports Server (NTRS)

    Ko, W. L.

    1979-01-01

    Formulae and the associated graphs are presented for contrasting the effective elastic constants for a superplastically formed/diffusion-bonded (SPF/DB) corrugated sandwich core and a honeycomb sandwich core. The results used in the comparison of the structural properties of the two types of sandwich cores are under conditions of equal sandwich density. It was found that the stiffness in the thickness direction of the optimum SPF/DB corrugated core (i.e., triangular truss core) was lower than that of the honeycomb core, and that the former had higher transverse shear stiffness than the latter.

  8. A double-sandwich ELISA for identification of monoclonal antibodies suitable for sandwich immunoassays

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The sandwich immunoassay (sIA) is an invaluable technique for concentrating, detecting, and quantifying target antigens. The two critical components required are a capture antibody and a detection antibody, each binding a different epitope on the target antigen. The specific antibodies incorporated...

  9. Modeling of Sandwich Sheets with Metallic Foam

    SciTech Connect

    Mata, H.; Jorge, R. Natal; Fernandes, A. A.; Parente, M. P. L.; Santos, A.; Valente, R. A. F.

    2011-08-22

    World-wide vehicles safety experts agree that significant further reductions in fatalities and injuries can be achieved as a result of the use of new lightweight and energy absorbing materials. On this work, the authors present the development and evaluation of an innovative system able to perform reliable panels of sandwich sheets with metallic foam cores for industrial applications. The mathematical model used to describe the behavior of sandwich shells with metal cores foam is presented and some numerical examples are presented. In order to validate those results mechanical experiments are carried out. Using the crushable foam constitutive model, available on ABAQUS, a set of different mechanical tests were simulated. There are two variants of this model available on ABAQUS: the volumetric hardening model and the isotropic hardening model. As a first approximation we chose the isotropic hardening variant. The isotropic hardening model available uses a yield surface that is an ellipse centered at the origin in the p-q stress plane. Based on this constitutive model for the foam, numerical simulations of the tensile and bulge test will be conducted. The numerical results will be validated using the data obtained from the experimental results.

  10. Aptamer-based Sandwich Assay and its Clinical Outlooks for Detecting Lipocalin-2 in Hepatocellular Carcinoma (HCC)

    PubMed Central

    Lee, Kyeong-Ah; Ahn, Ji-Young; Lee, Sang-Hee; Singh Sekhon, Simranjeet; Kim, Dae-Ghon; Min, Jiho; Kim, Yang-Hoon

    2015-01-01

    We validated a single-stranded, DNA aptamer-based, diagnostic method capable of detecting Lipocalin-2 (LCN2), a biomarker from clinically relevant hepatocellular carcinoma (HCC) patient serum, in the sandwich assay format. Nine aptamers (LCN2_apta1 to LCN2_apta9) for LCN2 were screened with SELEX processes, and a sandwich pair (LCN2_apta2 and LCN2_apta4) was finally chosen using surface plasmon resonance (SPR) and dot blotting analysis. The result of the proposed aptamer sandwich construction shows that LCN2 was sensitively detected in the concentration range of 2.5–500 ng mL−1 with a limit of detection of 0.6 ng mL−1. Quantitative measurement tests in HCC patients were run on straight serum and were compared with the performance of the conventional antibody-based ELISA kit. The aptamer sandwich assay demonstrated an excellent dynamic range for LCN2 at clinically relevant serum levels, covering sub-nanogram per mL concentrations. The new approach offers a simple and robust method for detecting serum biomarkers that have low and moderate abundance. It consists of functionalization, hybridization and signal read-out, and no dilution is required. The results of the study demonstrate the capability of the aptamer sandwich assay platform for diagnosing HCC and its potential applicability to the point-of-care testing (POCT) system. PMID:26039737

  11. Design, fabrication and test of liquid metal heat-pipe sandwich panels

    NASA Technical Reports Server (NTRS)

    Basiulis, A.; Camarda, C. J.

    1983-01-01

    Integral heat-pipe sandwich panels, which synergistically combine the thermal efficiency of heat pipes and the structural efficiency of honeycomb sandwich panel construction, were fabricated and tested. The designs utilize two different wickable honeycomb cores, facesheets with screen mesh sintered to the internal surfaces, and potassium or sodium as the working fluid. Panels were tested by radiant heating, and the results indicate successful heat pipe operation at temperatures of approximately 922K (1200F). These panels, in addition to solving potential thermal stress problems in an Airframe-Integrated Scramjet Engine, have potential applications as cold plates for electronic component cooling, as radiators for space platforms, and as low distortion, large area structures.

  12. Design, fabrication and test of liquid metal heat-pipe sandwich panels

    NASA Technical Reports Server (NTRS)

    Basiulis, A.; Camarda, C. J.

    1982-01-01

    Integral heat-pipe sandwich panels, which synergistically combine the thermal efficiency of heat pipes and the structural efficiency of honeycomb sandwich panel construction, were fabricated and tested. The designs utilize two different wickable honeycomb cores, facesheets with screen mesh sintered to the internal surfaces, and potassium or sodium as the working fluid. Panels were tested by radiant heating, and the results indicate successful heat pipe operation at temperatures of approximately 922 K (1200 F). These panels, in addition to solving potential thermal stress problems in an Airframe-Integrated Scramjet Engine, have potential applications as cold plates for electronic component cooling, as radiators for space platforms, and as low distortion, large area structures.

  13. High Velocity Impact Response of Composite Lattice Core Sandwich Structures

    NASA Astrophysics Data System (ADS)

    Wang, Bing; Zhang, Guoqi; Wang, Shixun; Ma, Li; Wu, Linzhi

    2014-04-01

    In this research, carbon fiber reinforced polymer (CFRP) composite sandwich structures with pyramidal lattice core subjected to high velocity impact ranging from 180 to 2,000 m/s have been investigated by experimental and numerical methods. Experiments using a two-stage light gas gun are conducted to investigate the impact process and to validate the finite element (FE) model. The energy absorption efficiency (EAE) in carbon fiber composite sandwich panels is compared with that of 304 stainless-steel and aluminum alloy lattice core sandwich structures. In a specific impact energy range, energy absorption efficiency in carbon fiber composite sandwich panels is higher than that of 304 stainless-steel sandwich panels and aluminum alloy sandwich panels owing to the big density of metal materials. Therefore, in addition to the multi-functional applications, carbon fiber composite sandwich panels have a potential advantage to substitute the metal sandwich panels as high velocity impact resistance structures under a specific impact energy range.

  14. Finite Element Modeling of the Buckling Response of Sandwich Panels

    NASA Technical Reports Server (NTRS)

    Rose, Cheryl A.; Moore, David F.; Knight, Norman F., Jr.; Rankin, Charles C.

    2002-01-01

    A comparative study of different modeling approaches for predicting sandwich panel buckling response is described. The study considers sandwich panels with anisotropic face sheets and a very thick core. Results from conventional analytical solutions for sandwich panel overall buckling and face-sheet-wrinkling type modes are compared with solutions obtained using different finite element modeling approaches. Finite element solutions are obtained using layered shell element models, with and without transverse shear flexibility, layered shell/solid element models, with shell elements for the face sheets and solid elements for the core, and sandwich models using a recently developed specialty sandwich element. Convergence characteristics of the shell/solid and sandwich element modeling approaches with respect to in-plane and through-the-thickness discretization, are demonstrated. Results of the study indicate that the specialty sandwich element provides an accurate and effective modeling approach for predicting both overall and localized sandwich panel buckling response. Furthermore, results indicate that anisotropy of the face sheets, along with the ratio of principle elastic moduli, affect the buckling response and these effects may not be represented accurately by analytical solutions. Modeling recommendations are also provided.

  15. Practical Instruction in Tissue Culture and Cytogenetics for Sandwich Students.

    ERIC Educational Resources Information Center

    Williams, D. C.; Bishun, N. P.

    1973-01-01

    Describes the training and practical techniques taught to students involved in a sandwich course at the Tissue Culture and Cytogenetics Unit of the Marie Curie Memorial Foundation, Surrey, England. Students spend a minimum of six months involved in the sandwich course before returning to university for a final academic year. (JR)

  16. Compressive Strength of Stainless-Steel Sandwiches at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Mathauser, Eldon E.; Pride, Richard A.

    1959-01-01

    Experimental results are presented from crippling tests of stainless-steel sandwich specimens in the temperature range from 80 F to 1,200 F. The specimens included resistance-welded 17-7 PH stainless-steel sandwiches with single-corrugated cores, type 301 stainless-steel sandwiches with double-corrugated cores, and brazed 17-7 PH stainless-steel sandwiches with honeycomb cores. The experimental strengths are compared with predicted buckling and crippling strengths. The crippling strengths were predicted from the calculated maximum strength of the individual plate elements of the sandwiches and from a correlation procedure which gives the elevated-temperature crippling strength when the experimental room-temperature crippling strengths are known. Photographs of some of the tested specimens are included to show the modes of failure.

  17. Development, testing, and numerical modeling of a foam sandwich biocomposite

    NASA Astrophysics Data System (ADS)

    Chachra, Ricky

    This study develops a novel sandwich composite material using plant based materials for potential use in nonstructural building applications. The face sheets comprise woven hemp fabric and a sap based epoxy, while the core comprises castor oil based foam with waste rice hulls as reinforcement. Mechanical properties of the individual materials are tested in uniaxial compression and tension for the foam and hemp, respectively. The sandwich composite is tested in 3 point bending. Flexural results are compared to a finite element model developed in the commercial software Abaqus, and the validated model is then used to investigate alternate sandwich geometries. Sandwich model responses are compared to existing standards for nonstructural building panels, showing that the novel material is roughly half the strength of equally thick drywall. When space limitations are not an issue, a double thickness sandwich biocomposite is found to be a structurally acceptable replacement for standard gypsum drywall.

  18. Impact damage in aircraft composite sandwich panels

    NASA Astrophysics Data System (ADS)

    Mordasky, Matthew D.

    An experimental study was conducted to develop an improved understanding of the damage caused by runway debris and environmental threats on aircraft structures. The velocities of impacts for stationary aircraft and aircraft under landing and takeoff speeds was investigated. The impact damage by concrete, asphalt, aluminum, hail and rubber sphere projectiles was explored in detail. Additionally, a kinetic energy and momentum experimental study was performed to look at the nature of the impacts in more detail. A method for recording the contact force history of the impact by an instrumented projectile was developed and tested. The sandwich composite investigated was an IM7-8552 unidirectional prepreg adhered to a NOMEXRTM core with an FM300K film adhesive. Impact experiments were conducted with a gas gun built in-house specifically for delivering projectiles to a sandwich composite target in this specic velocity regime (10--140 m/s). The effect on the impact damage by the projectile was investigated by ultrasonic C-scan, high speed camera and scanning electron and optical microscopy. Ultrasonic C-scans revealed the full extent of damage caused by each projectile, while the high speed camera enabled precise projectile velocity measurements that were used for striking velocity, kinetic energy and momentum analyses. Scanning electron and optical images revealed specific features of the panel failure and manufacturing artifacts within the lamina and honeycomb core. The damage of the panels by different projectiles was found to have a similar damage area for equivalent energy levels, except for rubber which had a damage area that increased greatly with striking velocity. Further investigation was taken by kinetic energy and momentum based comparisons of 19 mm diameter stainless steel sphere projectiles in order to examine the dominating damage mechanisms. The sandwich targets were struck by acrylic, aluminum, alumina, stainless steel and tungsten carbide spheres of the

  19. 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

  20. Which Is The Best Sandwich Compound? Hexaphenylbenzene Substituted By Sandwich Compounds Bearing Sc, Cr, and Fe.

    PubMed

    Ramos, Estrella; Martínez, Ana; Rios, Citlalli; Salcedo, Roberto

    2015-11-25

    The electronic properties of nine different hexaarylbenzene molecules substituted by sandwich compounds have been studied by applying density functional theory. Different structures and the particular electron donor power of these systems have been considered in order to analyze their oxidant capacity, using bis(ciclopentadienyl) scandium, ferrocene, and bis(benzene)chromium as sandwich compounds. Both monometallic and bimetallic combinations are investigated. According to the ionization energies and electron affinities, compounds with Cr are nucleophiles and represent the best electron donors, whereas compounds with Sc are electrophiles and represent the best electron acceptors. The worse electron donor or acceptor is hexakis(4-ferrocenyl phenyl) benzene. This is very significant, as it implies that the very well-known electronic properties of hexakis(4-ferrocenyl phenyl) benzene can be improved by substituting with other metals, such as Sc and Cr. This suggests several possible applications for these compounds. PMID:26528582

  1. Nanoparticle organization in sandwiched polymer brushes.

    PubMed

    Curk, Tine; Martinez-Veracoechea, Francisco J; Frenkel, Daan; Dobnikar, Jure

    2014-05-14

    The organization of nanoparticles inside grafted polymer layers is governed by the interplay of polymer-induced entropic interactions and the action of externally applied fields. Earlier work had shown that strong external forces can drive the formation of colloidal structures in polymer brushes. Here we show that external fields are not essential to obtain such colloidal patterns: we report Monte Carlo and molecular dynamics simulations that demonstrate that ordered structures can be achieved by compressing a "sandwich" of two grafted polymer layers, or by squeezing a coated nanotube, with nanoparticles in between. We show that the pattern formation can be efficiently controlled by the applied pressure, while the characteristic length-scale, that is, the typical width of the patterns, is sensitive to the length of the polymers. Based on the results of the simulations, we derive an approximate equation of state for nanosandwiches. PMID:24707901

  2. "Inverse Sandwich" Complexes of Perhalogenated Cyclohexasilane

    SciTech Connect

    Dai, Xuliang; Shulz, Douglas; Braun, Christopher; Ugrinov, Angel; and Boudjouk, Philip

    2010-04-20

    Perhalogenated cyclohexasilanes, Si6X12 (X = Cl, Br), were prepared by reaction of Si6H12 with molecular chlorine or bromine in cold (-89 °C) dichloromethane. Single-crystal structural determination by X-ray analysis shows that the six silicon atoms comprising Si6Br12 adopt a chair conformation in the solid state. The addition of p-tolunitrile to Si6X12 (X = Cl, Br) leads to the rapid formation of colorless precipitates. Si6Br12 3 2(p-CH3C6H4CN) adopts an 'inverse sandwich' structure where the N atoms of the p-tolunitrile molecules are μ6 bonded and are located above and below the planar hexagonal Si6 ring. In conclusion, Si6X12 (X = Cl, Br) was synthesized by molecular halogenation of Si6H12 in high yield and good purity. Perhalogenated cyclohexasilanes react with p-tolunitrile to give 'inverse sandwich' adducts 3 and 4 with a planar Si6 ring upon coordination. Our future reports will detail dianionic adducts based on tetra-n-butylammonium halides as well as a monoanionic adamantyl azide adduct of Si6Cl12. It is straightforward to conceptualize the utility of Si6X12 ∙ Ln chemistry in molecular assembly of silicon-based clusters/tubes/wires. Thereby, we proffer that this constitutes a new landscape in Si chemistry.

  3. Optimization of Sandwich Composites Fuselages Under Flight Loads

    NASA Astrophysics Data System (ADS)

    Yuan, Chongxin; Bergsma, Otto; Koussios, Sotiris; Zu, Lei; Beukers, Adriaan

    2012-02-01

    The sandwich composites fuselages appear to be a promising choice for the future aircrafts because of their structural efficiency and functional integration advantages. However, the design of sandwich composites is more complex than other structures because of many involved variables. In this paper, the fuselage is designed as a sandwich composites cylinder, and its structural optimization using the finite element method (FEM) is outlined to obtain the minimum weight. The constraints include structural stability and the composites failure criteria. In order to get a verification baseline for the FEM analysis, the stability of sandwich structures is studied and the optimal design is performed based on the analytical formulae. Then, the predicted buckling loads and the optimization results obtained from a FEM model are compared with that from the analytical formulas, and a good agreement is achieved. A detailed parametric optimal design for the sandwich composites cylinder is conducted. The optimization method used here includes two steps: the minimization of the layer thickness followed by tailoring of the fiber orientation. The factors comprise layer number, fiber orientation, core thickness, frame dimension and spacing. Results show that the two-step optimization is an effective method for the sandwich composites and the foam sandwich cylinder with core thickness of 5 mm and frame pitch of 0.5 m exhibits the minimum weight.

  4. Development and Mechanical Behavior of FML/Aluminium Foam Sandwiches

    NASA Astrophysics Data System (ADS)

    Baştürk, S. B.; Tanoğlu, M.

    2013-10-01

    In this study, the Fiber-Metal Laminates (FMLs) containing glass fiber reinforced polypropylene (GFPP) and aluminum (Al) sheet were consolidated with Al foam cores for preparing the sandwich panels. The aim of this article is the comparison of the flexural properties of FML/Al foam sandwich panels bonded with various surface modification approaches (silane treatment and combination of silane treatment with polypropylene (PP) based film addition). The FML/foam sandwich systems were fabricated by laminating the components in a mould at 200 °C under 1.5 MPa pressure. The energy absorbtion capacities and flexural mechanical properties of the prepared sandwich systems were evaluated by mechanical tests. Experiments were performed on samples of varying foam thicknesses (8, 20 and 30 mm). The bonding among the sandwich components were achieved by various surface modification techniques. The Al sheet/Al foam sandwiches were also consolidated by bonding the components with an epoxy adhesive to reveal the effect of GFPP on the flexural performance of the sandwich structures.

  5. Evaluation of Analysis Techniques for Fluted-Core Sandwich Cylinders

    NASA Technical Reports Server (NTRS)

    Lovejoy, Andrew E.; Schultz, Marc R.

    2012-01-01

    Buckling-critical launch-vehicle structures require structural concepts that have high bending stiffness and low mass. Fluted-core, also known as truss-core, sandwich construction is one such concept. In an effort to identify an analysis method appropriate for the preliminary design of fluted-core cylinders, the current paper presents and compares results from several analysis techniques applied to a specific composite fluted-core test article. The analysis techniques are evaluated in terms of their ease of use and for their appropriateness at certain stages throughout a design analysis cycle (DAC). Current analysis techniques that provide accurate determination of the global buckling load are not readily applicable early in the DAC, such as during preliminary design, because they are too costly to run. An analytical approach that neglects transverse-shear deformation is easily applied during preliminary design, but the lack of transverse-shear deformation results in global buckling load predictions that are significantly higher than those from more detailed analysis methods. The current state of the art is either too complex to be applied for preliminary design, or is incapable of the accuracy required to determine global buckling loads for fluted-core cylinders. Therefore, it is necessary to develop an analytical method for calculating global buckling loads of fluted-core cylinders that includes transverse-shear deformations, and that can be easily incorporated in preliminary design.

  6. Transmission Loss and Absorption of Corrugated Core Sandwich Panels With Embedded Resonators

    NASA Technical Reports Server (NTRS)

    Allen, Albert R.; Schiller, Noah H.; Zalewski, Bart F.; Rosenthal, Bruce N.

    2014-01-01

    The effect of embedded resonators on the diffuse field sound transmission loss and absorption of composite corrugated core sandwich panels has been evaluated experimentally. Two 1.219 m × 2.438 m panels with embedded resonator arrangements targeting frequencies near 100 Hz were evaluated using non-standard processing of ASTM E90-09 acoustic transmission loss and ASTM C423-09a room absorption test measurements. Each panel is comprised of two composite face sheets sandwiching a corrugated core with a trapezoidal cross section. When inlet openings are introduced in one face sheet, the chambers within the core can be used as embedded acoustic resonators. Changes to the inlet and chamber partition locations allow this type of structure to be tuned for targeted spectrum passive noise control. Because the core chambers are aligned with the plane of the panel, the resonators can be tuned for low frequencies without compromising the sandwich panel construction, which is typically sized to meet static load requirements. Absorption and transmission loss performance improvements attributed to opening the inlets were apparent for some configurations and inconclusive for others.

  7. An enriched 1D finite element for the buckling analysis of sandwich beam-columns

    NASA Astrophysics Data System (ADS)

    Sad Saoud, Kahina; Le Grognec, Philippe

    2016-06-01

    Sandwich constructions have been widely used during the last few decades in various practical applications, especially thanks to the attractive compromise between a lightweight and high mechanical properties. Nevertheless, despite the advances achieved to date, buckling still remains a major failure mode for sandwich materials which often fatally leads to collapse. Recently, one of the authors derived closed-form analytical solutions for the buckling analysis of sandwich beam-columns under compression or pure bending. These solutions are based on a specific hybrid formulation where the faces are represented by Euler-Bernoulli beams and the core layer is described as a 2D continuous medium. When considering more complex loadings or non-trivial boundary conditions, closed-form solutions are no more available and one must resort to numerical models. Instead of using a 2D computationally expensive model, the present paper aims at developing an original enriched beam finite element. It is based on the previous analytical formulation, insofar as the skin layers are modeled by Timoshenko beams whereas the displacement fields in the core layer are described by means of hyperbolic functions, in accordance with the modal displacement fields obtained analytically. By using this 1D finite element, linearized buckling analyses are performed for various loading cases, whose results are confronted to either analytical or numerical reference solutions, for validation purposes.

  8. Calibration of an analytical thermal model for an epoxy-based composite sandwich design

    NASA Astrophysics Data System (ADS)

    Reinarts, Thomas R.; Davis, Darrell; Stuckey, Charles I.

    2001-02-01

    An epoxy-based sandwich configuration was designed to meet the structural and thermal requirements of a nose cap for the space shuttle solid rocket boosters (SRB's). This project was suspended in late 1999, but the information gathered during this work is unique in the sense that portions of graphite-epoxy layers were modeled at temperatures exceeding their glass transition temperatures. This work presents the results of the thermal model calibration efforts. A symmetric sandwich configuration was chosen that includes an inner and outer structural skin with a graphite-epoxy composite, Hexcel's AGP370-8H/3501-6 (AS4/3501-6), and a center epoxy-based syntactic core. 3M SC350G, that provides thermal protection. Each graphite-epoxy section consists of seven layers, each layer with a 0°, 90°, or +/-45° graphite fiber orientation. Three flat panels (0.305×0.483 m top view dimensions) using this sandwich construction were fabricated and exposed to an aerothermal environment in the Marshall Space Flight Center (MSFC) Improved Hot Gas Facility (IHGF). Each of these panels had ten interstitial thermocouples in the panel. The exact locations of the thermocouples and thickness of the different layers were determined by X-ray evaluation. A 1-D model was generated that used the outer surface IR measured temperature as a boundary condition, and the predicted temperatures were compared with the measured temperatures, calibrating the code. .

  9. Buckling Analysis of Angle-ply Composite and Sandwich Plates by Combination of Geometric Stiffness Matrix

    NASA Astrophysics Data System (ADS)

    Zhen, Wu; Wanji, Chen

    2007-05-01

    Buckling response of angle-ply laminated composite and sandwich plates are analyzed using the global-local higher order theory with combination of geometric stiffness matrix in this paper. This global-local theory completely fulfills the free surface conditions and the displacement and stress continuity conditions at interfaces. Moreover, the number of unknowns in this theory is independent of the number of layers in the laminate. Based on this global-local theory, a three-noded triangular element satisfying C1 continuity conditions has also been proposed. The bending part of this element is constructed from the concept of DKT element. In order to improve the accuracy of the analysis, a method of modified geometric stiffness matrix has been introduced. Numerical results show that the present theory not only computes accurately the buckling response of general laminated composite plates but also predicts the critical buckling loads of soft-core sandwiches. However, the global higher-order theories as well as first order theories might encounter some difficulties and overestimate the critical buckling loads for soft-core sandwich plates.

  10. Human umbilical cord mesenchymal stromal cells in a sandwich approach for osteochondral tissue engineering

    PubMed Central

    Wang, Limin; Zhao, Liang; Detamore, Michael S.

    2013-01-01

    Cell sources and tissue integration between cartilage and bone regions are critical to successful osteochondral regeneration. In this study, human umbilical cord mesenchymal stromal cells (hUCMSCs), derived from Wharton’s jelly, were introduced to the field of osteochondral tissue engineering and a new strategy for osteochondral integration was developed by sandwiching a layer of cells between chondrogenic and osteogenic constructs before suturing them together. Specifically, hUCMSCs were cultured in biodegradable poly-l-lactic acid scaffolds for 3 weeks in either chondrogenic or osteogenic medium to differentiate cells toward cartilage or bone lineages, respectively. A highly concentrated cell solution containing undifferentiated hUCMSCs was pasted onto the surface of the bone layer at week 3 and the two layers were then sutured together to form an osteochondral composite for another 3 week culture period. Chondrogenic and osteogenic differentiation was initiated during the first 3 weeks, as evidenced by the expression of type II collagen and runt-related transcription factor 2 genes, respectively, and continued with the increase of extracellular matrix during the last 3 weeks. Histological and immunohistochemical staining, such as for glycosaminoglycans, type I collagen and calcium, revealed better integration and transition of these matrices between two layers in the composite group containing sandwiched cells compared to other control composites. These results suggest that hUCMSCs may be a suitable cell source for osteochondral regeneration, and the strategy of sandwiching cells between two layers may facilitate scaffold and tissue integration. PMID:21953869

  11. Seismic load tests on reinforced concrete beam-column sandwich joints with strengthening measures

    NASA Astrophysics Data System (ADS)

    Yang, Zhi-Hong; Li, Ying-Min; Liu, Jian-Wei

    2009-12-01

    Reinforced concrete high-rise buildings with high strength concrete (HSC) column and normal strength concrete (NSC) floor are popular nowadays. For these structures, it is ineffective to construct beam-column joint with high strength concrete. So beam-column joints with normal strength concrete attract abundant attention and are strongly recommended in china recent years. In this paper, we refer to this type of joints as sandwich joints. In order to improve seismic behavior of sandwich joints with high stress, strengthening measures including addition of vertical dowels, addition of diagonal bars, and enhancement of joint constraint were proposed to apply to engineering practice recent years. In this paper, 6 full scale sandwich joint specimens were test under cyclic load to investigate the validity of strengthening measures. Tested specimens were consist of 1 specimen with additional vertical dowels, 2 specimens with additional diagonal bars, and 1 specimen with additional lateral beams, compared with 2 specimens without strengthening measures. Integrated seismic performances of these specimens were studied, such as load resistance behavior, deflection performance, ductility, energy dissipation behavior, beam bars anchorage capacity and so on. Based on the experimental results, the effect and mechanical behavior of strengthening measures were analyzed.

  12. Seismic load tests on reinforced concrete beam-column sandwich joints with strengthening measures

    NASA Astrophysics Data System (ADS)

    Yang, Zhi-hong; Li, Ying-min; Liu, Jian-wei

    2010-03-01

    Reinforced concrete high-rise buildings with high strength concrete (HSC) column and normal strength concrete (NSC) floor are popular nowadays. For these structures, it is ineffective to construct beam-column joint with high strength concrete. So beam-column joints with normal strength concrete attract abundant attention and are strongly recommended in china recent years. In this paper, we refer to this type of joints as sandwich joints. In order to improve seismic behavior of sandwich joints with high stress, strengthening measures including addition of vertical dowels, addition of diagonal bars, and enhancement of joint constraint were proposed to apply to engineering practice recent years. In this paper, 6 full scale sandwich joint specimens were test under cyclic load to investigate the validity of strengthening measures. Tested specimens were consist of 1 specimen with additional vertical dowels, 2 specimens with additional diagonal bars, and 1 specimen with additional lateral beams, compared with 2 specimens without strengthening measures. Integrated seismic performances of these specimens were studied, such as load resistance behavior, deflection performance, ductility, energy dissipation behavior, beam bars anchorage capacity and so on. Based on the experimental results, the effect and mechanical behavior of strengthening measures were analyzed.

  13. The Effects of Various Design Parameters on the Free Vibration of Doubly Curved Composite Sandwich Panels

    NASA Astrophysics Data System (ADS)

    CUNNINGHAM, P. R.; WHITE, R. G.; AGLIETTI, G. S.

    2000-02-01

    Sandwich panels have a very high stiffness to weight ratio, which makes them particularly useful in the aerospace industry where carbon fibre reinforced plastics and lightweight honeycomb cores are being used in the construction of floor panels, fairings and intake barrel panels. In the latter case, the geometry of the panels can be considered doubly curved. This paper presents an introduction to an ongoing study investigating the dynamic response prediction of acoustically excited composite sandwich panels which have double curvature. The final objective is to assess and hopefully produce an up to date set of acoustic fatigue design guidelines for this type of structure. The free vibration of doubly curved composite honeycomb sandwich panels is investigated here, both experimentally and theoretically, the latter using a commerically available finite element package. The design and manufacture of three test panels is covered before presenting experimental results for the natural frequencies of vibration with freely supported boundary conditions. Once validated against the experimental results, the theoretical investigation is extended to study the effects of changing radii of curvature, orthotropic properties of the core, and ply orientation on the natural frequencies of vibration of rectangular panels with various boundary conditions. The results from the parameter studies show curve veering, particularly when studying the effect of changing radii and ply orientation, however, it is not clear whether this phenomenon is due to the approximation method used or occurs in the physical system.

  14. The behavior of bonded doubler splices for composite sandwich panels

    NASA Technical Reports Server (NTRS)

    Zeller, T. A.; Weisahaar, T. A.

    1980-01-01

    The results of an investigation into the behavior of adhesively bonded doubler splices of two composite material sandwich panels are presented. The splices are studied from three approaches: analytical; numerical (finite elements); and experimental. Several parameters that characterize the splice are developed to determine their influence upon joint strength. These parameters are: doubler overlap length; core stiffness; laminate bending stiffness; the size of the gap between the spliced sandwich panels; and room and elevated temperatures. Similarities and contrasts between these splices and the physically similar single and double lap joints are discussed. The results of this investigation suggest several possible approaches to improving the strength of the sandwich splices.

  15. Wave propagation in sandwich panels with a poroelastic core.

    PubMed

    Liu, Hao; Finnveden, Svante; Barbagallo, Mathias; Arteaga, Ines Lopez

    2014-05-01

    Wave propagation in sandwich panels with a poroelastic core, which is modeled by Biot's theory, is investigated using the waveguide finite element method. A waveguide poroelastic element is developed based on a displacement-pressure weak form. The dispersion curves of the sandwich panel are first identified as propagating or evanescent waves by varying the damping in the panel, and wave characteristics are analyzed by examining their motions. The energy distributions are calculated to identify the dominant motions. Simplified analytical models are also devised to show the main physics of the corresponding waves. This wave propagation analysis provides insight into the vibro-acoustic behavior of sandwich panels lined with elastic porous materials.

  16. The Bending Strength, Internal Bonding and Thickness Swelling of a Five Layer Sandwiched Bamboo Particleboard

    NASA Astrophysics Data System (ADS)

    Jamaludin, M. A.; Bahari, S. A.; Nordin, K.; Soh, T. F. T.

    2010-03-01

    The demand for wood based material is increasing but the supply is decreasing. Therefore the price of these raw materials has increased. Bamboo provides an economically feasible alternative raw material for the wood based industry. Its properties are comparable to wood. It is also compatible with the existing processing technology. Bamboo is in abundance, easy to propagate and of short maturation period. Bamboo provides a cheaper alternative resource for the wood based industry. The development of new structural components from bamboo will widen its area of application from handicrafts to furniture and building components. In this study, five layer sandwiched bamboo particleboard were manufactured. The sandwiched Bamboo PB consists of a bamboo PB core, oil palm middle veneers and thin meranti surface veneers. The physical and mechanical properties of the bamboo sandwiched particleboards were tested in accordance to the BS-EN 317:1993 [1] and BS-EN 310:1993 [2], respectively. All the samples passed the standards. The modulus of elasticity was about 352% higher than the value specified in the BS standard, BS-EN 312-4:1996 [3]. The Internal bonding was about 23% higher than the general requirements specified in the standard. On the other hand, the thickness swelling was about 6% lower than the standard. No glue line failure was observed in the strength tests. Critical failures in the IB tests were observed in the particleboards. Tension failures were observed in the surface veneers in the bending tests. The five layer sandwiched bamboo particleboard can be used for light weight construction such as furniture, and wall and door panels in buildings.

  17. Measuring Moisture Levels in Graphite Epoxy Composite Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Nurge, Mark; Youngquist, Robert; Starr, Stanley

    2011-01-01

    Graphite epoxy composite (GEC) materials are used in the construction of rocket fairings, nose cones, interstage adapters, and heat shields due to their high strength and light weight. However, they absorb moisture depending on the environmental conditions they are exposed to prior to launch. Too much moisture absorption can become a problem when temperature and pressure changes experienced during launch cause the water to vaporize. The rapid state change of the water can result in structural failure of the material. In addition, heat and moisture combine to weaken GEC structures. Diffusion models that predict the total accumulated moisture content based on the environmental conditions are one accepted method of determining if the material strength has been reduced to an unacceptable level. However, there currently doesn t exist any field measurement technique to estimate the actual moisture content of a composite structure. A multi-layer diffusion model was constructed with Mathematica to predict moisture absorption and desorption from the GEC sandwich structure. This model is used in conjunction with relative humidity/temperature sensors both on the inside and outside of the material to determine the moisture levels in the structure. Because the core materials have much higher diffusivity than the face sheets, a single relative humidity measurement will accurately reflect the moisture levels in the core. When combined with an external relative humidity measurement, the model can be used to determine the moisture levels in the face sheets. Since diffusion is temperaturedependent, the temperature measurements are used to determine the diffusivity of the face sheets for the model computations.

  18. Forced vibration of a shear thickening fluid sandwich beam

    NASA Astrophysics Data System (ADS)

    Wei, Minghai; Hu, Gang; Jin, Lu; Lin, Kun; Zou, Dujian

    2016-05-01

    The forced vibration of a sandwich beam integrating a shear thickening fluid (STF) core and with conductive skins subjected to a periodic excitation was investigated theoretically in this study. The rheological properties of the STF material including viscosity, plasticity, and elasticity may be changed under the periodic vibration, and hence they were considered. The governing equation of motion was derived based on the complex stiffness method and some key parameters were derived based on the Timoshenko beam theory. Effects of the excitation frequency, the excitation amplitude, the excitation location, and the skin/core thickness ratio on the nature frequency of the sandwich beam were investigated. It was found that the STF core has a significant effect on the dynamic property of the sandwich beam. Based on the findings, integrating the STF core in a sandwich beam can reduce the vibration of the beam.

  19. The sandwich model: the 'music and dance' of therapeutic action.

    PubMed

    Harrison, Alexandra M

    2014-04-01

    My premise is that a 'layered' approach is necessary to understand the process of exchanges that result in therapeutic change. I imagine these processes occurring in three layers - although the number of domains in which change is taking place is actually infinite - such as in a sandwich. The top layer, or top slice of bread of the sandwich, represents a broad view of the change process; it is non-linear and includes the feature of uncertainty, a general principle of dynamic systems theory. The middle layer, or the meat of the sandwich, is explained by theories that are immediately and clinically useful to a therapist, such as psychoanalytic theories. These are primarily linear theories and use language and symbols to 'tell a story of what happened'. The bottom layer, or bottom slice of bread of the sandwich, is the micro-process; this layer includes the moment-to-moment patterns of coordinated rhythms that both communicate meaning and provide the essential scaffold for all higher-level change processes. The micro-process also requires a non-linear theory to make sense of its variability and emergent properties. Taking a bite out of the sandwich will include a 'polysemic bundle of communicative behaviors' (Harrison and Tronick, 2011). I will illustrate the 'sandwich model' with the clinical case of the analytic treatment of a 5 year-old boy.

  20. Modified Mode-I Cracked Sandwich Beam (CSB) Fracture Test

    NASA Technical Reports Server (NTRS)

    Smith, S. A.; Shivakumar, K. N.

    2001-01-01

    Five composite sandwich panels were fabricated using vacuum assisted resin transfer molding (VARTM). Four of these panels had E-glass/vinylester facesheets and one had carbon/epoxy facesheets. The sandwich panels had different density PVC foam cores. The four E-glass panels had core densities of 80, 100, 130, 200 kg/cu m. The sandwich with carbon/epoxy 3 facesheets had a core with density of 100 kg/cu m. Fracture tests were conducted using a modified Cracked Sandwich Beam (CSB) test configuration. Load displacement curves were obtained for loading and unloading of the specimens during crack growth. Various increments of crack growth were monitored. Critical Strain Energy Release Rates (SERR) were determined from the tests using the area method. The critical values of SERR can be considered the fracture toughness of the sandwich material. The fracture toughness ranged 367 J/sq m to 1350 J/sq m over the range of core densities. These results are compared to the Mode-I fracture toughness of the PVC foam core materials and values obtained for foam-cored sandwiches using the TSD specimen. Finite-element analyses (FEA) were performed for the test configuration and Strain Energy Release Rates were calculated using the Virtual Crack Closure Technique (VCCT). The SERR values determined from the FEA were scaled to the fracture loads, or critical loads, obtained from the modified CSB tests. These critical loads were in close agreement with the test values.

  1. A study of structurally efficient graphite-thermoplastic trapezoidal-corrugation sandwich and semi-sandwich panels

    NASA Technical Reports Server (NTRS)

    Jegley, Dawn C.

    1993-01-01

    The structural efficiency of compression-loaded trapezoidal-corrugation sandwich and semi-sandwich composite panels is studied to determine their weight savings potential. Sandwich panels with two identical face sheets and a trapezoidal corrugated core between them, and semi-sandwich panels with a corrugation attached to a single skin are considered. An optimization code is used to find the minimum weight designs for critical compressive load levels ranging from 3,000 to 24,000 lb/in. Graphite-thermoplastic panels based on the optimal minimum weight designs were fabricated and tested. A finite-element analysis of several test specimens was also conducted. The results of the optimization study, the finite-element analysis, and the experiments are presented.

  2. Enhanced Antibacterial Activity of Silver Nanoparticles/Halloysite Nanotubes/Graphene Nanocomposites with Sandwich-Like Structure

    PubMed Central

    Yu, Liang; Zhang, Yatao; Zhang, Bing; Liu, Jindun

    2014-01-01

    A sandwich-like antibacterial reagent (Ag/HNTs/rGO) was constructed through the direct growth of silver nanoparticles on the surface graphene-based HNTs nanosheets. Herein, various nanomaterials were combined by adhesion effect of DOPA after self-polymerization. Ag/HNTs/rGO posses enhanced antibacterial ability against E. coli and S. aureus compared with individual silver nanoparticles, rGO nanosheets or their nanocomposites. PMID:24722502

  3. Numerical analysis of impact-damaged sandwich composites

    NASA Astrophysics Data System (ADS)

    Hwang, Youngkeun

    Sandwich structures are used in a wide variety of structural applications due to their relative advantages over other conventional structural materials in terms of improved stability, weight savings, and ease of manufacture and repair. Foreign object impact damage in sandwich composites can result in localized damage to the facings, core, and core-facing interface. Such damage may result in drastic reductions in composite strength, elastic moduli, and durability and damage tolerance characteristics. In this study, physically-motivated numerical models have been developed for predicting the residual strength of impact-damaged sandwich composites comprised of woven-fabric graphite-epoxy facesheets and Nomex honeycomb cores subjected to compression-after-impact loading. Results from non-destructive inspection and destructive sectioning of damaged sandwich panels were used to establish initial conditions for damage (residual facesheet indentation, core crush dimension, etc.) in the numerical analysis. Honeycomb core crush test results were used to establish the nonlinear constitutive behavior for the Nomex core. The influence of initial facesheet property degradation and progressive loss of facesheet structural integrity on the residual strength of impact-damaged sandwich panels was examined. The influence of damage of various types and sizes, specimen geometry, support boundary conditions, and variable material properties on the estimated residual strength is discussed. Facesheet strains from material and geometric nonlinear finite element analyses correlated relatively well with experimentally determined values. Moreover, numerical predictions of residual strength are consistent with experimental observations. Using a methodology similar to that presented in this work, it may be possible to develop robust residual strength estimates for complex sandwich composite structural components with varying levels of in-service damage. Such studies may facilitate sandwich

  4. Impact damage analysis of balsawood sandwich composite materials

    NASA Astrophysics Data System (ADS)

    Abdalslam, Suof Omran

    In this study, a new composite sandwich structure with a balsa wood core (end grain and regular balsa) in conjunction with E-glass/epoxy face sheets was proposed, fabricated, impact tested, and modeled. The behavior of the sandwich structure under low velocity impact and compression after impact was investigated. Low velocity impact tests were carried out by drop-weight impact tower at different energy levels (8J-35J) to evaluate the impact response of the sandwich structure. Visual inspection, destructive and non destructive evaluation methods have been conducted. For the sandwich plate with end grain core, the damage was very clear and can be visually detected. However, the damage in regular balsa core was not clearly visible and destructive evaluation method was used. Compression testing was done after subjecting the specimens to impact testing. Impact test results; load-time, load-deflection history and energy absorption for sandwich composites with two different cores, end grain and regular balsa were compared and they were investigated at three different impact energies. The results show that the sandwich structures with end grain core are able to withstand impact loading better than the regular balsa core because the higher stiffness of end grain core informs of sustaining higher load and higher overall energy. The results obtained from compression after impact testing show that the strengths of sandwich composites with end grain and regular balsa cores were reduced about 40% and 52%, respectively, after impact. These results were presented in terms of stress-strain curves for both damaged and undamaged specimens. Finite element analysis was conducted on the sandwich composite structure using LS-DYNA code to simulate impact test. A 3- D finite element model was developed and appropriate material properties were given to each component. The computational model was developed to predict the response of sandwich composite under dynamic loading. The experimental

  5. Sound Transmission through Two Concentric Cylindrical Sandwich Shells

    NASA Technical Reports Server (NTRS)

    Tang, Yvette Y.; Silcox, Richard J.; Robinson, Jay H.

    1996-01-01

    This paper solves the problem of sound transmission through a system of two infinite concentric cylindrical sandwich shells. The shells are surrounded by external and internal fluid media and there is fluid (air) in the annular space between them. An oblique plane sound wave is incident upon the surface of the outer shell. A uniform flow is moving with a constant velocity in the external fluid medium. Classical thin shell theory is applied to the inner shell and first-order shear deformation theory is applied to the outer shell. A closed form for transmission loss is derived based on modal analysis. Investigations have been made for the impedance of both shells and the transmission loss through the shells from the exterior into the interior. Results are compared for double sandwich shells and single sandwich shells. This study shows that: (1) the impedance of the inner shell is much smaller than that of the outer shell so that the transmission loss is almost the same in both the annular space and the interior cavity of the shells; (2) the two concentric sandwich shells can produce an appreciable increase of transmission loss over single sandwich shells especially in the high frequency range; and (3) design guidelines may be derived with respect to the noise reduction requirement and the pressure in the annular space at a mid-frequency range.

  6. Self-assembled hetero-bimetallic sandwich with Ag-Ag bridging using a flexible two-arm ferrocene amide linker

    NASA Astrophysics Data System (ADS)

    Ni, Jia; Wei, Kai-Ju; Chen, Yao-Wen; Liu, Yangzhong

    2012-03-01

    The tetradentate ferrocenyl sandwich molecule N,N'-bis(di-2-pyridylamine)-1,1'-ferrocenedicarboxamine (bdpfa) has been designed and synthesized as an organometallic ligand in order to construct hetero-bimetallic architectures. By combining the flexibility from the arm-like molecule bdpfa with AgI ions, a novel complex [Ag2(bdpfa)](ClO4)2·(H2O)2 (1) was obtained. Single crystal X-ray analysis has revealed that complex 1 forms a hetero-trinuclear sandwich-type complex with Ag-Ag bridging. Furthermore, the preliminary electrochemical properties of the ligand and complex were investigated.

  7. A Double-Sandwich ELISA for Identification of Monoclonal Antibodies Suitable for Sandwich Immunoassays.

    PubMed

    Stanker, Larry H; Hnasko, Robert M

    2015-01-01

    The sandwich immunoassay (sELISA) is an invaluable technique for concentrating, detecting, and quantifying target antigens. The two critical components required are a capture antibody and a detection antibody, each binding a different epitope on the target antigen. The specific antibodies incorporated into the test define most of the performance parameters of any subsequent immunoassay regardless of the assay format: traditional ELISA, lateral-flow immunoassay, various bead-based assays, antibody-based biosensors, or the reporting label. Here we describe an approach for identifying monoclonal antibodies (mAbs) suitable for use as capture antibodies and detector antibodies in a sELISA targeting bacterial protein toxins. The approach was designed for early identification of monoclonal antibodies (mAbs), in the initial hybridoma screen.

  8. Academic Accreditation of Work-Based Learning in the Construction Environment

    ERIC Educational Resources Information Center

    McLernon, Tim; Hughes, David

    2004-01-01

    This paper examines the contribution of work-based learning (WBL) to the education of construction students. The research draws on the experiences of part-time students and students on sandwich courses in a School of the Built Environment. The sandwich courses include a year in industry as the penultimate year of a four-year programme. This WBL…

  9. Actively cooled plate fin sandwich structural panels for hypersonic aircraft

    NASA Technical Reports Server (NTRS)

    Smith, L. M.; Beuyukian, C. S.

    1979-01-01

    An unshielded actively cooled structural panel was designed for application to a hypersonic aircraft. The design was an all aluminum stringer-stiffened platefin sandwich structure which used a 60/40 mixture of ethylene glycol/water as the coolant. Eight small test specimens of the basic platefin sandwich concept and three fatigue specimens from critical areas of the panel design was fabricated and tested (at room temperature). A test panel representative of all features of the panel design was fabricated and tested to determine the combined thermal/mechanical performance and structural integrity of the system. The overall findings are that; (1) the stringer-stiffened platefin sandwich actively cooling concept results in a low mass design that is an excellent contender for application to a hypersonic vehicle, and (2) the fabrication processes are state of the art but new or modified facilities are required to support full scale panel fabrication.

  10. Sandwich complex-containing macromolecules: property tunability through versatile synthesis.

    PubMed

    Abd-El-Aziz, Alaa S; Agatemor, Christian; Etkin, Nola

    2014-03-01

    Sandwich complexes feature unique properties as the physical and electronic properties of a hydrocarbon ligand or its derivative are integrated into the physical, electronic, magnetic, and optical properties of a metal. Incorporation of these complexes into macromolecules results in intriguing physical, electrical, and optical properties that were hitherto unknown in organic-based macromolecules. These properties are tunable through well-designed synthetic strategies. This review surveys many of the synthetic approaches that have resulted in tuning the properties of sandwich complex-containing macromolecules. While the past two decades have seen an ever-growing number of research publications in this field, gaps remain to be filled. Thus, we expect this review to stimulate research interest towards bridging these gaps, which include the insolubility of some of these macromolecules as well as expanding the scope of the sandwich complexes.

  11. Vibration analysis and optimization of sandwich composite with curvilinear fibers

    NASA Astrophysics Data System (ADS)

    Honda, S.; Narita, Y.

    2016-09-01

    The present paper develops a shell element based on the refined zigzag theory (RZT) and applies it to the vibration analysis and optimization problem of the composite sandwich plate composed of CFRP skins and soft-cores. The RZT accepts large differences in layer stiffness, and requires less calculation effort than the layer-wise or three-dimensional theories. Numerical results revealed that the present method predicts vibration characteristics of composite sandwich plates with soft-core accurately. Then, shapes of reinforcing fibers in CFRP composite skins are optimized to maximize fundamental frequencies. As an optimizer, the particle swarm optimization (PSO) approach is employed since curvilinear fiber shapes are defined by continuous design variables. Obtained results showed that the composite sandwich with optimum curvilinear fiber shapes indicates higher fundamental frequencies compared with straight fibers.

  12. Response of fiber reinforced sandwich structures subjected to explosive loading

    SciTech Connect

    Perotti, Luigi E.; El Sayed, Tamer; Deiterding, Ralf; Ortiz, Michael

    2011-01-01

    The capability to numerically simulate the response of sandwich structures to explosive loading constitutes a powerful tool to analyze and optimize their design by investigating the influence of different parameters. In order to achieve this objective, the necessary models for foam core and fiber reinforced materials in finite kinematics have been developed together with a finite element scheme which includes C1 finite elements for shells and cohesive elements able to capture the fracture propagation in composite fiber reinforced materials. This computational capability has been used to investigate the response of fiber reinforced sandwich shells to explosive loading. Based on the dissipated fracture energy resulting from these simulations, a factorial design has been carried out to assess the effect of different parameters on the sandwich shell response creating a tool for its optimization.

  13. ['Sandwich PhD': considerations for a successful experience abroad].

    PubMed

    Salvetti, Marina de Goes; Bueno, Mariana; Gastaldo, Denise; Kimura, Amélia Fumiko; Pimenta, Cibele Andrucioli de Mattos

    2013-03-01

    International PhD internship, named "Sandwich PhD" in Brazil is an opportunity to improve research abilities, to become known in academic area and to establish and/or increase work opportunities in an international context. In this article, we describe key factors regarding the planning and development of the "Sandwich PhD" as experienced by professors and students involved in the collaboration between the School of Nursing, University of São Paulo and Lawrence S. Bloomberg Faculty of Nursing, University of Toronto, Canada. We also present the participation of PhD students' network as an alternative to the "Sandwich PhD". An international experience, when well-planned and developed correctly, promotes students' personal and professional development and favors the internationalization of Brazilian graduate programs and research groups.

  14. Extended high order sandwich panel theory for bending analysis of sandwich beams with carbon nanotube reinforced face sheets

    NASA Astrophysics Data System (ADS)

    Jedari Salami, S.

    2016-02-01

    Bending analysis of a sandwich beam with soft core and carbon nanotube reinforced composite (CNTRC) face sheets in the literature is presented based on Extended High order Sandwich Panel Theory (EHSAPT). Distribution of fibers through the thickness of the face sheets could be uniform or functionally graded (FG). In this theory the face sheets follow the first order shear deformation theory (FSDT). Besides, the two dimensional elasticity is used for the core. The field equations are derived via the Ritz based solution which is suitable for any essential boundary condition. The influences of boundary conditions on bending response of the sandwich panel with soft core and CNTRC face sheet are investigated. In each type of boundary condition the effect of distribution pattern of CNTRCs on many essential involved parameters of the sandwich beam with functionally graded carbon nanotube reinforced composite (FG- CNTRC) face sheets are studied in detail. Finally, experimental result have been compared with those obtained based on developed solution method. It is concluded that, the sandwich beam with X distribution figure of face sheets is the strongest with the smallest transverse displacement, and followed by the UD, O and ∧-ones, respectively.

  15. Performance of Novel Composites and Sandwich Structures Under Blast Loading

    NASA Astrophysics Data System (ADS)

    Shukla, Arun; Tekalur, Srinivasan Arjun; Gardner, Nate; Jackson, Matt; Wang, Erheng

    The current chapter focuses on the experimental observations of the resistance of different composite material systems to air blast loadings. These material systems include traditional two dimensional (2D) woven laminated composites, layered composites and sandwich composite materials. A controlled blast loading of pre-defined pressure magnitude and rise time were obtained using a shock tube apparatus. Rectangular plate elements of the desired material system were subjected to such a controlled blast loading and the effect of the blast loading on these elements were studied using optical and residual strength measurements. A high speed imaging technique was utilized to study the damage modes and mechanisms in real time. It was observed that layering of a conventional composite material with a soft visco-elastic polymer provided better blast resistance and sandwiching the polymer greatly enhanced its survivability under extreme air blast conditions. Aside from layering the conventional composite material with a soft visco-elastic polymer, it was observed that layering or grading the core can successfully mitigate the impact damage and thus improve the overall blast resistance as well. In addition to these, three dimensional (3D) woven skin and core reinforcements were introduced in the conventional sandwich composites and their effects on the blast resistance were studied experimentally. It was observed that these reinforcements also enhance the blast resistance of conventional sandwich composites by changing the mechanism of failure initiation and propagation in these sandwich structures. The energies during the blast loading process were estimated to illustrate the energy absorption and energy redistribution properties of the composite panels. The effect of pre-existing impact damage on the failure mechanisms in sandwich structures was also studied.

  16. Structural Performance of Eco-Core Sandwich Panels

    NASA Astrophysics Data System (ADS)

    Shivakumar, Kunigal; Chen, Huanchun

    Eco-Core, a fire resistant core material for sandwich composite structures developed under the US Navy (ONR) program, was used to study its performance as a sandwich beam with glass/vinyl ester face sheet. Performance of Eco-Core was compared with balsa and PVC core sandwich panels. Test specimens were designed to simulate shear, flexural, and edgewise compression loadings. These tests were conducted on Eco-Core as well as balsa and PVC sandwich composite specimens. Failure loads and modes were compared with each other and the analytical prediction. Both Eco-Core and balsa cored sandwich beams had similar failure modes in all three test conditions. In the case of transversely loaded (four-point) beams Eco-Core specimens failed by core shear for span/depth (S/d) ratio less than 4 and the failure mode changed to core tension for S/d >4. This is attributed to weak tensile strength of the core material. An expression for core tension failure load based on beam theory was derived. On the other hand, ductile materials like PVC failed by core indentation. Under edgewise compression, face sheet microbuckling and general buckling are the two potential failure modes for Eco-Core and balsa core sandwich composites. For specimen length/depth ratio L/d <7 the failure is by face sheet microbuckling, for 7 ≤L/d ≤13 the failure is a combination of face sheet microbuckling, debonding and buckling, and for L/d >13 the failure is by general buckling. Predictions from the existing equations agreed well with the experiment for both core materials. For PVC core, wrinkling/shear buckling and general buckling are the potential failure modes. For L/d ≤8.5 the failure is wrinkling and for L/d >8.5 the failure is general buckling.

  17. A novel method of measuring leaf epidermis and mesophyll stiffness shows the ubiquitous nature of the sandwich structure of leaf laminas in broad-leaved angiosperm species

    PubMed Central

    Onoda, Yusuke; Schieving, Feike; Anten, Niels P. R.

    2015-01-01

    Plant leaves commonly exhibit a thin, flat structure that facilitates a high light interception per unit mass, but may increase risks of mechanical failure when subjected to gravity, wind and herbivory as well as other stresses. Leaf laminas are composed of thin epidermis layers and thicker intervening mesophyll layers, which resemble a composite material, i.e. sandwich structure, used in engineering constructions (e.g. airplane wings) where high bending stiffness with minimum weight is important. Yet, to what extent leaf laminas are mechanically designed and behave as a sandwich structure remains unclear. To resolve this issue, we developed and applied a novel method to estimate stiffness of epidermis- and mesophyll layers without separating the layers. Across a phylogenetically diverse range of 36 angiosperm species, the estimated Young’s moduli (a measure of stiffness) of mesophyll layers were much lower than those of the epidermis layers, indicating that leaf laminas behaved similarly to efficient sandwich structures. The stiffness of epidermis layers was higher in evergreen species than in deciduous species, and strongly associated with cuticle thickness. The ubiquitous nature of sandwich structures in leaves across studied species suggests that the sandwich structure has evolutionary advantages as it enables leaves to be simultaneously thin and flat, efficiently capturing light and maintaining mechanical stability under various stresses. PMID:25675956

  18. A novel method of measuring leaf epidermis and mesophyll stiffness shows the ubiquitous nature of the sandwich structure of leaf laminas in broad-leaved angiosperm species.

    PubMed

    Onoda, Yusuke; Schieving, Feike; Anten, Niels P R

    2015-05-01

    Plant leaves commonly exhibit a thin, flat structure that facilitates a high light interception per unit mass, but may increase risks of mechanical failure when subjected to gravity, wind and herbivory as well as other stresses. Leaf laminas are composed of thin epidermis layers and thicker intervening mesophyll layers, which resemble a composite material, i.e. sandwich structure, used in engineering constructions (e.g. airplane wings) where high bending stiffness with minimum weight is important. Yet, to what extent leaf laminas are mechanically designed and behave as a sandwich structure remains unclear. To resolve this issue, we developed and applied a novel method to estimate stiffness of epidermis- and mesophyll layers without separating the layers. Across a phylogenetically diverse range of 36 angiosperm species, the estimated Young's moduli (a measure of stiffness) of mesophyll layers were much lower than those of the epidermis layers, indicating that leaf laminas behaved similarly to efficient sandwich structures. The stiffness of epidermis layers was higher in evergreen species than in deciduous species, and strongly associated with cuticle thickness. The ubiquitous nature of sandwich structures in leaves across studied species suggests that the sandwich structure has evolutionary advantages as it enables leaves to be simultaneously thin and flat, efficiently capturing light and maintaining mechanical stability under various stresses. PMID:25675956

  19. A novel method of measuring leaf epidermis and mesophyll stiffness shows the ubiquitous nature of the sandwich structure of leaf laminas in broad-leaved angiosperm species.

    PubMed

    Onoda, Yusuke; Schieving, Feike; Anten, Niels P R

    2015-05-01

    Plant leaves commonly exhibit a thin, flat structure that facilitates a high light interception per unit mass, but may increase risks of mechanical failure when subjected to gravity, wind and herbivory as well as other stresses. Leaf laminas are composed of thin epidermis layers and thicker intervening mesophyll layers, which resemble a composite material, i.e. sandwich structure, used in engineering constructions (e.g. airplane wings) where high bending stiffness with minimum weight is important. Yet, to what extent leaf laminas are mechanically designed and behave as a sandwich structure remains unclear. To resolve this issue, we developed and applied a novel method to estimate stiffness of epidermis- and mesophyll layers without separating the layers. Across a phylogenetically diverse range of 36 angiosperm species, the estimated Young's moduli (a measure of stiffness) of mesophyll layers were much lower than those of the epidermis layers, indicating that leaf laminas behaved similarly to efficient sandwich structures. The stiffness of epidermis layers was higher in evergreen species than in deciduous species, and strongly associated with cuticle thickness. The ubiquitous nature of sandwich structures in leaves across studied species suggests that the sandwich structure has evolutionary advantages as it enables leaves to be simultaneously thin and flat, efficiently capturing light and maintaining mechanical stability under various stresses.

  20. Approaches to Design and Evaluation of Sandwich Composites

    NASA Technical Reports Server (NTRS)

    Shivakumar, Kunigal; Raju, I. S. (Technical Monitor); Ambur, D. (Technical Monitor)

    2001-01-01

    This report describes research during the period June 15, 1997 to October 31, 2000. This grant yielded a low cast manufacturing of composite sandwich structures technology and characterization interfacial and subinterfacial cracks in foam core sandwich panels. The manufacturing technology is called the vacuum assisted resin transfer (VARTM). The VARTM is suitable for processing composite materials both at ambient and elevated temperatures and of unlimited component size. This technology has been successfully transferred to a small business fiber preform manufacturing company 3TEX located in Cary, North Carolina. The grant also supported one Ph.D, one M.S and a number of under graduate students, and nine publications and Presentations.

  1. Methods for Using Durable Adhesively Bonded Joints for Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Smeltzer, Stanley S., III (Inventor); Lundgren, Eric C. (Inventor)

    2016-01-01

    Systems, methods, and apparatus for increasing durability of adhesively bonded joints in a sandwich structure. Such systems, methods, and apparatus includes an first face sheet and an second face sheet as well as an insert structure, the insert structure having a first insert face sheet, a second insert face sheet, and an insert core material. In addition, sandwich core material is arranged between the first face sheet and the second face sheet. A primary bondline may be coupled to the face sheet(s) and the splice. Further, systems, methods, and apparatus of the present disclosure advantageously reduce the load, provide a redundant path, reduce structural fatigue, and/or increase fatigue life.

  2. Detection of entrapped moisture in honeycomb sandwich structures

    NASA Technical Reports Server (NTRS)

    Hallmark, W. B.

