Study on influence of vibration behavior of composite material damage by holography

NASA Astrophysics Data System (ADS)

Guo, Linfeng; Zhao, Zhimin; Gao, Mingjuan; Zhuang, Xianzhong

2006-01-01

Composite material has been applied widely in aeronautics, astronautics and some other fields due to their high strength, light weight and antifatigue and etc. But in the application, composite material may be destroyed or damaged, which may have impact on its further applications. Therefore, study on the influence of behavior of composite material damage becomes a hot research. In this paper, the common composite material for aircraft is used as the test object, and a study is conducted to investigate the influence of vibration behavior of composite material damage. The authors adopt the method of light-carrier wave and time-average holography. Compared the interference fringes of composite materials before and after damage, the width of the interference fringes of hologram of the damaged composite material is narrower than that of the fringes before. It means that the off-plane displacement of each point on the test object is larger than before. Based on the elastic mechanics theory, the off-plane displacement is inverse to the bending stiffness, and the bending stiffness of the test object will decrease after it is damaged. In other words, the vibration property of the composite material changes after damages occur. The research results of the paper show that the results accord with the analysis of theory.

Guidelines for the Utilization of Composite Materials in Oxygen Storage Tanks

NASA Technical Reports Server (NTRS)

Davis, Samuel E.; Herald, Stephen

2006-01-01

Space travel is inherently dangerous and, currently, quite expensive. NASA has always done everything possible to minimize the risk associated with the materials chosen for space travel applications by requiring that all materials associated with NASA programs meet the strict requirements established by NASA testing standard NASA-STD-600 1 Flammability, Odor, Offgassing, and Compatibility Requirements and Test Procedures for Materials in Environments that Support Combustion. NASA also has the need to develop lighter weight structural materials that will allow more payload weight to be carried into space. NASA is utilizing composite materials inside the orbiter to lighten the overall weight, but has not considered composite materials for oxygen tanks because of the inherent incompatibility of composite materials with atomic oxygen. This presentation will focus on how oxygen tanks can be built from composite materials. Details will be provided for the design and compatibility testing techniques that will be utilized to create a new NASA standard, NASA-HDBK-6018, which will serve as the starting point for the design of oxygen tanks made from composite materials.

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

NASA Astrophysics Data System (ADS)

Sevkat, Ercan

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

Industry to Education Technical Transfer Program & Composite Materials. Composite Materials Course. Fabrication I Course. Fabrication II Course. Composite Materials Testing Course. Final Report.

ERIC Educational Resources Information Center

Massuda, Rachel

These four reports provide details of projects to design and implement courses to be offered as requirements for the associate degree program in composites and reinforced plastics technology. The reports describe project activities that led to development of curricula for four courses: composite materials, composite materials fabrication I,…

Standard Test Methods for Textile Composites

NASA Technical Reports Server (NTRS)

Masters, John E.; Portanova, Marc A.

1996-01-01

Standard testing methods for composite laminates reinforced with continuous networks of braided, woven, or stitched fibers have been evaluated. The microstructure of these textile' composite materials differs significantly from that of tape laminates. Consequently, specimen dimensions and loading methods developed for tape type composites may not be applicable to textile composites. To this end, a series of evaluations were made comparing testing practices currently used in the composite industry. Information was gathered from a variety of sources and analyzed to establish a series of recommended test methods for textile composites. The current practices established for laminated composite materials by ASTM and the MIL-HDBK-17 Committee were considered. This document provides recommended test methods for determining both in-plane and out-of-plane properties. Specifically, test methods are suggested for: unnotched tension and compression; open and filled hole tension; open hole compression; bolt bearing; and interlaminar tension. A detailed description of the material architectures evaluated is also provided, as is a recommended instrumentation practice.

Experimental characterization of composites. [load test methods

NASA Technical Reports Server (NTRS)

Bert, C. W.

1975-01-01

The experimental characterization for composite materials is generally more complicated than for ordinary homogeneous, isotropic materials because composites behave in a much more complex fashion, due to macroscopic anisotropic effects and lamination effects. Problems concerning the static uniaxial tension test for composite materials are considered along with approaches for conducting static uniaxial compression tests and static uniaxial bending tests. Studies of static shear properties are discussed, taking into account in-plane shear, twisting shear, and thickness shear. Attention is given to static multiaxial loading, systematized experimental programs for the complete characterization of static properties, and dynamic properties.

Nanocellulose based polymer composite for acoustical materials

NASA Astrophysics Data System (ADS)

Farid, Mohammad; Purniawan, Agung; Susanti, Diah; Priyono, Slamet; Ardhyananta, Hosta; Rahmasita, Mutia E.

2018-04-01

Natural fibers are biodegradable materials that are innovatively and widely used for composite reinforcement in automotive components. Nanocellulose derived from natural fibers oil palm empty bunches have properties that are remarkable for use as a composite reinforcement. However, there have not been many investigations related to the use of nanocellulose-based composites for wideband sound absorption materials. The specimens of nanocellulose-based polyester composite were prepared using a spray method. An impedance tube method was used to measure the sound absorption coefficient of this composite material. To reveal the characteristics of the nanocellulose-based polyester composite material, SEM (scanning electron microscope), TEM (Transmission Electron Microscope), FTIR (Fourier Transform Infra Red), TGA (Thermogravimetric Analysis), and density tests were performed. Sound absorption test results showed the average value of sound absorption coefficient of 0.36 to 0,46 for frequency between 500 and 4000 Hz indicating that this nanocellulose-based polyester composite materials had a tendency to wideband sound absorption materials and potentially used as automotive interior materials.

Experimental Investigation of Textile Composite Materials Using Moire Interferometry

NASA Technical Reports Server (NTRS)

Ifju, Peter G.

1995-01-01

The viability as an efficient aircraft material of advanced textile composites is currently being addressed in the NASA Advanced Composites Technology (ACT) Program. One of the expected milestones of the program is to develop standard test methods for these complex material systems. Current test methods for laminated composites may not be optimum for textile composites, since the architecture of the textile induces nonuniform deformation characteristics on the scale of the smallest repeating unit of the architecture. The smallest repeating unit, also called the unit cell, is often larger than the strain gages used for testing of tape composites. As a result, extending laminated composite test practices to textiles can often lead to pronounced scatter in material property measurements. It has been speculated that the fiber architectures produce significant surface strain nonuniformities, however, the magnitudes were not well understood. Moire interferometry, characterized by full-field information, high displacement sensitivity, and high spatial resolution, is well suited to document the surface strain on textile composites. Studies at the NASA Langley Research Center on a variety of textile architectures including 2-D braids and 3-D weaves, has evidenced the merits of using moire interferometry to guide in test method development for textile composites. Moire was used to support tensile testing by validating instrumentation practices and documenting damage mechanisms. It was used to validate shear test methods by mapping the full-field deformation of shear specimens. Moire was used to validate open hole tension experiments to determine the strain concentration and compare then to numeric predictions. It was used for through-the-thickness tensile strength test method development, to verify capabilities for testing of both 2-D and 3-D material systems. For all of these examples, moire interferometry provided vision so that test methods could be developed with less speculation and more documentation.

Combinatorial synthesis of ceramic materials

DOEpatents

Lauf, Robert J [Oak Ridge, TN; Walls, Claudia A [Oak Ridge, TN; Boatner, Lynn A [Oak Ridge, TN

2010-02-23

A combinatorial library includes a gelcast substrate defining a plurality of cavities in at least one surface thereof; and a plurality of gelcast test materials in the cavities, at least two of the test materials differing from the substrate in at least one compositional characteristic, the two test materials differing from each other in at least one compositional characteristic.

Combinatorial synthesis of ceramic materials

DOEpatents

Lauf, Robert J.; Walls, Claudia A.; Boatner, Lynn A.

2006-11-14

A combinatorial library includes a gelcast substrate defining a plurality of cavities in at least one surface thereof; and a plurality of gelcast test materials in the cavities, at least two of the test materials differing from the substrate in at least one compositional characteristic, the two test materials differing from each other in at least one compositional characteristic.

Progressive Damage and Fracture in Composites Under Dynamic Loading

NASA Technical Reports Server (NTRS)

Minnetyan, Levon

1994-01-01

A computational simulation tool is used to evaluate the various stages of damage progression in composite materials during losipescu shear testing. Unidirectional composite specimens with either the major or minor material axis in the load direction are considered. Damage progression characteristics are described for each specimen using two types of boundary conditions. A procedure is outlined regarding the use of computational simulation in the testing of composite materials.

Materials for Wind Turbine Blades: An Overview.

PubMed

Mishnaevsky, Leon; Branner, Kim; Petersen, Helga Nørgaard; Beauson, Justine; McGugan, Malcolm; Sørensen, Bent F

2017-11-09

A short overview of composite materials for wind turbine applications is presented here. Requirements toward the wind turbine materials, loads, as well as available materials are reviewed. Apart from the traditional composites for wind turbine blades (glass fibers/epoxy matrix composites), natural composites, hybrid and nanoengineered composites are discussed. Manufacturing technologies for wind turbine composites, as well their testing and modelling approaches are reviewed.

Composite Overview and Composite Aerocover Overview

NASA Technical Reports Server (NTRS)

Caraccio, Anne; Tate, LaNetra; Dokos, Adam; Taylor, Brian; Brown, Chad

2014-01-01

Materials Science Division within the Engineering Directorate tasked by the Ares Launch Vehicle Division (LX-V) and the Fluids Testing and Technology Development Branch (NE-F6) to design, fabricate and test an aerodynamic composite shield for potential Heavy Lift Launch Vehicle infusion and a composite strut that will serve as a pathfinder in evaluating calorimeter data for the CRYOSTAT (cryogenic on orbit storage and transfer) Project. ATP project is to carry the design and development of the aerodynamic composite cover or "bracket" from cradle to grave including materials research, purchasing, design, fabrication, testing, analysis and presentation of the final product. Effort consisted of support from the Materials Testing & Corrosion Control Branch (NE-L2) for mechanical testing, the Prototype Development Branch (NE-L3) for CAD drawing, design/analysis, and fabrication, Materials & Processes Engineering Branch (NE-L4) for project management and materials selection; the Applied Physics Branch (NE-LS) for NDE/NDI support; and the Chemical Analysis Branch (NE-L6) for developmental systems evaluation. Funded by the Ares Launch Vehicle Division and the Fluids Testing and Technology Development Branch will provide ODC

Development and Sliding Wear Response of Epoxy Composites Filled with Coal Mine Overburden Material

NASA Astrophysics Data System (ADS)

Das, Prithika; Satapathy, Alok; Mishra, M. K.

2018-03-01

The paper reports on development and characterization of epoxy based composites filled with micro-sized mine overburden material. Coal mine overburden material is typically highly heterogeneous and is considered as waste material. For excavating each ton of coal, roughly 5 tons of overburden materials are removed and is dumped nearby occupying large space. Gainful utilization of this waste is a major challenge. In the present work, this material is used as filler materials in making a new class of epoxy matrix composites. Composites with different weight proportions of fillers (0, 10, 20, 30 and 40) wt. % are prepared by hand layup technique. Compression tests are performed as per corresponding ASTM standards to assess the compressive strength of these composites. Further, dry sliding tests are performed following ASTM G99 standards using a pin on disk machine. A design of experiment approach based on Taguchi’s L16 orthogonal arrays is adopted. Tests are performed at different sliding velocities for multiple sliding distances under varying normal loads. Specific wear rates of the composites under different test conditions are obtained. The analysis of the test results revealed that the filler content and the sliding velocity are the most predominant control factors affecting the wear rate. This work thus, opens up a new avenue for the value added utilization of coal mine overburden material.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dr. Mohit Jain; Dr. Ganesh Skandan; Dr. Gordon E. Khose

Generation IV Very High Temperature power generating nuclear reactors will operate at temperatures greater than 900 oC. At these temperatures, the components operating in these reactors need to be fabricated from materials with excellent thermo-mechanical properties. Conventional pure or composite materials have fallen short in delivering the desired performance. New materials, or conventional materials with new microstructures, and associated processing technologies are needed to meet these materials challenges. Using the concept of functionally graded materials, we have fabricated a composite material which has taken advantages of the mechanical and thermal properties of ceramic and metals. Functionally-graded composite samples with variousmore » microstructures were fabricated. It was demonstrated that the composition and spatial variation in the composition of the composite can be controlled. Some of the samples were tested for irradiation resistance to neutrons. The samples did not degrade during initial neutron irradiation testing.« less

Radiopacity of flowable composite by a digital technique.

PubMed

Dukić, W; Delija, B; Lešić, S; Dubravica, I; Derossi, D

2013-01-01

The aim of this in vitro study was to evaluate the radiopacity of 19 current dental flowable composite materials by a digital technique. Digital radiographs were obtained with a CCD sensor using an aluminum step wedge, a 1-mm-thick tooth slice, and a 1-mm-thick flowable composite specimen using five different combinations of exposure and voltage. The radiopacity in pixels was determined using Digora 2.6. software. The equivalent thickness of aluminum for each material was then calculated based on the calibration curve. All of the tested flowable composite materials had higher radiopacities than that of dentin, but in almost every combination of exposure and voltage, there were some composite materials that exhibited radiopacities equal to or slightly greater than enamel p>α; α=0.01). Of the flowable composite materials tested, 37% showed lower radiopacities than enamel, and 21% of the tested materials had higher radiopacities than the 3-mm aluminum equivalent. The highest radiopacity at all exposure values was produced by the Majesty Flow and Charisma Opal Flow materials, which had radiopacities almost twice that of enamel. Flowable composite materials should have radiopacities greater than that of enamel (ISO 4049), an important consideration for the introduction of new materials to the market. The digital radiopacity analysis techniques used in this study provide an easy, reliable, rapid, and precise method to characterize radiopacity of dental flowable composite materials.

Design, durability and low cost processing technology for composite fan exit guide vanes

NASA Technical Reports Server (NTRS)

Blecherman, S. S.

1979-01-01

A lightweight composite fan exit guide vane for high bypass ratio gas turbine engine application was investigated. Eight candidate material/design combinations were evaluated by NASTRAN finite element analyses. A total of four combinations were selected for further analytical evaluation, part fabrication by two ventors, and fatigue test in dry and wet condition. A core and shell vane design was chosen in which the unidirectional graphite core fiber was the same for all candidates. The shell material, fiber orientation, and ply configuration were varied. Material tests were performed on raw material and composite specimens to establish specification requirements. Pre-test and post-test microstructural examination and nondestructive analyses were conducted to determine the effect of material variations on fatigue durability and failure mode. Relevant data were acquired with respect to design analysis, materials properties, inspection standards, improved durability, weight benefits, and part price of the composite fan exit guide vane.

Composite structural materials. [aircraft structures

NASA Technical Reports Server (NTRS)

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1980-01-01

The use of filamentary composite materials in the design and construction of primary aircraft structures is considered with emphasis on efforts to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, and reliability and life prediction. The redesign of a main spar/rib region on the Boeing 727 elevator near its actuator attachment point is discussed. A composite fabrication and test facility is described as well as the use of minicomputers for computer aided design. Other topics covered include (1) advanced structural analysis methids for composites; (2) ultrasonic nondestructive testing of composite structures; (3) optimum combination of hardeners in the cure of epoxy; (4) fatigue in composite materials; (5) resin matrix characterization and properties; (6) postbuckling analysis of curved laminate composite panels; and (7) acoustic emission testing of composite tensile specimens.

Advanced Ceramic Armor Materials

DTIC Science & Technology

1990-05-11

materials, toughened alumina, fiber -reinforced glass matrix composites, and multilayer-gradient materials for ballistic testing. Fabrication and...material systems: Multilayer advanced armor materials consisting of a hard ceramic faceplate bonded to a graphite fiber -reinforced glass matrix...toughened alumina, and fiber - applied studies of advanced reinforced ceramic matrix glass and glass -ceramic composites for ballistic testing. technologies

Frictional Ignition Testing of Composite Materials

NASA Technical Reports Server (NTRS)

Peralta, Steve; Rosales, Keisa; Robinson, Michael J.; Stoltzfus, Joel

2006-01-01

The space flight community has been investigating lightweight composite materials for use in propellant tanks for both liquid and gaseous oxygen for space flight vehicles. The use of these materials presents some risks pertaining to ignition and burning hazards in the presence of oxygen. Through hazard analysis process, some ignition mechanisms have been identified as being potentially credible. One of the ignition mechanisms was reciprocal friction; however, test data do not exist that could be used to clear or fail these types of materials as "oxygen compatible" for the reciprocal friction ignition mechanism. Therefore, testing was performed at White Sands Test Facility (WSTF) to provide data to evaluate this ignition mechanism. This paper presents the test system, approach, data results, and findings of the reciprocal friction testing performed on composite sample materials being considered for propellant tanks.

Color stability of esthetic restorative materials: a spectrophotometric analysis.

PubMed

Poggio, Claudio; Ceci, Matteo; Beltrami, Riccardo; Mirando, Maria; Wassim, Jaffal; Colombo, Marco

2016-12-01

Objective: The aim of this in vitro study was to evaluate the color stability of different restorative materials (one microfilled composite, one nanofilled composite, one nanohybrid composite and one Ormocer-based composite) after exposure to different staining solutions (coffee, coca-cola and red wine). Material and methods: All materials were polymerized into silicon rings (2 mm ×6 mm ×8 mm) to obtain specimens identical in size. Thirty cylindrical specimens of each material were prepared. They were immersed in staining solutions over a 28-day test period. A colorimetric evaluation according to the CIE L*a*b* system was performed by a blind trained operator at 7, 14, 21, 28 days of the staining process. The Shapiro-Wilk test and Kruskal-Wallis ANOVA were applied to assess significant differences among restorative materials. The paired t -test was applied to test which CIE L*a*b* parameters significantly changed after immersion in staining solutions. Results: All restorative materials showed clinically perceptible color differences after immersion in coffee. L* and b* values showed the highest variability. Coca cola and red wine did not influence the color stability for all restorative materials except for Filtek Supreme XTE. Conclusions: Coffee caused a significant color change in all types of tested composite resins. Filtek Supreme XTE demonstrated alone a staining susceptibility to red wine; no other significant differences among the materials were demonstrated. Long-term exposure to some food dyes (coffee in particular) can significantly affect the color stability of modern esthetic restorative materials regardless of materials' different composition.

Materials for Wind Turbine Blades: An Overview

PubMed Central

Branner, Kim; Petersen, Helga Nørgaard; Beauson, Justine; McGugan, Malcolm; Sørensen, Bent F.

2017-01-01

A short overview of composite materials for wind turbine applications is presented here. Requirements toward the wind turbine materials, loads, as well as available materials are reviewed. Apart from the traditional composites for wind turbine blades (glass fibers/epoxy matrix composites), natural composites, hybrid and nanoengineered composites are discussed. Manufacturing technologies for wind turbine composites, as well their testing and modelling approaches are reviewed. PMID:29120396

Materials Examination of the Vertical Stabilizer from American Airlines Flight 587

NASA Technical Reports Server (NTRS)

Fox, Matthew R.; Schultheisz, Carl R.; Reeder, James R.; Jensen, Brian J.

2005-01-01

The first in-flight failure of a primary structural component made from composite material on a commercial airplane led to the crash of American Airlines Flight 587. As part of the National Transportation Safety Board investigation of the accident, the composite materials of the vertical stabilizer were tested, microstructure was analyzed, and fractured composite lugs that attached the vertical stabilizer to the aircraft tail were examined. In this paper the materials testing and analysis is presented, composite fractures are described, and the resulting clues to the failure events are discussed.

Full-Field Strain Methods for Investigating Failure Mechanisms in Triaxial Braided Composites

NASA Technical Reports Server (NTRS)

Littell, Justin D.; Binienda, Wieslaw K.; Goldberg, Robert K.; Roberts, Gary D.

2008-01-01

Recent advancements in braiding technology have led to commercially viable manufacturing approaches for making large structures with complex shape out of triaxial braided composite materials. In some cases, the static load capability of structures made using these materials has been higher than expected based on material strength properties measured using standard coupon tests. A more detailed investigation of deformation and failure processes in large-unit-cell-size triaxial braid composites is needed to evaluate the applicability of standard test methods for these materials and to develop alternative testing approaches. This report presents some new techniques that have been developed to investigate local deformation and failure using digital image correlation techniques. The methods were used to measure both local and global strains during standard straight-sided coupon tensile tests on composite materials made with 12- and 24-k yarns and a 0 /+60 /-60 triaxial braid architecture. Local deformation and failure within fiber bundles was observed and correlations were made between these local failures and global composite deformation and strength.

International SAMPE Symposium and Exhibition, 35th, Anaheim, CA, Apr. 2-5, 1990, Proceedings. Books 1 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Janicki, G.; Bailey, V.; Schjelderup, H.

The present conference discusses topics in the fields of ultralightweight structures, producibility of thermoplastic composites, innovation in sandwich structures, composite failure processes, toughened materials, metal-matrix composites, advanced materials for future naval systems, thermoplastic polymers, automated composites manufacturers, advanced adhesives, emerging processes for aerospace component fabrication, and modified resin systems. Also discussed are matrix behavior for damage tolerance, composite materials repair, testing for damage tolerance, composite strength analyses, materials workplace health and safety, cost-conscious composites, bismaleimide systems, and issues facing advanced composite materials suppliers.

AECM-4; Proceedings of the 4th International Symposium on Acoustic Emission from Composite Materials, Seattle, WA, July 27-31, 1992

NASA Astrophysics Data System (ADS)

Various papers on AE from composite materials are presented. Among the individual topics addressed are: acoustic analysis of tranverse lamina cracking in CFRP laminates under tensile loading, characterization of fiber failure in graphite-epoxy (G/E) composites, application of AE in the study of microfissure damage to composite used in the aeronautic and space industries, interfacial shear properties and AE behavior of model aluminum and titanium matrix composites, amplitude distribution modelling and ultimate strength prediction of ASTM D-3039 G/E tensile specimens, AE prefailure warning system for composite structural tests, characterization of failure mechanisms in G/E tensile tests specimens using AE data, development of a standard testing procedure to yield an AE vs. strain curve, benchmark exercise on AE measurements from carbon fiber-epoxy composites. Also discussed are: interpretation of optically detected AE signals, acoustic emission monitoring of fracture process of SiC/Al composites under cyclic loading, application of pattern recognition techniques to acousto-ultrasonic testing of Kevlar composite panels, AE for high temperature monitoring of processing of carbon/carbon composite, monitoring the resistance welding of thermoplastic composites through AE, plate wave AE composite materials, determination of the elastic properties of composite materials using simulated AE signals, AE source location in thin plates using cross-correlation, propagation of flexural mode AE signals in Gr/Ep composite plates.

Impact and residual fatigue behavior of ARALL and AS6/5245 composite materials

NASA Technical Reports Server (NTRS)

Johnson, W. S.

1986-01-01

Aramide fiber reinforced aluminum laminates (ARALL) represent a cross between resin matrix composites and metals. The purpose of this study was to evaluate the impact sensitivity of this concept. Two types of ARALL (7075 aluminum prestrained and 2024 aluminum not prestrained) were tested through static indentation and the results compared to sheet 2024-T3 and 7075-T6 aluminum alloys. A state-of-the-art composite (AS6/5245) was also tested and compared to the ARALL. Further, the two types of ARALL material and the composite were dynamically impacted at two energy levels and fatigue tested to determine residual fatigue strength. Both forms of the ARALL material had worse impact resistance than monolithic sheet aluminum. The ARALL material made with 2024-T3 aluminum had better impact resistance than did the laminates made with 7075-T6 aluminum. The ARALL materials are at least equal to the composite material in impact damage resistance and are better for impact detection. The composite material has higher residual fatigue strength after impact than the ARALL material and is 25 percent lighter. The prestraining of the ARALL greatly reduces the fatigue growth of impact damage.

Modified Composite Materials Workshop

NASA Technical Reports Server (NTRS)

Dicus, D. L. (Compiler)

1978-01-01

The reduction or elimination of the hazard which results from accidental release of graphite fibers from composite materials was studied at a workshop. At the workshop, groups were organized to consider six topics: epoxy modifications, epoxy replacement, fiber modifications, fiber coatings and new fibers, hybrids, and fiber release testing. Because of the time required to develop a new material and acquire a design data base, most of the workers concluded that a modified composite material would require about four to five years of development and testing before it could be applied to aircraft structures. The hybrid working group considered that some hybrid composites which reduce the risk of accidental fiber release might be put into service over the near term. The fiber release testing working group recommended a coordinated effort to define a suitable laboratory test.

Investigation on mechanical properties of basalt composite fabrics (experiment study)

NASA Astrophysics Data System (ADS)

Talebi Mazraehshahi, H.; Zamani, H.

2010-06-01

To fully appreciate the role and application of composite materials to structures, correct understanding of mechanical behaviors required for selection of optimum material. Fabric reinforced composites are composed of a matrix that is reinforced with pliable fabric, glass fabric is most popular reinforcement for different application specially in aircraft structure, although other fabric material are also used. At this study new fabric material called basalt with epoxy resin introduced and mechanical behaviors of this material investigated from view point of testing. For this study two type of fabric with different thickness used. Comparison between this composite reinforcement with popular reinforcement as carbon, glass, kevlar performed. To determine mechanical properties of epoxy based basalt fabric following test procedure performed : 1). Tensile testing according to ASTM D3039 in 0° and 90° direction to find ultimate strength in tension and shear, modulus of elasticity, elangation and ultimate strain. 2). Compression testing according to EN 2850 ultimate compression strength and maximum deformation under compression loading. 3). Shear testing according to ASTM D3518-94 to find in plane shear response of polymer matrix composites materials. 4). Predict flexural properties of sandwich construction which manufactured from basalt facing with PVC foam core according to ASTM C393-94. Material strength properties must be based on enough tests of material to meet the test procedure specifications [1]. For this reason six specimens were manufactured for testing and the tests were performed on them using an INSTRON machine model 5582. In the study, the effect of percent of resin in basalt reinforced composite was investigated. Also the weights of the ballast based composites with different percent of resin were measured with conventional composites. As the weight is an important parameter in aerospace industry when the designer wants to replace one material with another, the effect of weight must be considered. Weight measurement showed that the replacement of glass fabric reinforcement with basalt fabric has little effect on weight. Investigation also shows that mechanical behavior of basalt fabric is higher than glass fabric. This is due to the excellent mechanical properties of the ballast fabric such as Young modulus and strength in compare with the glass fabric. Figure1 shows the samples which used for tensile testing in warp direction.

Cytotoxicity of dental alloys, metals, and ceramics assessed by millipore filter, agar overlay, and MTT tests.

PubMed

Sjögren, G; Sletten, G; Dahl, J E

2000-08-01

Biocompatibility of dental materials is dependent on the release of elements from the materials. In addition, the composition, pretreatment, and handling of the materials influence the element release. This study evaluated the cytotoxicity of dental alloys, metals, and ceramics, with specific emphasis on the effects of altering the composition and the pretreatment. By using cells from a mouse fibroblast cell line and the agar overlay test, Millipore filter test, and MTT test, cytotoxicity of various metals, metal alloys, and ceramics for dental restoration were studied. Effects of altering the composition of a high noble gold alloy and of pretreatment of a ceramic-bonding alloy were also studied. In addition, the release of elements into the cell culture medium by the materials studied was measured using an inductively coupled plasma optical emission spectrophotometer. The results of the MTT test were analyzed statistically using ANOVA and Scheffé test at a significance level of P <.05. Specimens manufactured from materials intended for dental restorations and handled in accordance with the manufacturers' instructions were ranked from "noncytotoxic" to "mildly cytotoxic" according to the agar overlay and Millipore filter tests. For the MTT test, no significant differences were observed between these materials and controls, with the exception of JS C-gold and unalloyed titanium. The modified materials were ranked from "mildly cytotoxic" to "moderately cytotoxic" in the agar overlay and Millipore filter tests and from "noncytotoxic" to "moderately cytotoxic" in the MTT test. Thus, cytotoxicity was related to the alloy composition and treatment. The release of Cu and Zn seemed to be important for the cytotoxic effect. Alterations in the composition and the pretreatment can greatly influence the cytotoxicity, and the results stress the importance of carefully following the manufacturers' instructions when handling dental materials.