    1967-01-01

    Thermal neutron moisture detection system detects entrapped moisture in intercellular areas of bonded honeycomb sandwich structures. A radium/beryllium fast neutron source bombards a specimen. The emitted thermal neutrons from the target nucleus are detected and counted by a boron trifluoride thermal neutron detector.

  3. Dielectrophoretic behaviours of microdroplet sandwiched between LN substrates

    NASA Astrophysics Data System (ADS)

    Chen, Lipin; Li, Shaobei; Fan, Bolin; Yan, Wenbo; Wang, Donghui; Shi, Lihong; Chen, Hongjian; Ban, Dechao; Sun, Shihao

    2016-07-01

    We demonstrate a sandwich configuration for microfluidic manipulation in LiNbO3 platform based on photovoltaic effect, and the behaviours of dielectric microdroplet under this sandwich configuration are investigated. It is found that the microdroplet can generate in the form of liquid bridge inside the LiNbO3-based sandwich structure under the governing dielectrophoretic force, and the dynamic process of microdroplet generation highly depends on the substrate combinations. Dynamic features found for different combinations are explained by the different electrostatic field distribution basing on the finite-element simulation results. Moreover, the electrostatic field required by the microdroplet generation is estimated through meniscus evolution and it is found in good agreement with the simulated electrostatic field inside the sandwich gap. Several kinds of microdroplet manipulations are attempted in this work. We suggest that the local dielectrophoretic force acting on the microdroplet depends on the distribution of the accumulated irradiation dosage. Without using any additional pumping or jetting actuator, the microdroplet can be step-moved, deformed or patterned by the inconsecutive dot-irradiation scheme, as well as elastically stretched out and back or smoothly guided in a designed pass by the consecutive line-irradiation scheme.

  4. Load characteristics of high power sandwich piezoelectric ultrasonic transducers.

    PubMed

    Shuyu, Lin

    2005-03-01

    Based on the equivalent circuit theory, the load characteristics of high power piezoelectric ultrasonic sandwich transducers are studied. Two types of loads are studied. One is liquid load as in ultrasonic cleaning, and the other is solid load as in ultrasonic drilling and machining. The effect of load and structure of the transducer on the resonance frequency of the transducer is analyzed. It is shown that the effect of load on the resonance frequency of sandwich transducers with different structures is different. For liquid load as in ultrasonic cleaning, the effect of the load on the resonance frequency of the sandwich transducer with symmetrical structure is the largest. It is the smallest for the transducer with its displacement node in the back metal cylinder. For solid load as in ultrasonic drilling and machining, the effect of the load on the resonance frequency of the sandwich transducer with its displacement node in the front metal cylinder is the largest. It is also the smallest for the transducer with its displacement node in the back metal cylinder. On the other hand, for some applications, such as ultrasonic drilling, when the lateral dimension of the tool is much less than that of the transducer, its effect on the resonance frequency of the transducer is small. The conclusions are useful in designing vibrating systems for different ultrasonic applications.

  5. Star cell type core configuration for structural sandwich materials

    DOEpatents

    Christensen, Richard M.

    1995-01-01

    A new pattern for cellular core material used in sandwich type structural materials. The new pattern involves star shaped cells intermixed with hexagonal shaped cells. The new patterned cellular core material includes star shaped cells interconnected at points thereof and having hexagonal shape cells positioned adjacent the star points. The new pattern allows more flexibility and can conform more easily to curved shapes.

  6. Dielectrophoretic behaviours of microdroplet sandwiched between LN substrates.

    PubMed

    Chen, Lipin; Li, Shaobei; Fan, Bolin; Yan, Wenbo; Wang, Donghui; Shi, Lihong; Chen, Hongjian; Ban, Dechao; Sun, Shihao

    2016-01-01

    We demonstrate a sandwich configuration for microfluidic manipulation in LiNbO3 platform based on photovoltaic effect, and the behaviours of dielectric microdroplet under this sandwich configuration are investigated. It is found that the microdroplet can generate in the form of liquid bridge inside the LiNbO3-based sandwich structure under the governing dielectrophoretic force, and the dynamic process of microdroplet generation highly depends on the substrate combinations. Dynamic features found for different combinations are explained by the different electrostatic field distribution basing on the finite-element simulation results. Moreover, the electrostatic field required by the microdroplet generation is estimated through meniscus evolution and it is found in good agreement with the simulated electrostatic field inside the sandwich gap. Several kinds of microdroplet manipulations are attempted in this work. We suggest that the local dielectrophoretic force acting on the microdroplet depends on the distribution of the accumulated irradiation dosage. Without using any additional pumping or jetting actuator, the microdroplet can be step-moved, deformed or patterned by the inconsecutive dot-irradiation scheme, as well as elastically stretched out and back or smoothly guided in a designed pass by the consecutive line-irradiation scheme. PMID:27383027

  7. Modular container assembled from fiber reinforced thermoplastic sandwich panels

    DOEpatents

    Donnelly, Mathew William; Kasoff, William Andrew; Mcculloch, Patrick Carl; Williams, Frederick Truman

    2007-12-25

    An improved, load bearing, modular design container structure assembled from thermoformed FRTP sandwich panels in which is utilized the unique core-skin edge configuration of the present invention in consideration of improved load bearing performance, improved useful load volume, reduced manufacturing costs, structural weight savings, impact and damage tolerance and repair and replace issues.

  8. Methods for Assessing Honeycomb Sandwich Panel Wrinkling Failures

    NASA Technical Reports Server (NTRS)

    Zalewski, Bart F.; Dial, William B.; Bednarcyk, Brett A.

    2012-01-01

    Efficient closed-form methods for predicting the facesheet wrinkling failure mode in sandwich panels are assessed. Comparisons were made with finite element model predictions for facesheet wrinkling, and a validated closed-form method was implemented in the HyperSizer structure sizing software.

  9. Dielectrophoretic behaviours of microdroplet sandwiched between LN substrates

    PubMed Central

    Chen, Lipin; Li, Shaobei; Fan, Bolin; Yan, Wenbo; Wang, Donghui; Shi, Lihong; Chen, Hongjian; Ban, Dechao; Sun, Shihao

    2016-01-01

    We demonstrate a sandwich configuration for microfluidic manipulation in LiNbO3 platform based on photovoltaic effect, and the behaviours of dielectric microdroplet under this sandwich configuration are investigated. It is found that the microdroplet can generate in the form of liquid bridge inside the LiNbO3-based sandwich structure under the governing dielectrophoretic force, and the dynamic process of microdroplet generation highly depends on the substrate combinations. Dynamic features found for different combinations are explained by the different electrostatic field distribution basing on the finite-element simulation results. Moreover, the electrostatic field required by the microdroplet generation is estimated through meniscus evolution and it is found in good agreement with the simulated electrostatic field inside the sandwich gap. Several kinds of microdroplet manipulations are attempted in this work. We suggest that the local dielectrophoretic force acting on the microdroplet depends on the distribution of the accumulated irradiation dosage. Without using any additional pumping or jetting actuator, the microdroplet can be step-moved, deformed or patterned by the inconsecutive dot-irradiation scheme, as well as elastically stretched out and back or smoothly guided in a designed pass by the consecutive line-irradiation scheme. PMID:27383027

  10. Buckling Design and Imperfection Sensitivity of Sandwich Composite Launch-Vehicle Shell Structures

    NASA Technical Reports Server (NTRS)

    Schultz, Marc R.; Sleight, David W.; Myers, David E.; Waters, W. Allen, Jr.; Chunchu, Prasad B.; Lovejoy, Andrew W.; Hilburger, Mark W.

    2016-01-01

    Composite materials are increasingly being considered and used for launch-vehicle structures. For shell structures, such as interstages, skirts, and shrouds, honeycomb-core sandwich composites are often selected for their structural efficiency. Therefore, it is becoming increasingly important to understand the structural response, including buckling, of sandwich composite shell structures. Additionally, small geometric imperfections can significantly influence the buckling response, including considerably reducing the buckling load, of shell structures. Thus, both the response of the theoretically perfect structure and the buckling imperfection sensitivity must be considered during the design of such structures. To address the latter, empirically derived design factors, called buckling knockdown factors (KDFs), were developed by NASA in the 1960s to account for this buckling imperfection sensitivity during design. However, most of the test-article designs used in the development of these recommendations are not relevant to modern launch-vehicle constructions and material systems, and in particular, no composite test articles were considered. Herein, a two-part study on composite sandwich shells to (1) examine the relationship between the buckling knockdown factor and the areal mass of optimized designs, and (2) to interrogate the imperfection sensitivity of those optimized designs is presented. Four structures from recent NASA launch-vehicle development activities are considered. First, designs optimized for both strength and stability were generated for each of these structures using design optimization software and a range of buckling knockdown factors; it was found that the designed areal masses varied by between 6.1% and 19.6% over knockdown factors ranging from 0.6 to 0.9. Next, the buckling imperfection sensitivity of the optimized designs is explored using nonlinear finite-element analysis and the as-measured shape of a large-scale composite cylindrical

  11. Lamb wave dispersion in a PZT/metal/PZT sandwich plate with imperfect interface

    NASA Astrophysics Data System (ADS)

    Kurt, Ilkay; Akbarov, Surkay D.; Sezer, Semih

    2016-07-01

    The Lamb wave dispersion in a PZT/Metal/PZT sandwich plate is investigated by employing the exact linear equations of electro-elastic waves in piezoelectric materials within the scope of the plane-strain state. It is assumed that at the interfaces between the piezoelectric face layers and metal core layer, shear-spring and normal-spring type imperfect conditions are satisfied. The degree of this imperfectness is estimated through the corresponding shear-spring and normal-spring type parameters which appear in the contact condition characterizing the transverse and normal displacements' discontinuity. The corresponding dispersion equation is derived, and as a result of the numerical solution to this equation, the dispersion curves are constructed for the first and second lowest modes in the cases where the material of the face layers is PZT and the material of the middle layer is Steel (St). Consequently, for the PZT/St/PZT sandwich plate, the study of the influence of the problem parameters such as the piezoelectric and dielectric constants, layer thickness ratios, non-dimensional shear-spring, and normal-spring type parameters, is carried out. In particular, it is established that the imperfectness of the contact between the layers of the plate causes a decrease in the values of the wave propagation velocity.

  12. Sandwich-like graphene/polypyrrole/layered double hydroxide nanowires for high-performance supercapacitors

    NASA Astrophysics Data System (ADS)

    Li, Xuejin; Zhang, Yu; Xing, Wei; Li, Li; Xue, Qingzhong; Yan, Zifeng

    2016-11-01

    Electrode design in nanoscale is considered to be ultra-important to construct a superb capacitor. Herein, a sandwich-like composite was made by combining graphene/polypyrrole (GPPY) with nickel-aluminum layered double hydroxide nanowires (NiAl-NWs) via a facile hydrothermal method. This sandwich-like architecture is promising in energy storage applications due to three unique features: (1) the conductive GPPY substrate not only effectively prevents the layered double hydroxides species from aggregating, but also considerably facilitates the electron transmission; (2) the ultrathin NiAl-NWs ensure a maximum exposure of active Ni2+, which can improve the efficiency of rapid redox reactions even at high current densities; (3) the sufficient space between anisotropic NiAl-NWs can accommodate a large volume change of the nanowires to avoid their collapse or distortion during the reduplicative redox reactions. Keeping all these unique features in mind, when the as-prepared composite was applied to supercapacitors, it presented an enhanced capacitive performance in terms of high specific capacitance (845 F g-1), excellent rate performance (67% retained at 30 A g-1), remarkable cyclic stability (92% maintained after 5000 cycles) and large energy density (40.1 Wh·Kg-1). This accomplishment in the present work inspires an innovative strategy of nanoscale electrode design for high-rate performance supercapacitor electrodes containing pseuducapacitive metal oxide.

  13. Compression Response of a Sandwich Fuselage Keel Panel With and Without Damage

    NASA Technical Reports Server (NTRS)

    McGowan, David M.; Ambur, Damodar R.

    1997-01-01

    Results are presented from an experimental and analytical study of a sandwich fuselage keel panel with and without damage. The fuselage keel panel is constructed of graphite-epoxy skins bonded to a honeycomb core, and is representative of a highly loaded fuselage keel structure. The face sheets of the panel contain several terminated or dropped plies along the length of the panel. The results presented provide a better understanding of the load distribution in damaged and undamaged thick-face-sheet composite sandwich structure with dropped plies and of the failure mechanisms of such structure in the presence of low-speed impact damage and discrete-source damage. The impact-damage condition studied corresponds to barely visible impact damage (BVID), and the discrete-source damage condition studied is a notch machined through both face sheets. Results are presented from an impact-damage screening study conducted on another panel of the same design to determine the impact energy necessary to inflict BVID on the panel. Results are presented from compression tests of the panel in three conditions: undamaged; BVID in two locations; and BVID in two locations and a notch through both face sheets. Surface strains in the face sheets of the undamaged panel and the notched panel obtained experimentally are compared with finite element analysis results. The experimental and analytical results suggest that for the damage conditions studied, discrete-source damage influences the structural performance more than BVID.

  14. Comparative Study of Permeatal Sandwich Tympanoplasty and Postaural Underlay Technique

    PubMed Central

    Nagpure, Prakash Shankarrao; Yadav, Manish; Chavan, Sushil

    2016-01-01

    Introduction Tympanoplasty is the most common operation performed by an Otolaryngologist right from the period of residency. During the last hundred years various modifications in this surgical technique have come up because of continued efforts made by otologists all over the world to achieve the best surgical outcome. Aim To compare the graft take up and complications associated with the Permeatal Sandwich Tympanoplasty performed with the use of Otoendoscope and traditional Postaural Underlay technique of Tympanoplasty from 1st September 2014 to 30th August 2015. Materials and Methods Patients attending the ENT OPD, suffering from Chronic Suppurative Otitis Media (CSOM) were selected on the basis of type of perforation and their workup was done to assess the candidature for tympanoplasty. Results A total of 100 patients were included in the study and the overall graft take was 92.3% in cases of Permeatal Sandwich technique as compared to 64.58% in the case of postaural underlay technique, with a majority of the failures in the large central perforation group rendering a p = 0.021 for patients operated for Large perforations, p = 0.036 for moderate perforations and p = 0.476 for small perforations. The overall p = 0.000649 which is highly significant. On comparing the complications there were only 2 cases in Permeatal Sandwich Technique compared to 25 cases in Postaural Underlay technique rendering a highly significant p-value 0f 0.000000348. There was a difference in hearing improvement with majority of the cases improving to the range of 16-25 dB in Permeatal Sandwich technique compared to 26-45 dB in Postaural Underlay technique. Conclusion Permeatal Sandwich technique produce much better results when compared with Postaural approach in terms of graft take up, complications and hearing improvement. PMID:27190842

  15. High-performance ultraviolet photodetectors based on solution-grown ZnS nanobelts sandwiched between graphene layers

    PubMed Central

    Kim, Yeonho; Kim, Sang Jin; Cho, Sung-Pyo; Hong, Byung Hee; Jang, Du-Jeon

    2015-01-01

    Ultraviolet (UV) light photodetectors constructed from solely inorganic semiconductors still remain unsatisfactory because of their low electrical performances. To overcome this limitation, the hybridization is one of the key approaches that have been recently adopted to enhance the photocurrent. High-performance UV photodetectors showing stable on-off switching and excellent spectral selectivity have been fabricated based on the hybrid structure of solution-grown ZnS nanobelts and CVD-grown graphene. Sandwiched structures and multilayer stacking strategies have been applied to expand effective junction between graphene and photoactive ZnS nanobelts. A multiply sandwich-structured photodetector of graphene/ZnS has shown a photocurrent of 0.115 mA under illumination of 1.2 mWcm−2 in air at a bias of 1.0 V, which is higher 107 times than literature values. The multiple-sandwich structure of UV-light sensors with graphene having high conductivity, flexibility, and impermeability is suggested to be beneficial for the facile fabrication of UV photodetectors with extremely efficient performances. PMID:26197784

  16. Novel self-assembled sandwich nanomedicine for NIR-responsive release of NO

    PubMed Central

    Fan, Jing; He, Qianjun; Liu, Yi; Ma, Ying; Fu, Xiao; Liu, Yijing; Huang, Peng; He, Nongyue; Chen, Xiaoyuan

    2015-01-01

    A novel sandwich nanomedicine (GO-BNN6) for near-infrared (NIR) light responsive release of nitric oxide (NO) has been constructed by self-assembling of graphene oxide (GO) nanosheets and a NO donor BNN6 through the π-π stacking interaction. GO-BNN6 nanomedicine has an extraordinarily high drug loading capacity (1.2 mg BNN6 per mg GO), good thermal stability, and high NIR responsiveness. The NO release from GO-BNN6 can be easily triggered and effectively controlled by adjusting the switching, irradiation time and power density of NIR laser. The intracellular NIR-responsive release of NO from GO-BNN6 nanomedicine causes a remarkable anti-cancer effect. PMID:26568270

  17. A novel self-assembled sandwich nanomedicine for NIR-responsive release of NO.

    PubMed

    Fan, Jing; He, Nongyue; He, Qianjun; Liu, Yi; Ma, Ying; Fu, Xiao; Liu, Yijing; Huang, Peng; Chen, Xiaoyuan

    2015-12-21

    A novel sandwich nanomedicine (GO-BNN6) for near-infrared (NIR) light responsive release of nitric oxide (NO) has been constructed by self-assembly of graphene oxide (GO) nanosheets and a NO donor BNN6 through the π-π stacking interaction. The GO-BNN6 nanomedicine has an extraordinarily high drug loading capacity (1.2 mg BNN6 per mg GO), good thermal stability, and high NIR responsiveness. The NO release from GO-BNN6 can be easily triggered and effectively controlled by adjusting the switching, irradiation time and power density of NIR laser. The intracellular NIR-responsive release of NO from the GO-BNN6 nanomedicine causes a remarkable anti-cancer effect.

  18. Visual distraction and visuo-spatial memory: a sandwich effect.

    PubMed

    Tremblay, Sébastien; Nicholls, Alastair P; Parmentier, Fabrice B R; Jones, Dylan M

    2005-01-01

    The functional characteristics of visuo-spatial serial memory and its sensitivity to irrelevant visual information are examined in the present study, through the investigation of the sandwich effect (e.g., Hitch, 1975). The memory task was one of serial recall for the position of a sequence of seven spatially and temporally separated dots. The presence of irrelevant dots interpolated with to-be-remembered dots affected performance over most serial positions (Experiment 1) but that effect was significantly reduced when the interpolated dots were distinct from the to-be-remembered dots by colour and shape (Experiment 2). Parallels are made between verbal and spatial serial memory, and the reduction of the sandwich effect is discussed in terms of the contribution of perceptual organisation and attentional factors in short-term memory.

  19. Vibration Characteristics of Partially Covered Double-Sandwich Cantilever Beam

    NASA Technical Reports Server (NTRS)

    Chen, Qinghua; Levy, Cesar

    1996-01-01

    The differential equations of motion together with the boundary conditions for a partially covered, double-sandwich cantilever beam are derived. Bending and extension, rotational and longitudinal inertia of damping layers, and shear deformation and rotational and longitudinal inertia of the constraining layers and the primary beam are included in the equations. The theory is applicable for long as well as short, soft, or stiff damping layer, double-sandwich beams. Also, the effects of different parameters on the system loss factor and resonance frequency are discussed. Differences are found to exist with the previous beam model (called the Euler beam model) when the damping layers are stiff, when the thickness of the damping layer is large compared to the primary-beam thickness, and in the case of higher modes of vibration.

  20. Fatigue and impact properties of metal honeycomb sandwich panel

    NASA Astrophysics Data System (ADS)

    Zou, Guang ping; Lu, Jie; Liang, Jun; Chang, Zhong liang

    2008-11-01

    Honeycomb sandwich structures are significant to be used as applied to thermal protection system on reusable launch vehicle. In this paper the fatigue and impact properties of a novel metallic thermal protection material have been investigated and predicted at room temperature. A series of strength tests are carried out to obtain parameters firstly for further experiments. A set of tension-tension stress fatigue tests and impact tests based on split-Hopkinson pressure bar are carried out. Different high strain rate impact experiments are accomplished. The curves of dynamical stress, strain and strain rate are obtained. Also the cell units images after impact are presented. The results show the fatigue properties of honeycomb sandwich panels are comparatively better. And it has the advantages of anti-impact resistance and high, energy absorption capability.

  1. Bismaleimide resins for flame resistant honeycomb sandwich panels

    NASA Technical Reports Server (NTRS)

    Stenzenberger, H. D.

    1978-01-01

    Bismaleimide resins are prime candidates for nonflammable aircraft interior panels. Three resin types with different structures and processing characteristics were formulated. Resin M 751 was used to fabricate 100 kg of glass fabric prepregs which were used for the preparation of face sheets for honeycomb sandwich panels. Prepreg characteristics and curing cycles for laminate fabrication are provided. In order to advance beyond the current solvent resin technology for fibre and fabric impregnation, a hot melt solvent-less resin system was prepared and characterized. Preliminary tests were performed to develop a wet bonding process for the fabrication of advanced sandwich honeycomb panels by use of polybismaleimide glass fabric face sheets and polybismaleimide Nomex honeycomb core. B-stage material was used for both the core and the face sheet, providing flatwise tensile properties equivalent to those obtained by the state-of-the-art 3-step process which includes an epoxy adhesive resin.

  2. Development of lightweight graphite/polyimide sandwich panels.

    NASA Technical Reports Server (NTRS)

    Poesch, J. G.

    1972-01-01

    Lightweight graphite/polyimide composite honeycomb core and sandwich panels were fabricated and tested. Honeycomb cores of 1/4-in. and 3/8-in. cell sizes of hexagonal configuration were produced from thin plus or minus 45 deg cross plied sheets of prepreg producing core weights between 1.8 and 3.6 lb/cu ft. Thin gauge prepreg using Hercules graphite tow and Monsanto Skybond 710 polyimide resin were manufactured to produce cured ply thicknesses of 0.001 to 0.002 in. Graphite core properties measured at temperatures from -150 to 600 F are reported. Core properties which are superior to available materials were obtained. Sandwich panels weighing less than 0.5 lb/sq ft were designed and fabricated which meet the support structure loads for the shuttle orbiter thermal protection system.

  3. A novel self-assembled sandwich nanomedicine for NIR-responsive release of NO

    NASA Astrophysics Data System (ADS)

    Fan, Jing; He, Nongyue; He, Qianjun; Liu, Yi; Ma, Ying; Fu, Xiao; Liu, Yijing; Huang, Peng; Chen, Xiaoyuan

    2015-11-01

    A novel sandwich nanomedicine (GO-BNN6) for near-infrared (NIR) light responsive release of nitric oxide (NO) has been constructed by self-assembly of graphene oxide (GO) nanosheets and a NO donor BNN6 through the π-π stacking interaction. The GO-BNN6 nanomedicine has an extraordinarily high drug loading capacity (1.2 mg BNN6 per mg GO), good thermal stability, and high NIR responsiveness. The NO release from GO-BNN6 can be easily triggered and effectively controlled by adjusting the switching, irradiation time and power density of NIR laser. The intracellular NIR-responsive release of NO from the GO-BNN6 nanomedicine causes a remarkable anti-cancer effect.A novel sandwich nanomedicine (GO-BNN6) for near-infrared (NIR) light responsive release of nitric oxide (NO) has been constructed by self-assembly of graphene oxide (GO) nanosheets and a NO donor BNN6 through the π-π stacking interaction. The GO-BNN6 nanomedicine has an extraordinarily high drug loading capacity (1.2 mg BNN6 per mg GO), good thermal stability, and high NIR responsiveness. The NO release from GO-BNN6 can be easily triggered and effectively controlled by adjusting the switching, irradiation time and power density of NIR laser. The intracellular NIR-responsive release of NO from the GO-BNN6 nanomedicine causes a remarkable anti-cancer effect. Electronic supplementary information (ESI) available: NMR and MS data of BNN6, stability of GO-BNN6, NIR-responsibility comparison of BNN6 and GO-BNN6, and NMR spectrum of RBSP. See DOI: 10.1039/c5nr06630a

  4. Star cell type core configuration for structural sandwich materials

    DOEpatents

    Christensen, R.M.

    1995-08-01

    A new pattern for cellular core material used in sandwich type structural materials is disclosed. The new pattern involves star shaped cells intermixed with hexagonal shaped cells. The new patterned cellular core material includes star shaped cells interconnected at points thereof and having hexagonal shape cells positioned adjacent the star points. The new pattern allows more flexibility and can conform more easily to curved shapes. 3 figs.

  5. Graphene Sandwiched Mesostructured Li-Ion Battery Electrodes.

    PubMed

    Liu, Jinyun; Zheng, Qiye; Goodman, Matthew D; Zhu, Haoyue; Kim, Jinwoo; Krueger, Neil A; Ning, Hailong; Huang, Xingjiu; Liu, Jinhuai; Terrones, Mauricio; Braun, Paul V

    2016-09-01

    A deterministic graphene-sandwiched Li-ion battery electrode consisting of an integrated 3D mesostructure of electrochemically active materials and graphene is presented. As demonstrations, electrodes with active nanomaterials that coat (V2 O5 @graphene@V2 O5 cathode) or are coated by (graphene@Si@graphene anode) graphene are fabricated. These electrodes exhibit high capacities and ultralong cycle lives (the cathode can be cycled over 2000 times with minimal capacity fade). PMID:27383465

  6. Graphene Sandwiched Mesostructured Li-Ion Battery Electrodes.

    PubMed

    Liu, Jinyun; Zheng, Qiye; Goodman, Matthew D; Zhu, Haoyue; Kim, Jinwoo; Krueger, Neil A; Ning, Hailong; Huang, Xingjiu; Liu, Jinhuai; Terrones, Mauricio; Braun, Paul V

    2016-09-01

    A deterministic graphene-sandwiched Li-ion battery electrode consisting of an integrated 3D mesostructure of electrochemically active materials and graphene is presented. As demonstrations, electrodes with active nanomaterials that coat (V2 O5 @graphene@V2 O5 cathode) or are coated by (graphene@Si@graphene anode) graphene are fabricated. These electrodes exhibit high capacities and ultralong cycle lives (the cathode can be cycled over 2000 times with minimal capacity fade).

  7. Structural modeling of sandwich structures with lightweight cellular cores

    NASA Astrophysics Data System (ADS)

    Liu, T.; Deng, Z. C.; Lu, T. J.

    2007-10-01

    An effective single layered finite element (FE) computational model is proposed to predict the structural behavior of lightweight sandwich panels having two dimensional (2D) prismatic or three dimensional (3D) truss cores. Three different types of cellular core topology are considered: pyramidal truss core (3D), Kagome truss core (3D) and corrugated core (2D), representing three kinds of material anisotropy: orthotropic, monoclinic and general anisotropic. A homogenization technique is developed to obtain the homogenized macroscopic stiffness properties of the cellular core. In comparison with the results obtained by using detailed FE model, the single layered computational model can give acceptable predictions for both the static and dynamic behaviors of orthotropic truss core sandwich panels. However, for non-orthotropic 3D truss cores, the predictions are not so well. For both static and dynamic behaviors of a 2D corrugated core sandwich panel, the predictions derived by the single layered computational model is generally acceptable when the size of the unit cell varies within a certain range, with the predictions for moderately strong or strong corrugated cores more accurate than those for weak cores.

  8. Size Effects in Impact Damage of Composite Sandwich Panels

    NASA Technical Reports Server (NTRS)

    Dobyns, Alan; Jackson, Wade

    2003-01-01

    Panel size has a large effect on the impact response and resultant damage level of honeycomb sandwich panels. It has been observed during impact testing that panels of the same design but different panel sizes will show large differences in damage when impacted with the same impact energy. To study this effect, a test program was conducted with instrumented impact testing of three different sizes of sandwich panels to obtain data on panel response and residual damage. In concert with the test program. a closed form analysis method was developed that incorporates the effects of damage on the impact response. This analysis method will predict both the impact response and the residual damage of a simply-supported sandwich panel impacted at any position on the panel. The damage is incorporated by the use of an experimental load-indentation curve obtained for the face-sheet/honeycomb and indentor combination under study. This curve inherently includes the damage response and can be obtained quasi-statically from a rigidly-backed specimen or a specimen with any support conditions. Good correlation has been obtained between the test data and the analysis results for the maximum force and residual indentation. The predictions can be improved by using a dynamic indentation curve. Analyses have also been done using the MSC/DYTRAN finite element code.

  9. Novel MRE/CFRP sandwich structures for adaptive vibration control

    NASA Astrophysics Data System (ADS)

    Kozlowska, J.; Boczkowska, A.; Czulak, A.; Przybyszewski, B.; Holeczek, K.; Stanik, R.; Gude, M.

    2016-03-01

    The aim of this work was the development of sandwich structures formed by embedding magnetorheological elastomers (MRE) between constrained layers of carbon fibre-reinforced plastic (CFRP) laminates. The MREs were obtained by mechanical stirring of a reactive mixture of substrates with carbonyl-iron particles, followed by orienting the particles into chains under an external magnetic field. Samples with particle volume fractions of 11.5% and 33% were examined. The CFRP/MRE sandwich structures were obtained by compressing MREs samples between two CFRP laminates composed. The used A.S.SET resin was in powder form and the curing process was carried out during pressing with MRE. The microstructure of the manufactured sandwich beams was inspected using SEM. Moreover, the rheological and damping properties of the examined materials with and without a magnetic field were experimentally investigated. In addition, the free vibration responses of the adaptive three-layered MR beams were studied at different fixed magnetic field levels. The free vibration tests revealed that an applied non-homogeneous magnetic field causes a shift in natural frequency values and a reduction in the vibration amplitudes of the CFRP/MRE adaptive beams. The reduction in vibration amplitude was attributed mainly to the stiffening effect of the MRE core and only a minor contribution was made by the enhanced damping capacity, which was evidenced by the variation in damping ratio values.

  10. Hypervelocity Impact Evaluation of Metal Foam Core Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Yasensky, John; Christiansen, Eric L.

    2007-01-01

    A series of hypervelocity impact (HVI) tests were conducted by the NASA Johnson Space Center (JSC) Hypervelocity Impact Technology Facility (HITF) [1], building 267 (Houston, Texas) between January 2003 and December 2005 to test the HVI performance of metal foams, as compared to the metal honeycomb panels currently in service. The HITF testing was conducted at the NASA JSC White Sands Testing Facility (WSTF) at Las Cruces, New Mexico. Eric L. Christiansen, Ph.D., and NASA Lead for Micro-Meteoroid Orbital Debris (MMOD) Protection requested these hypervelocity impact tests as part of shielding research conducted for the JSC Center Director Discretionary Fund (CDDF) project. The structure tested is a metal foam sandwich structure; a metal foam core between two metal facesheets. Aluminum and Titanium metals were tested for foam sandwich and honeycomb sandwich structures. Aluminum honeycomb core material is currently used in Orbiter Vehicle (OV) radiator panels and in other places in space structures. It has many desirable characteristics and performs well by many measures, especially when normalized by density. Aluminum honeycomb does not perform well in Hypervelocity Impact (HVI) Testing. This is a concern, as honeycomb panels are often exposed to space environments, and take on the role of Micrometeoroid / Orbital Debris (MMOD) shielding. Therefore, information on possible replacement core materials which perform adequately in all necessary functions of the material would be useful. In this report, HVI data is gathered for these two core materials in certain configurations and compared to gain understanding of the metal foam HVI performance.

  11. Sandwiched Rényi divergence satisfies data processing inequality

    SciTech Connect

    Beigi, Salman

    2013-12-15

    Sandwiched (quantum) α-Rényi divergence has been recently defined in the independent works of Wilde et al. [“Strong converse for the classical capacity of entanglement-breaking channels,” preprint http://arxiv.org/abs/arXiv:1306.1586 (2013)] and Müller-Lennert et al. [“On quantum Rényi entropies: a new definition, some properties and several conjectures,” preprint http://arxiv.org/abs/arXiv:1306.3142v1 (2013)]. This new quantum divergence has already found applications in quantum information theory. Here we further investigate properties of this new quantum divergence. In particular, we show that sandwiched α-Rényi divergence satisfies the data processing inequality for all values of α > 1. Moreover we prove that α-Holevo information, a variant of Holevo information defined in terms of sandwiched α-Rényi divergence, is super-additive. Our results are based on Hölder's inequality, the Riesz-Thorin theorem and ideas from the theory of complex interpolation. We also employ Sion's minimax theorem.

  12. Sandwich enzyme-linked immunosorbent assay for Taiwan cobra venom.

    PubMed

    Huang, Yu-Ping; Yu, Yi-Jung; Hung, Dong-Zong

    2002-08-01

    Poisonous snake bite victims usually have difficulty identifying the species, and clinical manifestations alone are not reliable because of overlapping symptoms. Thus, it is important to develop a quick and reliable mean of identifying the snake responsible. We describe the development of a sandwich-ELISA method for detection of venom in biological samples and apply it to a case of snakebite to confirm the clinical diagnosis. The sandwich-ELISA takes 6 h to complete. Cobra venom antigen gave positive absorbance at about 500 pg/ml. Good linearity with R2 values over 0.99 were observed in dilution series of 1:100 ng/mL of cobra venom in calf serum and human urine. A snakebite initially thought to be Trimeresurus mucrosquamatus was proven cobra with a serum venom level up to 288 ngmL 3 h after envenoming. Sandwich-ELISA provides a rapid and accurate method for clinical identification and evaluation of toxic antigens circulating in individuals bitten by the Taiwan cobra snake. PMID:12136964

  13. Development of aircraft lavatory compartments with improved fire resistance characteristics. Phase 2: Sandwich panel resin system development

    NASA Technical Reports Server (NTRS)

    Anderson, R. A.; Arnold, D. B.; Johnson, G. A.

    1979-01-01

    A NASA-funded program is described which aims to develop a resin system for use in the construction of lavatory wall panels, sidewall panels, and ceiling panels possessing flammability, smoke and gas emission, and toxicity (FS&T) characteristics superior to the existing epoxy resin. Candidate resins studied were phenolic, polyimide, and bismaleimide. Based on the results of a series of FS&T as well as mechanical and aesthetic property tests, a phenolic resin was chosen as the superior material. Material and process specifications covering the phenolic resin based materials were prepared and a method of rating sandwich panel performance was developed.

  14. Data characterizing compressive properties of Al/Al2O3 syntactic foam core metal matrix sandwich

    PubMed Central

    Omar, Mohammed Yaseer; Xiang, Chongchen; Gupta, Nikhil; Strbik, Oliver M.; Cho, Kyu

    2015-01-01

    Microstructural observations and compressive property datasets of metal matrix syntactic foam core sandwich composite at quasi-static and high strain rate (HSR) conditions (525–845 s−1) are provided. The data supplied in this article includes sample preparation procedure prior to scanning electron and optical microscopy as well as the micrographs. The data used to construct the stress–strain curves and the derived compressive properties of all specimens in both quasi-static and HSR regions are included. Videos of quasi-static compressive failure and that obtained by a high speed image acquisition system during deformation and failure of HSR specimen are also included. PMID:26587558

  15. General stability analysis of composite sandwich plates under thermal load

    NASA Astrophysics Data System (ADS)

    Abdallah, Shaher A.

    In structures subjected to high temperature change such as high-speed aircraft the panels are stressed more significantly under thermal loading than mechanical loading. This can produce instability within the structure; therefore, the thermal loading may become the primary factor in the design of the structure. For example, buckling and facesheet wrinkling are two major failure modes of the composite sandwich plates subjected to various loadings. The goal of this dissertation is to study the stability analysis of composite sandwich plates due to buckling and wrinkling subjected to thermal loading. The primary objective is to find out the critical failure mode and the associated critical temperature change causing it. For thermal buckling and wrinkling analysis, the critical temperature change Delta Tcr, is of more interest than the critical thermal load. In this study, two different approaches of the stability problem of the composite sandwich plate subjected to thermally induced load are developed. In the first approach, the wrinkling analysis and buckling analysis are performed separately to evaluate their associated critical wrinkling and buckling temperature changes. For the face-wrinkling problem, two different models, the linear decaying Hoff model and exponential decaying Chen model are employed. The global buckling analysis is based on the energy method. The second approach is based on the unified theory of Benson and Mayers. In such an approach, the critical temperature change for both the global buckling and face wrinkling can be evaluated simultaneously. A potential energy based variation principle has been applied to formulate the problem. The Lagrange multipliers are used to satisfy the face-core continuity conditions. The buckling and wrinkling can be analyzed and calculated simultaneously. Therefore, the critical wrinkling temperature and the critical buckling temperature are found in a single analysis. The critical buckling and wrinkling stresses

  16. Shaped Pd-Ni-Pt core-sandwich-shell nanoparticles: influence of Ni sandwich layers on catalytic electrooxidations.

    PubMed

    Sneed, Brian T; Young, Allison P; Jalalpoor, Daniel; Golden, Matthew C; Mao, Shunjia; Jiang, Ying; Wang, Yong; Tsung, Chia-Kuang

    2014-07-22

    Shape-controlled metal nanoparticles (NPs) interfacing Pt and nonprecious metals (M) are highly active energy conversion electrocatalysts; however, there are still few routes to shaped M-Pt core-shell NPs and fewer studies on the geometric effects of shape and strain on catalysis by such structures. Here, well-defined cubic multilayered Pd-Ni-Pt sandwich NPs are synthesized as a model platform to study the effects of the nonprecious metal below the shaped Pt surface. The combination of shaped Pd substrates and mild reduction conditions directs the Ni and Pt overgrowth in an oriented, layer-by-layer fashion. Exposing a majority of Pt(100) facets, the catalytic performance in formic acid and methanol electro-oxidations (FOR and MOR) is assessed for two different Ni layer thicknesses and two different particle sizes of the ternary sandwich NPs. The strain imparted to the Pt shell layer by the introduction of the Ni sandwich layer (Ni-Pt lattice mismatch of ∼11%) results in higher specific initial activities compared to core-shell Pd-Pt bimetallic NPs in alkaline MOR. The trends in activity are the same for FOR and MOR electrocatalysis in acidic electrolyte. However, restructuring in acidic conditions suggests a more complex catalytic behavior from changes in composition. Notably, we also show that cubic quaternary Au-Pd-Ni-Pt multishelled NPs, and Pd-Ni-Pt nanooctahedra can be generated by the method, the latter of which hold promise as potentially highly active oxygen reduction catalysts.

  17. Vibration Characteristics Determined for Stainless Steel Sandwich Panels With a Metal Foam Core for Lightweight Fan Blade Design

    NASA Technical Reports Server (NTRS)

    Ghosn, Louis J.; Min, James B.; Raj, Sai V.; Lerch, Bradley A.; Holland, Frederic A., Jr.

    2004-01-01

    The goal of this project at the NASA Glenn Research Center is to provide fan materials that are safer, weigh less, and cost less than the currently used titanium alloy or polymer matrix composite fans. The proposed material system is a sandwich fan construction made up of thin solid face sheets and a lightweight metal foam core. The stiffness of the sandwich structure is increased by separating the two face sheets by the foam layer. The resulting structure has a high stiffness and lighter weight in comparison to the solid facesheet material alone. The face sheets carry the applied in-plane and bending loads (ref. 1). The metal foam core must resist the transverse shear and transverse normal loads, as well as keep the facings supported and working as a single unit. Metal foams have ranges of mechanical properties, such as light weight, impact resistance, and vibration suppression (ref. 2), which makes them more suitable for use in lightweight fan structures. Metal foams have been available for decades (refs. 3 and 4), but the difficulties in the original processes and high costs have prevented their widespread use. However, advances in production techniques and cost reduction have created a new interest in this class of materials (ref. 5). The material chosen for the face sheet and the metal foam for this study was the aerospace-grade stainless steel 17-4PH. This steel was chosen because of its attractive mechanical properties and the ease with which it can be made through the powder metallurgy process (ref. 6). The advantages of a metal foam core, in comparison to a typical honeycomb core, are material isotropy and the ease of forming complex geometries, such as fan blades. A section of a 17-4PH sandwich structure is shown in the following photograph. Part of process of designing any blade is to determine the natural frequencies of the particular blade shape. A designer needs to predict the resonance frequencies of a new blade design to properly identify a useful

  18. Vibrational analysis of rectangular sandwich plates resting on some elastic point supports

    SciTech Connect

    Ichinomiya, Osamu; Maruyama, Koichi; Sekine, Kouji

    1995-11-01

    An approximate solution of forced-vibration for rectangular sandwich plate resting on some elastic point supports is presented. The sandwich plate has thin, anisotropic composite laminated faces and a thick orthotropic core. The simplified sandwich plate model is used in the analysis. The governing equation of elastically point supported rectangular sandwich plate is obtained by using the Lagrange equation. The steady state response solution to a sinusoidally varying point force is also derived. The response curves of rectangular sandwich plates having CFRP laminated faces and aluminum honeycomb core is calculated. Application examples illustrate the effects of laminate lay-up of face sheets, core material properties and core thickness ratio on the vibration characteristics of rectangular sandwich plate.

  19. Energy absorption capabilities of composite sandwich panels under blast loads

    NASA Astrophysics Data System (ADS)

    Sankar Ray, Tirtha

    As blast threats on military and civilian structures continue to be a significant concern, there remains a need for improved design strategies to increase blast resistance capabilities. The approach to blast resistance proposed here is focused on dissipating the high levels of pressure induced during a blast through maximizing the potential for energy absorption of composite sandwich panels, which are a competitive structural member type due to the inherent energy absorption capabilities of fiber reinforced polymer (FRP) composites. Furthermore, the middle core in the sandwich panels can be designed as a sacrificial layer allowing for a significant amount of deformation or progressive failure to maximize the potential for energy absorption. The research here is aimed at the optimization of composite sandwich panels for blast mitigation via energy absorption mechanisms. The energy absorption mechanisms considered include absorbed strain energy due to inelastic deformation as well as energy dissipation through progressive failure of the core of the sandwich panels. The methods employed in the research consist of a combination of experimentally-validated finite element analysis (FEA) and the derivation and use of a simplified analytical model. The key components of the scope of work then includes: establishment of quantified energy absorption criteria, validation of the selected FE modeling techniques, development of the simplified analytical model, investigation of influential core architectures and geometric parameters, and investigation of influential material properties. For the parameters that are identified as being most-influential, recommended values for these parameters are suggested in conceptual terms that are conducive to designing composite sandwich panels for various blast threats. Based on reviewing the energy response characteristic of the panel under blast loading, a non-dimensional parameter AET/ ET (absorbed energy, AET, normalized by total energy

  20. Fiber-Reinforced-Foam (FRF) Core Composite Sandwich Panel Concept for Advanced Composites Technologi

    NASA Technical Reports Server (NTRS)

    2010-01-01

    Fiber-Reinforced-Foam (FRF) Core Composite Sandwich Panel Concept for Advanced Composites Technologies Project - Preliminary Manufacturing Demonstration Articles for Ares V Payload Shroud Barrel Acreage Structure

  1. Experimental evaluation of two 36 inch by 47 inch graphite/epoxy sandwich shear webs

    NASA Technical Reports Server (NTRS)

    Bush, H. G.

    1975-01-01

    The design is described and test of two large (36 in. x 47 in.) graphite/epoxy sandwich shear webs. One sandwich web was designed to exhibit strength failure of the facings at a shear load of 7638 lbs/in., which is a characteristic loading for the space shuttle orbiter main engine thrust beam structure. The second sandwich web was designed to exhibit general instability failure at a shear load of 5000 lbs/in., to identify problem areas of stability critical sandwich webs and to assess the adequacy of contemporary analysis techniques.

  2. Damping Properties of Sandwich Truss Core Structures by Strain Energy Method

    NASA Astrophysics Data System (ADS)

    Wesolowski, M.; Rucevskis, S.; Janeliukstis, R.; Polanski, M.

    2015-11-01

    Sandwich panel structures with stiff face sheets and cellular cores are widely used to support dynamic loads. Combining face sheets made of carbon fibre reinforced plastics (CFRPs) with an aluminium pyramidal truss improves the damping performance of the structure due to viscoelastic character of CRFP composites. To predict the damping characteristics of the pyramidal truss core sandwich panel the strain energy method is adopted. The procedure for evaluating the damping of the sandwich panel was performed using commercial finite element software NASTRAN and MATLAB. Non-contact vibration tests were performed on the real sandwich panels in order to extract the modal characteristics and compare them with the numerical predictions.

  3. Hail Ice Impact of Lightweight Composite Sandwich Panels

    NASA Astrophysics Data System (ADS)

    Luong, Sean Dustin

    There is a growing demand for the usage of composite sandwich structures in the aircraft industry. Aircraft may suffer damage from a variety of impact sources such as ground service equipment, runway debris, bird strike, or hail ice. The damage response of hail ice impacts on composite sandwich structures is not well understood and they can often result in core damage without visually detectable surface damage. This seed damage may grow and lead to large-scale failure of the structure through repetitive operational loading, such as ground-air-ground cycles of aircraft (causes core internal pressurization). Therefore, it is necessary to understand the types of damage that can occur as a result of impacts. This study explores the effect of high velocity hail ice impact on damage formation in lightweight composite sandwich panels, particularly at a level that produces barely visible external damage. Panels consisting of two different facesheet thicknesses (1.19 and 1.87 mm) were impacted at angles of 25, 40, and 90 degrees at speeds of 25 and 50 m/s. The tests revealed three different core damage modes. Any level of measurable surface damage was an indicator of the presence of internal core damage, but internal damage could also be present without measurable surface damage. Thus, visual inspection alone was not a reliable method of damage detection. No clear relationship was found between impact energy levels and internal damage state since, for example, both 83 and 20.5 J tests produced core fracture, while a 16 J test did not produce any core damage. All core damage occurred at a depth of 3-5 mm from the impact-side facesheet.

  4. Low Velocity Blunt Impact on Lightweight Composite Sandwich Panels

    NASA Astrophysics Data System (ADS)

    Chan, Monica Kar

    There is an increased desire to incorporate more composite sandwich structures into modern aircrafts. Because in-service aircrafts routinely experience impact damage during maintenance due to ground vehicle collision, dropped equipment, or foreign object damage (FOD) impact, it is necessary to understand their impact characteristics, particularly when blunt impact sources create internal damage with little or no external visibility. The objective of this investigation is to explore damage formation in lightweight composite sandwich panels due to low-velocity impacts of variable tip radius and energy level. The correlation between barely visible external dent formation and internal core damage was explored as a function of impact tip radius. A pendulum impactor was used to impact composite sandwich panels having honeycomb core while held in a 165 mm square window fixture. The panels were impacted by hardened steel tips with radii of 12.7, 25.4, 50.8, and 76.2 mm at energy levels ranging from 2 to 14 J. Experimental data showed little dependence of external dent depth on tip radius at very low energies of 2 to 6 J, and thus, there was also little variation in visibility due to tip radius. Four modes of internal core damage were identified. Internal damage span and depth were dependent on impact tip radius. Damage depth was also radius-dependent, but stabilized at constant depth independent of kinetic energy. Internal damage span increased with increasing impact energy, but not with increasing tip radius, suggesting a relationship between maximum damage tip radius with core density/size.

  5. Analysis and Fabrication of Paraboloidal CFRP Sandwich Mirrors

    NASA Astrophysics Data System (ADS)

    Hong, Tayo Steve

    The low areal weight requirements of telescopes in aerospace applications has driven the study on composite mirrors for several years. For example, the primary parabolic mirror in a balloon-borne, Cassegrain telescope required an optical quality better than 30 microns in figure RMS error. A parametric study on composite sandwich mirrors was conducted by using finite element analysis as well as optical analysis. The factors covered the cell sizes, core materials, core thicknesses, face layups, and support configurations. Based on theoretical calculations, many high quality spherical composite sandwich mirrors were generated by using a non-heat curing process. The CFRP faces and Nomex core were chosen as the baseline materials for mirror fabrication due to their high strength and low weight. The proposed replication method applied an interface layer between face and surface coat to eliminate print -through problems. Many important goals have been realized in those mirror samples with optical laser interferometer testing. These include the figure RMS error less than 2 microns and the surface RMS error less than 0.05 micron. The areal weights of the mirror samples are less than 7 kg/m ^2. The thermal stability of these mirrors was observed from the optical results with thermal cycling tests. The proposed 2-meter parabolic composite sandwich mirror, with an areal weight of less than 10 kg/m ^2, would consist of either (0/90/45/ -45) _{rm S} layup faces with an optimal 3^{' '} core or (QC) layup faces with a total core thickness of 5 inches. Both a ring support around the equator and the 18-point Hindle-type support would lead to the best optical quality under both self weight and thermal loading.

  6. Synthesis and characterization of a 1D chain-like Cu{sub 6} substituted sandwich-type phosphotungstate with pendant dinuclear Cu–azido complexes

    SciTech Connect

    Li, Yan-Ying; Zhao, Jun-Wei; Wei, Qi; Yang, Bai-Feng; Yang, Guo-Yu

    2014-02-15

    A novel Cu–azido complex modified hexa-Cu{sup II} substituted sandwich-type phosphotungstate [Cu(en){sub 2}]([Cu{sub 2}(en){sub 2}(μ-1,1-N{sub 3}){sub 2}(H{sub 2}O)]{sub 2}[Cu{sub 6}(en){sub 2}(H{sub 2}O){sub 2}(B-α-PW{sub 9}O{sub 34}){sub 2}])·6H{sub 2}O (1) (en=ethylene-diamine) has been prepared under hydrothermal conditions and structurally characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. 1 displays a beautiful 1-D chain architecture constructed from sandwich-type [Cu{sub 2}(en){sub 2}(μ-1,1-N{sub 3}){sub 2}(H{sub 2}O)]{sub 2}[Cu{sub 6}(en){sub 2}(H{sub 2}O){sub 2}(B-α-PW{sub 9}O{sub 34}){sub 2}]{sup 2−} units and [Cu(en){sub 2}]{sup 2+} linkers. To our knowledge, 1 represents the first hexa-Cu{sup II} sandwiched phosphotungstate with supporting Cu–azido complexes. - Graphical abstract: The first hexa-Cu{sup II} sandwiched phosphotungstate with supporting Cu–azido complexes has been prepared and characterized. Display Omitted - Highlights: • Hexa-copper-substituted phosphotungstate. • Cu–azido complexes modified hexa-Cu{sup II} substituted sandwich-type polyoxometalate. • 1-D chain architecture built by hexa-copper-substituted polyoxotungstate units.

  7. Sandwich double gate vertical tunneling field-effect transistor

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Zhang, Wen-hao; Yu, Cheng-hao; Cao, Fei

    2016-05-01

    In this work, a sandwich vertical tunnel field effect transistor (SDG-VTFET) is presented and studied. Since the dominant carrier tunneling of SDG-VFET occurs in a direction that is in line with the gate field, high ON-state current and steep subthreshold slope are observed. Comparisons between SDG-VFET and double gate tunnel field effect transistor are made to clarify advantages of SDG-VTFET. The simulation results of our work show that SDG-VTFET has stronger gate control, steeper subthreshold slope and higher ON-state current. The device plays a promising candidate for future low power circuit applications.

  8. Deformation and fracture of impulsively loaded sandwich panels

    NASA Astrophysics Data System (ADS)

    Wadley, H. N. G.; Børvik, T.; Olovsson, L.; Wetzel, J. J.; Dharmasena, K. P.; Hopperstad, O. S.; Deshpande, V. S.; Hutchinson, J. W.

    2013-02-01

    Light metal sandwich panel structures with cellular cores have attracted interest for multifunctional applications which exploit their high bend strength and impact energy absorption. This concept has been explored here using a model 6061-T6 aluminum alloy system fabricated by friction stir weld joining extruded sandwich panels with a triangular corrugated core. Micro-hardness and miniature tensile coupon testing revealed that friction stir welding reduced the strength and ductility in the welds and a narrow heat affected zone on either side of the weld by approximately 30%. Square, edge clamped sandwich panels and solid plates of equal mass per unit area were subjected to localized impulsive loading by the impact of explosively accelerated, water saturated, sand shells. The hydrodynamic load and impulse applied by the sand were gradually increased by reducing the stand-off distance between the test charge and panel surfaces. The sandwich panels suffered global bending and stretching, and localized core crushing. As the pressure applied by the sand increased, face sheet fracture by a combination of tensile stretching and shear-off occurred first at the two clamped edges of the panels that were parallel with the corrugation and weld direction. The plane of these fractures always lay within the heat affected zone of the longitudinal welds. For the most intensively loaded panels additional cracks occurred at the other clamped boundaries and in the center of the panel. To investigate the dynamic deformation and fracture processes, a particle-based method has been used to simulate the impulsive loading of the panels. This has been combined with a finite element analysis utilizing a modified Johnson-Cook constitutive relation and a Cockcroft-Latham fracture criterion that accounted for local variation in material properties. The fully coupled simulation approach enabled the relationships between the soil-explosive test charge design, panel geometry, spatially varying

  9. Measuring Core/Facesheet Bond Toughness in Honeycomb Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Nettles, A. T.

    2006-01-01

    This study examines two test methods to evaluate the peel toughness of the skin to core debond of sandwich panels. The methods tested were the climbing drum (CD) peel test and the double cantilever beam (DCB) test. While the CD peel test is only intended for qualitative measurements, it is shown in this study that qualitative measurements can be performed and compare well with DCB test data. It is also shown that artificially stiffening the facesheets of a DCB specimen can cause the test to behave more like a flatwise tensile test than a peel test.

  10. Devices, systems, and methods for conducting sandwich assays using sedimentation

    DOEpatents

    Schaff, Ulrich Y; Sommer, Gregory J; Singh, Anup K; Hatch, Anson V

    2015-02-03

    Embodiments of the present invention are directed toward devices, systems, and method for conducting sandwich assays using sedimentation. In one example, a method includes generating complexes on a plurality of beads in a fluid sample, individual ones of the complexes comprising a capture agent, a target analyte, and a labeling agent. The plurality of beads including the complexes may be transported through a density media, wherein the density media has a density lower than a density of the beads and higher than a density of the fluid sample, and wherein the transporting occurs, at least in part, by sedimentation. Signal may be detected from the labeling agents of the complexes.

  11. Fatigue and fracture of foam cores used in sandwich composites

    NASA Astrophysics Data System (ADS)

    Saenz, Elio

    This study focused on the fracture and fatigue crack growth behavior in polyvinylchloride (PVC) and polyethersulfone (PES) foams. A new sandwich double cantilever beam (DCB) test specimen was implemented. Elastic foundation and finite element analysis and experimental testing confirmed that the DCB specimen is appropriate for static and cyclic crack propagation testing of soft polymer foams. A comprehensive experimental mechanical analysis was conducted on PVC foams of densities ranging from 45 to 100 kg/m3 and PES foams of densities ranging from 60 to 130 kg/m3. An in-situ scanning electron microscope study on miniature foam fracture specimens showed that crack propagation in the PVC foam was inter-cellular and in the PES foam, failure occurred predominately by extensional failure of vertical cell edges. Sandwich DCB specimens were loaded cyclically as well. For the PVC foams, the crack growth rates were substantially influence by the density. For the PES foams, there was no clear indication about the influence of foam density on the crack growth rate.

  12. Sandwich electrode designed for high performance lithium-ion battery

    NASA Astrophysics Data System (ADS)

    Zhao, Chunsong; Luo, Xi; Chen, Chengmeng; Wu, Hui

    2016-05-01

    We fabricated a sandwich structure Li-ion battery electrode by trapping micron-sized silicon between a copper current collector and a graphene coating. During dynamic electrochemical cycles, the volume change of the silicon can be buffered by the coating through the deformation of soft graphenes. This structure can effectively prevent the silicon particles from escaping from the current collector while keeping the buffered graphene coating integrated and unbroken during deformation. The electrodes could be maintained for 400 cycles at a constant charge capacity of 1000 mA h g-1.We fabricated a sandwich structure Li-ion battery electrode by trapping micron-sized silicon between a copper current collector and a graphene coating. During dynamic electrochemical cycles, the volume change of the silicon can be buffered by the coating through the deformation of soft graphenes. This structure can effectively prevent the silicon particles from escaping from the current collector while keeping the buffered graphene coating integrated and unbroken during deformation. The electrodes could be maintained for 400 cycles at a constant charge capacity of 1000 mA h g-1. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr09049k

  13. Impact Delamination and Fracture in Aluminum/Acrylic Sandwich Plates

    NASA Technical Reports Server (NTRS)

    Liaw, Benjamin; Zeichner, Glenn; Liu, Yanxiong; Bowles, Kenneth J. (Technical Monitor)

    2000-01-01

    Impact-induced delamination and fracture in 6061-T6 aluminum/cast acrylic sandwich plates adhered by epoxy were generated in an instrumented drop-weight impact machine. Although only a small dent was produced on the aluminum side when a hemispherical penetrator tup was dropped onto it from a couple of inches, a large ring of delamination at the interface was observed. The delamination damage was often accompanied by severe shattering in the acrylic substratum. Damage patterns in the acrylic layer include radial and ring cracks and, together with delamination at the interface, may cause peeling-off of acrylic material from the sandwich plate. Theory of stress-wave propagation can be used to explain these damage patterns. The impact tests were conducted at various temperatures. The results also show clearly that temperature effect is very important in impact damage. For pure cast acrylic nil-ductile transition (NDT) occurs between 185-195 F. Excessive impact energy was dissipated into fracture energy when tested at temperature below this range or through plastic deformation when tested at temperature above the NDT temperature. Results from this study will be used as baseline data for studying fiber-metal laminates, such as GLARE and ARALL for advanced aeronautical and astronautical applications.

  14. Experimental and Numerical Analysis of Inserts in Sandwich Structures

    NASA Astrophysics Data System (ADS)

    Bunyawanichakul, P.; Castanie, B.; Barrau, J.-J.

    2005-05-01

    In aeronautics, sandwich structures are widely used for secondary structures like flaps or landing gear doors. In the case of landing gear doors, the junction is made by a local reinforcement called an insert. This insert is made by a resin molded in the Nomex™ sandwich core. Such structures are still designed mainly using test results and the lack of an efficient numerical model remains a problem. The purpose of this study is on the one hand to perform experiments in order to be able to identify the failure modes and on the other hand to propose an efficient numerical model. Pull-out tests with cycling were conducted and 3D displacement measured by optical methods. The potential failure modes are numerous (delamination, local fiber breaking, skin/core debonding, core crushing, core shear buckling, potting failure, etc.). Experiments demonstrated that, for the lower loads, the non-linearity and the hysteresis are mainly due to core shear buckling. From this observation, the nonlinear behavior of the core is identified by a 3 point-bending test. The shear-modulus damage law is then implemented on a non-linear finite element model and an acceptable correlation of the tests is achieved. As a consequence, some improvements of the technology will be proposed, manufactured and tested.

  15. Dispersion of guided waves in composite laminates and sandwich panels

    NASA Astrophysics Data System (ADS)

    Schaal, Christoph; Mal, Ajit

    2015-03-01

    In composite structures, damages are often invisible from the surface and can grow to reach a critical size, potentially causing catastrophic failure of the entire structure. Thus safe operation of these structures requires careful monitoring of the initiation and growth of such defects. Ultrasonic methods using guided waves offer a reliable and cost-effective method for structural health monitoring in advanced structures. Guided waves allow for long monitoring ranges and are very sensitive to defects within their propagation path. In this work, the relevant properties of guided Lamb waves for damage detection in composite structures are investigated. An efficient numerical approach is used to determine their dispersion characteristics, and these results are compared to those from laboratory experiments. The experiments are based on a pitch-catch method, in which a pair of movable transducers is placed on one surface of the structure to induce and detect guided Lamb waves. The specific cases considered include an aluminum plate and an aluminum honeycomb sandwich panel with woven composite face sheets. In addition, a disbond of the interface between one of the face sheets and the honeycomb core of the sandwich panel is also considered, and the dispersion characteristics of the two resultant waveguides are determined. Good agreement between numerical and experimental dispersion results is found, and suggestions on the applicability of the pitch-catch system for structural health monitoring are made.

  16. First record of a banded Sandwich Tern (Thalasseus sandvicensis) moving from England to the United States

    USGS Publications Warehouse

    Spendelow, Jeffrey A.

    2015-01-01

    A Sandwich Tern (Thalasseus sandvicensis sandvicensis) banded as a chick in 2002 at Coquet Island off the northeast coast of Great Britain was observed at two locations on Cape Cod, Massachusetts, USA, in August and September 2013. This is the first record of a banded Sandwich Tern from the United Kingdom being observed in the United States.

  17. Natural cork agglomerate employed as an environmentally friendly solution for quiet sandwich composites.

    PubMed

    Sargianis, James; Kim, Hyung-ick; Suhr, Jonghwan

    2012-01-01

    Carbon fiber-synthetic foam core sandwich composites are widely used for many structural applications due to their superior mechanical performance and low weight. Unfortunately these structures typically have very poor acoustic performance. There is increasingly growing demand in mitigating this noise issue in sandwich composite structures. This study shows that marrying carbon fiber composites with natural cork in a sandwich structure provides a synergistic effect yielding a noise-free sandwich composite structure without the sacrifice of mechanical performance or weight. Moreover the cork-core sandwich composites boast a 250% improvement in damping performance, providing increased durability and lifetime operation. Additionally as the world seeks environmentally friendly materials, the harvesting of cork is a natural, renewable process which reduces subsequent carbon footprints. Such a transition from synthetic foam cores to natural cork cores could provide unprecedented improvements in acoustic and vibrational performance in applications such as aircraft cabins or wind turbine blades.

  18. High renewable content sandwich structures based on flax-basalt hybrids and biobased epoxy polymers

    NASA Astrophysics Data System (ADS)

    Colomina, S.; Boronat, T.; Fenollar, O.; Sánchez-Nacher, L.; Balart, R.

    2014-05-01

    In the last years, a growing interest in the development of high environmental efficiency materials has been detected and this situation is more accentuated in the field of polymers and polymer composites. In this work, green composite sandwich structures with high renewable content have been developed with core cork materials. The base resin for composites was a biobased epoxy resin derived from epoxidized vegetable oils. Hybrid basalt-flax fabrics have been used as reinforcements for composites and the influence of the stacking sequence has been evaluated in order to optimize the appropriate laminate structure for the sandwich bases. Core cork materials with different thickness have been used to evaluate performance of sandwich structures thus leading to high renewable content composite sandwich structures. Results show that position of basalt fabrics plays a key role in flexural fracture of sandwich structures due to differences in stiffness between flax and basalt fibers.

  19. Natural Cork Agglomerate Employed as an Environmentally Friendly Solution for Quiet Sandwich Composites

    PubMed Central

    Sargianis, James; Kim, Hyung-ick; Suhr, Jonghwan

    2012-01-01

    Carbon fiber-synthetic foam core sandwich composites are widely used for many structural applications due to their superior mechanical performance and low weight. Unfortunately these structures typically have very poor acoustic performance. There is increasingly growing demand in mitigating this noise issue in sandwich composite structures. This study shows that marrying carbon fiber composites with natural cork in a sandwich structure provides a synergistic effect yielding a noise-free sandwich composite structure without the sacrifice of mechanical performance or weight. Moreover the cork-core sandwich composites boast a 250% improvement in damping performance, providing increased durability and lifetime operation. Additionally as the world seeks environmentally friendly materials, the harvesting of cork is a natural, renewable process which reduces subsequent carbon footprints. Such a transition from synthetic foam cores to natural cork cores could provide unprecedented improvements in acoustic and vibrational performance in applications such as aircraft cabins or wind turbine blades. PMID:22574250

  20. Optimum Design of Composite Sandwich Structures Subjected to Combined Torsion and Bending Loads

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Li, Gangyan; Wang, Chun H.; You, Min

    2012-06-01

    This research is motivated by the increase use of composite sandwich structures in a wide range of industries such as automotive, aerospace and civil infrastructure. To maximise stiffness at minimum weight, the paper develops a minimum weight optimization method for sandwich structure under combined torsion and bending loads. We first extend the minimum-weight design of sandwich structures under bending load to the case of torsional deformation and then present optimum solutions for the combined requirements of both bending and torsional stiffness. Three design cases are identified for a sandwich structure required to meet multiple design constraints of torsion and bending stiffness. The optimum solutions for all three cases are derived. To illustrate the newly developed optimum design solutions, numerical examples are presented for sandwich structures made of either isotropic face skins or orthotropic composite face skins.

  1. Vibration analysis of sandwich rectangular plates with magnetorheological elastomer damping treatment

    NASA Astrophysics Data System (ADS)

    Yeh, Jia-Yi

    2013-03-01

    In this study, the vibration analysis of sandwich rectangular plates with magnetorheological (MR) elastomer damping treatment is presented. The rectangular plate is combined with a magnetorheological elastomer core layer and a constraining layer to improve the vibration behaviors of the sandwich system. The MR material shows variations in the rheological properties when subjected to varying magnetic fields. Additionally, the MR material exhibits a rapid time response and is applicable to structures or devices when a tunable system is required. The magnetorheological elastomer is found to have a significant effect on the vibration characteristics of the sandwich rectangular plate. The modal damper and the natural frequencies for the sandwich plate system are calculated for various magnetic fields and some designed parameters by utilizing the finite element method. The damping effects of the sandwich plate system can be controlled and changed when different magnetic field strengths are applied.

  2. Computed tomography with single-shot dual-energy sandwich detectors

    NASA Astrophysics Data System (ADS)

    Kim, Seung Ho; Youn, Hanbean; Kim, Daecheon; Kim, Dong Woon; Jeon, Hosang; Kim, Ho Kyung

    2016-03-01

    Single-shot dual-energy sandwich detector can produce sharp images because of subtraction of images from two sub-detector layers, which have different thick x-ray converters, of the sandwich detector. Inspired by this observation, the authors have developed a microtomography system with the sandwich detector in pursuit of high-resolution bone-enhanced small-animal imaging. The preliminary results show that the bone-enhanced images reconstructed with the subtracted projection data are better in visibility of bone details than the conventionally reconstructed images. In addition, the bone-enhanced images obtained from the sandwich detector are relatively immune to the artifacts caused by photon starvation. The microtomography with the single-shot dual-energy sandwich detector will be useful for the high-resolution bone imaging.

  3. Minimum-Weight Sandwich Structure Optimum Design Subjected to Torsional Loading

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Li, Gangyan; Wang, Chun H.; You, Min

    2012-04-01

    As one of the most valued structural engineering innovations developed by the composites industry, sandwich structures are now used extensively in automotive, aerospace and civil infrastructure due to the main advantage of lightweight. This paper develops a minimum weight optimization method for sandwich structure subjected to torsion load. The design process are identified for a sandwich structure required to meet the design constraint of torsion stiffness. The optimum solutions show that at optimum design the core weight accounts for 66.7% of the whole sandwich structure. To illustrate the newly developed optimum design solutions, numerical examples are presented for sandwich structures made of either isotropic face skins or orthotropic composite face skins. Agreement between the theoretical analysis and the examples results is good.

  4. PLLA/Flax Mat/Balsa Bio-Sandwich Manufacture and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Le Duigou, Antoine; Deux, Jean-Marc; Davies, Peter; Baley, Christophe

    2011-10-01

    This paper describes the manufacture and mechanical characterization of a sandwich material which is 100% bio-sourced. The flax mat/PLLA facings and balsa core can also be composted at end of service life. Manufacture is by vacuum bag moulding. The optimum moulding time and temperature are a compromise between ensuring good impregnation and avoiding degradation, and holding for 60 min at 180°C was found to be satisfactory. The mechanical properties of the bio-sandwich obtained are compared to those of a traditional glass reinforced polyester balsa sandwich. The flexural strength is 30% lower, as predicted based on the facing properties. Skin/core adhesion is also measured using debonding tests. Crack propagation occurs at the skin/core interface in the traditional sandwich but within the facing in the bio-sandwich. The impregnation of the core in the two materials is examined using X-ray micro-tomography.

  5. Natural cork agglomerate employed as an environmentally friendly solution for quiet sandwich composites.

    PubMed

    Sargianis, James; Kim, Hyung-ick; Suhr, Jonghwan

    2012-01-01

    Carbon fiber-synthetic foam core sandwich composites are widely used for many structural applications due to their superior mechanical performance and low weight. Unfortunately these structures typically have very poor acoustic performance. There is increasingly growing demand in mitigating this noise issue in sandwich composite structures. This study shows that marrying carbon fiber composites with natural cork in a sandwich structure provides a synergistic effect yielding a noise-free sandwich composite structure without the sacrifice of mechanical performance or weight. Moreover the cork-core sandwich composites boast a 250% improvement in damping performance, providing increased durability and lifetime operation. Additionally as the world seeks environmentally friendly materials, the harvesting of cork is a natural, renewable process which reduces subsequent carbon footprints. Such a transition from synthetic foam cores to natural cork cores could provide unprecedented improvements in acoustic and vibrational performance in applications such as aircraft cabins or wind turbine blades. PMID:22574250

  6. Lightweight composites for modular panelized construction

    NASA Astrophysics Data System (ADS)

    Vaidya, Amol S.

    Rapid advances in construction materials technology have enabled civil engineers to achieve impressive gains in the safety, economy, and functionality of structures built to serve the common needs of society. Modular building systems is a fast-growing modern, form of construction gaining recognition for its increased efficiency and ability to apply modern technology to the needs of the market place. In the modular construction technique, a single structural panel can perform a number of functions such as providing thermal insulation, vibration damping, and structural strength. These multifunctional panels can be prefabricated in a manufacturing facility and then transferred to the construction site. A system that uses prefabricated panels for construction is called a "panelized construction system". This study focuses on the development of pre-cast, lightweight, multifunctional sandwich composite panels to be used for panelized construction. Two thermoplastic composite panels are proposed in this study, namely Composite Structural Insulated Panels (CSIPs) for exterior walls, floors and roofs, and Open Core Sandwich composite for multifunctional interior walls of a structure. Special manufacturing techniques are developed for manufacturing these panels. The structural behavior of these panels is analyzed based on various building design codes. Detailed descriptions of the design, cost analysis, manufacturing, finite element modeling and structural testing of these proposed panels are included in this study in the of form five peer-reviewed journal articles. The structural testing of the proposed panels involved in this study included flexural testing, axial compression testing, and low and high velocity impact testing. Based on the current study, the proposed CSIP wall and floor panels were found satisfactory, based on building design codes ASCE-7-05 and ACI-318-05. Joining techniques are proposed in this study for connecting the precast panels on the construction

  7. Laser evaporation of metal sandwich layers for improved IC metallization

    NASA Astrophysics Data System (ADS)

    Pielmeier, R.; Bollmann, D.; Haberger, K.

    1990-12-01

    With the further shrink of IC dimensions, metallization becomes the most crucial layer because conductivity and contact resistivity determine the RC constants and thus the speed of the circuits. With our Q-switched Nd:YAG laser we have evaporated different materials (Al, Ti, W, Pt, Au), alloys (Ta-Si) and dielectrics (ZrO 2, Al 2O 3). We also produced sandwich layers (Al-Au, Ti-Al). The layers were investigated with regard to deposition rate, homogeneity, adhesion, step coverage and surface roughness. Deposition rates in the order of 60 nm/min were achieved. At a power of 10 W and a repetition rate of about 5 kHz we could form ohmic contacts to silicon with a good step coverage in the contact.

  8. Prediction of the ballistic limit of an aluminium sandwich panel

    NASA Astrophysics Data System (ADS)

    Campbell, J.; De Vuyst, T.; Vignjevic, R.; Hughes, K.

    2016-08-01

    This paper presents research on modelling the impact of a 150g projectile on a 35mm thick aluminium sandwich panel. The objective of the work is a predictive modelling capability for the ballistic limit of the panel. A predictive modelling capability supports the design of capture and deorbit missions for large items of space debris such as satellites and rocket upper stages. A detailed explicit finite element model was built using the LSDYNA software and results were compared with experimental data for the projectile exit velocity to establish key parameters. The primary parameters influencing the model behaviour were the strength and failure of the aluminium face sheets and the friction between projectile and panel. The model results showed good agreement with experimental results for ogive nose projectiles, but overestimated the exit velocity for flat nose projectiles.

  9. Small bending and stretching of sandwich-type shells

    NASA Technical Reports Server (NTRS)

    Reissner, Eric

    1950-01-01

    A theory has been developed for small bending and stretching of sandwich-type shells. This theory is an extension of the known theory of homogeneous thin elastic shells. It was found that two effects are important in the present problem, which are not normally of importance in the theory of curved shells: (1) the effect of transverse shear deformation and (2) the effect of transverse normal stress deformation. The first of these two effects has been known to be of importance in the theory of plates and beams. The second effect was found to occur in a manner which is typical for shells and has no counterpart in flat-plate theory. The general results of this report have been applied to the solution of problems concerning flat plates, circular rings, circular cylindrical shells, and spherical shells. In each case numerical examples have been given, illustrating the magnitude of the effects of transverse shear and normal stress deformation.

  10. Predicting The Compression Strength Of Impact-Damaged Sandwich Panels

    NASA Technical Reports Server (NTRS)

    Ratcliffe, James; Jackson, Wade; Schaff, Jeffery

    1990-01-01

    The objective of this work was to develop a technique for predicting the residual compression strength of sandwich panels containing impact damage in one facesheet. The technique was tailored to predict the strength of specimens that exhibit a failure mode involving the formation of kink bands at locations of peak strain in the region of impact damage. Under continued compression loading, the kink bands propagate in a stable manner perpendicular to the applied load. When a critical kink-band length is reached, growth becomes unstable corresponding to panel failure. The analysis follows in two sections. The first section calculates the far-field stress required for stable kink-band growth and the second calculates that required for unstable growth. The residual strength prediction is made when the stress for stable growth becomes equal to that for unstable kink-band growth. Initial comparisons between analysis and experiment show good agreement.

  11. Development and Optimization of a Thrombin Sandwich Aptamer Microarray

    PubMed Central

    Meneghello, Anna; Sosic, Alice; Antognoli, Agnese; Cretaio, Erica; Gatto, Barbara

    2012-01-01

    A sandwich microarray employing two distinct aptamers for human thrombin has been optimized for the detection of subnanomolar concentrations of the protein. The aptamer microarray demonstrates high specificity for thrombin, proving that a two-site binding assay with the TBA1 aptamer as capture layer and the TBA2 aptamer as detection layer can ensure great specificity at times and conditions compatible with standard routine analysis of biological samples. Aptamer microarray sensitivity was evaluated directly by fluorescent analysis employing Cy5-labeled TBA2 and indirectly by the use of TBA2-biotin followed by detection with fluorescent streptavidin. Sub-nanomolar LODs were reached in all cases and in the presence of serum, demonstrating that the optimized aptamer microarray can identify thrombin by a low-cost, sensitive and specific method.

  12. Detection of bound residues in soils by sandwich-immunoassay

    SciTech Connect

    Dosch, M.; Weller, M.G.; Niessner, R.

    1995-12-31

    Immunoassays are useful analytical instruments for the detection of many environmental compounds. This method was not introduced for the detection of non-extractable compounds in soil. So-called ``bound residues`` consist of a soil component, e.g. humic acids and an irreversibly bound pollutant. Because of the complexity of those macromolecules conventional analytical methods in general do not work. Enzyme immunoassays, in contrast, seem to have a large potential for applications and further developments in this field. The use of antibodies with high affinity to the analytes makes a selective detection of environmental pollutants possible. With the development of an enzyme-labeled sandwich-immunoassay polycyclic aromatic hydrocarbons (PAHs) irreversibly bound to humic acids were determined for the first time.

  13. Detection of bound residues in soils by sandwich-immunoassay

    NASA Astrophysics Data System (ADS)

    Dosch, M.; Weller, Michael G.; Niessner, Reinhard

    1995-10-01

    Immunoassays are useful analytical instruments for the detection of many environmental compounds. This method is now introduced for the detection of non-extractable compounds in soil. So-called 'bound residues' consist of a soil component, e.g. humic acids, and an irreversibly bound pollutant. Because of the complexity of those macromolecules conventional analytical methods in general do not work. Enzyme immunoassays, in contrast, seem to have a large potential for applications and further developments in this field. The use of antibodies with high affinity to the analytes makes a selective detection of environmental pollutants possible. With the development of an enzyme-labeled sandwich-immunoassay polycyclic aromatic hydrocarbons (PAHs), irreversibly bound to humic acids, were determined for the first time.

  14. Scattering analysis of high performance large sandwich radomes

    NASA Astrophysics Data System (ADS)

    Shavit, Reuven; Smolski, Adam P.; Michielssen, Eric; Mittra, Raj

    1992-02-01

    Large radomes are assembled from many panels connected together forming joints or seams. When the panels are type A sandwiches that are optimized for minimum transmission loss over moderately narrow bandwidths, the seams and joints introduce scattering effects that can degrade the overall electromagnetic performance. Tuning the dielectric seams with conductive wires and optimizing their geometry is, therefore, crucial to enhancing the electromagnetic performance of the radome. The authors address the problem of systematically tuning the dielectric seams and present both numerical and experimental results to illustrate the tuning procedure. Included are results showing the effect of the tuning of the radome on the radiation of an enclosed aperture of circular or elliptic shape.

  15. Diffusion bonding of titanium-titanium aluminide-alumina sandwich

    SciTech Connect

    Wickman, H.A.; Chin, E.S.C.; Biederman, R.R.

    1995-12-31

    Diffusion bonding of a metallic-intermetallic-ceramic sandwich is of interest for potential armor applications. Low cost titanium, titanium diboride reinforced titanium aluminide (Ti-48at.%Al), and aluminum oxide are diffusion bonded in a vacuum furnace between 1,000 C and 1,400 C. Metallographic examination of the prior bonding interface showed excellent metallurgical coupling between the Ti-48at.%Al composite and the low cost Ti. A series of microstructures representative of phases consistent with a hypothetical Ti-Al-B phase diagram is visible. The alumina-Ti-48at.%Al interfacial bond is achieved through penetration of titanium-aluminum phases into the existing alumina porosity. A detailed microstructural analysis identifying mechanisms of interfacial bonding will be presented for each interfacial zone.

  16. Probabilistic Structural Evaluation of Uncertainties in Radiator Sandwich Panel Design

    NASA Technical Reports Server (NTRS)

    Kuguoglu, Latife; Ludwiczak, Damian

    2006-01-01

    The Jupiter Icy Moons Orbiter (JIMO) Space System is part of the NASA's Prometheus Program. As part of the JIMO engineering team at NASA Glenn Research Center, the structural design of the JIMO Heat Rejection Subsystem (HRS) is evaluated. An initial goal of this study was to perform sensitivity analyses to determine the relative importance of the input variables on the structural responses of the radiator panel. The desire was to let the sensitivity analysis information identify the important parameters. The probabilistic analysis methods illustrated here support this objective. The probabilistic structural performance evaluation of a HRS radiator sandwich panel was performed. The radiator panel structural performance was assessed in the presence of uncertainties in the loading, fabrication process variables, and material properties. The stress and displacement contours of the deterministic structural analysis at mean probability was performed and results presented. It is followed by a probabilistic evaluation to determine the effect of the primitive variables on the radiator panel structural performance. Based on uncertainties in material properties, structural geometry and loading, the results of the displacement and stress analysis are used as an input file for the probabilistic analysis of the panel. The sensitivity of the structural responses, such as maximum displacement and maximum tensile and compressive stresses of the facesheet in x and y directions and maximum VonMises stresses of the tube, to the loading and design variables is determined under the boundary condition where all edges of the radiator panel are pinned. Based on this study, design critical material and geometric parameters of the considered sandwich panel are identified.

  17. A Novel Sandwich Electrochemical Immunosensor Based on the DNA-Derived Magnetic Nanochain Probes for Alpha-Fetoprotein

    PubMed Central

    Gan, Ning; Jia, Liyong; Zheng, Lei

    2011-01-01

    One novel electrochemical immunosensor was constructed by immobilizing capture antibody of alpha-fetoprotein (AFP Ab1) on a nafion/nanogold-particle modified glassy carbon electrode. With a sandwich immunoassay, one DNA-derived magnetic nanoprobe, simplified as DNA/(ZMPs—HRP-AFP Ab2)n, was employed for the detection of AFP. The fabricated procedure of the proposed biosensor was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The performance and factors influencing the performance of the biosensor were also evaluated. Under optimal conditions, the developed biosensor exhibited a well-defined electrochemical behavior toward the reduction of AFP ranging from 0.01 to 200 ng/mL with a detection limit of 4 pg/mL (S/N = 3). The biosensor was applied to the determination of AFP in serum with satisfactory results. It is important to note that the sandwich nanochainmodified electro-immunosensor provided an alternative substrate for the immobilization of other tumor markers. PMID:22013390

  18. Experimental study of the mechanical behaviour of pin reinforced foam core sandwich materials under shear load

    NASA Astrophysics Data System (ADS)

    Dimassi, M. A.; Brauner, C.; Herrmann, A. S.

    2016-03-01

    Sandwich structures with a lightweight closed cell hard foam core have the potential to be used in primary structures of commercial aircrafts. Compared to honeycomb core sandwich, the closed cell foam core sandwich overcomes the issue of moisture take up and makes the manufacturing of low priced and highly integrated structures possible. However, lightweight foam core sandwich materials are prone to failure by localised external loads like low velocity impacts. Invisible cracks could grow in the foam core and threaten the integrity of the structure. In order to enhance the out-of-plane properties of foam core sandwich structures and to improve the damage tolerance (DT) dry fibre bundles are inserted in the foam core. The pins are infused with resin and co-cured with the dry fabric face sheets in an out-of-autoclave process. This study presents the results obtained from shear tests following DIN 53294-standard, on flat sandwich panels. All panels were manufactured with pin-reinforcement manufactured with the Tied Foam Core Technology (TFC) developed by Airbus. The effects of pin material (CFRP and GFRP) and pin volume fraction on the shear properties of the sandwich structure and the crack propagation were investigated and compared to a not pinned reference. It has been concluded that the pin volume fraction has a remarkable effect on the shear properties and damage tolerance of the observed structure. Increasing the pin volume fraction makes the effect of crack redirection more obvious and conserves the integrity of the structure after crack occurrence.

  19. Effect of gamma irradiation on Listeria monocytogenes in frozen, artificially contaminated sandwiches.

    PubMed

    Clardy, S; Foley, D M; Caporaso, F; Calicchia, M L; Prakash, A

    2002-11-01

    Gamma irradiation has been shown to effectively control L monocytogenes in uncooked meats but has not been extensively studied in ready-to-eat foods. The presence of Listeria in ready-to-eat foods is often due to postprocess contamination by organisms in the food-manufacturing environment. Because gamma irradiation is applied after products are packaged, the treated foods are protected from environmental recontamination. Currently, a petition to allow gamma irradiation of ready-to-eat foods is under review by the Food and Drug Administration. This study was conducted to determine if gamma irradiation could be used to control L. monocytogenes in ready-to-eat sandwiches. Ham and cheese sandwiches were contaminated with L. monocytogenes, frozen at -40 degrees C, and exposed to gamma irradiation. Following irradiation, sandwiches were assayed for L. monocytogenes. A triangle test was performed to determine if irradiated and nonirradiated sandwiches differed in sensory quality. We found that the D10-values ranged from 0.71 to 0.81 kGy and that a 5-log reduction would require irradiation with 3.5 to 4.0 kGy. The results of a 39-day storage study of sandwiches inoculated with 10(7) CFU of L monocytogenes per g indicated that counts for nonirradiated sandwiches remained fairly constant. Counts for sandwiches treated with 3.9 kGy decreased by 5 log units initially and then decreased further during storage at 4 degrees C. Sensory panelists could distinguish between irradiated and nonirradiated sandwiches but were divided on whether irradiation adversely affected sandwich quality. Our results suggest that manufacturers of ready-to-eat foods could use gamma irradiation to control L. monocytogenes and improve the safety of their products.

  20. Sandwiched confinement of quantum dots in graphene matrix for efficient electron transfer and photocurrent production

    PubMed Central

    Zhu, Nan; Zheng, Kaibo; Karki, Khadga J.; Abdellah, Mohamed; Zhu, Qiushi; Carlson, Stefan; Haase, Dörthe; Žídek, Karel; Ulstrup, Jens; Canton, Sophie E.; Pullerits, Tõnu; Chi, Qijin

    2015-01-01

    Quantum dots (QDs) and graphene are both promising materials for the development of new-generation optoelectronic devices. Towards this end, synergic assembly of these two building blocks is a key step but remains a challenge. Here, we show a one-step strategy for organizing QDs in a graphene matrix via interfacial self-assembly, leading to the formation of sandwiched hybrid QD-graphene nanofilms. We have explored structural features, electron transfer kinetics and photocurrent generation capacity of such hybrid nanofilms using a wide variety of advanced techniques. Graphene nanosheets interlink QDs and significantly improve electronic coupling, resulting in fast electron transfer from photoexcited QDs to graphene with a rate constant of 1.3 × 109 s−1. Efficient electron transfer dramatically enhances photocurrent generation in a liquid-junction QD-sensitized solar cell where the hybrid nanofilm acts as a photoanode. We thereby demonstrate a cost-effective method to construct large-area QD-graphene hybrid nanofilms with straightforward scale-up potential for optoelectronic applications. PMID:25996307

  1. Sandwiched confinement of quantum dots in graphene matrix for efficient electron transfer and photocurrent production

    NASA Astrophysics Data System (ADS)

    Zhu, Nan; Zheng, Kaibo; Karki, Khadga J.; Abdellah, Mohamed; Zhu, Qiushi; Carlson, Stefan; Haase, Dörthe; Žídek, Karel; Ulstrup, Jens; Canton, Sophie E.; Pullerits, Tõnu; Chi, Qijin

    2015-05-01

    Quantum dots (QDs) and graphene are both promising materials for the development of new-generation optoelectronic devices. Towards this end, synergic assembly of these two building blocks is a key step but remains a challenge. Here, we show a one-step strategy for organizing QDs in a graphene matrix via interfacial self-assembly, leading to the formation of sandwiched hybrid QD-graphene nanofilms. We have explored structural features, electron transfer kinetics and photocurrent generation capacity of such hybrid nanofilms using a wide variety of advanced techniques. Graphene nanosheets interlink QDs and significantly improve electronic coupling, resulting in fast electron transfer from photoexcited QDs to graphene with a rate constant of 1.3 × 109 s-1. Efficient electron transfer dramatically enhances photocurrent generation in a liquid-junction QD-sensitized solar cell where the hybrid nanofilm acts as a photoanode. We thereby demonstrate a cost-effective method to construct large-area QD-graphene hybrid nanofilms with straightforward scale-up potential for optoelectronic applications.

  2. Sandwiched confinement of quantum dots in graphene matrix for efficient electron transfer and photocurrent production.

    PubMed

    Zhu, Nan; Zheng, Kaibo; Karki, Khadga J; Abdellah, Mohamed; Zhu, Qiushi; Carlson, Stefan; Haase, Dörthe; Žídek, Karel; Ulstrup, Jens; Canton, Sophie E; Pullerits, Tõnu; Chi, Qijin

    2015-05-21

    Quantum dots (QDs) and graphene are both promising materials for the development of new-generation optoelectronic devices. Towards this end, synergic assembly of these two building blocks is a key step but remains a challenge. Here, we show a one-step strategy for organizing QDs in a graphene matrix via interfacial self-assembly, leading to the formation of sandwiched hybrid QD-graphene nanofilms. We have explored structural features, electron transfer kinetics and photocurrent generation capacity of such hybrid nanofilms using a wide variety of advanced techniques. Graphene nanosheets interlink QDs and significantly improve electronic coupling, resulting in fast electron transfer from photoexcited QDs to graphene with a rate constant of 1.3 × 10(9) s(-1). Efficient electron transfer dramatically enhances photocurrent generation in a liquid-junction QD-sensitized solar cell where the hybrid nanofilm acts as a photoanode. We thereby demonstrate a cost-effective method to construct large-area QD-graphene hybrid nanofilms with straightforward scale-up potential for optoelectronic applications.

  3. Flame structure of sandwich systems based on ammonium perchlorate, HMX and polybutadiene rubber studied by probe mass-spectrometry and modeling

    SciTech Connect

    Chernov, A.A.; Shvartsberg, V.M.; Ermolin, N.E.

    1994-12-31

    The structure of subatmospheric flames of sandwich-type systems consisting of alternating laminae of ammonium perchlorate (AP) or HMX and {open_quotes}base{close_quotes} (polymerized mixture of fine-grained AP and polybutadiene binder) has been studied. The burning surface shape as well as the profiles of concentrations for 17 stable components and of temperature for three crosssections corresponding to the middle of {open_quotes}base{close_quotes} lamina, and to the interface between the laminae have been determined. The hypothesis assuming the existence of three types of flames in sandwiches has been verified experimentally. A concentration gradient of fuel components has been observed at the burning surface of the oxidizer, directed towards the burning surface. Multizone structures and step-by-step mechanisms of reactions in AP and HMX flames have been confirmed. A numerical study for the flame structure of sandwich system based on AP and {open_quotes}base{close_quotes} have been carried out. A simplified set of equations obtained from a complete Navier-Stokes set with the limiting transition M {yields} O have been used in order to construct a solution. Satisfactory agreement between calculated and experimental data on flame structure have been obtained.

  4. Novel electrochemical dual-aptamer-based sandwich biosensor using molybdenum disulfide/carbon aerogel composites and Au nanoparticles for signal amplification.

    PubMed

    Fang, Lin-Xia; Huang, Ke-Jing; Liu, Yang

    2015-09-15

    A new electrochemical aptamer biosensor for the platelet-derived growth factor BB (PDGF-BB) detection has been developed based on the signal amplification of MoS2/carbon aerogel composites (MoS2/CA) and sandwich assay. A facile hydrothermal route assisted by L-cysteine was applied to synthesize CA incorporated flower-like MoS2 with the large surface active sites and good conductivity. The electrochemical aptasensor was constructed by sandwiching the PDGF-BB between a glassy carbon electrode modified with thiol-terminated PDGF-BB aptamer-1 (Apt1)/gold nanoparticles (AuNPs)/MoS2/CA and the AuNPs with thiol-terminated PDGF-BB aptamer-2 (Apt2) and 6-ferrocenyl hexanethiol (Fc). Fc-AuNPs-Apt2 acted as tracer and AuNPs/MoS2/CA were utilized as the biosensor platform to immobilize a large amount of capture aptamers, owing to their layered structure and high surface-to-volume ratio. Based on the sandwich format, a dual signal amplification strategy had been successfully developed with a wide linear response in the range of 0.001-10nM and a limit of detection of 0.3 pM. The developed assay demonstrated good selectivity and high sensitivity, indicating potential applications in bioanalysis and biomedicine.

  5. Elastic constants for superplastically formed/diffusion-bonded corrugated sandwich core

    NASA Technical Reports Server (NTRS)

    Ko, W. L.

    1980-01-01

    Formulas and associated graphs for evaluating the effective elastic constants for a superplastically formed/diffusion bonded (SPF/DB) corrugated sandwich core, are presented. A comparison of structural stiffnesses of the sandwich core and a honeycomb core under conditions of equal sandwich core density was made. The stiffness in the thickness direction of the optimum SPF/DB corrugated core (that is, triangular truss core) is lower than that of the honeycomb core, and that the former has higher transverse shear stiffness than the latter.

  6. Meshless Analysis of Laminated Composite and Sandwich Plates Subjected to Various Types of Loads

    NASA Astrophysics Data System (ADS)

    Singh, Jeeoot; Singh, Sandeep; Shukla, K. K.

    2014-03-01

    The bending analysis of laminated composite and sandwich plates using different radial basis functions and higher-order shear deformation theory is presented. This meshfree technique is insensitive to spatial dimension and considers only a cloud of nodes (centers) for the spatial discretization of both the problem domain and the boundary. Numerical results for simply supported isotropic, symmetric cross-ply composite and sandwich plate are presented. The results are compared with other available results. It is observed that convergence of the polynomial function is faster as compared to other radial basis functions, whereas Gaussian function takes the least solution time. The effect of various types of loadings on sandwich plate is presented.

  7. A comparative study of the impact properties of sandwich materials with different cores

    NASA Astrophysics Data System (ADS)

    Ramakrishnan, K. R.; Shankar, K.; Viot, P.; Guerard, S.

    2012-08-01

    Sandwich panels are made of two high strength skins bonded to either side of a light weight core and are used in applications where high stiffness combined with low structural weight is required. The purpose of this paper is to compare the mechanical response of several sandwich panels whose core materials are different. Sandwich panels with glass fibre-reinforced polymer face sheets were used, combined with five different cores; polystyrene foam, polypropylene honeycomb, two different density Balsa wood and Cork. All specimens were subjected to low velocity impact and their structural response (Force-displacement curves) were compared to quasistatic response of the panel tested using an hemispherical indenter.

  8. Design Considerations for Thermally Insulating Structural Sandwich Panels for Hypersonic Vehicles

    NASA Technical Reports Server (NTRS)

    Blosser, Max L.

    2016-01-01

    Simplified thermal/structural sizing equations were derived for the in-plane loading of a thermally insulating structural sandwich panel. Equations were developed for the strain in the inner and outer face sheets of a sandwich subjected to uniaxial mechanical loads and differences in face sheet temperatures. Simple equations describing situations with no viable solution were developed. Key design parameters, material properties, and design principles are identified. A numerical example illustrates using the equations for a preliminary feasibility assessment of various material combinations and an initial sizing for minimum mass of a sandwich panel.

  9. Response of Honeycomb Core Sandwich Panel with Minimum Gage GFRP Face-Sheets to Compression Loading After Impact

    NASA Technical Reports Server (NTRS)

    McQuigg, Thomas D.; Kapania, Rakesh K.; Scotti, Stephen J.; Walker, Sandra P.

    2011-01-01

    A compression after impact study has been conducted to determine the residual strength of three sandwich panel constructions with two types of thin glass fiber reinforced polymer face-sheets and two hexagonal honeycomb Nomex core densities. Impact testing is conducted to first determine the characteristics of damage resulting from various impact energy levels. Two modes of failure are found during compression after impact tests with the density of the core precipitating the failure mode present for a given specimen. A finite element analysis is presented for prediction of the residual compressive strength of the impacted specimens. The analysis includes progressive damage modeling in the face-sheets. Preliminary analysis results were similar to the experimental results; however, a higher fidelity core material model is expected to improve the correlation.

  10. Analysis and Tests of Reinforced Carbon-Epoxy/Foam-Core Sandwich Panels with Cutouts

    NASA Technical Reports Server (NTRS)

    Baker, Donald J.; Rogers, Charles

    1996-01-01

    The results of a study of a low-cost structurally efficient minimum-gage shear-panel design that can be used in light helicopters are presented. The shear-panel design is based on an integrally stiffened syntactic-foam stabilized-skin with an all-bias-ply tape construction for stabilized-skin concept with an all-bias-ply tape construction for the skins. This sandwich concept is an economical way to increase the panel bending stiffness weight penalty. The panels considered in the study were designed to be buckling resistant up to 100 lbs/in. of shear load and to have an ultimate strength of 300 lbs/in. The panel concept uses unidirectional carbon-epoxy tape on a syntactic adhesive as a stiffener that is co-cured with the skin and is an effective concept for improving panel buckling strength. The panel concept also uses pultruded carbon-epoxy rods embedded in a syntactic adhesive and over-wrapped with a bias-ply carbon-epoxy tape to form a reinforcing beam which is an effective method for redistributing load around rectangular cutout. The buckling strength of the reinforced panels is 83 to 90 percent of the predicted buckling strength based on a linear buckling analysis. The maximum experimental deflection exceeds the maximum deflection predicted by a nonlinear analysis by approximately one panel thickness. The failure strength of the reinforced panels was two and a half to seven times of the buckling strength. This efficient shear-panel design concept exceeds the required ultimate strength requirement of 300 lbs/in by more than 100 percent.

  11. A variable transverse stiffness sandwich structure using fluidic flexible matrix composites (F2MC)

    NASA Astrophysics Data System (ADS)

    Li, Suyi; Lotfi, Amir; Shan, Ying; Wang, K. W.; Rahn, Christopher D.; Bakis, Charles E.

    2008-03-01

    Presented in this paper is the development of a novel honeycomb sandwich panel with variable transverse stiffness. In this structure, the traditional sandwich face sheets are replaced by the fluidic flexible matrix composite (F2MC) tube layers developed in recent studies. The F2MC layers, combined with the anisotropic honeycomb core material properties, provide a new sandwich structure with variable stiffness properties for transverse loading. In this research, an analytical model is derived based on Lekhitskii's anisotropic pressurized tube solution and Timoshenko beam theory. Experimental investigations are also conducted to verify the analytical findings. A segmented multiple-F2MC-tube configuration is synthesized to increase the variable stiffness range. The analysis shows that the new honeycomb sandwich structure using F2MC tubes of 10 segments can provide a high/low transverse stiffness ratio of 60. Segmentation and stiffness control can be realized by an embedded valve network, granting a fast response time.

  12. Quantitative surface enhanced Raman scattering detection based on the ``sandwich'' structure substrate

    NASA Astrophysics Data System (ADS)

    Zhang, Junmeng; Qu, Shengchun; Zhang, Lisheng; Tang, Aiwei; Wang, Zhanguo

    2011-08-01

    A sandwich structured substrate was designed for quantitative molecular detection using surface enhanced Raman scattering (SERS), in which the probe molecule was sandwiched between silver nanoparticles (SNPs) and silver nanoarrays. The SNPs was prepared using Lee-Meisel method, and the silver nanoarrays was fabricated on porous anodic aluminum oxide (AAO) using electrodepositing method. The SERS studies show that the sandwich structured substrate exhibits good stability and reproducibility, and the detection sensitivity of Rhodamine 6G (R6G) and Melamine can respectively reach up to 10 -19 M and 10 -9 M, which is improved greatly as compared to other SERS substrates. The improved SERS sensitivity is closely associated with the stronger electromagnetic field enhancement, which stems from localized surface plasmon (LSP) coupling between the two silver nanostructures. Furthermore, the SERS intensity increased almost linearly as the mother concentration increased, which indicates that such a sandwich structure may be used as a good SERS substrate for quantitative analysis.

  13. Interfacial Crack Arrest in Sandwich Panels with Embedded Crack Stoppers Subjected to Fatigue Loading

    NASA Astrophysics Data System (ADS)

    Martakos, G.; Andreasen, J. H.; Berggreen, C.; Thomsen, O. T.

    2016-08-01

    A novel crack arresting device has been implemented in sandwich panels and tested using a special rig to apply out-of-plane loading on the sandwich panel face-sheets. Fatigue crack propagation was induced in the face-core interface of the sandwich panels which met the crack arrester. The effect of the embedded crack arresters was evaluated in terms of the achieved enhancement of the damage tolerance of the tested sandwich panels. A finite element (FE) model of the experimental setup was used for predicting propagation rates and direction of the crack growth. The FE simulation was based on the adoption of linear fracture mechanics and a fatigue propagation law (i.e. Paris law) to predict the residual fatigue life-time and behaviour of the test specimens. Finally, a comparison between the experimental results and the numerical simulations was made to validate the numerical predictions as well as the overall performance of the crack arresters.

  14. An Investigation on Low Velocity Impact Response of Multilayer Sandwich Composite Structures

    PubMed Central

    Jedari Salami, S.; Sadighi, M.; Shakeri, M.; Moeinfar, M.

    2013-01-01

    The effects of adding an extra layer within a sandwich panel and two different core types in top and bottom cores on low velocity impact loadings are studied experimentally in this paper. The panel includes polymer composite laminated sheets for faces and the internal laminated sheet called extra layer sheet, and two types of crushable foams are selected as the core material. Low velocity impact tests were carried out by drop hammer testing machine to the clamped multilayer sandwich panels with expanded polypropylene (EPP) and polyurethane rigid (PUR) in the top and bottom cores. Local displacement of the top core, contact force and deflection of the sandwich panel were obtained for different locations of the internal sheet; meanwhile the EPP and PUR were used in the top and bottom cores alternatively. It was found that the core material type has made significant role in improving the sandwich panel's behavior compared with the effect of extra layer location. PMID:24453804

  15. Investigation of out of plane compressive strength of 3D printed sandwich composites

    NASA Astrophysics Data System (ADS)

    Dikshit, V.; Yap, Y. L.; Goh, G. D.; Yang, H.; Lim, J. C.; Qi, X.; Yeong, W. Y.; Wei, J.

    2016-07-01

    In this study, the 3D printing technique was utilized to manufacture the sandwich composites. Composite filament fabrication based 3D printer was used to print the face-sheet, and inkjet 3D printer was used to print the sandwich core structure. This work aims to study the compressive failure of the sandwich structure manufactured by using these two manufacturing techniques. Two different types of core structures were investigated with the same type of face-sheet configuration. The core structures were printed using photopolymer, while the face-sheet was made using nylon/glass. The out-of-plane compressive strength of the 3D printed sandwich composite structure has been examined in accordance with ASTM standards C365/C365-M and presented in this paper.

  16. An expression of within-plate uncertainty in sandwich ELISA.

    PubMed

    Hayashi, Yuzuru; Matsuda, Rieko; Maitani, Tamio; Ito, Katsutoshi; Nishimura, Waka; Imai, Kazuhiro; Maeda, Masako

    2004-09-21

    This paper puts forward a method to describe an equation of the within-plate uncertainty (relative standard deviation (R.S.D.) of measurements) as a function of analyte concentration in sandwich enzyme-linked immunosorbent assay (ELISA). A kit for thyroid stimulating hormone is taken as an example. The pipetting procedures of analyte solution and chromogen-substrate solution and absorbance inherent to the wells of a microplate are identified as major error sources and their variability is included as parameters in the uncertainty equation. These parameters can be determined by the experiments with distilled water. The theoretical R.S.D. is shown to be in good agreement with the results of the repeated experiments using the real samples. Since the theory gives a continuous plot of R.S.D. against concentration, the uncertainty structure of the ELISA kit can be recognized over a wide concentration range and the detection limit and quantitation range can easily be determined on the plot.

  17. γ-Cyclodextrin cuprate sandwich-type complexes.

    PubMed

    Bagabas, Abdulaziz A; Frasconi, Marco; Iehl, Julien; Hauser, Brad; Farha, Omar K; Hupp, Joseph T; Hartlieb, Karel J; Botros, Youssry Y; Stoddart, J Fraser

    2013-03-18

    Three structures, based on γ-cyclodextrin (γ-CD) and metal ions (Cu(2+), Li(+), Na(+), and Rb(+)), have been prepared in aqueous and alkaline media and characterized structurally by single-crystal X-ray diffraction. Their dimeric assemblies adopt cylindrical channels along the c axes in the crystals. Coordinative and hydrogen bonding between the cylinders and the solvent molecules lead to the formation of two-dimensional sheets, with the identity of the alkali-metal ion strongly influencing the precise nature of the solid-state structures. In the case of the Rb(+) complex, coordinative bonding involving the Rb(+) ions leads to the formation of an extended two-dimensional structure. Nonbound solvent molecules can be removed, and gas isotherm analyses confirm the permanent porosity of these new complexes. Carbon dioxide (CO2) adsorption studies show that the extended structure, obtained upon crystallization of the Rb(+)-based sandwich-type dimers, has the highest CO2 sequestration ability of the three γ-CD complexes reported. PMID:23432138

  18. Dispersion of Lamb waves in a honeycomb composite sandwich panel.

    PubMed

    Baid, Harsh; Schaal, Christoph; Samajder, Himadri; Mal, Ajit

    2015-02-01

    Composite materials are increasingly being used in advanced aircraft and aerospace structures. Despite their many advantages, composites are often susceptible to hidden damages that may occur during manufacturing and/or service of the structure. Therefore, safe operation of composite structures requires careful monitoring of the initiation and growth of such defects. Ultrasonic methods using guided waves offer a reliable and cost effective method for defects monitoring in advanced structures due to their long propagation range and their sensitivity to defects in their propagation path. In this paper, some of the useful properties of guided Lamb type waves are investigated, using analytical, numerical and experimental methods, in an effort to provide the knowledge base required for the development of viable structural health monitoring systems for composite structures. The laboratory experiments involve a pitch-catch method in which a pair of movable transducers is placed on the outside surface of the structure for generating and recording the wave signals. The specific cases considered include an aluminum plate, a woven composite laminate and an aluminum honeycomb sandwich panel. The agreement between experimental, numerical and theoretical results are shown to be excellent in certain frequency ranges, providing a guidance for the design of effective inspection systems. PMID:25287973

  19. Sandwich module prototype progress for space solar power

    NASA Astrophysics Data System (ADS)

    Jaffe, Paul; Hodkin, Jason; Harrington, Forest; Person, Clark; Nurnberger, Michael; Nguyen, Bang; LaCava, Susie; Scheiman, Dave; Stewart, Grant; Han, Andrew; Hettwer, Ethan; Rhoades, Daniel

    2014-02-01

    Space solar power (SSP) has been broadly defined as the collection of solar energy in space and its wireless transmission for use on earth. This approach potentially gives the benefit of provision of baseload power while avoiding the losses due to the day/night cycle and tropospheric effects that are associated with terrestrial solar power. Proponents have contended that the implementation of such systems could offer energy security, environmental, and technological advantages to those who would undertake their development. Among recent implementations commonly proposed for SSP, the modular symmetrical concentrator (MSC) and other modular concepts have received considerable attention. Each employs an array of modules for performing conversion of concentrated sunlight into microwaves or laser beams for transmission to earth. While prototypes of such modules have been designed and developed previously by several groups, none have been subjected to the challenging conditions inherent to the space environment and the possible solar concentration levels in which an array of modules might be required to operate. The research described herein details our team's efforts in the development of photovoltaic arrays, power electronics, microwave conversion electronics, and antennas for microwave-based "sandwich" module prototypes. The implementation status and testing results of the prototypes are reviewed.

  20. Variable stiffness sandwich panels using electrostatic interlocking core

    NASA Astrophysics Data System (ADS)

    Heath, Callum J. C.; Bond, Ian P.; Potter, Kevin D.

    2016-04-01

    Structural topology has a large impact on the flexural stiffness of a beam structure. Reversible attachment between discrete substructures allows for control of shear stress transfer between structural elements, thus stiffness modulation. Electrostatic adhesion has shown promise for providing a reversible latching mechanism for controllable internal connectivity. Building on previous research, a thin film copper polyimide laminate has been used to incorporate high voltage electrodes to Fibre Reinforced Polymer (FRP) sandwich structures. The level of electrostatic holding force across the electrode interface is key to the achievable level of stiffness modulation. The use of non-flat interlocking core structures can allow for a significant increase in electrode contact area for a given core geometry, thus a greater electrostatic holding force. Interlocking core geometries based on cosine waves can be Computer Numerical Control (CNC) machined from Rohacell IGF 110 Foam core. These Interlocking Core structures could allow for enhanced variable stiffness functionality compared to basic planar electrodes. This novel concept could open up potential new applications for electrostatically induced variable stiffness structures.

  1. Characterizing Facesheet/Core Disbonding in Honeycomb Core Sandwich Structure

    NASA Technical Reports Server (NTRS)

    Rinker, Martin; Ratcliffe, James G.; Adams, Daniel O.; Krueger, Ronald

    2013-01-01

    Results are presented from an experimental investigation into facesheet core disbonding in carbon fiber reinforced plastic/Nomex honeycomb sandwich structures using a Single Cantilever Beam test. Specimens with three, six and twelve-ply facesheets were tested. Specimens with different honeycomb cores consisting of four different cell sizes were also tested, in addition to specimens with three different widths. Three different data reduction methods were employed for computing apparent fracture toughness values from the test data, namely an area method, a compliance calibration technique and a modified beam theory method. The compliance calibration and modified beam theory approaches yielded comparable apparent fracture toughness values, which were generally lower than those computed using the area method. Disbonding in the three-ply facesheet specimens took place at the facesheet/core interface and yielded the lowest apparent fracture toughness values. Disbonding in the six and twelve-ply facesheet specimens took place within the core, near to the facesheet/core interface. Specimen width was not found to have a significant effect on apparent fracture toughness. The amount of scatter in the apparent fracture toughness data was found to increase with honeycomb core cell size.

  2. An extraterrestrial sandwich: The perils of food in space.

    PubMed

    Levi, Jane

    2010-03-01

    Food was and is an essential component in human space exploration. If it had not proved possible to eat and digest in space, none of the long-term space missions of the last four decades would have been achievable. Every country that has sent an astronaut on a mission has used its national foods as a means of stating both their presence and their identity to their colleagues in the programme and their citizens at home: in space, as on earth, food has provided a means of asserting national culture. From the earliest missions, the US and USSR's differing attitudes to the programme have been reflected in the food provided and the respective administrations' approaches to feeding in space. The contrast between the US focus on space travel and the USSR's focus on space living is highlighted through their attitudes to the often vexed question of what astronauts and cosmonauts should be permitted to eat, illustrated by the corned-beef sandwich incident of 1965.

  3. ''Sandwich'' treatment for diospyrobezoar intestinal obstruction: a case report.

    PubMed

    Zheng, Yi-Xiong; Prasoon, Pankaj; Chen, Yan; Hu, Liang; Chen, Li

    2014-12-28

    Intestinal obstruction is a common clinical entity encountered in surgical practice. The objective of this report is to corroborate an atypical scenario of intestinal obstruction in a Chinese patient and to focus on the diagnosis and treatment. A 27-year-old male presented with a history of gastric pain combined with nausea and abdominal distension that had been present for 5 d. The presence of a foreign body was detected by computed tomography and observed as an abnormal density within the stomach. A diospyrobezoar was revealed during gastroscopy, the extraction of which was prevented due to its size and firmness. An endoscopic holmium laser joined with a snare was used to fragment the obstruction, which was followed by management with a conservative "sandwich" treatment strategy involving intestinal decompression with an ileus tube and Coca-Cola lavage between endoscopic lithotripsy fragmentation procedures. This strategy resulted in the successful removal of the diospyrobezoar along with multiple small bowel obstructions. The patient was discharged after abatement of symptoms. The case presented here demonstrates the implementation of a conservative, yet successful, treatment as an alternative to conventional surgical removal of intestinal obstructions. PMID:25561823

  4. Refined Zigzag Theory for Laminated Composite and Sandwich Plates

    NASA Technical Reports Server (NTRS)

    Tessler, Alexander; DiSciuva, Marco; Gherlone, Marco

    2009-01-01

    A refined zigzag theory is presented for laminated-composite and sandwich plates that includes the kinematics of first-order shear deformation theory as its baseline. The theory is variationally consistent and is derived from the virtual work principle. Novel piecewise-linear zigzag functions that provide a more realistic representation of the deformation states of transverse-shear-flexible plates than other similar theories are used. The formulation does not enforce full continuity of the transverse shear stresses across the plate s thickness, yet is robust. Transverse-shear correction factors are not required to yield accurate results. The theory is devoid of the shortcomings inherent in the previous zigzag theories including shear-force inconsistency and difficulties in simulating clamped boundary conditions, which have greatly limited the accuracy of these theories. This new theory requires only C(sup 0)-continuous kinematic approximations and is perfectly suited for developing computationally efficient finite elements. The theory should be useful for obtaining relatively efficient, accurate estimates of structural response needed to design high-performance load-bearing aerospace structures.

  5. Dispersion of Lamb waves in a honeycomb composite sandwich panel.

    PubMed

    Baid, Harsh; Schaal, Christoph; Samajder, Himadri; Mal, Ajit

    2015-02-01

    Composite materials are increasingly being used in advanced aircraft and aerospace structures. Despite their many advantages, composites are often susceptible to hidden damages that may occur during manufacturing and/or service of the structure. Therefore, safe operation of composite structures requires careful monitoring of the initiation and growth of such defects. Ultrasonic methods using guided waves offer a reliable and cost effective method for defects monitoring in advanced structures due to their long propagation range and their sensitivity to defects in their propagation path. In this paper, some of the useful properties of guided Lamb type waves are investigated, using analytical, numerical and experimental methods, in an effort to provide the knowledge base required for the development of viable structural health monitoring systems for composite structures. The laboratory experiments involve a pitch-catch method in which a pair of movable transducers is placed on the outside surface of the structure for generating and recording the wave signals. The specific cases considered include an aluminum plate, a woven composite laminate and an aluminum honeycomb sandwich panel. The agreement between experimental, numerical and theoretical results are shown to be excellent in certain frequency ranges, providing a guidance for the design of effective inspection systems.

  6. Piezoelectric performance of fluor polymer sandwiches with different void structures

    NASA Astrophysics Data System (ADS)

    Lou, Kexing; Zhang, Xiaoqing; Xia, Zhongfu

    2012-06-01

    Film sandwiches, consisting of two outer layers of fluoroethylenepropylene and one middle layer of patterned porous polytetrafluoroethylene, were prepared by patterning and fusion bonding. Contact charging was conducted to render the films piezoelectric. The critical voltage to trigger air breakdown in the inner voids in the fabricated films was investigated. The piezoelectric d 33 coefficients were measured employing the quasistatic method and dielectric resonance spectrum. The results show that the critical voltage for air breakdown in the inner voids is associated with the void microstructure of the films. For the films with patterning factors of 0%, 25% and 44%, the critical values are 300, 230 and 230 kV/cm, respectively. With an increase in the patterning factor, both the piezoelectric d 33 coefficients determined from the dielectric resonance spectra and those determined from quasistatic measurements increase, which might be due to a decrease in Young's modulus for the films. The nonlinearity of d 33 becomes increasingly obvious as the patterning factor increases.

  7. Multiscale Modeling Methods for Analysis of Failure Modes in Foldcore Sandwich Panels

    NASA Astrophysics Data System (ADS)

    Sturm, R.; Schatrow, P.; Klett, Y.

    2015-12-01

    The paper presents an homogenised core model suitable for use in the analysis of fuselage sandwich panels with folded composite cores under combined loading conditions. Within a multiscale numerical design process a failure criterion was derived for describing the macroscopic behaviour of folded cores under combined loading using a detailed foldcore micromodel. The multiscale modelling method was validated by simulation of combined compression/bending failure of foldcore sandwich panels.

  8. Sandwich ELISA Microarrays: Generating Reliable and Reproducible Assays for High-Throughput Screens

    SciTech Connect

    Gonzalez, Rachel M.; Varnum, Susan M.; Zangar, Richard C.

    2009-05-11

    The sandwich ELISA microarray is a powerful screening tool in biomarker discovery and validation due to its ability to simultaneously probe for multiple proteins in a miniaturized assay. The technical challenges of generating and processing the arrays are numerous. However, careful attention to possible pitfalls in the development of your antibody microarray assay can overcome these challenges. In this chapter, we describe in detail the steps that are involved in generating a reliable and reproducible sandwich ELISA microarray assay.

  9. Development of a finite element model for the simulation of parabolic impact of sandwich panels

    NASA Astrophysics Data System (ADS)

    Ram Ramakrishnan, Karthik; Guérard, Sandra; Mahéo, Laurent; Shankar, Krishna; Viot, Philippe

    2015-09-01

    Sandwich panels are lightweight structures of two thin high strength facesheets bonded to either side of a thick low density core such as foams and honeycombs. It is necessary to study the impact response of sandwich structures in order to ensure the reliability and safety of these structures. The response of sandwich panels to impact loading is usually studied for impact at normal angle of incidence. In real engineering situations, the structures are more frequently loaded at some oblique angle or with a complex trajectory. It is easy to carry out normal impact tests using devices like the drop tower, but impacts at oblique angles are difficult to characterise experimentally. A tri-dimensional impact device called Hexapod has been developed to experimentally study the impact loading of sandwich plates with a parabolic trajectory. The Hexapod is a modified Gough-Stewart platform that can be moved independently in the six degrees of freedom, corresponding to three translation axes and three rotation axes. In this paper, an approach for modelling the parabolic impact of sandwich structures with thin metallic facesheets and polymer foam core using commercial finite element code LS-DYNA software is presented. The results of the FE model of sandwich panels are compared with experimental data in terms of the time history of vertical and horizontal components of force. A comparison of the strain history obtained from Digital Image Correlation and LS-Dyna model are also presented.

  10. An Analysis of Nondestructive Evaluation Techniques for Polymer Matrix Composite Sandwich Materials

    NASA Technical Reports Server (NTRS)

    Cosgriff, Laura M.; Roberts, Gary D.; Binienda, Wieslaw K.; Zheng, Diahua; Averbeck, Timothy; Roth, Donald J.; Jeanneau, Philippe

    2006-01-01

    Structural sandwich materials composed of triaxially braided polymer matrix composite material face sheets sandwiching a foam core are being utilized for applications including aerospace components and recreational equipment. Since full scale components are being made from these sandwich materials, it is necessary to develop proper inspection practices for their manufacture and in-field use. Specifically, nondestructive evaluation (NDE) techniques need to be investigated for analysis of components made from these materials. Hockey blades made from sandwich materials and a flat sandwich sample were examined with multiple NDE techniques including thermographic, radiographic, and shearographic methods to investigate damage induced in the blades and flat panel components. Hockey blades used during actual play and a flat polymer matrix composite sandwich sample with damage inserted into the foam core were investigated with each technique. NDE images from the samples were presented and discussed. Structural elements within each blade were observed with radiographic imaging. Damaged regions and some structural elements of the hockey blades were identified with thermographic imaging. Structural elements, damaged regions, and other material variations were detected in the hockey blades with shearography. Each technique s advantages and disadvantages were considered in making recommendations for inspection of components made from these types of materials.

  11. Failure Predictions of Out-of-Autoclave Sandwich Joints with Delaminations under Flexure Loads

    NASA Technical Reports Server (NTRS)

    Nordendale, Nikolas; Goyal, Vinay; Lundgren, Eric; Patel, Dhruv; Farrokh, Babak; Jones, Justin; Fischetti, Grace; Segal, Kenneth

    2015-01-01

    An analysis and a test program was conducted to investigate the damage tolerance of composite sandwich joints. The joints contained a single circular delamination between the face-sheet and the doubler. The coupons were fabricated through out-of-autoclave (OOA) processes, a technology NASA is investigating for joining large composite sections. The four-point bend flexure test was used to induce compression loading into the side of the joint where the delamination was placed. The compression side was chosen since it tends to be one of the most critical loads in launch vehicles. Autoclave cure was used to manufacture the composite sandwich sections, while the doubler was co-bonded onto the sandwich face-sheet using an OOA process after sandwich panels were cured. A building block approach was adopted to characterize the mechanical properties of the joint material, including the fracture toughness between the doubler and facesheet. Twelve four-point-bend samples were tested, six in the sandwich core ribbon orientation and six in sandwich core cross-ribbon direction. Analysis predicted failure initiation and propagation at the pre-delaminated location, consistent with experimental observations. A building block approach using fracture analyses methods predicted failure loads in close agreement with tests. This investigation demonstrated a small strength reduction due to a flaw of significant size compared to the width of the sample. Therefore, concerns of bonding an OOA material to an in-autoclave material was mitigated for the geometries, materials, and load configurations considered.