Composite structural materials. [aircraft applications

NASA Technical Reports Server (NTRS)

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1981-01-01

The development of composite materials for aircraft applications is addressed with specific consideration of physical properties, structural concepts and analysis, manufacturing, reliability, and life prediction. The design and flight testing of composite ultralight gliders is documented. Advances in computer aided design and methods for nondestructive testing are also discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siranosian, Antranik Antonio; Schembri, Philip Edward; Luscher, Darby Jon

The Los Alamos National Laboratory's Weapon Systems Engineering division's Advanced Engineering Analysis group employs material constitutive models of composites for use in simulations of components and assemblies of interest. Experimental characterization, modeling and prediction of the macro-scale (i.e. continuum) behaviors of these composite materials is generally difficult because they exhibit nonlinear behaviors on the meso- (e.g. micro-) and macro-scales. Furthermore, it can be difficult to measure and model the mechanical responses of the individual constituents and constituent interactions in the composites of interest. Current efforts to model such composite materials rely on semi-empirical models in which meso-scale properties are inferredmore » from continuum level testing and modeling. The proposed approach involves removing the difficulties of interrogating and characterizing micro-scale behaviors by scaling-up the problem to work with macro-scale composites, with the intention of developing testing and modeling capabilities that will be applicable to the mesoscale. This approach assumes that the physical mechanisms governing the responses of the composites on the meso-scale are reproducible on the macro-scale. Working on the macro-scale simplifies the quantification of composite constituents and constituent interactions so that efforts can be focused on developing material models and the testing techniques needed for calibration and validation. Other benefits to working with macro-scale composites include the ability to engineer and manufacture—potentially using additive manufacturing techniques—composites that will support the application of advanced measurement techniques such as digital volume correlation and three-dimensional computed tomography imaging, which would aid in observing and quantifying complex behaviors that are exhibited in the macro-scale composites of interest. Ultimately, the goal of this new approach is to develop a meso-scale composite modeling framework, applicable to many composite materials, and the corresponding macroscale testing and test data interrogation techniques to support model calibration.« less

Capturing the Energy Absorbing Mechanisms of Composite Structures under Crash Loading

NASA Astrophysics Data System (ADS)

Wade, Bonnie

As fiber reinforced composite material systems become increasingly utilized in primary aircraft and automotive structures, the need to understand their contribution to the crashworthiness of the structure is of great interest to meet safety certification requirements. The energy absorbing behavior of a composite structure, however, is not easily predicted due to the great complexity of the failure mechanisms that occur within the material. Challenges arise both in the experimental characterization and in the numerical modeling of the material/structure combination. At present, there is no standardized test method to characterize the energy absorbing capability of composite materials to aide crashworthy structural design. In addition, although many commercial finite element analysis codes exist and offer a means to simulate composite failure initiation and propagation, these models are still under development and refinement. As more metallic structures are replaced by composite structures, the need for both experimental guidelines to characterize the energy absorbing capability of a composite structure, as well as guidelines for using numerical tools to simulate composite materials in crash conditions has become a critical matter. This body of research addresses both the experimental characterization of the energy absorption mechanisms occurring in composite materials during crushing, as well as the numerical simulation of composite materials undergoing crushing. In the experimental investigation, the specific energy absorption (SEA) of a composite material system is measured using a variety of test element geometries, such as corrugated plates and tubes. Results from several crush experiments reveal that SEA is not a constant material property for laminated composites, and varies significantly with the geometry of the test specimen used. The variation of SEA measured for a single material system requires that crush test data must be generated for a range of different test geometries in order to define the range of its energy absorption capability. Further investigation from the crush tests has led to the development of a direct link between geometric features of the crush specimen and its resulting SEA. Through micrographic analysis, distinct failure modes are shown to be guided by the geometry of the specimen, and subsequently are shown to directly influence energy absorption. A new relationship between geometry, failure mode, and SEA has been developed. This relationship has allowed for the reduction of the element-level crush testing requirement to characterize the composite material energy absorption capability. In the numerical investigation, the LS-DYNA composite material model MAT54 is selected for its suitability to model composite materials beyond failure determination, as required by crush simulation, and its capability to remain within the scope of ultimately using this model for large-scale crash simulation. As a result of this research, this model has been thoroughly investigated in depth for its capacity to simulate composite materials in crush, and results from several simulations of the element-level crush experiments are presented. A modeling strategy has been developed to use MAT54 for crush simulation which involves using the experimental data collected from the coupon- and element-level crush tests to directly calibrate the crush damage parameter in MAT54 such that it may be used in higher-level simulations. In addition, the source code of the material model is modified to improve upon its capability. The modifications include improving the elastic definition such that the elastic response to multi-axial load cases can be accurately portrayed simultaneously in each element, which is a capability not present in other composite material models. Modifications made to the failure determination and post-failure model have newly emphasized the post-failure stress degradation scheme rather than the failure criterion which is traditionally considered the most important composite material model definition for crush simulation. The modification efforts have also validated the use of the MAT54 failure criterion and post-failure model for crash modeling when its capabilities and limitations are well understood, and for this reason guidelines for using MAT54 for composite crush simulation are presented. This research has effectively (a) developed and demonstrated a procedure that defines a set of experimental crush results that characterize the energy absorption capability of a composite material system, (b) used the experimental results in the development and refinement of a composite material model for crush simulation, (c) explored modifying the material model to improve its use in crush modeling, and (d) provided experimental and modeling guidelines for composite structures under crush at the element-level in the scope of the Building Block Approach.

Standard test evaluation of graphite fiber/resin matrix composite materials for improved toughness

NASA Technical Reports Server (NTRS)

Chapman, Andrew J.

1984-01-01

Programs sponsored by NASA with the commercial transport manufacturers to develop a technology data base are required to design and build composite wing and fuselage structures. To realize the full potential of composite structures in these strength critical designs, material systems having improved ductility and interlaminar toughness are being sought. To promote systematic evaluation of new materials, NASA and the commercial transport manufacturers have selected and standardized a set of five common tests. These tests evaluate open hole tension and compression performance, compression performance after impact at an energy level of 20 ft-lb, and resistance to delamination. Ten toughened resin matrix/graphite fiber composites were evaluated using this series of tests, and their performance is compared with a widely used composite system.

Molding of strength testing samples using modern PDCPD material for purpose of automotive industry

NASA Astrophysics Data System (ADS)

Grabowski, L.; Baier, A.; Sobek, M.

2017-08-01

The casting of metal materials is widely known but the molding of composite polymer materials is not well-known method still. The initial choice of method for producing composite bodies was the method of casting of PDCPD material. For purpose of performing casting of polymer composite material, a special mold was made. Firstly, the 3D printed, using PLA material, mold was used. After several attempts of casting PDCPD many problems were encountered. The second step was to use mold milled from a firm and dense isocyanate foam. After several attempts research shown that this solution is more resistant to high-temperature peak, but this material is too fragile to use it several times. This solution also prevents mold from using external heating, which can be necessary for performing correct molding process. The last process was to use the aluminum mold, which is dedicated to PDCPD polymer composite, because of low adhesiveness. This solution leads to perform correct PDCPD polymer composite material injection. After performing casting operation every PDCPD testing samples were tested. These results were compared together. The result of performed work was to archive correct properties of injection of composite material. Research and results were described in detail in this paper.

Compression Testing of Textile Composite Materials

NASA Technical Reports Server (NTRS)

Masters, John E.

1996-01-01

The applicability of existing test methods, which were developed primarily for laminates made of unidirectional prepreg tape, to textile composites is an area of concern. The issue is whether the values measured for the 2-D and 3-D braided, woven, stitched, and knit materials are accurate representations of the true material response. This report provides a review of efforts to establish a compression test method for textile reinforced composite materials. Experimental data have been gathered from several sources and evaluated to assess the effectiveness of a variety of test methods. The effectiveness of the individual test methods to measure the material's modulus and strength is determined. Data are presented for 2-D triaxial braided, 3-D woven, and stitched graphite/epoxy material. However, the determination of a recommended test method and specimen dimensions is based, primarily, on experimental results obtained by the Boeing Defense and Space Group for 2-D triaxially braided materials. They evaluated seven test methods: NASA Short Block, Modified IITRI, Boeing Open Hole Compression, Zabora Compression, Boeing Compression after Impact, NASA ST-4, and a Sandwich Column Test.

Cooperative program for design, fabrication, and testing of graphite/epoxy composite helicopter shafting

NASA Technical Reports Server (NTRS)

Wright, C. C.; Baker, D. J.; Corvelli, N.; Thurston, L.; Clary, R.; Illg, W.

1971-01-01

The fabrication of UH-1 helicopter tail rotor drive shafts from graphite/epoxy composite materials is discussed. Procedures for eliminating wrinkles caused by lack of precure compaction are described. The development of the adhesive bond between aluminum end couplings and the composite tube is analyzed. Performance tests to validate the superiority of the composite materials are reported.

Prosthetic limb sockets from plant-based composite materials.

PubMed

Campbell, Andrew I; Sexton, Sandra; Schaschke, Carl J; Kinsman, Harry; McLaughlin, Brian; Boyle, Martin

2012-06-01

There is a considerable demand for lower limb prostheses globally due to vascular disease, war, conflict, land mines and natural disasters. Conventional composite materials used for prosthetic limb sockets include acrylic resins, glass and carbon fibres, which produce harmful gasses and dust in their manufacture. To investigate the feasibility of using a renewable plant oil-based polycarbonate-polyurethane copolymer resin and plant fibre composite, instead of conventional materials, to improve safety and accessibility of prosthetic limb manufacture. Experimental, bench research. Test pieces of the resin with a range of plant fibres (10.0% by volume) were prepared and tensile strengths were tested. Test sockets of both conventional composite materials and plant resin with plant fibres were constructed and tested to destruction. Combinations of plant resin and either banana or ramie fibres gave high tensile strengths. The conventional composite material socket and plant resin with ramie composite socket failed at a similar loading, exceeding the ISO 10328 standard. Both wall thickness and fibre-matrix adhesion played a significant role in socket strength. From this limited study we conclude that the plant resin and ramie fibre composite socket has the potential to replace the standard layup. Further mechanical and biocompatibility testing as well as a full economic analysis is required. Using readily sourced and renewable natural fibres and a low-volatile bio-resin has potential to reduce harm to those involved in the manufacture of artificial limb sockets, without compromising socket strength and benefitting clinicians working in poorer countries where safety equipment is scarce. Such composite materials will reduce environmental impact.

In vitro evaluation of five core materials.

PubMed

Gu, Steven; Rasimick, Brian J; Deutsch, Allan S; Musikant, Barry L

2007-01-01

This in vitro study determined the fracture strength of five core materials supported by two different endodontic dowels. Diametral tensile strength and microhardness of the three resin composite core materials used in this study were also tested. The fracture strength study used one lanthanide-reinforced flowable resin composite (Ti-Core Auto E), one titanium- and lanthanide-reinforced composite (Ti-Core), one lanthanide-reinforced composite (Ti-Core Natural), and two metal-reinforced glass ionomer core materials (Ketac Silver and GC Miracle Mix). Two types of dowels were used: a multitiered, split-shank threaded dowel with a flange (#1 Flexi-Flange) and one without a flange design (#1 Flexi-Post). The specimens were divided into ten groups. Each tooth/dowel and core specimen was placed in a special jig at 45 degrees and subjected to a load by a universal testing machine. The diametral tensile strength and the microhardness of the three resin composite core materials were measured by a universal testing machine and Barcol hardness tester, respectively. All test groups contained ten specimens. The fracture strength value of the resin composite core materials was significantly larger ( p < 0.0001) than those for the metal-reinforced glass-ionomer core materials. Analysis of variance (ANOVA) also showed that the Flexi-Flange dowel interacted with Ti-Core and Ti-Core Auto E to significantly ( p < 0.0013) increase the fracture strength relative to the Flexi-Post. One-way ANOVA revealed that there were no significant differences between them in terms of diametral tensile strength. The Barcol hardness values of the composite core materials were statistically different ( p < 0.0001), with the Ti-Core the highest, followed by Ti-Core Natural, then Ti-Core Auto E. Resin composite core material performed better than glass ionomer material in this in vitro study. The flowable composite core material performed about the same in terms of fracture strength and diametral tensile strength compared with nonflowable composites. Combined with certain core materials, the flange design increased the fracture strength of the tooth/dowel and core combination.

An effect of humid climate on micro structure and chemical component of natural composite (Boehmeria nivea-Albizia falcata) based wind turbine blade

NASA Astrophysics Data System (ADS)

Sudarsono, S.; Purwanto; Sudarsono, Johny W.

2018-02-01

In this work, wind turbine blade NACA 4415 is fabricated from natural composite of Boehmeria nivea and Albizia falcate. The composite fabrication method used is hand lay up method. The aim of the work is to investigate an effect of humid climate of coastal area on micro structure and chemical composition of composite material of the blade. The wind turbine is tested at Pantai Baru, Bantul, Yogyakarta for 5.5 months. The micro structure scanning is performed with Scanning Electron Microscope (SEM) and material component is measured with Energy Dispersive X-ray spectrometer (EDS). The samples are tested before and after the use within 5.5 month at the location. The results show that composite material inexperienced interface degradation and insignificant change of micro structure. From EDS test, it is observed that Na filtration reduces C and increases O in composite material after 5.5 months.

Physical properties of a new sonically placed composite resin restorative material.

PubMed

Ibarra, Emily T; Lien, Wen; Casey, Jeffery; Dixon, Sara A; Vandewalle, Kraig S

2015-01-01

A new nanohybrid composite activated by sonic energy has been recently introduced as a single-step, bulk-fill restorative material. The purpose of this study was to compare the physical properties of this new composite to various other composite restorative materials marketed for posterior or bulk-fill placement. The following physical properties were examined: depth of cure, volumetric shrinkage, flexural strength, flexural modulus, fracture toughness, and percent porosity. A mean and standard deviation were determined per group. One-way ANOVA and Tukey's post hoc tests were performed per property (α = 0.05). Percent porosity was evaluated with a Kruskal-Wallis/Mann-Whitney test (α = 0.005). Significant differences were found between groups (P < 0.001) per test type. Compared to the other composite restorative materials, the new nanohybrid composite showed low shrinkage and percent porosity, moderate fracture toughness and flexural modulus, and high flexural strength. However, it also demonstrated a relatively reduced depth of cure compared to the other composites.

Mechanical characterization of a short fiber-reinforced polymer at room temperature: experimental setups evaluated by an optical measurement system

NASA Astrophysics Data System (ADS)

Röhrig, C.; Scheffer, T.; Diebels, S.

2017-09-01

Composite materials are of great interest for industrial applications because of their outstanding properties. Each composite material has its own characteristics due to the large number of possible combinations of matrix and filler. As a result of their compounding, composites usually show a complex material behavior. This work is focused on the experimental testing of a short fiber-reinforced thermoplastic composite at room temperature. The characteristic behavior of this material class is often based on a superposition of typical material effects. The predicted characteristic material properties such as elasto-plasticity, damage and anisotropy of the investigated material are obtained from results of cyclic uniaxial tensile tests at constant strain rate. Concerning the manufacturing process as well as industrial applications, the experimental investigations are extended to multiaxial loading situations. Therefore, the composite material is examined with a setup close to a deep-drawing process, the Nakajima test (Nakazima et al. in Study on the formability of steel sheets. Yawate Technical Report No. 264, pp 8517-8530, 1968). The evaluation of the experimental investigations is provided by an optical analysis system using a digital image correlation software. Finally, based on the results of the uniaxial tensile tests, a one-dimensional macroscopic model is introduced and first results of the simulation are provided.

Microstructure, Friction and Wear of Aluminum Matrix Composites

NASA Astrophysics Data System (ADS)

Florea, R. M.

2018-06-01

MMCs are made by dispersing a reinforcing material into a metal matrix. They are prepared by casting, although several technical challenges exist with casting technology. Achieving a homogeneous distribution of reinforcement within the matrix is one such challenge, and this affects directly on the properties and quality of composite. The aluminum alloy composite materials consist of high strength, high stiffness, more thermal stability, more corrosion and wear resistance, and more fatigue life. Aluminum alloy materials found to be the best alternative with its unique capacity of designing the materials to give required properties. In this work a composite is developed by adding silicon carbide in Aluminum metal matrix by mass ratio 5%, 10% and 15%. Mechanical tests such as hardness test and microstructure test are conducted.

Results of ASTM round robin testing for mode 1 interlaminar fracture toughness of composite materials

NASA Technical Reports Server (NTRS)

Obrien, T. Kevin; Martin, Roderick H.

1992-01-01

The results are summarized of several interlaboratory 'round robin' test programs for measuring the mode 1 interlaminar fracture toughness of advanced fiber reinforced composite materials. Double Cantilever Beam (DCB) tests were conducted by participants in ASTM committee D30 on High Modulus Fibers and their Composites and by representatives of the European Group on Fracture (EGF) and the Japanese Industrial Standards Group (JIS). DCB tests were performed on three AS4 carbon fiber reinforced composite materials: AS4/3501-6 with a brittle epoxy matrix; AS4/BP907 with a tough epoxy matrix; and AS4/PEEK with a tough thermoplastic matrix. Difficulties encountered in manufacturing panels, as well as conducting the tests are discussed. Critical issues that developed during the course of the testing are highlighted. Results of the round robin testing used to determine the precision of the ASTM DCB test standard are summarized.

Processing and Material Characterization of Continuous Basalt Fiber Reinforced Ceramic Matrix Composites Using Polymer Derived Ceramics.

NASA Technical Reports Server (NTRS)

Cox, Sarah B.

2014-01-01

The need for high performance vehicles in the aerospace industry requires materials which can withstand high loads and high temperatures. New developments in launch pads and infrastructure must also be made to handle this intense environment with lightweight, reusable, structural materials. By using more functional materials, better performance can be seen in the launch environment, and launch vehicle designs which have not been previously used can be considered. The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Polymer matrix composites can be used for temperatures up to 260C. Ceramics can take much higher temperatures, but they are difficult to produce and form in bulk volumes. Polymer Derived Ceramics (PDCs) begin as a polymer matrix, allowing a shape to be formed and cured and then to be pyrolized in order to obtain a ceramic with the associated thermal and mechanical properties. The use of basalt in structural and high temperature applications has been under development for over 50 years, yet there has been little published research on the incorporation of basalt fibers as a reinforcement in the composites. In this study, continuous basalt fiber reinforced PDCs have been fabricated and tested for the applicability of this composite system as a high temperature structural composite material. The oxyacetylene torch testing and three point bend testing have been performed on test panels and the test results are presented.

Acoustic emission as a screening tool for ceramic matrix composites

NASA Astrophysics Data System (ADS)

Ojard, Greg; Goberman, Dan; Holowczak, John

2017-02-01

Ceramic matrix composites are composite materials with ceramic fibers in a high temperature matrix of ceramic or glass-ceramic. This emerging class of materials is viewed as enabling for efficiency improvements in many energy conversion systems. The key controlling property of ceramic matrix composites is a relatively weak interface between the matrix and the fiber that aids crack deflection and fiber pullout resulting in greatly increased toughness over monolithic ceramics. United Technologies Research Center has been investigating glass-ceramic composite systems as a tool to understand processing effects on material performance related to the performance of the weak interface. Changes in the interface have been shown to affect the mechanical performance observed in flexural testing and subsequent microstructural investigations have confirmed the performance (or lack thereof) of the interface coating. Recently, the addition of acoustic emission testing during flexural testing has aided the understanding of the characteristics of the interface and its performance. The acoustic emission onset stress changes with strength and toughness and this could be a quality tool in screening the material before further development and use. The results of testing and analysis will be shown and additional material from other ceramic matrix composite systems may be included to show trends.

[Preparation of sodium alginate-nanohydroxyapatite composite material for bone repair and its biocompatibility].

PubMed

Wang, Yanmei; He, Jiacai; Li, Quanli; Shen, Jijia

2014-02-01

To prepare sodium alginate-nanohydroxyapatite composite material and to explore its feasibility as a bone repair material. Sodium alginate-nanohydroxyapatite composite material was prepared using chemical cross-linking and freeze-drying technology. The composite was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) and its porosity was measured by liquid displacement method. The fifth passage of bone marrow stromal stem cells (BMSCs) were incubated on the composite material and then growth was observed by inverted microscope and SEM. BMSCs were cultured with liquid extracts of the material, methyl thiazolyl tetrazolium (MTT) assay was used to calculate the relative growth rate (RGR) on 1, 3, 5 d and to evaluate the cytotoxicity. Fresh dog blood was added into the liquid extracts to conduct hemolysis test, the spectrophotometer was used to determine the optical density (OD) and to calculate the hemolysis rate. Sodium alginate-nanohydroxyapatite composite material displayed porosity, the porous pore rate was (88.6 +/- 4.5)%. BMSCs showed full stretching and vigorous growth under inverted microscope and SEM. BMSCs cultured with liquid extracts of the material had good activities. The toxicity of composite material was graded as 1. Hemolysis test results showed that the hemolysis rate of the composite material was 1.28%, thus meeting the requirement of medical biomaterials. The composite material fabricated in this study has high porosity and good biocompatibility.

Flexible neutron shielding composite material of EPDM rubber with boron trioxide: Mechanical, thermal investigations and neutron shielding tests

NASA Astrophysics Data System (ADS)

Özdemir, T.; Güngör, A.; Reyhancan, İ. A.

2017-02-01

In this study, EPDM and boron trioxide composite was produced and mechanical, thermal and neutron shielding tests were performed. EPDM rubber (Ethylene Propylene Diene Monomer) having a considerably high hydrogen content is an effective neutron shielding material. On the other hand, the materials containing boron components have effective thermal neutron absorption crossection. The composite of EPDM and boron trioxide would be an effective solution for both respects of flexibility and effectiveness for developing a neutron shielding material. Flexible nature of EPDM would be a great asset for the shielding purpose in case of intervention action to a radiation accident. The theoretical calculations and experimental neutron absorption tests have shown that the results were in parallel and an effective neutron shielding has been achieved with the use of the developed composite material.

Discoloration of different esthetic restorative materials: A spectrophotometric evaluation

PubMed Central

Ceci, Matteo; Viola, Matteo; Rattalino, Davide; Beltrami, Riccardo; Colombo, Marco; Poggio, Claudio

2017-01-01

Objective: A crucial property of esthetic restorative materials is their long-term color stability. The aim of this in vitro study was to evaluate the color stability of esthetic restorative materials (one microfilled flowable composite, one nanofilled composite, one nanoybrid composite, one microfilled composite, and one nanoybrid ormocer-based composite) after surface roughening with cola and exposure to different staining solutions (coffee and red wine). Materials and Methods: All materials were polymerized into silicone rubber rings (2 mm × 6 mm × 8 mm) to obtain 150 specimens identical in size. Seventy-five specimens of Group A were first exposed to cola for 24 h, and then samples were immersed in coffee or red wine over a 28-day test period. A colorimetric evaluation, according to the CIE L*a*b* system, was performed at 7, 14, 21, 28 days. Shapiro–Wilk test and Kruskal–Wallis analysis of variance were applied to assess significant differences among restorative materials. Means were compared with Scheffe's multiple comparison test at the 0.05 level of significance. Results: Specimens of Group A showed higher variations when compared with Group B's specimens (P < 0.05). After 28 days, the immersion protocols caused a clinically perceivable color change for all materials tested (P < 0.05). CeramX Universal and Admira Fusion showed the lowest ΔE variations (P < 0.05). Conclusions: Staining beverages caused significant discolorations for all the materials tested. The first exposure to cola enhanced the subsequent staining with coffee or red wine. Nanohybrid composites reported the lowest color variations. PMID:28729784

Energy Absorption in Chopped Carbon Fiber Compression Molded Composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Starbuck, J.M.

2001-07-20

In passenger vehicles the ability to absorb energy due to impact and be survivable for the occupant is called the ''crashworthiness'' of the structure. To identify and quantify the energy absorbing mechanisms in candidate automotive composite materials, test methodologies were developed for conducting progressive crush tests on composite plate specimens. The test method development and experimental set-up focused on isolating the damage modes associated with the frond formation that occurs in dynamic testing of composite tubes. Quasi-static progressive crush tests were performed on composite plates manufactured from chopped carbon fiber with an epoxy resin system using compression molding techniques. Themore » carbon fiber was Toray T700 and the epoxy resin was YLA RS-35. The effect of various material and test parameters on energy absorption was evaluated by varying the following parameters during testing: fiber volume fraction, fiber length, fiber tow size, specimen width, profile radius, and profile constraint condition. It was demonstrated during testing that the use of a roller constraint directed the crushing process and the load deflection curves were similar to progressive crushing of tubes. Of all the parameters evaluated, the fiber length appeared to be the most critical material parameter, with shorter fibers having a higher specific energy absorption than longer fibers. The combination of material parameters that yielded the highest energy absorbing material was identified.« less

Effectiveness of metal matrix and ceramic matrix composites as orbital debris shield materials

NASA Technical Reports Server (NTRS)

Mcgill, Preston B.; Mount, Angela R.

1992-01-01

The effectiveness of two metal matrix composites and one ceramic matrix material in defeating hypervelocity impacts at about 3.8 km/s are evaluated to determine the potential of these composites as spacecraft shield materials. The metal matrix composites investigated consist of SiC particles (70 percent by volume) in an aluminum matrix and Al2O3 particles (50 percent by volume) in an Al matrix. The ceramic composite consists of ZrB2 platelets in a ZrC matrix. Both the metal matrix and ceramic matrix composites are found to perform as well or better than 6061-T6 aluminum, which is presently used in the Whipple type bumper shield of Space Station Freedom. Test results indicate that the composites tested may have applications as micrometeoroid/orbital debris shield materials.

Energy Finite Element Analysis Developments for Vibration Analysis of Composite Aircraft Structures

NASA Technical Reports Server (NTRS)

Vlahopoulos, Nickolas; Schiller, Noah H.

2011-01-01

The Energy Finite Element Analysis (EFEA) has been utilized successfully for modeling complex structural-acoustic systems with isotropic structural material properties. In this paper, a formulation for modeling structures made out of composite materials is presented. An approach based on spectral finite element analysis is utilized first for developing the equivalent material properties for the composite material. These equivalent properties are employed in the EFEA governing differential equations for representing the composite materials and deriving the element level matrices. The power transmission characteristics at connections between members made out of non-isotropic composite material are considered for deriving suitable power transmission coefficients at junctions of interconnected members. These coefficients are utilized for computing the joint matrix that is needed to assemble the global system of EFEA equations. The global system of EFEA equations is solved numerically and the vibration levels within the entire system can be computed. The new EFEA formulation for modeling composite laminate structures is validated through comparison to test data collected from a representative composite aircraft fuselage that is made out of a composite outer shell and composite frames and stiffeners. NASA Langley constructed the composite cylinder and conducted the test measurements utilized in this work.

Tensile, Compression, Open-Hole Compression and Double Cantilever Beam Fracture Toughness Testing of Multiple NASA Langley Research Center Composite Materials

NASA Technical Reports Server (NTRS)

Adams, Donald F.

1999-01-01

The attached data summarizes the work performed by the Composite Materials Research Group at the University of Wyoming funded by the NASA LaRC Research Grant NAG-1-1294. The work consisted primarily of tension, compression, open-hole compression and double cantilever beam fracture toughness testing performed an a variety of NASA LaRC composite materials. Tests were performed at various environmental conditions and pre-conditioning requirements. The primary purpose of this work was to support the LaRC material development efforts. The data summaries are arranged in chronological order from oldest to newest.

Poly-paper: a sustainable material for packaging, based on recycled paper and recyclable with paper.

PubMed

Del Curto, Barbara; Barelli, Nadia; Profaizer, Mauro; Farè, Silvia; Tanzi, Maria Cristina; Cigada, Alberto; Ognibene, Giulia; Recca, Giuseppe; Cicala, Gianluca

2016-11-02

Until now, environmental sustainability issues are almost entirely unsolved for packaging materials. With the final aim of finding materials with a single recycling channel, cellulose fiber/poly(vinyl)alcohol composites were investigated. After extrusion and injection molding, samples of composite with different cellulose fiber content (30%, 50% and 70% w/w) were tested. Tensile mechanical tests exhibited an improvement in composite stiffness when the reinforcement content was increased together with a decrease in composite elongation. Solubility tests performed at room temperature and 45°C showed different behavior depending on the water-resistant film applied on the composite (50% cellulose fiber content). In particular, the uncoated composite showed complete solubility after 2 hours, whereas at the same time point, no solubility occurred when a non-water-soluble varnish was used. The proposed composites, named Poly-paper, appear to warrant further investigation as highly sustainable packaging.

Development of Fracture Mechanics Maps for Composite Materials. Volume 2.

DTIC Science & Technology

1985-12-01

AD-A169 663 DEP 1/3UR OIOST l uNCL~ss~~n HUCI S I B M 11 1*2 AF,:P,.-TR-?5,-4150 DEVELOPMENT OF FRACTURE MECHANICS MAPS FOR COMPOSITE MATERIALS Dr. H...coIo. Development of N/A N/A N/A N/A Fracture Mechanics Maps for Composite Materials 12. PERSONAL AUTHORISI Editor (Dr. H. W. Bergmann) 13. TYPE OF...GROUP SUB GR. Fiber Reinforced Composites , Dynamic Test, Thermal Cycling, 1I1 04 Quality Control, Static Test, Stress Concentrations 01 03 19

Composite armored vehicle advanced technology demonstator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ostberg, D.T.; Dunfee, R.S.; Thomas, G.E.

1996-12-31

Composite structures are a key technology needed to develop future lightweight combat vehicles that are both deployable and survivable. The Composite Armored Vehicle Advanced Technology Demonstrator Program that started in fiscal year 1994 will continue through 1998 to verily that composite structures are a viable solution for ground combat vehicles. Testing thus far includes material characterization, structural component tests and full scale quarter section tests. Material and manufacturing considerations, tests, results and changes, and the status of the program will be described. The structural component tests have been completed successfully, and quarter section testing is in progress. Upon completion ofmore » the critical design review, the vehicle demonstrator will be Fabricated and undergo government testing.« less

Damage Processes in a Quasi-Isotropic Composite Short Beam Under Three- Point Loading

DTIC Science & Technology

1992-01-01

American Society for Testing and Materials, 1916 Race Street, Philadelphia, PA 19103 12a. DISTRIBUTION /AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE...three- point bend test Is investigated for a composite with a quasi-isotropic layup. Failue is found to Initiate iri a region near the point of...Composites Technology & Research, Winter 1991 Copyright American Society for Testing and Materials, 1916 Race Street, Philadelphia, PA 19103 REFERENCE

The Effect of Localized Damage on the Electrical Conductivity of Bare Carbon Fiber Tow and its Use as a Non-Destructive Evaluation Tool for Composite Overwrapped Pressure Vessels

NASA Technical Reports Server (NTRS)

Wentzel, Daniel

2015-01-01

Composite materials are beneficial because of their high specific strength and low weight. Safety, Destructive testing and destructive testing, Non-Destructive Testing (NDT) and Non-Destructive Evaluation (NDE). Problem: Neither NDT nor NDE can provide sufficient data to determine life expectancy or quantify the damage state of a composite material.