  12. Failure Predictions of Out-of-Autoclave Sandwich Joints with Delaminations Under Flexure Loads

    NASA Technical Reports Server (NTRS)

    Nordendale, Nikolas; Goyal, Vinay; Lundgren, Eric; Patel, Dhruv; Farrokh, Babak; Jones, Justin; Fischetti, Grace; Segal, Kenneth

    2015-01-01

    An analysis and a test program was conducted to investigate the damage tolerance of composite sandwich joints. The joints contained a single circular delamination between the face-sheet and the doubler. The coupons were fabricated through out-of-autoclave (OOA) processes, a technology NASA is investigating for joining large composite sections. The four-point bend flexure test was used to induce compression loading into the side of the joint where the delamination was placed. The compression side was chosen since it tends to be one of the most critical loads in launch vehicles. Autoclave cure was used to manufacture the composite sandwich sections, while the doubler was co-bonded onto the sandwich face-sheet using an OOA process after sandwich panels were cured. A building block approach was adopted to characterize the mechanical properties of the joint material, including the fracture toughness between the doubler and face-sheet. Twelve four-point-bend samples were tested, six in the sandwich core ribbon orientation and six in sandwich core cross-ribbon direction. Analysis predicted failure initiation and propagation at the pre-delaminated location, consistent with experimental observations. Fracture analyses methods predicted failure loads in close agreement with tests. This investigation demonstrated a strength reduction of 10 percent due to a flaw of significant size compared to the width of the sample. Therefore, concerns of bonding an OOA material to an in-autoclave material was mitigated for the geometries, materials, and load configurations considered.

  13. Failure Predictions of Out-of-Autoclave Sandwich Joints with Delaminations Under Flexure Loads

    NASA Technical Reports Server (NTRS)

    Nordendale, Nikolas A.; Goyal, Vinay K.; Lundgren, Eric C.; Patel, Dhruv N.; Farrokh, Babak; Jones, Justin; Fischetti, Grace; Segal, Kenneth N.

    2015-01-01

    An analysis and a test program was conducted to investigate the damage tolerance of composite sandwich joints. The joints contained a single circular delamination between the face-sheet and the doubler. The coupons were fabricated through out-of-autoclave (OOA) processes, a technology NASA is investigating for joining large composite sections. The four-point bend flexure test was used to induce compression loading into the side of the joint where the delamination was placed. The compression side was chosen since it tends to be one of the most critical loads in launch vehicles. Autoclave cure was used to manufacture the composite sandwich sections, while the doubler was co-bonded onto the sandwich face-sheet using an OOA process after sandwich panels were cured. A building block approach was adopted to characterize the mechanical properties of the joint material, including the fracture toughness between the doubler and face-sheet. Twelve four-point-bend samples were tested, six in the sandwich core ribbon orientation and six in sandwich core cross-ribbon direction. Analysis predicted failure initiation and propagation at the pre-delaminated location, consistent with experimental observations. A building block approach using fracture analyses methods predicted failure loads in close agreement with tests. This investigation demonstrated a small strength reduction due to a flaw of significant size compared to the width of the sample. Therefore, concerns of bonding an OOA material to an in-autoclave material was mitigated for the geometries, materials, and load configurations considered.

  14. Dynamic analysis of tapered laminated composite magnetorheological elastomer (MRE) sandwich plates

    NASA Astrophysics Data System (ADS)

    Babu, V. Ramesh; Vasudevan, R.

    2016-03-01

    In the present study, the dynamic performance of the sandwich plate with magneto rheological elastomer (MRE) as the core layer and tapered laminated composite plates as the face layers is investigated. Various MRE tapered laminated composite sandwich plate models are formulated by dropping-off the plies longitudinally in top and bottom composite layers to yield tapered plates as the face layers and uniform MRE layer as the core layer. The governing equations of motion of tapered composite MRE sandwich plates are derived using classical laminated plate theory and solved numerically. Further, silicon based MRE is being fabricated and tested to obtain the shear and loss moduli using MR rheometer. The efficacy of the finite element formulation is validated by carrying out experiments on the various prototypes of tapered composite silicon based MRE sandwich plates and comparing the results in terms of natural frequencies obtained at various magnetic fields with those obtained numerically and with available literature. Also, the effects of magnetic field, taper angle of the top and bottom layers, aspect ratio, ply orientations and various end conditions on the various dynamic properties of tapered laminated composite MRE sandwich plate are investigated. Further, the transverse vibration responses of three different tapered composite MRE based sandwich plates under harmonic force excitation are analyzed at various magnetic fields.

  15. A quantitative exposure model simulating human norovirus transmission during preparation of deli sandwiches.

    PubMed

    Stals, Ambroos; Jacxsens, Liesbeth; Baert, Leen; Van Coillie, Els; Uyttendaele, Mieke

    2015-03-01

    Human noroviruses (HuNoVs) are a major cause of food borne gastroenteritis worldwide. They are often transmitted via infected and shedding food handlers manipulating foods such as deli sandwiches. The presented study aimed to simulate HuNoV transmission during the preparation of deli sandwiches in a sandwich bar. A quantitative exposure model was developed by combining the GoldSim® and @Risk® software packages. Input data were collected from scientific literature and from a two week observational study performed at two sandwich bars. The model included three food handlers working during a three hour shift on a shared working surface where deli sandwiches are prepared. The model consisted of three components. The first component simulated the preparation of the deli sandwiches and contained the HuNoV reservoirs, locations within the model allowing the accumulation of NoV and the working of intervention measures. The second component covered the contamination sources being (1) the initial HuNoV contaminated lettuce used on the sandwiches and (2) HuNoV originating from a shedding food handler. The third component included four possible intervention measures to reduce HuNoV transmission: hand and surface disinfection during preparation of the sandwiches, hand gloving and hand washing after a restroom visit. A single HuNoV shedding food handler could cause mean levels of 43±18, 81±37 and 18±7 HuNoV particles present on the deli sandwiches, hands and working surfaces, respectively. Introduction of contaminated lettuce as the only source of HuNoV resulted in the presence of 6.4±0.8 and 4.3±0.4 HuNoV on the food and hand reservoirs. The inclusion of hand and surface disinfection and hand gloving as a single intervention measure was not effective in the model as only marginal reductions of HuNoV levels were noticeable in the different reservoirs. High compliance of hand washing after a restroom visit did reduce HuNoV presence substantially on all reservoirs. The

  16. A Refined Zigzag Beam Theory for Composite and Sandwich Beams

    NASA Technical Reports Server (NTRS)

    Tessler, Alexander; Sciuva, Marco Di; Gherlone, Marco

    2009-01-01

    A new refined theory for laminated composite and sandwich beams that contains the kinematics of the Timoshenko Beam Theory as a proper baseline subset is presented. This variationally consistent theory is derived from the virtual work principle and employs a novel piecewise linear zigzag function that provides a more realistic representation of the deformation states of transverse-shear flexible beams than other similar theories. This new zigzag function is unique in that it vanishes at the top and bottom bounding surfaces of a beam. The formulation does not enforce continuity of the transverse shear stress across the beam s cross-section, yet is robust. Two major shortcomings that are inherent in the previous zigzag theories, shear-force inconsistency and difficulties in simulating clamped boundary conditions, and that have greatly limited the utility of these previous theories are discussed in detail. An approach that has successfully resolved these shortcomings is presented herein. Exact solutions for simply supported and cantilevered beams subjected to static loads are derived and the improved modelling capability of the new zigzag beam theory is demonstrated. In particular, extensive results for thick beams with highly heterogeneous material lay-ups are discussed and compared with corresponding results obtained from elasticity solutions, two other zigzag theories, and high-fidelity finite element analyses. Comparisons with the baseline Timoshenko Beam Theory are also presented. The comparisons clearly show the improved accuracy of the new, refined zigzag theory presented herein over similar existing theories. This new theory can be readily extended to plate and shell structures, and should be useful for obtaining relatively low-cost, accurate estimates of structural response needed to design an important class of high-performance aerospace structures.

  17. Experimental investigation on sandwich structure ring-type ultrasonic motor.

    PubMed

    Peng, Taijiang; Shi, Hongyan; Liang, Xiong; Luo, Feng; Wu, Xiaoyu

    2015-02-01

    This paper presents a manufacture method for a sandwich structure Ultrasonic Motor (USM) and experiment. Two pieces of rotor clamped on a stator, and a stainless steel disk-spring is bonded on the hollow rotor disk to provide the press by a nut assembled on the shaft. The stator is made of a double-side Printed-Circuit Board (PCB) which is sawed out the ring in the center and connected on the board with three legs. On each side of the ring surface, there are electrodes connected at the same position via through hole. The three layer drive circuit for sine, cosine, and ground signal is connected on the board through each leg. There are many piezoelectric components (PZT) bonded between two electrodes and fill soldering tin on each electrode. Then PZT is welded on PCB by reflow soldering. Finally, rub the gibbous soldering tin down to the position of PZT surface makes sure the surface contacts with rotor evenly. The welding process can also be completed by Surface Mounted Technology (SMT). A prototype motor is manufactured by this method. Two B03 model shapes of the stator are obtained by the finite element analysis and the optimal frequency of the motor is 56.375 kHz measured by impedance instrument. The theoretical analysis is conducted for the relationship between the revolving speed of the USM and thickness of stator ring, number of the travelling waves, PZT amplitude, frequency and the other parameters. The experiment result shows that the maximum revolving speed is 116 RPM and the maximum torque is 25 N mm, when the actuate voltage is 200 VAC.

  18. Experimental investigation on sandwich structure ring-type ultrasonic motor.

    PubMed

    Peng, Taijiang; Shi, Hongyan; Liang, Xiong; Luo, Feng; Wu, Xiaoyu

    2015-02-01

    This paper presents a manufacture method for a sandwich structure Ultrasonic Motor (USM) and experiment. Two pieces of rotor clamped on a stator, and a stainless steel disk-spring is bonded on the hollow rotor disk to provide the press by a nut assembled on the shaft. The stator is made of a double-side Printed-Circuit Board (PCB) which is sawed out the ring in the center and connected on the board with three legs. On each side of the ring surface, there are electrodes connected at the same position via through hole. The three layer drive circuit for sine, cosine, and ground signal is connected on the board through each leg. There are many piezoelectric components (PZT) bonded between two electrodes and fill soldering tin on each electrode. Then PZT is welded on PCB by reflow soldering. Finally, rub the gibbous soldering tin down to the position of PZT surface makes sure the surface contacts with rotor evenly. The welding process can also be completed by Surface Mounted Technology (SMT). A prototype motor is manufactured by this method. Two B03 model shapes of the stator are obtained by the finite element analysis and the optimal frequency of the motor is 56.375 kHz measured by impedance instrument. The theoretical analysis is conducted for the relationship between the revolving speed of the USM and thickness of stator ring, number of the travelling waves, PZT amplitude, frequency and the other parameters. The experiment result shows that the maximum revolving speed is 116 RPM and the maximum torque is 25 N mm, when the actuate voltage is 200 VAC. PMID:25213313

  19. The sandwich technique for repair of pectus carinatum and excavatum/carinatum complex

    PubMed Central

    Kim, Kyung Soo

    2016-01-01

    Background Simple external compression of pectus carinatum seems to have its limitations, particularly the repair of asymmetric pectus carinatum or excavatum/carinatum complex. We devised the sandwich technique (press-molding) to remodel the entire chest wall. The purpose of this study is to introduce the sandwich technique and appraise the early results. Methods Between January 2007 and January 2016, 523 consecutive patients with pectus carinatum and its variants were analyzed retrospectively. No patients were excluded during the study period. The sandwich 1 and 2 techniques using the internal and external pectus bars were for pectus carinatum repair. Modified techniques using the external string and the internal bar were to treat the lower costal flare (the flare-buster) and focal protuberances (the magic string) in pectus excavatum repair. Statistical analyses were carried out using paired and unpaired t-test or Wilcoxon signed rank tests. Results The sandwich repair with the external and internal bars was applied to 58 pectus carinatum patients: seven symmetric (12.1%), 14 asymmetric (24.1%), and 37 carinatum-excavatum complex (63.8%). After pectus excavatum repair, 426 patients had the flare-buster and 39 patients received the magic string. The sandwich 1 technique achieved near-complete resolution of carinatum in 52 patients (86.2%). The sandwich 2 technique accomplished almost symmetric configuration with no residual carinatum in all six cases. Conclusions The sandwich technique using the external and internal bars seems to be effective in treating asymmetric pectus carinatum and complex excavatum/carinatum deformities. The flare-buster and the magic string effectively relieve the costal flare and focal protuberances in pectus excavatum repair. PMID:27747176

  20. Density functional study of isoguanine tetrad and pentad sandwich complexes with alkali metal ions.

    PubMed

    Meyer, Michael; Steinke, Thomas; Sühnel, Jürgen

    2007-02-01

    Isoguanine tetraplexes and pentaplexes contain two or more stacked polyads with intercalating metal ions. We report here the results of a density functional study of sandwiched isoguanine tetrad and pentad complexes consisting of two polyads with Na(+), K(+) and Rb(+) ions at the B3LYP level. In comparison to single polyad metal ion complexes, there is a trend towards increased non-planarity of the polyads in the sandwich complexes. In general, the pentad sandwiches have relatively planar polyad structures, whereas the tetrad complexes contain highly non-planar polyad building blocks. As in other sandwich complexes and in metal ion complexes with single polyads, the metal ion-base interaction energy plays an essential role. In iG sandwich structures, this interaction energy is slightly larger than in the corresponding guanine sandwich complexes. Because the base-base interaction energy is even more increased in passing from guanine to isoguanine, the isoguanine sandwiches are thus far the only examples where the base-base interaction energy is larger than the base-metal ion interaction energy. Stacking interactions have been studied in smaller models consisting of two bases, retaining the geometry from the complete complex structures. From the data obtained at the B3LYP and BH&H levels and with Møller-Plesset perturbation theory, one can conclude that the B3LYP method overestimates the repulsion in stacked base dimers. For the complexes studied in this work, this is only of minor importance because the direct inter-tetrad or inter-pentad interaction is supplemented by a strong metal ion-base interaction. Using a microsolvation model, the metal ion preference K(+) approximately Rb(+) > Na(+) is found for tetrad complexes. On the other hand, for pentads the ordering is Rb(+) > K(+) > Na(+). In the latter case experimental data are available that agree with this prediction. PMID:17013632

  1. Buckling analysis of curved composite sandwich panels subjected to inplane loadings

    NASA Technical Reports Server (NTRS)

    Cruz, Juan R.

    1993-01-01

    Composite sandwich structures are being considered for primary structure in aircraft such as subsonic and high speed civil transports. The response of sandwich structures must be understood and predictable to use such structures effectively. Buckling is one of the most important response mechanisms of sandwich structures. A simple buckling analysis is derived for sandwich structures. This analysis is limited to flat, rectangular sandwich panels loaded by uniaxial compression (N(sub x)) and having simply supported edges. In most aerospace applications, however, the structure's geometry, boundary conditions, and loading are usually very complex. Thus, a general capability for analyzing the buckling behavior of sandwich structures is needed. The present paper describes and evaluates an improved buckling analysis for cylindrically curved composite sandwich panels. This analysis includes orthotropic facesheets and first-order transverse shearing effects. Both simple support and clamped boundary conditions are also included in the analysis. The panels can be subjected to linearly varying normal loads N(sub x) and N(sub y) in addition to a constant shear load N(sub xy). The analysis is based on the modified Donnell's equations for shallow shells. The governing equations are solved by direct application of Galerkin's method. The accuracy of the present analysis is verified by comparing results with those obtained from finite element analysis for a variety of geometries, loads, and boundary conditions. The limitations of the present analysis are investigated, in particular those related to the shallow shell assumptions in the governing equations. Finally, the computational efficiency of the present analysis is considered.

  2. Hypervelocity Impact Performance of Open Cell Foam Core Sandwich Panel Structures

    NASA Technical Reports Server (NTRS)

    Ryan, Shannon; Christiansen, Eric; Lear, Dana

    2009-01-01

    Metallic foams are a relatively new class of materials with low density and novel physical, mechanical, thermal, electrical and acoustic properties. Although incompletely characterized, they offer comparable mechanical performance to traditional spacecraft structural materials (i.e. honeycomb sandwich panels) without detrimental through-thickness channeling cells. There are two competing types of metallic foams: open cell and closed cell. Open cell foams are considered the more promising technology due to their lower weight and higher degree of homogeneity. Leading micrometeoroid and orbital debris shields (MMOD) incorporate thin plates separated by a void space (i.e. Whipple shield). Inclusion of intermediate fabric layers, or multiple bumper plates have led to significant performance enhancements, yet these shields require additional non-ballistic mass for installation (fasteners, supports, etc.) that can consume up to 35% of the total shield weight [1]. Structural panels, such as open cell foam core sandwich panels, that are also capable of providing sufficient MMOD protection, represent a significant potential for increased efficiency in hypervelocity impact shielding from a systems perspective through a reduction in required non-ballistic mass. In this paper, the results of an extensive impact test program on aluminum foam core sandwich panels are reported. The effect of pore density, and core thickness on shielding performance have been evaluated over impact velocities ranging from 2.2 - 9.3 km/s at various angles. A number of additional tests on alternate sandwich panel configurations of comparable-weight have also been performed, including aluminum honeycomb sandwich panels (see Figure 1), Nomex honeycomb core sandwich panels, and 3D aluminum honeycomb sandwich panels. A total of 70 hypervelocity impact tests are reported, from which an empirical ballistic limit equation (BLE) has been derived. The BLE is in the standard form suitable for implementation in

  3. Experimental investigation on the dynamic response of clamped corrugated sandwich plates subjected to underwater impulsive loadings

    NASA Astrophysics Data System (ADS)

    Huang, Wei; Zhang, Wei; Li, Dacheng; Hypervelocity Impact Research Center Team

    2015-06-01

    Corrugated sandwich plates are widely used in marine industry because such plates have high strength-to-weight ratios and blast resistance. The laboratory-scaled fluid-structure interaction experiments are performed to demonstrate the shock resistance of solid monolithic plates and corrugated sandwich plates by quantifying the permanent transverse deflection at mid-span of the plates as a function of impulsive loadings per areal mass. Sandwich structures with 6mm-thick and 10mm-thick 3003 aluminum corrugated core and 5A06 face sheets are compared with the 5A06 solid monolithic plates in this paper. The dynamic deformation of plates are captured with the the 3D digital speckle correlation method (DIC). The results affirm that sandwich structures show a 30% reduction in the maximum plate deflection compare with a monolithic plate of identical mass per unit area, and the peak value of deflection effectively reduced by increasing the thickness core. The failure modes of sandwich plates consists of core crushing, imprinting, stretch tearing of face sheets, bending and permanent deformation of entire structure with the increasing impulsive loads, and the failure mechanisms are analyzed with the postmortem panels and dynamic deflection history captured by cameras. National Natural Science Foundation of China (NO.: 11372088).

  4. Carbon sandwich preparation preserves quality of two-dimensional crystals for cryo-electron microscopy.

    PubMed

    Yang, Fan; Abe, Kazuhiro; Tani, Kazutoshi; Fujiyoshi, Yoshinori

    2013-12-01

    Electron crystallography is an important method for determining the structure of membrane proteins. In this paper, we show the impact of a carbon sandwich preparation on the preservation of crystalline sample quality, using characteristic examples of two-dimensional (2D) crystals from gastric H(+),K(+)-ATPase and their analyzed images. Compared with the ordinary single carbon support film preparation, the carbon sandwich preparation dramatically enhanced the resolution of images from flat sheet 2D crystals. As water evaporation is restricted in the carbon-sandwiched specimen, the improvement could be due to the strong protective effect of the retained water against drastic changes in the environment surrounding the specimen, such as dehydration and increased salt concentrations. This protective effect by the carbon sandwich technique helped to maintain the inherent and therefore best crystal conditions for analysis. Together with its strong compensation effect for the image shift due to beam-induced specimen charging, the carbon sandwich technique is a powerful method for preserving crystals of membrane proteins with larger hydrophilic regions, such as H(+),K(+)-ATPase, and thus constitutes an efficient and high-quality method for collecting data for the structural analysis of these types of membrane proteins by electron crystallography. PMID:23883606

  5. Compression After Impact Testing of Sandwich Structures Using the Four Point Bend Test

    NASA Technical Reports Server (NTRS)

    Nettles, Alan T.; Gregory, Elizabeth; Jackson, Justin; Kenworthy, Devon

    2008-01-01

    For many composite laminated structures, the design is driven by data obtained from Compression after Impact (CAI) testing. There currently is no standard for CAI testing of sandwich structures although there is one for solid laminates of a certain thickness and lay-up configuration. Most sandwich CAI testing has followed the basic technique of this standard where the loaded ends are precision machined and placed between two platens and compressed until failure. If little or no damage is present during the compression tests, the loaded ends may need to be potted to prevent end brooming. By putting a sandwich beam in a four point bend configuration, the region between the inner supports is put under a compressive load and a sandwich laminate with damage can be tested in this manner without the need for precision machining. Also, specimens with no damage can be taken to failure so direct comparisons between damaged and undamaged strength can be made. Data is presented that demonstrates the four point bend CAI test and is compared with end loaded compression tests of the same sandwich structure.

  6. Thermostructural Behavior of a Hypersonic Aircraft Sandwich Panel Subjected to Heating on One Side

    NASA Technical Reports Server (NTRS)

    Ko, William L.

    1997-01-01

    Thermostructural analysis was performed on a heated titanium honeycomb-core sandwich panel. The sandwich panel was supported at its four edges with spar-like substructures that acted as heat sinks, which are generally not considered in the classical analysis. One side of the panel was heated to high temperature to simulate aerodynamic heating during hypersonic flight. Two types of surface heating were considered: (1) flat-temperature profile, which ignores the effect of edge heat sinks, and (2) dome-shaped-temperature profile, which approximates the actual surface temperature distribution associated with the existence of edge heat sinks. The finite-element method was used to calculate the deformation field and thermal stress distributions in the face sheets and core of the sandwich panel. The detailed thermal stress distributions in the sandwich panel are presented, and critical stress regions are identified. The study shows how the magnitudes of those critical stresses and their locations change with different heating and edge conditions. This technical report presents comprehensive, three-dimensional graphical displays of thermal stress distributions in every part of a titanium honeycomb-core sandwich panel subjected to hypersonic heating on one side. The plots offer quick visualization of the structural response of the panel and are very useful for hot structures designers to identify the critical stress regions.

  7. A Study on Flexural Properties of Sandwich Structures with Fiber/Metal Laminate Face Sheets

    NASA Astrophysics Data System (ADS)

    Dariushi, S.; Sadighi, M.

    2013-10-01

    In this work, a new family of sandwich structures with fiber metal laminate (FML) faces is investigated. FMLs have benefits over both metal and fiber reinforced composites. To investigate the bending properties of sandwich beams with FML faces and compare with similar sandwich beams with fibrous composite faces, 6 groups of specimen with different layer arrangements were made and tested. Results show that FML faces have good resistance against transverse local loads and minimize stress concentration and local deformations of skin and core under the loading tip. In addition, FML faces have a good integrity even after plateau region of foam cores and prevent from catastrophic failures, which cannot be seen in fibrous composite faces. Also, FML faces are lighter than metal faces and have better connection with foam cores. Sandwich beams with FML faces have a larger elastic region because of simultaneous deformation of top and bottom faces and larger failure strain thanks to good durability of FMLs. A geometrical nonlinear classical theory is used to predict force-deflection behavior. In this model an explicit formula between symmetrical sandwich beams deflections and applied force which can be useful for designers, is derived. Good agreement is obtained between the analytical predictions and experimental results. Also, analytical results are compared with small deformation solution in a parametric study, and the effects of geometric parameters on difference between linear and nonlinear results are discussed.

  8. Evaluation of modal-based damage detection techniques for composite aircraft sandwich structures

    NASA Astrophysics Data System (ADS)

    Oliver, J. A.; Kosmatka, J. B.

    2005-05-01

    Composite sandwich structures are important as structural components in modern lightweight aircraft, but are susceptible to catastrophic failure without obvious forewarning. Internal damage, such as disbonding between skin and core, is detrimental to the structures' strength and integrity and thus must be detected before reaching critical levels. However, highly directional low density cores, such as Nomex honeycomb, make the task of damage detection and health monitoring difficult. One possible method for detecting damage in composite sandwich structures, which seems to have received very little research attention, is analysis of global modal parameters. This study will investigate the viability of modal analysis techniques for detecting skin-core disbonds in carbon fiber-Nomex honeycomb sandwich panels through laboratory testing. A series of carbon fiber prepreg and Nomex honeycomb sandwich panels-representative of structural components used in lightweight composite airframes-were fabricated by means of autoclave co-cure. All panels were of equal dimensions and two were made with predetermined sizes of disbonded areas, created by substituting areas of Teflon release film in place of epoxy film adhesive during the cure. A laser vibrometer was used to capture frequency response functions (FRF) of all panels, and then real and imaginary FRFs at different locations on each plate and operating shapes for each plate were compared. Preliminary results suggest that vibration-based techniques hold promise for damage detection of composite sandwich structures.

  9. Metal sandwich method to quick-freeze monolayer cultured cells for freeze-fracture.

    PubMed

    Fujimoto, T; Fujimoto, K

    1997-04-01

    We describe a simple quick-freezing method to obtain a large fractured plane of the plasma membrane from monolayer cultured cells. Cells were grown on thin gold foil, inverted on a thin layer of gelatin on thin copper foil, and frozen by a quick press between two gold-plated copper blocks precooled in liquid nitrogen. The frozen cell sandwich was mounted on the cold stage of a freeze-fracture device with the gold side up and was fractured by separating the sandwich with a cold fracture knife. When this technique was applied to confluent monolayer cells, large replicas of the E-face of the upper plasma membrane and the P-face of the lower plasma membrane were obtained. The present metal sandwich method is simple, does not require any expensive equipment, and provides a large fracture plane of the plasma membrane for subsequent histochemical manipulation. PMID:9111237

  10. Tests of graphite/polyimide sandwich panels in uniaxial edgewise compression

    NASA Technical Reports Server (NTRS)

    Camarda, C. J.

    1980-01-01

    The local and general buckling behavior of graphite/polyimide sandwich panels simply supported along all four edges and loaded in uniaxial edgewise compression were investigated. Material properties of sandwich panel constituents (adhesive and facings) were determined from flatwise tension and sandwich beam flexure tests. Buckling specimens were 30.5 by 33 cm, had quasi-isotropic, symmetric facings, and a glass/polyimide honeycomb core. Core thicknesses were varied and three panels of each thickness were tested at room temperature to investigate failure modes and corresponding buckling loads. Specimens 0.635 cm thick failed by overall buckling at loads close to the analytically predicted buckling load; all other panels failed by face wrinkling. Results of the wrinkling tests indicated that several buckling formulas were unconservative and therefore not suitable for design purposes; a recommended wrinkling equation is presented.

  11. Graphene oxide embedded sandwich nanostructures for enhanced Raman readout and their applications in pesticide monitoring

    NASA Astrophysics Data System (ADS)

    Zhang, Lulu; Jiang, Changlong; Zhang, Zhongping

    2013-04-01

    Analytical techniques based on surface-enhanced Raman scattering (SERS) suffer from a lack of reproducibility and reliability, thus hampering their practical applications. Herein, we have developed a SERS-active substrate based on a graphene oxide embedded sandwich nanostructure for ultrasensitive Raman signal readout. By using this novel Au@Ag NPs/GO/Au@Ag NPs sandwich nanostructure as a SERS substrate, the Raman signals of analytes were dramatically enhanced due to having plenty of hot spots on their surfaces and the unique structure of the graphene oxide sheets. These features make the sandwich nanostructured film an ideal SERS substrate to improve the sensitivity, reproducibility and reliability of the Raman readout. The sandwich nanostructure film can be applied to detect rhodamine-6G (R6G) with an enhancement factor (EF) of ~7.0 × 107 and the pesticide thiram in commercial grape juice with a detection limit of as low as 0.1 μM (0.03 ppm), which is much lower than the maximal residue limit (MRL) of 7 ppm in fruit prescribed by the U.S. Environmental Protection Agency (EPA). The GO embedded sandwich nanostructure also has the ability to selectively detect dithiocarbamate compounds over other types of agricultural chemical. Furthermore, spiked tests show that the sandwich nanostructure can be used to monitor thiram in natural lake water and commercial grape juice without further treatment. In addition, the GO enhanced Raman spectroscopic technique offers potential practical applications for the on-site monitoring and assessment of pesticide residues in agricultural products and environments.Analytical techniques based on surface-enhanced Raman scattering (SERS) suffer from a lack of reproducibility and reliability, thus hampering their practical applications. Herein, we have developed a SERS-active substrate based on a graphene oxide embedded sandwich nanostructure for ultrasensitive Raman signal readout. By using this novel Au@Ag NPs/GO/Au@Ag NPs sandwich

  12. Optimisation of Composite Sandwich Structures Subjected to Combined Torsion and Bending Stiffness Requirements

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Li, Gangyan; Wang, Chun H.

    2012-06-01

    This research is motivated by the rapidly increasing use of composite sandwich structures to reduce weight and improve energy efficiency in a wide range of industries such as automotive, aerospace and civil infrastructure. The paper presents a minimum-weight optimization method for sandwich structures to meet both torsion and bending rigidity requirements. This multiple inequality-constrained optimisation problem is formulated using the Lagrange multiplier method. Solving the resulting equations reveals the optimum solution that can satisfy both flexural and torsion stiffness requirements depend on the stiffness ratio relative to elastic modulus ratio. To illustrate the newly developed optimum design solutions, numerical examples are presented for sandwich structures made of either isotropic face skins or orthotropic composite face skins.

  13. Tunable and Sizable Band Gap of Single Layer Graphene Sandwiched between Hexagonal Boron Nitride

    NASA Astrophysics Data System (ADS)

    Zheng, Jiaxin; Qu, Heruge; Liu, Qihang; Qin, Rui; Zhou, Jing; Yu, Dapeng; Gao, Zhengxiang; Lu, Jing; Luo, Guangfu; Nagase, Shigeru; Mei, Wai-Ning

    2012-02-01

    It is a big challenge to open a tunable and sizable band gap of single layer graphene without big loss in structural integrity and carrier mobility. By using density functional theory calculations, we show that the band gap of single layer graphene can be opened to 0.16 (without electrical field) and 0.34 eV (with a strong electrical field) when sandwiched between two hexagonal boron nitride single layers in a proper way. The zero-field band gaps are increased by about 50% when many-body effects are included. Ab initio quantum transport simulation of a dual-gated FET out of such a sandwich structure further confirms an electrical field-enhanced transport gap. The tunable and sizeable band gap and structural integrity render this sandwich structure a promising candidate for high-performance single layer graphene field effect transistors.

  14. A Higher-Order Bending Theory for Laminated Composite and Sandwich Beams

    NASA Technical Reports Server (NTRS)

    Cook, Geoffrey M.

    1997-01-01

    A higher-order bending theory is derived for laminated composite and sandwich beams. This is accomplished by assuming a special form for the axial and transverse displacement expansions. An independent expansion is also assumed for the transverse normal stress. Appropriate shear correction factors based on energy considerations are used to adjust the shear stiffness. A set of transverse normal correction factors is introduced, leading to significant improvements in the transverse normal strain and stress for laminated composite and sandwich beams. A closed-form solution to the cylindrical elasticity solutions for a wide range of beam aspect ratios and commonly used material systems. Accurate shear stresses for a wide range of laminates, including the challenging unsymmetric composite and sandwich laminates, are obtained using an original corrected integration scheme. For application of the theory to a wider range of problems, guidelines for finite element approximations are presented.

  15. Novel sandwich structure adsorptive membranes for removal of 4-nitrotoluene from water.

    PubMed

    Guo, Yuexin; Jia, Zhiqian

    2016-11-01

    Novel sandwich PES-SPES/PS-PDVB/PTFE adsorptive membranes were prepared by a filtration/immersion precipitation method and employed for the removal of 4-nitrotoluene from water. The static adsorption thermodynamics, kinetics, dynamic adsorption/desorption and membrane reusability were investigated. The results showed that the Freundlich model describes the adsorption isotherm satisfactorily. With increased PS-PDVB content, the maximum static adsorption capacity, partition coefficient, apparent adsorption rate constant, and dynamic adsorption capacity all significantly increased. The sandwich membranes showed much higher removal efficiency and adsorption capacity than those of mixed matrix membranes. With respect to dynamics adsorption/desorption, the sandwich membranes exhibited excellent reusability, with a removal efficiency greater than 95% even after five recycles. PMID:27322899

  16. Simultaneous determination of iron (II) and ascorbic acid in pharmaceuticas based on flow sandwich technique.

    PubMed

    Vakh, Christina; Freze, Elena; Pochivalov, Alexsey; Evdokimova, Ekaterina; Kamencev, Mihail; Moskvin, Leonid; Bulatov, Andrey

    2015-01-01

    The simple and easy performed flow system based on sandwich technique has been developed for the simultaneous separate determination of iron (II) and ascorbic acid in pharmaceuticals. The implementation of sandwich technique assumed the injection of sample solution between two selective reagents and allowed the carrying out in reaction coil two chemical reactions simultaneously: iron (II) with 1,10-phenanthroline and ascorbic acid with sodium 2,6-dichlorophenolindophenol. For achieving of excellent repeatability and considerable reagent saving the various parameters such as flow rate, sample and reagent volumes, reaction coil length were also optimized. The limits of detection (LODs) obtained by using the developed flow sandwich-type approach were 0.2 mg L(-1) for iron (II) and 0.7 mg L(-1) for ascorbic acid. The suggested approach was validated according to the following parameters: linearity and sensitivity, precision, recoveries and accuracy. The sampling frequency was 41 h(-1). PMID:25862995

  17. Graphene oxide embedded sandwich nanostructures for enhanced Raman readout and their applications in pesticide monitoring.

    PubMed

    Zhang, Lulu; Jiang, Changlong; Zhang, Zhongping

    2013-05-01

    Analytical techniques based on surface-enhanced Raman scattering (SERS) suffer from a lack of reproducibility and reliability, thus hampering their practical applications. Herein, we have developed a SERS-active substrate based on a graphene oxide embedded sandwich nanostructure for ultrasensitive Raman signal readout. By using this novel Au@Ag NPs/GO/Au@Ag NPs sandwich nanostructure as a SERS substrate, the Raman signals of analytes were dramatically enhanced due to having plenty of hot spots on their surfaces and the unique structure of the graphene oxide sheets. These features make the sandwich nanostructured film an ideal SERS substrate to improve the sensitivity, reproducibility and reliability of the Raman readout. The sandwich nanostructure film can be applied to detect rhodamine-6G (R6G) with an enhancement factor (EF) of ∼7.0 × 10(7) and the pesticide thiram in commercial grape juice with a detection limit of as low as 0.1 μM (0.03 ppm), which is much lower than the maximal residue limit (MRL) of 7 ppm in fruit prescribed by the U.S. Environmental Protection Agency (EPA). The GO embedded sandwich nanostructure also has the ability to selectively detect dithiocarbamate compounds over other types of agricultural chemical. Furthermore, spiked tests show that the sandwich nanostructure can be used to monitor thiram in natural lake water and commercial grape juice without further treatment. In addition, the GO enhanced Raman spectroscopic technique offers potential practical applications for the on-site monitoring and assessment of pesticide residues in agricultural products and environments.

  18. Low-Velocity Impact Response of Sandwich Beams with Functionally Graded Core

    NASA Technical Reports Server (NTRS)

    Apetre, N. A.; Sankar, B. V.; Ambur, D. R.

    2006-01-01

    The problem of low-speed impact of a one-dimensional sandwich panel by a rigid cylindrical projectile is considered. The core of the sandwich panel is functionally graded such that the density, and hence its stiffness, vary through the thickness. The problem is a combination of static contact problem and dynamic response of the sandwich panel obtained via a simple nonlinear spring-mass model (quasi-static approximation). The variation of core Young's modulus is represented by a polynomial in the thickness coordinate, but the Poisson's ratio is kept constant. The two-dimensional elasticity equations for the plane sandwich structure are solved using a combination of Fourier series and Galerkin method. The contact problem is solved using the assumed contact stress distribution method. For the impact problem we used a simple dynamic model based on quasi-static behavior of the panel - the sandwich beam was modeled as a combination of two springs, a linear spring to account for the global deflection and a nonlinear spring to represent the local indentation effects. Results indicate that the contact stiffness of thc beam with graded core Increases causing the contact stresses and other stress components in the vicinity of contact to increase. However, the values of maximum strains corresponding to the maximum impact load arc reduced considerably due to grading of thc core properties. For a better comparison, the thickness of the functionally graded cores was chosen such that the flexural stiffness was equal to that of a beam with homogeneous core. The results indicate that functionally graded cores can be used effectively to mitigate or completely prevent impact damage in sandwich composites.

  19. Systems, Apparatuses, and Methods for Using Durable Adhesively Bonded Joints for Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Smeltzer, III, Stanley S. (Inventor); Lundgren, Eric C. (Inventor)

    2014-01-01

    Systems, methods, and apparatus for increasing durability of adhesively bonded joints in a sandwich structure. Such systems, methods, and apparatus includes an first face sheet and an second face sheet as well as an insert structure, the insert structure having a first insert face sheet, a second insert face sheet, and an insert core material. In addition, sandwich core material is arranged between the first face sheet and the second face sheet. A primary bondline may be coupled to the face sheet(s) and the splice. Further, systems, methods, and apparatus of the present disclosure advantageously reduce the load, provide a redundant path, reduce structural fatigue, and/or increase fatigue life.

  20. Analyses for Debonding of Stitched Composite Sandwich Structures Using Improved Constitutive Models

    NASA Technical Reports Server (NTRS)

    Glaessgen, E. H.; Sleight, D. W.; Krishnamurthy, T.; Raju, I. S.

    2001-01-01

    A fracture mechanics analysis based on strain energy release rates is used to study the effect of stitching in bonded sandwich beam configurations. Finite elements are used to model the configurations. The stitches were modeled as discrete nonlinear spring elements with a compliance determined by experiment. The constitutive models were developed using the results of flatwise tension tests from sandwich material rather than monolithic material. The analyses show that increasing stitch stiffness, stitch density and debond length decrease strain energy release rates for a fixed applied load.

  1. Microstructure of the combustion zone: Thin-binder AP-polymer sandwiches

    NASA Technical Reports Server (NTRS)

    Price, E. W.; Panyam, R. R.; Sigman, R. K.

    1980-01-01

    Experimental results are summarized for systematic quench-burning tests on ammonium perchlorate-HC binder sandwiches with binder thicknesses in the range 10 - 150 microns. Tests included three binders (polysulfide, polybutadiene-acrylonitrile, and hydroxy terminated polybutadiene), and pressures from 1.4 to 14 MPa. In addition, deflagration limits were determined in terms of binder thickness and pressure. Results are discussed in terms of a qualitative theory of sandwich burning consolidated from various sources. Some aspects of the observed results are explained only speculatively.

  2. On core compressibility of sandwich composite panels subjected to intense underwater shock loads

    NASA Astrophysics Data System (ADS)

    Ghoshal, Ritwik; Mitra, Nilanjan

    2014-01-01

    Novel analytical models have been proposed in this study which extends current available fluid-structure interaction (FSI) theories for explosion induced shock loading on monolithic and laminated composite plates to sandwich composite panels, featuring core compression. The proposed models have been asymptotically validated against other FSI existing theories in low pressure range. A qualitative comparative analysis of the proposed models has been made with other existing FSI theories from the viewpoint of energy conservation. Core compression as predicted by the proposed models can be utilized for more economical, robust design of blast resistant sandwich composite structures.

  3. A {3,2}-Order Bending Theory for Laminated Composite and Sandwich Beams

    NASA Technical Reports Server (NTRS)

    Cook, Geoffrey M.; Tessler, Alexander

    1998-01-01

    A higher-order bending theory is derived for laminated composite and sandwich beams thus extending the recent {1,2}-order theory to include third-order axial effect without introducing additional kinematic variables. The present theory is of order {3,2} and includes both transverse shear and transverse normal deformations. A closed-form solution to the cylindrical bending problem is derived and compared with the corresponding exact elasticity solution. The numerical comparisons are focused on the most challenging material systems and beam aspect ratios which include moderate-to-thick unsymmetric composite and sandwich laminates. Advantages and limitations of the theory are discussed.

  4. Equivalent material modelling of sandwich beams, evanescent solutions and damping investigations

    NASA Astrophysics Data System (ADS)

    de Rijk, Sophie; Nijman, Eugene

    2016-11-01

    A novel method for representing the transverse vibrations of sandwich beams as equivalent Timoshenko beams is developed. Special attention is given to damping modelling together with the evanescent parts of the solutions to assert applicability of the approach to any boundary conditions. Shear stiffness is evaluated based on current knowledge. The latter is then used to update the reference theory for vibrations in sandwich beams. Analytical case studies are presented to show the performance and limitations of the method and compared with experimental data.

  5. FaceSheet Push-off Tests to Determine Composite Sandwich Toughness at Cryogenic Temperatures

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.; Herring, Helen M.

    2001-01-01

    A new novel test method, associated analysis, and experimental procedures are developed to investigate the toughness of the facesheet-to-core interface of a sandwich material at cryogenic temperatures. The test method is designed to simulate the failure mode associated with facesheet debonding from high levels of gas pressure in the sandwich core. The effects of specimen orientation are considered, and the results of toughness measurements are presented. Comparisons are made between room and liquid nitrogen (-196 C) test temperatures. It was determined that the test method is insensitive to specimen facesheet orientation and strain energy release rate increases with a decrease in the test temperature.

  6. Cherenkov radiation of a Josephson vortex moving in a sandwich embedded in a dielectric medium

    SciTech Connect

    Malishevskii, A. S. Silin, V. P.; Uryupin, S. A.; Uspenskii, S. G.

    2008-08-15

    A motion of a Josephson vortex in a long sandwich embedded in a dielectric medium is described. If the velocity of the vortex is greater than the velocity of light in the dielectric, terahertz-band Cherenkov radiation is generated and emitted from the lateral surface of the sandwich. The radiation loss power is determined. In the case when radiation loss is compensated for by the energy gain due to transport current, a relation between the current and the velocity of the vortex is obtained.

  7. Using Conducting Wire at A-Sandwich Junctions to Improve the Transmission Performance of Radomes

    NASA Astrophysics Data System (ADS)

    Inasawa, Yoshio; Nishimura, Toshio; Tsuruta, Jun; Miyashita, Hiroaki; Konishi, Yoshihiko

    We present design procedures for using conducting wires in A-sandwich junctions to achieve high transmission performance; benchtest results validate the procedures. The scattering characteristics of the junction are obtained by solving the electric field integral equation of volumetric equivalent currents. The transmission performance is evaluated by subtracting the scattered fields of the same-sized A-sandwich panel in order to offset the effect of edge diffraction. Optimum wire width is determined by examining transmission performance with different arrangements. The designed junction achieves high transmission performance. The measured scattering characteristics of a bench model demonstrate the validity of the presented method.

  8. Sandwich consumption by adults in the U.S., What We Eat in America, NHANES 2009-2012

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although sandwiches are a staple of the American diet, little is known about their consumption and their contributions to dietary intakes of energy, nutrients, and food components. In this report, the definition of “sandwich” includes not only sandwiches represented in the dietary data by a single ...

  9. Fabrication of a 2014Al-SiC/2014Al Sandwich Structure Composite with Good Tensile Strength and Ductility

    NASA Astrophysics Data System (ADS)

    Zhu, Xian; Zhao, Yu-Guang; Wang, Hui-Yuan; Wang, Zhi-Guo; Wu, Min; Pei, Chang-hao; Chen, Chao; Jiang, Qi-Chuan

    2016-09-01

    A sandwich structure laminate composed of a ductile 2014Al inter-layer and two nanoscale SiC reinforced 2014Al (SiC/2014Al) composite outer layers was successfully fabricated through the combination of powder metallurgy and hot rolling. The ductile 2014Al inter-layer effectively improved the processability of the sandwiched laminates. Tensile test revealed that the yield strength and ultimate tensile strength of the sandwiched laminate were 287 and 470 MPa, respectively, compared with 235 and 425 MPa for monolithic 2014Al. The good performance of the sandwiched laminate results from the strong bonding between the SiC/2014Al composites layer and the ductile 2014Al layer. Thus, the sandwich structure with a composite surface and ductile core is effective for increasing the strength and toughness of composite laminates.

  10. The Association between Membership in the Sandwich Generation and Health Behaviors: A Longitudinal Study

    ERIC Educational Resources Information Center

    Chassin, Laurie; Macy, Jon T.; Seo, Dong-Chul; Presson, Clark C.; Sherman, Steven J.

    2010-01-01

    The current study examined the association between membership in the sandwich generation, defined as providing care to both children and parents or in-laws, and five health behaviors: checking the food label for health value when buying foods, using a seat belt, choosing foods based on health value, exercising regularly, and cigarette smoking.…

  11. Morphing nacelle inlet lip with pneumatic actuators and a flexible nano composite sandwich panel

    NASA Astrophysics Data System (ADS)

    Gulsine Ozdemir, Nazli; Scarpa, Fabrizio; Craciun, Monica; Remillat, Chrystel; Lira, Cristian; Jagessur, Yogesh; Da Rocha-Schmidt, Luiz

    2015-12-01

    We present a hybrid pneumatic/flexible sandwich structure with thermoplastic (TP) nanocomposite skins to enable the morphing of a nacelle inlet lip. The design consists of pneumatic inflatables as actuators and a flexible sandwich panel that morphs under variable pressure combinations to adapt different flight conditions and save fuel. The sandwich panel forms the outer layer of the nacelle inlet lip. It is lightweight, compliant and impact resistant with no discontinuities, and consists of graphene-doped thermoplastic polyurethane (G/TPU) skins that are supported by an aluminium Flex-core honeycomb in the middle, with near zero in-plane Poisson’s ratio behaviour. A test rig for a reduced-scale demonstrator was designed and built to test the prototype of morphing nacelle with custom-made pneumatic actuators. The output force and the deflections of the experimental demonstrator are verified with the internal pressures of the actuators varying from 0 to 0.41 MPa. The results show the feasibility and promise of the hybrid inflatable/nanocomposite sandwich panel for morphing nacelle airframes.

  12. ACTIV: Sandwich Detector Activity from In-Pile Slowing-Down Spectra Experiment

    SciTech Connect

    2013-08-01

    ACTIV calculates the activities of a sandwich detector, to be used for in-pile measurements in slowing-down spectra below a few keV. The effect of scattering with energy degradation in the filter and in the detectors has been included to a first approximation.

  13. Phonons transmission by thin films sandwiched between two similar fcc structures

    NASA Astrophysics Data System (ADS)

    Belkacemi, Ghania; Bourahla, Boualem

    2015-09-01

    An analytical and numerical formalism are developed to study the influence of the sandwiched atomic films on the vibration properties and phonon transmission modes in fcc waveguides. The model system consists of two identical semi-infinite fcc leads joined by ultrathin atomic films in between. The matching technique is applied to calculate the local Green's functions for the irreducible set of sites that constitute the inhomogeneous domain. Numerical results are presented for the reflection/transmission, total phonon transmittance and localized vibration states in considered fcc lattices. The results show that vibrational properties of the sandwich materials are strongly dependent on the scattering frequency, the thickness of the insured films, incidence angles and elastic boundary conditions. We note that some of the fluctuations, observed in the vibration spectra, are related to Fano resonances, they are due to the coherent coupling between travelling phonons and the localized vibration modes in the neighborhood of the nanojunction domains. The number of localized modes which interact with the propagating modes of the continuum is proportional to the number of the sandwiched Slabs in the interfacial zone. The results give also the effect of the sandwiched ultrathin films on elastic waves propagation by atomic interfaces in fcc lattices.

  14. Experimental investigation of graphite/polyimide sandwich panels in edgewise compression. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Camarda, C. J.

    1980-01-01

    The local and general buckling of graphite/polyimide sandwich panels simply supported along all four edges and loaded in uniaxial edgewise compression is investigated. Material properties of sandwich panel constituents (adhesive and facings) were determined from flatwise tension and sandwich beam flexure tests. An adhesive bond study resulted in the selection of a suitable cure cycle for FM 34 polyimide film adhesive and, a bonding technique using a liquid cell edge version of that adhesive resulted in considerable mass savings. Tensile and compressive material properties of the facings, quasiisotropic, symmetric, laminates (0, +45,90,-45)s of Celion/PMR-15, were determined at 116, R.T., and 589 K (-250, R.T., and 600 F) usng the sandwich beam flexure test method. Results indicate the Gr/PI is a usable structural material for short term use at temperatures as high as 589 K (600 F). Buckling specimens were 1006.5 sq cm. 156 sq in., had quasiisotropic symmetric facings (0, + or - 45,90)s and a glass/polyimide honeycomb core (HRH-327-3/8-4).

  15. [Sb4Au4Sb4](2-): A designer all-metal aromatic sandwich.

    PubMed

    Tian, Wen-Juan; Guo, Jin-Chang; Li, Da-Zhi; You, Xue-Rui; Wang, Ying-Jin; Sun, Zhong-Ming; Zhai, Hua-Jin

    2016-07-28

    We report on the computational design of an all-metal aromatic sandwich, [Sb4Au4Sb4](2-). The triple-layered, square-prismatic sandwich complex is the global minimum of the system from Coalescence Kick and Minima Hopping structural searches. Following a standard, qualitative chemical bonding analysis via canonical molecular orbitals, the sandwich complex can be formally described as [Sb4](+)[Au4](4-)[Sb4](+), showing ionic bonding characters with electron transfers in between the Sb4/Au4/Sb4 layers. For an in-depth understanding of the system, one needs to go beyond the above picture. Significant Sb → Au donation and Sb ← Au back-donation occur, redistributing electrons from the Sb4/Au4/Sb4 layers to the interlayer Sb-Au-Sb edges, which effectively lead to four Sb-Au-Sb three-center two-electron bonds. The complex is a system with 30 valence electrons, excluding the Sb 5s and Au 5d lone-pairs. The two [Sb4](+) ligands constitute an unusual three-fold (π and σ) aromatic system with all 22 electrons being delocalized. An energy gap of ∼1.6 eV is predicted for this all-metal sandwich. The complex is a rare example for rational design of cluster compounds and invites forth-coming synthetic efforts. PMID:27475362

  16. Half-sandwich cycloruthenated complexes from aryloxazolines: synthesis, structures, and catalytic activities.

    PubMed

    Jia, Wei-Guo; Zhang, Tai; Xie, Dong; Xu, Qiu-Tong; Ling, Shuo; Zhang, Qing

    2016-09-28

    Seven half-sandwich cycloruthenated complexes [Ru(p-cymene)LCl] (2a-2g) (L = 2-phenyl-2-oxazoline (2a), 2-p-tolyl-4,5-dihydrooxazole (2b), 4,4-dimethyl-2-phenyl-2-oxazoline (2c), 2-(4-chlorophenyl)-4,5-dihydrooxazole (2d), 2-(4-bromophenyl)-4,5-dihydrooxazole (2e), 2-(4-fluorophenyl)-4,5-dihydrooxazole (2f) and 2-(4-nitrophenyl)-4,5-dihydrooxazole (2g)) were synthesized and characterized. All half-sandwich cycloruthenated complexes were fully characterized by (1)H and (13)C NMR spectra, elemental analyses and infrared spectroscopy. The molecular structures of 2a, 2d and 2e were confirmed by single-crystal X-ray diffraction methods. These half-sandwich cycloruthenated complexes were employed in nitroarene reduction using sodium borohydride (NaBH4) as a reducing agent in ethanol at room temperature. The catalytic results indicate that half-sandwich cycloruthenated complexes show promising catalytic activity in nitroarene reduction with a broad substrate and varied functional group compatibility. PMID:27534600

  17. Extremely low-frequency Lamb wave band gaps in a sandwich phononic crystal thin plate

    NASA Astrophysics Data System (ADS)

    Shen, Li; Wu, Jiu Hui; Liu, Zhangyi; Fu, Gang

    2015-11-01

    In this paper, a kind of sandwich phononic crystal (PC) plate with silicon rubber scatterers embedded in polymethyl methacrylate (PMMA) matrix is proposed to demonstrate its low-frequency Lamb wave band gap (BG) characteristics. The dispersion relationship and the displacement vector fields of the basic slab modes and the locally resonant modes are investigated to show the BG formation mechanism. The anti-symmetric Lamb wave BG is further studied due to its important function in reducing vibration. The analysis on the BG characteristics of the PC through changing their geometrical parameters is performed. By optimizing the structure, a sandwich PC plate with a thickness of only 3 mm and a lower boundary (as low as 23.9 Hz) of the first anti-symmetric BG is designed. Finally, sound insulation experiment on a sandwich PC plate with the thickness of only 2.5 mm is conducted, showing satisfactory noise reduction effect in the frequency range of the anti-symmetric Lamb BG. Therefore, this kind of sandwich PC plate has potential applications in controlling vibration and noise in low-frequency ranges.

  18. An analytical and experimental investigation of sandwich composites subjected to low-velocity impact

    NASA Astrophysics Data System (ADS)

    Anderson, Todd Alan

    1999-12-01

    This study involves an experimental and analytical investigation of low-velocity impact phenomenon in sandwich composite structures. The analytical solution of a three-dimensional finite-geometry multi-layer specially orthotropic panel subjected to static and transient transverse loading cases is presented. The governing equations of the static and dynamic formulations are derived from Reissner's functional and solved by enforcing the continuity of traction and displacement components between adjacent layers. For the dynamic loading case, the governing equations are solved by applying Fourier or Laplace transformation in time. Additionally, the static solution is extended to solve the contact problem between the sandwich laminate and a rigid sphere. An iterative method is employed to determine the sphere's unknown contact area and pressure distribution. A failure criterion is then applied to the sandwich laminate's stress and strain field to predict impact damage. The analytical accuracy of the present study is verified through comparisons with finite element models, other analyses, and through experimentation. Low-velocity impact tests were conducted to characterize the type and extent of the damage observed in a variety of sandwich configurations with graphite/epoxy face sheets and foam or honeycomb cores. Correlation of the residual indentation and cross-sectional views of the impacted specimens provides a criterion for the extent of damage. Quasi-static indentation tests are also performed and show excellent agreement when compared with the analytical predictions. Finally, piezoelectric polyvinylidene fluoride (PVF2) film sensors are found to be effective in detecting low-velocity impact.

  19. STS-43 Pilot Baker eats a sandwich on OV-104's forward flight deck

    NASA Technical Reports Server (NTRS)

    1991-01-01

    STS-43 Pilot Michael A. Baker, seated at the forward flight deck pilots station controls, eats a freefloating peanut butter and jelly sandwich while holding a carrot. Surrounding Baker on Atlantis', Orbiter Vehicle (OV) 104's, flight deck are procedural checklists, control panels, and windows. A lemonade drink bag is velcroed to overhead panel O9.

  20. Job Burnout and Couple Burnout in Dual-Earner Couples in the Sandwiched Generation

    ERIC Educational Resources Information Center

    Pines, Ayala Malach; Neal, Margaret B.; Hammer, Leslie B.; Icekson, Tamar

    2011-01-01

    We use existential theory as a framework to explore the levels of and relationship between job and couple burnout reported by dual-earner couples in the "sandwich generation" (i.e., couples caring both for children and aging parents) in a sample of such couples in Israel and the United States. This comparison enables an examination of the…

  1. Comparison of Theory with Experimental Data For a Partially Covered Double-Sandwich Cantilever Beam

    NASA Technical Reports Server (NTRS)

    Chen, Qinghua; Levy, Cesar

    1998-01-01

    In this paper, vibration characteristics of a partially covered, double-sandwich cantilever beam are evaluated experimentally and compared to the theoretical results of Levy and Chen for partially covered beams with and without end mass. The results obtained indicate that the theoretical models serve very well in providing the frequency factors and loss factors for the system being investigated.

  2. Efficiency of a Sandwiched Thermoelectric Material with a Graded Interlayer and Temperature-Dependent Properties

    NASA Astrophysics Data System (ADS)

    Wallace, T. T.; Jin, Z.-H.; Su, J.

    2016-04-01

    This paper investigates the energy conversion efficiency for a sandwiched thermoelectric (TE) material with a graded interlayer and temperature-dependent properties. The graded interlayer can be modeled as a composite of the two homogeneous end material members to achieve continuously varying composition and properties, thus eliminating the electrical contact resistance at the interfaces of segmented TE materials. The temperature distribution and efficiency are obtained by a semianalytical recurrence relation and a simple iteration technique. In the numerical examples, we consider a sandwiched TE element consisting of nanostructured Bi2Te3 at the cold-end side, nanostructured PbTe at the hot-end side, and a graded interlayer of Bi2Te3-PbTe composite. The numerical results show that the peak efficiency of the sandwiched TE material with no contact resistance is higher than that of segmented Bi2Te3/PbTe with contact resistance at the sharp interface between Bi2Te3 and PbTe. The peak efficiency of the sandwiched material is also influenced by the location of and gradation profile in the graded interlayer. Finally, it is found that temperature dependence of properties decreases the efficiencies of Bi2Te3 and PbTe.

  3. [Sb4Au4Sb4]2-: A designer all-metal aromatic sandwich

    NASA Astrophysics Data System (ADS)

    Tian, Wen-Juan; Guo, Jin-Chang; Li, Da-Zhi; You, Xue-Rui; Wang, Ying-Jin; Sun, Zhong-Ming; Zhai, Hua-Jin

    2016-07-01

    We report on the computational design of an all-metal aromatic sandwich, [Sb4Au4Sb4]2-. The triple-layered, square-prismatic sandwich complex is the global minimum of the system from Coalescence Kick and Minima Hopping structural searches. Following a standard, qualitative chemical bonding analysis via canonical molecular orbitals, the sandwich complex can be formally described as [Sb4]+[Au4]4-[Sb4]+, showing ionic bonding characters with electron transfers in between the Sb4/Au4/Sb4 layers. For an in-depth understanding of the system, one needs to go beyond the above picture. Significant Sb → Au donation and Sb ← Au back-donation occur, redistributing electrons from the Sb4/Au4/Sb4 layers to the interlayer Sb-Au-Sb edges, which effectively lead to four Sb-Au-Sb three-center two-electron bonds. The complex is a system with 30 valence electrons, excluding the Sb 5s and Au 5d lone-pairs. The two [Sb4]+ ligands constitute an unusual three-fold (π and σ) aromatic system with all 22 electrons being delocalized. An energy gap of ˜1.6 eV is predicted for this all-metal sandwich. The complex is a rare example for rational design of cluster compounds and invites forth-coming synthetic efforts.

  4. Comparison of Retention Rates Using Traditional, Drill Sandwich, and Incremental Rehearsal Flash Card Methods.

    ERIC Educational Resources Information Center

    MacQuarrie, Lara L.; Tucker, James A.; Burns, Matthew K.; Hartman, Brian

    2002-01-01

    Research has demonstrated increased retention from drill, but the data regarding drill format are inconsistent. Two commonly used models, Drill Sandwich (DS) and Incremental Rehearsal (IR), were compared to each other and to a traditional flashcard method. The IR model consistently led to significantly more words retained than the traditional or…

  5. Damage Detection and Impact Testing on Laminated and Sandwich Composite Panels

    NASA Technical Reports Server (NTRS)

    Hughes, Derke R.; Craft, William J.; Schulz, Mark J.; Naser, Ahmad S.; Martin, William N.

    1998-01-01

    This research investigates health monitoring of sandwich shell composites to determine if the Transmittance Functions (TF) are effective in determining the present of damage. The health monitoring test was conducted on the sandwich plates before and after low velocity impacts using the health monitoring technique given in TFs are a NDE (Nondestructive Evaluation) technique that utilizes the ratios of cross-spectrums to auto-spectrums between two response points on the sandwich composites. The test for transmittance was conducted on the same density foam core throughout the experiment. The test specimens were 17.8 cm by 25.4 cm in dimension. The external sheets (face sheets) were created from graphite/epoxy laminate with dimension of 1.58 mm thick. The polymethacrylide (Rohacell) foam core was 12.7 mm thick. These samples experienced a transformation in the TF that was considered the low velocity impact damage. The low velocity damage was observed in the TFs for the sandwich composites.

  6. Library Services to the Sandwich Generation and Serial Caregivers. ASCLA Changing Horizons Series.

    ERIC Educational Resources Information Center

    Walling, Linda Lucas, Comp.

    This book discusses library services to the "sandwich generation" (i.e., people in late middle age who find themselves caring for their elderly, impaired parents at the same time that their adult children are returning home for economic or other reasons) and "serial caregivers" (i.e., people who, at various periods throughout their lifetimes, find…

  7. Unique Sandwiched Carbon Sheets@Ni-Mn Nanoparticles for Enhanced Oxygen Evolution Reaction.

    PubMed

    Zhang, Yan; Zhang, Huijuan; Yang, Jiao; Bai, Yuanjuan; Qiu, Huajun; Wang, Yu

    2016-05-11

    A unique sandwich-like architecture, where Ni-Mn nanoparticles are enveloped in coupled carbon sheets (CS@Ni-Mn), has been successfully fabricated. In the synthesis process, a great quantity of uniform NiMnO3 nanosheets generated by a universal hydrothermal method acts as precursors and templates and the cheap, environmentally friendly and recyclable glucose functions as a green carbon source. Via subsequent hydrothermal reaction and thermal annealing, sandwiched nanocomposites with Ni-Mn nanoparticles embedded inside and carbon sheets encapsulating outside can be massively prepared. The novel sandwich-like CS@Ni-Mn possesses numerous advantages, such as an intrinsic porous feature, large specific surface area, and enhanced electronic conductivity. Moreover, as a promising NiMn-based oxygen evolution reaction (OER) catalyst, the special sandwiched nanostructure demonstrates improved electrochemical properties in 1 M KOH, including a low overpotential of about 250 mV, a modest Tafel slope of 40 mV dec(-1), excellent stability over 2000 cycles, and durability for 40 h. PMID:27101350

  8. A high-throughput, precipitating colorimetric sandwich ELISA microarray for shiga toxins

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Shiga toxins 1 and 2 (Stx1 and Stx2) from Shiga toxin-producing E. coli (STEC) bacteria were simultaneously detected with a newly developed, high-throughput antibody microarray platform. The proteinaceous toxins were immobilized and sandwiched between biorecognition elements (monoclonal antibodies)...

  9. Optimum stacking sequence design of composite sandwich panel using genetic algorithms

    NASA Astrophysics Data System (ADS)

    Bir, Amarpreet Singh

    Composite sandwich structures recently gained preference for various structural components over conventional metals and simple composite laminates in the aerospace industries. For most widely used composite sandwich structures, the optimization problems only requires the determination of the best stacking sequence and the number of laminae with different fiber orientations. Genetic algorithm optimization technique based on Darwin's theory of survival of the fittest and evolution is most suitable for solving such optimization problems. The present research work focuses on the stacking sequence optimization of composite sandwich panels with laminated face-sheets for both critical buckling load maximization and thickness minimization problems, subjected to bi-axial compressive loading. In the previous studies, only balanced and even-numbered simple composite laminate panels have been investigated ignoring the effects of bending-twisting coupling terms. The current work broadens the application of genetic algorithms to more complex composite sandwich panels with balanced, unbalanced, even and odd-numbered face-sheet laminates including the effects of bending-twisting coupling terms.

  10. Ferrocene analogues of sandwich B12·Cr·B12: a theoretical study.

    PubMed

    Yuan, Yuan; Cheng, Longjiu

    2013-01-14

    The bowl B(12) cluster was previously reported to be analogous to benzene and predicted to be one of the best candidates to be new inorganic ligands. The structural stability and electronic properties of a new sandwich compound Cr(B(12))(2) (D(3d)) have been investigated by using density functional theory. It is found that the sandwich Cr(B(12))(2) (D(3d)) is a stable complex with large binding energy (-5.93 eV) and HOMO-LUMO gap (2.37 eV), as well as Fe(C(5)H(5))(2) and Cr(C(6)H(6))(2), following the 18-electron principle. The detailed molecular orbitals and aromaticity analyses indicate that the sandwich compound Cr(B(12))(2) (D(3d)) is electronically very stable. The natural bond orbital analysis suggests that spd-π interaction plays an important role in the sandwich compounds. PMID:23320677

  11. Ultra-Lightweight Nanocomposite Foams and Sandwich Structures for Space Structure Applications

    NASA Technical Reports Server (NTRS)

    Tan, Seng

    2012-01-01

    Microcellular nanocomposite foams and sandwich structures have been created to have excellent electrical conductivity and radiation-resistant properties using a new method that does not involve or release any toxicity. The nanocomposite structures have been scaled up in size to 12 X 12 in. (30 X 30 cm) for components fabrication. These sandwich materials were fabricated mainly from PE, CNF, and carbon fibers. Test results indicate that they have very good compression and compression-after-impact properties, excellent electrical conductivity, and superior space environment durability. Compression tests show that 1000 ESH (equivalent Sun hours) of UV exposure has no effect on the structural properties of the sandwich structures. The structures are considerably lighter than aluminum alloy (= 36 percent lighter), which translates to 36 percent weight savings of the electronic enclosure and its housing. The good mechanical properties of the materials may enable the electronic housing to be fabricated with a thinner structure that further reduces the weight. There was no difficulty in machining the sandwich specimens into electronic enclosure housing.

  12. The Sandwich Generation Diner: Development of a Web-Based Health Intervention for Intergenerational Caregivers

    PubMed Central

    George, Nika; MacDougall, Megan

    2016-01-01

    Background Women are disproportionately likely to assist aging family members; approximately 53 million in the United States are involved with the health care of aging parents, in-laws, or other relatives. The busy schedules of “sandwich generation” women who care for older relatives require accessible and flexible health education, including Web-based approaches. Objective This paper describes the development and implementation of a Web-based health education intervention, The Sandwich Generation Diner, as a tool for intergenerational caregivers of older adults with physical and cognitive impairments. Methods We used Bartholomew’s Intervention Mapping (IM) process to develop our theory-based health education program. Bandura’s (1997) self-efficacy theory provided the overarching theoretical model. Results The Sandwich Generation Diner website features four modules that address specific health care concerns. Our research involves randomly assigning caregiver participants to one of two experimental conditions that are identical in the type of information provided, but vary significantly in the presentation. In addition to structured Web-based assessments, specific website usage data are recorded. Conclusions The Sandwich Generation Diner was developed to address some of the informational and self-efficacy needs of intergenerational female caregivers. The next step is to demonstrate that this intervention is: (1) attractive and effective with families assisting older adults, and (2) feasible to embed within routine home health services for older adults. PMID:27269632

  13. Teacher Professional Development through Sandwich Programmes and Absenteeism in Basic Schools in Ghana

    ERIC Educational Resources Information Center

    Tamanja, Emmanuel Makabu J.

    2016-01-01

    Continuous professional development of teachers plays a crucial role in improving learning outcomes in schools. This study investigated how teaching time is lost when teachers absent themselves to participate in sandwich programmes to upgrade themselves in the University of Education, Winneba (UEW) in Ghana. Using a survey of 475 teachers pursuing…

  14. Qualitative and quantitative detection of T7 bacteriophages using paper based sandwich ELISA.

    PubMed

    Khan, Mohidus Samad; Pande, Tripti; van de Ven, Theo G M

    2015-08-01

    Viruses cause many infectious diseases and consequently epidemic health threats. Paper based diagnostics and filters can offer attractive options for detecting and deactivating pathogens. However, due to their infectious characteristics, virus detection using paper diagnostics is more challenging compared to the detection of bacteria, enzymes, DNA or antigens. The major objective of this study was to prepare reliable, degradable and low cost paper diagnostics to detect viruses, without using sophisticated optical or microfluidic analytical instruments. T7 bacteriophage was used as a model virus. A paper based sandwich ELISA technique was developed to detect and quantify the T7 phages in solution. The paper based sandwich ELISA detected T7 phage concentrations as low as 100 pfu/mL to as high as 10(9) pfu/mL. The compatibility of paper based sandwich ELISA with the conventional titre count was tested using T7 phage solutions of unknown concentrations. The paper based sandwich ELISA technique is faster and economical compared to the traditional detection techniques. Therefore, with proper calibration and right reagents, and by following the biosafety regulations, the paper based technique can be said to be compatible and economical to the sophisticated laboratory diagnostic techniques applied to detect pathogenic viruses and other microorganisms.

  15. Response of Composite Fuselage Sandwich Side Panels Subjected to Internal Pressure and Axial Tension

    NASA Technical Reports Server (NTRS)

    Rouse, Marshall; Ambur, Damodar R.; Dopker, Bernard; Shah, Bharat

    1998-01-01

    The results from an experimental and analytical study of two composite sandwich fuselage side panels for a transport aircraft are presented. Each panel has two window cutouts and three frames and utilizes a distinctly different structural concept. These panels have been evaluated with internal pressure loads that generate biaxial tension loading conditions. Design limit load and design ultimate load tests have been performed on both panels. One of the sandwich panels was tested with the middle frame removed to demonstrate the suitability of this two-frame design for supporting the prescribed biaxial loading conditions with twice the initial frame spacing of 20 inches. A damage tolerance study was conducted on the two-frame panel by cutting a notch in the panel that originates at the edge of a cutout and extends in the panel hoop direction through the window-belt area. This panel with a notch was tested in a combined-load condition to demonstrate the structural damage tolerance at the design limit load condition. Both the sandwich panel designs successfully satisfied all desired load requirements in the experimental part of the study, and experimental results from the two-frame panel with and without damage are fully explained by the analytical results. The results of this study suggest that there is potential for using sandwich structural concepts with greater than the usual 20-in. wide frame spacing to further reduce aircraft fuselage structural weight.

  16. Enhanced thermal stability of functionally graded sandwich cylindrical shells by shape memory alloys

    NASA Astrophysics Data System (ADS)

    Asadi, H.; Akbarzadeh, A. H.; Chen, Z. T.; Aghdam, M. M.

    2015-04-01

    The present paper deals with the nonlinear thermal instability of geometrically imperfect sandwich cylindrical shells under uniform heating. The sandwich shells are made of a shape memory alloy (SMA)-fiber-reinforced composite and functionally graded (FG) face sheets (FG/SMA/FG). The Brinson phenomenological model is used to express the constitutive characteristics of SMA fibers. The governing equations are established within the framework of the third-order shear deformation shell theory by taking into account the von Karman geometrical nonlinearity and initial imperfection. The material properties of constituents are assumed to be temperature dependent. The Galerkin technique is utilized to derive expressions of the bifurcation points and bifurcation paths of the sandwich cylindrical shells. Using the developed closed-form solutions, extensive numerical results are presented to provide an insight into the influence of the SMA fiber volume fraction, SMA pre-strain, core thickness, non-homogeneity index, geometrical imperfection, geometry parameters of sandwich shells and temperature dependency of materials on the stability of shells. The results reveal that proper application of SMA fibers postpones the thermal bifurcation point and dramatically decreases thermal post-buckling deflection. Moreover, the induced tensile recovery stress of SMA fibers could also stabilize the geometrically imperfect shells during the inverse martensite phase transformation.

  17. Effect of the parameters of a sandwich structure with a honeycomb core on its soundproofing capacity

    NASA Astrophysics Data System (ADS)

    Tkachev, A. A.

    Expressions for estimating the soundproofing capacity of sandwich structures with a honeycomb core are obtained by using equations of transverse vibrations of a plate with allowance for the flexural and shear waves. The expressions provide an adequate description of the experimentally observed effects and make it possible to predict the effect of the parameters of a structure on its soundproofing efficiency.

  18. Introduction to Sandwiches. Learning Activity Pack and Instructor's Guide 5.4a. Commercial Foods and Culinary Arts Competency-Based Series. Section 5: Basic Food Preparation.

    ERIC Educational Resources Information Center

    Florida State Univ., Tallahassee. Center for Studies in Vocational Education.

    This document consists of a learning activity packet (LAP) for the student and an instructor's guide for the teacher. The LAP is intended to acquaint occupational home economics students with types of sandwiches and their ingredients, to give tips on making and handling sandwich ingredients, and to explain how to set up a sandwich counter.…

  19. Survival of Salmonella in Cookie and Cracker Sandwiches Containing Inoculated, Low-Water Activity Fillings.

    PubMed

    Beuchat, Larry R; Mann, David A

    2015-10-01

    A study was done to determine the rate of inactivation of Salmonella in cookie and cracker snack sandwiches. Two cookie bases (chocolate and vanilla) and cheese crackers, along with high-sugar chocolate and peanut butter-based crème cookie fillings and peanut butter- and cheese-based cracker fillings, were obtained from commercial sources. Fillings and sandwiches containing fillings that had been dry- or wet-inoculated with Salmonella were stored at 25°C for 1, 6, 21, 35, 70, 112, and 182 days (6 months). At initial populations of 3.4 and 3.6 log CFU/g of cookie sandwiches containing chocolate crème and peanut butter crème fillings, respectively, Salmonella survived for at least 182 days; initially at 0.36 log CFU/g, the pathogen survived for at least 35 and 70 days. Initially at 2.9 and 3.4 log CFU/g of cracker sandwiches containing peanut butter- and cheese-based fillings, respectively, Salmonella survived for at least 182 and 112 days; initially at 0.53 log CFU/g, the pathogen survived for at least 6 and 35 days. Inactivation of Salmonella was more rapid in wet-inoculated peanut butter crème cookie filling than in dry-inoculated filling but was less affected by type of inoculum in peanut butter-based cracker filling. Chocolate cookie base (water activity [aw] 0.39) and chocolate crème filling (aw 0.30) components of sandwiches equilibrated to aw 0.38 within 15 days at 25°C; vanilla cookie base (aw 0.21) and peanut butter-based crème filling (aw 0.27) equilibrated to aw 0.24 between 50 and 80 days. Cheese cracker (aw 0.14) and peanut butter-based filling (aw 0.31) or cheese-based filling (aw 0.33) components of sandwiches equilibrated to aw 0.33 in 80 days. The ability of Salmonella to survive for at least 182 days in fillings of cookie and cracker sandwiches demonstrates a need to assure that filling ingredients do not contain the pathogen and that contamination does not occur during manufacture.

  20. Survival of Salmonella in Cookie and Cracker Sandwiches Containing Inoculated, Low-Water Activity Fillings.

    PubMed

    Beuchat, Larry R; Mann, David A

    2015-10-01

    A study was done to determine the rate of inactivation of Salmonella in cookie and cracker snack sandwiches. Two cookie bases (chocolate and vanilla) and cheese crackers, along with high-sugar chocolate and peanut butter-based crème cookie fillings and peanut butter- and cheese-based cracker fillings, were obtained from commercial sources. Fillings and sandwiches containing fillings that had been dry- or wet-inoculated with Salmonella were stored at 25°C for 1, 6, 21, 35, 70, 112, and 182 days (6 months). At initial populations of 3.4 and 3.6 log CFU/g of cookie sandwiches containing chocolate crème and peanut butter crème fillings, respectively, Salmonella survived for at least 182 days; initially at 0.36 log CFU/g, the pathogen survived for at least 35 and 70 days. Initially at 2.9 and 3.4 log CFU/g of cracker sandwiches containing peanut butter- and cheese-based fillings, respectively, Salmonella survived for at least 182 and 112 days; initially at 0.53 log CFU/g, the pathogen survived for at least 6 and 35 days. Inactivation of Salmonella was more rapid in wet-inoculated peanut butter crème cookie filling than in dry-inoculated filling but was less affected by type of inoculum in peanut butter-based cracker filling. Chocolate cookie base (water activity [aw] 0.39) and chocolate crème filling (aw 0.30) components of sandwiches equilibrated to aw 0.38 within 15 days at 25°C; vanilla cookie base (aw 0.21) and peanut butter-based crème filling (aw 0.27) equilibrated to aw 0.24 between 50 and 80 days. Cheese cracker (aw 0.14) and peanut butter-based filling (aw 0.31) or cheese-based filling (aw 0.33) components of sandwiches equilibrated to aw 0.33 in 80 days. The ability of Salmonella to survive for at least 182 days in fillings of cookie and cracker sandwiches demonstrates a need to assure that filling ingredients do not contain the pathogen and that contamination does not occur during manufacture. PMID:26408131

  1. Thermo-structural optimization of all-metallic prismatic sandwich panels

    NASA Astrophysics Data System (ADS)

    Valdevit, Lorenzo

    All-metallic sandwich panels with prismatic cores offer tremendous potential for thermostructural applications, due to their exceptional bending response together with the possibility of driving a fluid through their open cores, thus enabling active cooling. This thesis offers a complete thermo-mechanical characterization of prismatic panels with both corrugated and diamond cores, with main emphasis on geometric optimization. For the mechanical study, the panel geometry is analytically optimized for minimum weight under any combination of bending and transverse shear force. For longitudinal loadings (i.e. bending axis parallel to the core corrugation direction), corrugated panels show excellent performance, equivalent to the best concepts available; for transverse loadings (i.e. bending axis perpendicular to the corrugation direction), this goal is achieved with diamond core designs. Failure maps are constructed based on the analytical model to provide easy visualization of the failure modes and allow immediate identification of optimal designs. Such maps are used to design a selected number of experiments, with the three-fold goal of (i) validating the analytical model, (ii) exploring the behavior subsequent to failure initiation (thus assessing the robustness of the chosen designs), and (iii) check the reliability of numerical simulations in capturing limit loads and deformation modes. Good agreement is achieved among analytical, computational and experimental results. In order to assess the active cooling performance of prismatic panels, a scenario is envisioned where a uniform heat flux is impinging on one face, with the rest of the panel being thermally insulated; under these conditions, all the heat flux is transferred to a cooling fluid flowing through the core channels. At any given level of the pressure drop, the panel geometry is optimized for maximum transferred heat flux subject to a temperature constraint on the structure. Although very large optimal

  2. Metal Foam Analysis: Improving Sandwich Structure Technology for Engine Fan and Propeller Blades

    NASA Technical Reports Server (NTRS)

    Fedor, Jessica L.

    2004-01-01

    The Life Prediction Branch of the NASA Glenn Research Center is searching for ways to construct aircraft and rotorcraft engine fan and propeller blades that are lighter and less costly. One possible design is to create a sandwich structure composed of two metal faces sheets and a metal foam core. The face sheets would carry the bending loads and the foam core would have to resist the transverse shear loads. Metal foam is ideal because of its low density and energy absorption capabilities, making the structure lighter, yet still stiff. The material chosen for the face sheets and core was 17-4PH stainless steel, which is easy to make and has appealing mechanical properties. This material can be made inexpensively compared to titanium and polymer matrix composites, the two current fan blade alternatives. Initial tests were performed on design models, including vibration and stress analysis. These tests revealed that the design is competitive with existing designs; however, some problems were apparent that must be addressed before it can be implemented in new technology. The foam did not hold up as well as expected under stress. This could be due to a number of issues, but was most likely a result of a large number of pores within the steel that weakened the structure. The brazing between the face sheets and the foam was also identified as a concern. The braze did not hold up well under shear stress causing the foam to break away from the face sheets. My role in this project was to analyze different options for improving the design. I primarily spent my time examining various foam samples, created with different sintering conditions, to see which exhibited the most favorable characteristics for our purpose. Methods of analysis that I employed included examining strut integrity under a microscope, counting the number of cells per inch, measuring the density, testing the microhardness, and testing the strength under compression. Shear testing will also be done to examine

  3. Full-scale testing and progressive damage modeling of sandwich composite aircraft fuselage structure

    NASA Astrophysics Data System (ADS)

    Leone, Frank A., Jr.

    A comprehensive experimental and computational investigation was conducted to characterize the fracture behavior and structural response of large sandwich composite aircraft fuselage panels containing artificial damage in the form of holes and notches. Full-scale tests were conducted where panels were subjected to quasi-static combined pressure, hoop, and axial loading up to failure. The panels were constructed using plain-weave carbon/epoxy prepreg face sheets and a Nomex honeycomb core. Panel deformation and notch tip damage development were monitored during the tests using several techniques, including optical observations, strain gages, digital image correlation (DIC), acoustic emission (AE), and frequency response (FR). Additional pretest and posttest inspections were performed via thermography, computer-aided tap tests, ultrasound, x-radiography, and scanning electron microscopy. The framework to simulate damage progression and to predict residual strength through use of the finite element (FE) method was developed. The DIC provided local and full-field strain fields corresponding to changes in the state-of-damage and identified the strain components driving damage progression. AE was monitored during loading of all panels and data analysis methodologies were developed to enable real-time determination of damage initiation, progression, and severity in large composite structures. The FR technique has been developed, evaluating its potential as a real-time nondestructive inspection technique applicable to large composite structures. Due to the large disparity in scale between the fuselage panels and the artificial damage, a global/local analysis was performed. The global FE models fully represented the specific geometries, composite lay-ups, and loading mechanisms of the full-scale tests. A progressive damage model was implemented in the local FE models, allowing the gradual failure of elements in the vicinity of the artificial damage. A set of modifications

  4. Bending and Forced Vibration Response of a Clamped Orthotropic Thick Plate and Sandwich Panel

    NASA Astrophysics Data System (ADS)

    LOK, T. S.; CHENG, Q. H.

    2001-08-01

    A closed-form solution for the forced response of an orthotropic thick plate and sandwich panel has been developed and is presented in this paper. The paper outlines the methodology and develops the formulation to enable the solution to be derived. A novel truss-core sandwich panel is introduced and a method is outlined in which the panel is represented as an equivalent homogeneous orthotropic thick plate continuum. The 3-D dynamic finite element method is one of the most versatile developments of the 20th century. However, the software is not as accessible or as user-friendly for engineers who are not trained in such analytical tools. Therefore, alternative methods of analysis must be found, especially in the dynamic assessment of thin-walled truss-core sandwich panels. One way is to transform the sandwich structure into an equivalent homogeneous orthotropic thick plate continuum and to conduct the analysis on the equivalent model. The authors have derived the necessary elastic constants to hasten this transformation. In this paper, the derived elastic constants are used with closed-form solution to determine the bending and forced vibration response of a clamped truss-core sandwich panel, represented as a homogeneous orthotropic thick plate continuum. The Rayleigh-Ritz method is employed for the closed-form solution and the forced response is determined using Duhamel's integral. Admissible functions are taken as a series of products of beam mode-shape functions in the two orthogonal directions. The beam function in either direction is derived from the corresponding beam eigenvalue problem. Numerical examples, which include the influence of transverse shear on the response, show that the closed-form solution agrees with analytical and numerical data available in the literature and also with 3-D finite element results.

  5. The degree of π electron delocalization and the formation of 3D-extensible sandwich structures.

    PubMed

    Wang, Xiang; Wang, Qiang; Yuan, Caixia; Zhao, Xue-Feng; Li, Jia-Jia; Li, Debao; Wu, Yan-Bo; Wang, Xiaotai

    2016-04-28

    DFT B3LYP/6-31G(d) calculations were performed to examine the feasibility of graphene-like C42H18 and starbenzene C6(BeH)6 (SBz) polymers as ligands of 3D-extensible sandwich compounds (3D-ESCs) with uninterrupted sandwich arrays. The results revealed that sandwich compounds with three or more C42H18 ligands were not feasible. The possible reason may be the localization of π electrons on certain C6 hexagons due to π-metal interactions, which makes the whole ligand lose its electronic structure basis (higher degree of π electron delocalization) to maintain the planar structure. For comparison, with the aid of benzene (Bz) molecules, the SBz polymers can be feasible ligands for designing 3D-ESCs because the C-Be interactions in individual SBz are largely ionic, which will deter the π electrons on one C6 ring from connecting to those on neighbouring C6 rings. This means that high degree of π electron delocalization is not necessary for maintaining the planarity of SBz polymers. Such a locally delocalized π electron structure is desirable for the ligands of 3D-ESCs. Remarkably, the formation of a sandwich compound with SBz is thermodynamically more favourable than that found for bis(Bz)chromium. The assembly of 3D-ESCs is largely exothermic, which will facilitate future experimental synthesis. The different variation trends on the HOMO-LUMO gaps in different directions (relative to the sandwich axes) suggest that they can be developed to form directional conductors or semiconductors, which may be useful in the production of electronic devices. PMID:27004750

  6. Analysis of wave propagation in sandwich plates with and without heavy fluid loading

    NASA Astrophysics Data System (ADS)

    Sorokin, S. V.

    2004-04-01

    The paper addresses wave motions in an unbounded sandwich plate with and without heavy fluid loading in a plane problem formulation. A sandwich plate is composed of two identical isotropic skin plies and an isotropic core ply. Several alternative theories for stationary dynamics of such a plate or a beam are derived, including a formulation in the framework of a theory of elasticity applied for a core ply. 'In-phase' and 'anti-phase' wave motions (with respect to transverse deflections of skins) of a sandwich beam are analyzed independently of each other. Dispersion curves obtained by the use of 'elementary' theories are compared with those obtained by the use of an 'exact' theory (which involves the theory of elasticity in a description of wave motion in a core ply) for a plate without fluid loading. It is shown that these simplified models are capable of giving a complete and accurate description of all propagating waves in not too high-frequency range, which is sufficient in practical naval and aerospace engineering. In the case of heavy fluid loading, similar analysis is performed for 'anti-phase' wave motions of a beam. Two simplified theories as well as an 'exact' one are extended to capture fluid loading effects. A good agreement between results obtained in 'elementary' and 'exact' problem formulations is demonstrated. The role of fluid's compressibility in the generation of propagating waves in a sandwich plate is explored. It is shown that, whereas analysis of wave motions in the case of an incompressible fluid predicts an existence of two propagating waves, only one such wave exists when a fluid is sufficiently compressible. The threshold magnitude of the ratio of a sound speed in an acoustic medium to a sound speed in a skin's material is found, which separates these two regimes of wave motions for a given set of parameters of sandwich plate composition.

  7. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1995-01-01

    Part of the 1994 Industrial Minerals Review. The production, consumption, and applications of construction aggregates are reviewed. In 1994, the production of construction aggregates, which includes crushed stone and construction sand and gravel combined, increased 7.7 percent to 2.14 Gt compared with the previous year. These record production levels are mostly a result of funding for highway construction work provided by the Intermodal Surface Transportation Efficiency Act of 1991. Demand is expected to increase for construction aggregates in 1995.

  8. A packaged, low-cost, robust optical fiber strain sensor based on small cladding fiber sandwiched within periodic polymer grating.

    PubMed

    Chiang, Chia-Chin; Li, Chein-Hsing

    2014-06-01

    In the present study, a novel packaged long-period fiber grating (PLPFG) strain sensor is first presented. The MEMS process was utilized to fabricate the packaged optical fiber strain sensor. The sensor structure consisted of etched optical fiber sandwiched between two layers of thick photoresist SU-8 3050 and then packaged with poly (dimethylsiloxane) (PDMS) polymer material to construct the PLPFG strain sensor. The PDMS packaging material was used to prevent the glue effect, wherein glue flows into the LPFG structure and reduces coupling strength, in the surface bonding process. Because the fiber grating was packaged with PDMS material, it was effectively protected and made robust. The resonance attenuation dip of PLPFG grows when it is loading. This study explored the size effect of the grating period and fiber diameter of PLPFG via tensile testing. The experimental results found that the best strain sensitivity of the PLPFG strain sensor was -0.0342 dB/με, and that an R2 value of 0.963 was reached.

  9. A Disulfide Stabilized β-Sandwich Defines the Structure of a New Cysteine Framework M-Superfamily Conotoxin.

    PubMed

    Kancherla, Aswani K; Meesala, Srinu; Jorwal, Pooja; Palanisamy, Ramasamy; Sikdar, Sujit K; Sarma, Siddhartha P

    2015-08-21

    The structure of a new cysteine framework (-C-CC-C-C-C-) "M"-superfamily conotoxin, Mo3964, shows it to have a β-sandwich structure that is stabilized by inter-sheet cross disulfide bonds. Mo3964 decreases outward K(+) currents in rat dorsal root ganglion neurons and increases the reversal potential of the NaV1.2 channels. The structure of Mo3964 (PDB ID: 2MW7 ) is constructed from the disulfide connectivity pattern, i.e., 1-3, 2-5, and 4-6, that is hitherto undescribed for the "M"-superfamily conotoxins. The tertiary structural fold has not been described for any of the known conus peptides. NOE (549), dihedral angle (84), and hydrogen bond (28) restraints, obtained by measurement of (h3)JNC' scalar couplings, were used as input for structure calculation. The ensemble of structures showed a backbone root mean square deviation of 0.68 ± 0.18 Å, with 87% and 13% of the backbone dihedral (ϕ, ψ) angles lying in the most favored and additional allowed regions of the Ramachandran map. The conotoxin Mo3964 represents a new bioactive peptide fold that is stabilized by disulfide bonds and adds to the existing repertoire of scaffolds that can be used to design stable bioactive peptide molecules. PMID:25961405

  10. Development of sandwich ELISA for detection and quantification of invertebrate major allergen tropomyosin by a monoclonal antibody.

    PubMed

    Zhang, Hong; Lu, Ying; Ushio, Hideki; Shiomi, Kazuo

    2014-05-01

    Muscle protein tropomyosins of invertebrates are major allergens responsible for wide spread allergic reactions against invertebrates such as shellfish and insects. In order to develop a sandwich enzyme-linked immunoadsorbent assay (ELISA) for detection and quantification of the invertebrate pan-allergen tropomyosin, a specific monoclonal antibody (MAb), CE7B2, was produced. We have successfully established a sandwich ELISA for measuring invertebrate tropomyosin concentrations in food and food materials. The sandwich ELISA system using the MAb CE7B2 is a useful tool to detect and quantify levels of tropomyosin in food. The method is also helpful to detect mite and cockroach tropomyosins, the important indoor allergens.

  11. Electrochemical construction

    DOEpatents

    Einstein, Harry; Grimes, Patrick G.

    1983-08-23

    An electrochemical cell construction features a novel co-extruded plastic electrode in an interleaved construction with a novel integral separator-spacer. Also featured is a leak and impact resistant construction for preventing the spill of corrosive materials in the event of rupture.

  12. Sandwich type plasmonic platform for MEF using silver fractals.

    PubMed

    Raut, Sangram L; Rich, Ryan; Shtoyko, Tanya; Bora, Ilkay; Laursen, Bo W; Sørensen, Thomas Just; Borejdo, Julian; Gryczynski, Zygmunt; Gryczynski, Ignacy

    2015-11-14

    In this report, we describe a plasmonic platform with silver fractals for metal enhanced fluorescence (MEF) measurements. When a dye containing surface was brought into contact with silver fractals, a significantly enhanced fluorescence signal from the dye was observed. Fluorescence enhancement was studied with the N-methyl-azadioxatriangulenium chloride salt (Me-ADOTA·Cl) in PVA films made from 0.2% PVA (w/v) solution spin-coated on a clean glass coverslip. The Plasmonic Platforms (PP) were assembled by pressing together silver fractals on one glass slide and a separate glass coverslip spin-coated with a uniform Me-ADOTA·Cl in PVA film. In addition, we also tested ADOTA labeled human serum albumin (HSA) deposited on a glass slide for potential PP bioassay applications. Using the new PP, we could achieve more than a 20-fold fluorescence enhancement (bright spots) accompanied by a decrease in the fluorescence lifetime. The experimental results were used to calculate the extinction (excitation) enhancement factor (GA) and fluorescence radiative rate enhancements factor (GF). No change in emission spectrum was observed for a dye with or without contact with fractals. Our studies indicate that this type of PP can be a convenient approach for constructing assays utilizing metal enhanced fluorescence (MEF) without the need for depositing the material directly on metal structures platforms.

  13. Clay Nanocomposite/Aerogel Sandwich Structures for Cryotanks

    NASA Technical Reports Server (NTRS)

    Miller, Sandi; Leventis, Nicholas; Johnston, J. Chris; Meador, Michael

    2006-01-01

    GRC research has led to the development of epoxy-clay nanocomposites with 60-70% lower gas permeability than the base epoxy resin. Filament wound carbon fiber reinforced tanks made with this nanocomposite had a five-fold lower helium leak rate than the corresponding tanks made without clay. More recent work has produced new composites with more than a 100-fold reduction in helium permeability. Use of these advanced, high barrier composites would eliminate the need for a liner in composite cryotanks, thereby simplifying construction and reducing propellant leakage. Aerogels are attractive materials for use as cryotank insulation because of their low density and low thermal conductivity. However, aerogels are fragile and have poor environmental stability, which have limited their use to certain applications in specialized environments (e.g., in certain types of nuclear reactors as Cerenkov radiation detectors, and as thermal insulators aboard space rovers on Mars). New GRC developed polymer crosslinked aerogels (X-Aerogels) retain the low density of conventional aerogels, but they demonstrate a 300-fold increase in their mechanical strength. Currently, our strongest materials combine a density of approx. 0.45 g/cc, a thermal conductivity of approx. 0.04 W/mK and a compressive strength of 185 MPa. Use of these novel aerogels as insulation materials/structural components in combination with the low permeability of epoxy-clay nanocomposites could significantly reduce cryotank weight and improve durability.

  14. Analysis of Thick Sandwich Shells with Embedded Ceramic Tiles

    NASA Technical Reports Server (NTRS)

    Davila, Carlos G.; Smith, C.; Lumban-Tobing, F.

    1996-01-01

    The Composite Armored Vehicle (CAV) is an advanced technology demonstrator of an all-composite ground combat vehicle. The CAV upper hull is made of a tough light-weight S2-glass/epoxy laminate with embedded ceramic tiles that serve as armor. The tiles are bonded to a rubber mat with a carefully selected, highly viscoelastic adhesive. The integration of armor and structure offers an efficient combination of ballistic protection and structural performance. The analysis of this anisotropic construction, with its inherent discontinuous and periodic nature, however, poses several challenges. The present paper describes a shell-based 'element-layering' technique that properly accounts for these effects and for the concentrated transverse shear flexibility in the rubber mat. One of the most important advantages of the element-layering technique over advanced higher-order elements is that it is based on conventional elements. This advantage allows the models to be portable to other structural analysis codes, a prerequisite in a program that involves the computational facilities of several manufacturers and government laboratories. The element-layering technique was implemented into an auto-layering program that automatically transforms a conventional shell model into a multi-layered model. The effects of tile layer homogenization, tile placement patterns, and tile gap size on the analysis results are described.

  15. Working Sandwich Generation Women Utilize Strategies within and between Roles to Achieve Role Balance.

    PubMed

    Evans, Kiah L; Millsteed, Jeannine; Richmond, Janet E; Falkmer, Marita; Falkmer, Torbjorn; Girdler, Sonya J

    2016-01-01

    Increasingly, women simultaneously balance the roles of mother, parental carer and worker. However, individual role balance strategies among these working 'sandwich' generation women have not been thoroughly explored. Eighteen women combining these three roles were interviewed about their individual role balance strategies. Findings were identified through the framework analysis technique, underpinned by the Model of Juggling Occupations. Achieving and maintaining role balance was explained as a complex process accomplished through a range of strategies. Findings revealed the women used six within-role balance strategies: living with integrity, being the best you can, doing what you love, loving what you do, remembering why and searching for signs of success. The women also described six between-role balance strategies: maintaining health and wellbeing, repressing perfectionism, managing time and energy, releasing responsibility, nurturing social connection and reciprocating. These findings provide a basis for health care providers to understand and potentially support working 'sandwich' generation women.

  16. Durable and Efficient PTFE Sandwiched SPEEK Membrane for Vanadium Flow Batteries.

    PubMed

    Yu, Lihong; Xi, Jingyu

    2016-09-14

    To overcome the poor cycling stability of sulfonated poly(ether ether ketone) (SPEEK) membrane in vanadium flow batteries (VFB), we demonstrate a facile and effective sandwich design by using hydrophilic porous poly(tetrafluoroethylene) (PTFE) films as a stress protective and electrolyte buffer layer for SPEEK membrane. VFB based on this novel sandwich PTFE/SPEEK/PTFE membrane exhibits super long-life properties, which can steadily run (98.5% of Coulombic efficiency and 85.0% of energy efficiency @ 80 mA cm(-2)) with 2.0 M vanadium electrolyte for more than 1000 cycles. This simple and powerful strategy may also be applied to other nonfluoride membranes. PMID:27576544

  17. Multilayer Roll-Bonded Sandwich: Processing, Mechanical Performance, and Bioactive Behavior

    SciTech Connect

    Palkowski H.; Stanic V.; Carrado, A.

    2012-03-30

    Multifunctionality and improving the properties of materials make it necessary to use hybrid systems such as combinations of metals with polymers. Their applications can be found in all areas where light weight and improved and adapted mechanical properties as well as high functionality are needed. Moreover, tailored types of hybrids can be interesting for biomedical applications, as under specific conditions they show, e.g., good strength combined with high elasticity. Herein, we present preliminary tests on the biomimetic behavior of AISI SS316L/polypropylene copolymer/AISI SS316L sandwich. Biomimetic coatings were produced by inducing a calcium phosphate layer in a way similar to the process of natural bone formation. Knowledge of the formability of three-layered sandwich sheets and their biomimetic behavior is presented.

  18. Analysis of a ceramic filled bio-plastic composite sandwich structure

    SciTech Connect

    Habib Ullah, M.; Islam, M. T.

    2013-11-25

    Design and analysis of a ceramic-filled bio-plastic composite sandwich structure is presented. This proposed high-dielectric structure is used as a substrate for patch antennas. A meandered-strip line-fed fractal-shape patch antenna is designed and fabricated on a copper-laminated sandwich-structured substrate. Measurement results of this antenna show 44% and 20% of bandwidths with maximum gains of 3.45 dBi and 5.87 dBi for the lower and upper bands, respectively. The half-power beam widths of 104° and 78° have been observed from the measured radiation pattern at the two resonance frequencies 0.9 GHz and 2.5 GHz.

  19. A literature review on computational models for laminated composite and sandwich panels

    NASA Astrophysics Data System (ADS)

    Kreja, Ireneusz

    2011-03-01

    The present paper is devoted to a state-of-the-art review on the computational treatment of laminated composite and sandwich panels. Over two hundred texts have been included in the survey with the focus put on theoretical models for multilayered plates and shells, and FEM implementation of various computational concepts. As a result of the review, one could notice a lack of a single numerical model capable for a universal representation of all layered composite and sandwich panels. Usually, with the increase of the range of rotations considered in the particular model, one can observe the decrease of the degree of complexity of the through-the-thickness representation of deformation profiles.

  20. Analysis of a ceramic filled bio-plastic composite sandwich structure

    NASA Astrophysics Data System (ADS)

    Habib Ullah, M.; Islam, M. T.

    2013-11-01

    Design and analysis of a ceramic-filled bio-plastic composite sandwich structure is presented. This proposed high-dielectric structure is used as a substrate for patch antennas. A meandered-strip line-fed fractal-shape patch antenna is designed and fabricated on a copper-laminated sandwich-structured substrate. Measurement results of this antenna show 44% and 20% of bandwidths with maximum gains of 3.45 dBi and 5.87 dBi for the lower and upper bands, respectively. The half-power beam widths of 104° and 78° have been observed from the measured radiation pattern at the two resonance frequencies 0.9 GHz and 2.5 GHz.

  1. Working Sandwich Generation Women Utilize Strategies within and between Roles to Achieve Role Balance.

    PubMed

    Evans, Kiah L; Millsteed, Jeannine; Richmond, Janet E; Falkmer, Marita; Falkmer, Torbjorn; Girdler, Sonya J

    2016-01-01

    Increasingly, women simultaneously balance the roles of mother, parental carer and worker. However, individual role balance strategies among these working 'sandwich' generation women have not been thoroughly explored. Eighteen women combining these three roles were interviewed about their individual role balance strategies. Findings were identified through the framework analysis technique, underpinned by the Model of Juggling Occupations. Achieving and maintaining role balance was explained as a complex process accomplished through a range of strategies. Findings revealed the women used six within-role balance strategies: living with integrity, being the best you can, doing what you love, loving what you do, remembering why and searching for signs of success. The women also described six between-role balance strategies: maintaining health and wellbeing, repressing perfectionism, managing time and energy, releasing responsibility, nurturing social connection and reciprocating. These findings provide a basis for health care providers to understand and potentially support working 'sandwich' generation women. PMID:27305074

  2. Development of lightweight graphite/polyimide sandwich panels, phases 3, 4 and 5

    NASA Technical Reports Server (NTRS)

    Merlette, J. B.

    1972-01-01

    Work performed in the last three phases of the program included: (1) face sheet processing; (2) honeycomb core manufacture; (3) face sheet-to-core bonding development; and (4) sandwich panel fabrication and testing. Resin cure studies were a major portion of this effort since processing problems traced to the polyimide matrix resin had to be resolved before quality core and face sheets could be fabricated. Honeycomb core fabrication and testing were conducted by Hexcel Corporation. A total of four graphite/polyimide resin composite cores were fabricated, tested, and reported. Two sandwich panels weighing .48 and .58 lb/sq ft, respectively were designed and fabricated which meet the support structure loads for the shuttle orbiter thermal protection system.

  3. High-Fidelity Modeling for Health Monitoring in Honeycomb Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Luchinsky, Dimitry G.; Hafiychuk, Vasyl; Smelyanskiy, Vadim; Tyson, Richard W.; Walker, James L.; Miller, Jimmy L.

    2011-01-01

    High-Fidelity Model of the sandwich composite structure with real geometry is reported. The model includes two composite facesheets, honeycomb core, piezoelectric actuator/sensors, adhesive layers, and the impactor. The novel feature of the model is that it includes modeling of the impact and wave propagation in the structure before and after the impact. Results of modeling of the wave propagation, impact, and damage detection in sandwich honeycomb plates using piezoelectric actuator/sensor scheme are reported. The results of the simulations are compared with the experimental results. It is shown that the model is suitable for analysis of the physics of failure due to the impact and for testing structural health monitoring schemes based on guided wave propagation.

  4. Identification of honeycomb sandwich properties by high-resolution modal analysis

    NASA Astrophysics Data System (ADS)

    Rebillat, M.; Boutillon, X.

    2010-06-01

    A method is proposed to identify the mechanical properties of the skin and core materials of honeycomb sandwich. All the elastic coefficients and loss-factors that matter in the dynamics of a panel in the thick-plate approximation are identified. To this end, experimental natural modes (i.e. eigenmodes of the damped system) are compared to the numerical modes of a large sandwich panel (lx,y/h ≃ 80). The chosen generic model for the visco-elastic behaviour of the materials is E (1 + jη). The numerical modes are computed by means of a Rayleigh-Ritz procedure and their dampings are predicted according to the visco-elastic model. The frequencies and dampings of the natural modes of the panel are estimated experimentally by means of a high-resolution modal analysis technique. An optimisation procedure yields the desired coefficients. A sensitivity analysis assess the reliability of the method.

  5. Characterization of compressive and short beam shear strength of bamboo opened cell foam core sandwich composites

    NASA Astrophysics Data System (ADS)

    Setyawan, Paryanto Dwi; Sugiman, Saputra, Yudhi

    2016-03-01

    The paper presents the compressive and the short beam shear strength of a sandwich composite with opened cell foam made of bamboo fiber as the core and plywood as the skins. The core thickness was varied from 10 mm to 40 mm keeping the volume fraction of fiber constant. Several test s were carried out including the core density, flatwise compressive and the short beam shear testing in three point bending. The results show that the density of bamboo opened cell foam is comparable with commercial plastic foam, such as polyurethane foam. The compressive strength tends to increase linearly with increasing the core thickness. The short beam shear failure load of the sandwich composite increases with the increase of core thickness, however on the contrary, the short beam shear strength which tends to sharply decrease from the thickness of 10 mm to 30 mm and then becomes flat.

  6. Fused-silica sandwiched three-port grating under second Bragg angle incidence

    NASA Astrophysics Data System (ADS)

    Li, Hongtao; Wang, Bo; Pei, Hao; Chen, Li; Lei, Liang; Zhou, Jinyun

    2016-05-01

    The fused-silica sandwiched three-port grating under second Bragg angle incidence is presented with operation in transmission. To obtain a highly-efficient three-port grating for a working wavelength of 800 nm, the grating depth and period should be optimized by using rigorous coupled-wave analysis. With the optimized different three-port grating depths and periods, both TE-polarized and TM-polarized waves can be diffracted into three orders with nearly 33% efficiency for the given duty cycle of 0.6. Based on the grating parameters of numerical optimization, modal method may be employed to explain the physical mechanism of the beam propagation in the grating and analyze the splitting behavior. For the sandwiched three-port grating, it is feasible that the diffraction efficiencies can be enhanced for both TE and TM polarizations.

  7. Numerical Simulation of Impact Responses on Through-thickness Stitched Foam Core Sandwich Composite

    NASA Astrophysics Data System (ADS)

    Xia, Fan; Wu, Xiao-Qing; Li, Jia-Lu

    2013-12-01

    This paper was based on the explicit finite element codes to predict the impact behavior of through-thickness stitched foam core sandwich composites. It is proposed that the extent of the impact damage can be characterized by the token parameters of cracking width, penetration depth and damage angle; and observations made during the simulative analysis with such damage parameters. The results show that the same tendencies and characteristics are shown on the numerical and test results of impact force-displacement plots, and a good agreement is also obtained in damage parameters. In comparing the unstitched types, the through-thickness stitched sandwiches are optimal for both the peak loads shown on the numerical plots at 25.0 J; and demonstrate the fewer extent of impact damage with a 63.5 and 6.0 % decreasing to the cracking width and penetration depth respectively, and where a 52.0 % increasing to the damage angle.

  8. A Finite Element Analysis for Predicting the Residual Compression Strength of Impact-Damaged Sandwich Panels

    NASA Technical Reports Server (NTRS)

    Ratcliffe, James G.; Jackson, Wade C.

    2008-01-01

    A simple analysis method has been developed for predicting the residual compression strength of impact-damaged sandwich panels. The method is tailored for honeycomb core-based sandwich specimens that exhibit an indentation growth failure mode under axial compression loading, which is driven largely by the crushing behavior of the core material. The analysis method is in the form of a finite element model, where the impact-damaged facesheet is represented using shell elements and the core material is represented using spring elements, aligned in the thickness direction of the core. The nonlinear crush response of the core material used in the analysis is based on data from flatwise compression tests. A comparison with a previous analysis method and some experimental data shows good agreement with results from this new approach.

  9. A Finite Element Analysis for Predicting the Residual Compressive Strength of Impact-Damaged Sandwich Panels

    NASA Technical Reports Server (NTRS)

    Ratcliffe, James G.; Jackson, Wade C.

    2008-01-01

    A simple analysis method has been developed for predicting the residual compressive strength of impact-damaged sandwich panels. The method is tailored for honeycomb core-based sandwich specimens that exhibit an indentation growth failure mode under axial compressive loading, which is driven largely by the crushing behavior of the core material. The analysis method is in the form of a finite element model, where the impact-damaged facesheet is represented using shell elements and the core material is represented using spring elements, aligned in the thickness direction of the core. The nonlinear crush response of the core material used in the analysis is based on data from flatwise compression tests. A comparison with a previous analysis method and some experimental data shows good agreement with results from this new approach.

  10. Dual-wavelength polymer laser based on an active/inactive/active sandwich-like structure

    NASA Astrophysics Data System (ADS)

    Zhai, Tianrui; Wu, Xiaofeng; Wang, Meng; Tong, Fei; Li, Songtao; Ma, Yanbin; Deng, Jinxiang; Zhang, Xinping

    2016-09-01

    Dual-wavelength laser emission is achieved by using an active/inactive/active sandwich-like structure, which can be conveniently fabricated using spin coating technique. Poly [(9, 9-dioctylfluorenyl-2, 7-diyl)-alt-co-(1, 4-benzo-(2, 1', 3) -thiadiazole)] and polyvinyl alcohol are employed as the active and the inactive materials, respectively. Two laser wavelengths are simultaneously observed, which are attributed to the difference of the surrounding refractive index of two active waveguides in the sandwich-like structure. Each wavelength is controlled by the respective waveguide structure, meaning that multi-wavelength laser can be designed by stacking the active/inactive layer pair. These results provide more flexibility to design compact laser sources.

  11. Flutter of a sandwich cylindrical shell supported with annular ribs and loaded with axial forces

    NASA Astrophysics Data System (ADS)

    Bakulin, V. N.; Volkov, E. N.; Nedbaj, A. Ya.

    2015-08-01

    The supersonic flutter of a sandwich cylindrical shell supported from within with annular ribs and loaded with axial forces on the end faces is investigated. The shell motion is described by the equations of the theory of sandwich orthotropic shells. The solution of the equations is sought as a trigonometric series with respect to the axial coordinate. With the help of the Bubnov—Galerkin method, this problem is reduced to the set of algebraic equations for the analysis of the stability of which one uses the Routh—Hurwits criterion. By a numerical example, the effect of the number and the heights of the ribs on the critical velocity of the flow around the shell is shown.

  12. Fabrication of anti-protein-fouling poly(ethylene glycol) microfluidic chip electrophoresis by sandwich photolithography.

    PubMed

    Cong, Hailin; Xu, Xiaodan; Yu, Bing; Liu, Huwei; Yuan, Hua

    2016-07-01

    Microfluidic chip electrophoresis (MCE) is a powerful separation tool for biomacromolecule analysis. However, adsorption of biomacromolecules, particularly proteins onto microfluidic channels severely degrades the separation performance of MCE. In this paper, an anti-protein-fouling MCE was fabricated using a novel sandwich photolithography of poly(ethylene glycol) (PEG) prepolymers. Photopatterned microchannel with a minimum resolution of 10 μm was achieved. After equipped with a conventional online electrochemical detector, the device enabled baseline separation of bovine serum albumin, lysozyme (Lys), and cytochrome c (Cyt-c) in 53 s under a voltage of 200 V. Compared with a traditional polydimethylsiloxane MCE made by soft lithography, the PEG MCE made by the sandwich photolithography not only eliminated the need of a master mold and the additional modification process of the microchannel but also showed excellent anti-protein-fouling properties for protein separation.

  13. 250 °C-Operated sandwich-structured all-SiC power module

    NASA Astrophysics Data System (ADS)

    Kato, Fumiki; Simanjorang, Rejeki; Lang, Fengqun; Nakagawa, Hiroshi; Yamaguchi, Hiroshi; Sato, Hiroshi

    2015-04-01

    The operation of a sandwich structured all-SiC power module is demonstrated at 250 °C. The power module was designed by considering two thermal deformation issues. Thermally induced bending of the SiN-AMC substrates is reduced by introducing symmetrical Cu wiring patterns on both sides of the SiN ceramic plate. The concentration of stress located in the gate joint material is drastically reduced by introducing a trench structure in the Cu wiring layer of the gate interconnection. A double pulse test at a high temperature is carried out. At 250 °C, the all-SiC sandwich-structured power module was successfully operate at 600 V and 15 A. The maximum switching transient speed (dV/dt) of turn-on and turn-off are observed 10.7 and 12.1 V/ns, respectively.

  14. Polarized white light from LEDs using remote-phosphor layer sandwiched between reflective polarizer and light-recycling dichroic filter.

    PubMed

    Oh, Ji Hye; Yang, Su Ji; Do, Young Rag

    2013-09-01

    This study introduces an efficient polarized, white phosphor-converted, light-emitting diode (pc-LED) using a remote phosphor film sandwiched between a reflective polarizer film (RPF) and a short-wavelength pass dichroic filter (SPDF). The on-axis brightness of polarized white light emission of a RPF/SPDF-sandwiched phosphor film over a blue LED, showed greater recovery than that of a conventional unpolarized remote phosphor film over blue LED, due to the recycling effect of yellow light from an SPDF. The relative luminous efficacy of an RPF/SPDF-sandwiched phosphor film was made 1.40 times better by adding an SPDF on the backside of an RPF-capped phosphor film. A polarization ratio of 0.84 was demonstrated for a white LED with an RPF/SPDF-sandwiched phosphor film, in good agreement with the measured results from the RPF-only sample.

  15. Analysis of an Aircraft Honeycomb Sandwich Panel with Circular Face Sheet/Core Disbond Subjected to Ground-Air Pressurization

    NASA Technical Reports Server (NTRS)

    Rinker, Martin; Krueger, Ronald; Ratcliffe, James

    2013-01-01

    The ground-air pressurization of lightweight honeycomb sandwich structures caused by alternating pressure differences between the enclosed air within the honeycomb core and the ambient environment is a well-known and controllable loading condition of aerospace structures. However, initial face sheet/core disbonds intensify the face sheet peeling effect of the internal pressure load significantly and can decrease the reliability of the sandwich structure drastically. Within this paper, a numerical parameter study was carried out to investigate the criticality of initial disbonds in honeycomb sandwich structures under ground-air pressurization. A fracture mechanics approach was used to evaluate the loading at the disbond front. In this case, the strain energy release rate was computed via the Virtual Crack Closure Technique. Special attention was paid to the pressure-deformation coupling which can decrease the pressure load within the disbonded sandwich section significantly when the structure is highly deformed.

  16. Compression After Impact on Honeycomb Core Sandwich Panels with Thin Facesheets, Part 2: Analysis

    NASA Technical Reports Server (NTRS)

    Mcquigg, Thomas D.; Kapania, Rakesh K.; Scotti, Stephen J.; Walker, Sandra P.

    2012-01-01

    A two part research study has been completed on the topic of compression after impact (CAI) of thin facesheet honeycomb core sandwich panels. The research has focused on both experiments and analysis in an effort to establish and validate a new understanding of the damage tolerance of these materials. Part 2, the subject of the current paper, is focused on the analysis, which corresponds to the CAI testings described in Part 1. Of interest, are sandwich panels, with aerospace applications, which consist of very thin, woven S2-fiberglass (with MTM45-1 epoxy) facesheets adhered to a Nomex honeycomb core. Two sets of materials, which were identical with the exception of the density of the honeycomb core, were tested in Part 1. The results highlighted the need for analysis methods which taken into account multiple failure modes. A finite element model (FEM) is developed here, in Part 2. A commercial implementation of the Multicontinuum Failure Theory (MCT) for progressive failure analysis (PFA) in composite laminates, Helius:MCT, is included in this model. The inclusion of PFA in the present model provided a new, unique ability to account for multiple failure modes. In addition, significant impact damage detail is included in the model. A sensitivity study, used to assess the effect of each damage parameter on overall analysis results, is included in an appendix. Analysis results are compared to the experimental results for each of the 32 CAI sandwich panel specimens tested to failure. The failure of each specimen is predicted using the high-fidelity, physicsbased analysis model developed here, and the results highlight key improvements in the understanding of honeycomb core sandwich panel CAI failure. Finally, a parametric study highlights the strength benefits compared to mass penalty for various core densities.

  17. Aptamer-conjugated silver nanoparticles for electrochemical dual-aptamer-based sandwich detection of staphylococcus aureus.

    PubMed

    Abbaspour, Abdolkarim; Norouz-Sarvestani, Fatemeh; Noori, Abolhassan; Soltani, Noushin

    2015-06-15

    Staphylococcus aureus (S. aureus) is one of the most important human pathogens and causes numerous illnesses. In this study, we report a sensitive and highly selective dual-aptamer-based sandwich immunosensor for the detection of S. aureus. In this bioassay system, a biotinylated primary anti-S.aureus aptamer was immobilized on streptavidin coated magnetic beads (MB), which serves as a capture probe. A secondary anti-S.aureus aptamer was conjugated to silver nanoparticles (Apt-AgNP) that sensitively reports the detection of the target. In the presence of target bacterium, an Apt/S.aureus/apt-AgNP sandwich complex is formed on the MB surface and the electrochemical signal of AgNPs followed through anodic stripping voltammetry. The proposed sandwich assay benefits from advantageous of a sandwich assay for increased specificity, MB as carriers of affinity ligands for solution-phase recognition and fast magnetic separation, AgNPs for signal amplification, and an electrochemical stripping voltammetry read-out as a simple and sensitive detection. The electrochemical immunosensor shows an extended dynamic range from 10 to 1×10(6) cfu/mL with a low detection limit of 1.0 cfu/mL (S/N=3). Furthermore, the possible interference of other analog bacteria was studied. To assess the general applicability of this sensor, we investigated the quantification of S. aureus in real water samples. The results were compared to the experimental results obtained from a plate counting method, which demonstrated an acceptable consistency.

  18. "Half-sandwich" Yb(III) single-ion magnets with metallacrowns.

    PubMed

    Li, Quan-Wen; Liu, Jun-Liang; Jia, Jian-Hua; Chen, Yan-Cong; Liu, Jiang; Wang, Long-Fei; Tong, Ming-Liang

    2015-06-28

    The first "half-sandwich" Yb(III) single-ion magnets (SIMs) based on [12-MCZn(ii)-4] are reported, in which the central ytterbium ion is coordinated by YbO8 geometry in D4d symmetry. The anisotropic barrier is extracted from the analysis of static, dynamic magnetism and emission spectrum offering an insight into the magneto-optical correlation.

  19. Development and fabrication of an autoclave molded PES/Quartz sandwich radome

    NASA Astrophysics Data System (ADS)

    Stanton, Leonard E.; Levin, Stephen D.

    1993-04-01

    A cohesively bonded, thermoplastic composite sandwich radome for a leading edge supersonic aircraft has been built using autoclave processing with PES/Quartz prepreg and a PES coated honeycomb core. Processes were developed for solvent removal, thermoplastic laminate consolidation, surface etching to improve adhesion, honeycomb coating and forming, and ultrasound testing of bond integrity. Environmental testing was also conducted to verify the structural integrity of the radome for its intended application.

  20. Governing equations for vibrating constrained-layer damping sandwich plates and beams.

    NASA Technical Reports Server (NTRS)

    Yan, M.-J.; Dowell, E. H.

    1972-01-01

    A simple differential equation is derived to describe constrained-layer damping in nonsymmetric sandwich plates and beams composed of isotropic and homogeneous layers. The natural boundary conditions related to this equation are determined and some typical numerical results obtained by this equation are given. The equation is valid within the linear theories of elasticity and viscoelasticity in the absence of any constraints on thicknesses, positions, symmetries, and densities of the layers.

  1. Sound Transmission Loss Through a Corrugated-Core Sandwich Panel with Integrated Acoustic Resonators

    NASA Technical Reports Server (NTRS)

    Schiller, Noah H.; Allen, Albert R.; Zalewski, Bart F; Beck, Benjamin S.

    2014-01-01

    The goal of this study is to better understand the effect of structurally integrated resonators on the transmission loss of a sandwich panel. The sandwich panel has facesheets over a corrugated core, which creates long aligned chambers that run parallel to the facesheets. When ports are introduced through the facesheet, the long chambers within the core can be used as low-frequency acoustic resonators. By integrating the resonators within the structure they contribute to the static load bearing capability of the panel while also attenuating noise. An analytical model of a panel with embedded resonators is derived and compared with numerical simulations. Predictions show that acoustic resonators can significantly improve the transmission loss of the sandwich panel around the natural frequency of the resonators. In one configuration with 0.813 m long internal chambers, the diffuse field transmission loss is improved by more than 22 dB around 104 Hz. The benefit is achieved with no added mass or volume relative to the baseline structure. The embedded resonators are effective because they radiate sound out-of-phase with the structure. This results in destructive interference, which leads to less transmitted sound power.