Vegetable Fibers for Composite Materials In Constructive Sector

NASA Astrophysics Data System (ADS)

Giglio, Francesca; Savoja, Giulia

2017-08-01

The aim of the research is to study and to test bio-mixture for laminas to use in construction field components. Composite materials are becoming more common in different sectors, but their embodied energy is an environmental problem. For this, in recent years, the researchers investigate new mixtures for composites, in particular with vegetable fibers and bio-based epoxy resin. The research carried out different laboratory tests for material and mechanical characterization, starting from the analysis of vegetable fibers, and arriving to test different kind of laminas with sundry fabrics and bio-based epoxy resin. In the most general organization of the theme, the research has the overall objective to contribute to reduce composites environmental impacts, with the promotion of local production chains about innovative materials from renewable and sustainable sources.

Friction and wear behavior of aluminum and composite airplane skins

NASA Technical Reports Server (NTRS)

Jackson, K. E.

1984-01-01

Friction and wear behavior was determined for small skin specimens under abrasive loading conditions typical of those occurring on the underside of a transport airplane during emergency belly landing. A test apparatus consisting of a standard belt sander provided the sliding surface. Small test specimens constructed of aluminum, standard graphite-epoxy composite, aramid-epoxy composite, and toughened-resin composites were tested undar a range of pressures, belt velocities, and belt-surface textures. The effects of these test variables on the wear rate and the coefficient of friction are discussed and comparisons are made between the composite materials and aluminum. The effect of fiber orientation in the composite materials on wear rate was also investigated. In addition, tests were performed in which thermocouples were imbedded into the various test specimens to obtain temperature-time histories during abrasion.

[An in vitro investigation of wear resistance and hardness of three kinds of new composite resins].

PubMed

Wang, Li-kai; Shi, Lian-shui; Zhu, Hong-shui

2008-02-01

To evaluate wear resistance and hardness of three kinds of new composite resins. Three kinds of new composite resins, Solidex, Spectrum, Filtek Z350, were tested. Enamel as control group. A refited MG-200 wear machine was used in this study. Scanning electron microscope (SEM) was used to observe the friction surface of each tested material. Hardness of each tested material was determined by Vickers indentation technique. The data of wear and hardness were analyzed by Mann-Whitney test and 1-way ANOVA. The relationship between the hardness of the composites and the amount of wear of them was determined by a regression analysis method. Filtek Z350 showed the lowest volumetric wear and highest Vickers hardness in the composites (P < 0.05). No significant differences in wear and hardness were observed between Solidex and Spectrum (P > 0.05). Significant relationships were observed between the hardness of the composites and the amount of wear of them (r = 0.968 6) (P < 0.05). Different wear characters of the friction surface of the tested materials were observed by SEM. Nanofilled composite was superior to the hybrid composite in wear resistance and hardness.

Study Of Nondestructive Techniques For Testing Composites

NASA Technical Reports Server (NTRS)

Roth, D.; Kautz, H.; Draper, S.; Bansal, N.; Bowles, K.; Bashyam, M.; Bishop, C.

1995-01-01

Study evaluates some nondestructive methods for characterizing ceramic-, metal-, and polymer-matrix composite materials. Results demonstrated utility of two ultrasonic methods for obtaining quantitative data on microstructural anomalies in composite materials.

Biomechanical properties of an advanced new carbon/flax/epoxy composite material for bone plate applications.

PubMed

Bagheri, Zahra S; El Sawi, Ihab; Schemitsch, Emil H; Zdero, Rad; Bougherara, Habiba

2013-04-01

This work is part of an ongoing program to develop a new carbon fiber/flax/epoxy (CF/flax/epoxy) hybrid composite material for use as an orthopaedic long bone fracture plate, instead of a metal plate. The purpose of this study was to evaluate the mechanical properties of this new novel composite material. The composite material had a "sandwich structure", in which two thin sheets of CF/epoxy were attached to each outer surface of the flax/epoxy core, which resulted in a unique structure compared to other composite plates for bone plate applications. Mechanical properties were determined using tension, three-point bending, and Rockwell hardness tests. Also, scanning electron microscopy (SEM) was used to characterize the failure mechanism of specimens in tension and three-point bending tests. The results of mechanical tests revealed a considerably high ultimate strength in both tension (399.8MPa) and flexural loading (510.6MPa), with a higher elastic modulus in bending tests (57.4GPa) compared to tension tests (41.7GPa). The composite material experienced brittle catastrophic failure in both tension and bending tests. The SEM images, consistent with brittle failure, showed mostly fiber breakage and fiber pull-out at the fractured surfaces with perfect bonding at carbon fibers and flax plies. Compared to clinically-used orthopaedic metal plates, current CF/flax/epoxy results were closer to human cortical bone, making the material a potential candidate for use in long bone fracture fixation. Copyright © 2013 Elsevier Ltd. All rights reserved.

EFFECTS OF TEMPERATURE AND ENVIRONMENT ON MECHANICAL PROPERTIES OF TWO CHOPPED-FIBER AUTOMOTIVE STRUCTURAL COMPOSITES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruggles-Wrenn, M.B.

2003-10-06

The Durability of Lightweight Composite Structures Project was established at Oak Ridge National Laboratory (ORNL) by the U.S. Department of Energy to provide the experimentally-based, durability-driven design guidelines necessary to assure long-term structural integrity of automotive composite components. The initial focus of the ORNL Durability Project was on composite materials consisting of polyurethane reinforced with E-glass. Current focus of the project is on composite materials reinforced with carbon fibers. The primary purpose of this report is to provide the individual specimen test date. Basic mechanical property testing and results for two chopped-fiber composite materials, one reinforced with glass- and themore » other with carbon fiber are provided. Both materials use the same polyurethane matrix. Preforms for both materials were produced using the P4 process. Behavioral trends, effects of temperature and environment, and corresponding design knockdown factors are established for both materials. Effects of prior short-time loads and of prior thermal cycling are discussed.« less

Damage progression in Composite Structures

NASA Technical Reports Server (NTRS)

Minnetyan, Levon

1996-01-01

A computational simulation tool is used to evaluate the various stages of damage progression in composite materials during Iosipescu sheat testing. Unidirectional composite specimens with either the major or minor material axis in the load direction are considered. Damage progression characteristics are described for each specimen using two types of boundary conditions. A procedure is outlined regarding the use of computational simulation in composites testing. Iosipescu shear testing using the V-notched beam specimen is a convenient method to measure both shear strength and shear stiffness simultaneously. The evaluation of composite test response can be made more productive and informative via computational simulation of progressive damage and fracture. Computational simulation performs a complete evaluation of laminated composite fracture via assessment of ply and subply level damage/fracture processes.

Heat release rate of wood-plastic composites

Treesearch

N. M. Stark; R. H. White; C. M. Clemons

1997-01-01

Wood-plastic composites are becoming more important as a material that fulfills recycling needs. In this study, fire performance tests were conducted on several compositions of wood and plastic materials using the Ohio State University rate of heat release apparatus. Test results included five-minute average heat release rate in kW/m2 (HRR avg) and maximum heat release...

Influence of artificial saliva on abrasive wear and microhardness of dental composites filled with nanoparticles.

PubMed

Mayworm, Camila D; Camargo, Sérgio S; Bastian, Fernando L

2008-09-01

The aim of this study is to compare the wear resistance and hardness of two dental nanohybrid composites and to evaluate the influence of artificial saliva storage on those properties. Specimens were made from two commercial nanohybrid dental composites (Esthet-X-Dentsply and Filtek Supreme-3M). Abrasion tests were carried out in a ball-cratering machine (three body abrasion) and microscopic analysis of the wear surfaces was made using optical and scanning electron microscopy; hardness was quantified by Vickers hardness test. Those tests were repeated on specimens stored in artificial saliva. Results show that the wear rate of the studied materials is within 10(-7)mm(3)/Nmm range, one of the composites presenting wear rate twice as large as the other. After storage in artificial saliva, the wear resistance increases for both materials. Microhardness of the composites is around 52 and 64HV, Esthet-X presents higher hardness values than Filtek Supreme. After storage in artificial saliva, the microhardness of both materials decreases. Data were analyzed using ANOVA test, p < or = 0.05. Artificial saliva storage increases the materials' wear resistance, suggesting that in both materials bulk post-cure takes place and saliva absorption occurs only on the surface of the composites. This effect was confirmed by comparing the Vickers hardness before and after artificial saliva treatment and FTIR analyses. Surface microhardness of the composites decreases after storage in artificial saliva whereas bulk microhardness of the materials increases.

Toxicity testing of restorative dental materials using brine shrimp larvae (Artemia salina).

PubMed

Milhem, Manar M; Al-Hiyasat, Ahmad S; Darmani, Homa

2008-01-01

This study investigated the effect of extracts of different composites, glass ionomer cement (GIC)s and compomers on the viability of brine shrimp larvae. Ethanolic extracts of four dental composites (Z-100; Solitaire 2; Filtek P60 and Synergy), a conventional GIC (Ketac-Fil), a resin-modified glass ionomer cement (Vitremer), two compomers (F2000; Dyract AP), and a flowable compomer (Dyract Flow) were prepared from each material. Following evaporation of the ethanol, the extracts were resuspended in distilled water, which was then used to test the effects on the viability of brine shrimp larvae. For the composites, the extract of Synergy was the least toxic (88% viability) followed by the extracts of Solitaire 2, Z100 and P60 (75%, 67.5% and 50% viability, respectively). One-way ANOVA revealed highly significant differences between the resin composite materials (p<0.001). Follow-up comparison between the composite groups by Tukey's pairwise multiple-comparison test (alpha =0.05) showed that the extract of Synergy was significantly less toxic than the extracts of all the other materials except that of Solitaire 2. The compomers showed 100% lethality, while the percentage of viable larvae for the extracts of Ketac-Fil, and Vitremer were 32.3%, and 37.0%, respectively. One-way ANOVA revealed highly significant differences between the groups of materials (p<0.001). Follow-up comparison between the groups by Tukey's test (alpha = 0.05) showed that the toxic effect of the extracts of the compomers were significantly greater than that of Ketac-Fil, and Vitremer. The differences in the toxic effects of Vitremer and Ketac-Fil were not statistically significant. In conclusion, the toxicity of composite materials varied according to their chemical composition. Compomers were the most lethal materials to brine shrimp larvae followed by GICs and then composites.

Fracture resistance of endodontically treated teeth restored with short fiber composite used as a core material-An in vitro study.

PubMed

Garlapati, Tejesh Gupta; Krithikadatta, Jogikalmat; Natanasabapathy, Velmurugan

2017-10-01

This in-vitro study tested the fracture resistance of endodontically treated molars with Mesial-Occluso-Distal (MOD) cavities restored with fibre reinforced composite material everX posterior in comparision with hybrid composite and ribbond fiber composite. Fifty intact freshly extracted human mandibular first molars were collected and were randomly divided into five groups (n=10). Group 1: positive control (PC) intact teeth without any endodontic preparation. In groups 2 through 6 after endodontic procedure standard MOD cavities were prepared and restored with their respective core materials as follows: group 2, negative control (NC) left unrestored or temporary flling was applied. Group 3, Hybrid composite (HC) as a core material (Te-Econom Plus Ivoclar Vivadent Asia) group 4, Ribbond (Ribbond; Seattle, WA, USA)+conventional composite resin (RCR) group 5, everX posterior (everX Posterior GC EUROPE)+conventional composite resin (EXP) after thermocycling fracture resistance for the samples were tested using universal testing machine. The results were analysed using ANOVA and Tukey's HSD post hoc tests. Mean fracture resistance (in Newton, N) was group 1: 1568.4±221.71N, group 2: 891.0±50.107N, group 3: 1418.3±168.71N, group 4:1716.7±199.51N and group 5: 1994.8±254.195N. Among the materials tested, endodontically treated teeth restored with everX posterior fiber reinforced composite showed superior fracture resistance. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

Mechanical and Vibration Testing of Carbon Fiber Composite Material with Embedded Piezoelectric Sensors

NASA Technical Reports Server (NTRS)

Duffy, Kirsten P.; Lerch, Bradley A.; Wilmoth, Nathan G.; Kray, Nicholas; Gemeinhardt, Gregory

2012-01-01

Piezoelectric materials have been proposed as a means of decreasing turbomachinery blade vibration either through a passive damping scheme, or as part of an active vibration control system. For polymer matrix fiber composite (PMFC) blades, the piezoelectric elements could be embedded within the blade material, protecting the brittle piezoceramic material from the airflow and from debris. Before implementation of a piezoelectric element within a PMFC blade, the effect on PMFC mechanical properties needs to be understood. This study attempts to determine how the inclusion of a packaged piezoelectric patch affects the material properties of the PMFC. Composite specimens with embedded piezoelectric patches were tested in four-point bending, short beam shear, and flatwise tension configurations. Results show that the embedded piezoelectric material does decrease the strength of the composite material, especially in flatwise tension, attributable to failure at the interface or within the piezoelectric element itself. In addition, the sensing properties of the post-cured embedded piezoelectric materials were tested, and performed as expected. The piezoelectric materials include a non-flexible patch incorporating solid piezoceramic material, and two flexible patch types incorporating piezoelectric fibers. The piezoceramic material used in these patches was Navy Type-II PZT.

Characterization and Analysis of Triaxially Braided Polymer Composites under Static and Impact Loads

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Roberts, Gary D.; Blinzler, Brina J.; Kohlman, Lee W.; Binienda, Wieslaw K.

2012-01-01

In order to design impact resistant aerospace components made of triaxially-braided polymer matrix composite materials, a need exists to have reliable impact simulation methods and a detailed understanding of the material behavior. Traditional test methods and specimen designs have yielded unrealistic material property data due to material mechanisms such as edge damage. To overcome these deficiencies, various alternative testing geometries such as notched flat coupons have been examined to alleviate difficulties observed with standard test methods. The results from the coupon level tests have been used to characterize and validate a macro level finite element-based model which can be used to simulate the mechanical and impact response of the braided composites. In the analytical model, the triaxial braid unit cell is approximated by using four parallel laminated composites, each with a different fiber layup, which roughly simulates the braid architecture. In the analysis, each of these laminated composites is modeled as a shell element. Currently, each shell element is considered to be a smeared homogeneous material. Simplified micromechanics techniques and lamination theory are used to determine the equivalent stiffness properties of each shell element, and results from the coupon level tests on the braided composite are used to back out the strength properties of each shell element. Recent improvements to the model include the incorporation of strain rate effects into the model. Simulations of ballistic impact tests have been carried out to investigate and verify the analysis approach.

Preparation of 24 ternary thin film materials libraries on a single substrate in one experiment for irreversible high-throughput studies.

PubMed

Buenconsejo, Pio John S; Siegel, Alexander; Savan, Alan; Thienhaus, Sigurd; Ludwig, Alfred

2012-01-09

For different areas of combinatorial materials science, it is desirable to have multiple materials libraries: especially for irreversible high-throughput studies, like, for example, corrosion resistance testing in different media or annealing of complete materials libraries at different temperatures. Therefore a new combinatorial sputter-deposition process was developed which yields 24 materials libraries in one experiment on a single substrate. It is discussed with the example of 24 Ti-Ni-Ag materials libraries. They are divided based on the composition coverage and orientation of composition gradient into two sets of 12 nearly identical materials libraries. Each materials library covers at least 30-40% of the complete ternary composition range. An acid etch test in buffered-HF solution was performed, illustrating the feasibility of our approach for destructive materials characterization. The results revealed that within the composition range of Ni < 30 at.%, the films were severely etched. The composition range which shows reversible martensitic transformations was confirmed to be outside this region. The high output of the present method makes it attractive for combinatorial studies requiring multiple materials libraries.

Advanced composite aileron for L-1011 transport aircraft: Design and analysis

NASA Technical Reports Server (NTRS)

Griffin, C. F.; Fogg, L. D.; Dunning, E. G.

1981-01-01

Detail design of the composite aileron has been completed. The aileron design is a multi-rib configuration with single piece upper and lower covers mechanically fastened to the substructure. Covers, front, spar and ribs are fabricated with graphite/epoxy tape or fabric composite material. The design has a weight savings of 23 percent compared to the aluminum aileron. The composite aileron has 50 percent fewer fasteners and parts than the metal aileron and is predicted to be cost competitive. Structural integrity of the composite aileron was verified by structural analysis and an extensive test program. Static, failsafe, and vibration analyses have been conducted on the composite aileron using finite element models and specialized computer programs for composite material laminates. The fundamental behavior of the composite materials used in the aileron was determined by coupon tests for a variety of environmental conditions. Critical details of the design were interrogated by static and fatigue tests on full-scale subcomponents and subassemblies of the aileron.

[Studies on the dynamic durability of dental restorative materials. Part 4. Materials evaluation of initial and fatigue specimen for composite resins by acoustic emission method].

PubMed

Kondo, S; Okawa, S; Hanawa, T; Sugawara, T; Ota, M

1981-10-01

Present study is directed towards development for a method of materials evaluation of the static and dynamic properties for dental restorative materials and nondestructive inspection of the dental restorations in oral cavity by acoustic emission (AE) method. AE characteristics and deformation-fracture behavior of hour commercial composite resins under three points bending test are examined in order to evaluate initial and fatigue specimen for conventional and microfilled composite resins. Experimental results obtained are as follows: (1) Deformation-fracture behavior of conventional and microfilled composite resins exhibits different mode, corresponding to relatively brittle and ductile fracture behavior, respectively. Therefore, the primary sources of AE for conventional and microfilled composite resins under bending test are related mainly to the nucleation and propagation of cracks and plastic deformation, respectively. (2) In conventional composite resins under bending test, the burst type AE signal of higher amplitude and shorter decay time and more many AE total counts tend to be observed. In microfilled composite resins under bending test, the burst type AE signal of lower amplitude and longer decay time and more a few total counts tend to be observed. (3) Composite resins, particularly conventional composite resins under unload and repeated bending load are indicative of different AE characteristics. Accordingly, application of AE method for composite resins offers a method to evaluate the static and dynamic strength of composite resins. (4) In conventional composite resins under bending test, as characteristic AE are observed in a few stress regions before fracture, it may be possible to monitor nondestructively the restorations in oral cavity by using AE method.

Modeling of Failure for Analysis of Triaxial Braided Carbon Fiber Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Littell, Justin D.; Binienda, Wieslaw K.

2010-01-01

In the development of advanced aircraft-engine fan cases and containment systems, composite materials are beginning to be used due to their low weight and high strength. The design of these structures must include the capability of withstanding impact loads from a released fan blade. Relatively complex triaxially braided fiber architectures have been found to yield the best performance for the fan cases. To properly work with and design these structures, robust analytical tools are required that can be used in the design process. A new analytical approach models triaxially braided carbon fiber composite materials within the environment of a transient dynamic finite-element code, specifically the commercially available transient dynamic finite-element code LS-DYNA. The geometry of the braided composites is approximated by a series of parallel laminated composites. The composite is modeled by using shell finite elements. The material property data are computed by examining test data from static tests on braided composites, where optical strain measurement techniques are used to examine the local strain variations within the material. These local strain data from the braided composite tests are used along with a judicious application of composite micromechanics- based methods to compute the stiffness properties of an equivalent unidirectional laminated composite required for the shell elements. The local strain data from the braided composite tests are also applied to back out strength and failure properties of the equivalent unidirectional composite. The properties utilized are geared towards the application of a continuum damage mechanics-based composite constitutive model available within LS-DYNA. The developed model can be applied to conduct impact simulations of structures composed of triaxially braided composites. The advantage of this technology is that it facilitates the analysis of the deformation and damage response of a triaxially braided polymer matrix composite within the environment of a transient dynamic finite-element code such as LS-DYNA in a manner which accounts for the local physical mechanisms but is still computationally efficient. This methodology is tightly coupled to experimental tests on the braided composite, which ensures that the material properties have physical significance. Aerospace or automotive companies interested in using triaxially braided composites in their structures, particularly for impact or crash applications, would find the technology useful. By the development of improved design tools, the amount of very expensive impact testing that will need to be performed can be significantly reduced.

Thermoplastic composites for veneering posterior teeth-a feasibility study.

PubMed

Gegauff, Anthony G; Garcia, Jose L; Koelling, Kurt W; Seghi, Robert R

2002-09-01

This pilot study was conducted to explore selected commercially-available thermoplastic composites that potentially had physical properties superior to currently available dental systems for restoring esthetic posterior crowns. Polyurethane, polycarbonate, and poly(ethylene/tetrafluoroethylene) (ETFE) composites and unfilled polyurethane specimens were injection molded to produce shapes adaptive to five standardized mechanical tests. The mechanical testing included abrasive wear rate, yield strength, apparent fracture toughness (strength ratio), flexural strength, and compressive strength. Compared to commercially available dental composites, abrasion wear rates were lower for all materials tested, yield strength was greater for the filled polycarbonates and filled polyurethane resins, fracture toughness testing was invalid (strength ratios were calculated for comparison of the pilot test materials), flexural strength was roughly similar except for the filled ETFE which was significantly greater, and compressive strength was lower. Commercially available thermoplastic resin composites, such as polyurethane, demonstrate the potential for development of an artificial crown material which exceeds the mechanical properties of currently available esthetic systems, if compressive strength can be improved.

Materials, Manufacturing and Test Development of a Composite Fan Blade Leading Edge Subcomponent for Improved Impact Resistance

NASA Technical Reports Server (NTRS)

Handschuh, Katherine M.; Miller, Sandi G.; Sinnott, Matthew J.; Kohlman, Lee W.; Roberts, Gary D.; Pereira, J. Michael; Ruggeri, Charles R.

2014-01-01

Application of polymer matrix composite materials for jet engine fan blades is becoming attractive as an alternative to metallic blades; particularly for large engines where significant weight savings are recognized on moving to a composite structure. However, the weight benefit of the composite of is offset by a reduction of aerodynamic efficiency resulting from a necessary increase in blade thickness; relative to the titanium blades. Blade dimensions are largely driven by resistance to damage on bird strike. Further development of the composite material is necessary to allow composite blade designs to approximate the dimensions of a metallic fan blade. The reduction in thickness over the state of the art composite blades is expected to translate into structural weight reduction, improved aerodynamic efficiency, and therefore reduced fuel consumption. This paper presents test article design, subcomponent blade leading edge fabrication, test method development, and initial results from ballistic impact of a gelatin projectile on the leading edge of composite fan blades. The simplified test article geometry was developed to realistically simulate a blade leading edge while decreasing fabrication complexity. Impact data is presented on baseline composite blades and toughened blades; where a considerable improvement to impact resistance was recorded.

Materials, Manufacturing, and Test Development of a Composite Fan Blade Leading Edge Subcomponent for Improved Impact Resistance

NASA Technical Reports Server (NTRS)

Miller, Sandi G.; Handschuh, Katherine; Sinnott, Matthew J.; Kohlman, Lee W.; Roberts, Gary D.; Martin, Richard E.; Ruggeri, Charles R.; Pereira, J. Michael

2015-01-01

Application of polymer matrix composite materials for jet engine fan blades is becoming attractive as an alternative to metallic blades; particularly for large engines where significant weight savings are recognized on moving to a composite structure. However, the weight benefit of the composite is offset by a reduction of aerodynamic efficiency resulting from a necessary increase in blade thickness; relative to the titanium blades. Blade dimensions are largely driven by resistance to damage on bird strike. Further development of the composite material is necessary to allow composite blade designs to approximate the dimensions of a metallic fan blade. The reduction in thickness over the state of the art composite blades is expected to translate into structural weight reduction, improved aerodynamic efficiency, and therefore reduced fuel consumption. This paper presents test article design, subcomponent blade leading edge fabrication, test method development, and initial results from ballistic impact of a gelatin projectile on the leading edge of composite fan blades. The simplified test article geometry was developed to realistically simulate a blade leading edge while decreasing fabrication complexity. Impact data is presented on baseline composite blades and toughened blades; where a considerable improvement to impact resistance was recorded.

Evaluation of mechanical properties of hybrid fiber (hemp, jute, kevlar) reinforced composites

NASA Astrophysics Data System (ADS)

Suresha, K. V.; Shivanand, H. K.; Amith, A.; Vidyasagar, H. N.

2018-04-01

In today's world composites play wide role in all the engineering fields. The reinforcement of composites decides the properties of the material. Natural fiber composites compared to synthetic fiber possesses poor mechanical properties. The solution for this problem is to use combination of natural fiber and synthetic fiber. Hybridization helps to improve the overall mechanical properties of the material. In this study, hybrid reinforced composites of Hemp fabric/Kevlar fabric/Epoxy and Jute fabric/ Kevlar fabric/Epoxy composites are fabricated using Simple hand layup technique followed by Vacuum bagging process. Appropriate test methods as per standards and guidelines are followed to analyze mechanical behavior of the composites. The mechanical characteristics like tensile, compression and flexural properties of the hybrid reinforced composites are tested as per the ASTM standards by series of tensile test; compression test and three point bending tests were conducted on the hybrid composites. A quantitative relationship between the Hemp fabric/Kevlar fabric/Epoxy and Jute/ Kevlar fabric/Epoxy has been established with constant thickness.

Effect of in-office bleaching agents on physical properties of dental composite resins.

PubMed

Mourouzis, Petros; Koulaouzidou, Elisabeth A; Helvatjoglu-Antoniades, Maria

2013-04-01

The physical properties of dental restorative materials have a crucial effect on the longevity of restorations and moreover on the esthetic demands of patients, but they may be compromised by bleaching treatments. The purpose of this study was to evaluate the effects of in-office bleaching agents on the physical properties of three composite resin restorative materials. The bleaching agents used were hydrogen peroxide and carbamide peroxide at high concentrations. Specimens of each material were prepared, cured, and polished. Measurements of color difference, microhardness, and surface roughness were recorded before and after bleaching and data were examined statistically by analysis of variance (ANOVA) and Tukey HSD post-hoc test at P < .05. The measurements showed that hue and chroma of silorane-based composite resin altered after the bleaching procedure (P < .05). No statistically significant differences were found when testing the microhardness and surface roughness of composite resins tested (P > .05). The silorane-based composite resin tested showed some color alteration after bleaching procedures. The bleaching procedure did not alter the microhardness and the surface roughness of all composite resins tested.

Estimation of Complex Permittivity of Composite Multilayer Material at Microwave Frequency Using Waveguide Measurements

NASA Technical Reports Server (NTRS)

Deshpande, Manohar D.; Dudley, Kenneth

2003-01-01

A simple method is presented to estimate the complex dielectric constants of individual layers of a multilayer composite material. Using the MatLab Optimization Tools simple MatLab scripts are written to search for electric properties of individual layers so as to match the measured and calculated S-parameters. A single layer composite material formed by using materials such as Bakelite, Nomex Felt, Fiber Glass, Woven Composite B and G, Nano Material #0, Cork, Garlock, of different thicknesses are tested using the present approach. Assuming the thicknesses of samples unknown, the present approach is shown to work well in estimating the dielectric constants and the thicknesses. A number of two layer composite materials formed by various combinations of above individual materials are tested using the present approach. However, the present approach could not provide estimate values close to their true values when the thicknesses of individual layers were assumed to be unknown. This is attributed to the difficulty in modelling the presence of airgaps between the layers while doing the measurement of S-parameters. A few examples of three layer composites are also presented.

Caracterisation des proprietes dielectriques de materiaux composites a base de polyethylene terephtalate recycle

NASA Astrophysics Data System (ADS)

Mebarki, Fouzia

The aim of this study is to examine the possibility of using thermoplastic composite materials for electrical applications such as supports of automotive engine ignition systems. We are particularly interested in composites based on recycled polyethylene terephtalate (PET). Conventional isolations like PET cannot meet the new prescriptive requirements. The introduction of reinforcement materials, such as glass fibers and mica can improve the mechanical characteristics of these materials. However, this enhancement may also reduce electrical properties especially since these composites have to be used under severe thermal and electric stresses. In order to estimate PET composite insulation lifetimes, accelerated aging tests were carried out at temperatures ranging from room temperature to 140°C and at a frequency of 300Hz. Studies at high temperature will help to identify the service temperature of candidate materials. Dielectric breakdown tests have been made on a large number of samples according to the standard of dielectric strength tests of solid insulating ASTM D-149. These tests have to identify the problematic samples and to check solid insulation quality. The different knowledge gained from this analysis was used to predict material performance. This will give the company the possibility to improve existing formulations and subsequently develop a material having electrical and thermal properties suitable for this application.

Method and Apparatus for Non-Destructive Evaluation of Materials

NASA Technical Reports Server (NTRS)

Washabaugh, Andrew P. (Inventor); Lyons, Robert (Inventor); Thomas, Zachary (Inventor); Martin, Christopher (Inventor); Goldfine, Neil J. (Inventor)

2017-01-01

Methods and apparatus for characterizing composite materials for manufacturing quality assurance (QA), periodic inspection during the useful life, or for forensic analysis/material testing. System are provided that relate eddy-current sensor responses to the fiber layup of a composite structure, the presence of impact damage on a composite structure with or without a metal liner, volumetric stress within the composite, fiber tow density, and other NDE inspection requirements. Also provided are systems that determine electromagnetic material properties and material dimensions of composite materials from capacitive sensor inspection measurements. These properties are related to the presence of buried defects in non-conductive composite materials, moisture ingress, aging of the material due to service or environmental/thermal exposure, or changes in manufacturing quality.

Method and Apparatus for Non-Destructive Evaluation of Materials

NASA Technical Reports Server (NTRS)

Lyons, Robert (Inventor); Martin, Christopher (Inventor); Washabaugh, Andrew P. (Inventor); Goldfine, Neil J. (Inventor); Thomas, Zachary (Inventor); Jablonski, David A. (Inventor)

2015-01-01

Methods and apparatus for characterizing composite materials for manufacturing quality assurance (QA), periodic inspection during the useful life, or for forensic analysis/material testing. System are provided that relate eddy-current sensor responses to the fiber layup of a composite structure, the presence of impact damage on a composite structure with or without a metal liner, volumetric stress within the composite, fiber tow density, and other NDE inspection requirements. Also provided are systems that determine electromagnetic material properties and material dimensions of composite materials from capacitive sensor inspection measurements. These properties are related to the presence of buried defects in non-conductive composite materials, moisture ingress, aging of the material due to service or environmental/thermal exposure, or changes in manufacturing quality.

Standard methods for filled hole tension testing of textile composites

NASA Technical Reports Server (NTRS)

Portanova, M. A.; Masters, J. E.

1995-01-01

The effects of two test specimen geometry parameters, the specimen width and W/D ratio, on filled-hole tensile strength were determined for textile composite materials. Test data generated by Boeing and Lockheed on 2-D and 3-D braids, and 3-D weaves were used to make these evaluations. The investigation indicated that filled-hole tensile-strength showed little sensitivity to either parameter. Test specimen configurations used in open-hole tension tests, such as those suggested by ASTM D5766 - Standard Test Method for Open Hole Tensile Strength of Polymer Matrix Composite Laminates or those proposed by MIL-HDBK-17-lD should provide adequate results for material comparisons studies. Comparisons of the materials' open-hole and filled-hole tensile strengths indicated that the latter were generally lower than the former. The 3-D braids were the exception; their filled-hole strengths were unexpected larger than their open-hole strengths. However, these increases were small compared to the scatter in the data. Thus, filled hole tension may be a critical design consideration for textile composite materials.

Accceleration of Fatigue Tests of Polymer Composite Materials by Using High-Frequency Loadings

NASA Astrophysics Data System (ADS)

Apinis, R.

2004-03-01

The possibility of using high-frequency loading in fatigue tests of polymer composite materials is discussed. A review of studies on the use of high-frequency loading of organic-, carbon-, and glass-fiber-reinforced plastics is presented. The results obtained are compared with those found in conventional low-frequency loadings. A rig for fatigue tests of rigid materials at loading frequencies to 500 Hz is described, and results for an LM-L1 unidirectional glass-fiber plastic in loadings with frequencies of 17 and 400 Hz are given. These results confirm that it is possible to accelerate the fatigue testing of polymer composite materials by considerably increasing the loading frequency. The necessary condition for using this method is an intense cooling of specimens to prevent them from vibration heating.

Industry technology assessment of graphite-polymide composite materials. [conferences

NASA Technical Reports Server (NTRS)

1975-01-01

An assessment of the current state of the art and the future prospects for graphite polyimide composite material technology is presented. Presentations and discussions given at a minisymposium of major issues on the present and future use, availability, processing, manufacturing, and testing of graphite polyimide composite materials are summarized.

New Coll-HA/BT composite materials for hard tissue engineering.

PubMed

Zanfir, Andrei Vlad; Voicu, Georgeta; Busuioc, Cristina; Jinga, Sorin Ion; Albu, Madalina Georgiana; Iordache, Florin

2016-05-01

The integration of ceramic powders in composite materials for bone scaffolds can improve the osseointegration process. This work was aimed to the synthesis and characterization of new collagen-hydroxyapatite/barium titanate (Coll-HA/BT) composite materials starting from barium titanate (BT) nanopowder, hydroxyapatite (HA) nanopowder and collagen (Coll) gel. BT nanopowder was produced by combining two wet-chemical approaches, sol-gel and hydrothermal methods. The resulting materials were characterized in terms of phase composition and microstructure by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. Moreover, the biocompatibility and bioactivity of the composite materials were assessed by in vitro tests. The synthesized BT particles exhibit an average size of around 35 nm and a spherical morphology, with a pseudo-cubic or tetragonal symmetry. The diffraction spectra of Coll-HA and Coll-HA/BT composite materials indicate a pronounced interaction between Col and the mineral phases, meaning a good mineralization of Col fibres. As well, the in vitro tests highlight excellent osteoinductive properties for all biological samples, especially for Coll-HA/BT composite materials, fact that can be attributed to the ferromagnetic properties of BT. Copyright © 2016 Elsevier B.V. All rights reserved.

VZLUSAT-1: verification of new materials and technologies for space

NASA Astrophysics Data System (ADS)

Daniel, Vladimir; Urban, Martin; Nentvich, Ondrej; Stehlikova, Veronika

2016-09-01

CubeSats are a good opportunity to test new technologies and materials on orbit. These innovations can be later used for improving of properties and life length of Cubesat or other satellites as well. VZLUSAT-1 is a small satellite from the CubeSat family, which will carry a wide scale of payloads with different purposes. The poster is focused on measuring of degradation and properties measurement of new radiation hardened composite material in orbit due to space environment. Material properties changes can be studied by many methods and in many disciplines. One payload measures mechanical changes in dependence on Young's modulus of elasticity which is got from non-destructive testing by mechanical vibrations. The natural frequencies we get using Fast Fourier Transform. The material is tested also by several thermometers which measure heat distribution through the composite, as well as reflectivity in dependence on different coatings. The satellite also will measure the material radiation shielding properties. There are PIN diodes which measure the relative shielding efficiency of composite and how it will change in time in space environment. Last one of material space testing is measurement of outgassing from tested composite material. It could be very dangerous for other parts of satellite, like detectors, when anything was outgassing, for example water steam. There are several humidity sensors which are sensitive to steam and other gases and measures temperatures as well.

Research on the preparation, biocompatibility and bioactivity of magnesium matrix hydroxyapatite composite material.

PubMed

Linsheng, Li; Guoxiang, Lin; Lihui, Li

2016-08-12

In this paper, magnesium matrix hydroxyapatite composite material was prepared by electrophoretic deposition method. The optimal process parameters of electrophoretic deposition were HA suspension concentration of 0.02 kg/L, aging time of 10 days and voltage of 60 V. Animal experiment and SBF immersion experiment were used to test the biocompatibility and bioactivity of this material respectively. The SD rats were divided into control group and implant group. The implant surrounding tissue was taken to do tissue biopsy, HE dyed and organizational analysis after a certain amount of time in the SD rat body. The biological composite material was soaked in SBF solution under homeothermic condition. After 40 days, the bioactivity of the biological composite material was evaluated by testing the growth ability of apatite on composite material. The experiment results showed that magnesium matrix hydroxyapatite biological composite material was successfully prepared by electrophoretic deposition method. Tissue hyperplasia, connective tissue and new blood vessels appeared in the implant surrounding soft tissue. No infiltration of inflammatory cells of lymphocytes and megakaryocytes around the implant was found. After soaked in SBF solution, a layer bone-like apatite was found on the surface of magnesium matrix hydroxyapatite biological composite material. The magnesium matrix hydroxyapatite biological composite material could promot calcium deposition and induce bone-like apatite formation with no cytotoxicity and good biocompatibility and bioactivity.

FRACTURE STRENGTH AND TIME DEPENDENT PROPERTIES OF 0/90 AND ±55-BRAIDED WEAVE SiC/SiC TYPE-S FIBER COMPOSITES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henager, Charles H.

PNNL has performed mechanical property tests on two types of Hi-Nicalon Type-S fiber SiC/SiC composites for the general purpose of evaluating such composites for control rod guide tube applications in the NGNP high-temperature gas-cooled reactor design. The mechanical testing consisted of 4-point bend strength, 4-point single-edge notched bend fracture toughness, and 4-point bend slow crack growth testing on both composites from ambient to 1600°C (1873K). The two composite materials that were tested included a ±55°-braided-weave composite with Type-S fibers inclined at 55° to the principal composite axes to simulate a braided tube architecture and a Type-S 0/90 satin-weave composite asmore » a reference material.« less

Radiopacity of Composite Luting Cements Using a Digital Technique.

PubMed

Dukic, Walter

2017-01-10

The aim of this in vitro study was to evaluate the radiopacity of 20 common dental composite luting materials using a digital technique. A 1-mm-thick specimen of each material with a human tooth slice and aluminium step wedge were tested using digital radiographs under four combinations of exposure and voltage. The radiopacity in pixels was determined using computer software. The equivalent thickness of aluminium for each material was then calculated based on the calibration curve. All tested materials except one had higher radiopacity than dentin (p > α; α  =  0.01), and 80% of the materials had radiopacity above enamel value (p > α; α  =  0.01). Moreover, 40% of tested materials had radiopacity of three times above the minimal International Organization for Standardization (ISO) values for composite luting cements. At all exposure values, the highest radiopacity was for Solocem and Multilink groups of materials, at three to six times above dentin radiopacity. Only Variolink Veneer showed radiopacity below dentin and enamel. Composite luting materials should have radiopacity above ISO values or greater than the dentin or enamel equivalent. The highest radiopacity values were for the Solocem and Multilink family composite luting cements. Clinicians should choose materials with high radiopacity values, and manufacturers should be aware of the radiopacity values when introducing materials on the market. © 2017 by the American College of Prosthodontists.

Manufacturing and testing of active composite panels with embedded piezoelectric sensors and actuators: wires out by molded-in holes

NASA Astrophysics Data System (ADS)

Ghasemi-Nejhad, Mehrdad N.; Pourjalali, Saeid

2003-08-01

This work presents manufacturing and testing of active composite panels (ACPs) with embedded piezoelectric sensors and actuators. The composite material employed here is a plain weave carbon epoxy prepreg fabric with about 0.33 mm ply thickness. The piezoelectric patches employed here are Continuum Control Corporation, CCC, (recently Continuum Photonics, Inc) active fiber composite patches with 0.33 mm thickness, i.e. close to the composite ply thickness. Composite cut-out layers are used to fill the space around the embedded piezoelectric patches to minimize the problems associated with ply drops in composites. The piezoelectric patches were embedded inside the composite laminate. High-temperature wires were soldered to the piezoelectric leads, insulated from the carbon substructure by high-temperature materials, and were taken out of the composite laminates employing a molded-in hole technique that reduces the stress concentration as opposed to a drilled hole, and thereby enhancing the performance of the composite structure. The laminated ACP"s were co-cured inside an autoclave employing the cure cycle recommended by the composite material supplier. The curie temperature of the embedded piezoelectric patches should be well above the curing temperature of the composite materials as was the case here. The manufactured ACP beams and plates were trimmed and then tested for their functionality. Vibration suppression as well as simultaneous vibration suppression and precision positioning tests, using PID control as well as Hybrid Adaptive Control techniques were successfully conducted on the manufactured ACP beams and their functionality were demonstrated. Recommendations on the use of this embedding technique for ACPs are provided.

Nano lead oxide and epdm composite for development of polymer based radiation shielding material: Gamma irradiation and attenuation tests

NASA Astrophysics Data System (ADS)

Özdemir, T.; Güngör, A.; Akbay, I. K.; Uzun, H.; Babucçuoglu, Y.

2018-03-01

It is important to have a shielding material that is not easily breaking in order to have a robust product that guarantee the radiation protection of the patients and radiation workers especially during the medical exposure. In this study, nano sized lead oxide (PbO) particles were used, for the first time, to obtain an elastomeric composite material in which lead oxide nanoparticles, after the surface modification with silane binding agent, was used as functional material for radiation shielding. In addition, the composite material including 1%, 5%, 10%, 15% and 20% weight percent nano sized lead oxide was irradiated with doses of 81, 100 and 120 kGy up to an irradiation period of 248 days in a gamma ray source with an initial dose rate of 21.1 Gy/h. Mechanical, thermal properties of the irradiated materials were investigated using DSC, DMA, TGA and tensile testing and modifications in thermal and mechanical properties of the nano lead oxide containing composite material via gamma irradiation were reported. Moreover, effect of bismuth-III oxide addition on radiation attenuation of the composite material was investigated. Nano lead oxide and bismuth-III oxide particles were mixed with different weight ratios. Attenuation tests have been conducted to determine lead equivalent values for the developed composite material. Lead equivalent thickness values from 0.07 to 0.65 (2-6 mm sample thickness) were obtained.

Evaluating Composite Sampling Methods of Bacillus spores at Low Concentrations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hess, Becky M.; Amidan, Brett G.; Anderson, Kevin K.

Restoring facility operations after the 2001 Amerithrax attacks took over three months to complete, highlighting the need to reduce remediation time. The most time intensive tasks were environmental sampling and sample analyses. Composite sampling allows disparate samples to be combined, with only a single analysis needed, making it a promising method to reduce response times. We developed a statistical experimental design to test three different composite sampling methods: 1) single medium single pass composite: a single cellulose sponge samples multiple coupons; 2) single medium multi-pass composite: a single cellulose sponge is used to sample multiple coupons; and 3) multi-medium post-samplemore » composite: a single cellulose sponge samples a single surface, and then multiple sponges are combined during sample extraction. Five spore concentrations of Bacillus atrophaeus Nakamura spores were tested; concentrations ranged from 5 to 100 CFU/coupon (0.00775 to 0.155CFU/cm2, respectively). Study variables included four clean surface materials (stainless steel, vinyl tile, ceramic tile, and painted wallboard) and three grime coated/dirty materials (stainless steel, vinyl tile, and ceramic tile). Analysis of variance for the clean study showed two significant factors: composite method (p-value < 0.0001) and coupon material (p-value = 0.0008). Recovery efficiency (RE) was higher overall using the post-sample composite (PSC) method compared to single medium composite from both clean and grime coated materials. RE with the PSC method for concentrations tested (10 to 100 CFU/coupon) was similar for ceramic tile, painted wall board, and stainless steel for clean materials. RE was lowest for vinyl tile with both composite methods. Statistical tests for the dirty study showed RE was significantly higher for vinyl and stainless steel materials, but significantly lower for ceramic tile. These results suggest post-sample compositing can be used to reduce sample analysis time when responding to a Bacillus anthracis contamination event of clean or dirty surfaces.« less

Impact testing of textile composite materials

NASA Technical Reports Server (NTRS)

Portanova, Marc

1995-01-01

The objectives of this report were to evaluate the impact damage resistance and damage tolerance of a variety of textile composite materials. Static indentation and impact tests were performed on the stitched and unstitched uniweave composites constructed from AS4/3501-6 Carbon/Epoxy with a fiberglass yarn woven in to hold the fibers together while being stitched. Compression and tension were measured after the tests to determine the damage resistance, residual strength and the damage tolerance of the specimens.

Evaluating the effect of some mechanical properties for chemically treated various natural fibers reinforced polyester composite

NASA Astrophysics Data System (ADS)

Salih, Wafaa Mahdi; Abdulkader, Niveen Jamal; Salih, Sana Mahdi

2018-05-01

This research were studied the effect of some mechanical properties for composite materials reinforced fiber and prepared from material (polyester with various natural fibers) then studied the effect of chemical treatment on the same fiber immerse in 10% NaOH solution for half an hour and then compared, the results of the same test of composite materials without and with chemical treatment and the results proved that there is a clear effect when treat the fiber compared to non-chemical treatment of the fibers also noted that hemp fibers loaded the stress higher than other fibers for both cases to distinguish them that the hemp fiber has continuous fibers either the other fibers are characterized by the type of cross linking or chopped types in tensile test, and the results of the same test of composite materials without and with chemical treatment and the results proved that the hardness of the fiber composite while the treated fiber composite samples better than the untreated fiber, and from the figures the palm leaf has the highest value than lufa fiber, hemp fiber and the smallest value is in sisal fiber because of the nature of formation fibers materials.

Flight service environmental effects on composite materials and structures

NASA Technical Reports Server (NTRS)

Dexter, H. Benson; Baker, Donald J.

1992-01-01

NASA Langley and the U.S. Army have jointly sponsored programs to assess the effects of realistic flight environments and ground-based exposure on advanced composite materials and structures. Composite secondary structural components were initially installed on commercial transport aircraft in 1973; secondary and primary structural components were installed on commercial helicopters in 1979; and primary structural components were installed on commercial aircraft in the mid-to-late 1980's. Service performance, maintenance characteristics, and residual strength of numerous components are reported. In addition to data on flight components, 10 year ground exposure test results on material coupons are reported. Comparison between ground and flight environmental effects for several composite material systems are also presented. Test results indicate excellent in-service performance with the composite components during the 15 year period. Good correlation between ground-based material performance and operational structural performance has been achieved.

Comparison of wear between occlusal splint materials and resin composite materials.

PubMed

Reyes-Sevilla, M; Kuijs, R H; Werner, A; Kleverlaan, C J; Lobbezoo, F

2018-07-01

Tooth wear in bruxing patients often results in a need for treatment with composite restorations. In some cases, bruxing patients receive an occlusal splint as a protective means as well. However, the wear between these opposing materials has not been investigated yet. The aim of this in vitro study was to assess the wear of different splint materials against resin composite materials. A two-body wear test was conducted using the ACTA wear machine. The materials selected for this study were three composites used for direct restorations (Filtek Z250, CLEARFIL AP-X, and Filtek Supreme XT) and four occlusal splints materials, viz. a polyamide resin (ThermoSens) an conventional (hand-processed), milled and printed polymethylmethacrylate (PMMA). As antagonistic materials, stainless steel, Filtek Supreme XT and CLEARFIL AP-X were used. The wear rate of the seven materials was determined after 200 000 cycles, using a profilometry. The rates were analysed using two-way ANOVA and post hoc Tukey's tests. The wear rates were significantly higher for the conventional and milled PMMA materials than for all other materials (P < .001). The wear rates of printed PMMA and the polyamide resin were comparable to composite wear rates. The antagonist materials have minor or no influence on the amount of wear of the various splint materials (P < .001). In conclusion, different splint materials yielded different wear rates for all antagonist materials tested. Keeping in mind that this study is an experimental in vitro study, this finding enables practitioners to choose the splint material necessary according to their patients' needs. © 2018 John Wiley & Sons Ltd.

Aluminum-thin-film packaged fiber Bragg grating probes for monitoring the maximum tensile strain of composite materials.

PubMed

Im, Jooeun; Kim, Mihyun; Choi, Ki-Sun; Hwang, Tae-Kyung; Kwon, Il-Bum

2014-06-10

In this paper, new fiber Bragg grating (FBG) sensor probes are designed to intermittently detect the maximum tensile strain of composite materials, so as to evaluate the structural health status. This probe is fabricated by two thin Al films bonded to an FBG optical fiber and two supporting brackets, which are fixed on the surface of composite materials. The residual strain of the Al packaged FBG sensor probe is induced by the strain of composite materials. This residual strain can indicate the maximum strain of composite materials. Two types of sensor probes are prepared-one is an FBG with 18 μm thick Al films, and the other is an FBG with 36 μm thick Al films-to compare the thickness effect on the detection sensitivity. These sensor probes are bonded on the surfaces of carbon fiber reinforced plastics composite specimens. In order to determine the strain sensitivity between the residual strain of the FBG sensor probe and the maximum strain of the composite specimen, tensile tests are performed by universal testing machine, under the loading-unloading test condition. The strain sensitivities of the probes, which have the Al thicknesses of 18 and 36 μm, are determined as 0.13 and 0.23, respectively.

Investigation on Failures of Composite Beam and Substrate Concrete due to Drying Shrinkage Property of Repair Materials

NASA Astrophysics Data System (ADS)

Pattnaik, Rashmi Ranjan

2017-06-01

A Finite Element Analysis (FEA) and an experimental study was conducted on composite beam of repair material and substrate concrete to investigate the failures of the composite beam due to drying shrinkage property of the repair materials. In FEA, the stress distribution in the composite beam due to two concentrate load and shrinkage of repair materials were investigated in addition to the deflected shape of the composite beam. The stress distributions and load deflection shapes of the finite element model were investigated to aid in analysis of the experimental findings. In the experimental findings, the mechanical properties such as compressive strength, split tensile strength, flexural strength, and load-deflection curves were studied in addition to slant shear bond strength, drying shrinkage and failure patterns of the composite beam specimens. Flexure test was conducted to simulate tensile stress at the interface between the repair material and substrate concrete. The results of FEA were used to analyze the experimental results. It was observed that the repair materials with low drying shrinkage are showing compatible failure in the flexure test of the composite beam and deform adequately in the load deflection curves. Also, the flexural strength of the composite beam with low drying shrinkage repair materials showed higher flexural strength as compared to the composite beams with higher drying shrinkage value of the repair materials even though the strength of those materials were more.

Experimental characterization of nonlinear, rate-dependent behavior in advanced polymer matrix composites

NASA Technical Reports Server (NTRS)

Gates, Thomas S.

1992-01-01

In order to support materials selection for the next-generation supersonic civilian-passenger transport aircraft, a study has been undertaken to evaluate the material stress/strain relationships needed to describe advanced polymer matrix composites under conditions of high load and elevated temperature. As part of this effort, this paper describes the materials testing which was performed to investigate the viscoplastic behavior of graphite/thermoplastic and graphite/bismaleimide composites. Test procedures, results and data-reduction schemes which were developed for generating material constants for tension and compression loading, over a range of useful temperatures, are explained.

Effect of Microscopic Damage Events on Static and Ballistic Impact Strength of Triaxial Braid Composites

NASA Technical Reports Server (NTRS)

Littell, Justin D.; Binienda, Wieslaw K.; Arnold, William A.; Roberts, Gary D.; Goldberg, Robert K.

2010-01-01

The reliability of impact simulations for aircraft components made with triaxial-braided carbon-fiber composites is currently limited by inadequate material property data and lack of validated material models for analysis. Methods to characterize the material properties used in the analytical models from a systematically obtained set of test data are also lacking. A macroscopic finite element based analytical model to analyze the impact response of these materials has been developed. The stiffness and strength properties utilized in the material model are obtained from a set of quasi-static in-plane tension, compression and shear coupon level tests. Full-field optical strain measurement techniques are applied in the testing, and the results are used to help in characterizing the model. The unit cell of the braided composite is modeled as a series of shell elements, where each element is modeled as a laminated composite. The braided architecture can thus be approximated within the analytical model. The transient dynamic finite element code LS-DYNA is utilized to conduct the finite element simulations, and an internal LS-DYNA constitutive model is utilized in the analysis. Methods to obtain the stiffness and strength properties required by the constitutive model from the available test data are developed. Simulations of quasi-static coupon tests and impact tests of a represented braided composite are conducted. Overall, the developed method shows promise, but improvements that are needed in test and analysis methods for better predictive capability are examined.

Wood-based Tri-Axial Sandwich Composite Materials: Design, Fabrication, Testing, Modeling and Application

Treesearch

Jinghao Li; John F. Hunt; Shaoqin Gong; Zhiyong Cai

2014-01-01

As the demand for sustainable materials increases, there are unique challenges and opportunities to develop light-weight green composites materials for a wide range of applications. Thus wood-based composite materials from renewable forests may provide options for some niche applications while helping to protect our environment. In this paper, the wood-based tri-axial...

Developing Raman spectroscopy for the nondestructive testing of composite materials.

DOT National Transportation Integrated Search

2009-08-01

The proposed research will develop the application of Raman Spectroscopy as a nondestructive evaluation tool for the condition assessment of carbon fiber composites. Composite materials are increasingly being used in engineered structures and compone...

Comparison of the retention of 5 core materials supported by a dental post.

PubMed

Gu, Steven; Isidro, Mario; Deutsch, Allan S; Musikant, Barry L

2006-01-01

This study evaluated the retention of dental post heads (No. 2 Flexi-Post) embedded in 5 core materials (1 automix resin composite, 2 hand-mixed resin composites, and 2 glass ionomers). Samples were prepared by embedding post heads in 4.5-mm-thick disks of core material. The resin composite materials provided significantly more retention than the glass-ionomer-based materials. The post head retention of the automix resin composite was comparable to that of the hand-mixed resin composites. Unlike the resin composite samples, all the glass-ionomer samples fractured during testing. This is an unacceptable condition for a clinically successful restoration.

An Investigation of a Vertical Test Method for Large Deformation Bending of High Strain Composite Laminates

NASA Astrophysics Data System (ADS)

Herrmann, Kelsey M.

Research to date indicates that traditional composite material failure analysis methods are not appropriate for thin laminates in flexure. Thin composite structures subjected to large bending deformations often attain significantly higher strain-to-failure than previously anticipated tensile and compression coupon test data and linear material model assumption predict. At NASA Langley Research Center, a new bend test method is being developed for High Strain Composite (HSC) structures. This method provides an adequate approximation of a pure moment, large deformation bend test for thin-ply, high strain composites to analyze the large strain flexure response of the laminates. The objective of this research was to further develop this new test method to measure the true bending stiffness and strain-to-failure of high strain composite materials. Of primary importance is the ability to characterize composite laminates that are of interest for current NASA deployable structures in both materials and layups. Two separate testing campaigns were performed for the development of the testing procedure. Initially six laminates were bend tested in three different fiber orientations. These laminates were some combination of unidirectional intermediate modulus (IM) carbon, high tenacity (HT) carbon plain weave, and astroquartz plain weave composite materials. The second test campaign was performed as a more detailed look into the simplest composite laminates at thicknesses that better represented deployable boom structures. The second campaign tested three basic, thinner laminates, again in three different fiber orientations. All testing was monotonic loading to failure. The thickness of the laminates tested ranged from 0.166mm (campaign 2) to 0.45mm (campaign 1). The measured strains at failure for the unidirectional material were approximately 2.1% and 1.4% at the compression and tension sides, respectively, failing as fiber tensile fracture. Both of these values differ from what would be expected from considering much thicker coupons tested under pure compression and tension, that show a strain-to-failure of 1.0-1.1% and 1.6-1.7%, respectively. The significant differences in strain values obtained at the outer surfaces of the coupon is thought to be related to the shift in neutral axis that the specimen experiences during the large deformation bending test as a result of fiber material nonlinearities at higher strains. The vertical test nature of the CBT when compared to other test methods proves to be helpful for visually capturing with Digital Image Correlation the distinct behavior of the flexure on both the compressive and tensile sides. It was found that the thinner the laminate tested, the more confirmation of a nonlinear response of this classification of composites. The moment versus curvature curves were predominantly nonlinear resulting in a near linear bending stiffness versus curvature response. At these large strains, carbon fibers are highly nonlinear resulting in the laminate flexure modulus increasing by up to 5x. The theoretical bending stiffness values calculated using Classical Lamination Theory analysis are within small differences with respect to the experimentally measured values: errors of approximately 5-10% for both D11 and D22. The error between the finite element model computed strain response and the experimental values was on average around 22%, with 35% of the laminates and orientation having errors less than 7%. Comparison between CLT, FEA, and experimentation show that the Column Bend Test appears to be a promising candidate for characterization of large deformation bending behavior of thin-ply high strain composite laminates.

Characterization of Triaxial Braided Composite Material Properties for Impact Simulation

NASA Technical Reports Server (NTRS)

Roberts, Gary D.; Goldberg, Robert K.; Biniendak, Wieslaw K.; Arnold, William A.; Littell, Justin D.; Kohlman, Lee W.

2009-01-01

The reliability of impact simulations for aircraft components made with triaxial braided carbon fiber composites is currently limited by inadequate material property data and lack of validated material models for analysis. Improvements to standard quasi-static test methods are needed to account for the large unit cell size and localized damage within the unit cell. The deformation and damage of a triaxial braided composite material was examined using standard quasi-static in-plane tension, compression, and shear tests. Some modifications to standard test specimen geometries are suggested, and methods for measuring the local strain at the onset of failure within the braid unit cell are presented. Deformation and damage at higher strain rates is examined using ballistic impact tests on 61- by 61- by 3.2-mm (24- by 24- by 0.125-in.) composite panels. Digital image correlation techniques were used to examine full-field deformation and damage during both quasi-static and impact tests. An impact analysis method is presented that utilizes both local and global deformation and failure information from the quasi-static tests as input for impact simulations. Improvements that are needed in test and analysis methods for better predictive capability are examined.

Post-Crazing Stress Analysis of Glass-Epoxy Laminates.

DTIC Science & Technology

1979-05-01

element Stress concentrations Thick-shell element b. Identiflers/Open-Ended Terms Thick-plate element Glass-epoxy Laminates Composite materials Failure...number) / Glass-Epoxy Angle Plys Finite Elements’ Laminates Shear Testing Isoparametric.,lement Composite Materials Compression Testing Doubly-Curved...with light weight. This favorable strength- weight ratio makes the material attractive for some flight structures as well as other machines and

ON EDGE CHIPPING TESTING AND SOME PERSONAL PERSPECTIVES ON THE STATE OF THE ART OF MECHANICAL TESTING

PubMed Central

Quinn, G. D.