  2. Aptamers-based sandwich assay for silver-enhanced fluorescence multiplex detection.

    PubMed

    Wang, Ying; Li, Hui; Xu, Danke

    2016-01-28

    In this work, aptamers-modified silver nanoparticles (AgNPs) were prepared as capture substrate, and fluorescent dyes-modified aptamers were synthesized as detection probes. The sandwich assay was based on dual aptamers, which was aimed to accomplish the highly sensitive detection of single protein and multiplex detection of proteins on one-spot. We found that aptamers-modified AgNPs based microarray was much superior to the aptamer based microarray in fluorescence detection of proteins. The result shows that the detection limit of the sandwich assay using AgNPs probes for thrombin or platelet-derived growth factor-BB (PDGF-BB) is 80 or 8 times lower than that of aptamers used directly. For multiplex detection of proteins, the detection limit was 625 pM for PDGF-BB and 21 pM for thrombin respectively. The sandwich assay based on dual aptamers and AgNPs was sensitive and specific. PMID:26755149

  3. Experimental investigation of graphite/polyimide sandwich panels in edgewise compression

    NASA Technical Reports Server (NTRS)

    Camarda, C. J.

    1980-01-01

    The local and general buckling behavior of graphite/polyimide sandwich panels simply supported along all four edges and loaded in uniaxial edgewise compression was investigated. Material properties of adhesive and facings were determined from flatwise tension and sandwich beam flexure tests. Tensile and compressive material properties of the facings were determined at 116, R.T., and 589 K (-250, R.T., and 600 F) using the sandwich beam flexure test method. Results indicate that Gr/PI is a usable structural material for short term use at temperatures as high as 589 K (600 F). Buckling specimens were 30.5 X 33.0 cm (12 x 13 in.), had quasi-isotropic symmetric facings and a glass/polyimide honeycomb core. Core thicknesses varied and three panels of each thickness were tested in edgewise compression at room temperature to investigate failure modes and corresponding buckling formulas. Specimens 0.635 cm (0.25 in.) thick failed by overall buckling at loads close to the analytically predicted buckling load; all other panels failed by face wrinkling. Results of the winkling tests indicate that several buckling formulas were unconservative and therefore not suitable for design purposes; recommended wrinkling equations are presented.

  4. Development of a sandwich ELISA for quantifying hepcidin in Rainbow trout.

    PubMed

    Santana, Paula A; Álvarez, Claudio A; Guzmán, Fanny; Mercado, Luis

    2013-09-01

    One of the most widespread antimicrobial peptides (AMPs) in fish is the hepcidins, which have potent, broad-spectrum activity against viruses, bacteria, fungi, and parasites. Moreover, they play the role of central regulation of iron metabolism and their expression is over-regulated by bacterial and viral infections, inflammation and vaccination. Quantification of their expression is an important factor in understanding their function. We therefore generated two polyclonal antibodies using synthetic peptides in order to measure hepcidin expression via sandwich ELISA. The specificity of both antibodies was confirmed by identifying an absence of cross-reactivity with other peptides that have similar pI and with the detection by Western blot of only one 9.6 kDa immunoreactive band corresponding to the hepcidin prepropeptide. The sensitivity of the sandwich ELISA was in the order of 0.005 ng/μL of hepcidin, which allowed analysis of the presence of the peptide and its variation in different tissues of Oncorhynchus mykiss. With the sandwich ELISA it could be seen that hepcidin expression in rainbow trout challenged with Aeromonas salmonicida was increased twofold over the untreated fish in head kidney samples, in correlation with the increase in the observed transcriptional level in the head kidney cells. These results provide the first evidence for quantifying the presence of active hepcidin and may be a useful indicator of disease susceptibility, providing a new, sensitive tool for rapid screening of population health. PMID:23791861

  5. Process Factors and Edgewise Compressive Properties of Scarf-repaired Honeycomb Sandwich Structures

    NASA Astrophysics Data System (ADS)

    Liu, Sui; Guan, Zhidong; Guo, Xia; Sun, Kai; Kong, Jiaoyue; Yan, Dongxiu

    2014-10-01

    Bonded repairs were conducted on flat and edge-closed composite sandwich panels that had undergone different levels of initial damage, and edgewise compression behaviors of repaired panel were tested. Experimental results indicate that these repair techniques can restore the compression performance of damaged panels effectively. The repaired specimens recovered an average of over 83 % of their strength. A k-sample Anderson-Darling test was used to analyze the influence of various parameters, including curing temperature, curing pressure, and repair configurations. After a thorough comparison, it was concluded that a high-temperature, high-pressure treatment can improve the mechanical performance of repaired panels, but the improvement is closely related to the structural complexity of the repaired region. A double-side repair scheme could be used to prevent the degradation of mechanical performance caused by the additional bending moment. The conclusions drawn in the present study provide further insight into the mechanical performance of repaired sandwich panels under edgewise compressive loads. These data facilitate the improved design methodology on bonded repair of composite sandwich structures.

  6. Development of monoclonal antibody-based sandwich ELISA for detection of dextran.

    PubMed

    Wang, Sheng-Yu; Li, Zhe; Wang, Xian-Jiang; Lv, Sha; Yang, Yun; Zeng, Lian-Qiang; Luo, Fang-Hong; Yan, Jiang-Hua; Liang, Da-Feng

    2014-10-01

    Dextran as anti-nutritional factor is usually a result of bacteria activity and has associated serial problems during the process stream in the sugar industry and in medical therapy. A sensitive method is expected to detect dextran quantitatively. Here we generated four monoclonal antibodies (MAbs) against dextran using dextran T40 conjugated with bovine serum albumin (BSA) as immunogen in our lab following hybridoma protocol. Through pairwise, an MAb named D24 was determined to be conjugated with horseradish peroxidase (HRP) and was used in the establishment of a sensitive sandwich enzyme-linked immunosorbent assay (ELISA) method for determination of dextran, in which MAb D9 was chosen as a capture antibody. The detection limit and working scope of the developed sandwich ELISA method were 3.9 ng/mL and 7.8-500 ng/mL with a correlation coefficient of 0.9909. In addition, the cross-reaction assay demonstrated that the method possessed high specificity with no significant cross-reaction with dextran-related substances, and the recovery rate ranged from 96.35 to 102.00%, with coefficient of variation ranging from 1.58 to 6.94%. These results indicated that we developed a detection system of MAb-based sandwich ELISA to measure dextran and this system should be a potential tool to determine dextran levels.

  7. Quantitation of rat lacrimal secretion: a novel sandwich ELISA with high sensitivity.

    PubMed

    Sanghi, S; Kumar, R; Walton, S; Laurie, G W

    2000-05-01

    Modulation of lacrimal acinar cell tear secretion may involve multiple factors acting both in subtle and pronounced ways. Functional screens of recombinant protein products arising from gene array technologies, or protein fractions derived from lacrimal conditioned media or extracellular matrix, will require a highly sensitive assay capable of monitoring tear protein secretion by small replicate cultures. To improve significantly on current methods, a rat- and mouse-specific sandwich ELISA was developed. For this purpose, chickens and rabbits were immunized with serum-free secretion media from carbachol and VIP-stimulated rat lacrimal acinar cell cultures. Immune sera were characterized by ELISA, Western blotting and immunohistochemistry, and subsequently optimized for use in a sandwich ELISA. Both antisera detected a wide range of different rat tear proteins, and immunostained only the secretory granule-rich juxtalumenal region in sections of rat lacrimal gland. Chicken, but not rabbit, antiserum cross-reacted with rabbit and human tears. In sandwich ELISA, capture with purified chicken immunoglobulin fraction and detection with rabbit antiserum detected as little as 1 ng ml-1 tear protein in 10,000-fold diluted rat secretion medium--a level of sensitivity 8000 times greater than the rat tear peroxidase assay. Such specificity and sensitivity greatly reduce the quantity of media needed for assay, and makes feasible functional screens for scarce factors that may influence lacrimal secretory processes, and in turn possibly play a role in human lacrimal insufficiency syndromes.

  8. Experimental Tests on the Composite Foam Sandwich Pipes Subjected to Axial Load

    NASA Astrophysics Data System (ADS)

    Li, Feng; Zhao, QiLin; Xu, Kang; Zhang, DongDong

    2015-12-01

    Compared to the composite thin-walled tube, the composite foam sandwich pipe has better local flexural rigidity, which can take full advantage of the high strength of composite materials. In this paper, a series of composite foam sandwich pipes with different parameters were designed and manufactured using the prefabricated polyurethane foam core-skin co-curing molding technique with E-glass fabric prepreg. The corresponding axial-load compressive tests were conducted to investigate the influence factors that experimentally determine the axial compressive performances of the tubes. In the tests, the detailed failure process and the corresponding load-displacement characteristics were obtained; the influence rules of the foam core density, surface layer thickness, fiber ply combination and end restraint on the failure modes and ultimate bearing capacity were studied. Results indicated that: (1) the fiber ply combination, surface layer thickness and end restraint have a great influence on the ultimate load bearing capacity; (2) a reasonable fiber ply combination and reliable interfacial adhesion not only optimize the strength but also transform the failure mode from brittle failure to ductile failure, which is vital to the fully utilization of the composite strength of these composite foam sandwich pipes.

  9. Interaction of sodium and potassium ions with sandwiched cytosine-, guanine-, thymine-, and uracil-base tetrads.

    PubMed

    Meyer, Michael; Hocquet, Alexandre; Sühnel, Jürgen

    2005-03-01

    Nucleic acid tetraplexes and lipophilic self-assembling G-quadruplexes contain stacked base tetrads with intercalated metal ions as basic building blocks. Thus far, quantum-chemical studies have been used to explore the geometric and energetic properties of base tetrads with and without metal ions. Recently, for the first time, work on a sandwiched G-tetrad complex has been studied. We report here results of a systematic B3LYP density functional study on sandwiched G-, C-, U-, and T-tetrads with Na+ and K+ at different symmetries that substantially extend the recent work. The results include detailed information on total energies as well as on metal ion tetrad and base-base interaction energies. The geometrical parameters of the sandwiched metal ion complexes are compared to both experimental structures and to calculated geometries of complexes of single tetrads with metal ions. A microsolvation model explains the ion selectivity preference of K+ over Na+ in a qualitative sense. PMID:15648098

  10. Droplets on inclined super hydrophobic substrates: between ``sandwich,'' free sliding and jumping

    NASA Astrophysics Data System (ADS)

    Martinez Mercado, Julian; Ohl, Claus-Dieter

    2015-11-01

    We seek to understand the effect of confinement on the transport properties of droplets on super hydrophobic surfaces. In a straightforward experiment, the droplet slides down an incline while being sandwiched between two plates. The dynamics is captured from two views to reveal centre of mass motion and the three dimensional motion. The range of Weber and Reynolds number based on the droplet radius are 0.6-4 and 260-680, respectively. The capillary number is of order 10-3. Three geometries are studied, confined between two plates, droplet release, and droplet capture. For the latter two geometries, some part of the incline consists of lower and upper plates. The experimental observations are that the acceleration of a ``sandwiched'' droplet is considerably reduced to a free sliding one. Droplets being released jump off the substrate converting considerable amount of the surface energy into potential energy. Droplet capture obeys a limit kinetic energy, below that, they are reflected from the constriction. We hope to present detail of the flow within the sandwiched droplet by the time of presentation. This work was supported by the Singapore National Research Foundations Competitive Research Program funding (NRF-CRP9-2011-04).

  11. Design of Fiber Reinforced Foam Sandwich Panels for Large Ares V Structural Applications

    NASA Technical Reports Server (NTRS)

    Bednarcyk, Brett A.; Arnold, Steven M.; Hopkins, Dale A.

    2010-01-01

    The preliminary design of three major structural components within NASA's Ares V heavy lift vehicle using a novel fiber reinforced foam composite sandwich panel concept is presented. The Ares V payload shroud, interstage, and core intertank are designed for minimum mass using this panel concept, which consists of integral composite webs separated by structural foam between two composite facesheets. The HyperSizer structural sizing software, in conjunction with NASTRAN finite element analyses, is used. However, since HyperSizer does not currently include a panel concept for fiber reinforced foam, the sizing was performed using two separate approaches. In the first, the panel core is treated as an effective (homogenized) material, whose properties are provided by the vendor. In the second approach, the panel is treated as a blade stiffened sandwich panel, with the mass of the foam added after completion of the panel sizing. Details of the sizing for each of the three Ares V components are given, and it is demonstrated that the two panel sizing approaches are in reasonable agreement for thinner panel designs, but as the panel thickness increases, the blade stiffened sandwich panel approach yields heavier panel designs. This is due to the effects of local buckling, which are not considered in the effective core property approach.

  12. A novel sandwich differential capacitive accelerometer with symmetrical double-sided serpentine beam-mass structure

    NASA Astrophysics Data System (ADS)

    Xiao, D. B.; Li, Q. S.; Hou, Z. Q.; Wang, X. H.; Chen, Z. H.; Xia, D. W.; Wu, X. Z.

    2016-02-01

    This paper presents a novel differential capacitive silicon micro-accelerometer with symmetrical double-sided serpentine beam-mass sensing structure and glass-silicon-glass sandwich structure. The symmetrical double-sided serpentine beam-mass sensing structure is fabricated with a novel pre-buried mask fabrication technology, which is convenient for manufacturing multi-layer sensors. The glass-silicon-glass sandwich structure is realized by a double anodic bonding process. To solve the problem of the difficulty of leading out signals from the top and bottom layer simultaneously in the sandwich sensors, a silicon pillar structure is designed that is inherently simple and low-cost. The prototype is fabricated and tested. It has low noise performance (the peak to peak value is 40 μg) and μg-level Allan deviation of bias (2.2 μg in 1 h), experimentally demonstrating the effectiveness of the design and the novel fabrication technology.

  13. Sandwich hybridisation assay for quantitative detection of yeast RNAs in crude cell lysates

    PubMed Central

    Rautio, Jari; Barken, Kim Bundvig; Lahdenperä, Juhani; Breitenstein, Antje; Molin, Søren; Neubauer, Peter

    2003-01-01

    Background A rapid microtiter plate based sandwich hybridization assay was developed for detection and quantification of single RNA species using magnetic beads. Following solution hybridization target RNA molecules were collected by biotin-streptavidin affinity binding and detected by fluorescence signal generated by alkaline phosphatase. The 18S rRNA and SUC2 mRNA of Saccharomyces cerevisiae were used as model RNA target molecules. Results The sensitivity of the assay was approximately 1.2 × 109 (2 fmol) molecules of target RNA. The developed method was feasible with crude cell lysates of S. cerevisiae carlsbergensis and was evaluated by measuring the levels of 18S rRNA during cell growth and SUC2 mRNA under repressive and inductive conditions. The 18S rRNA expression level followed the changes in the specific growth rate. SUC2 mRNA levels were in good correlation with the measured invertase enzyme activities. Conclusions The here presented sandwich hybridisation method was succefully applied for monitoring the amounts of ribosomal RNA and mRNA with high expression level in shake flask cultivation conditions. Sandwich hybridisation method offers a fast and convenient tool for following single key RNA species of interest in the production conditions. PMID:12780940

  14. Hypervelocity Impact Performance of Open Cell Foam Core Sandwich Panel Structures

    NASA Technical Reports Server (NTRS)

    Ryan, S.; Ordonez, E.; Christiansen, E. L.; Lear, D. M.

    2010-01-01

    Open cell metallic foam core sandwich panel structures are of interest for application in spacecraft micrometeoroid and orbital debris shields due to their novel form and advantageous structural and thermal performance. Repeated shocking as a result of secondary impacts upon individual foam ligaments during the penetration process acts to raise the thermal state of impacting projectiles ; resulting in fragmentation, melting, and vaporization at lower velocities than with traditional shielding configurations (e.g. Whipple shield). In order to characterize the protective capability of these structures, an extensive experimental campaign was performed by the Johnson Space Center Hypervelocity Impact Technology Facility, the results of which are reported in this paper. Although not capable of competing against the protection levels achievable with leading heavy shields in use on modern high-risk vehicles (i.e. International Space Station modules), metallic foam core sandwich panels are shown to provide a substantial improvement over comparable structural panels and traditional low weight shielding alternatives such as honeycomb sandwich panels and metallic Whipple shields. A ballistic limit equation, generalized in terms of panel geometry, is derived and presented in a form suitable for application in risk assessment codes.

  15. Efficient Design and Analysis of Lightweight Reinforced Core Sandwich and PRSEUS Structures

    NASA Technical Reports Server (NTRS)

    Bednarcyk, Brett A.; Yarrington, Phillip W.; Lucking, Ryan C.; Collier, Craig S.; Ainsworth, James J.; Toubia, Elias A.

    2012-01-01

    Design, analysis, and sizing methods for two novel structural panel concepts have been developed and incorporated into the HyperSizer Structural Sizing Software. Reinforced Core Sandwich (RCS) panels consist of a foam core with reinforcing composite webs connecting composite facesheets. Boeing s Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) panels use a pultruded unidirectional composite rod to provide axial stiffness along with integrated transverse frames and stitching. Both of these structural concepts are ovencured and have shown great promise applications in lightweight structures, but have suffered from the lack of efficient sizing capabilities similar to those that exist for honeycomb sandwich, foam sandwich, hat stiffened, and other, more traditional concepts. Now, with accurate design methods for RCS and PRSEUS panels available in HyperSizer, these concepts can be traded and used in designs as is done with the more traditional structural concepts. The methods developed to enable sizing of RCS and PRSEUS are outlined, as are results showing the validity and utility of the methods. Applications include several large NASA heavy lift launch vehicle structures.

  16. Sizing Single Cantilever Beam Specimens for Characterizing Facesheet/Core Peel Debonding in Sandwich Structure

    NASA Technical Reports Server (NTRS)

    Ratcliffe, James G.

    2010-01-01

    This technical publication details part of an effort focused on the development of a standardized facesheet/core peel debonding test procedure. The purpose of the test is to characterize facesheet/core peel in sandwich structure, accomplished through the measurement of the critical strain energy release rate associated with the debonding process. Following an examination of previously developed tests and a recent evaluation of a selection of these methods, a single cantilever beam (SCB) specimen was identified as being a promising candidate for establishing such a standardized test procedure. The objective of the work described here was to begin development of a protocol for conducting a SCB test that will render the procedure suitable for standardization. To this end, a sizing methodology was developed to ensure appropriate SCB specimen dimensions are selected for a given sandwich system. Application of this method to actual sandwich systems yielded SCB specimen dimensions that would be practical for use. This study resulted in the development of a practical SCB specimen sizing method, which should be well-suited for incorporation into a standardized testing protocol.

  17. Failure Maps for Rectangular 17-4PH Stainless Steel Sandwiched Foam Panels

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Ghosn, L. J.

    2007-01-01

    A new and innovative concept is proposed for designing lightweight fan blades for aircraft engines using commercially available 17-4PH precipitation hardened stainless steel. Rotating fan blades in aircraft engines experience a complex loading state consisting of combinations of centrifugal, distributed pressure and torsional loads. Theoretical failure plastic collapse maps, showing plots of the foam relative density versus face sheet thickness, t, normalized by the fan blade span length, L, have been generated for rectangular 17-4PH sandwiched foam panels under these three loading modes assuming three failure plastic collapse modes. These maps show that the 17-4PH sandwiched foam panels can fail by either the yielding of the face sheets, yielding of the foam core or wrinkling of the face sheets depending on foam relative density, the magnitude of t/L and the loading mode. The design envelop of a generic fan blade is superimposed on the maps to provide valuable insights on the probable failure modes in a sandwiched foam fan blade.

  18. A sandwich-cultured rat hepatocyte system with increased metabolic competence evaluated by gene expression profiling.

    PubMed

    Kienhuis, A S; Wortelboer, H M; Maas, W J; van Herwijnen, M; Kleinjans, J C S; van Delft, J H M; Stierum, R H

    2007-08-01

    A rapid decline of cytochrome P450 (CYP450) enzyme activities remains a drawback of rat hepatocyte-based in vitro cultures. Consequently, judgment of the toxic potential of compounds that need bioactivation by CYP450s may not be adequate using this model. In the present study, an improved hepatocyte-based in vitro system was developed with special focus on metabolic competence. Therefore, a mixture of CYP450 inducers, phenobarbital, dexamethasone and beta-naphthoflavone, was added to culture medium of sandwich-cultured rat hepatocytes. The resulting modified model was evaluated by comparing its genome-wide expression profiles with liver and a standard model without the inducer mixture. Metabolic capacity for CYP450 enzymes showed that the modified model resembled more closely the in vivo situation. Gene expression results revealed large differences between in vivo and both in vitro models. The slight differences between the two sandwich models were predominantly represented by gene expression changes in CYP450s. Importantly, in the modified model, expression ratios of the phase I and the majority of phase II genes more closely resembled liver in vivo. The CYP450 enzyme activities corresponded with gene expression data. In conclusion, for toxicological applications using sandwich-cultured hepatocytes, the modified model may be preferred. PMID:17336492

  19. On the Rigidity in Bending of a Sandwich with Thick CFRP Facings and Thin Soft Core

    NASA Astrophysics Data System (ADS)

    Caprino, G.; Iaccarino, P.; Langella, A.; Lamboglia, A.

    2009-06-01

    Flexure tests in three-point bending were performed in the elastic domain on sandwich specimens whose facings were made of T800H/3900-2 laminates, and the core by a soft rubbery layer. The contribution of the shear and flexural deformations to the overall deflection was varied by varying the slenderness ratio. The rigidities yielded by the load-displacement curve were corrected for the indentation occurring at the points of load introduction, using an experimentally determined calibration curve. Due to the thinness of the sandwich, indentation negligibly affected the precision of the results, with the apparent rigidities differing from the actual ones by less than 2%. By an analytical formula previously developed for sandwich structures, a prediction of the rigidities in flexure was attempted, adopting elastic constants available in the literature. The correlation with the data points was poor, with the theoretical results largely overestimating the actual rigidities. However, the reliability of the closed-form formula was supported by finite element analysis, carried out modelling the facings by 2D plate elements, and the core by 3D brick elements. Through the formula, the core shear modulus was individuated as responsible of the discrepancies observed. Assuming a suitable value for this parameter, both the analytic solution and the finite element models were able to match with accuracy the rigidities measured.

  20. A thin-walled polydimethylsiloxane bioreactor for high-density hepatocyte sandwich culture.

    PubMed

    Tan, Guo-Dong Sean; Toh, Guoyang William; Birgersson, Erik; Robens, Jeffrey; van Noort, Danny; Leo, Hwa Liang

    2013-06-01

    In vitro drug testing requires long-term maintenance of hepatocyte liver specific functions. Hepatocytes cultured at a higher seeding density in a sandwich configuration exhibit an increased level of liver specific functions when compared to low density cultures due to the better cell to cell contacts that promote long term maintenance of polarity and liver specific functions. However, culturing hepatocytes at high seeding densities in a standard 24-well plate poses problems in terms of the mass transport of nutrients and oxygen to the cells. In view of this drawback, we have developed a polydimethylsiloxane (PDMS) bioreactor that was able to maintain the long-term liver specific functions of a hepatocyte sandwich culture at a high seeding density. The bioreactor was fabricated with PDMS, an oxygen permeable material, which allowed direct oxygenation and perfusion to take place simultaneously. The mass transport of oxygen and the level of shear stress acting on the cells were analyzed by computational fluid dynamics (CFD). The combination of both direct oxygenation and perfusion has a synergistic effect on the liver specific function of a high density hepatocyte sandwich culture over a period of 9 days. PMID:23280535

  1. Finite element based stability-constrained weight minimization of sandwich composite ducts for airship applications

    NASA Astrophysics Data System (ADS)

    Khode, Urmi B.

    High Altitude Long Endurance (HALE) airships are platform of interest due to their persistent observation and persistent communication capabilities. A novel HALE airship design configuration incorporates a composite sandwich propulsive hull duct between the front and the back of the hull for significant drag reduction via blown wake effects. The sandwich composite shell duct is subjected to hull pressure on its outer walls and flow suction on its inner walls which result in in-plane wall compressive stress, which may cause duct buckling. An approach based upon finite element stability analysis combined with a ply layup and foam thickness determination weight minimization search algorithm is utilized. Its goal is to achieve an optimized solution for the configuration of the sandwich composite as a solution to a constrained minimum weight design problem, for which the shell duct remains stable with a prescribed margin of safety under prescribed loading. The stability analysis methodology is first verified by comparing published analytical results for a number of simple cylindrical shell configurations with FEM counterpart solutions obtained using the commercially available code ABAQUS. Results show that the approach is effective in identifying minimum weight composite duct configurations for a number of representative combinations of duct geometry, composite material and foam properties, and propulsive duct applied pressure loading.

  2. In-situ observation of nucleated polymer crystallization in polyoxymethylene sandwich composites

    NASA Astrophysics Data System (ADS)

    Slouf, Miroslav; Krejcikova, Sabina; Vackova, Tatana; Kratochvil, Jaroslav; Novak, Libor

    2015-03-01

    We introduce a dynamic sandwich method, which can be used for in-situ observation and quantification of polymer crystallization nucleated by micro/nanoparticles. The method was applied on polyoxymethylene (POM) composites with three nucleating agents: talc micropowder (POM/mTalc), chalk nanopowder (POM/nChalk) and titanate nanotubes (POM/TiNT). The nucleating agents were deposited between polymer films, the resulting sandwich samples were consolidated by thermal treatment, and their microtomed cross-sections were observed during isothermal crystallization by polarized light microscopy. As the intensity of polarized light was shown to be proportional to the relative crystallinity, the PLM results could be fitted to Avrami equation and the nucleating activity of all investigated particles could be quantified by means of Avrami parameters (n, k). The crystallization half-times increased reproducibly in the following order: POM/nChalk < POM/mTalc < POM/TiNT ~ POM. For strong nucleating agents (mTalc, nChalk), the crystallization kinetics corresponded to spontaneous crystallization starting from central nucleating layer, which was verified by computer simulations. The results were also confirmed by DSC. We concluded that the sandwich method is an efficient microscopic technique for detailed evaluation of nucleating activity of arbitrary micro/nanoparticles in polymer systems.

  3. Non-destructive inspection of drilled holes in reinforced honeycomb sandwich panels using active thermography

    NASA Astrophysics Data System (ADS)

    Usamentiaga, R.; Venegas, P.; Guerediaga, J.; Vega, L.; López, I.

    2012-11-01

    The aerospace industry is in constant need of ever-more efficient inspection methods for quality control. Product inspection is also essential to maintain the safe operation of aircraft components designed to perform for decades. This paper proposes a method for non-destructive inspection of drilled holes in reinforced honeycomb sandwich panels. Honeycomb sandwich panels are extensively employed in the aerospace industry due to their high strength and stiffness to weight ratios. In order to attach additional structures to them, panels are reinforced by filling honeycomb cells and drilling holes into the reinforced areas. The proposed procedure is designed to detect the position of the holes within the reinforced area and to provide a robust measurement of the distance between each hole and the boundary of the reinforced area. The result is a fast, safe and clean inspection method for drilled holes in reinforced honeycomb sandwich panels that can be used to robustly assess a possible displacement of the hole from the center of the reinforced area, which could have serious consequences. The proposed method is based on active infrared thermography, and uses state of the art methods for infrared image processing, including signal-to-nose ratio enhancement, hole detection and segmentation. Tests and comparison with X-ray inspections indicate that the proposed system meets production needs.

  4. Facile Fabrication of Sandwich Structured WO3 Nanoplate Arrays for Efficient Photoelectrochemical Water Splitting.

    PubMed

    Feng, Xiaoyang; Chen, Yubin; Qin, Zhixiao; Wang, Menglong; Guo, Liejin

    2016-07-20

    Herein, sandwich structured tungsten trioxide (WO3) nanoplate arrays were first synthesized for photoelectrochemical (PEC) water splitting via a facile hydrothermal method followed by an annealing treatment. It was demonstrated that the annealing temperature played an important role in determining the morphology and crystal phase of the WO3 film. Only when the hydrothermally prepared precursor was annealed at 500 °C could the sandwich structured WO3 nanoplates be achieved, probably due to the crystalline phase transition and increased thermal stress during the annealing process. The sandwich structured WO3 photoanode exhibited a photocurrent density of 1.88 mA cm(-2) and an incident photon-to-current conversion efficiency (IPCE) as high as 65% at 400 nm in neutral Na2SO4 solution under AM 1.5G illumination. To our knowledge, this value is one of the best PEC performances for WO3 photoanodes. Meanwhile, simultaneous hydrogen and oxygen evolution was demonstrated for the PEC water splitting. It was concluded that the high PEC performance should be attributed to the large electrochemically active surface area and active monoclinic phase. The present study can provide guidance to develop highly efficient nanostructured photoelectrodes with the favorable morphology.

  5. Sandwich mixer-reactor: influence of the diffusion coefficient and flow rate ratios.

    PubMed

    Abonnenc, Mélanie; Josserand, Jacques; Girault, Hubert H

    2009-02-01

    A sandwich mixer consists of mixing two solutions in a channel, one central laminar flow being sandwiched between two outer flow solutions. The present numerical study considers the convection-diffusion of two reacting species A and B, provided respectively by the two incoming solutions. The simulations show how the diffusion coefficient, flow rate and species concentration ratios influence, via the transversal diffusion length and reaction kinetics, the reaction extent at the end of the sandwich mixer. First, this extent can be enhanced up to 60% if the species with the lowest diffusion coefficient is located in the outer solutions where the flow velocity is small compared to that of the central part (higher residence time). Secondly, decreasing the outer flow rates (to confine the reaction close to the walls) and increasing the local concentration to keep the same flux ratio improve the extent by 300%. Comparison with a bi-lamination passive mixer, with an ideal mixer and an electro-osmotic driven flow mixer is presented. These conclusions are also demonstrated for consecutive reactions, showing an amplification of the effects described above. The results are also presented versus the residence time in the mixer-reactor to show the time window for which the gain is appreciable.

  6. An experimental investigation of sandwich flat panels under low velocity impact

    NASA Astrophysics Data System (ADS)

    Harrington, Timberlyn M.

    1994-12-01

    This study evaluated the failure modes and mechanisms associated with increasing face sheet thickness of flat sandwich panels under low velocity impact. The sandwich panels were fabricated using 1.27 cm thick, 145 kg/cu m (9 lb/cu ft), 3.175 mm (1/8 in.) cell size Nomex honeycomb core, FM 300-2 film adhesive and AS4/3501-6 graphite/epoxy face sheets. The thickness of the core remained 1.27 cm, and the thickness of the adhesive remained 0.25 mm. The thickness of the face sheets varied using the following stacking sequences: (O/90)s, (O/90)2s, (O/90)4s, (O/90)8s, and (O/90)12s. The sandwich panels were subjected to various low velocity impacts using the Dynatup Impact Test Machine. Pulse-Echo C-scans and optical microscopy of panel cross-sections were performed to characterize the damage. The cross-sections indicated that delamination and transverse cracking contribute to internal damage of the face sheets, while crushing, buckling, and crippling contribute to damage of the core. Cracks in the adhesive also contribute to damage in some cases.

  7. Computation of linear transmittance of thermal bridges in precast concrete sandwich panels

    NASA Astrophysics Data System (ADS)

    Luscietti, Davide; Gervasio, Paola; Lezzi, Adriano M.

    2014-11-01

    Precast concrete lightened sandwich panels are widely used building elements. They are made by two concrete wythes separated by a layer of lightweight material: the central layer is inhomogeneous due to the presence of concrete ribs which tie the external wythe and act as thermal bridges. Computation of thermal transmittance of sandwich panels is clearly described in European Standards, but in many cases it requires numerical simulations to determine the linear transmittance ψ associated with lightweight material-concrete interfaces in the inhomogeneous layer. Although simple, these simulations represent a critical issue for many panel manufacturers and they would much rather prefer correlations to compute ψ. In this work we present a correlation based on an artificial neural network (ANN) to estimate linear trasmittauce values for current Italian sandwich panel production. Five input parameters are considered: rib width, lightweight material conductivity, and thickness of the three panel layers. To obtain the data which are necessary to train and test the ANN, a fast and accurate Spectral Element Method is used to solve Laplace equation in the neighborhood of a rib. 5460 ψ values are collected which ensure an accurate network response.

  8. The dynamic mechanical properties study on the sandwich panel of different thickness steel plate-foam aluminum core

    NASA Astrophysics Data System (ADS)

    Chang, Zhongliang; Zou, Guangping; Zhao, Weiling; Xia, Peixiu

    2009-12-01

    The foam aluminum belongs to multi-cell materials, and it has good mechanical performance, such as large deformation capacity and good energy absorption, and usually used as core material of sandwich panel, now it is widely used in automotive, aviation, aerospace and other fields, particularly suitable for various anti-collision structure and buffer structure. In this article, based on an engineering background, the INSTRON4505 electronic universal testing machine and split Hopkinson pressure bar (SHPB) were used for testing the static and dynamic mechanical properties of sandwich panel with different thickness steel plate- foam aluminum core, from the results we can see that the steel plate thickness has big influence on the stress-strain curve of the sandwich panel, and also takes the sandwich panel with 1mm steel panel to study the material strain rate dependence which under different high shock wave stress loaded, the results show that the sandwich panel is strain rate dependence material. And also, in order to get good waveforms in the SHPB experiment, the waveform shaped technique is used in the dynamic experiments, and the study of this paper will good to sandwich panel used in the engineering.

  9. Development of an innovative sandwich common bulkhead for cryogenic upper stage propellant tank

    NASA Astrophysics Data System (ADS)

    Szelinski, B.; Lange, H.; Röttger, C.; Sacher, H.; Weiland, S.; Zell, D.

    2012-12-01

    In the frame of the Future Launcher Preparatory Program (FLPP) investigating advancing technologies for the Next Generation of Launchers (NGL) a number of novel key technologies are presently under development for significantly improving vehicle performance in terms of payload capacity and mission versatility. As a respective ESA guided technology development program, Cryogenic Upper Stage Technologies (CUST) has been launched within FLPP that hosts among others the development of a common bulkhead to separate liquid hydrogen from the liquid oxygen compartment. In this context, MT Aerospace proposed an advanced sandwich design concept which is currently in the development phase reaching for TRL4 under MT Aerospace responsibility. Key components of this sandwich common bulkhead are a specific core material, situated in-between two thin aluminum face sheets, and an innovative thermal decoupling element at the equatorial region. The combination of these elements provides excellent thermal insulation capabilities and mechanical performance at a minimum weight, since mechanical and thermal functions are merged in the same component. This improvement is expressed by substantial performance figures of the proposed concept that include high resistance against reverse pressure, an optimized heat leak and minimized mass, involving the sandwich dome structure and the adjacent interface rings. The development of single sub-technologies, all contributing to maturate the sandwich common bulkhead towards the desired technology readiness level (TRL), is described in the context of the given design constraints as well as technical, functional and programmatic requirements, issued from the stage level. This includes the thermal and mechanical characterization of core materials, manufacturing issues as well as non-destructive testing and the thermal and structural analyses and dimensioning of the complete common bulkhead system. Dedicated TRL assessments in the Ariane 5 Mid

  10. Vibroacoustic flexural properties of symmetric honeycomb sandwich panels with composite faces

    NASA Astrophysics Data System (ADS)

    Guillaumie, Laurent

    2015-05-01

    The vibroacoustic bending properties of honeycomb sandwich panels with composite faces are studied from the wavenumber modulus to the mechanical impedance, passing through the modal density. Numerical results extracted from finite element software computations are compared with analytical results. In both cases, the homogenization method is used to calculate the global properties of the sandwich panel. Since faces are made of composite material, the classical laminate theory serves as reference. With particular conditions used in the application for symmetric panels, the original orthotropic mechanical properties can be reduced simply to three parameters commonly used in vibroacoustic characterizations. These three parameters are the mass per unit area, the bending rigidity and the out-of-plane shear rigidity. They simultaneously govern the wavenumber modulus, the modal frequencies, the modal density and the mechanical impedance. For all of these vibroacoustic characterizations, a special frequency called the transition frequency separates two domains. In the first domain, below the transition frequency or for low frequencies, the orthotropic sandwich panel has a classical isotropic plate behavior. In the second domain, above the transition frequency or for high frequencies, the out-of-plane shear rigidity is very significant and changes the behavior. However, the results discussed are only valid up to a certain frequency which is determined by the thickness and out-of-plane shear stiffness of the honeycomb core, the thickness and the bending stiffness of the laminated face sheets and then the mass per unit area and bending stiffness of the total sandwich structure. All these parameters influence the final choice of model and simplifications presented. Experimental measurements of the bending wavenumber modulus and modal frequencies for our own application were carried out. In the vibroacoustic domain, the critical frequency is also an important frequency. It again

  11. Response surface characterization of impact damage and residual strength degradation in composite sandwich panels

    NASA Astrophysics Data System (ADS)

    Samarah, Issam Khder

    2003-06-01

    The influence of material configuration and impact parameters on the damage tolerance characteristics of sandwich composites comprised of carbon-epoxy woven fabric facesheets and Nomex honeycomb cores was investigated using empirically based response surfaces. A series of carefully selected tests were used to isolate the coupled influence of various combinations of the number of facesheet plies, core density, core thickness, impact energy, impactor diameter, and impact velocity on the damage formation and residual strength degradation due to normal impact. The ranges of selected material parameters were typical of those found in common aircraft applications. The diameter of the planar damage area associated with Through Transmission Ultrasonic C-scan measurements and the peak residual facesheet indentation depth were used to describe the extent of internal and detectable surface damage, respectively. Standard analysis of variance techniques were used to assess the significance of the regression models, individual model terms, and model lack-of-fit. In addition, the inherent variability associated with given types of experimental measurements was evaluated. Response surface estimates of the size of the planar damage region and compressive residual strength as a continuous function of material system and impact parameters correlated reasonably well with experimentally determined values. For a fixed set of impact parameters, regression results suggest that impact damage development and residual strength degradation is highly material and lay-up configuration dependent. Increasing the number of facesheet plies and the thickness of the core material generally resulted in the greatest improvement in the damage tolerance characteristics. An increase in the impact energy can result in a significant decrease in the estimated residual strength, particularly for those sandwich panels with thicker facesheets. The effects of variable impact velocity on damage formation and loss

  12. Construction aggregates

    USGS Publications Warehouse

    Langer, W.H.; Tepordei, V.V.; Bolen, W.P.

    2000-01-01

    Construction aggregates consist primarily of crushed stone and construction sand and gravel. Total estimated production of construction aggregates increased in 1999 by about 2% to 2.39 Gt (2.64 billion st) compared with 1998. This record production level continued an expansion that began in 1992. By commodities, crushed stone production increased 3.3%, while sand and gravel production increased by about 0.5%.

  13. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1994-01-01

    Part of a special section on industrial minerals in 1993. The 1993 production of construction aggregates increased 6.3 percent over the 1992 figure, to reach 2.01 Gt. This represents the highest estimated annual production of combined crushed stone and construction sand and gravel ever recorded in the U.S. The outlook for construction aggregates and the issues facing the industry are discussed.

  14. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1996-01-01

    Part of the Annual Commodities Review 1995. Production of construction aggregates such as crushed stone and construction sand and gravel showed a marginal increase in 1995. Most of the 1995 increases were due to funding for highway construction work. The major areas of concern to the industry included issues relating to wetlands classification and the classification of crystalline silica as a probable human carcinogen. Despite this, an increase in demand is anticipated for 1996.

  15. Constructive Fun.

    ERIC Educational Resources Information Center

    Simanek, Donald E.

    1994-01-01

    Compares and reviews currently available brands of steel construction sets that are useful to physics teachers for building demonstrations, prototypes of mechanisms, robotics, and remote control devices. (ZWH)

  16. Archetypal sandwich-structured CuO for high performance non-enzymatic sensing of glucose

    NASA Astrophysics Data System (ADS)

    Meher, Sumanta Kumar; Rao, G. Ranga

    2013-02-01

    In the quest to enhance the selectivity and sensitivity of novel structured metal oxides for electrochemical non-enzymatic sensing of glucose, we report here a green synthesis of unique sandwich-structured CuO on a large scale under microwave mediated homogeneous precipitation conditions. The physicochemical studies carried out by XRD and BET methods show that the monoclinic CuO formed via thermal decomposition of Cu2(OH)2CO3 possesses monomodal channel-type pores with largely improved surface area (~43 m2 g-1) and pore volume (0.163 cm3 g-1). The fascinating surface morphology and pore structure of CuO is formulated due to homogeneous crystallization and microwave induced self assembly during synthesis. The cyclic voltammetry and chronoamperometry studies show diffusion controlled glucose oxidation at ~0.6 V (vs. Ag/AgCl) with extremely high sensitivity of 5342.8 μA mM-1 cm-2 and respective detection limit and response time of ~1 μM and ~0.7 s, under a wide dynamic concentration range of glucose. The chronoamperometry measurements demonstrate that the sensitivity of CuO to glucose is unaffected by the absence of dissolved oxygen and presence of poisoning chloride ions in the reaction medium, which essentially implies high poison resistance activity of the sandwich-structured CuO. The sandwich-structured CuO also shows insignificant interference/significant selectivity to glucose, even in the presence of high concentrations of other sugars as well as reducing species. In addition, the sandwich-structured CuO shows excellent reproducibility (relative standard deviation of ~2.4% over ten identically fabricated electrodes) and outstanding long term stability (only ~1.3% loss in sensitivity over a period of one month) during non-enzymatic electrochemical sensing of glucose. The unique microstructure and suitable channel-type pore architecture provide structural stability and maximum accessible electroactive surface for unimpeded mobility of glucose as well as the

  17. Analysis of propagation characteristics of flexural wave in honeycomb sandwich panel and design of loudspeaker for radiating inclined sound

    NASA Astrophysics Data System (ADS)

    Fujii, Ayaka; Wakatsuki, Naoto; Mizutani, Koichi

    2015-07-01

    A loudspeaker for an auditory guiding system is proposed. This loudspeaker utilizes inclined sound transformed from a flexural wave in a honeycomb sandwich panel. We focused on the fact that the inclined sound propagates extensively with uniform level and direction. Furthermore, sound can be generated without group delay dispersion because the phase velocity of the flexural wave in the sandwich panel becomes constant with increasing frequency. These characteristics can be useful for an auditory guiding system in public spaces since voice-guiding navigation indicates the right direction regardless of position on a pathway. To design the proposed loudspeaker, the behavior of the sandwich panel is predicted using a theoretical equation in which the honeycomb core is assumed as an orthotropic continuum. We calculated the phase velocity dispersion of the flexural wave in the sandwich panel and compared the results obtained using the equation with those of a simulation based on the finite element method and an experiment in order to confirm the applicability of the theoretical equation. It was confirmed that the phase velocities obtained using the theoretical equation and by the simulation were in good agreement with that obtained experimentally. The obtained results suggest that the behavior of the sandwich panel can be predicted using the parameters of the panel. In addition, we designed an optimized honeycomb sandwich panel for radiating inclined sound by calculating the phase velocity characteristics of various panels that have different parameters of core height and cell size using the theoretical equation. Sound radiation from the optimized panel was simulated and compared with that of a homogeneous plate. It was clear that the variance of the radiation angle with varying frequency of the optimized panel was smaller than that of the homogeneous plate. This characteristic of sound radiation with a uniform angle is useful for indicating the destination direction. On

  18. Droplet-Array (DA) Sandwich Chip: A Versatile Platform for High-Throughput Cell Screening Based on Superhydrophobic-Superhydrophilic Micropatterning.

    PubMed

    Popova, Anna A; Schillo, Sebastian M; Demir, Konstantin; Ueda, Erica; Nesterov-Mueller, A; Levkin, Pavel A

    2015-09-16

    A droplet-array (DA) sandwich chip is a miniaturized platform for cell-based high-throughput screening. It is based on sandwiching of a glass slide with a preprinted library and a superhydrophobic-superhydrophilic pattern, which consists of thousands of simultaneously formed microdroplets containing cells. The DA sandwich chip allows for one-step cell seeding, simultaneous initiation of screening, and 1000 times less reagent consumption than a regular 96-well plate.

  19. A cost-effective sandwich electrochemiluminescence immunosensor for ultrasensitive detection of HIV-1 antibody using magnetic molecularly imprinted polymers as capture probes.

    PubMed

    Zhou, Jing; Gan, Ning; Li, Tianhua; Hu, Futao; Li, Xing; Wang, Lihong; Zheng, Lei

    2014-04-15

    In this report, a rapid and cost-effective sandwich electrochemiluminescence (ECL) immunosensor was constructed for the ultrasensitive detection of human immunodeficiency virus type 1 antibody (anti-HIV-1) using magnetic molecularly imprinted polymers (MMIPs) as capture probes by combining surface and epitope imprinting techniques and antigen conjugated with horseradish peroxidase (HRP-HIV-1) as labels. First, 3-aminobenzeneboronic acid (APBA) was used as the functional monomer and cross-linking reagent, which was polymerized on the surface of silicate-coated magnetic iron oxide nanoparticles (Fe3O4@SiO2 NPs) in the presence of human immunoglobulin G (HIgG), as the template exhibiting the same Fc region but different Fab region to anti-HIV-1 after the addition of the initiator, ammonium persulfate. This process resulted in grafting a hydrophilic molecularly imprinted polymer (MIP) film on the Fe3O4@SiO2 NPs. Thus, MMIPs, which could be reused after eluting the template, were used to recognize and enrich ultra-trace levels of anti-HIV-1. Subsequently, a novel sandwich ECL immunosensor was formed through the immunoreaction between MMIPs conjugated with varied concentrations of anti-HIV-1 and HRP-HIV-1. By the catalysis of HRP immobilized onto HRP-HIV-1 on the ECL system of Luminol-H2O2, a linear response range of the anti-HIV-1 dilution ratio (standard positive serum) was achieved from 1:20,000 to 1:50, with a detection limit of 1:60,000 (S/N=3). The developed method provides a low-cost, simple, and sensitive way for the early diagnosis of HIV infected patients.

  20. A cost-effective sandwich electrochemiluminescence immunosensor for ultrasensitive detection of HIV-1 antibody using magnetic molecularly imprinted polymers as capture probes.

    PubMed

    Zhou, Jing; Gan, Ning; Li, Tianhua; Hu, Futao; Li, Xing; Wang, Lihong; Zheng, Lei

    2014-04-15

    In this report, a rapid and cost-effective sandwich electrochemiluminescence (ECL) immunosensor was constructed for the ultrasensitive detection of human immunodeficiency virus type 1 antibody (anti-HIV-1) using magnetic molecularly imprinted polymers (MMIPs) as capture probes by combining surface and epitope imprinting techniques and antigen conjugated with horseradish peroxidase (HRP-HIV-1) as labels. First, 3-aminobenzeneboronic acid (APBA) was used as the functional monomer and cross-linking reagent, which was polymerized on the surface of silicate-coated magnetic iron oxide nanoparticles (Fe3O4@SiO2 NPs) in the presence of human immunoglobulin G (HIgG), as the template exhibiting the same Fc region but different Fab region to anti-HIV-1 after the addition of the initiator, ammonium persulfate. This process resulted in grafting a hydrophilic molecularly imprinted polymer (MIP) film on the Fe3O4@SiO2 NPs. Thus, MMIPs, which could be reused after eluting the template, were used to recognize and enrich ultra-trace levels of anti-HIV-1. Subsequently, a novel sandwich ECL immunosensor was formed through the immunoreaction between MMIPs conjugated with varied concentrations of anti-HIV-1 and HRP-HIV-1. By the catalysis of HRP immobilized onto HRP-HIV-1 on the ECL system of Luminol-H2O2, a linear response range of the anti-HIV-1 dilution ratio (standard positive serum) was achieved from 1:20,000 to 1:50, with a detection limit of 1:60,000 (S/N=3). The developed method provides a low-cost, simple, and sensitive way for the early diagnosis of HIV infected patients. PMID:24280050

  1. Construction aggregates

    USGS Publications Warehouse

    Bolen, W.P.; Tepordei, V.V.

    2001-01-01

    The estimated production during 2000 of construction aggregates, crushed stone, and construction sand and gravel increased by about 2.6% to 2.7 Gt (3 billion st), compared with 1999. The expansion that started in 1992 continued with record production levels for the ninth consecutive year. By commodity, construction sand and gravel production increased by 4.5% to 1.16 Gt (1.28 billion st), while crushed stone production increased by 1.3% to 1.56 Gt (1.72 billion st).

  2. A study of sandwich T-joints and composite lap joints

    NASA Astrophysics Data System (ADS)

    Turaga, Umamaheswar V. R. S.

    In this study, new efficient designs for adhesive sandwich T-joint and single-lap joint were proposed and investigated. In the proposed new sandwich T-joint, called U-channel joint, the load transfer path at the web-flange interface was modified to include a U-shaped aluminum channel which provides strong path for load transfer. Experimental results show that the new design has 62% more strength than the conventional circular fillet joint. The new U-channel joint was tested in tension, compression and bending to investigate its characteristics. It is found to have good performance in bending also, even though in compression it performs same as the circular fillet joint. An extensive parametric study was carried out to investigate the effect of parameters like flange skin stiffener, foam density, foam thickness in the web, and aluminum attachments. A fracture mechanics criterion based on the strain energy release rate was used to explain the failure modes, apart from the stress analysis explanation. The failure loads of the joints in compression were predicted using a maximum principal stress failure criterion based on the sandwich beam theory. A new single lap joint with attachments was proposed in the second phase of the research. The design was verified using both aluminum and composite materials. The new design was found to have 59% more strength than the single-lap joint. A parametric study was performed to find out the influence of the angle of attachment, thickness of attachment and the length of attachment. By careful consideration of design parameters, the joint can be optimized. Finally, the failure loads of the single lap joints with and without attachments were predicted using different failure criteria.

  3. Sandwich-Architectured Poly(lactic acid)-Graphene Composite Food Packaging Films.

    PubMed

    Goh, Kunli; Heising, Jenneke K; Yuan, Yang; Karahan, Huseyin E; Wei, Li; Zhai, Shengli; Koh, Jia-Xuan; Htin, Nanda M; Zhang, Feimo; Wang, Rong; Fane, Anthony G; Dekker, Matthijs; Dehghani, Fariba; Chen, Yuan

    2016-04-20

    Biodegradable food packaging promises a more sustainable future. Among the many different biopolymers used, poly(lactic acid) (PLA) possesses the good mechanical property and cost-effectiveness necessary of a biodegradable food packaging. However, PLA food packaging suffers from poor water vapor and oxygen barrier properties compared to many petroleum-derived ones. A key challenge is, therefore, to simultaneously enhance both the water vapor and oxygen barrier properties of the PLA food packaging. To address this issue, we design a sandwich-architectured PLA-graphene composite film, which utilizes an impermeable reduced graphene oxide (rGO) as the core barrier and commercial PLA films as the outer protective encapsulation. The synergy between the barrier and the protective encapsulation results in a significant 87.6% reduction in the water vapor permeability. At the same time, the oxygen permeability is reduced by two orders of magnitude when evaluated under both dry and humid conditions. The excellent barrier properties can be attributed to the compact lamellar microstructure and the hydrophobicity of the rGO core barrier. Mechanistic analysis shows that the large rGO lateral dimension and the small interlayer spacing between the rGO sheets have created an extensive and tortuous diffusion pathway, which is up to 1450-times the thickness of the rGO barrier. In addition, the sandwiched architecture has imbued the PLA-rGO composite film with good processability, which increases the manageability of the film and its competency to be tailored. Simulations using the PLA-rGO composite food packaging film for edible oil and potato chips also exhibit at least eight-fold extension in the shelf life of these oxygen and moisture sensitive food products. Overall, these qualities have demonstrated the high potential of a sandwich-architectured PLA-graphene composite film for food packaging applications.

  4. It All Starts with a Sandwich: Identification of Sialidases with Trans-Glycosylation Activity

    PubMed Central

    Nordvang, Rune T.; Nyffenegger, Christian; Holck, Jesper; Jers, Carsten; Sundekilde, Ulrik K.; Meyer, Anne S.; Mikkelsen, Jørn D.

    2016-01-01

    Sialidases (3.2.1.18) may exhibit trans-sialidase activity to catalyze sialylation of lactose if the active site topology is congruent with that of the Trypanosoma cruzi trans-sialidase (EC 2.4.1.-). The present work was undertaken to test the hypothesis that a particular aromatic sandwich structure of two amino acids proximal to the active site of the T. cruzi trans-sialidase infers trans-sialidase activity. On this basis, four enzymes with putative trans-sialidase activity were identified through an iterative alignment from 2909 native sialidases available in GenBank, which were cloned and expressed in Escherichia coli. Of these, one enzyme, SialH, derived from Haemophilus parasuis had an aromatic sandwich structure on the protein surface facing the end of the catalytic site (Phe168; Trp366), and was indeed found to exhibit trans-sialidase activity. SialH catalyzed production of the human milk oligosaccharide 3’-sialyllactose as well as the novel trans-sialylation product 3-sialyllactose using casein glycomacropeptide as sialyl donor and lactose as acceptor. The findings corroborated that Tyr119 and Trp312 in the T. cruzi trans-sialidase are part of an aromatic sandwich structure that confers trans-sialylation activity for lactose sialylation. The in silico identification of trans-glycosidase activity by rational active site topology alignment thus proved to be a quick tool for selecting putative trans-sialidases amongst a large group of glycosyl hydrolases. The approach moreover provided data that help understand structure-function relations of trans-sialidases. PMID:27367145

  5. Interdiffusion and surface-sandwich ordering in initial Ni-core-Pd-shell nanoparticle.

    PubMed

    Evteev, Alexander V; Levchenko, Elena V; Belova, Irina V; Murch, Graeme E

    2009-05-01

    Using molecular dynamics simulation ( approximately 1 mus) in combination with the embedded atom method we have investigated interdiffusion and structural transformations at 1000 K in an initial core-shell nanoparticle (diameter approximately 4.5 nm). This starting particle has the f.c.c. structure in which a core of Ni atoms ( approximately 34%) is surrounded by a shell of Pd atoms ( approximately 66%). It is found that in such nanoparticles reactive diffusion accompanying nucleation and growth of a Pd(2)Ni ordering surface-sandwich structure takes place. In this structure, the Ni atoms mostly accumulate in a layer just below the surface and, at the same time, are located in the centres of interpenetrating icosahedra to generate a subsurface shell as a Kagomé net. Meanwhile, the Pd atoms occupy the vertices of the icosahedra and cover this Ni layer from the inside and outside as well as being located in the core of the nanoparticle forming (according to the alloy composition) a Pd-rich solid solution with the remaining Ni atoms. The total atomic fraction involved in building up the surface-sandwich shell of the nanoparticle in the form of the Ni Kagomé net layer covered on both side by Pd atoms is estimated at approximately 70%. These findings open up a range of opportunities for the experimental synthesis and study of new kinds of Pd-Ni nanostructures exhibiting Pd(2)Ni surface-sandwich ordering along with properties that may differ significantly from the corresponding bulk Pd-Ni alloys. Some of these opportunities are discussed.

  6. Functional expression and regulation of drug transporters in monolayer- and sandwich-cultured mouse hepatocytes.

    PubMed

    Noel, Gregory; Le Vee, Marc; Moreau, Amélie; Stieger, Bruno; Parmentier, Yannick; Fardel, Olivier

    2013-04-11

    Primary hepatocyte cultures are now considered as convenient models for in vitro analyzing liver drug transport. However, if primary human and rat hepatocytes have been well-characterized with respect to drug transporter expression and regulation, much less is known for primary mouse hepatocytes. The present study was therefore designed to gain insights about this point. The profile of sinusoidal and canalicular drug transporter mRNA expression in short time (4h)-cultured mouse hepatocytes was found to be highly correlated with that of freshly isolated hepatocytes; by contrast, those of counterparts cultured for a longer time (until 4 days) either in monolayer configurations on plastic or collagen or in sandwich configuration with matrigel were profoundly altered: uptake drug transporters such as Oct1, Oatps and Oat2 were thus down-regulated, whereas most of efflux transporters such as Mdr1a/b, Mrp3, Mrp4 and Bcrp were induced. Moreover, short time-cultured hepatocytes exhibited the highest levels of sinusoidal influx transporter activities. Transporter-mediated drug secretion into canalicular networks was however only observed in sandwich-cultured hepatocytes. Mouse hepatocytes cultured either in monolayer or sandwich configurations were finally shown to exhibit up-regulation of referent transporters in response to exposure to prototypical activators of the drug sensing receptors pregnane X receptor, aryl hydrocarbon receptor or constitutive androstane receptor. Taken together, these data demonstrate the feasibility of using primary mouse hepatocytes for investigating potential interactions of xenobiotics with hepatic transporter activity or regulation, provided that adequate culture conditions are retained. PMID:23396053

  7. It All Starts with a Sandwich: Identification of Sialidases with Trans-Glycosylation Activity.

    PubMed

    Nordvang, Rune T; Nyffenegger, Christian; Holck, Jesper; Jers, Carsten; Zeuner, Birgitte; Sundekilde, Ulrik K; Meyer, Anne S; Mikkelsen, Jørn D

    2016-01-01

    Sialidases (3.2.1.18) may exhibit trans-sialidase activity to catalyze sialylation of lactose if the active site topology is congruent with that of the Trypanosoma cruzi trans-sialidase (EC 2.4.1.-). The present work was undertaken to test the hypothesis that a particular aromatic sandwich structure of two amino acids proximal to the active site of the T. cruzi trans-sialidase infers trans-sialidase activity. On this basis, four enzymes with putative trans-sialidase activity were identified through an iterative alignment from 2909 native sialidases available in GenBank, which were cloned and expressed in Escherichia coli. Of these, one enzyme, SialH, derived from Haemophilus parasuis had an aromatic sandwich structure on the protein surface facing the end of the catalytic site (Phe168; Trp366), and was indeed found to exhibit trans-sialidase activity. SialH catalyzed production of the human milk oligosaccharide 3'-sialyllactose as well as the novel trans-sialylation product 3-sialyllactose using casein glycomacropeptide as sialyl donor and lactose as acceptor. The findings corroborated that Tyr119 and Trp312 in the T. cruzi trans-sialidase are part of an aromatic sandwich structure that confers trans-sialylation activity for lactose sialylation. The in silico identification of trans-glycosidase activity by rational active site topology alignment thus proved to be a quick tool for selecting putative trans-sialidases amongst a large group of glycosyl hydrolases. The approach moreover provided data that help understand structure-function relations of trans-sialidases. PMID:27367145

  8. Sandwich enzyme-linked immunosorbent assay (ELISA) for the detection of lupine residues in foods.

    PubMed

    Kaw, C H; Hefle, S L; Taylor, S L

    2008-10-01

    Lupine has been increasingly used in food applications due to its high nutritional value and excellent functional properties. However, lupine provokes allergic reactions in susceptible individuals. The presence of undeclared lupine residues in foods can pose a serious health risk to lupine-allergic individuals. Therefore, the objective of this research was to develop a sandwich-type ELISA for the detection of lupine residues in foods. Lupine flour derived from Lupinus albus was used to immunize 3 rabbits and a sheep. Pooled lupine-specific antibodies were partially purified from the sera by ammonium sulfate precipitation. A sandwich lupine ELISA with a limit of quantification (LOQ) of 1 ppm was developed by utilizing the rabbit antisera as the capture reagent and the sheep antiserum as the detector reagent. The binding of the antigen-antibody complex was visualized by the addition of commercial rabbit antisheep IgG antibody labeled with alkaline phosphatase with subsequent addition of p-nitrophenyl phosphate substrate to produce a colored product for quantification. Minor cross-reactivity was observed with soy (Glycine max) and black bean (Castanospermum australe). The performance of the lupine ELISA was evaluated in reference food standards (beef frankfurter and apple cinnamon muffin) and laboratory-prepared cooked frankfurters and corn muffins. The mean percent recovery for lupine spiked-frankfurters and corn muffins were 108.4%+/- 8.8% and 103.1%+/- 11.5%, respectively. The sandwich-type lupine ELISA developed in this study provides food manufacturers and regulatory agencies with an effective analytical tool to detect and quantify lupine residues in processed foods.