2014-01-01

Objective The edge chipping test is used to measure the fracture resistance of dental restoration ceramics and resin composites. This paper focuses on the progress of evaluating chipping resistance of these materials and also on the progress of standardization of this test method. This paper also makes observations about the state of the art of mechanical testing of ceramic and composite restorative materials in general. Interlaboratory comparative studies (“round robins”) are recommended. Methods An edge chipping machine was used to evaluate dozens of materials including porcelains, glass ceramics, aluminas, zirconias, filled resin-composites, new hybrid ceramic-resin composites, laminated composite ceramics, and even polymethyl methacrylate based denture materials. Force versus distance data were collected over a broad range with different indenters. Several chipping resistance parameters were quantified. Results Older restorative materials such as feldspathic porcelains and veneering materials had limited chipping resistance, but more modern ceramics and filled composites show significant improvements. A yttria-partially stabilized zirconia had the greatest resistance to chipping. Much of the early work on edge chipping resistance of brittle materials emphasized linear force versus distance trends obtained with relatively blunt Rockwell C indenters. More recently, trends for dental restorative materials with alternative sharper indenters have been nonlinear. A new phenomenological model with a simple quadratic function fits all data exceptionally well. It is loosely based on an energy balance between indenter work and fracture and deformation energies in the chipped material. Significance Although a direct comparison of our laboratory scale tests on idealized simple geometries to clinical outcomes has not yet been done, anecdotal evidence suggests the procedure does produce clinically relevant rankings and outcomes. Despite the variations in the trends and indenters, comparisons between materials can easily be made by chipping convenient block-shaped specimens with sharp conical 120°, Vickers, or Rockwell C indenters at a defined edge distance of 0.5 mm. Broad distance ranges are recommended for trend evaluation. This work has provided important information for standardization. PMID:25244927

Characterization and manufacture of braided composites for large commercial aircraft structures

NASA Technical Reports Server (NTRS)

Fedro, Mark J.; Willden, Kurtis

1992-01-01

Braided composite materials, one of the advanced material forms which is under investigation in Boeing's ATCAS program, have been recognized as a potential cost-effective material form for fuselage structural elements. Consequently, there is a strong need for more knowledge in the design, manufacture, test, and analysis of textile structural composites. The overall objective of this work is to advance braided composite technology towards applications to a large commercial transport fuselage. This paper summarizes the mechanics of materials and manufacturing demonstration results which have been obtained in order to acquire an understanding of how braided composites can be applied to a commercial fuselage. Textile composites consisting of 1D, 2D triaxial, and 3D braid patterns with thermoplastic and two RTM resin systems were investigated. The structural performance of braided composites was evaluated through an extensive mechanical test program. Analytical methods were also developed and applied to predict the following: internal fiber architectures, stiffnesses, fiber stresses, failure mechanisms, notch effects, and the entire history of failure of the braided composites specimens. The applicability of braided composites to a commercial transport fuselage was further assessed through a manufacturing demonstration. Three foot fuselage circumferential hoop frames were manufactured to demonstrate the feasibility of consistently producing high quality braided/RTM composite primary structures. The manufacturing issues (tooling requirements, processing requirements, and process/quality control) addressed during the demonstration are summarized. The manufacturing demonstration in conjunction with the mechanical test results and developed analytical methods increased the confidence in the ATCAS approach to the design, manufacture, test, and analysis of braided composites.

Evaluation of interlaminar shear of laminate by 3D digital holography

NASA Astrophysics Data System (ADS)

Mayssa, Karray; Christophe, Poilane; Mohamed, Gargouri; Pascal, Picart

2017-05-01

In this paper, we propose a three-color holographic interferometer devoted to the 3D displacement field analysis of a composite material. The method in applied to analyze cracks during a short beam shear test. The tested materials are a glass/epoxy composite, a flax/carbon/epoxy composite and a flax/epoxy composite. Such an evaluation provides a pertinent parameter to detect premature cracks in the structure, long before it becomes visible on the real time stress/strain curve, or with a classical microscope. Moreover, the mechanical proprieties of flax/carbon/epoxy composite and flax/epoxy composite are compared.

Investigation of woven composites as potential cryogenic tank materials

NASA Astrophysics Data System (ADS)

Islam, Md. S.; Melendez-Soto, E.; Castellanos, A. G.; Prabhakar, P.

2015-12-01

In this paper, carbon fiber and Kevlar® fiber woven composites were investigated as potential cryogenic tank materials for storing liquid fuel in spacecraft or rocket. Towards that end, both carbon and Kevlar® fiber composites were manufactured and tested with and without cryogenic exposure. The focus was on the investigation of the influence of initial cryogenic exposure on the degradation of the composite. Tensile, flexural and inter laminar shear strength (ILSS) tests were conducted, which indicate that Kevlar® and carbon textile composites are potential candidates for use under cryogenic exposure.

Composite Material Testing Data Reduction to Adjust for the Systematic 6-DOF Testing Machine Aberrations

Treesearch

Athanasios lliopoulos; John G. Michopoulos; John G. C. Hermanson

2012-01-01

This paper describes a data reduction methodology for eliminating the systematic aberrations introduced by the unwanted behavior of a multiaxial testing machine, into the massive amounts of experimental data collected from testing of composite material coupons. The machine in reference is a custom made 6-DoF system called NRL66.3 and developed at the NAval...

Pin bearing evaluation of LTM25 composite materials

NASA Technical Reports Server (NTRS)

Shah, C. H.; Postyn, A. S.

1996-01-01

This report summarizes pin bearing evaluations of LTM25 composite materials. Northrop Grumman Corporation conducted pin bearing testing and fabricate two panels from composite materials that cure at low temperatures. These materials are being incorporated into Unmanned Aerial Vehicles (UAVS) to reduce manufacturing costs since they allow the use of low-cost tooling and facilities. Two composite prepreg product forms were evaluated; MR50/LTM25 unidirectional tape, batch 2881vd and CFS003/LTM25 woven cloth, batch 2216. Northrop Grumman fabricated, machined, and tested specimens to determine the bearing strength in accordance with MIL-HDBK-17D, Volume 1, Section 7.2.4. Quasi-isotropic laminates from the two product forms were fabricated for these tests. In addition, 2 quasi-isotropic panels of dimensions 12 in. x 28 in. were fabricated (one each from the two product forms), inspected, and shipped to NASA Langley for further evaluation.

An investigation of the compressive strength of PRD-49-3/Epoxy composites

NASA Technical Reports Server (NTRS)

Kulkarni, S. V.; Rice, J. S.; Rosen, B. W.

1973-01-01

The development of unidirectional fiber composite materials is discussed. The mechanical and physical properties of the materials are described. Emphasis is placed in analyzing the compressive behavior of composite materials and developing methods for increasing compressive strength. The test program for evaluating the various procedures for improving compressive strength are reported.

Role of Microstructure on the Performance of UHTCs

NASA Technical Reports Server (NTRS)

Johnson, Sylvia M.; Gasch, Matthew J.; Lawson, John W.; Gusman, Michael I.; Stackpoole, Mairead

2010-01-01

We have investigated a number of methods to control microstructure. We have routes to form: a) in situ "composites" b) Very fine microstructures. Arcjet testing and other characterization of monolithic materials. Control oxidation through microstructure and composition. Beginning to incorporate these materials as matrices for composites. Modeling effort to facilitate material design and characterization.

Influence of different repair procedures on bond strength of adhesive filling materials to etched enamel in vitro.

PubMed

Hannig, Christian; Hahn, Petra; Thiele, Patrick-Philipp; Attin, Thomas

2003-01-01

Contamination of etched enamel with repair bond agents during repair of dental restorations may interfere with the bonding of composite to enamel. This study examined the bond strength of adhesive filling materials to etched bovine enamel after pre-treatment with the repair systems Monobond S, Silibond and Co-Jet. The materials Tetric Ceram, Dyract and Definite and their corresponding bonding agents (Syntac Single Comp, Prime & Bond NT, Etch and Prime) were tested in combination with the repair systems. One hundred and thirty-five enamel specimens were etched (37% phosphoric acid, 60 seconds) and equally distributed among three groups (A-C). In Group A, the repair materials were applied on etched enamel followed by applying the composite materials without using their respective bonding material. In Group B, the composite materials were placed on etched enamel after applying the repair materials and bonding agents. In control Group C, the composite materials and bonding agents were applied on etched enamel without using the repair systems. In each sub-group, every composite material was applied on 15 specimens. Samples were stored in artificial saliva for 14 days and thermocycled 1,000 times (5 degrees C/55 degrees C). The shear bond strength of the samples were then determined in a universal testing machine (ISO 10477). Applying Monobond or Silibond followed by the use of its respective bonding agents resulted in a bond strength that was not statistically different from the controls for all filling materials (Group C). The three composites that used Monobond and Silibond without applying the corresponding bonding agent resulted in bond strengths that were significantly lower than the controls. Utilizing the Co-Jet-System drastically reduced the bond strength of composites on etched enamel. Contamination of etched enamel with the repairing bonding agents Monobond and Silibond does not interfere with bond strength if the application of Monobond and Silibond is followed by using its corresponding bonding system of the composites tested.

Application of optical interferometric techniques for non-destructive evaluation of novel "green" composite materials

NASA Astrophysics Data System (ADS)

Pagliarulo, Vito; Russo, Pietro; Bianco, Vittorio; Ferraro, Pietro; Simeoli, Giorgio; Cimino, Francesca; Ruggiero, Berardo

2018-04-01

Nowadays the use of advanced composite materials in aeronautics, both civil and military, in automotive and in sport applications, citing some, is well established. The characteristics of composite materials in terms of weight, fatigue resistance and corrosion resistance make them competitive with respect to conventional ones. On the other side, the fabrication process of the most employed composites reinforced by carbon fibers or glass fibers, needs of complex steps that not always are environmental complaisant. Moreover, such fibers are not themselves "green". For these reasons, in the last decades, the use of natural reinforcing fibers has gained an increasing attention allowing the development of new materials with the same advantages of composite systems but respecting the environment. Furthermore, such materials for their structural complexity are not always compatible with the use of standard non-destructive evaluation as the ultrasounds methods. In this work the efficiency of the employment of optical interferometric techniques as nondestructive evaluation methods in full field modality is proved on novel "green" composite materials. In particular, Electronic Speckle Pattern Interferometry has been tested on different kinds of specimens after flexural tests.

Composite materials flown on the Long Duration Exposure Facility

NASA Technical Reports Server (NTRS)

George, Pete E.; Dursch, Harry W.; Pippin, H. Gary

1995-01-01

Organic composite test specimens were flown on several LDEF experiments. Both bare and coated composites were flown. Atomic oxygen eroded bare composite material, with the resins being recessed at a greater rate than the fibers. Selected coating techniques protected the composite substrate in each case. Tensile and optical properties are reported for numerous specimens. Fiberglass and metal matrix composites were also flown.

Fatigue behavior and life prediction of a SiC/Ti-24Al-11Nb composite under isothermal conditions. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Bartolotta, Paul A.

1991-01-01

Metal Matrix Composites (MMC) and Intermetallic Matrix Composites (IMC) were identified as potential material candidates for advanced aerospace applications. They are especially attractive for high temperature applications which require a low density material that maintains its structural integrity at elevated temperatures. High temperature fatigue resistance plays an important role in determining the structural integrity of the material. This study attempts to examine the relevance of test techniques, failure criterion, and life prediction as they pertain to an IMC material, specifically, unidirectional SiC fiber reinforced titanium aluminide. A series of strain and load controlled fatigue tests were conducted on unidirectional SiC/Ti-24Al-11Nb composite at 425 and 815 C. Several damage mechanism regimes were identified by using a strain-based representation of the data, Talreja's fatigue life diagram concept. Results of these tests were then used to address issues of test control modes, definition of failure, and testing techniques. Finally, a strain-based life prediction method was proposed for an IMC under tensile cyclic loadings at elevated temperatures.

Development of an Input Suite for an Orthotropic Composite Material Model

NASA Technical Reports Server (NTRS)

Hoffarth, Canio; Shyamsunder, Loukham; Khaled, Bilal; Rajan, Subramaniam; Goldberg, Robert K.; Carney, Kelly S.; Dubois, Paul; Blankenhorn, Gunther

2017-01-01

An orthotropic three-dimensional material model suitable for use in modeling impact tests has been developed that has three major components elastic and inelastic deformations, damage and failure. The material model has been implemented as MAT213 into a special version of LS-DYNA and uses tabulated data obtained from experiments. The prominent features of the constitutive model are illustrated using a widely-used aerospace composite the T800S3900-2B[P2352W-19] BMS8-276 Rev-H-Unitape fiber resin unidirectional composite. The input for the deformation model consists of experimental data from 12 distinct experiments at a known temperature and strain rate: tension and compression along all three principal directions, shear in all three principal planes, and off axis tension or compression tests in all three principal planes, along with other material constants. There are additional input associated with the damage and failure models. The steps in using this model are illustrated composite characterization tests, verification tests and a validation test. The results show that the developed and implemented model is stable and yields acceptably accurate results.

Experimental and Analytical Characterization of the Macromechanical Response for Triaxial Braided Composite Materials

NASA Technical Reports Server (NTRS)

Littell, Justin D.

2013-01-01

Increasingly, carbon composite structures are being used in aerospace applications. Their highstrength, high-stiffness, and low-weight properties make them good candidates for replacing many aerospace structures currently made of aluminum or steel. Recently, many of the aircraft engine manufacturers have developed new commercial jet engines that will use composite fan cases. Instead of using traditional composite layup techniques, these new fan cases will use a triaxially braided pattern, which improves case performance. The impact characteristics of composite materials for jet engine fan case applications have been an important research topic because Federal regulations require that an engine case be able to contain a blade and blade fragments during an engine blade-out event. Once the impact characteristics of these triaxial braided materials become known, computer models can be developed to simulate a jet engine blade-out event, thus reducing cost and time in the development of these composite jet engine cases. The two main problems that have arisen in this area of research are that the properties for these materials have not been fully determined and computationally efficient computer models, which incorporate much of the microscale deformation and failure mechanisms, are not available. The research reported herein addresses some of the deficiencies present in previous research regarding these triaxial braided composite materials. The current research develops new techniques to accurately quantify the material properties of the triaxial braided composite materials. New test methods are developed for the polymer resin composite constituent and representative composite coupons. These methods expand previous research by using novel specimen designs along with using a noncontact measuring system that is also capable of identifying and quantifying many of the microscale failure mechanisms present in the materials. Finally, using the data gathered, a new hybrid micromacromechanical computer model is created to simulate the behavior of these composite material systems under static and ballistic impact loading using the test data acquired. The model also quantifies the way in which the fiber/matrix interface affects material response under static and impact loading. The results show that the test methods are capable of accurately quantifying the polymer resin under a variety of strain rates and temperature for three loading conditions. The resin strength and stiffness data show a clear rate and temperature dependence. The data also show the hydrostatic stress effects and hysteresis, all of which can be used by researchers developing composite constitutive models for the resins. The results for the composite data reveal noticeable differences in strength, failure strain, and stiffness in the different material systems presented. The investigations into the microscale failure mechanisms provide information about the nature of the different material system behaviors. Finally, the developed computer model predicts composite static strength and stiffness to within 10 percent of the gathered test data and also agrees with composite impact data, where available.

Tissue Anisotropy Modeling Using Soft Composite Materials.

PubMed

Chanda, Arnab; Callaway, Christian

2018-01-01

Soft tissues in general exhibit anisotropic mechanical behavior, which varies in three dimensions based on the location of the tissue in the body. In the past, there have been few attempts to numerically model tissue anisotropy using composite-based formulations (involving fibers embedded within a matrix material). However, so far, tissue anisotropy has not been modeled experimentally. In the current work, novel elastomer-based soft composite materials were developed in the form of experimental test coupons, to model the macroscopic anisotropy in tissue mechanical properties. A soft elastomer matrix was fabricated, and fibers made of a stiffer elastomer material were embedded within the matrix material to generate the test coupons. The coupons were tested on a mechanical testing machine, and the resulting stress-versus-stretch responses were studied. The fiber volume fraction (FVF), fiber spacing, and orientations were varied to estimate the changes in the mechanical responses. The mechanical behavior of the soft composites was characterized using hyperelastic material models such as Mooney-Rivlin's, Humphrey's, and Veronda-Westmann's model and also compared with the anisotropic mechanical behavior of the human skin, pelvic tissues, and brain tissues. This work lays the foundation for the experimental modelling of tissue anisotropy, which combined with microscopic studies on tissues can lead to refinements in the simulation of localized fiber distribution and orientations, and enable the development of biofidelic anisotropic tissue phantom materials for various tissue engineering and testing applications.

Tissue Anisotropy Modeling Using Soft Composite Materials

PubMed Central

Callaway, Christian

2018-01-01

Soft tissues in general exhibit anisotropic mechanical behavior, which varies in three dimensions based on the location of the tissue in the body. In the past, there have been few attempts to numerically model tissue anisotropy using composite-based formulations (involving fibers embedded within a matrix material). However, so far, tissue anisotropy has not been modeled experimentally. In the current work, novel elastomer-based soft composite materials were developed in the form of experimental test coupons, to model the macroscopic anisotropy in tissue mechanical properties. A soft elastomer matrix was fabricated, and fibers made of a stiffer elastomer material were embedded within the matrix material to generate the test coupons. The coupons were tested on a mechanical testing machine, and the resulting stress-versus-stretch responses were studied. The fiber volume fraction (FVF), fiber spacing, and orientations were varied to estimate the changes in the mechanical responses. The mechanical behavior of the soft composites was characterized using hyperelastic material models such as Mooney-Rivlin's, Humphrey's, and Veronda-Westmann's model and also compared with the anisotropic mechanical behavior of the human skin, pelvic tissues, and brain tissues. This work lays the foundation for the experimental modelling of tissue anisotropy, which combined with microscopic studies on tissues can lead to refinements in the simulation of localized fiber distribution and orientations, and enable the development of biofidelic anisotropic tissue phantom materials for various tissue engineering and testing applications. PMID:29853996

Application of composite materials to impact-insensitive munitions

NASA Technical Reports Server (NTRS)

Neradka, Vincent F.; Chang, Yale; Grady, Joseph E.; Trowbridge, Daniel A.

1992-01-01

An approach is outlined for developing bullet-impact-insensitive munitions based on composite materials that provide rapid venting of the rocket-motor case. Impact experiments are conducted with test specimens of hybrid laminates of graphite/epoxy and epoxy reinforcing with woven glass fibers. The dynamic strain response and initial impact force are measured with strain gauges, and perforation damage is examined in the plates. The results show that impact damage can be designed by means of parametric variations of the fiber, matrix, and ply orientations. It is suggested that rocket-motor cases can be designed with composite materials to provide rapid venting during the failure mode. The experimental ballistic testing performed provides data that can be used comparatively with analytical data on composite materials.

Evaluation of Material Models within LS-DYNA(Registered TradeMark) for a Kevlar/Epoxy Composite Honeycomb

NASA Technical Reports Server (NTRS)

Polanco, Michael A.; Kellas, Sotiris; Jackson, Karen

2009-01-01

The performance of material models to simulate a novel composite honeycomb Deployable Energy Absorber (DEA) was evaluated using the nonlinear explicit dynamic finite element code LS-DYNA(Registered TradeMark). Prototypes of the DEA concept were manufactured using a Kevlar/Epoxy composite material in which the fibers are oriented at +/-45 degrees with respect to the loading axis. The development of the DEA has included laboratory tests at subcomponent and component levels such as three-point bend testing of single hexagonal cells, dynamic crush testing of single multi-cell components, and impact testing of a full-scale fuselage section fitted with a system of DEA components onto multi-terrain environments. Due to the thin nature of the cell walls, the DEA was modeled using shell elements. In an attempt to simulate the dynamic response of the DEA, it was first represented using *MAT_LAMINATED_COMPOSITE_FABRIC, or *MAT_58, in LS-DYNA. Values for each parameter within the material model were generated such that an in-plane isotropic configuration for the DEA material was assumed. Analytical predictions showed that the load-deflection behavior of a single-cell during three-point bending was within the range of test data, but predicted the DEA crush response to be very stiff. In addition, a *MAT_PIECEWISE_LINEAR_PLASTICITY, or *MAT_24, material model in LS-DYNA was developed, which represented the Kevlar/Epoxy composite as an isotropic elastic-plastic material with input from +/-45 degrees tensile coupon data. The predicted crush response matched that of the test and localized folding patterns of the DEA were captured under compression, but the model failed to predict the single-cell three-point bending response.

Shear properties of pultruded fiber reinforced polymer composite materials

NASA Astrophysics Data System (ADS)

Seo, J. H.; Kim, S. H.; Ok, D. M.; An, D. J.; Yoon, S. J.

2018-06-01

This paper focuses on the mechanical properties of PFRP composite materials. Especially, relationship between shear property and the other mechanical properties of PFRP composite materials is investigated through comparison between experimental and theoretical results. The shear property of PFRP composite specimen is calculated from the theoretical equations which were suggested in previous studies. In addition, comparison between the shear property determined by the tensile test and the shear property calculated from theoretical equations is conducted and discussed. It was found that the theoretically predicted shear modulus of elasticity considering contiguity is close to the shear modulus of elasticity obtained by the 45° off-axis tensile test.

Test Report: Direct and Indirect Lightning Effects on Composite Materials

NASA Technical Reports Server (NTRS)

Evans, R. W.

1997-01-01

Lightning tests were performed on composite materials as a part of an investigation of electromagnetic effects on the materials. Samples were subjected to direct and remote simulated lightning strikes. Samples included various thicknesses of graphite filament reinforced plastic (GFRP), material enhanced by expanded aluminum foil layers, and material with an aluminum honeycomb core. Shielding properties of the material and damage to the sample surfaces and joints were investigated. Adding expanded aluminum foil layers and increasing the thickness of GFRP improves the shielding effectiveness against lightning induced fields and the ability to withstand lightning strikes. A report describing the lightning strike tests performed by the U.S. Army Redstone Technical Test Center, Redstone Arsenal, AL, STERT-TE-E-EM, is included as an appendix.

Investigation on Flexure Test of Composite Beam of Repair Materials and Substrate Concrete for Durable Repair

NASA Astrophysics Data System (ADS)

Pattnaik, Rashmi R.; Rangaraju, Prasada Rao

2014-12-01

An experimental study was conducted on composite beam of repair materials and substrate concrete to investigate the failures of concrete repair due to differences in strength of repair materials and substrate concrete. In this investigation the flexural strength, load-deflection curves and failure patterns of the composite beam specimens are studied for the durability of the concrete repair. Flexure test was conducted to simulate tensile stress in the concrete repair material. Compressive strength and split tensile strength of the repair materials and substrate concrete are investigated to aid in the analysis of the concrete repair. It was observed that the repair materials of higher compressive strength than the substrate concrete are causing an incompatible failure in the concrete repair.

Fabrication and evaluation of low fiber content alumina fiber/aluminum composites

NASA Technical Reports Server (NTRS)

Hack, J. E.; Strempek, G. C.

1980-01-01

The mechanical fabrication of low volume percent fiber, polycrystalline alumina fiber reinforced aluminum composites was accomplished. Wire preform material was prepared by liquid-metal infiltration of alumina fiber bundles. The wires were subsequently encapsulated with aluminum foil and fabricated into bulk composite material by hot-drawing. Extensive mechanical, thermal and chemical testing was conducted on preform and bulk material to develop a process and material data base. In addition, a preliminary investigation of mechanical forming of bulk alumina fiber reinforced aluminum composite material was conducted.

Mode II Interlaminar Fracture Toughness and Fatigue Characterization of a Graphite Epoxy Composite Material

NASA Technical Reports Server (NTRS)

O'Brien, T. Kevin; Johnston, William M.; Toland, Gregory J.

2010-01-01

Mode II interlaminar fracture toughness and delamination onset and growth characterization data were generated for IM7/8552 graphite epoxy composite materials from two suppliers for use in fracture mechanics analyses. Both the fracture toughness testing and the fatigue testing were conducted using the End-notched Flexure (ENF) test. The ENF test for mode II fracture toughness is currently under review by ASTM as a potential standard test method. This current draft ASTM protocol was used as a guide to conduct the tests on the IM7/8552 material. This report summarizes the test approach, methods, procedures and results of this characterization effort.

Determination of Interlaminar Toughness of IM7/977-2 Composites at Temperature Extremes and Different Thicknesses

NASA Technical Reports Server (NTRS)

Johnson, W. S.; Pavlick, M. M.; Oliver, M. S.

2005-01-01

Composite materials are being used in the aerospace industry as a means of reducing vehicle weight. In particular, polymer matrix composites (PMC) are good candidates due to their high strength-to-weight and high stiffness-to-weight ratios. Future reusable space launch vehicles and space exploration structures will need advanced light weight composites in order to minimize vehicle weight while demonstrating robustness and durability, guaranteeing high factors of safety. In particular, the implementation of composite cryogenic propellant fuel tanks (cryotanks) for future reusable launch vehicles (RLVs) could greatly reduce the vehicle's weight versus identically sized cryotanks constructed of metallic materials. One candidate composite material for future cryotank designs is IM7/977-2, which is a graphite/epoxy system. A successful candidate must demonstrate reasonable structural properties over a wide range of temperatures. Since the matrix material is normally the weak link in the composite, tests that emphasize matrix-dominated behavior need to be conducted. Therefore, the objective of this work is to determine the mode I interlaminar fracture toughness of "unidirectional" 8-ply and 16-ply IM7/977-2 through experimental testing. Tests were performed at -196 degrees Celsius (-320 degrees Fahrenheit), 22 degrees Celsius (72 degrees Fahrenheit), 93 degrees Celsius (200 degrees Fahrenheit) and 160 degrees C (320 degrees Fahrenheit). Low temperature testing was completed while the specimen was submerged in a liquid nitrogen bath. High temperature testing was completed in a temperature-controlled oven.

The Design, Fabrication, and Testing of Composite Heat Exchange Coupons

NASA Technical Reports Server (NTRS)

Quade, Derek J.; Meador, Michael A.; Shin, Euy-Sik; Johnston, James C.; Kuczmarski, Maria A.

2011-01-01

Several heat exchanger (HX) test panels were designed, fabricated and tested at the NASA Glenn Research Center to explore the fabrication and performance of several designs for composite heat exchangers. The development of these light weight, high efficiency air-liquid test panels was attempted using polymer composites and carbon foam materials. The fundamental goal of this effort was to demonstrate the feasibility of the composite HX for various space exploration and thermal management applications including Orion CEV and Altair. The specific objectives of this work were to select optimum materials, designs, and to optimize fabrication procedures. After fabrication, the individual design concept prototypes were tested to determine their thermal performance and to guide the future development of full-size engineering development units (EDU). The overall test results suggested that the panel bonded with pre-cured composite laminates to KFOAM Grade L1 scored above the other designs in terms of ease of manufacture and performance.

Composite structural materials

NASA Technical Reports Server (NTRS)

Loewy, R.; Wiberley, S. E.

1986-01-01

Overall emphasis is on basic long-term research in the following categories: constituent materials, composite materials, generic structural elements, processing science technology; and maintaining long-term structural integrity. Research in basic composition, characteristics, and processing science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to present and future problems. Detailed descriptions of the progress achieved in the various component parts of this comprehensive program are presented.

Application of the inverse analysis for determining the material properties of the woven fabrics for macroscopic approach

NASA Astrophysics Data System (ADS)

Oleksik, Mihaela; Oleksik, Valentin

2013-05-01

The current paper intends to realise a fast method for determining the material characteristics in the case of composite materials used in the airbags manufacturing. For determining the material data needed for other complex numerical simulations at macroscopic level there was used the inverse analysis method. In fact, there were carried out tensile tests for the composite material extracted along two directions - the direction of the weft and the direction of the warp and afterwards there were realised numerical simulations (using the Ls-Dyna software). A second stage consisted in the numerical simulation through the finite element method and the experimental testing for the Bias test. The material characteristics of the composite fabric material were then obtained by applying a multicriterial analysis using the Ls-Opt software, for which there was imposed a decrease of the mismatch between the force-displacement curves obtained numerically and experimentally, respectively, for both directions (weft and warp) as well as the decrease of the mismatch between the strain - extension curves for two points at the Bias test.

Contributions on the Study of the Compressive Strength of the Light-Cured Composite Resins

PubMed Central

Manolea, H.; Degeratu, Sonia; Deva, V.; Coles, Evantia; Draghici, Emma

2009-01-01

The mechanical properties of the light-cured composite resins are related to the material composition, but also vary according to the light-source characteristics used for polymerization. In this study we followed the compressive strength variation for a light-cured composite resin according to the time of exposure to the curing light. With that end in view,18 test pieces were made from a light-cured hybrid composite material (Filtek Z250). The test pieces where then submitted to a compressive force by a mechanical properties universal testing machine. Our results didn’t show an increase of the compressive strength according to the light-curing time increasing, than only in the light-curing time limit indicated by the manufacturer. A longer light-curing time may induce a shrinkage polymerization growth with the formation of internal tensions inside the material. The composite materials light-curing in short layers as long as there is indicated by the manufacturer seems to be a safer method to make the best from a resin qualities, then an exaggerated increase of the light-curing time. The light-curing is indicated to be done in the direction of the compressive forces. To confirm this supposition other mechanical tests are also necessary PMID:24778814

TOXICITY TESTING OF RESTORATIVE DENTAL MATERIALS USING BRINE SHRIMP LARVAE (ARTEMIA SALINA)

PubMed Central

Milhem, Manar M.; Al-Hiyasat, Ahmad S.; Darmani, Homa

2008-01-01

This study investigated the effect of extracts of different composites, glass ionomer cement (GIC)s and compomers on the viability of brine shrimp larvae. Ethanolic extracts of four dental composites (Z-100; Solitaire 2; Filtek P60 and Synergy), a conventional GIC (Ketac-Fil), a resin-modified glass ionomer cement (Vitremer), two compomers (F2000; Dyract AP), and a flowable compomer (Dyract Flow) were prepared from each material. Following evaporation of the ethanol, the extracts were resuspended in distilled water, which was then used to test the effects on the viability of brine shrimp larvae. For the composites, the extract of Synergy was the least toxic (88% viability) followed by the extracts of Solitaire 2, Z100 and P60 (75%, 67.5% and 50% viability, respectively). One-way ANOVA revealed highly significant differences between the resin composite materials (p<0.001). Follow-up comparison between the composite groups by Tukey's pairwise multiple-comparison test (α =0.05) showed that the extract of Synergy was significantly less toxic than the extracts of all the other materials except that of Solitaire 2. The compomers showed 100% lethality, while the percentage of viable larvae for the extracts of Ketac-Fil, and Vitremer were 32.3%, and 37.0%, respectively. One-way ANOVA revealed highly significant differences between the groups of materials (p<0.001). Follow-up comparison between the groups by Tukey's test (α = 0.05) showed that the toxic effect of the extracts of the compomers were significantly greater than that of Ketac-Fil, and Vitremer. The differences in the toxic effects of Vitremer and Ketac-Fil were not statistically significant. In conclusion, the toxicity of composite materials varied according to their chemical composition. Compomers were the most lethal materials to brine shrimp larvae followed by GICs and then composites. PMID:19089264

Evaluation of Multi-Functional Materials for Deep Space Radiation Shielding

NASA Technical Reports Server (NTRS)

Rojdev, Kristina; Atwell, William; Wilkins, Richard; Gersey, Brad; Badavi, Francis F.

2009-01-01

Small scale trade study of materials for radiation shielding: a) High-hydrogen polymers; b) Z-graded materials; c) Fiber-reinforced polymer composites. Discussed multi-functionality of fiber-reinforced polymer composites. Preliminary results of ground testing data.

Comparison of mechanical properties of multi-walled carbon nanotube and graphene nanosheet/polyethylene oxide composites plasticized with lithium triflate

NASA Astrophysics Data System (ADS)

Jurkane, A.; Gaidukov, S.

2017-10-01

A strong engineering interest in nanostructured conducting polymers and its composite materials have been widely used to build various sensor devices, electronic interconnect devices, fuel cells and batteries. Preparation of polymeric nano-composites with finely controlled structure, especially, at nano-scale, is still one of the most perspective modification ways of the properties of polymeric composites. Multi-walled carbon nanotube (MWCNT)/polyethylene oxide (PEO) and graphene nanosheets (GR)/PEO composites and composite of MWCNT/GR/PEO were prepared by solution casting and hot-pressing method. Composites were plasticized by 5% of Lithium triflate (LiTrifl), which play role of additional ion source in conducting polymer composite. Mechanical tensile tests were performed to evaluate nanoparticles influence on the mechanical strength of the conductive polymer composite materials. Difference of tensile tests of prepared composition can be seen from tensile tests data curves. The results of tensile tests indicated that the nanoparticles can provide PEO/5%LiTrifl composite with stiffening effects at rather low filler content (at least 0.05% by volume).

Material characterization of active fiber composites for integral twist-actuated rotor blade application

NASA Astrophysics Data System (ADS)

Wickramasinghe, Viresh K.; Hagood, Nesbitt W.

2004-10-01

The primary objective of this work was to perform material characterization of the active fiber composite (AFC) actuator system for the Boeing active material rotor (AMR) blade application. The purpose of the AMR was to demonstrate active vibration control in helicopters through integral twist-actuation of the blade. The AFCs were a new structural actuator system consisting of piezoceramic fibers embedded in an epoxy matrix and sandwiched between interdigitated electrodes to enhance actuation performance. These conformable actuators were integrated directly into the blade spar laminate as active plies within the composite structure to perform structural control. Therefore, extensive electromechanical material characterization was required to evaluate AFCs both as actuators and as structural components of the blade. The characterization tests designed to extract important electromechanical properties under simulated blade operating conditions included nominal actuation tests, stress-strain tests and actuation under tensile load tests. This paper presents the test results as well as the comprehensive testing procedure developed to evaluate the relevant properties of the AFCs for structural application. The material characterization tests provided an invaluable insight into the behavior of the AFCs under various electromechanical conditions. The results from this comprehensive material characterization of the AFC actuator system supported the design and operation of the AMR blades scheduled for wind tunnel tests.

Mechanical fatigue degradation of ceramics versus resin composites for dental restorations.

PubMed

Belli, Renan; Geinzer, Eva; Muschweck, Anna; Petschelt, Anselm; Lohbauer, Ulrich

2014-04-01

For posterior partial restorations an overlap of indication exists where either ceramic or resin-based composite materials can be successfully applied. The aim of this study was to compare the fatigue resistance of modern dental ceramic materials versus dental resin composites in order to address such conflicts. Bar specimens of five ceramic materials and resin composites were produced according to ISO 4049 and stored for 14 days in distilled water at 37°C. The following ceramic materials were selected for testing: a high-strength zirconium dioxide (e.max ZirCAD, Ivoclar), a machinable lithium disilicate (e.max CAD, Ivoclar), a pressable lithium disilicate ceramic (e-max Press, Ivoclar), a fluorapatite-based glass-ceramic (e.max Ceram, Ivoclar), and a machinable color-graded feldspathic porcelain (Trilux Forte, Vita). The composite materials selected were: an indirect machinable composite (Lava Ultimate, 3M ESPE) and four direct composites with varying filler nature (Clearfil Majesty Posterior, Kuraray; GrandioSO, Voco; Tetric EvoCeram, Ivoclar-Vivadent; and CeramX Duo, Dentsply). Fifteen specimens were tested in water for initial strength (σin) in 4-point bending. Using the same test set-up, the residual flexural fatigue strength (σff) was determined using the staircase approach after 10(4) cycles at 0.5 Hz (n=25). Weibull parameters σ0 and m were calculated for the σin specimens, whereas the σff and strength loss in percentage were obtained from the fatigue experiment. The zirconium oxide ceramic showed the highest σin and σff (768 and 440 MPa, respectively). Although both lithium disilicate ceramics were similar in the static test, the pressable version showed a significantly higher fatigue resistance after cyclic loading. Both the fluorapatite-based and the feldspathic porcelain showed equivalent initial and cyclic fatigue properties. From the composites, the highest filled direct material Clearfil Majesty Posterior showed superior fatigue performance. From all materials, e.max Press and Clearfil Majesty Posterior showed the lowest strength loss (29.6% and 32%, respectively), whereas the other materials lost between 41% and 62% of their flexural strength after cyclic loading. Dental ceramics and resin composite materials show equivalent fatigue strength degradation at loads around 0.5σin values. Apart from the zirconium oxide and the lithium disilicate ceramics, resin composites generally showed better σff after 10,000 cycles than the fluorapatite glass-ceramic and the feldspathic porcelain. Resin composite restorations may be used as an equivalent alternative to glass-rich-ceramic inlays regarding mechanical performance. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Processing and Characterization of Basalt Fiber Reinforced Ceramic Composites for High Temperature Applications Using Polymer Precursors

NASA Technical Reports Server (NTRS)

Cox, Sarah; Lui, Donovan; Gou, Jihua

2014-01-01

The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Ceramics can take much higher temperatures, but they are difficult to produce and form in bulk volumes. Polymer Derived Ceramics (PDCs) begin as a polymer matrix, allowing a shape to be formed, to be cured, and be pyrolized in order to obtain a ceramic with the associated thermal and mechanical properties. The two PDCs used in this development are polysiloxane and polycarbosilane. Polysiloxanes contain a silicon oxycarbide backbone when pyrolized up to 1000degC. Polycarbosilane, an organosilicon polymer, contain a silicon-carbon backbone; around 1200degC, -SiC begins to crystallize. The use of basalt in structural and high temperature applications has been under development for over 50 years, yet there has been little published research on the incorporation of basalt fibers as a reinforcement in composites. Basalt is a naturally occurring material found in volcanic rock. Continuous basalt fiber reinforced PDCs have been fabricated and tested for the applicability of this composite system as a high temperature structural composite material. Testing for this included thermal and mechanical testing per ASTM standard tests.

Granulated activated carbon modified with hydrophobic silica aerogel-potential composite materials for the removal of uranium from aqueous solutions.

PubMed

Coleman, Sabre J; Coronado, Paul R; Maxwell, Robert S; Reynolds, John G

2003-05-15

Aqueous solutions of 100 parts per billion (ppb) uranium at pH 7 were treated with granulated activated carbon (GAC) that had been modified with various formulations of hydrophobic aerogels. The composite materials were found to be superior in removing uranium from a stock solution compared to GAC alone evaluated by a modified ASTM D 3860-98 method for batch testing. The testing results were evaluated using a Freundlich adsorption model. The best performing material has parameters of n = 287 and Kf = 1169 compared to n = 1.00, and Kf = 20 for GAC alone. The composite materials were formed by mixing (CH3O)4Si with the hydrophobic sol-gel precursor, (CH3O)3SiCH2CH2CF3 and with specified modifiers, such as H3PO4, Ca(NO3)2, and (C2H5O)3SiCH2CH2P(O)(OC2H5)2, elation catalysts, and GAC in a supercritical reactor system. After gelation, supercritical extraction, and sieving, the composites were tested. Characterization by FTIR and 31P NMR indicate the formation of phosphate in the case of the H3PO4 and Ca(NO3)2 composites and phosphonic acid related compounds in the phosphonate composite. These composite materials have potential application in the clean up of groundwater at DOE and other facilities.

Comparative in vitro study for orthodontic adhesives relatively to sorption and solubility

NASA Astrophysics Data System (ADS)

Muntean, A.; Mesaros, A.; Festila, D.; Moldovan, M.; Boboia, S.; Mesaros, M.

2015-12-01

Water sorption and solubility correspond to undesirable physical characteristics because it may cause micro leakage and dissolution for composite materials used for orthodontic attachment bonding. The aim of this study was to evaluate the performance of four composite materials employed in orthodontic as adhesives, relatively to water and 50% alcoholic solution, by means of in vitro tests of sorption and solubility. We used an experimental composite sealer SO® (ICCRR Cluj Napoca) and 3 commercial products already on the market: Blugloo® (Ormco), Opal Bond MV® (Ultradent) and Bond It® (DB orthodontics). Data were recorded and specific statistic tests were performed, revealing significant differences for all materials relatively to tested solutions. The materials expressed an adequate performance in terms of sorption and solubility, offering various alternatives for orthodontists.

Study on the infrared radiation performance of Tourmaline composite and its effect on the diesel characteristic

NASA Astrophysics Data System (ADS)

Liao, Jian Bin; Yu, Hong Liang; Sun, Di; Ma, Fong Yuan

2017-09-01

The black tourmaline, magnesium tourmaline, and spinel were ground into powder, and the infrared radiation material was prepared by adding the ceramic powder, clay and the other material into the tourmaline powder according to a certain proportion. The infrared radiation property was tested and analyzed, the diesel was infrared radiation activated by the composite material, and the physicochemical property of fuel oil was analyzed pre-test and post-test. The result shows that the infrared absorption spectrum of the black tourmaline of different particle size is stable. After the diesel oil was infrared radiation activated by tourmaline composite materials, the physicochemical property of diesel oil was changed, the activation energy decreased, the viscosity and surface tension of fuel oil were reduced.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Alexander; Jernigan, Dann A.; Dodd, Amanda B.

New aircraft are being designed with increasing quantities of composite materials used in their construction. Different from the more traditional metals, composites have a higher propensity to burn. This presents a challenge to transportation safety analyses, as the aircraft structure now represents an additional fuel source involved in the fire scenario. Most of the historical fire testing of composite materials is aime d at studying kinetics, flammability or yield strength under fire conditions. Most of this testing is small - scale. Heterogeneous reactions are often length - scale dependent, and this is thought to be particularly true for composites whichmore » exhibit signific ant microscopic dynamics that can affect macro - scale behavior. We have designed a series of tests to evaluate composite materials under various structural loading conditions with a consistent thermal condition. We have measured mass - loss , heat flux, and temperature throughout the experiments. Several types of panels have been tested, including simple composite panels, and sandwich panels. The main objective of the testing was to understand the importance of the structural loading on a composite to its b ehavior in response to fire - like conditions. During flaming combustion at early times, there are some features of the panel decomposition that are unique to the type of loading imposed on the panels. At load levels tested, fiber reaction rates at later t imes appear to be independent of the initial structural loading.« less

Wear rate optimization of Al/SiCnp/e-glass fibre hybrid metal matrix composites using Taguchi method and genetic algorithm and development of wear model using artificial neural networks

NASA Astrophysics Data System (ADS)

Bongale, Arunkumar M.; Kumar, Satish; Sachit, T. S.; Jadhav, Priya

2018-03-01

Studies on wear properties of Aluminium based hybrid nano composite materials, processed through powder metallurgy technique, are reported in the present study. Silicon Carbide nano particles and E-glass fibre are reinforced in pure aluminium matrix to fabricate hybrid nano composite material samples. Pin-on-Disc wear testing equipment is used to evaluate dry sliding wear properties of the composite samples. The tests were conducted following the Taguchi’s Design of Experiments method. Signal-to-Noise ratio analysis and Analysis of Variance are carried out on the test data to find out the influence of test parameters on the wear rate. Scanning Electron Microscopic analysis and Energy Dispersive x-ray analysis are conducted on the worn surfaces to find out the wear mechanisms responsible for wear of the composites. Multiple linear regression analysis and Genetic Algorithm techniques are employed for optimization of wear test parameters to yield minimum wear of the composite samples. Finally, a wear model is built by the application of Artificial Neural Networks to predict the wear rate of the composite material, under different testing conditions. The predicted values of wear rate are found to be very close to the experimental values with a deviation in the range of 0.15% to 8.09%.

Composite material making from empty fruit bunches of palm oil (EFB) and Ijuk (Arengapinnata) using plastic bottle waste as adhesives

NASA Astrophysics Data System (ADS)

Rihayat, T.; Salim, S.; Audina, N.; Khan, N. S. P.; Zaimahwati; Sami, M.; Yunus, M.; Salisah, Z.; Alam, P. N.; Saifuddin; Yusuf, I.

2018-03-01

Reviewed from the current technological required a new methods to capable offering a high profit value without overriding the quality. The development of composite technology is now beginning to shift from traditional composite materials based petroleum to natural fibers composite. In the present study, aim to made specimens using natural fibers in form of EFB as a composite reinforcedment with Polyethylene Terephtalate (PET) derived from Plastic bottles waste as matrix with mixed composition parameters and time-tolerance in the mixing process to build a biocomposite material. The characterization of mechanical properties includes tensile test (ASTM D638-01) and bending test (ASTM D790-02) followed by thermal analysis using Thermogravimetric Analysis (TGA), and morphological analysis using scanning electron microscope (SEM). The analysis effect of EFB, Ijuk and PET mixtures on the composite matrix is very influential with mechanical properties characterization, including tensile test and bending strength. The results demonstrated that from the sample named : 50 : 25: 25, hybrid composites showed improved properties such as tensile strength of 167 MPa while the 90:05:05 based composites exhibited tensile strength values of 30 MPa, respectively. In term the flexural test the best result of composition on the properties with 10 minutes duration time its load value 7,5 Mpa for 80:10:10.

Development of Lightweight Material Composites to Insulate Cryogenic Tanks for 30-Day Storage in Outer Space

NASA Technical Reports Server (NTRS)

Krause, D. R.

1972-01-01

A conceptual design was developed for an MLI system which will meet the design constraints of an ILRV used for 7- to 30-day missions. The ten tasks are briefly described: (1) material survey and procurement, material property tests, and selection of composites to be considered; (2) definition of environmental parameters and tooling requirements, and thermal and structural design verification test definition; (3) definition of tanks and associated hardware to be used, and definition of MLI concepts to be considered; (4) thermal analyses, including purge, evacuation, and reentry repressurization analyses; (5) structural analyses (6) thermal degradation tests of composite and structural tests of fastener; (7) selection of MLI materials and system; (8) definition of a conceptual MLI system design; (9) evaluation of nondestructive inspection techniques and definition of procedures for repair of damaged areas; and (10) preparation of preliminary specifications.

NDT detection and quantification of induced defects on composite helicopter rotor blade and UAV wing sections

NASA Astrophysics Data System (ADS)

Findeis, Dirk; Gryzagoridis, Jasson; Musonda, Vincent

2008-09-01

Digital Shearography and Infrared Thermography (IRT) techniques were employed to test non-destructively samples from aircraft structures of composite material nature. Background information on the techniques is presented and it is noted that much of the inspection work reviewed in the literature has focused on qualitative evaluation of the defects rather than quantitative. There is however, need to quantify the defects if the threshold rejection criterion of whether the component inspected is fit for service has to be established. In this paper an attempt to quantify induced defects on a helicopter main rotor blade and Unmanned Aerospace Vehicle (UAV) composite material is presented. The fringe patterns exhibited by Digital Shearography were used to quantify the defects by relating the number of fringes created to the depth of the defect or flaw. Qualitative evaluation of defects with IRT was achieved through a hot spot temperature indication above the flaw on the surface of the material. The results of the work indicate that the Shearographic technique proved to be more sensitive than the IRT technique. It should be mentioned that there is "no set standard procedure" tailored for testing of composites. Each composite material tested is more likely to respond differently to defect detection and this depends generally on the component geometry and a suitable selection of the loading system to suit a particular test. The experimental procedure that is reported in this paper can be used as a basis for designing a testing or calibration procedure for defects detection on any particular composite material component or structure.

Mechanical Property Analysis on Sandwich Structured Hybrid Composite Made from Natural Fibre, Glass Fibre and Ceramic Fibre Wool Reinforced with Epoxy Resin

NASA Astrophysics Data System (ADS)

Bharat, K. R.; Abhishek, S.; Palanikumar, K.

2017-06-01

Natural fibre composites find wide range of applications and usage in the automobile and manufacturing industries. They find lack in desired properties, which are required for present applications. In current scenario, many developments in composite materials involve the synthesis of Hybrid composite materials to overcome some of the lacking properties. In this present investigation, two sandwich structured hybrid composite materials have been made by reinforcing Aloe Vera-Ceramic Fibre Wool-Glass fibre with Epoxy resin matrix and Sisal fibre-Ceramic Fibre Wool-Glass fibre with Epoxy resin matrix and its mechanical properties such as Tensile, Flexural and Impact are tested and analyzed. The test results from the two samples are compared and the results show that sisal fibre reinforced hybrid composite has better mechanical properties than aloe vera reinforced hybrid composite.

The behavior of delaminations in composite materials - experimental results

NASA Astrophysics Data System (ADS)

Chermoshentseva, A. S.; Pokrovskiy, A. M.; Bokhoeva, L. A.

2016-02-01

Delamination is one of the most common failure modes of composite materials. It may occur as a consequence of imperfections in the production process or the effects of external factors during the operational life of the composite laminates, such as the impact by foreign objects. This paper presents the results of mechanical tests and the optimum degrees of filling the composite materials (CM) with hydrophobic powder (Tarkosil T-20) depending on the latter mass concentration. The results present test samples of the CM with the underlying interlayer defects. The samples were fabricated of twenty-ply pre-preg (fiberglass or carbon fiber). The industrial grade glass is T-25 (VM) specification 6-11-380-76. The composite materials have nanosized additives in structure. The volume concentration of nanopowders is varying from 0.1% to 0.5%. This kind of research has been done for the first time.

Combustion toxicology of epoxy/carbon fiber composites

NASA Technical Reports Server (NTRS)

Cagliostro, D. E.

1981-01-01

A combustion toxicology test was developed to screen materials for aerospace applications. The system is called the radiant panel test facility. A description of the facility and some preliminary results from tests on a Navy 3501-6AS composite, a typical composite for fighter aircraft, are presented.

Graphite/epoxy composite adapters for the Space Shuttle/Centaur vehicle

NASA Technical Reports Server (NTRS)

Kasper, Harold J.; Ring, Darryl S.

1990-01-01

The decision to launch various NASA satellite and Air Force spacecraft from the Space Shuttle created the need for a high-energy upper stage capable of being deployed from the cargo bay. Two redesigned versions of the Centaur vehicle which employed a graphite/epoxy composite material for the forward and aft adapters were selected. Since this was the first time a graphite/epoxy material was used for Centaur major structural components, the development of the adapters was a major effort. An overview of the composite adapter designs, subcomponent design evaluation test results, and composite adapter test results from a full-scale vehicle structural test is presented.

Antibacterial Properties of Calcium Fluoride-Based Composite Materials: In Vitro Study

PubMed Central

Zarzycka, Beata; Grzegorczyk, Janina; Sokołowski, Krzysztof; Półtorak, Konrad; Sokołowski, Jerzy

2016-01-01

The aim of the study was to evaluate antibacterial activity of composite materials modified with calcium fluoride against cariogenic bacteria S. mutans and L. acidophilus. One commercially available conventional light-curing composite material containing fluoride ions (F2) and two commercially available flowable light-curing composite materials (Flow Art and X-Flow) modified with 1.5, 2.5, and 5.0 wt% anhydrous calcium fluoride addition were used in the study. Composite material samples were incubated in 0.95% NaCl at 35°C for 3 days; then dilution series of S. mutans and L. acidophilus strains were made from the eluates. Bacteria dilutions were cultivated on media afterwards. Colony-forming unit per 1 mL of solution (CFU/mL) was calculated. Composite materials modified with calcium fluoride highly reduced (p < 0.001) bacteria growth compared to commercially available composite materials containing fluoride compounds. The greatest reduction in bacteria growth was observed for composite materials modified with 1.5% wt. CaF2. All three tested composite materials showed statistically greater antibacterial activity against L. acidophilus than against S. mutans. PMID:28053976

Effects of air-polishing powders on color stability of composite resins

PubMed Central

GÜLER, Ahmet Umut; DURAN, Ibrahim; YÜCEL, Ali Çagin; ÖZKAN, Pelin

2011-01-01

Objectives The purpose of this study was to investigate the effect of different air-polishing powders on the color stability of different types of composite resin restorative materials. Material and methods Thirty cylindrical specimens (15×2 mm) were prepared for each of 7 composite resin restorative materials. All specimens were polished with a series of aluminum oxide polishing discs (Sof-Lex). The prepared specimens of each composite resin were randomly divided into 3 groups of 10 specimens each, for control (Group-C) and two air-powder applications (Group-CP: Cavitron Prophy-Jet; Group-PS: Sirona ProSmile prophylaxis powder). A standard air-polishing unit (ProSmile Handly) was used. All specimens were air-powdered for 10 s at 4-bar pressure. The distance of the spray nosel from the specimens was approximately 10 mm and angulation of the nosel was 90º. Specimens were stored in 100 mL of coffee (Nescafe Classic) for 24 h at 37ºC. Color measurement of all specimens was recorded before and after exposure to staining agent with a colorimeter (Minolta CR-300). Color differences (∆E*) between the 2 color measurements (baseline and after 24 h storage) were calculated. The data were analyzed with a 2-way ANOVA test, and mean values were compared by the Tukey HSD test (p≤0.05). Results According to the 2-way ANOVA results, composite resin restorative materials, air-polishing powders, and their interaction were statistically significant (p<0.05) For Aelite Aesthetic Enemal, Filtek Z250, Grandio, CeramX Mono, and Quixfil composite resin restorative materials, no significant difference was observed between Group-PS and Group-CP (p>.05) and these groups demonstrated the highest ∆E* values. For Filtek Silorane and IntenS, the highest ∆E* values were observed in Group-PS. The lowest ∆E* values for all composite resin groups were observed in Group-C. When comparing the 7 composite resin restorative materials, Aelite Aesthetic Enemal demonstrated significantly less ∆E* values than the other composite resins tested. The highest ∆E* values were observed in Quixfil. Conclusion Except for Quixfil, all control groups of composite resins that were polished Sof-Lex exhibited clinically acceptable ∆E values (<3.7). Air-polishing applications increased the color change for all composite resin restorative materials tested. Composite restorations may require re-polishing after air-polishing. PMID:21922122

Characterization and manufacture of braided composites for large commercial aircraft structures

NASA Technical Reports Server (NTRS)

Fedro, Mark J.; Willden, Kurtis

1992-01-01

Braided composite materials has been recognized as a potential cost effective material form for fuselage structural elements. Consequently, there is a strong need for more knowledge in the design, manufacture, test, and analysis of textile structural composites. Advance braided composite technology is advanced towards applications to a large commercial transport fuselage. The mechanics are summarized of materials and manufacturing demonstration results which were obtained in order to acquire an understanding of how braided composites can be applied to a commercial fuselage. Textile composites consisting of 2-D, 2-D triaxial, and 3-D braid patterns with thermoplastic and two resin transfer molding resin systems were studied. The structural performance of braided composites was evaluated through an extensive mechanical test program. Analytical methods were also developed and applied to predict the following: internal fiber architecture; stiffness; fiber stresses; failure mechanisms; notch effects; and the history of failure of the braided composite specimens. The applicability of braided composites to a commercial transport fuselage was further assessed through a manufacturing demonstration.

A non-orthogonal material model of woven composites in the preforming process

DOE PAGES

Zhang, Weizhao; Ren, Huaqing; Liang, Biao; ...

2017-05-04

Woven composites are considered as a promising material choice for lightweight applications. An improved non-orthogonal material model that can decouple the strong tension and weak shear behaviour of the woven composite under large shear deformation is proposed for simulating the preforming of woven composites. The tension, shear and compression moduli in the model are calibrated using the tension, bias-extension and bending experiments, respectively. The interaction between the composite layers is characterized by a sliding test. The newly developed material model is implemented in the commercial finite element software LS-DYNA® and validated by a double dome study.

Standardization of the carbon-phenolic materials and processes. Vol. 2: Test methods and specifications

NASA Technical Reports Server (NTRS)

Hall, William B.

1988-01-01

Carbon-phenolic composite materials are used in the ablation process in the nozzles of the Space Shuttle Main Engine. The nozzle is lined with carbon cloth-phenolic resin composites. The extreme heat and erosion of the burning propellant are controlled by the carbon-phenolic composite by means of ablation, a heat and mass transfer process in which a large amount of heat is dissipated by sacrificailly removing material from a surface. Phenolic materials ablate with the initial formation of a char. The depth of the char is a function of the heat conduction coefficient of the composite. The char layer is a poor conductor so it protects the underlying phenolic composite from the high heat of the burning propellant. The nozzle component ablative liners (carbon cloth-phenolic resin composites) are tape wrapped, hydroclave and/or autoclave cured, machined and assembled. The tape consists of prepreg broadcloth. The materials flow sheet for the nozzle ablative liners is given. The prepreg is a three component system: phenolic resin, carbon cloth, and carbon filler. This is Volume 2 of the report, Test Methods and Specifications.

Aspects regarding the correlation between the physical-mechanical and tribological characteristics of composites materials reinforced with carbon fibers

NASA Astrophysics Data System (ADS)

Caliman, R.

2017-08-01

The purpose of this paper is to highlight a number of factors that influence the physical-mechanical and tribological characteristics of sintered composite materials. Such factors are grouped generally in two categories: technological parameters (pressure compacting, sintering temperature, sintering duration, heat treatment) and the receipt of sintered composite materials. In this paper is presented a program of experiments developed both in composite materials sintered polymer matrix (non-metallic) and in the metal matrix (eg., Al) which was prepared in advance a methodology original production and research for this particular type of materials. The experiments have focused development and testing of a number of 14 polymer composite and 5 composite sintered Al base, in both situations armed with carbon fiber in various forms. Tribological tests followed the establishment of the coefficient of friction and wear rate of the sliding speed at the constant values (v = 7.2 mm/s) and the normal load (N = 8 daN) and for different orientations of the fibers to the direction of sliding: normal (N type), parallel (P) and antiparallel-perpendicular (AP type).

Application of IDT Sensors for Structural Health Monitoring of Windmill Turbine Blades Made of Composite Material

NASA Astrophysics Data System (ADS)

Nalladega, V.; Na, J. K.; Druffner, C.

2011-06-01

Interdigital transducers (IDT) generate and receive ultrasonic surface waves without the complexity involved with secondary devices such as angled wedges or combs. The IDT sensors have been successfully applied for the NDE of homogeneous materials like metals in order to detect cracks and de-bond. However, these transducers have not been yet adapted for complex and anisotropic materials like fiber-reinforced composites. This work presents the possibility of using IDT sensors for monitoring structural damages in wind turbine blades, typically made of fiberglass composites. IDT sensors with a range of operating frequency between 250 kHz and 1 MHz are initially tested on representative composite test panels for ultrasonic surface wave properties including beam spread, propagation distance and effect of material's anisotropy. Based on these results, an optimum frequency range for the IDT sensor is found to be 250-500 kHz. Subsequently, IDT sensors with operating frequency 500 kHz are used to detect and quantify artificial defects created in the composite test samples. Discussions are made on the interaction of ultrasonic fields with these defects along with the effects of fiber directionality and composite layer stacking.

Performance characterization of active fiber-composite actuators for helicopter rotor blade applications

NASA Astrophysics Data System (ADS)

Wickramasinghe, Viresh K.; Hagood, Nesbitt W.