  9. Sandwich-Architectured Poly(lactic acid)-Graphene Composite Food Packaging Films.

    PubMed

    Goh, Kunli; Heising, Jenneke K; Yuan, Yang; Karahan, Huseyin E; Wei, Li; Zhai, Shengli; Koh, Jia-Xuan; Htin, Nanda M; Zhang, Feimo; Wang, Rong; Fane, Anthony G; Dekker, Matthijs; Dehghani, Fariba; Chen, Yuan

    2016-04-20

    Biodegradable food packaging promises a more sustainable future. Among the many different biopolymers used, poly(lactic acid) (PLA) possesses the good mechanical property and cost-effectiveness necessary of a biodegradable food packaging. However, PLA food packaging suffers from poor water vapor and oxygen barrier properties compared to many petroleum-derived ones. A key challenge is, therefore, to simultaneously enhance both the water vapor and oxygen barrier properties of the PLA food packaging. To address this issue, we design a sandwich-architectured PLA-graphene composite film, which utilizes an impermeable reduced graphene oxide (rGO) as the core barrier and commercial PLA films as the outer protective encapsulation. The synergy between the barrier and the protective encapsulation results in a significant 87.6% reduction in the water vapor permeability. At the same time, the oxygen permeability is reduced by two orders of magnitude when evaluated under both dry and humid conditions. The excellent barrier properties can be attributed to the compact lamellar microstructure and the hydrophobicity of the rGO core barrier. Mechanistic analysis shows that the large rGO lateral dimension and the small interlayer spacing between the rGO sheets have created an extensive and tortuous diffusion pathway, which is up to 1450-times the thickness of the rGO barrier. In addition, the sandwiched architecture has imbued the PLA-rGO composite film with good processability, which increases the manageability of the film and its competency to be tailored. Simulations using the PLA-rGO composite food packaging film for edible oil and potato chips also exhibit at least eight-fold extension in the shelf life of these oxygen and moisture sensitive food products. Overall, these qualities have demonstrated the high potential of a sandwich-architectured PLA-graphene composite film for food packaging applications. PMID:27028268

  10. Construction Administration.

    ERIC Educational Resources Information Center

    Barley, John McKim, II

    1986-01-01

    Successful completion of a construction project requires the efforts of a team composed of the owner, architect, and contractor. A preconstruction conference can clarify the roles of the team as specified in the design contract. (MLF)

  11. Constructing Phylogenies.

    ERIC Educational Resources Information Center

    Bilardello, Nicholas; Valdes, Linda

    1998-01-01

    Introduces a method for constructing phylogenies using molecular traits and elementary graph theory. Discusses analyzing molecular data and using weighted graphs, minimum-weight spanning trees, and rooted cube phylogenies to display the data. (DDR)

  12. The Effect of Temperature on Faceplate/Core Delamination in Composite/Titanium Sandwich Plates

    NASA Technical Reports Server (NTRS)

    Liechti, Kenneth M.; Marton, Balazs

    2000-01-01

    A study was made of the delamination behavior of sandwich beams made of titanium core bonded to face-plates that consisted of carbon fiber reinforced polymer composite. Nominally mode I behavior was considered at 23C and 180C, by making use of a specially reinforced double cantilever (DCB) specimens. The toughness of the bond between the faceplate and the core was determined on the basis of a beam on elastic foundation analysis. The specimen compliance, and toughness were all independent of temperature in these relatively short-term experiments. The fracture mechanism showed temperature dependence, due to the hygrothermal sensitivity of the adhesive.

  13. Low-energy impact resistance of graphite-epoxy plates and ALS honeycomb sandwich panels

    NASA Technical Reports Server (NTRS)

    Hui, David

    1989-01-01

    Low energy impact may be potentially dangerous for many highly optimized stiff structures. Impact by foreign objects such as birds, ice, and runways stones or dropping of tools occur frequently and the resulting damage and stress concentrations may be unacceptable from a designer's standpoint. The barely visible, yet potentially dangerous dents due to impact of foreign objects on the Advanced Launch System (ALS) structure are studied. Of particular interest is the computation of the maximum peak impact force for a given impactor mass and initial velocity. The theoretical impact forces will be compared with the experimental dropweight results for the ALS face sheets alone as well as the ALS honeycomb sandwich panels.

  14. Appearance of "fragile" Fermi liquids in finite-width Mott insulators sandwiched between metallic leads.

    PubMed

    Zenia, H; Freericks, J K; Krishnamurthy, H R; Pruschke, Th

    2009-09-11

    Using inhomogeneous dynamical mean-field theory, we show that the normal-metal proximity effect could force any finite number of Mott-insulating "barrier" planes sandwiched between semi-infinite metallic leads to become "fragile" Fermi liquids. They are fully Fermi-liquid-like at T=0, leading to a restoration of lattice periodicity at zero frequency, with a well-defined Fermi surface, and perfect (ballistic) conductivity. However, the Fermi-liquid character can rapidly disappear at finite omega, V, T, disorder, or magnetism, all of which restore the expected quantum tunneling regime, leading to fascinating possibilities for nonlinear response in devices.

  15. Application of Air Coupled Acoustic Thermography (ACAT) for Inspection of Honeycomb Sandwich Structures

    NASA Technical Reports Server (NTRS)

    Winfree, William P.; Zalameda, Joseph N.; Pergantis, Charles; Flanagan, David; Deschepper, Daniel

    2009-01-01

    The application of a noncontact air coupled acoustic heating technique is investigated for the inspection of advanced honeycomb composite structures. A weakness in the out of plane stiffness of the structure, caused by a delamination or core damage, allows for the coupling of acoustic energy and thus this area will have a higher temperature than the surrounding area. Air coupled acoustic thermography (ACAT) measurements were made on composite sandwich structures with damage and were compared to conventional flash thermography. A vibrating plate model is presented to predict the optimal acoustic source frequency. Improvements to the measurement technique are also discussed.

  16. Tunable surface plasmon-polaritons in a gyroelectric slab sandwiched between two graphene layers

    NASA Astrophysics Data System (ADS)

    Xu, Guoding; Cao, Ming; Liu, Chang; Sun, Jian; Pan, Tao

    2016-05-01

    We study numerically the properties of surface plasmon-polaritons (SPPs) in a gyroelectric slab sandwiched between two graphene layers, where the external static magnetic field is applied in the Voigt geometry. It is shown that the dispersion characteristics and propagation lenghts of the SPPs for both the optical and the acoustic branches can be tuned flexibly by the external magnetic field and graphene's chemical potential, and that the nonreciprocal properties of the SPPs caused by the external magnetic field are rather obvious. The results provide a method for adjusting and improving the dispersion and propagation properties of the SPPs, which might be helpful for the design of the related plasmonic devices.

  17. New sandwich-type lanthanide complexes based on closed-macrocyclic Schiff base and phthalocyanine molecules.

    PubMed

    Gao, Feng; Feng, Xiaowan; Yang, Liu; Chen, Xiaoyu

    2016-04-25

    Two new sandwich-type lanthanide complexes with the general formula [(Pc)2Ln3(L)(OAc)(OCH3)2] (Ln(3+) = Dy(3+) () and Er(3+) ()) were successfully synthesized and structurally characterized based on closed-macrocyclic Schiff base and phthalocyanine molecules. The magnetic properties and structure-property relationship in this multi-decker system were investigated. Interestingly, the corresponding dysprosium complex shows typical single-molecule magnetic behavior with ferromagnetic dipole-dipole interactions and the slow relaxation of magnetization. PMID:27044594

  18. Compression After Impact Experiments and Analysis on Honeycomb Core Sandwich Panels with Thin Facesheets

    NASA Technical Reports Server (NTRS)

    McQuigg, Thomas D.

    2011-01-01

    A better understanding of the effect of impact damage on composite structures is necessary to give the engineer an ability to design safe, efficient structures. Current composite structures suffer severe strength reduction under compressive loading conditions, due to even light damage, such as from low velocity impact. A review is undertaken to access the current state-of-development in the areas of experimental testing, and analysis methods. A set of experiments on honeycomb core sandwich panels, with thin woven fiberglass cloth facesheets, is described, which includes detailed instrumentation and unique observation techniques.

  19. Small metal-organic molecular sandwiches: Versatile units for induced structure manipulation

    NASA Astrophysics Data System (ADS)

    Naumkin, Fedor Y.; Fisher, Kayla

    2013-12-01

    Interfaces between metal atoms and organic molecules are key units of many important metal-organic systems. Presented are results of ab initio calculations for a series of complexes of 2nd-row metal atoms sandwiched between small unsaturated hydrocarbon molecules. Evolution of the system structure and stability is studied for different metal atoms, as well as upon excitation, ionization and electron attachment. Predicted interesting features include cooperative stabilization, unusual geometries, reversible charge- or excitation-governed geometry alterations. The observed variety of properties suggests potential applications of such species as intermolecular junctions and units with charge- or spin-controlled shapes in molecular devices and/or machines.

  20. Proton radiography of PBX 9502 detonation shock dynamics confinement sandwich test

    SciTech Connect

    Aslam, Tariq D; Jackson, Scott I; Morris, John S

    2009-01-01

    Recent results utilizing proton radiography (P-Rad) during the detonation of the high explosive PBX 9502 are presented. Specifically, the effects of confinement of the detonation are examined in the LANL detonation confinement sandwich geometry. The resulting detonation velocity and detonation shock shape are measured. In addition, proton radiography allows one to image the reflected shocks through the detonation products. Comparisons are made with detonation shock dynamics (DSD) and reactive flow models for the lead detonation shock and detonation velocity. In addition, predictions of reflected shocks are made with the reactive flow models.

  1. Generation of quasi-monoenergetic carbon ions accelerated parallel to the plane of a sandwich target

    SciTech Connect

    Wang, J. W.; Murakami, M.; Weng, S. M.; Xu, H.; Ju, J. J.; Luan, S. X.; Yu, W.

    2014-12-15

    A new ion acceleration scheme, namely, target parallel Coulomb acceleration, is proposed in which a carbon plate sandwiched between gold layers is irradiated with intense linearly polarized laser pulses. The high electrostatic field generated by the gold ions efficiently accelerates the embedded carbon ions parallel to the plane of the target. The ion beam is found to be collimated by the concave-shaped Coulomb potential. As a result, a quasi-monoenergetic and collimated C{sup 6+}-ion beam with an energy exceeding 10 MeV/nucleon is produced at a laser intensity of 5 × 10{sup 19} W/cm{sup 2}.

  2. Electron-beam-induced alteration of the dielectric properties of sandwiched self-assembled organic monolayers

    NASA Astrophysics Data System (ADS)

    Balaur, Eugeniu; Peele, Andrew G.

    2010-04-01

    Electrical transport through octadecyltrichlorosilane self-assembled monolayers sandwiched between a silicon substrate and an aluminum film was altered using electron-beams (e-beams) with different energies and doses. Under certain e-beam conditions, improvement of the dielectric performance was observed compared with the unmodified monolayers. This was ascribed to partial "healing" of the gauche defects within the alkyl chains under the electron flux. It was also possible to vary the barrier height between 2 and 2.35 eV, an effect attributed to the creation of amorphous carbon under prolonged exposure times. Factors that influenced these effects were identified and discussed.

  3. Assessment of a commercial sandwich ELISA in the diagnosis of aspergillosis in falcons.

    PubMed

    Arca-Ruibal, B; Wernery, U; Zachariah, R; Bailey, T A; Di Somma, A; Silvanose, C; McKinney, P

    2006-04-01

    A commercial sandwich elisa (Platelia Aspergillus EIA; Bio-Rad) developed for the detection of galactomannan, a major cell wall constituent of Aspergillus species, was tested for its efficacy in the diagnosis of aspergillosis in falcons. Ninety serum samples from 50 aspergillosis-positive falcons and 182 samples from 142 aspergillosis-negative falcons were tested. The sensitivity of the test was only 12 per cent and its specificity was 95 percent. The test was therefore unsatisfactory for detecting galactomannan in the serum samples and cannot be used as a screening test for aspergillosis in falcons.

  4. Numerical Analysis of Thermodynamic Behaviour of Through-Thickness Stitched Sandwich Laminate

    NASA Astrophysics Data System (ADS)

    Shigang, Ai; Yiqi, Mao; Yongmao, Pei; Daining, Fang; Liqun, Tang

    2013-12-01

    Effects of stitching angle on mechanical properties, thermal protection capability and induced thermal stress of stitched sandwich laminate (SSL) are numerically analyzed by ABAQUS codes. Interest centers on the potential for microcracking in the vicinity of the through-thickness stitches and the skins/foam interfaces. Two numerical models, in-depth heat transfer and thermoelastic deformation, are coupled to yield the transient response of the SSL. Six different stitching angles are considered and the simulation results showed that: the heat conductivity ability of the SSL is improved as the stitching angle increasing, which alters the mechanical behaviour and the thermal stress state of the SSL.

  5. Employment of a metal microgrid as a front electrode in a sandwich-structured photodetector.

    PubMed

    Zhang, Junying; Cai, Chao; Pan, Feng; Hao, Weichang; Zhang, Weiwei; Wang, Tianmin

    2009-07-01

    A highly UV-transparent metal microgrid was prepared and employed as the front electrode in a sandwich-structured ultraviolet (UV) photodetector using TiO(2) thin film as the semiconductor layer. The photo-generated charger carriers travel a shorter distance before reaching the electrodes in comparison with a photodetector using large-spaced interdigitated metal electrodes (where distance between fingers is several to tens of micrometers) on the surface of the semiconductor film. This photodetector responds to UV light irradiation, and the photocurrent intensity increases linearly with the irradiation intensity below 0.2 mW/cm(2). PMID:19571918

  6. Mechanical analysis of confectioning flaw of refractory alloy honeycomb sandwich structure

    NASA Astrophysics Data System (ADS)

    He, Xiaodong; Kong, Xianghao; Shi, Liping; Li, Mingwei

    2009-03-01

    Thermal protection system is one of the key technology of reusable launch vehicle (RLV). After C/C and ceramic-matrix composite used in space orbiter, one new-typed thermal protection systems (TPS)-ARMOR TPS is coming forth. ARMOR TPS is means adaptable, robust, metallic, operable, reusable TPS. The ARMOR TPS has many advantages, for example: fixing easily, longer life, good properties, short time of maintenance and service. The ARMOR TPS is one of important candidate structure of RLV. ARMOR thermal protection system in foreign countries for reusable launch vehicle is used instead of the traditional ceramic-matrix composite thermal protection system and C/C thermal protection system. Also the constituent feature of ARMOR thermal protection system is much better than the traditional TPS. In comparison with traditional TPS, the ARMOR TPS will be the best selection for all kinds of RLV. So the ARMOR thermal protection system will be used in aviation and spaceflight field more and more widely because of its much better performance. ARMOR TPS panel is above the whole ARMOR TPS, and the metal honeycomb sandwich structure is the surface of the ARMOR TPS panel. So the metal honeycomb sandwich structure plays an important role in the ARMOR TPS, while it bears the flight dynamic pressure and stands against the flight dynamic calefaction. The metal honeycomb sandwich structure is made using the technique of the whole braze welding. In the course of the vacuum high temperature braze welding, its surface will appear concave. The reasons which lead to the shortage are summarized and discussed. The difference of thermal expansion coefficient and pressure between the core and the panels may be the chief reasons. This paper will analyze the mechanics behavior of metal honeycomb sandwich structure in the course of the vacuum high temperature braze welding, then make sure the reasons and get a way to solve it. Haynes214 is a good material of face sheet at present. γ - TiAl and

  7. Damage detection in a radome sandwich material with embedded fiber optic sensors

    NASA Astrophysics Data System (ADS)

    Bocherens, E.; Bourasseau, S.; Dewynter-Marty, V.; Py, S.; Dupont, M.; Ferdinand, P.; Berenger, H.

    2000-06-01

    Embedded distributed micro/macro-bending multimode optical fiber transducers multiplexed in the time domain (photon counting, optical time domain reflectometry) and quasi-distributed embedded in-fiber Bragg grating (FBG) filters based on wavelength measurement and demultiplexing encoding have been used for damage detection assessment in a radome sandwich structure. Both methods are well suited for detection and localization of permanent damage induced by impacts of energy ranging from 8-20 J. Optical fiber sensor measurements have been compared to those given by classical health monitoring methods using ultrasonics and shearography, as well as infrared thermography.

  8. Parameters estimation of sandwich beam model with rigid polyurethane foam core

    NASA Astrophysics Data System (ADS)

    Barbieri, Nilson; Barbieri, Renato; Winikes, Luiz Carlos

    2010-02-01

    In this work, the physical parameters of sandwich beams made with the association of hot-rolled steel, Polyurethane rigid foam and High Impact Polystyrene, used for the assembly of household refrigerators and food freezers are estimated using measured and numeric frequency response functions (FRFs). The mathematical models are obtained using the finite element method (FEM) and the Timoshenko beam theory. The physical parameters are estimated using the amplitude correlation coefficient and genetic algorithm (GA). The experimental data are obtained using the impact hammer and four accelerometers displaced along the sample (cantilevered beam). The parameters estimated are Young's modulus and the loss factor of the Polyurethane rigid foam and the High Impact Polystyrene.

  9. A note concerning the Lighthill “sandwich model” of tropical cyclones

    PubMed Central

    Barenblatt, G. I.; Chorin, A. J.; Prostokishin, V. M.

    2005-01-01

    The basic element of Lighthill's “sandwich model” of tropical cyclones is the existence of “ocean spray,” a layer intermediate between air and sea made up of a cloud of droplets that can be viewed as a “third fluid.” We propose a mathematical model of the flow in the ocean spray based on a semiempirical turbulence theory and demonstrate that the availability of the ocean spray over the waves in the ocean can explain the tremendous acceleration of the wind as a consequence of the reduction of the turbulence intensity by droplets. This explanation complements the thermodynamic arguments proposed by Lighthill. PMID:16049097

  10. Archetypal sandwich-structured CuO for high performance non-enzymatic sensing of glucose

    NASA Astrophysics Data System (ADS)

    Meher, Sumanta Kumar; Rao, G. Ranga

    2013-02-01

    In the quest to enhance the selectivity and sensitivity of novel structured metal oxides for electrochemical non-enzymatic sensing of glucose, we report here a green synthesis of unique sandwich-structured CuO on a large scale under microwave mediated homogeneous precipitation conditions. The physicochemical studies carried out by XRD and BET methods show that the monoclinic CuO formed via thermal decomposition of Cu2(OH)2CO3 possesses monomodal channel-type pores with largely improved surface area (~43 m2 g-1) and pore volume (0.163 cm3 g-1). The fascinating surface morphology and pore structure of CuO is formulated due to homogeneous crystallization and microwave induced self assembly during synthesis. The cyclic voltammetry and chronoamperometry studies show diffusion controlled glucose oxidation at ~0.6 V (vs. Ag/AgCl) with extremely high sensitivity of 5342.8 μA mM-1 cm-2 and respective detection limit and response time of ~1 μM and ~0.7 s, under a wide dynamic concentration range of glucose. The chronoamperometry measurements demonstrate that the sensitivity of CuO to glucose is unaffected by the absence of dissolved oxygen and presence of poisoning chloride ions in the reaction medium, which essentially implies high poison resistance activity of the sandwich-structured CuO. The sandwich-structured CuO also shows insignificant interference/significant selectivity to glucose, even in the presence of high concentrations of other sugars as well as reducing species. In addition, the sandwich-structured CuO shows excellent reproducibility (relative standard deviation of ~2.4% over ten identically fabricated electrodes) and outstanding long term stability (only ~1.3% loss in sensitivity over a period of one month) during non-enzymatic electrochemical sensing of glucose. The unique microstructure and suitable channel-type pore architecture provide structural stability and maximum accessible electroactive surface for unimpeded mobility of glucose as well as the

  11. Behavior and Failure Modes of Sandwich T-Joint Using Cohesive Zone Material Model and Contact Elements

    NASA Astrophysics Data System (ADS)

    Khalili, S. M. R.; Ghaznavi, A.

    2013-02-01

    One of the significant concerns of sandwich panels is their joints. T-joint is one the most common joint in sandwich structures. This paper deals with the numerical study of triangle T-joint under static loading. The results of numerical solution obtained by ANSYS modeling are verified with the results of experimental tests obtained in the literature. In general, the results obtained for anticipated failure load by numerical solution with the results of experimental test is in good agreement. Contact elements and cohesive zone material model are used to model the adhesive layer, hence debonding and fracture of adhesive is observed by the numerical modeling. Also, by using a written macro code in the ANSYS software, the ability of damage is explained for the core of sandwich panels; thus both the modes in fracture of T-joints (core shear failure in base panel and debonding of adhesive) are modeled. Core materials consist of Divinycell H100, H160, H250, and HCP70 are used for modeling sandwich panels, so that the function of joint is studied under different conditions of the sandwich core material. Nine different geometrical models are created by changing the base angle of the core triangle. The absorbed energy associated with different segments of the T-joint are used to investigate the effect of joint geometry and core material on the load transfer and failure mode of the T-joint.

  12. Rational screening of antibodies and design of sandwich enzyme linked immunosorbant assay on the basis of a kinetic model.

    PubMed

    Choi, Dong Hwan; Katakura, Yoshio; Ninomiya, Kazuaki; Shioya, Suteaki

    2008-03-01

    A rational strategy for the rapid establishment of a sensitive sandwich enzyme linked immunosorbant assay was developed. The kinetic properties required for the solid-phase and enzyme-conjugated antibodies of sandwich ELISA were determined rationally on the basis of a kinetic model describing antibody-antigen interaction. Some antibodies possessing the required kinetic properties against a model antigen, C-reactive protein (CRP), were successfully isolated from a phage antibody library under the screening conditions that were designed on the basis of simulation results. The best combination of solid-phase and enzyme-conjugated antibodies that gives the most sensitive sandwich ELISA was determined by simulation on the basis of the apparent association and dissociation rate constants of the isolated antibodies. It was confirmed by experiment that the sandwich ELISA using the best combination of antibodies was actually the most sensitive one. Our strategy would be useful for the rapid establishment of sensitive sandwich ELISAs compared with the traditional hybridoma method in which the best condition is determined by trial and error.

  13. Present-day stress field on the South American slab underneath the Sandwich Plate (Southern Atlantic Ocean)

    NASA Astrophysics Data System (ADS)

    Giner-Robles, J. L.; Pérez-López, R.; Álvarez-Gómez, J. A.; Martínez-Díaz, J. J.; Rodríguez-Pascua, M. A.

    2009-04-01

    This work confirms the present-day principal stress orientation on the South Sandwich Plate (SSP) from the analysis of 331 earthquake focal mechanisms (Harvard catalog, HCMT). Principal stress orientation was deduced from earthquake focal mechanisms, examined by fault population analysis methods. The SSP plate is composed by oceanic crust limits an elliptical trench to the east (South Sandwich Trench), a ridge to the west and transforms faults towards the northern and southern boundaries. Within the trench region, the maximum horizontal shortening direction (SHMAX) rotates in trend in a clockwise direction, from NNE, in the northern boundary, to SSE in the southern boundary. Therefore, and keeping in mind the gradual rotation of SHMAX along the trench, three different areas were defined according to the prevailing focal mechanism type: (1) the North Zone, with SHMAX oriented N060°E and reverse and strike-slip focal mechanisms; (2) the Central Zone, with only reverse focal mechanism and SHMAX striking N080°E; (3) the South Zone, with SHMAX oriented N110°E and reverse and strike-slip focal geometry. Furthermore, the accommodation of the strain field in the Northern Zone of the South Sandwich Plate generates a subduction decoupling of the slab at, approximately, 70 km depth. In contrast, the South Zone slab exhibits a gradual stress and strain magnitude decreasing in depth. Finally, we define a sinistral strike-slip parallel to the southern boundary between the South Sandwich Plate and the Antarctic Plate, the South Sandwich Fault Zone.

  14. Amorphous GeOx-Coated Reduced Graphene Oxide Balls with Sandwich Structure for Long-Life Lithium-Ion Batteries.

    PubMed

    Choi, Seung Ho; Jung, Kyeong Youl; Kang, Yun Chan

    2015-07-01

    Amorphous GeOx-coated reduced graphene oxide (rGO) balls with sandwich structure are prepared via a spray-pyrolysis process using polystyrene (PS) nanobeads as sacrificial templates. This sandwich structure is formed by uniformly coating the exterior and interior of few-layer rGO with amorphous GeOx layers. X-ray photoelectron spectroscopy analysis reveals a Ge:O stoichiometry ratio of 1:1.7. The amorphous GeOx-coated rGO balls with sandwich structure have low charge-transfer resistance and fast Li(+)-ion diffusion rate. For example, at a current density of 2 A g(-1), the GeOx-coated rGO balls with sandwich and filled structures and the commercial GeO2 powders exhibit initial charge capacities of 795, 651, and 634 mA h g(-1), respectively; the corresponding 700th-cycle charge capacities are 758, 579, and 361 mA h g(-1). In addition, at a current density of 5 A g(-1), the rGO balls with sandwich structure have a 1600th-cycle reversible charge capacity of 629 mA h g(-1) and a corresponding capacity retention of 90.7%, as measured from the maximum reversible capacity at the 100th cycle.

  15. Construction aggregates

    USGS Publications Warehouse

    Nelson, T.I.; Bolen, W.P.

    2007-01-01

    Construction aggregates, primarily stone, sand and gravel, are recovered from widespread naturally occurring mineral deposits and processed for use primarily in the construction industry. They are mined, crushed, sorted by size and sold loose or combined with portland cement or asphaltic cement to make concrete products to build roads, houses, buildings, and other structures. Much smaller quantities are used in agriculture, cement manufacture, chemical and metallurgical processes, glass production and many other products.

  16. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1993-01-01

    Part of a special section on the market performance of industrial minerals in 1992. Production of construction aggregates increased by 4.6 percent in 1992. This increase was due, in part, to the increased funding for transportation and infrastructure projects. The U.S. produced about 1.05 Gt of crushed stone and an estimated 734 Mt of construction sand and gravel in 1992. Demand is expected to increase by about 5 percent in 1993.

  17. Worldwide construction

    SciTech Connect

    Williamson, M.

    1994-10-17

    The paper lists major construction projects in worldwide processing and pipelining, showing capacities, contractors, estimated costs, and time of construction. The lists are divided into refineries, petrochemical plants, sulfur recovery units, gas processing plants, pipelines, and related fuel facilities. This last classification includes cogeneration plants, coal liquefaction and gasification plants, biomass power plants, geothermal power plants, integrated coal gasification combined-cycle power plants, and a coal briquetting plant.

  18. Sound radiation and transmission loss characteristics of a honeycomb sandwich panel with composite facings: Effect of inherent material damping

    NASA Astrophysics Data System (ADS)

    Arunkumar, M. P.; Jagadeesh, M.; Pitchaimani, Jeyaraj; Gangadharan, K. V.; Babu, M. C. Lenin

    2016-11-01

    This paper presents the results of numerical studies carried out on vibro-acoustic and sound transmission loss behaviour of aluminium honeycomb core sandwich panel with fibre reinforced plastic (FRP) facings. Layered structural shell element with equivalent orthotropic elastic properties of core and orthotropic properties of FRP facing layer is used to predict the free and forced vibration characteristics. Followed by this, acoustic response and transmission loss characteristics are obtained using Rayleigh integral. Vibration and acoustic characteristics of FRP sandwich panels are compared with aluminium sandwich panels. The result reveals that FRP panel has better vibro-acoustic and transmission loss characteristics due to high stiffness and inherent material damping associated with them. Resonant amplitudes of the response are fully controlled by modal damping factors calculated based on modal strain energy. It is also demonstrated that FRP panel can be used to replace the aluminium panel without losing acoustic comfort with nearly 40 percent weight reduction.

  19. Metal-Organic Frameworks (MOFs) as Sandwich Coating Cushion for Silicon Anode in Lithium Ion Batteries.

    PubMed

    Han, Yuzhen; Qi, Pengfei; Zhou, Junwen; Feng, Xiao; Li, Siwu; Fu, Xiaotao; Zhao, Jingshu; Yu, Danni; Wang, Bo

    2015-12-01

    A novel metal-organic framework (MOF) sandwich coating method (denoted as MOF-SC) is developed for hybrid Li ion battery electrode preparation, in which the MOF films are casted on the surface of a silicon layer and sandwiched between the active silicon and the separator. The obtained electrodes show improved cycling performance. The areal capacity of the cheap and readily available microsized Si treated with MOF-SC can reach 1700 μAh cm(-2) at 265 μA cm(-2) and maintain at 850 μAh cm(-2) after 50 cycles. Beyond the above, the commercial nanosized Si treated by MOF-SC also shows greatly enhanced areal capacity and outstanding cycle stability, 600 μAh cm(-2) for 100 cycles without any apparent fading. By virtue of the novel structure prepared by the MOFs, this new MOF-SC structure serves as an efficient protection cushion for the drastic volume change of silicon during charge/discharge cycles. Furthermore, this MOF layer, with large pore volume and high surface area, can adsorb electrolyte and allow faster diffusion of Li(+) as evidenced by decreased impedance and improved rate performance. PMID:26569374

  20. Semi-active control of a sandwich beam partially filled with magnetorheological elastomer

    NASA Astrophysics Data System (ADS)

    Dyniewicz, Bartłomiej; Bajkowski, Jacek M.; Bajer, Czesław I.

    2015-08-01

    The paper deals with the semi-active control of vibrations of structural elements. Elastomer composites with ferromagnetic particles that act as magnetorheological fluids are used. The damping coefficient and the shear modulus of the elastomer increases when it is exposed to an electro-magnetic field. The control of this process in time allows us to reduce vibrations more effectively than if the elastomer is permanently exposed to a magnetic field. First the analytical solution for the vibrations of a sandwich beam filled with an elastomer is given. Then the control problem is defined and applied to the analytical formula. The numerical solution of the minimization problem results in a periodic, perfectly rectangular control function if free vibrations are considered. Such a temporarily acting magnetic field is more efficient than a constantly acting one. The surplus reaches 20-50% or more, depending on the filling ratio of the elastomer. The resulting control was verified experimentally in the vibrations of a cantilever sandwich beam. The proposed semi-active control can be directly applied to engineering vibrating structural elements, for example helicopter rotors, aircraft wings, pads under machines, and vehicles.

  1. Three different signal amplification strategies for the impedimetric sandwich detection of thrombin.

    PubMed

    Ocaña, Cristina; del Valle, Manel

    2016-03-17

    In this work, we report a comparative study on three highly specific amplification strategies for the ultrasensitive detection of thrombin with the use of aptamer sandwich protocol. The protocol consisted on the use of a first thrombin aptamer immobilized on the electrode surface, the recognition of thrombin protein, and the reaction with a second biotinylated thrombin aptamer forming the sandwich. Through the exposed biotin end, three variants have been tested to amplify the electrochemical impedance signal. The strategies included (a) silver enhancement treatment, (b) gold enhancement treatment and (c) insoluble product produced by the combination of the enzyme horseradish peroxidase (HRP) and 3-amino-9-ethylcarbazole (AEC). The properties of the sensing surface were probed by electrochemical impedance measurements in the presence of the ferrocyanide/ferricyanide redox marker. Insoluble product strategy and silver enhancement treatment resulted in the lowest detection limit (0.3 pM), while gold enhancement method resulted in the highest reproducibility, 8.8% RSD at the pM thrombin concentration levels. Results of silver and gold enhancement treatment also permitted direct inspection by scanning electron microscopy (SEM). PMID:26920780

  2. Determination of glycinin in soybean and soybean products using a sandwich enzyme-linked immunosorbent assay.

    PubMed

    Chen, Jingshu; Wang, Ji; Song, Peixia; Ma, Xi

    2014-11-01

    This study performs a sandwich ELISA for detection of trace amounts of glycinin in soybean products. We designed a soy-free mouse model to produce anti-glycinin monoclonal antibodies with high affinity and specificity. Using the monoclonal antibody as coating antibody, with the rabbit anti-glycinin polyclonal antibody as a detected antibody, the established sandwich ELISA showed high specificity for glycinin with minimum cross-reactions with other soy proteins. The practical working range of the determination was 3-200 ng/mL with detection limit of 1.63 ng/mL. The regaining of glycinin in spiked soybean samples were between 93.8% and 103.3% with relative standard deviation less than 8.3% (intra-day) and 10.5% (inter-day). The developed assay was used in analysing 469 soybean samples and five soybean products under different processing. The assay provides a specific and sensitive method for screening of glycinin and allows for further investigation into hypersensitive mechanisms to soybean proteins. PMID:24874353

  3. Fabrication of mucoadhesive chitosan coated polyvinylpyrrolidone/cyclodextrin/clotrimazole sandwich patches for oral candidiasis.

    PubMed

    Tonglairoum, Prasopchai; Ngawhirunpat, Tanasait; Rojanarata, Theerasak; Panomsuk, Suwanee; Kaomongkolgit, Ruchadaporn; Opanasopit, Praneet

    2015-11-01

    This study aims to fabricate clotrimazole (CZ)-composite sandwich nanofibers using electrospinning. The CZ-loaded polyvinylpyrrolidone (PVP)/hydroxypropyl-β-cyclodextrin (HPβCD) fiber was coated with chitosan-cysteine (CS-SH)/polyvinyl alcohol (PVA) to increase the mucoadhesive properties and to achieve a sustained release of the drug from the nanofibers. The nanofibers were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and X-ray diffractometry (XRD). The nanofibers mechanical and mucoadhesive properties, drug release, antifungal activity and cytotoxicity were also assessed. The fibers were in the nanoscale with good mucoadhesive properties. The XRPD revealed a molecular dispersion of amorphous CZ in the nanofibers. The initial fast release of CZ from the nanofibers was achieved. Moreover, the sandwich nanofibers coated for longer times resulted in slower release rates compared with the shorter coating times. The CZ-loaded nanofibers killed the Candida significantly faster than the commercial CZ lozenges at 5, 15 and 30 min and were safe for a 2-h incubation. Therefore, these nanofibers may be promising candidates for the treatment of oral candidiasis. PMID:26256338

  4. A Pyridazine-Bridged Sandwiched Cluster Incorporating Planar Hexanuclear Cobalt Ring and Bivacant Phosphotungstate.

    PubMed

    Guo, Ling-Yu; Zeng, Su-Yuan; Jagličić, Zvonko; Hu, Qi-Dong; Wang, Shi-Xuan; Wang, Zhi; Sun, Di

    2016-09-01

    A planar hexanuclear cobalt ring was clamped by two bivacant α1-[PW10O37](9-) with the assistance of the pyridazine bridges to form a novel sandwiched Co(II)-polyoxometalate cluster compound, [Na(H2O)6][Co3(OH) (pydz)4(H2O)7][Co6(PW10O37)2(pydz)4(H2O)6]·43H2O (1; pydz = pyridazine).This cluster was identified by X-ray single-crystal diffraction, elemental analysis, Fourier transform IR and UV-visible spectroscopies, and cyclic voltammetry (CV). Structural analysis reveals that 1 comprises a hexahydrated sodium, a trinuclear [Co3(OH) (pydz)4(H2O)7](5+) cationic cluster, and an anionic [Co6(PW10O37)2(pydz)4(H2O)6](6-) sandwiched cluster, thus giving an intrinsical intercluster compound. The isolation of such cluster was dependent on the in situ transformation of trivacant [α-P2W15O56](12-) to α1-[PW10O37](9-) under the hydrothermal condition. The CV shows reversible multielectron waves from the redox of W(VI) in 1. Cluster 1 exhibits remarkable electrocatalytic activity toward the reduction of nitrite. Magnetism studies indicated a weak anti-ferromagnetic exchange interaction between Co(II) ions within 1. PMID:27548500

  5. Dynamic response and optimal design of curved metallic sandwich panels under blast loading.

    PubMed

    Qi, Chang; Yang, Shu; Yang, Li-Jun; Han, Shou-Hong; Lu, Zhen-Hua

    2014-01-01

    It is important to understand the effect of curvature on the blast response of curved structures so as to seek the optimal configurations of such structures with improved blast resistance. In this study, the dynamic response and protective performance of a type of curved metallic sandwich panel subjected to air blast loading were examined using LS-DYNA. The numerical methods were validated using experimental data in the literature. The curved panel consisted of an aluminum alloy outer face and a rolled homogeneous armour (RHA) steel inner face in addition to a closed-cell aluminum foam core. The results showed that the configuration of a "soft" outer face and a "hard" inner face worked well for the curved sandwich panel against air blast loading in terms of maximum deflection (MaxD) and energy absorption. The panel curvature was found to have a monotonic effect on the specific energy absorption (SEA) and a nonmonotonic effect on the MaxD of the panel. Based on artificial neural network (ANN) metamodels, multiobjective optimization designs of the panel were carried out. The optimization results revealed the trade-off relationships between the blast-resistant and the lightweight objectives and showed the great use of Pareto front in such design circumstances.

  6. Design of Cellular Composite Sandwich Panels for Maximum Blast Resistance Via Energy Absorption

    NASA Astrophysics Data System (ADS)

    McConnell, Jennifer Righman; Su, Hong

    2016-06-01

    This paper presents a design methodology for optimizing the energy absorption under blast loads of cellular composite sandwich panels. A combination of dynamic finite element analysis (FEA) and simplified analytical modeling techniques are used. The analytical modeling calculates both the loading effects and structural response resulting from user-input charge sizes and standoff distances and offers the advantage of expediting iterative design processes. The FEA and the analytical model results are compared and contrasted then used to compare the energy response of various cellular composite sandwich panels under blast loads, where various core shapes and dimensions are the focus. As a result, it is concluded that the optimum shape consists of vertically-oriented webs while the optimum dimensions can be generally described as those which cause the most inelasticity without failure of the webs. These dimensions are also specifically quantified for select situations. This guidance is employed, along with the analytical method developed by the authors and considerations of the influences of material properties, to suggest a general design procedure that is a simple yet sufficiently accurate method for design. The suggested design approach is also demonstrated through a design example.

  7. Quantification of human tissue transglutaminase by a luminescence sandwich enzyme-linked immunosorbent assay.

    PubMed

    Wolf, Johannes; Lachmann, Ingolf; Wagner, Uta; Osman, Awad A; Mothes, Thomas

    2011-12-15

    Tissue transglutaminase (tTG) is a calcium-dependent enzyme that catalyzes crosslinking of peptidic glutamine residues with primary amines via isopeptide bonds and hydrolysis of ATP or GTP. The enzyme exerts a variety of functions at the cellular and tissue levels that may be disturbed in disease. Its role in pathoprocesses is poorly understood. For investigation of the involvement of tTG in disease, sensitive and specific assays should be available. We have developed the first sandwich enzyme-linked immunosorbent assay (ELISA) based on two monoclonal antibodies (mabs) against human tTG. tTG is captured by mab 3C10 and detected by biotinylated mab 10F3. After incubation with peroxidase-conjugated streptavidin, bound tTG is visualized by peroxidase reaction applying a luminescence substrate. The detection limit was 40 pg/ml. The assay was highly reproducible. Recovery of spiked tTG in crude samples was greater than 92%. The enzyme could be detected in cellular lysates and tissue homogenates of humans. The effect of typical effectors (retinoic acid and interferon-γ) on tTG expression could be demonstrated. A low signal was also obtained in mice samples, suggesting cross-reactivity of the mabs with murine tTG. The new sandwich ELISA may be successfully applied for investigation of physiological functions of tTG and of disorders associated with inadequate tTG expression.

  8. Scandium arene inverted-sandwich complexes supported by a ferrocene diamide ligand.

    PubMed

    Huang, Wenliang; Khan, Saeed I; Diaconescu, Paula L

    2011-07-13

    The synthesis and characterization of the first scandium arene inverted-sandwich complexes supported by a ferrocene diamide ligand (NN(fc)) are reported. Through the use of (NN(fc))ScI(THF)(2) as a precursor and potassium graphite (KC(8)) as a reducing agent, the naphthalene and anthracene complexes [(NN(fc))Sc](2)(μ-C(10)H(8)) and [(NN(fc))Sc](2)(μ-C(14)H(10)), respectively, were synthesized and isolated in moderate to high yields. Both molecular structures feature an inverted-sandwich geometry and exhibit short Fe-Sc distances. DFT calculations were employed to gain understanding of the electronic structures of these new scandium arene complexes. A variable-temperature NMR spectroscopic study of [(NN(fc))Sc](2)(μ-C(14)H(10)) indicated that two different structures are accessible in solution. Reactivity studies showed that the naphthalene complex [(NN(fc))Sc](2)(μ-C(10)H(8)) can be converted to the corresponding anthracene species [(NN(fc))Sc](2)(μ-C(14)H(10)) and that [(NN(fc))Sc](2)(μ-C(10)H(8)) can act as either a reductant or a proton acceptor. The reaction of [(NN(fc))Sc](2)(μ-C(10)H(8)) with excess pyridine led to a rare example of C-C bond formation between two pyridine rings at the para position.

  9. Elevated Temperature, Residual Compressive Strength of Impact-Damaged Sandwich Structure Manufactured Out-of-Autoclave

    NASA Technical Reports Server (NTRS)

    Grimsley, Brian W.; Sutter, James K.; Burke, Eric R.; Dixon, Genevieve D.; Gyekenyesi, Thomas G.; Smeltzer, Stanley S.

    2012-01-01

    Several 1/16th-scale curved sandwich composite panel sections of a 10 m diameter barrel were fabricated to demonstrate the manufacturability of large-scale curved sections using minimum gauge, [+60/-60/0]s, toughened epoxy composite facesheets co-cured with low density (50 kilograms per cubic meters) aluminum honeycomb core. One of these panels was fabricated out of autoclave (OoA) by the vacuum bag oven (VBO) process using Cycom(Registered Trademark) T40-800b/5320-1 prepreg system while another panel with the same lay-up and dimensions was fabricated using the autoclave-cure, toughened epoxy prepreg system Cycom(Registered Trademark) IM7/977-3. The resulting 2.44 m x 2 m curved panels were investigated by non-destructive evaluation (NDE) at NASA Langley Research Center (NASA LaRC) to determine initial fabrication quality and then cut into smaller coupons for elevated temperature wet (ETW) mechanical property characterization. Mechanical property characterization of the sandwich coupons was conducted including edge-wise compression (EWC), and compression-after-impact (CAI) at conditions ranging from 25 C/dry to 150 C/wet. The details and results of this characterization effort are presented in this paper.

  10. Open-sandwich enzyme immunoassay for one-step noncompetitive detection of corticosteroid 11-deoxycortisol.

    PubMed

    Ihara, Masaki; Suzuki, Tatsuya; Kobayashi, Norihiro; Goto, Junichi; Ueda, Hiroshi

    2009-10-15

    A noncompetitive immunoassay has the potential for improved sensitivity and working range compared with corresponding competitive assays. However, monovalent antigens with less than 1000 in molecular weight are not susceptible to sandwich assays due to their small size. As a noncompetitive immunoassay that can be performed with a clone of an antibody, an open-sandwich immunoassay (OS-IA) based on the antigen-dependent stabilization of the antibody variable region (V(H) + V(L)) was applied to the quantification of 11-deoxycortisol (11-DC; M(r) 346.5), a corticosteroid serving as a diagnostic index for pituitary-adrenal function, as a model target hapten. By one step OS-IA detection of enzyme-labeled V(H) fragment bound to immobilized V(L) in the presence of sample in microplate wells, 11-DC was measured with a femtomolar detection limit and the working range was wider than that with corresponding competitive assay. In addition, the selectivity against analogues was found almost identical to that of conventional assays. The effect of the mutagenesis of a V(H) residue at the V(H)/V(L) interface to reduce background signal was also shown, implying the wider application of OS-IA in small molecule analyses.

  11. Material Based Structure Design: Numerical Analysis Thermodynamic Response of Thermal Pyrolytic Graphite /Al Sandwich Composites

    NASA Astrophysics Data System (ADS)

    Wang, Junxia; Yan, Shilin; Yu, Dingshan

    2016-06-01

    Amine-grafted multiwalled carbon nanotubes (MWCNTs) based thermally conductive adhesive (TCA) was studied in the previous paper and applied here in thermal pyrolytic graphite (TPG)/Al radiator due to its high thermal conductivity, toughness and cohesiveness. In this paper, in an attempt to confirm the application of TCA to TPG/Al sandwich radiator, the thermodynamic response in TPG/Al sandwich composites associated with key material properties and structural design was investigated using finite element simulation with commercial available ANSYS software. The induced thermal stress in TCA layer is substantial due to the thermal expansion mismatch between Al plate and TPG. The maximum thermal stress is located near the edge of TCA layer with the von Mises stress value of 4.02 MPa and the shear stress value of 1.66 MPa. The reasonable adjustment of physical-mechanical properties including thermal conductivity, thermal expansion, Young,s modulus and the thickness of TCA layer, Al plate and TPG are beneficial for reducing the temperature of the top surface of the upper skin and their effects on the reduction of thermal structural response in some ways. These findings will highlight the structural optimization of TPG/Al radiator for future application.

  12. Sandwich-format 3D printed microfluidic mixers: a flexible platform for multi-probe analysis

    NASA Astrophysics Data System (ADS)

    Kise, Drew P.; Reddish, Michael J.; Dyer, R. Brian

    2015-12-01

    We report on a microfluidic mixer fabrication platform that increases the versatility and flexibility of mixers for biomolecular applications. A sandwich-format design allows the application of multiple spectroscopic probes to the same mixer. A polymer spacer is ‘sandwiched’ between two transparent windows, creating a closed microfluidic system. The channels of the mixer are defined by regions in the polymer spacer that lack material and therefore the polymer need not be transparent in the spectral region of interest. Suitable window materials such as CaF2 make the device accessible to a wide range of optical probe wavelengths, from the deep UV to the mid-IR. In this study, we use a commercially available 3D printer to print the polymer spacers to apply three different channel designs into the passive, continuous-flow mixer, and integrated them with three different spectroscopic probes. All three spectroscopic probes are applicable to each mixer without further changes. The sandwich-format mixer coupled with cost-effective 3D printed fabrication techniques could increase the applicability and accessibility of microfluidic mixing to intricate kinetic schemes and monitoring chemical synthesis in cases where only one probe technique proves insufficient.

  13. Plating a Dendrite-Free Lithium Anode with a Polymer/Ceramic/Polymer Sandwich Electrolyte.

    PubMed

    Zhou, Weidong; Wang, Shaofei; Li, Yutao; Xin, Sen; Manthiram, Arumugam; Goodenough, John B

    2016-08-01

    A cross-linked polymer containing pendant molecules attached to the polymer framework is shown to form flexible and low-cost membranes, to be a solid Li(+) electrolyte up to 270 °C, much higher than those based on poly(ethylene oxide), to be wetted by a metallic lithium anode, and to be not decomposed by the metallic anode if the anions of the salt are blocked by a ceramic electrolyte in a polymer/ceramic membrane/polymer sandwich electrolyte (PCPSE). In this sandwich architecture, the double-layer electric field at the Li/polymer interface is reduced due to the blocked salt anion transfer. The polymer layer adheres/wets the lithium metal surface and makes the Li-ion flux at the interface more homogeneous. This structure integrates the advantages of the ceramic and polymer. With the PCPSE, all-solid-state Li/LiFePO4 cells showed a notably high Coulombic efficiency of 99.8-100% over 640 cycles. PMID:27440104

  14. Dynamic Response and Optimal Design of Curved Metallic Sandwich Panels under Blast Loading

    PubMed Central

    Yang, Shu; Han, Shou-Hong; Lu, Zhen-Hua

    2014-01-01

    It is important to understand the effect of curvature on the blast response of curved structures so as to seek the optimal configurations of such structures with improved blast resistance. In this study, the dynamic response and protective performance of a type of curved metallic sandwich panel subjected to air blast loading were examined using LS-DYNA. The numerical methods were validated using experimental data in the literature. The curved panel consisted of an aluminum alloy outer face and a rolled homogeneous armour (RHA) steel inner face in addition to a closed-cell aluminum foam core. The results showed that the configuration of a “soft” outer face and a “hard” inner face worked well for the curved sandwich panel against air blast loading in terms of maximum deflection (MaxD) and energy absorption. The panel curvature was found to have a monotonic effect on the specific energy absorption (SEA) and a nonmonotonic effect on the MaxD of the panel. Based on artificial neural network (ANN) metamodels, multiobjective optimization designs of the panel were carried out. The optimization results revealed the trade-off relationships between the blast-resistant and the lightweight objectives and showed the great use of Pareto front in such design circumstances. PMID:25126606

  15. Hepatocyte function within a stacked double sandwich culture plate cylindrical bioreactor for bioartificial liver system.

    PubMed

    Xia, Lei; Arooz, Talha; Zhang, Shufang; Tuo, Xiaoye; Xiao, Guangfa; Susanto, Thomas Adi Kurnia; Sundararajan, Janani; Cheng, Tianming; Kang, Yuzhan; Poh, Hee Joo; Leo, Hwa Liang; Yu, Hanry

    2012-11-01

    Bioartificial liver (BAL) system is promising as an alternative treatment for liver failure. We have developed a bioreactor with stacked sandwich culture plates for the application of BAL. This bioreactor design addresses some of the persistent problems in flat-bed bioreactors through increasing cell packing capacity, eliminating dead flow, regulating shear stress, and facilitating the scalability of the bioreactor unit. The bioreactor contained a stack of twelve double-sandwich-culture plates, allowing 100 million hepatocytes to be housed in a single cylindrical bioreactor unit (7 cm of height and 5.5 cm of inner diameter). The serial flow perfusion through the bioreactor increased cell-fluid contact area for effective mass exchange. With the optimal perfusion flow rate, shear stress was minimized to achieve high and uniform cell viabilities across different plates in the bioreactor. Our results demonstrated that hepatocytes cultured in the bioreactor could re-establish cell polarity and maintain liver-specific functions (e.g. albumin and urea synthesis, phase I&II metabolism functions) for seven days. The single bioreactor unit can be readily scaled up to house adequate number of functional hepatocytes for BAL development.

  16. Measurement of relevant elastic and damping material properties in sandwich thick plates

    NASA Astrophysics Data System (ADS)

    Rébillat, Marc; Boutillon, Xavier

    2011-12-01

    An easy-to-implement method to measure relevant elastic and damping properties of the constituents of a sandwich structure, possibly with a heterogeneous core, is proposed. The method makes use of a one-point dynamical measurement on a thick-plate. The hysteretic model for each (possibly orthotropic) constituent is written generically as " E(1+jη)" for all mechanical parameters. The estimation method of the parameters relies on a mixed experimental/numerical procedure. The frequencies and dampings of the natural modes of the plate are obtained from experimental impulse responses by means of a high-resolution modal analysis technique. This allows for considerably more experimental data to be used. Numerical modes (frequencies, dampings, and modal shapes) are computed by means of an extended Rayleigh-Ritz procedure under the "light damping" hypothesis, for given values of the mechanical parameters. Minimising the differences between the modal characteristics yields an estimation of the values of the mechanical parameters describing the hysteretic behaviour. A sensitivity analysis assesses the reliability of the method for each parameter. Validations of the method are proposed by (a) applying it to virtual plates on which a finite-element model replaces the experimental modal analysis, (b) some comparisons with results obtained by static mechanical measurements, and (c) by comparing the results on different plates made of the same sandwich material.

  17. Compression After Impact on Honeycomb Core Sandwich Panels With Thin Facesheets. Part 1; Experiments

    NASA Technical Reports Server (NTRS)

    McQuigg, Thomas D.; Kapania, Rakesh K.; Scotti, Stephen J.; Walker, Sandra P.

    2012-01-01

    A two part research study has been completed on the topic of compression after impact (CAI) of thin facesheet honeycomb core sandwich panels. The research has focused on both experiments and analysis in an effort to establish and validate a new understanding of the damage tolerance of these materials. Part one, the subject of the current paper, is focused on the experimental testing. Of interest are sandwich panels, with aerospace applications, which consist of very thin, woven S2-fiberglass (with MTM45-1 epoxy) facesheets adhered to a Nomex honeycomb core. Two sets of specimens, which were identical with the exception of the density of the honeycomb core, were tested. Static indentation and low velocity impact using a drop tower are used to study damage formation in these materials. A series of highly instrumented CAI tests was then completed. New techniques used to observe CAI response and failure include high speed video photography, as well as digital image correlation (DIC) for full-field deformation measurement. Two CAI failure modes, indentation propagation, and crack propagation, were observed. From the results, it can be concluded that the CAI failure mode of these panels depends solely on the honeycomb core density.

  18. Interfacial Microstructure Evolution and Shear Strength of Titanium Sandwich Structures Fabricated by Brazing

    NASA Astrophysics Data System (ADS)

    Wang, Wentao; Fan, Minyu; Li, Jinlong; Tao, Jie

    2016-03-01

    The corrugated sandwich structure, consisting of a CP Ti (commercially pure titanium) core between two Ti-6Al-4V face sheets, was brazed using pasty Ti-37.5Zr-15Cu-10Ni as filler alloy, at the temperature of 870°C for 5, 10, 20, and 30 min. The effect of brazing time on the microstructure and elemental distribution of the brazed joints was examined by means of SEM, EDS, and XRD analyses. It was found that various intermetallic phases were formed in the brazed joints, following a brazing time of 5 min, and their contents were decreased by the increment of brazing time, while prolonged brazing time resulted in a fine, acicular Widmanstätten microstructure throughout the entire joint. In addition, shear testing was performed in the brazed corrugated specimens in order to indirectly assess the quality of the joints. The debonding between CP Ti and Ti-6Al-4V was observed in the specimen brazed for 5 min and the fracture of the CP Ti corrugated core occurred after 30 min of brazing time. Additionally, when brazed for 10 min or 20 min, brittle intermetallic compounds in the joints and the grain growth of the base metal were controllable. Therefore, the sandwich structures failed without debonding in the joints or fracture within the base metal, demonstrating a good combination of strength and ductility.

  19. Rotational Conformers of Group VI Metal (Cr, Mo, and w) Bis(mesitylene) Sandwich Complexes

    NASA Astrophysics Data System (ADS)

    Kumari, Sudesh; Yang, Dong-Sheng

    2010-06-01

    Group VI metal bis(mesitylene) sandwich complexes were produced by interactions between laser-vaporized metal atoms and mesitylene vapor in pulsed molecular beams, identified by photoionization time-of-flight mass spectrometry, and studied by pulsed-field-ionization zero-electron-kinetic-energy spectroscopy and density functional theory calculations. Although transition metal bis(arene) sandwiches may adopt eclipsed and staggered conformations, the group VI metal bis(mesitylene) complexes were determined to be in the eclipsed form. In this configuration, two rotational conformers, with methyl group dihedral angles of 0° and 60°, were identified for each complex. The adiabatic ionization energies of the 0° and 60° rotamers were measured to be 40557/40359, 42138/41697, and 41452/41000 cm-1 for the Cr, Mo, and W complexes, with the uncertainty of ˜{5 cm-1}. The ground electronic states of the 0°(D3h)/60° (D3d) rotamers are 1A'1/ 1A1g in the neutral form and ^2A'1/2A1g in the ionized form.

  20. Sandwich node architecture for agile wireless sensor networks for real-time structural health monitoring applications

    NASA Astrophysics Data System (ADS)

    Wang, Zi; Pakzad, Shamim; Cheng, Liang

    2012-04-01

    In recent years, wireless sensor network (WSN), as a powerful tool, has been widely applied to structural health monitoring (SHM) due to its low cost of deployment. Several commercial hardware platforms of wireless sensor networks (WSN) have been developed and used for structural monitoring applications [1,2]. A typical design of a node includes a sensor board and a mote connected to it. Sensing units, analog filters and analog-to-digital converters (ADCs) are integrated on the sensor board and the mote consists of a microcontroller and a wireless transceiver. Generally, there are a set of sensor boards compatible with the same model of mote and the selection of the sensor board depends on the specific applications. A WSN system based on this node lacks the capability of interrupting its scheduled task to start a higher priority task. This shortcoming is rooted in the hardware architecture of the node. The proposed sandwich-node architecture is designed to remedy the shortcomings of the existing one for task preemption. A sandwich node is composed of a sensor board and two motes. The first mote is dedicated to managing the sensor board and processing acquired data. The second mote controls the first mote via commands. A prototype has been implemented using Imote2 and verified by an emulation in which one mote is triggered by a remote base station and then preempts the running task at the other mote for handling an emergency event.

  1. High-quality sandwiched black phosphorus heterostructure and its quantum oscillations

    PubMed Central

    Chen, Xiaolong; Wu, Yingying; Wu, Zefei; Han, Yu; Xu, Shuigang; Wang, Lin; Ye, Weiguang; Han, Tianyi; He, Yuheng; Cai, Yuan; Wang, Ning

    2015-01-01

    Two-dimensional materials such as graphene and transition metal dichalcogenides have attracted great attention because of their rich physics and potential applications in next-generation nanoelectronic devices. The family of two-dimensional materials was recently joined by atomically thin black phosphorus which possesses high theoretical mobility and tunable bandgap structure. However, degradation of properties under atmospheric conditions and high-density charge traps in black phosphorus have largely limited its actual mobility thus hindering its future applications. Here, we report the fabrication of stable sandwiched heterostructures by encapsulating atomically thin black phosphorus between hexagonal boron nitride layers to realize ultra-clean interfaces that allow a high field-effect mobility of ∼1,350 cm2V−1 s−1 at room temperature and on–off ratios exceeding 105. At low temperatures, the mobility even reaches ∼2,700 cm2V−1 s−1 and quantum oscillations in black phosphorus two-dimensional hole gas are observed at low magnetic fields. Importantly, the sandwiched heterostructures ensure that the quality of black phosphorus remains high under ambient conditions. PMID:26099721

  2. High-quality sandwiched black phosphorus heterostructure and its quantum oscillations.

    PubMed

    Chen, Xiaolong; Wu, Yingying; Wu, Zefei; Han, Yu; Xu, Shuigang; Wang, Lin; Ye, Weiguang; Han, Tianyi; He, Yuheng; Cai, Yuan; Wang, Ning

    2015-06-23

    Two-dimensional materials such as graphene and transition metal dichalcogenides have attracted great attention because of their rich physics and potential applications in next-generation nanoelectronic devices. The family of two-dimensional materials was recently joined by atomically thin black phosphorus which possesses high theoretical mobility and tunable bandgap structure. However, degradation of properties under atmospheric conditions and high-density charge traps in black phosphorus have largely limited its actual mobility thus hindering its future applications. Here, we report the fabrication of stable sandwiched heterostructures by encapsulating atomically thin black phosphorus between hexagonal boron nitride layers to realize ultra-clean interfaces that allow a high field-effect mobility of ∼1,350 cm(2)V(-1) s(-1) at room temperature and on-off ratios exceeding 10(5). At low temperatures, the mobility even reaches ∼2,700 cm(2)V(-1) s(-1) and quantum oscillations in black phosphorus two-dimensional hole gas are observed at low magnetic fields. Importantly, the sandwiched heterostructures ensure that the quality of black phosphorus remains high under ambient conditions.