2002-07-01

The primary objective of this work was to characterize the performance of the Active Fiber Composite (AFC) actuator material system for the Boeing Active Material Rotor (AMR) blade application. The AFCs were a new structural actuator system consisting of piezoceramic fibers embedded in an epoxy matrix and sandwiched between interdigitated electrodes to orient the driving electric field in the fiber direction to use the primary piezoelectric effect. These actuators were integrated directly into the blade spar laminate as active plies within the composite structure to perform structural actuation for vibration control in helicopters. Therefore, it was necessary to conduct extensive electromechanical material characterization to evaluate AFCs both as actuators and as structural components of the rotor blade. The characterization tests designed to extract important electromechanical properties under simulated blade operating conditions included stress-strain tests, free strain tests and actuation under tensile load tests. This paper presents the test results as well as the comprehensive testing process developed to evaluate the relevant AFC material properties. The results from this comprehensive performance characterization of the AFC material system supported the design and operation of the Boeing AMR blade scheduled for hover and forward flight wind tunnel tests.

Ultrasonic nondestructive testing of composite materials using disturbed coincidence conditions

NASA Astrophysics Data System (ADS)

Bause, F.; Olfert, S.; Schröder, A.; Rautenberg, J.; Henning, B.; Moritzer, E.

2012-05-01

In this contribution we present a new method detecting changes in the composite material's acoustic behavior by analyzing disturbed coincidence conditions on plate-like test samples. The coincidence condition for an undamaged GFRP test sample has been experimentally identified using Schlieren measurements. Disturbances of this condition follow from a disturbed acoustic behavior of the test sample which is an indicator for local damages in the region inspected. An experimental probe has been realized consisting of two piezoceramic elements adhered to the nonparallel sides of an isosceles trapezoidal body made of silicone. The base angles of the trapezoidal body have been chosen such that the incident wave meets pre-measured condition of coincidence. The receiving element receives the geometric reflection of the acoustic wave scattered at the test sample's surface which corresponds to the non-coupled part of the incident wave as send by the sending element. Analyzing the transfer function or impulse response of the electro-acoustic system (transmitter, scattering at test sample, receiver), it is possible to detect local disturbances with respect to Cramer's coincidence rule. Thus, it is possible to realize a very simple probe for local ultrasonic nondestructive testing of composite materials (as well as non-composite material) which can be integrated in a small practical device and is good for small size inspection areas.

Composite structural materials

NASA Technical Reports Server (NTRS)

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1979-01-01

A multifaceted program is described in which aeronautical, mechanical, and materials engineers interact to develop composite aircraft structures. Topics covered include: (1) the design of an advanced composite elevator and a proposed spar and rib assembly; (2) optimizing fiber orientation in the vicinity of heavily loaded joints; (3) failure mechanisms and delamination; (4) the construction of an ultralight sailplane; (5) computer-aided design; finite element analysis programs, preprocessor development, and array preprocessor for SPAR; (6) advanced analysis methods for composite structures; (7) ultrasonic nondestructive testing; (8) physical properties of epoxy resins and composites; (9) fatigue in composite materials, and (10) transverse thermal expansion of carbon/epoxy composites.

Development of the technology for the fabrication of reliable laminar from control panels

NASA Technical Reports Server (NTRS)

Meade, L. E.; Kays, A. O.; Ferrill, R. S.; Young, H. R.

1977-01-01

Materials were assessed and fabrication techniques were developed for use in the manufacture of wing surface materials compatible with the application of both aluminum alloys and nonmetallic composites. The concepts investigated included perforations and slots in the metallic test panels and microporosity and perforations in the composite test panels. Perforations were produced in the metallic test panels by the electron beam process and slots were developed by controlled gaps between the metal sheets. Microporosity was produced in the composite test panels by the resin bleed process, and perforations were produced by the fugitive fiber technique. Each of these concepts was fabricated into test panels, and air flow tests were conducted on the panels.

Validation of Material Models For Automotive Carbon Fiber Composite Structures Via Physical And Crash Testing (VMM Composites Project)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coppola, Anthony; Faruque, Omar; Truskin, James F

As automotive fuel economy requirements increase, the push for reducing overall vehicle weight will likely include the consideration of materials that have not previously been part of mainstream vehicle design and manufacturing, including carbon fiber composites. Vehicle manufacturers currently rely on computer-aided engineering (CAE) methods as part of the design and development process, so going forward, the ability to accurately and predictably model carbon fiber composites will be necessary. If composites are to be used for structural components, this need applies to both, crash and quasi-static modeling. This final report covers the results of a five-year, $6.89M, 50% cost-shared researchmore » project between Department of Energy (DOE) and the US Advanced Materials Partnership (USAMP) under Cooperative Agreement DE-EE-0005661 known as “Validation of Material Models for Automotive Carbon Fiber Composite Structures Via Physical and Crash Testing (VMM).” The objective of the VMM Composites Project was to validate and assess the ability of physics-based material models to predict crash performance of automotive primary load-carrying carbon fiber composite structures. Simulation material models that were evaluated included micro-mechanics based meso-scale models developed by the University of Michigan (UM) and micro-plane models by Northwestern University (NWU) under previous collaborations with the DOE and Automotive Composites Consortium/USAMP, as well as five commercial crash codes: LS-DYNA, RADIOSS, VPS/PAM-CRASH, Abaqus, and GENOA-MCQ. CAE predictions obtained from seven organizations were compared with experimental results from quasi-static testing and dynamic crash testing of a thermoset carbon fiber composite front-bumper and crush-can (FBCC) system gathered under multiple loading conditions. This FBCC design was developed to demonstrate progressive crush, virtual simulation, tooling, fabrication, assembly, non-destructive evaluation and crash testing advances in order to assess the correlation of the predicted results to the physical tests. The FBCC was developed to meet a goal of 30-35% mass reduction while aiming for equivalent energy absorption as a steel component for which baseline experimental results were obtained from testing in the same crash modes. The project also evaluated crash performance of thermoplastic composite structures fabricated from commercial prepreg materials and low cost carbon fiber sourced from Oak Ridge National Laboratory. The VMM Project determined that no set of predictions from a CAE supplier were found to be universally accurate among all the six crash modes evaluated. In general, crash modes that were most dependent on the properties of the prepreg were more accurate than those that were dependent on the behavior of the joints. The project found that current CAE modeling methods or best practices for carbon fiber composites have not achieved standardization, and accuracy of CAE is highly reliant on the experience of its users. Coupon tests alone are not sufficient to develop an accurate material model, but it is necessary to bridge the gap between the coupon data and performance of the actual structure with a series of subcomponent level tests. Much of the unreliability of the predictions can be attributed to shortcomings in our ability to mathematically link the effects of manufacturing and material variability into the material models. This is a subject of ongoing research in the industry. The final report is organized by key technical tasks to describe how the validation project developed, modeled and compared crash data obtained on the composite FBCC to the multiple sets of CAE predictions. Highlights of the report include a discussion of the quantitative comparison between predictions and experimental data, as well as an in-depth discussion of remaining technological gaps that exist in the industry, which are intended to spur innovations and improvements in CAE technology.« less

Testing Composites

NASA Technical Reports Server (NTRS)

1981-01-01

A device for testing composites for strength characteristics has been developed by Acoustic Emission Technology Corporation. Called the Model 206AU, the system is lightweight and portable. It is comprised of three sections. The "pulser" section injects ultrasonic waves into the material under test. A receiver picks up the simulated stress waves as they pass through the material and relays the signals to the acoustic emission section, where they are electronically analyzed.

Radiopacity evaluation of contemporary resin composites by digitization of images.

PubMed

Ermis, R Banu; Yildirim, Derya; Yildiz, Gul; Gormez, Ozlem

2014-07-01

The aim of this study was to evaluate the radiopacity of different composite resins and compare the values to those of human enamel and dentine. Five specimens of each material with thicknesses of 2 mm were prepared and radiographed alongside aluminum step wedge and human enamel and dentin. Three occlusal radiographs for each material were taken and digitized using a desktop scanner. Mean gray values of the test materials were measured using Image J software. Then a conversion was performed according to establish the radiopacity of the test materials, in millimeters of equivalent Al. Data were analyzed using one-way analysis of variance and Duncan multiple range tests (P < 0.05). The radiopacity values varied among the restorative materials (P < 0.05). The radiopacity values of the materials tested were, in decreasing order: Enamel Plus HRI > Z250 > Filtek Ultimate ≥ Z550 > Nexcomp ≥ Nanoceram Bright > enamel ≥ Estelite Sigma Quick > Clearfil Majesty Esthetic ≥ Reflexions XLS ≥ Aelite LS Posterior ≥ dentin ≥ 2 mm Al. All resin composite materials investigated in this study presented different radiopacity values. However, all materials had radiopacity values greater than dentin and had sufficient radiopacity to meet International Organization for Standardization 4049 standard.

Thermal design of composite materials high temperature attachments

NASA Technical Reports Server (NTRS)

1972-01-01

The thermal aspects of using filamentary composite materials as primary airframe structures on advanced atmospheric entry spacecraft such as the space shuttle vehicle were investigated to identify and evaluate potential design approaches for maintaining composite structures within allowable temperature limits at thermal protection system (TPS) attachments and/or penetrations. The investigation included: (1) definition of thermophysical data for composite material structures; (2) parametric characterization and identification of the influence of the aerodynamic heating and attachment design parameters on composite material temperatures; (3) conceptual design, evaluation, and detailed thermal analyses of temperature limiting design concepts; and (4) the development of experimental data for assessment of the thermal design methodologies and data used for evaluation of the temperature-limiting design concepts. Temperature suppression attachment concepts were examined for relative merit. The simple isolator was identified as the most weight-effective concept and was selected for detail design, thermal analysis, and testing. Tests were performed on TPS standoff attachments to boron/aluminum, boron/polyimide and graphite/epoxy composite structures.

Modeling the Mechanical Behavior of Ceramic Matrix Composite Materials

NASA Technical Reports Server (NTRS)

Jordan, William

1998-01-01

Ceramic matrix composites are ceramic materials, such as SiC, that have been reinforced by high strength fibers, such as carbon. Designers are interested in using ceramic matrix composites because they have the capability of withstanding significant loads while at relatively high temperatures (in excess of 1,000 C). Ceramic matrix composites retain the ceramic materials ability to withstand high temperatures, but also possess a much greater ductility and toughness. Their high strength and medium toughness is what makes them of so much interest to the aerospace community. This work concentrated on two different tasks. The first task was to do an extensive literature search into the mechanical behavior of ceramic matrix composite materials. This report contains the results of this task. The second task was to use this understanding to help interpret the ceramic matrix composite mechanical test results that had already been obtained by NASA. Since the specific details of these test results are subject to the International Traffic in Arms Regulations (ITAR), they are reported in a separate document (Jordan, 1997).

Preliminary Validation of Composite Material Constitutive Characterization

Treesearch

John G. Michopoulos; Athanasios lliopoulos; John C. Hermanson; Adrian C. Orifici; Rodney S. Thomson

2012-01-01

This paper is describing the preliminary results of an effort to validate a methodology developed for composite material constitutive characterization. This methodology involves using massive amounts of data produced from multiaxially tested coupons via a 6-DoF robotic system called NRL66.3 developed at the Naval Research Laboratory. The testing is followed by...

Development and Evaluation of High Temperature Gaskets for Hypersonic and Reentry Applications

NASA Technical Reports Server (NTRS)

Singh, Mrityunjay; Shpargel, Tarah

2007-01-01

A wide variety of flexible gasket compositions were developed and tested at high temperatures. The gasket material system has high temperature capability. GRABER sealants were very effective in sealing machined ACC-4 composite surfaces. The gasket composition do not bond strongly with the ACC-4 substrate materials. The density of gasket materials can be tailored to show appropriate compressibility.

Tribological study of non-asbestos fiber reinforced phenolic composites for braking applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gopal, P.; Dharani, L.R.; Blum, F.D.

A cashew modified phenolic resin was used as the binder to prepare several different nonasbestos fiber reinforced composite friction materials. Friction-wear tests were conducted at various loads, speeds and temperatures on a Chase friction testing machine. The fade and wear characteristics of glass and carbon fiber reinforced friction materials were studied. The wear rates of hybrid composites containing Kevlar{reg_sign} (registered trademark of E.I. duPont de Nemours) pulp were compared to those of control composites without Kevlar{reg_sign} pulp.

Challenges and Opportunities in Design, Fabrication, and Testing of High Temperature Joints in Ceramics and Ceramic Composites

NASA Technical Reports Server (NTRS)

Singh, M.; Levine, S. R. (Technical Monitor)

2001-01-01

Ceramic joining has been recognized as an enabling technology for successful utilization of advanced ceramics and composite materials. A number of joint design and testing issues have been discussed for ceramic joints in silicon carbide-based ceramics and fiber-reinforced composites. These joints have been fabricated using an affordable, robust ceramic joining technology (ARCJoinT). The microstructure and good high temperature mechanical capability (compressive and flexural strengths) of ceramic joints in silicon carbide-based ceramics and composite materials are reported.

Study of erosion characterization of carbon fiber reinforced composite material

NASA Astrophysics Data System (ADS)

Debnath, Uttam Kumar; Chowdhury, Mohammad Asaduzzaman; Kowser, Md. Arefin; Mia, Md. Shahin

2017-06-01

Carbon fiber composite materials are widely used at different engineering and industrial applications there are good physical, mechanical, chemical properties and light weight. Erosion behavior of materials depends on various factors such as impact angle, particle velocity, particle size, particle shape, particle type, particle flux, temperature of the tested materials. Among these factors impact angle and particle velocity have been recognized as two parameters that noticeably influence the erosion rates of all tested materials. Irregular shaped sand (SiO2) particles of various sizes (200-300 µm, 400-500 µm, and 500-600 µm) were selected erosive element. Tested conditions such as impingement angles between 15 degree to 90 degree, impact velocities between 30-50 m/sec, and stand-off distances 15-25 mm at surrounding room temperature were maintained. The highest level of erosion of the tested composite is obtained at 60° impact angle, which signifies the semi-ductile behavior of this material. Erosion showed increasing trend with impact velocity and decreasing nature in relation to stand-off distance. Surface damage was analyzed using SEM to examine the nature of the erosive wear mechanism.

Determination of replicate composite bone material properties using modal analysis.

PubMed

Leuridan, Steven; Goossens, Quentin; Pastrav, Leonard; Roosen, Jorg; Mulier, Michiel; Denis, Kathleen; Desmet, Wim; Sloten, Jos Vander

2017-02-01

Replicate composite bones are used extensively for in vitro testing of new orthopedic devices. Contrary to tests with cadaveric bone material, which inherently exhibits large variability, they offer a standardized alternative with limited variability. Accurate knowledge of the composite's material properties is important when interpreting in vitro test results and when using them in FE models of biomechanical constructs. The cortical bone analogue material properties of three different fourth-generation composite bone models were determined by updating FE bone models using experimental and numerical modal analyses results. The influence of the cortical bone analogue material model (isotropic or transversely isotropic) and the inter- and intra-specimen variability were assessed. Isotropic cortical bone analogue material models failed to represent the experimental behavior in a satisfactory way even after updating the elastic material constants. When transversely isotropic material models were used, the updating procedure resulted in a reduction of the longitudinal Young's modulus from 16.00GPa before updating to an average of 13.96 GPa after updating. The shear modulus was increased from 3.30GPa to an average value of 3.92GPa. The transverse Young's modulus was lowered from an initial value of 10.00GPa to 9.89GPa. Low inter- and intra-specimen variability was found. Copyright © 2016 Elsevier Ltd. All rights reserved.

Evaluation of composite materials providing improved acoustic transmission loss for UAVs

NASA Astrophysics Data System (ADS)

Callicoat, Jeffrey R.

With the proliferation of Unmanned Aerial Vehicles (UAVs) in civilian airspace in the near future, community noise will be a major issue of concern. Numerous studies have shown a direct link between community noise pollution (i.e., road traffic noise and airport noise) and serious health problems. There exists, therefore, a pressing need to create quiet UAVs, and this drives the need for noise-attenuating materials and structures suitable for UAV airframe fabrication. By shrouding predominant noise sources such as the engine, exhaust, and even the propeller (in the case of a ducted fan) with the airframe structure, the airframe can serve as a noise transmission barrier and substantially reduce UAV noise profiles. The present research effort is an experimental investigation of light-weight fiber-reinforced composite materials to provide high acoustic transmission loss (TL) for use in fabricating UAV airframes. A transmission loss tube acoustic test system was designed, fabricated, and validated, and extensive testing was done on numerous composite layups of interest for UAV fabrication. Composites under study included carbon fiber, fiberglass, and Kevlar fabrics as skin materials along with vinyl foam, Nomex honeycomb, and balsawood as core materials. Results from testing small 3"x3" samples in the TL tube led to the selection of four composite sandwich panels of interest for further study. Larger 36"x36" test samples of these selected layups were then fabricated and tested using a 2-room methodology. Whereas the TL tube yielded results in the stiffness-controlled region of acoustic behavior, the 2-room tests produced results in the mass-controlled region for these materials, enabling relative performance comparisons over both acoustic regimes. Recognizing that a good material for airframe fabrication should possess not only high TL, but also low weight and high stiffness, load-deflection tests were conducted and overall material performance was compared in terms of the parameter [(TL * stiffness) / surface density]. A sandwich panel layup of 5.7 oz carbon fiber skins with a vinyl foam core emerged as the preferable material choice, and a UAV fuselage of this construction was evaluated in the OSU anechoic chamber and shown to substantially reduce sound propagation from enclosed noise sources.

Characterization and damage evaluation of advanced materials

NASA Astrophysics Data System (ADS)

Mitrovic, Milan

Mechanical characterization of advanced materials, namely magnetostrictive and graphite/epoxy composite materials, is studied in this dissertation, with an emphasis on damage evaluation of composite materials. Consequently, the work in this dissertation is divided into two parts, with the first part focusing on characterization of the magneto-elastic response of magnetostrictlve materials, while the second part of this dissertation describes methods for evaluating the fatigue damage in composite materials. The objective of the first part of this dissertation is to evaluate a nonlinear constitutive relation which more closely depict the magneto-elastic response of magnetostrictive materials. Correlation between experimental and theoretical values indicate that the model adequately predicts the nonlinear strain/field relations in specific regimes, and that the currently employed linear approaches are inappropriate for modeling the response of this material in a structure. The objective of the second part of this dissertation is to unravel the complexities associated with damage events associated with polymeric composite materials. The intent is to characterize and understand the influence of impact and fatigue induced damage on the residual thermo-mechanical properties and compressive strength of composite systems. The influence of fatigue generated matrix cracking and micro-delaminations on thermal expansion coefficient (TEC) and compressive strength is investigated for woven graphite/epoxy composite system. Experimental results indicate that a strong correlation exists between TEC and compressive strength measurements, indicating that TEC measurements can be used as a damage metric for this material systems. The influence of delaminations on the natural frequencies and mode shapes of a composite laminate is also investigated. Based on the changes of these parameters as a function of damage, a methodology for determining the size and location of damage is suggested. Finally, the influence of loading parameters on impact damage growth is investigated experimentally though constant amplitude and spectrum loading fatigue tests. Based on observed impact damage growth during these tests it is suggested that the low load levels can be deleted from the standardized test sequence without significant influence on impact damage propagation.

Critical Joints in Large Composite Primary Aircraft Structures. Volume 3: Ancillary Test Results

NASA Technical Reports Server (NTRS)

Bunin, Bruce L.; Sagui, R. L.

1985-01-01

A program was conducted to develop the technology for critical structural joints for composite wing structure that meets all the design requirements of a 1990 commercial transport aircraft. The results of a comprehensive ancillary test program are summarized, consisting of single-bolt composite joint specimens tested in a variety of configurations. These tests were conducted to characterize the strength and load deflection properties that are required for multirow joint analysis. The composite material was Toray 300 fiber and Ciba-Geigy 914 resin, in the form of 0.005 and 0.01 inch thick unidirectional tape. Tests were conducted in single and double shear for loaded and unloaded hole configurations under both tensile and compressive loading. Two different layup patterns were examined. All tests were conducted at room temperature. In addition, the results of NASA Standard Toughness Test (NASA RP 1092) are reported, which were conducted for several material systems.

Self-healing nanocomposite using shape memory polymer and carbon nanotubes

NASA Astrophysics Data System (ADS)

Liu, Yingtao; Rajadas, Abhishek; Chattopadhyay, Aditi

2013-04-01

Carbon fiber reinforced composites are used in a wide range of applications in aerospace, mechanical, and civil structures. Due to the nature of material, most damage in composites, such as delaminations, are always barely visible to the naked eye, which makes it difficult to detect and repair. The investigation of biological systems has inspired the development and characterization of self-healing composites. This paper presents the development of a new type of self-healing material in order to impede damage progression and conduct in-situ damage repair in composite structures. Carbon nanotubes, which are highly conductive materials, are mixed with shape memory polymer to develop self-healing capability. The developed polymeric material is applied to carbon fiber reinforced composites to automatically heal the delamination between different layers. The carbon fiber reinforced composite laminates are manufactured using high pressure molding techniques. Tensile loading is applied to double cantilever beam specimens using an MTS hydraulic test frame. A direct current power source is used to generate heat within the damaged area. The application of thermal energy leads to re-crosslinking in shape memory polymers. Experimental results showed that the developed composite materials are capable of healing the matrix cracks and delaminations in the bonded areas of the test specimens. The developed self-healing material has the potential to be used as a novel structural material in mechanical, civil, aerospace applications.

Applications of laser ultrasound NDT methods on composite structures in aerospace industry

NASA Astrophysics Data System (ADS)

Kalms, Michael; Focke, Oliver; v. Kopylow, Christoph

2008-09-01

Composite materials are used more and more in aircraft production. Main composite types are Carbon Fiber Reinforced Plastics (CFRP), Glass Fiber Reinforced Plastics (GFRP) and metal-aluminium laminates (e. g. Glass Fiber Aluminium Reinforced GLARE©). Typical parts made of CFRP material are flaps, vertical and horizontal tail planes, center wing boxes, rear pressure bulkheads, ribs and stringers. These composite parts require adequate nondestructive testing (NDT) methods. Flaws to be detected are delaminations and debondings, porosity and foreign body inclusion. Manual ultrasonic testing with single element transducers is still the most applied method for composite parts with small and medium size. The extension of the conventional ultrasound technique for nondestructive testing with the laser ultrasound method brings new possibilities into the production processes for example the inspection of complex CFRP-components and the possibilities of online observation under remote control. In this paper we describe the principle of laser ultrasound with respect to the demands of nondestructive testing especially of small complex CFRP and C/PPS parts. We report applications of laser-based ultrasound options with generated types of guided and bulk waves on modern aircraft materials.

Analysis of Graphite Reinforced Cementitious Composites

NASA Technical Reports Server (NTRS)

Vaughan, Robert E.; Gilbert, John A.; Spanyer, Karen (Technical Monitor)

2001-01-01

This paper describes analytical methods that can be used to determine the deflections and stresses in highly compliant graphite-reinforced cementitious composites. It is demonstrated that the standard transform section fails to provide accurate results when the elastic modulus ratio exceeds 20. So an alternate approach is formulated by using the rule of mixtures to determine a set of effective material properties for the composite. Tensile tests are conducted on composite samples to verify this approach; and, when the effective material properties are used to characterize the deflections of composite beams subject to pure bending, an excellent agreement is obtained. Laminated composite plate theory is also investigated as a means for analyzing even more complex composites, consisting of multiple graphite layers oriented in different directions. In this case, composite beams are analyzed by incorporating material properties established from tensile tests. Finite element modeling is used to verity the results and, considering the complexity of the samples, a very good agreement is obtained.

Design and analysis of a novel latch system implementing fiber-reinforced composite materials

NASA Astrophysics Data System (ADS)

Guevara Arreola, Francisco Javier

The use of fiber-reinforced composite materials have increased in the last four decades in high technology applications due to their exceptional mechanical properties and low weight. In the automotive industry carbon fiber have become popular exclusively in luxury cars because of its high cost. However, Carbon-glass hybrid composites offer an effective alternative to designers to implement fiber-reinforced composites into several conventional applications without a considerable price increase maintaining most of their mechanical properties. A door latch system is a complex mechanism that is under high loading conditions during car accidents such as side impacts and rollovers. Therefore, the Department of Transportation in The United States developed a series of tests that every door latch system comply in order to be installed in a vehicle. The implementation of fiber-reinforced composite materials in a door latch system was studied by analyzing the material behavior during the FMVSS No. 206 transverse test using computational efforts and experimental testing. Firstly, a computational model of the current forkbolt and detent structure was developed. Several efforts were conducted in order to create an effective and time efficient model. Two simplified models were implemented with two different contact interaction approaches. 9 composite materials were studied in forkbolt and 5 in detent including woven carbon fiber, unidirectional carbon fiber, woven carbon-glass fiber hybrid composites and unidirectional carbon-glass fiber hybrid composites. The computational model results showed that woven fiber-reinforced composite materials were stiffer than the unidirectional fiber-reinforced composite materials. For instance, a forkbolt made of woven carbon fibers was 20% stiffer than a forkbolt made of unidirectional fibers symmetrically stacked in 0° and 90° alternating directions. Furthermore, Hybrid composite materials behaved as expected in forkbolt noticing a decline in the load-displacement slopes while the percentage of glass fiber increased. In the other hand, results showed that a detent made of only glass fiber layers was preferable than a carbon-glass fiber hybrid detent due to the high stresses shown in carbon fiber layers. Ultimately, forkbolt and detent were redesigned according to their functionality and test results. It was observed that the new design was stiffer than the original by showing a steeper load-displacement curve. Subsequently, an experimental procedure was performed in order to correlate computational model results. Fiber-reinforced composite forkbolt and detent were waterjet cut from a composite laminate manufactured by Vacuum Assisted Resin Transfer Molding (VART) process. Then, samples were tested according to the computational model. Six testing sample combinations of forkbolt and detent were tested including the top three woven iterations forkbolts from the computational model paired with woven and unidirectional glass fiber detents. Test results showed a stiffness drop of 15% when the carbon fiber percentage decreases from 100% to 75%. Also, it was observed that woven glass fiber detent was superior to the unidirectional glass fiber detent by presenting a forkbolt-detent stiffness 38% higher. Moreover, the new design of forkbolt and detent were tested showing a stiffness increment of 29%. Furthermore, it was observed that fiber-reinforced composite forkbolt and detent did not reach the desired load of 5000 N. However, the redesigned forkbolt made of 100% woven carbon fiber and the redesign detent made of 100% woven glass fiber were close to reach that load. The design review based on test results performed (DRBTR) showed that components did not fail where the computational model concluded to be the areas with the highest maximum principal stress. In contrast to the computational model, all samples failed at the contact area between forkbolt and detent.

High heat flux testing of CFC composites for the tokamak physics experiment

NASA Astrophysics Data System (ADS)

Valentine, P. G.; Nygren, R. E.; Burns, R. W.; Rocket, P. D.; Colleraine, A. P.; Lederich, R. J.; Bradley, J. T.

1996-10-01

High heat flux (HHF) testing of carbon fiber reinforced carbon composites (CFC's) was conducted under the General Atomics program to develop plasma-facing components (PFC's) for Princeton Plasma Physics Laboratory's tokamak physics experiment (TPX). As part of the process of selecting TPX CFC materials, a series of HHF tests were conducted with the 30 kW electron beam test system (EBTS) facility at Sandia National Laboratories, and with the plasma disruption simulator I (PLADIS-I) facility at the University of New Mexico. The purpose of the tests was to make assessments of the thermal performance and erosion behavior of CFC materials. Tests were conducted with 42 different CFC materials. In general, the CFC materials withstood the rapid thermal pulse environments without fracturing, delaminating, or degrading in a non-uniform manner; significant differences in thermal performance, erosion behavior, vapor evolution, etc. were observed and preliminary findings are presented below. The CFC's exposed to the hydrogen plasma pulses in PLADIS-I exhibited greater erosion rates than the CFC materials exposed to the electron-beam pulses in EBTS. The results obtained support the continued consideration of a variety of CFC composites for TPX PFC components.

Properties of five toughened matrix composite materials

NASA Technical Reports Server (NTRS)

Cano, Roberto J.; Dow, Marvin B.

1992-01-01

The use of toughened matrix composite materials offers an attractive solution to the problem of poor damage tolerance associated with advanced composite materials. In this study, the unidirectional laminate strengths and moduli, notched (open-hole) and unnotched tension and compression properties of quasi-isotropic laminates, and compression-after-impact strengths of five carbon fiber/toughened matrix composites, IM7/E7T1-2, IM7/X1845, G40-800X/5255-3, IM7/5255-3, and IM7/5260 have been evaluated. The compression-after-impact (CAI) strengths were determined primarily by impacting quasi-isotropic laminates with the NASA Langley air gun. A few CAI tests were also made with a drop-weight impactor. For a given impact energy, compression after impact strengths were determined to be dependent on impactor velocity. Properties and strengths for the five materials tested are compared with NASA data on other toughened matrix materials (IM7/8551-7, IM6/1808I, IM7/F655, and T800/F3900). This investigation found that all five materials were stronger and more impact damage tolerant than more brittle carbon/epoxy composite materials currently used in aircraft structures.

Effects of commercial aircraft operating environment on composite materials

NASA Technical Reports Server (NTRS)

Chapman, A. J.; Hoffman, D. J.; Hodges, W. T.

1980-01-01

Long term effects of commercial aircraft operating environment on the properties and durability of composite materials are being systematically explored. Composite specimens configured for various mechanical property tests are exposed to environmental conditions on aircraft in scheduled airline service, on racks at major airports, and to controlled environmental conditions in the laboratory. Results of tests following these exposures will identify critical parameters affecting composite durability, and correlation of the data will aid in developing methods for predicting durability. Interim results of these studies show that mass change of composite specimens on commercial aircraft depends upon the regional climate and season, and that mass loss from composite surfaces due to ultraviolet radiation can be largely prevented by aircraft paint.