  3. Damage Behaviors of Foam Sandwiched Composite Materials Under Quasi-Static Three-point Bending

    NASA Astrophysics Data System (ADS)

    Zhang, Fa; Mohmmed, Ramadan; Sun, Baozhong; Gu, Bohong

    2013-12-01

    This paper reports the quasi-static three-point bending damage behaviors of foam sandwiched composites in finite element analyses (FEA) and experimental. Finite element calculations were performed to characterize the static response of foam sandwich composites with different ply angle face sheets. Quasi-static three-point bending tests were conducted with a MTS materials testing system to obtain the load-displacement curves and energy absorption under quasi-static bending. A crushable foam model was used in order to explore the mechanical behaviors of core materials, while the Hashin criterion was employed to predict the failure of the face sheets. The load-displacement curves show a satisfactory agreement between the experimental and numerical results. The finite element calculations can also be used to obtain the failure mode included the core damage, face sheet damage and face-core interface damage. It can be observed that the damage at the core material can be classified as either core cracking or core crushing. The damage of the face sheet was through matrix cracking and delamination, with fiber breakage. The significant indentation occurs as a result of the fiber breakage. The face-core interface crack was typically induced by the cracks initiated from the tensile side and propagated to the compressive side.

  4. Sandwich beam model for free vibration analysis of bilayer graphene nanoribbons with interlayer shear effect

    SciTech Connect

    Nazemnezhad, Reza E-mail: rnazemnezhad@du.ac.ir; Shokrollahi, Hassan; Hosseini-Hashemi, Shahrokh

    2014-05-07

    In this study, sandwich beam model (SM) is proposed for free vibration analysis of bilayer graphene nanoribbons (BLGNRs) with interlayer shear effect. This model also takes into account the intralayer (in-plane) stretch of graphene nanoribbons. The molecular dynamics (MD) simulations using the software LAMMPS and Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential are done to validate the accuracy of the sandwich model results. The MD simulation results include the two first frequencies of cantilever BLGNRs with different lengths and two interlayer shear moduli, i.e., 0.25 and 4.6 GPa. These two interlayer shear moduli, 0.25 and 4.6 GPa, can be obtained by sliding a small flake of graphene on a large graphene substrate when the parameter of E-LJ term in AIREBO potential, epsilon-CC, is set to be 2.84 and 45.44 meV, respectively. The SM results for a wide range of bending rigidity values show that the proposed model, i.e., the SM, predicts much better than the previous beam model in which the intralayer stretch is ignored. In addition, it is observed that the model can properly predict the natural frequencies of BLGNRs for various values of the bending rigidity and the interlayer shear modulus.

  5. Sandwich-format 3D printed microfluidic mixers: a flexible platform for multi-probe analysis

    PubMed Central

    Kise, Drew P; Reddish, Michael J; Dyer, R Brian

    2015-01-01

    We report on a microfluidic mixer fabrication platform that increases the versatility and flexibility of mixers for biomolecular applications. A sandwich-format design allows the application of multiple spectroscopic probes to the same mixer. A polymer spacer is ‘sandwiched’ between two transparent windows, creating a closed microfluidic system. The channels of the mixer are defined by regions in the polymer spacer that lack material and therefore the polymer need not be transparent in the spectral region of interest. Suitable window materials such as CaF2 make the device accessible to a wide range of optical probe wavelengths, from the deep UV to the mid-IR. In this study, we use a commercially available 3D printer to print the polymer spacers to apply three different channel designs into the passive, continuous-flow mixer, and integrated them with three different spectroscopic probes. All three spectroscopic probes are applicable to each mixer without further changes. The sandwich-format mixer coupled with cost-effective 3D printed fabrication techniques could increase the applicability and accessibility of microfluidic mixing to intricate kinetic schemes and monitoring chemical synthesis in cases where only one probe technique proves insufficient. PMID:26855478

  6. Shape and Stress Sensing of Multilayered Composite and Sandwich Structures Using an Inverse Finite Element Method

    NASA Technical Reports Server (NTRS)

    Cerracchio, Priscilla; Gherlone, Marco; Di Sciuva, Marco; Tessler, Alexander

    2013-01-01

    The marked increase in the use of composite and sandwich material systems in aerospace, civil, and marine structures leads to the need for integrated Structural Health Management systems. A key capability to enable such systems is the real-time reconstruction of structural deformations, stresses, and failure criteria that are inferred from in-situ, discrete-location strain measurements. This technology is commonly referred to as shape- and stress-sensing. Presented herein is a computationally efficient shape- and stress-sensing methodology that is ideally suited for applications to laminated composite and sandwich structures. The new approach employs the inverse Finite Element Method (iFEM) as a general framework and the Refined Zigzag Theory (RZT) as the underlying plate theory. A three-node inverse plate finite element is formulated. The element formulation enables robust and efficient modeling of plate structures instrumented with strain sensors that have arbitrary positions. The methodology leads to a set of linear algebraic equations that are solved efficiently for the unknown nodal displacements. These displacements are then used at the finite element level to compute full-field strains, stresses, and failure criteria that are in turn used to assess structural integrity. Numerical results for multilayered, highly heterogeneous laminates demonstrate the unique capability of this new formulation for shape- and stress-sensing.

  7. Development of honeycomb sandwich finite element modeling techniques for dynamic and static analysis

    NASA Astrophysics Data System (ADS)

    Spoonire, Ross A.

    2010-07-01

    Honeycomb sandwich core is typically modeled as an equivalent continuum for both static and dynamic analysis. The orthotropic material properties for such a continuum representation are difficult to predict. The objective of this work is to examine material and geometric parameters that affect the elastic and harmonic responses of honeycomb cores. A 3D shell FEA approach is adopted to model the core geometry. The model is compared to a typical homogeneous core finite-element representation in vibratory response. It is found that adhesive filleting can play a significant role in the response of honeycomb sandwich structure. Additionally, finite-element models using homogenized core approximations are shown to yield erroneous predictions for higher modes of vibration. Only through the modeling of actual honeycomb core geometry through finiteelement methods is it possible to predict higher modes. Vibration occurring strictly in the honeycomb cells can be observed by a tight band of resonances. This band occurs at different frequency ranges depending on the modeling technique. Achieving accurate homogeneous core model dynamic response for higher modes is restricted by computational inefficiency. Steady state harmonic analysis was only possible using the 3D shell core representation. The homogeneous core models were accurate in static shear and early modal response only. When it becomes necessary to predict shorter wavelengths of vibration, the homogeneous core models are either too computationally expensive or produce incorrect responses specifically with regard to modes isolated in the core.

  8. Fabrication of mucoadhesive chitosan coated polyvinylpyrrolidone/cyclodextrin/clotrimazole sandwich patches for oral candidiasis.

    PubMed

    Tonglairoum, Prasopchai; Ngawhirunpat, Tanasait; Rojanarata, Theerasak; Panomsuk, Suwanee; Kaomongkolgit, Ruchadaporn; Opanasopit, Praneet

    2015-11-01

    This study aims to fabricate clotrimazole (CZ)-composite sandwich nanofibers using electrospinning. The CZ-loaded polyvinylpyrrolidone (PVP)/hydroxypropyl-β-cyclodextrin (HPβCD) fiber was coated with chitosan-cysteine (CS-SH)/polyvinyl alcohol (PVA) to increase the mucoadhesive properties and to achieve a sustained release of the drug from the nanofibers. The nanofibers were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and X-ray diffractometry (XRD). The nanofibers mechanical and mucoadhesive properties, drug release, antifungal activity and cytotoxicity were also assessed. The fibers were in the nanoscale with good mucoadhesive properties. The XRPD revealed a molecular dispersion of amorphous CZ in the nanofibers. The initial fast release of CZ from the nanofibers was achieved. Moreover, the sandwich nanofibers coated for longer times resulted in slower release rates compared with the shorter coating times. The CZ-loaded nanofibers killed the Candida significantly faster than the commercial CZ lozenges at 5, 15 and 30 min and were safe for a 2-h incubation. Therefore, these nanofibers may be promising candidates for the treatment of oral candidiasis.

  9. Debonding Stress Concentrations in a Pressurized Lobed Sandwich-Walled Generic Cryogenic Tank

    NASA Technical Reports Server (NTRS)

    Ko, William L.

    2004-01-01

    A finite-element stress analysis has been conducted on a lobed composite sandwich tank subjected to internal pressure and cryogenic cooling. The lobed geometry consists of two obtuse circular walls joined together with a common flat wall. Under internal pressure and cryogenic cooling, this type of lobed tank wall will experience open-mode (a process in which the honeycomb is stretched in the depth direction) and shear stress concentrations at the junctures where curved wall changes into flat wall (known as a curve-flat juncture). Open-mode and shear stress concentrations occur in the honeycomb core at the curve-flat junctures and could cause debonding failure. The levels of contributions from internal pressure and temperature loading to the open-mode and shear debonding failure are compared. The lobed fuel tank with honeycomb sandwich walls has been found to be a structurally unsound geometry because of very low debonding failure strengths. The debonding failure problem could be eliminated if the honeycomb core at the curve-flat juncture is replaced with a solid core.

  10. Highly graphitized laterally interconnected SWCNT network synthesis via a sandwich-grown method

    NASA Astrophysics Data System (ADS)

    Teng, I.-Ju; Chen, Kai-Ling; Hsu, Hui-Lin; Jian, Sheng-Rui; Wang, Li-Chun; Chen, Jung-Hsuan; Wang, Wei-Hsiang; Kuo, Cheng-Tzu

    2011-04-01

    We present a sandwich-grown method for growing laterally interconnected single-walled carbon nanotube (SWCNT) networks with a high degree of graphitization by microwave plasma chemical vapour deposition (MPCVD). An Al2O3-supported Fe catalyst precursor layer deposited on an oxidized Si substrate with an upper Si cover is first pretreated in pure hydrogen, and then exposed to a gas mixture of methane/hydrogen for growth process at a lower growth temperature and a faster rate. The effects of various parameters, such as catalyst film thickness, gas flow rate, working pressure, growth time and plasma power, on the morphologies and structural characteristics of the SWCNT networks are investigated, and therefore provide the essential conditions for direct growth of laterally interconnected SWCNT networks. Analytical results demonstrate that the SWCNT-based lateral architecture comprises a mixture of graphene-sheet-wrapped catalyst particles and laterally interconnected nanotubes, isolated or branched or assembled into bundles. The results also show that the formation of the laterally interconnected SWCNT networks is related to the sandwich-like stack approach and the addition of an Al2O3 layer in the MPCVD process. The successful growth of lateral SWCNT networks provides new experimental information for simply and efficiently preparing lateral SWCNTs on unpatterned substrates, and opens a pathway to create network-structured nanotube-based devices.

  11. Sandwich Wound Closure Reduces the Risk of Cerebrospinal Fluid Leaks in Posterior Fossa Surgery

    PubMed Central

    Heymanns, Verena; Oseni, Abidemi W.; Alyeldien, Ameer; Maslehaty, Homajoun; Parvin, Richard; Scholz, Martin

    2016-01-01

    Posterior fossa surgery is demanding and hides a significant number of obstacles starting from the approach to the wound closure. The risk of cerebrospinal fluid (CSF) leakage in posterior fossa surgery given in the literature is around 8%. The present study aims to introduce a sandwich closure of the dura in posterior fossa surgery, which reduces significantly the number of CSF leaks (3.8%) in the patients treated in our department. Three hundred and ten patients treated in our hospital in the years 2009-2013 for posterior fossa pathologies were retrospectively evaluated. The dura closure method was as following: lyophilized dura put under the dura and sealed with fibrin glue and sutures, dura adapting stitches, TachoSil® (Takeda Pharma A/S, Roskilde, Denmark), Gelfoam® (Pfizer Inc., New York, NY, USA) and polymethylmethacrylate (osteoclastic craniotomy). The incidence of postsurgical complications associated with the dural closure like CSF leakage, infections, bleeding is evaluated. Only 3.8% of patients developed CSF leakage and only 0.5% needed a second surgery for CSF leakage closure. Two percent had a cerebellar bleeding with no need for re-operation and 3% had a wound infection treated with antibiotics. The sandwich wound closure we are applying for posterior fossa surgery in our patients correlates with a significant reduction of CSF leaks compared to the literature. PMID:27478578

  12. Optimal Design of Litz Wire Coils With Sandwich Structure Wirelessly Powering an Artificial Anal Sphincter System.

    PubMed

    Ke, Lei; Yan, Guozheng; Yan, Sheng; Wang, Zhiwu; Li, Xiaoyang

    2015-07-01

    Transcutaneous energy transfer system (TETS) is widely used to energize implantable biomedical devices. As a key part of the TETS, a pair of applicable coils with low losses, high unloaded Q factor, and strong coupling is required to realize an efficient TETS. This article presents an optimal design methodology of planar litz wire coils sandwiched between two ferrite substrates wirelessly powering a novel mechanical artificial anal sphincter system for treating severe fecal incontinence, with focus on the main parameters of the coils such as the wire diameter, number of turns, geometry, and the properties of the ferrite substrate. The theoretical basis of optimal power transfer efficiency in an inductive link was analyzed. A set of analytical expressions are outlined to calculate the winding resistance of a litz wire coil on ferrite substrate, taking into account eddy-current losses, including conduction losses and induction losses. Expressions that describe the geometrical dimension dependence of self- and mutual inductance are derived. The influence of ferrite substrate relative permeability and dimensions is also considered. We have used this foundation to devise an applicable coil design method that starts with a set of realistic constraints and ends with the optimal coil pair geometries. All theoretical predictions are verified with measurements using different types of fabricated coils. The results indicate that the analysis is useful for optimizing the geometry design of windings and the ferrite substrate in a sandwich structure as part of which, in addition to providing design insight, allows speeding up the system efficiency-optimizing design process.

  13. Face Sheet/Core Disbond Growth in Honeycomb Sandwich Panels Subjected to Ground-Air-Ground Pressurization and In-Plane Loading

    NASA Technical Reports Server (NTRS)

    Chen, Zhi M.; Krueger, Ronald; Rinker, Martin

    2015-01-01

    Typical damage modes in light honeycomb sandwich structures include face sheet/core disbonding and core fracture, both of which can pose a threat to the structural integrity of a component. These damage modes are of particular interest to aviation certification authorities since several in-service occurrences, such as rudder structural failure and other control surface malfunctions, have been attributed to face sheet/core disbonding. Extensive studies have shown that face sheet/core disbonding and core fracture can lead to damage propagation caused by internal pressure changes in the core. The increasing use of composite sandwich construction in aircraft applications makes it vitally important to understand the effect of ground-air-ground (GAG) cycles and conditions such as maneuver and gust loads on face sheet/core disbonding. The objective of the present study was to use a fracture mechanics based approach developed earlier to evaluate the loading at the disbond front caused by ground-air-ground pressurization and in-plane loading. A honeycomb sandwich panel containing a circular disbond at one face sheet/core interface was modeled with three-dimensional (3D) solid finite elements. The disbond was modeled as a discrete discontinuity and the strain energy release rate along the disbond front was computed using the Virtual Crack Closure Technique (VCCT). Special attention was paid to the pressure-deformation coupling which can decrease the pressure load within the disbonded sandwich section significantly when the structure is highly deformed. The commercial finite element analysis software, Abaqus/Standard, was used for the analyses. The recursive pressure-deformation coupling problem was solved by representing the entrapped air in the honeycomb cells as filled cavities in Abaqus/Standard. The results show that disbond size, face sheet thickness and core thickness are important parameters that determine crack tip loading at the disbond front. Further, the pressure

  14. Microbiological quality of take-away cooked rice and chicken sandwiches: effectiveness of food hygiene training of the management.

    PubMed

    Little, C L; Barnes, J; Mitchell, R T

    2002-12-01

    During August 2001 a microbiological study of ready-to-eat cooked rice from take-aways and of chicken sandwiches made on the premises from sandwich bars was undertaken. The intention was to identify risk factors in the production, storage and handling of cooked rice and sandwiches, and to establish their effect on microbiological quality. Examination of cooked rice revealed that the majority of samples (87%; 442 of 508) were of satisfactory/acceptable microbiological quality; 50 (10%) were unsatisfactory, and 16 (3%) were of unacceptable quality due to Bacillus cereus and/or other Bacillus spp in excess of 10(5) cfu/g. The microbiological quality of cooked rice was associated with cuisine type (p < 0.00001), rice type (p < 0.01), cooking (p < 0.01), serving methods (p < 0.00001), and management food hygiene training (p < 0.01). Examination of chicken sandwiches found that most (75%; 335 of 449) were of satisfactory/acceptable microbiological quality and 114 (25%) were unsatisfactory. Acceptable microbiological quality of sandwiches was associated with sandwich bars that had hazard analysis in place (p < 0.05). Smaller businesses, as indicated by Local Authority Inspectors' Consumer at Risk scores, were more likely to have samples classified as unsatisfactory or unacceptable compared to larger businesses (p < 0.001). The majority (90%) of premises had hand-washing facilities accessible and available for use, although only over half (55%) were correctly used as judged by the sampling officer. Where the manager of the premises had received some form of food hygiene training, food safety procedures such as the hazard analysis system were more likely to be in place (p < 0.0001). PMID:12564243

  15. Microbiological quality of take-away cooked rice and chicken sandwiches: effectiveness of food hygiene training of the management.

    PubMed

    Little, C L; Barnes, J; Mitchell, R T

    2002-12-01

    During August 2001 a microbiological study of ready-to-eat cooked rice from take-aways and of chicken sandwiches made on the premises from sandwich bars was undertaken. The intention was to identify risk factors in the production, storage and handling of cooked rice and sandwiches, and to establish their effect on microbiological quality. Examination of cooked rice revealed that the majority of samples (87%; 442 of 508) were of satisfactory/acceptable microbiological quality; 50 (10%) were unsatisfactory, and 16 (3%) were of unacceptable quality due to Bacillus cereus and/or other Bacillus spp in excess of 10(5) cfu/g. The microbiological quality of cooked rice was associated with cuisine type (p < 0.00001), rice type (p < 0.01), cooking (p < 0.01), serving methods (p < 0.00001), and management food hygiene training (p < 0.01). Examination of chicken sandwiches found that most (75%; 335 of 449) were of satisfactory/acceptable microbiological quality and 114 (25%) were unsatisfactory. Acceptable microbiological quality of sandwiches was associated with sandwich bars that had hazard analysis in place (p < 0.05). Smaller businesses, as indicated by Local Authority Inspectors' Consumer at Risk scores, were more likely to have samples classified as unsatisfactory or unacceptable compared to larger businesses (p < 0.001). The majority (90%) of premises had hand-washing facilities accessible and available for use, although only over half (55%) were correctly used as judged by the sampling officer. Where the manager of the premises had received some form of food hygiene training, food safety procedures such as the hazard analysis system were more likely to be in place (p < 0.0001).

  16. Improved protocols for protein and RNA isolation from three-dimensional collagen sandwich cultures of primary hepatocytes.

    PubMed

    Heidebrecht, F; Schulz, I; Keller, M; Behrens, S-E; Bader, A

    2009-10-01

    The sandwich culture is the most widely used long-term culture system for functional primary hepatocytes. Despite its advantages, the currently available protocols for protein and RNA extraction are either time-consuming or contain steps that may skewer the results. This paper describes improved protocols for RNA and protein extraction from sandwich cultures that are easy to perform, require short working time, and use no additional enzymatic reactions that could change the expression profile of the cells. The quality of the RNA is excellent, allowing also applications requiring high purity such as microarrays. In general, the protocols are suited for any cells in 3D collagen culture. PMID:19539596

  17. Use of a sandwich technique to control image geometry in clinical studies comparing intraoral xeroradiographs and E-speed films

    SciTech Connect

    Ludlow, J.B.; Hill, R.A.; Hayes, C.J.

    1988-05-01

    A method of superimposing a film on a xeroradiographic (XR) cassette for simultaneous intraoral exposure is evaluated for use as an imaging technique in clinical studies comparing Ektaspeed film and XR images. Sandwich images were indistinguishable from those produced by conventional technique. Pilot studies were conducted with 104 patients who had symptomatic dental problems. No significant differences were found in diagnostic usefulness or image quality between XR and film radiographs when sign test analysis was used. The sandwich technique yielded film and XR images with duplicate image geometry while reducing patient exposures to one half of that used in conventional image comparison protocols.

  18. Manifestation of the shape-memory effect in polyetherurethane cellular plastics, fabric composites, and sandwich structures under microgravity

    NASA Astrophysics Data System (ADS)

    Babaevskii, P. G.; Kozlov, N. A.; Agapov, I. G.; Reznichenko, G. M.; Churilo, N. V.; Churilo, I. V.

    2016-09-01

    The results of experiments that were performed to test the feasibility of creating sandwich structures (consisting of thin-layer sheaths of polymer composites and a cellular polymer core) with the shapememory effect as models of the transformable components of space structures have been given. The data obtained indicate that samples of sandwich structures under microgravity conditions on board the International Space Station have recovered their shape to almost the same degree as under terrestrial conditions, which makes it possible to recommend them for creating components of transformable space structures on their basis.

  19. Metal Construction

    NASA Technical Reports Server (NTRS)

    Verduzio, Rodolfo

    1922-01-01

    The future development of aerial navigation is closely connected with the condition of obtaining airplanes of great stability and sufficient strength. Different construction materials such as wood, aluminum, iron, and alloys are examined to determine which materials or combination of materials provides a greater coefficient of safety.

  20. Constructive Criticism.

    ERIC Educational Resources Information Center

    Lieberfeld, Lawrence

    1982-01-01

    Many crucial questions need to be answered before a college embarks on a construction project and makes a substantial financial commitment. Computer modeling techniques can be used to make even complex project feasibility analyses. Available from Peat, Marwick, Mitchell & Co., 345 Park Avenue, New York, NY 10154. (MSE)

  1. Abstract Constructions.

    ERIC Educational Resources Information Center

    Pietropola, Anne

    1998-01-01

    Describes a lesson designed to culminate a year of eighth-grade art classes in which students explore elements of design and space by creating 3-D abstract constructions. Outlines the process of using foam board and markers to create various shapes and optical effects. (DSK)

  2. Worldwide construction

    SciTech Connect

    Bell, L.

    1993-10-18

    Major construction projects in worldwide processing and pipelining are tested, showing capacities, contractors, estimated costs, and time of completion. Total capacity figure in Remarks and completion column includes capacity of project listed. The information is divided into petroleum refineries, petrochemical plants, sulfur recovery units, gas processing plants, related fuel plants (cogeneration, coal gasification, combined cycles), and pipeline companies.

  3. Benthic infaunal communities across the Weddell Sea Basin and South Sandwich Slope, Antarctica

    NASA Astrophysics Data System (ADS)

    Blake, James A.; Narayanaswamy, Bhavani E.

    2004-07-01

    The present study represents the first quantitative investigation of deep-sea benthic infauna in Antarctica. Box cores and multicores were used to collect sediment from 12 stations across the slope and abyssal basin of the Weddell Sea and the slope off the South Sandwich Islands, including sites in the South Sandwich Trench (6300 m). The multicore was a more efficient sampler than the box core. Nine phyla of invertebrates were found, dominated by annelids (67%), crustaceans (20%); other phyla (13%). A total of 117 taxa were identified to the species level: 72 were polychaetes; 45 were crustaceans. Many taxa are new to science. Highest densities were at the 1000 m depth on the western slope of the Weddell Sea (260 individuals per 0.1 m -2) and at ca. 2200 m on the South Sandwich Slope (132 individuals per 0.1 m -2); lowest densities were in the central Weddell Sea Basin (39 individuals per 0.1 m -2). Species richness and rarefaction analysis suggest that the fauna is undersampled. The 117 species identified in this study were represented by only 237 specimens, indicating that species were being added at a rate of one species for every two specimens collected. Rarefaction curves do not begin to reach an asymptote supporting high estimates of diversity. Some species appear to be limited to distinct zones in upper and middle slope depths, other species extend from the slope to the abyssal basin, and at least two species appear to be restricted to the abyssal basin. In general, the densities of infauna on the slopes surrounding the Weddell Sea Basin have lower densities than well-studied areas off North America. However, abyssal populations in Antarctica appear to have denser infaunal populations than those from off New England and the North Pacific Gyre. Productive surface waters of the Weddell Sea and subsequent sinking of phytoplankton to the seabed are probable reasons for the higher benthic productivity in Antarctic abyssal sediments. Similarity analyses were not

  4. A sandwich-designed temperature-gradient incubator for studies of microbial temperature responses.

    PubMed

    Elsgaard, Lars; Jørgensen, Leif Wagner

    2002-03-01

    A temperature-gradient incubator (TGI) is described, which produces a thermal gradient over 34 aluminium modules (15x30x5 cm) intersected by 2-mm layers of partly insulating graphite foil (SigraFlex Universal). The new, sandwich-designed TGI has 30 rows of six replicate sample wells for incubation of 28-ml test tubes. An electric plate heats one end of the TGI, and the other end is cooled by thermoelectric Peltier elements in combination with a liquid cooling system. The TGI is equipped with 24 calibrated Pt-100 temperature sensors and insulated by polyurethane plates. A PC-operated SCADA (Supervisory Control And Data Acquisition) software (Genesis 4.20) is applied for temperature control using three advanced control loops. The precision of the TGI temperature measurements was better than +/-0.12 degrees C, and for a 0-40 degrees C gradient, the temperature at the six replicate sample wells varied less than +/-0.04 degrees C. Temperatures measured in incubated water samples closely matched the TGI temperatures, which showed a linear relationship to the sample row number. During operation for 8 days with a gradient of 0-40 degrees C, the temperature at the cold end was stable within +/-0.02 degrees C, while the temperatures at the middle and the warm end were stable within +/-0.08 degrees C (n=2370). Using the new TGI, it was shown that the fine-scale (1 degrees C) temperature dependence of S(o) oxidation rates in agricultural soil (0-29 degrees C) could be described by the Arrhenius relationship. The apparent activation energy (E(a)) for S(o) oxidation was 79 kJ mol(-1), which corresponded to a temperature coefficient (Q(10)) of 3.1. These data demonstrated that oxidation of S(o) in soil is strongly temperature-dependent. In conclusion, the new TGI allowed a detailed study of microbial temperature responses as it produced a precise, stable, and certifiable temperature gradient by the new and combined use of sandwich-design, thermoelectric cooling, and advanced

  5. Artificial diet sandwiches reveal sub-social behavior in the coffee berry borer Hypothenemus hampei (Coleoptera: Scolytinae)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A diet sandwich, consisting of coffee berry borer artificial diet within two glass panes, has been developed to elucidate the behavior of the coffee berry borer, an insect that in nature spends most of its life cycle inside the coffee berry. Various types of behavior have been observed for the first...

  6. Exploratory Investigation of Failure Mechanisms in Transition Regions between Solid Laminates and X-cor(registered tm) Truss Sandwich

    NASA Technical Reports Server (NTRS)

    OBrien, T. Kevin; Paris, Isabelle L.

    2004-01-01

    Small sub-component specimens consisting of solid laminates at the ends that transition to X-cor(R) truss sandwich in the center, were tested in a combination of three point bending, uni-axial tension, and combined tension and bending. The failure process in the transition region was documented for each loading using digital video and high-resolution cameras. For the 3-point bending tests, most of the deformation occurred in the solid laminate regions on either end of the specimen. Some pin debonding from the skin of the X-cor(R) truss sandwich was observed in the transition region and was accompanied by audible "pings" throughout the loading. Tension loaded specimens failed in the sandwich skin in the middle of the gage length, accompanied by separation of the sandwich core from the back skin and by delamination between the top skin and bottom skin at the transition region. The pinging associated with pin debonding occurred as the load was increased. However, the frequency of the pinging exceeded any visual observations of pin debonding in the video of the transition region. For specimens tested in combined tension and bending, the greatest amount of pinging occurred during initial application of the axial load. High-resolution images in the transition region indicated that the pinging corresponded to pins debonding and buckling due to the through-thickness Poisson contraction of the specimen. This buckling continued to a much smaller extent as the transverse load was applied.

  7. Experimental, Theoretical and Numerical Investigation of the Flexural Behaviour of the Composite Sandwich Panels with PVC Foam Core

    NASA Astrophysics Data System (ADS)

    Mostafa, A.; Shankar, K.; Morozov, E. V.

    2014-08-01

    This study presents the main results of an experimental, theoretical and numerical investigation on the flexural behaviour and failure mode of composite sandwich panels primarily developed for marine applications. The face sheets of the sandwich panels are made up of glass fibre reinforced polymer (GFRP), while polyvinylchloride (PVC) foam was used as core material. Four-point bending test was carried out to investigate the flexural behaviour of the sandwich panel under quasi static load. The finite element (FE) analysis taking into account the cohesive nature of the skin-core interaction as well as the geometry and materials nonlinearity was performed, while a classical beam theory was used to estimate the flexural response. Although the FE results accurately represented the initial and post yield flexural response, the theoretical one restricted to the initial response of the sandwich panel due to the linearity assumptions. Core shear failure associate with skin-core debonding close to the loading points was the dominant failure mode observed experimentally and validated numerically and theoretically.

  8. Immunodiagnostic monoclonal antibody-based sandwich ELISA of fasciolosis by detection of Fasciola gigantica circulating fatty acid binding protein.

    PubMed

    Anuracpreeda, Panat; Chawengkirttikul, Runglawan; Sobhon, Prasert

    2016-09-01

    Up to now, parasitological diagnosis of fasciolosis is often unreliable and possesses low sensitivity. Hence, the detection of circulating parasite antigens is thought to be a better alternative for diagnosis of fasciolosis, as it reflects the real parasite burden. In the present study, a monoclonal antibody (MoAb) against recombinant Fasciola gigantica fatty acid binding protein (rFgFABP) has been produced. As well, a reliable sandwich enzyme-linked immunosorbent assay (sandwich ELISA) has been developed for the detection of circulating FABP in the sera of mice experimentally and cattle naturally infected with F. gigantica. MoAb 3A3 and biotinylated rabbit anti-recombinant FABP antibody were selected due to their high reactivities and specificities. The lower detection limit of sandwich ELISA was 5 pg mL-1, and no cross-reaction with other parasite antigens was observed. This assay could detect F. gigantica infection from day 1 post infection. In experimental mice, the sensitivity, specificity and accuracy of this assay were 93·3, 100 and 98·2%, while in natural cattle they were 96·7, 100 and 99·1%. Hence, this sandwich ELISA method showed high efficiencies and precisions for diagnosis of fasciolosis by F. gigantica. PMID:27312522

  9. Multiplexing in optical encryption by using an aperture system and a rotating sandwich random phase diffuser in the Fourier plane

    NASA Astrophysics Data System (ADS)

    Singh, Madan; Kumar, Arvind; Singh, Kehar

    2008-03-01

    In the present paper, we describe multiplexing in optical encryption of two-dimensional images, by using apertures and rotation of one of the constituent phase diffusers of a sandwich phase diffuser in the Fourier plane. The sandwich phase diffuser is made with two random constituent phase-diffusing surfaces sandwiched together. The apertures of different sizes and shapes are made with the help of 'paint brush' software. Simulation results are presented showing the effects of size, shape, and orientation of the apertures on the decrypted images obtained via multiplexing techniques. In addition to the results of using aperture systems in encryption and decryption, the results of rotation of one of the constituent phase diffusers in decryption are analyzed and used in multiplexing. Due to the use of aperture systems and the rotation of the constituent phase diffuser, the multiplexing capability of the system in encryption is enhanced along with the enhanced security due to using a sandwich diffuser. To evaluate the reliability of the technique, mean square error between the decrypted and the original image has been calculated.

  10. The Journey of a Sandwich: Computer-Based Laboratory Experiments about the Human Digestive System in High School Biology Teaching

    ERIC Educational Resources Information Center

    Sorgo, Andrej; Hajdinjak, Zdravka; Briski, Darko

    2008-01-01

    Teaching high school students about the digestive system can be a challenge for a teacher when s/he wants to overcome rote learning of facts without a deeper understanding of the physiological processes inside the alimentary tract. A series of model experiments illustrating the journey of a sandwich was introduced into teaching high school…

  11. The Role of Sandwich In-Service Program in Developing Agricultural Science Teachers in Delta State, Nigeria

    ERIC Educational Resources Information Center

    Ikeoji, Canice N.; Agwubike, Christian C.; Ideh, Victor

    2007-01-01

    This study examined the role of the sandwich in-service educational program of Delta State University, Abraka in developing agricultural science teachers in the state. Data were collected from 895 agricultural science teachers who completed the program between 1989-2004. However, response to the questionnaire was by 391 in-service agricultural…

  12. Finite element analysis of hypervelocity impact behaviour of CFRP-Al/HC sandwich panel

    NASA Astrophysics Data System (ADS)

    Phadnis, Vaibhav A.; Silberschmidt, Vadim V.

    2015-09-01

    The mechanical response of CFRP-Al/HC (carbon fibre-reinforced/epoxy composite face sheets with Al honeycomb core) sandwich panels to hyper-velocity impact (up to 1 km/s) is studied using a finite-element model developed in ABAQUS/Explicit. The intraply damage of CFRP face sheets is analysed by mean of a user-defined material model (VUMAT) employing a combination of Hashin and Puck criteria, delamination modelled using cohesive-zone elements. The damaged Al/HC core is assessed on the basis of a Johnson Cook dynamic failure model while its hydrodynamic response is captured using the Mie-Gruneisen equation of state. The results obtained with the developed finite-element model showed a reasonable correlation to experimental damage patterns. The surface peeling of both face sheets was evident, with a significant delamination around the impact location accompanied by crushing HC core.

  13. Thermal stability tests of CFRP sandwich panels for far infrared astronomy

    NASA Technical Reports Server (NTRS)

    Hoffmann, W. F.; Helwig, G.; Scheulen, D.

    1986-01-01

    An account is given of fabrication methods and low temperature figure tests for CFRP sandwich panels, in order to ascertain their applicability to ultralightweight 3-m aperture primary mirrors for balloon-borne sub-mm and far-IF telescopes that must maintain a 1-2 micron rms surface figure accuracy at -40 to -50 C. Optical figure measurements on the first two of a series of four 0.5-m test panels, replicated to a spherical surface, show a radius-of-curvature change and astigmatism down to -60 C; this approximately follows the composite's theoretical predictions and implies that material and process control is excellent, so that the large scale changes observed can be compensated for.

  14. Sandwich enzyme-linked immunosorbent assay for detection of excretory secretory antigens in humans with fascioliasis.

    PubMed Central

    Espino, A M; Finlay, C M

    1994-01-01

    A sandwich enzyme-linked immunosorbent assay has been developed for the detection of Fasciola hepatica excretory secretory (ES) antigens in stool specimens of infected humans. The assay uses antibodies against F. hepatica ES antigens. A monoclonal antibody (ES78, mouse immunoglobulin G2a) was used to capture ES antigens, and a rabbit polyclonal antibody, peroxidase conjugate, was used to identify ES antigens. Thirteen of 14 patients with parasitological evidence of fascioliasis had a detectable concentration of ES antigens (more than 15 ng/ml). None of the stool specimens from controls and from patients with parasites other than F. hepatica showed a positive reaction, suggesting the absence of cross-reactions in this assay. When the 14 patients were retested 2 months after treatment, all of the specimens from the 11 parasitologically cured patients were negative by the antigen detection assay while the specimens from the 3 patients with persisting F. hepatica eggs in their stools remained positive. PMID:8126178

  15. The conformal method and the conformal thin-sandwich method are the same

    NASA Astrophysics Data System (ADS)

    Maxwell, David

    2014-07-01

    The conformal method developed in the 1970s and the more recent Lagrangian and Hamiltonian conformal thin-sandwich methods are techniques for finding solutions of the Einstein constraint equations. We show that they are manifestations of a single conformal method: there is a straightforward way to convert back and forth between the parameters for these methods so that the corresponding solutions of the Einstein constraint equations agree. The unifying idea is the need to clearly distinguish tangent and cotangent vectors to the space of conformal classes on a manifold, and we introduce a vocabulary for working with these objects without reference to a particular representative background metric. As a consequence of these conceptual advantages, we demonstrate how to strengthen previous near-CMC (constant mean curvature) existence and non-existence theorems for the original conformal method to include metrics with scalar curvatures that change sign.

  16. Fabrication method for cores of structural sandwich materials including star shaped core cells

    DOEpatents

    Christensen, Richard M.

    1997-01-01

    A method for fabricating structural sandwich materials having a core pattern which utilizes star and non-star shaped cells. The sheets of material are bonded together or a single folded sheet is used, and bonded or welded at specific locations, into a flat configuration, and are then mechanically pulled or expanded normal to the plane of the sheets which expand to form the cells. This method can be utilized to fabricate other geometric cell arrangements than the star/non-star shaped cells. Four sheets of material (either a pair of bonded sheets or a single folded sheet) are bonded so as to define an area therebetween, which forms the star shaped cell when expanded.

  17. Fabrication method for cores of structural sandwich materials including star shaped core cells

    DOEpatents

    Christensen, R.M.

    1997-07-15

    A method for fabricating structural sandwich materials having a core pattern which utilizes star and non-star shaped cells is disclosed. The sheets of material are bonded together or a single folded sheet is used, and bonded or welded at specific locations, into a flat configuration, and are then mechanically pulled or expanded normal to the plane of the sheets which expand to form the cells. This method can be utilized to fabricate other geometric cell arrangements than the star/non-star shaped cells. Four sheets of material (either a pair of bonded sheets or a single folded sheet) are bonded so as to define an area therebetween, which forms the star shaped cell when expanded. 3 figs.

  18. Approximate methods for predicting interlaminar shear stiffness of laminated and sandwich beams

    NASA Astrophysics Data System (ADS)

    Roy, Ajit K.; Verchery, Georges

    1993-01-01

    Several approximate closed form expressions exist in the literature for predicting the effective interlaminar shear stiffness (G13) of laminated composite beams. The accuracy of these approximate methods depends on the number of layers present in the laminated beam, the relative layer thickness and layer stacking sequence, and the beam length to depth ratio. The objective of this work is to evaluate approximate methods for predicting G13 by comparing its predictions with that of an accurate method, and then find the range where the simple closed form expressions for predicting G13 can be applicable. A comparative study indicates that all the approximate methods included here give good prediction of G13 when the laminate is made of a large number of repeated sublaminates. Further, the parabolic shear stress distribution function yields a reasonably accurate prediction of G13 even for a relatively small number of layers in the laminate. A similar result is also presented for sandwich beams.

  19. New theories for symmetric/unsymmetric composite and sandwich beams with C0 finite elements

    NASA Astrophysics Data System (ADS)

    Manjunatha, B. S.; Kant, T.

    A new set of higher order theories for the analysis of composite and sandwich beams by using C0 finite elements is presented. These theories incorporate the more realistic non-linear variation of displacements through the beam thickness, thus eliminating the use of shear correction coefficients. Discrete Lagrangian four-noded cubic element models having five, six, and seven degrees of freedom per node are used. The computer program developed incorporates the realistic prediction of interlaminar stresses from equilibrium equations. By comparing the results obtained with the elasticity solution and the classical plate theory, it is shown that the present higher order theories give a much better approximation to the behavior of thick to thin laminated composite beams.

  20. High rate lithium-sulfur battery enabled by sandwiched single ion conducting polymer electrolyte

    PubMed Central

    Sun, Yubao; Li, Gai; Lai, Yuanchu; Zeng, Danli; Cheng, Hansong

    2016-01-01

    Lithium-sulfur batteries are highly promising for electric energy storage with high energy density, abundant resources and low cost. However, the battery technologies have often suffered from a short cycle life and poor rate stability arising from the well-known “polysulfide shuttle” effect. Here, we report a novel cell design by sandwiching a sp3 boron based single ion conducting polymer electrolyte film between two carbon films to fabricate a composite separator for lithium-sulfur batteries. The dense negative charges uniformly distributed in the electrolyte membrane inherently prohibit transport of polysulfide anions formed in the cathode inside the polymer matrix and effectively blocks polysulfide shuttling. A battery assembled with the composite separator exhibits a remarkably long cycle life at high charge/discharge rates. PMID:26898772

  1. Double-antibody sandwich enzyme-linked immunosorbent assay for cellobiohydrolase I

    SciTech Connect

    Riske, F.J.; Eveleigh, D.E.; MacMillan, J.D. )

    1990-11-01

    A double-antibody sandwich enzyme-linked immunosorbent assay was developed for quantifying cellobiohydrolase I (CBH I) in crude preparations of the cellulase complex from Trichoderma reesei. The other enzymes (endoglucanase and {beta}-glucosidase) in this complex and other ingredients in culture broth did not interfere with this assay. The antibody configuration that resulted in the highest specificity for the assay of CBH I employed a monoclonal antibody to coat wells in polystyrene plates and peroxidase-labeled polyclonal antibody to detect cellobiohydrolase bound to the immobilized monoclonal antibody. Previously, procedures have not been available for the direct assay of CBH I activity in the presence of the other enzymes in the complex, and current indirect procedures are cumbersome and inaccurate. The direct procedure described here is highly specific for CBH I and useful for quantifying this enzyme in the range of 0.1 to 0.8 {mu}g/ml.

  2. Semi-flexible gas-insulated transmission line using sandwiched discs for intermittent flexing joints

    DOEpatents

    Kommineni, Prasad R.

    1983-02-15

    A gas-insulated transmission line includes an outer sheath, an inner conductor, an insulating gas electrically insulating the inner conductor from the outer sheath, and insulating supports insulatably supporting the inner conductor within the outer sheath. The inner conductor is provided with flexibility by the use of main conductor sections which are joined together through a conductor hub section and flexible flexing elements. Stress shields are provided to control the electric field at the locations of the conductor hub sections where the insulating supports are contacting the inner conductor. The flexing elements are formed by sandwiching together, by fusing, a pair of thin hollow discs which are fixedly secured to both the main conductor sections and the conductor hub section.

  3. Semi-flexible gas-insulated transmission line using sandwiched discs for intermittent flexing joints

    DOEpatents

    Kommineni, P.R.

    1983-02-15

    A gas-insulated transmission line includes an outer sheath, an inner conductor, an insulating gas electrically insulating the inner conductor from the outer sheath, and insulating supports insulatably supporting the inner conductor within the outer sheath. The inner conductor is provided with flexibility by the use of main conductor sections which are joined together through a conductor hub section and flexible flexing elements. Stress shields are provided to control the electric field at the locations of the conductor hub sections where the insulating supports are contacting the inner conductor. The flexing elements are formed by sandwiching together, by fusing, a pair of thin hollow discs which are fixedly secured to both the main conductor sections and the conductor hub section. 4 figs.

  4. Exact dynamic stiffness matrix for flexural vibration of three-layered sandwich beams

    NASA Astrophysics Data System (ADS)

    Howson, W. P.; Zare, A.

    2005-04-01

    An exact dynamic member stiffness matrix (exact finite element), which defines the flexural motion of a three-layered sandwich beam with unequal faceplates, is developed from the closed form solution of the governing differential equation. This enables the powerful modelling features associated with the finite element technique to be utilised, including the ability to account for nodal masses, spring support stiffnesses and non-classical boundary conditions. However, such a formulation necessitates the solution of a transcendental eigenvalue problem. This is accomplished using the Wittrick-Williams algorithm, which enables the required natural frequencies to be converged upon to any required accuracy with the certain knowledge that none have been missed. The accuracy of the method is confirmed by comparison with three sets of published results and a final example indicates its range of application.

  5. Sandwich-like mesoporous graphene@magnetite@carbon nanosheets for high-rate lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Zhong, Yongming; Zhou, Xunfu; Li, Xin; Zhang, Shengsen; Liu, Yingju; Yu, Xiaoyuan; Wang, Hongqiang; Li, Qingyu; Fang, Yueping; Li, Jun

    2016-07-01

    Sandwich-like mesoporous GS@Fe3O4@C nanosheets with a 2D nanoarchitecture have been successfully synthesized by one-step solvothermal treatment. Such type of 2D nanoarchitecture is made up of a number of Fe3O4 nanoparticles uniformly grown on a graphene sheet and an even amorphous carbon layer covering on their surface. The Li-cycling properties of GS@Fe3O4@C nanosheets have been evaluated by galvanostatic discharge-charge cycling and impedance spectroscopy. Results indicate that the GS@Fe3O4@C nanosheets with about 5 wt % of graphene content provides a very high discharge capacity of 913.2 mAh g-1 at a current densities of 200 mA g-1 after 100 cycles and reveals a stable discharge capacity of 483.2 mAh g-1 at a rate of 1600 mA g-1.

  6. Fabrication and development of several heat pipe honeycomb sandwich panel concepts. [airframe integrated scramjet engine

    NASA Technical Reports Server (NTRS)

    Tanzer, H. J.

    1982-01-01

    The feasibility of fabricating and processing liquid metal heat pipes in a low mass honeycomb sandwich panel configuration for application on the NASA Langley airframe-integrated Scramjet engine was investigated. A variety of honeycomb panel facesheet and core-ribbon wick concepts was evaluated within constraints dictated by existing manufacturing technology and equipment. The chosen design consists of an all-stainless steel structure, sintered screen facesheets, and two types of core-ribbon; a diffusion bonded wire mesh and a foil-screen composite. Cleaning, fluid charging, processing, and process port sealing techniques were established. The liquid metals potassium, sodium and cesium were used as working fluids. Eleven honeycomb panels 15.24 cm X 15.24 cm X 2.94 cm were delivered to NASA Langley for extensive performance testing and evaluation; nine panels were processed as heat pipes, and two panels were left unprocessed.

  7. Load-dependent Optimization of Honeycombs for Sandwich Components - New Possibilities by Using Additive Layer Manufacturing

    NASA Astrophysics Data System (ADS)

    Riss, Fabian; Schilp, Johannes; Reinhart, Gunther

    Due to their feasible geometric complexity, additive layer manufacturing (ALM) processes show a highpotential for the production of lightweight components.Therefore, ALM processes enable the realization of bionic-designedcomponents like honeycombs, which are optimized depending upon load and outer boundary conditions.This optimization is based on a closed-loop, three-steps methodology: At first, each honeycomb is conformed to the surface of the part. Secondly, the structure is optimizedfor lightweight design.It is possible to achieve a homogeneous stress distribution in the part by varying the wall thickness, honeycombdiameter and the amount of honeycombs, depending on the subjected stresses and strains. At last, the functional components like threads or bearing carriers are integrated directly into the honeycomb core.Using all these steps as an iterative process, it is possible to reduce the mass of sandwich components about 50 percent compared to conventional approaches.

  8. Multi-response parametric optimization in drilling of bamboo/Kevlar fiber reinforced sandwich composite

    NASA Astrophysics Data System (ADS)

    Singh, Thingujam Jackson; Samanta, Sutanu

    2016-09-01

    In the present work an attempt was made towards parametric optimization of drilling bamboo/Kevlar K29 fiber reinforced sandwich composite to minimize the delamination occurred during the drilling process and also to maximize the tensile strength of the drilled composite. The spindle speed and the feed rate of the drilling operation are taken as the input parameters. The influence of these parameters on delamination and tensile strength of the drilled composite studied and analysed using Taguchi GRA and ANOVA technique. The results show that both the response parameters i.e. delamination and tensile strength are more influenced by feed rate than spindle speed. The percentage contribution of feed rate and spindle speed on response parameters are 13.88% and 81.74% respectively.

  9. Quantum transport effects in copper(II) phthalocyanine sandwiched between gold nanoelectrodes.

    PubMed

    Tada, Tomofumi; Hamayama, Shinya; Kondo, Masakazu; Yoshizawa, Kazunari

    2005-06-30

    The electrical transmission of copper(II) phthalocyanine (CuPc) sandwiched between gold nanoelectrodes is studied on the basis of the Green function formalism coupled with the Gaussian-broadening technique. In the Au-CuPc-Au junction, broadened density of states (DOS) of the Au chains is defined as continuous DOS of electrodes to calculate the Green function of the electrodes. Two peaks of the transmission function found in the vicinity of the Fermi level are analyzed in terms of molecular orbitals (MOs). A convenient procedure to analyze MO contribution to a transmission peak is proposed. It is found that (I) symmetry-matched interactions between CuPc and the gold nanoelectrodes are important to the enhancement of the transmission function and (II) the nanoelectrodes have almost no effect on the electronic states of CuPc.

  10. [Chest Wall Reconstruction Using Titanium Plates Sandwiched Between Sheets after Resection of Chest Wall Chondrosarcoma].

    PubMed

    Endoh, Makoto; Oizumi, Hiroyuki; Kato, Hirohisa; Suzuki, Jun; Watarai, Hikaru; Hamada, Akira; Suzuki, Katsuyuki; Takahashi, Ai; Nakahashi, Kenta; Sugawara, Masato; Tsuchiya, Takashi; Sadahiro, Mitsuaki

    2016-07-01

    Extensive chest wall resection carries the risk of difficult reconstruction and surgical complications. We report our experience on chest wall reconstruction using titanium plates for a wide thoracic defect after tumor resection. A 74-year-old man was diagnosed with chondrosarcoma of the 6th rib on the right. He needed extensive chest wall resection because of skip lesions on 4th rib noted on operative inspection, leaving a defect measuring 33 × 20 cm. Reconstruction using 5 transverse titanium plates sandwiched between an expanded polytetrafluoroethylene patch and a polypropylene mesh sheet stabilized the chest wall. This reconstruction allowed successful separation from ventilatory support after operation. The postoperative course was uneventful, and he was discharged on postoperative day 20. The advantages of this form of reconstruction over conventional prostheses are rigidity, and stability and usability. PMID:27365062

  11. Effects of valence, geometry and electronic correlations on transport in transition metal benzene sandwich molecules

    NASA Astrophysics Data System (ADS)

    Karolak, M.; Jacob, D.

    2016-11-01

    We study the impact of the valence and the geometry on the electronic structure and transport properties of different transition metal-benzene sandwich molecules bridging the tips of a Cu nanocontact. Our density-functional calculations show that the electronic transport properties of the molecules depend strongly on the molecular geometry which can be controlled by the nanocontact tips. Depending on the valence of the transition metal center certain molecules can be tuned in and out of half-metallic behaviour facilitating potential spintronics applications. We also discuss our results in the framework of an Anderson impurity model, indicating cases where the inclusion of local correlations alters the ground state qualitatively. For Co and V centered molecules we find indications of an orbital Kondo effect.

  12. Sizing Single Cantilever Beam Specimens for Characterizing Facesheet/Core Peel Debonding in Sandwich Structure

    NASA Technical Reports Server (NTRS)

    Ratcliffe, James G.

    2010-01-01

    This paper details part of an effort focused on the development of a standardized facesheet/core peel debonding test procedure. The purpose of the test is to characterize facesheet/core peel in sandwich structure, accomplished through the measurement of the critical strain energy release rate associated with the debonding process. The specific test method selected for the standardized test procedure utilizes a single cantilever beam (SCB) specimen configuration. The objective of the current work is to develop a method for establishing SCB specimen dimensions. This is achieved by imposing specific limitations on specimen dimensions, with the objectives of promoting a linear elastic specimen response, and simplifying the data reduction method required for computing the critical strain energy release rate associated with debonding. The sizing method is also designed to be suitable for incorporation into a standardized test protocol. Preliminary application of the resulting sizing method yields practical specimen dimensions.

  13. Flotation Immunoassay: Masking the Signal from Free Reporters in Sandwich Immunoassays.

    PubMed

    Chen, Hui; Hagström, Anna E V; Kim, Jinsu; Garvey, Gavin; Paterson, Andrew; Ruiz-Ruiz, Federico; Raja, Balakrishnan; Strych, Ulrich; Rito-Palomares, Marco; Kourentzi, Katerina; Conrad, Jacinta C; Atmar, Robert L; Willson, Richard C

    2016-04-14

    In this work, we demonstrate that signal-masking reagents together with appropriate capture antibody carriers can eliminate the washing steps in sandwich immunoassays. A flotation immunoassay (FI) platform was developed with horseradish peroxidase chemiluminescence as the reporter system, the dye Brilliant Blue FCF as the signal-masking reagent, and buoyant silica micro-bubbles as the capture antibody carriers. Only reporters captured on micro-bubbles float above the dye and become visible in an analyte-dependent manner. These FIs are capable of detecting proteins down to attomole levels and as few as 10(6) virus particles. This signal-masking strategy represents a novel approach to simple, sensitive and quantitative immunoassays in both laboratory and point-of-care settings.

  14. Frequency analysis of curved nano-sandwich structure based on a nonlocal model

    NASA Astrophysics Data System (ADS)

    Rahmani, O.; Hosseini, S. A. H.; Hayati, H.

    2016-04-01

    In this paper, we study the vibration of curved nano-sandwich (CNS) with considering the influence of core shear based on the Eringen nonlocal theory. The equation of motion is derived and exact solution for the natural frequencies of CNS is presented. The proposed nonlocal model includes a material length scale parameter that can capture the size effect in CNS beam. The effects of important parameters, such as the thickness to length ratio, nonlocal parameter and mode number on the frequencies of CNS are investigated. The result of our research shows that as the opening angle increases, the amount of natural frequencies decrease. We have additionally validate, our results against previous research works which showed good agreement.

  15. An Investigation of The Reticulated Foam - Perforated Steel Sheet Sandwich Structure As A Blast Mitigation Media

    NASA Astrophysics Data System (ADS)

    Nguyen, Thuy-Tien Ngoc; Proud, William; Institute of Shock Physics, Imperial College London Collaboration; Royal British Legion CentreBlast Injury Studies at Imperial College London Collaboration

    2015-06-01

    Explosions have always been the main cause of injuries during battles and conflicts, with improvised explosive devices (IEDs) becoming more and more common nowadays. In this paper, the interaction between blast waves and sandwich structures of reticulated foam and perforated sheets, with varying thickness and configuration, is studied using an air-driven shock tube apparatus. The mitigation effects for primary blast injuries of these structures are discussed in terms of pulse shape, pressure magnitude as well as shock impulse. Schlieren photography together with other high-speed imaging was also used to visually investigate the matter. The results show that lower open area of perforated sheet and increased thickness of foam offer best protection. However, below a threshold thickness, no mitigation is seen. The Institute of Shock Physics acknowledges the support of AWE, Aldermaston, UK and Imperial College London. The Centre for Blast Injury Studies acknowledges the support of the Royal British Legion and Imperial College London.

  16. Flotation Immunoassay: Masking the Signal from Free Reporters in Sandwich Immunoassays.

    PubMed

    Chen, Hui; Hagström, Anna E V; Kim, Jinsu; Garvey, Gavin; Paterson, Andrew; Ruiz-Ruiz, Federico; Raja, Balakrishnan; Strych, Ulrich; Rito-Palomares, Marco; Kourentzi, Katerina; Conrad, Jacinta C; Atmar, Robert L; Willson, Richard C

    2016-01-01

    In this work, we demonstrate that signal-masking reagents together with appropriate capture antibody carriers can eliminate the washing steps in sandwich immunoassays. A flotation immunoassay (FI) platform was developed with horseradish peroxidase chemiluminescence as the reporter system, the dye Brilliant Blue FCF as the signal-masking reagent, and buoyant silica micro-bubbles as the capture antibody carriers. Only reporters captured on micro-bubbles float above the dye and become visible in an analyte-dependent manner. These FIs are capable of detecting proteins down to attomole levels and as few as 10(6) virus particles. This signal-masking strategy represents a novel approach to simple, sensitive and quantitative immunoassays in both laboratory and point-of-care settings. PMID:27075635

  17. An efficient finite element with layerwise mechanics for smart piezoelectric composite and sandwich shallow shells

    NASA Astrophysics Data System (ADS)

    Yasin, M. Yaqoob; Kapuria, S.

    2014-01-01

    In this work, we present a new efficient four-node finite element for shallow multilayered piezoelectric shells, considering layerwise mechanics and electromechanical coupling. The laminate mechanics is based on the zigzag theory that has only seven kinematic degrees of freedom per node. The normal deformation of the piezoelectric layers under the electric field is accounted for without introducing any additional deflection variables. A consistent quadratic variation of the electric potential across the piezoelectric layers with the provision of satisfying the equipotential condition of electroded surfaces is adopted. The performance of the new element is demonstrated for the static response under mechanical and electric potential loads, and for free vibration response of smart shells under different boundary conditions. The predictions are found to be very close to the three dimensional piezoelasticity solutions for hybrid shells made of not only single-material composite substrates, but also sandwich substrates with a soft core for which the equivalent single layer (ESL) theories perform very badly.

  18. WORM ALGORITHM PATH INTEGRAL MONTE CARLO APPLIED TO THE 3He-4He II SANDWICH SYSTEM

    NASA Astrophysics Data System (ADS)

    Al-Oqali, Amer; Sakhel, Asaad R.; Ghassib, Humam B.; Sakhel, Roger R.

    2012-12-01

    We present a numerical investigation of the thermal and structural properties of the 3He-4He sandwich system adsorbed on a graphite substrate using the worm algorithm path integral Monte Carlo (WAPIMC) method [M. Boninsegni, N. Prokof'ev and B. Svistunov, Phys. Rev. E74, 036701 (2006)]. For this purpose, we have modified a previously written WAPIMC code originally adapted for 4He on graphite, by including the second 3He-component. To describe the fermions, a temperature-dependent statistical potential has been used. This has proven very effective. The WAPIMC calculations have been conducted in the millikelvin temperature regime. However, because of the heavy computations involved, only 30, 40 and 50 mK have been considered for the time being. The pair correlations, Matsubara Green's function, structure factor, and density profiles have been explored at these temperatures.

  19. Development of beryllium honeycomb sandwich composite for structural and other related applications

    NASA Technical Reports Server (NTRS)

    Vogan, J. W.; Grant, L. A.

    1972-01-01

    The feasibility of fabricating large beryllium honeycomb panels was demonstrated. Both flat and curved sandwich structures were manufactured using practical, braze bonding techniques. The processes developed prove that metallurgically assembled beryllium honeycomb panels show decided potential where rigid, lightweight structures are required. Three panels, each 10 square feet in surface area, were fabricated, and radiographically inspected to determine integrity. This examination revealed a 97 percent braze in the final panel. It is believed that ceramic dies for forming and brazing would facilitate the fabrication techniques for higher production rates. Ceramic dies would yield a lower thermal gradient in the panel during the braze cycle. This would eliminate the small amount of face sheet wrinkling present in the panels. Hot forming the various panel components demonstrated efficient manufacturing techniques for scaling up and producing large numbers of hot formed beryllium components and panels. The beryllium honeycomb panel demonstrated very good vibrational loading characteristics under test with desirable damping characteristics.

  20. Multi-Functional Sandwich Composites for Spacecraft Applications: An Initial Assessment

    NASA Technical Reports Server (NTRS)

    Adams, Daniel O.; Webb, Nicholas Jason; Yarger, Cody B.; Hunter, Abigail; Oborn, Kelli D.

    2007-01-01

    Current spacecraft implement relatively uncoupled material and structural systems to address a variety of design requirements, including structural integrity, damage tolerance, radiation protection, debris shielding and thermal insulation. This investigation provided an initial assessment of multi-functional sandwich composites to integrate these diverse requirements. The need for radiation shielding was addressed through the selection of polymeric constituents with high hydrogen content. To provide increased damage tolerance and debris shielding, manufacturing techniques were developed to incorporate transverse stitching reinforcement, internal layers, and a self-healing ionomer membrane. To assess the effects of a space environment, thermal expansion behavior of the candidate foam materials was investigated under a vacuum and increasing temperature. Finally, a thermal expansion model was developed for foam under vacuum conditions and its predictive capability assessed.