Tensile properties of textile composites

NASA Technical Reports Server (NTRS)

Avva, V. Sarma; Sadler, Robert L.; Lyon, Malcolm

1992-01-01

The importance of textile composite materials in aerospace structural applications has been gaining momentum in recent years. With a view to better understand the suitability of these materials in aerospace applications, an experimental program was undertaken to assess the mechanical properties of these materials. Specifically, the braided textile preforms were infiltrated with suitable polymeric matrices leading to the fabrication of composite test coupons. Evaluation of the tensile properties and the analyses of the results in the form of strength moduli, Poisson's ratio, etc., for the braided composites are presented. Based on our past experience with the textile coupons, the fabrication techniques have been modified (by incorporating glass microballoons in the matrix and/or by stabilizing the braid angle along the length of the specimen with axial fibers) to achieve enhanced mechanical properties of the textile composites. This paper outlines the preliminary experimental results obtained from testing these composites.

Milestone 4: Test plan for Reusable Hydrogen Composite Tank System (RHCTS). Task 3: Composite tank materials

NASA Technical Reports Server (NTRS)

Greenberg, H. S.

1994-01-01

This document is the detailed test plan for the series of tests enumerated in the preceding section. The purpose of this plan is to present the test objectives, test parameters and procedures, expected performance and data analysis plans, criteria for success, test schedules, and related safety provisions and to describe the test articles, test instrumentation, and test facility requirements. Initial testing will be performed to screen four composite materials for suitability for SSTO LH2 tank loads and environmental conditions. The laminates for this testing will be fabricated by fiber placement, which is the manufacturing approach identified as baseline for the tank wall. Even though hand layup will be involved in fabricating many of the internal structural members of the tank, no hand-layup laminates will be evaluated in the screening or subsequent characterization testing. This decision is based on the understanding that mechanical properties measured for hand-layup material should be at least equivalent to properties measured for fiber-placed material, so that the latter should provide no less than a conservative approximation of the former. A single material will be downselected from these screening tests. This material will be subsequently characterized for impact-damage tolerance and durability under conditions of mechanical and thermal cycling, and to establish a preliminary design database to support ongoing analysis. Next, testing will be performed on critical structural elements fabricated from the selected material. Finally, the 8-foot diameter tank article, containing the critical structural features of the full-scale tank, will be fabricated by fiber placement and tested to verify its structural integrity and LH2 containment.

Radiopacity evaluation of contemporary resin composites by digitization of images

PubMed Central

Ermis, R. Banu; Yildirim, Derya; Yildiz, Gul; Gormez, Ozlem

2014-01-01

Objective: The aim of this study was to evaluate the radiopacity of different composite resins and compare the values to those of human enamel and dentine. Materials and Methods: Five specimens of each material with thicknesses of 2 mm were prepared and radiographed alongside aluminum step wedge and human enamel and dentin. Three occlusal radiographs for each material were taken and digitized using a desktop scanner. Mean gray values of the test materials were measured using Image J software. Then a conversion was performed according to establish the radiopacity of the test materials, in millimeters of equivalent Al. Data were analyzed using one-way analysis of variance and Duncan multiple range tests (P < 0.05). Results: The radiopacity values varied among the restorative materials (P < 0.05). The radiopacity values of the materials tested were, in decreasing order: Enamel Plus HRI > Z250 > Filtek Ultimate ≥ Z550 > Nexcomp ≥ Nanoceram Bright > enamel ≥ Estelite Sigma Quick > Clearfil Majesty Esthetic ≥ Reflexions XLS ≥ Aelite LS Posterior ≥ dentin ≥ 2 mm Al. Conclusion: All resin composite materials investigated in this study presented different radiopacity values. However, all materials had radiopacity values greater than dentin and had sufficient radiopacity to meet International Organization for Standardization 4049 standard. PMID:25202214

Graphite composite truss welding and cap section forming subsystems. Volume 2: Program results

NASA Technical Reports Server (NTRS)

1980-01-01

The technology required to develop a beam builder which automatically fabricates long, continuous, lightweight, triangular truss members in space from graphite/thermoplastics composite materials is described. Objectives are: (1) continue the development of forming and welding methods for graphite/thermoplastic (GR/TP) composite material; (2) continue GR/TP materials technology development; and (3) fabricate and structurally test a lightweight truss segment.

Stress Free Temperature Testing and Residual Stress Calculations on Out-of-Autoclave Composites

NASA Technical Reports Server (NTRS)

Cox, Sarah; Tate, LaNetra C.; Danley, Susan; Sampson, Jeff; Taylor, Brian; Miller, Sandi

2012-01-01

Future launch vehicles will require the incorporation large composite parts that will make up primary and secondary components of the vehicle. NASA has explored the feasibility of manufacturing these large components using Out-of-Autoclave impregnated carbon fiber composite systems through many composites development projects. Most recently, the Composites for Exploration Project has been looking at the development of a 10 meter diameter fairing structure, similar in size to what will be required for a heavy launch vehicle. The development of new material systems requires the investigation of the material properties and the stress in the parts. Residual stress is an important factor to incorporate when modeling the stresses that a part is undergoing. Testing was performed to verify the stress free temperature with two-ply asymmetric panels. A comparison was done between three newly developed out of autoclave IM7 /Bismalieimide (BMI) systems. This paper presents the testing results and the analysis performed to determine the residual stress of the materials.

Stress Free Temperature Testing and Calculations on Out-of-Autoclave Composites

NASA Technical Reports Server (NTRS)

Cox, Sarah B.; Tate, LeNetra C.; Danley, Susan E.; Sampson, Jeffrey W.; Taylor, Brian J.; Sutter, James K.; Miller, Sandi G.

2013-01-01

Future launch vehicles will require the incorporation of large composite parts that will make up primary and secondary components of the vehicle. NASA has explored the feasibility of manufacturing these large components using Out-of-Autoclave impregnated carbon fiber composite systems through many composites development projects. Most recently, the Composites for Exploration Project has been looking at the development of a 10 meter diameter fairing structure, similar in size to what will be required for a heavy launch vehicle. The development of new material systems requires the investigation of the material properties and the stress in the parts. Residual stress is an important factor to incorporate when modeling the stresses that a part is undergoing. Testing was performed to verify the stress free temperature with two-ply asymmetric panels. A comparison was done between three newly developed out of autoclave IM7/Bismaleimide (BMI) systems. This paper presents the testing results and the analysis performed to determine the stress free temperature of the materials

Environmental effects on FOD resistance of composite fan blade

NASA Technical Reports Server (NTRS)

Murphy, G. C.; Selemme, C. T.

1981-01-01

The sensitivity of the impact characteristics of typical polymeric composite fan blade materials to potential limiting combinations of moisture, temperature level and temperature transients was established. The following four technical tasks are reported: (1) evaluation and characterization of constituent blade materials; (2) ballistic impact tests; (3) leading edge impact protection systems; and (4) simulated blade spin impact tests.

Evaluation of residual strength in the basalt fiber reinforced composites under impact damage

NASA Astrophysics Data System (ADS)

Kim, Yun-Hae; Lee, Jin-Woo; Moon, Kyung-Man; Yoon, Sung-Won; Baek, Tae-Sil; Hwang, Kwang-Il

2015-03-01

Composites are vulnerable to the impact damage by the collision as to the thickness direction, because composites are being manufactured by laminating the fiber. The understanding about the retained strength after the impact damage of the material is essential in order to secure the reliability of the structure design using the composites. In this paper, we have tried to evaluate the motion of the material according to the kinetic energy and potential energy and the retained strength after impact damage by testing the free fall test of the basalt fiber reinforced composite in the limelight as the environment friendly characteristic.

An in vitro evaluation of wear and surface roughness of particulate filler composite resin after tooth brushing.

PubMed

Al Khuraif, Abdul Aziz A

2014-11-01

To evaluate the influence of tooth brushing on wear and surface roughness of four different particulate filler composite resins. Six specimens (2 mm thick and 8 mm in diameter) of each tested material (Filtek Z250-Microhybrid, SpectrumTPH3-Submicron hybrid, Filtek Z350XT Nanofiller and Filtek P90- Microhybrid) were prepared according to the manufacturer's directions. A brushing sequence of 5000, 10,000 and 20,000 cycles was performed for all the samples. A non-contact profilometer was used to determine average surface roughness (Ra) and wear of the material assessed using an analytic electronic balance at baseline and each cycle interval. The data obtained were analyzed using one-way ANOVAs and post-hoc multiple comparison tests. Paired t-test was used for comparisons between cycle intervals for each material. Analyses with scanning electron microscopy (SEM) were also performed. The resin composite Filtek P 90 presented an increase in percentage weight loss after final toothbrushing cycles over the rest of the materials. Brushing significantly increased roughness (Ra) for all composites. Filtek Z250, after brushing, was significantly rougher than the other resins followed by Filtek P 90, Spectrum TPH 3 and Filtek Z350 XT. However, SEM images indicated severe change in surface topography of 'sub-micron hybrid' specimen compared to each other after tooth brushing. Wear and surface roughness increased with each cycle interval for all the materials and one composite resin demonstrated a higher increase in surface roughness than the other three tested brands of composite resins. Not much difference was observed in the weight loss between tested samples.

Processing and Characterization of Basalt Fiber Reinforced Ceramic Composites for High Temperature Applications Using Polymer Precursors

NASA Technical Reports Server (NTRS)

Cox, Sarah B.; Lui, Donovan; Gou, Jihua

2014-01-01

The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Ceramics can take much higher temperatures, but they are difficult to produce and form in bulk volumes. Polymer Derived Ceramics (PDCs) begin as a polymer matrix, allowing a shape to be formed and cured and then to be pyrolized in order to obtain a ceramic with the associated thermal and mechanical properties. The two PDCs used in this development are polysiloxane and polycarbosilane. Polysiloxanes contain a silicon oxycarbide backbone when pyrolized up to 1000C. Polycarbosilane, an organosilicon polymer, contain a silicon-carbon backbone; around 1200C, beta-SiC begins to crystallize. The use of basalt in structural and high temperature applications has been under development for over 50 years, yet there has been little published research on the incorporation of basalt fibers as a reinforcement in composites. Basalt is a naturally occurring material found in volcanic rock. Continuous basalt fiber reinforced PDCs have been fabricated and tested for the applicability of this composite system as a high temperature structural composite material. Thermal and mechanical testing includes oxyacetylene torch testing and three point bend testing.

Processing and Characterization of Basalt Fiber Reinforced Ceramic Composites for High Temperature Applications Using Polymer Precursors

NASA Technical Reports Server (NTRS)

Cox, Sarah B.; Lui, Donovan; Wang, Xin; Gou, Jihua

2014-01-01

The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Ceramics can take much higher temperatures, but they are difficult to produce and form in bulk volumes. Polymer Derived Ceramics (PDCs) begin as a polymer matrix, allowing a shape to be formed and cured and then to be pyrolized in order to obtain a ceramic with the associated thermal and mechanical properties. The two PDCs used in this development are polysiloxane and polycarbosilane. Polysiloxanes contain a silicon oxycarbide backbone when pyrolized up to 1000 deg C. Polycarbosilane, an organosilicon polymer, contain a silicon-carbon backbone; around 1200 deg C, Beta-SiC begins to crystallize. The use of basalt in structural and high temperature applications has been under development for over 50 years, yet there has been little published research on the incorporation of basalt fibers as a reinforcement in composites. Basalt is a naturally occurring material found in volcanic rock. Continuous basalt fiber reinforced PDCs have been fabricated and tested for the applicability of this composite system as a high temperature structural composite material. Thermal and mechanical testing includes oxyacetylene torch testing and three point bend testing.

Energy absorption in composite materials for crashworthy structures

NASA Technical Reports Server (NTRS)

Farley, Gary L.

1987-01-01

Crash energy-absorption processes in composite materials have been studied as part of a research program aimed at the development of energy absorbing subfloor beams for crashworthy military helicopters. Based on extensive tests on glass/epoxy, graphite/epoxy, and Kevlar/epoxy composites, it is shown that the energy-absorption characteristics and crushing modes of composite beams are similar to those exhibited by tubular specimens of similar material and architecture. The crushing mechanisms have been determined and related to the mechanical properties of the constituent materials and specimen architecture. A simple and accurate method for predicting the energy-absorption capability of composite beams has been developed.

Failure Study of Composite Materials by the Yeh-Stratton Criterion

NASA Technical Reports Server (NTRS)

Yeh, Hsien-Yang; Richards, W. Lance

1997-01-01

The newly developed Yeh-Stratton (Y-S) Strength Criterion was used to study the failure of composite materials with central holes and normal cracks. To evaluate the interaction parameters for the Y-S failure theory, it is necessary to perform several biaxial loading tests. However, it is indisputable that the inhomogeneous and anisotropic nature of composite materials have made their own contribution to the complication of the biaxial testing problem. To avoid the difficulties of performing many biaxial tests and still consider the effects of the interaction term in the Y-S Criterion, a simple modification of the Y-S Criterion was developed. The preliminary predictions by the modified Y-S Criterion were relatively conservative compared to the testing data. Thus, the modified Y-S Criterion could be used as a design tool. To further understand the composite failure problem, an investigation of the damage zone in front of the crack tip coupled with the Y-S Criterion is imperative.

Comparative study of the physical properties of core materials.

PubMed

Saygili, Gülbin; Mahmali, Sevil M

2002-08-01

This study was undertaken to measure physical properties of materials used for direct core buildups, including high-copper amalgam, visible light-cured resin composite, autocured titanium-containing composite, polyacid-modified composite, resin-modified glass-ionomer, and silver cermet cement. Compressive strength, diametral tensile strength, and flexural strength of six core materials of various material classes were measured for each material as a function of time up to 3 months at different storage conditions, using a standard specification test designed for the materials. Three different storage conditions (dry, humid, wet) at 37 degrees C were chosen. Materials were manipulated according to manufacturers' instructions for use as cores. Mean compressive, diametral tensile, and flexural strengths with associated standard deviations were calculated for each material. Multiple comparison and Newman-Keuls tests discerned many differences among materials. All materials were found to meet the minimum specification requirements, except in terms of flexural strength for amalgam after 1 hour and the silver cermet at all time intervals.

Test methods for textile composites

NASA Technical Reports Server (NTRS)

Minguet, Pierre J.; Fedro, Mark J.; Gunther, Christian K.

1994-01-01

Various test methods commonly used for measuring properties of tape laminate composites were evaluated to determine their suitability for the testing of textile composites. Three different types of textile composites were utilized in this investigation: two-dimensional (2-D) triaxial braids, stitched uniweave fabric, and three-dimensional (3-D) interlock woven fabric. Four 2-D braid architectures, five stitched laminates, and six 3-D woven architectures were tested. All preforms used AS4 fibers and were resin-transfer-molded with Shell RSL-1895 epoxy resin. Ten categories of material properties were investigated: tension, open-hole tension, compression, open-hole compression, in-plane shear, filled-hole tension, bolt bearing, interlaminar tension, interlaminar shear, and interlaminar fracture toughness. Different test methods and specimen sizes were considered for each category of test. Strength and stiffness properties obtained with each of these methods are documented in this report for all the material systems mentioned above.

Mechanical Properties of Calcium Fluoride-Based Composite Materials

PubMed Central

Kleczewska, Joanna; Pryliński, Mariusz; Podlewska, Magdalena; Sokołowski, Jerzy; Łapińska, Barbara

2016-01-01

Aim of the study was to evaluate mechanical properties of light-curing composite materials modified with the addition of calcium fluoride. The study used one experimental light-curing composite material (ECM) and one commercially available flowable light-curing composite material (FA) that were modified with 0.5–5.0 wt% anhydrous calcium fluoride. Morphology of the samples and uniformity of CaF2 distribution were analyzed using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Mechanical properties were tested after 24-hour storage of specimens in dry or wet conditions. Stored dry ECM enriched with 0.5–1.0 wt% CaF2 showed higher tensile strength values, while water storage of all modified ECM specimens decreased their tensile strength. The highest Vickers hardness tested after dry storage was observed for 2.5 wt% CaF2 content in ECM. The addition of 2.0–5.0 wt% CaF2 to FA caused significant decrease in tensile strength after dry storage and overall tensile strength decrease of modified FA specimens after water storage. The content of 2.0 wt% CaF2 in FA resulted in the highest Vickers hardness tested after wet storage. Commercially available composite material (FA), unmodified with fluoride addition, demonstrated overall significantly higher mechanical properties. PMID:28004001

Evaluating Composite Sampling Methods of Bacillus Spores at Low Concentrations

PubMed Central

Hess, Becky M.; Amidan, Brett G.; Anderson, Kevin K.; Hutchison, Janine R.

2016-01-01

Restoring all facility operations after the 2001 Amerithrax attacks took years to complete, highlighting the need to reduce remediation time. Some of the most time intensive tasks were environmental sampling and sample analyses. Composite sampling allows disparate samples to be combined, with only a single analysis needed, making it a promising method to reduce response times. We developed a statistical experimental design to test three different composite sampling methods: 1) single medium single pass composite (SM-SPC): a single cellulose sponge samples multiple coupons with a single pass across each coupon; 2) single medium multi-pass composite: a single cellulose sponge samples multiple coupons with multiple passes across each coupon (SM-MPC); and 3) multi-medium post-sample composite (MM-MPC): a single cellulose sponge samples a single surface, and then multiple sponges are combined during sample extraction. Five spore concentrations of Bacillus atrophaeus Nakamura spores were tested; concentrations ranged from 5 to 100 CFU/coupon (0.00775 to 0.155 CFU/cm2). Study variables included four clean surface materials (stainless steel, vinyl tile, ceramic tile, and painted dry wallboard) and three grime coated/dirty materials (stainless steel, vinyl tile, and ceramic tile). Analysis of variance for the clean study showed two significant factors: composite method (p< 0.0001) and coupon material (p = 0.0006). Recovery efficiency (RE) was higher overall using the MM-MPC method compared to the SM-SPC and SM-MPC methods. RE with the MM-MPC method for concentrations tested (10 to 100 CFU/coupon) was similar for ceramic tile, dry wall, and stainless steel for clean materials. RE was lowest for vinyl tile with both composite methods. Statistical tests for the dirty study showed RE was significantly higher for vinyl and stainless steel materials, but lower for ceramic tile. These results suggest post-sample compositing can be used to reduce sample analysis time when responding to a Bacillus anthracis contamination event of clean or dirty surfaces. PMID:27736999

Evaluating Composite Sampling Methods of Bacillus Spores at Low Concentrations.

PubMed

Hess, Becky M; Amidan, Brett G; Anderson, Kevin K; Hutchison, Janine R

2016-01-01

Restoring all facility operations after the 2001 Amerithrax attacks took years to complete, highlighting the need to reduce remediation time. Some of the most time intensive tasks were environmental sampling and sample analyses. Composite sampling allows disparate samples to be combined, with only a single analysis needed, making it a promising method to reduce response times. We developed a statistical experimental design to test three different composite sampling methods: 1) single medium single pass composite (SM-SPC): a single cellulose sponge samples multiple coupons with a single pass across each coupon; 2) single medium multi-pass composite: a single cellulose sponge samples multiple coupons with multiple passes across each coupon (SM-MPC); and 3) multi-medium post-sample composite (MM-MPC): a single cellulose sponge samples a single surface, and then multiple sponges are combined during sample extraction. Five spore concentrations of Bacillus atrophaeus Nakamura spores were tested; concentrations ranged from 5 to 100 CFU/coupon (0.00775 to 0.155 CFU/cm2). Study variables included four clean surface materials (stainless steel, vinyl tile, ceramic tile, and painted dry wallboard) and three grime coated/dirty materials (stainless steel, vinyl tile, and ceramic tile). Analysis of variance for the clean study showed two significant factors: composite method (p< 0.0001) and coupon material (p = 0.0006). Recovery efficiency (RE) was higher overall using the MM-MPC method compared to the SM-SPC and SM-MPC methods. RE with the MM-MPC method for concentrations tested (10 to 100 CFU/coupon) was similar for ceramic tile, dry wall, and stainless steel for clean materials. RE was lowest for vinyl tile with both composite methods. Statistical tests for the dirty study showed RE was significantly higher for vinyl and stainless steel materials, but lower for ceramic tile. These results suggest post-sample compositing can be used to reduce sample analysis time when responding to a Bacillus anthracis contamination event of clean or dirty surfaces.

Development of a beam builder for automatic fabrication of large composite space structures

NASA Technical Reports Server (NTRS)

Bodle, J. G.

1979-01-01

The composite material beam builder which will produce triangular beams from pre-consolidated graphite/glass/thermoplastic composite material through automated mechanical processes is presented, side member storage, feed and positioning, ultrasonic welding, and beam cutoff are formed. Each process lends itself to modular subsystem development. Initial development is concentrated on the key processes for roll forming and ultrasonic welding composite thermoplastic materials. The construction and test of an experimental roll forming machine and ultrasonic welding process control techniques are described.

Evaluation of CVI SiC/SiC Composites for High Temperature Applications

NASA Technical Reports Server (NTRS)

Kiser, D.; Almansour, A.; Smith, C.; Gorican, D.; Phillips, R.; Bhatt, R.; McCue, T.

2017-01-01

Silicon carbide fiber reinforced silicon carbide (SiC/SiC) composites are candidate materials for various high temperature turbine engine applications because of their high specific strength and good creep resistance at temperatures of 1400 C (2552 F) and higher. Chemical vapor infiltration (CVI) SiC/SiC ceramic matrix composites (CMC) incorporating Sylramic-iBN SiC fiber were evaluated via fast fracture tensile tests (acoustic emission damage characterization to assess cracking behavior), tensile creep testing, and microscopy. The results of this testing and observed material behavior degradation mechanisms are reviewed.

Evaluation and prediction of long-term environmental effects of nonmetallic materials

NASA Technical Reports Server (NTRS)

Papazian, H.

1985-01-01

The properties of a number of nonmetallic materials were evaluated experimentally in simulated space environments in order to develop models for accelerated test methods useful for predicting such behavioral changes. Graphite-epoxy composites were exposed to thermal cycling. Adhesive foam tapes were subjected to a vacuum environment. Metal-matrix composites were tested for baseline data. Predictive modeling designed to include strength and aging effects on composites, polymeric films, and metals under such space conditions (including the atomic oxygen environment) is discussed. The Korel 8031-00 high strength adhesive foam tape was shown to be superior to the other two tested.

Process Optimization of Bismaleimide (BMI) Resin Infused Carbon Fiber Composite

NASA Technical Reports Server (NTRS)

Ehrlich, Joshua W.; Tate, LaNetra C.; Cox, Sarah B.; Taylor, Brian J.; Wright, M. Clara; Faughnan, Patrick D.; Batterson, Lawrence M.; Caraccio, Anne J.; Sampson, Jeffery W.

2013-01-01

Engineers today are presented with the opportunity to design and build the next generation of space vehicles out of the lightest, strongest, and most durable materials available. Composites offer excellent structural characteristics and outstanding reliability in many forms that will be utilized in future aerospace applications including the Commercial Crew and Cargo Program and the Orion space capsule. NASA's Composites for Exploration (CoEx) project researches the various methods of manufacturing composite materials of different fiber characteristics while using proven infusion methods of different resin compositions. Development and testing on these different material combinations will provide engineers the opportunity to produce optimal material compounds for multidisciplinary applications. Through the CoEx project, engineers pursue the opportunity to research and develop repair patch procedures for damaged spacecraft. Working in conjunction with Raptor Resins Inc., NASA engineers are utilizing high flow liquid infusion molding practices to manufacture high-temperature composite parts comprised of intermediate modulus 7 (IM7) carbon fiber material. IM7 is a continuous, high-tensile strength composite with outstanding structural qualities such as high shear strength, tensile strength and modulus as well as excellent corrosion, creep, and fatigue resistance. IM7 carbon fiber, combined with existing thermoset and thermoplastic resin systems, can provide improvements in material strength reinforcement and deformation-resistant properties for high-temperature applications. Void analysis of the different layups of the IM7 material discovered the largest total void composition within the [ +45 , 90 , 90 , -45 ] composite panel. Tensile and compressional testing proved the highest mechanical strength was found in the [0 4] layup. This paper further investigates the infusion procedure of a low-cost/high-performance BMI resin into an IM7 carbon fiber material and the optical, chemical, and mechanical analyses performed.

Time-frequency analysis of acoustic emission signals generated by the Glass Fibre Reinforced Polymer Composites during the tensile test

NASA Astrophysics Data System (ADS)

Świt, G.; Adamczak, A.; Krampikowska, A.

2017-10-01

Fibre reinforced polymer composites are currently dominating in the composite materials market. The lack of detailed knowledge about their properties and behaviour in various conditions of exposure under load significantly limits the broad possibilities of application of these materials. Occurring and accumulation of defects in material during the exploitation of the construction lead to the changes of its technical condition. The necessity to control the condition of the composite is therefore justified. For this purpose, non-destructive method of acoustic emission can be applied. This article presents an example of application of acoustic emission method based on time analysis and time-frequency analysis for the evaluation of the progress of the destructive processes and the level of degradation of glass fibre reinforced composite tapes that were subject to tensile testing.

Materials research for high-speed civil transport and generic hypersonics: Composites durability

NASA Technical Reports Server (NTRS)

Allen-Lilly, Heather; Cregger, Eric; Hoffman, Daniel; Mccool, Jim

1995-01-01

This report covers a portion of an ongoing investigation of the durability of composites for the High Speed Civil Transport (HSCT) program. Candidate HSCT composites need to possess the high-temperature capability required for supersonic flight. This program was designed to initiate the design, analysis, fabrication, and testing of equipment intended for use in validating the long-term durability of materials for the HSCT. This equipment includes thermally actuated compression and tension fixtures, hydraulic-actuated reversible load fixtures, and thermal chambers. This equipment can be used for the durability evaluation of both composite and adhesive materials. Thermally actuated fixtures are recommended for fatigue cycling when long-term thermomechanical fatigue (TMF) data are required on coupon-sized tension or compression specimens. Long term durability testing plans for polymer matrix composite specimens are included.

Effects of air-polishing powders on color stability of composite resins.

PubMed

Güler, Ahmet Umut; Duran, Ibrahim; Yücel, Ali Çağin; Ozkan, Pelin

2011-10-01

The purpose of this study was to investigate the effect of different air-polishing powders on the color stability of different types of composite resin restorative materials. Thirty cylindrical specimens (15×2 mm) were prepared for each of 7 composite resin restorative materials. All specimens were polished with a series of aluminum oxide polishing discs (Sof-Lex). The prepared specimens of each composite resin were randomly divided into 3 groups of 10 specimens each, for control (Group-C) and two air-powder applications (Group-CP: Cavitron Prophy-Jet; Group-PS: Sirona ProSmile prophylaxis powder). A standard air-polishing unit (ProSmile Handly) was used. All specimens were air-powdered for 10 s at 4-bar pressure. The distance of the spray nosel from the specimens was approximately 10 mm and angulation of the nosel was 90°. Specimens were stored in 100 mL of coffee (Nescafe Classic) for 24 h at 37°C. Color measurement of all specimens was recorded before and after exposure to staining agent with a colorimeter (Minolta CR-300). Color differences (∆E*) between the 2 color measurements (baseline and after 24 h storage) were calculated. The data were analyzed with a 2-way ANOVA test, and mean values were compared by the Tukey HSD test (p<0.05). According to the 2-way ANOVA results, composite resin restorative materials, air-polishing powders, and their interaction were statistically significant (p<0.05) For Aelite Aesthetic Enemal, Filtek Z250, Grandio, CeramX Mono, and Quixfil composite resin restorative materials, no significant difference was observed between Group-PS and Group-CP (p>.05) and these groups demonstrated the highest ∆E* values. For Filtek Silorane and IntenS, the highest ∆E* values were observed in Group-PS. The lowest ∆E* values for all composite resin groups were observed in Group-C. When comparing the 7 composite resin restorative materials, Aelite Aesthetic Enemal demonstrated significantly less ∆E* values than the other composite resins tested. The highest ∆E* values were observed in Quixfil. Except for Quixfil, all control groups of composite resins that were polished Sof-Lex exhibited clinically acceptable ∆E values (<3.7). Air-polishing applications increased the color change for all composite resin restorative materials tested. Composite restorations may require re-polishing after air-polishing.

Improvement of acoustical characteristics : wideband bamboo based polymer composite

NASA Astrophysics Data System (ADS)

Farid, M.; Purniawan, A.; Rasyida, A.; Ramadhani, M.; Komariyah, S.

2017-07-01

Environmental friendly and comfortable materials are desirable for applications in the automobile interior. The objective of this research was to examine and develop bamboo based polymer composites applied to the sound absorption materials of automobile door panels. Morphological analysis of the polyurethane/bamboo powder composite materials was carried out using scanning electron microscope to reveal the microscopic material behavior and followed by the FTIR and TGA testing. The finding demonstrated that this acoustical polymer composite materials provided a potential wideband sound absorption material. The range of frequency can be controlled between 500 and 4000 Hz with an average of sound absorption coefficient around 0.411 and it met to the door panels criteria.

Diametral and compressive strength of dental core materials.

PubMed

Cho, G C; Kaneko, L M; Donovan, T E; White, S N

1999-09-01

Strength greatly influences the selection of core materials. Many disparate material types are now recommended for use as cores. Cores must withstand forces due to mastication and parafunction for many years. This study compared the compressive and diametral tensile strengths of 8 core materials of various material classes and formulations (light-cured hybrid composite, autocured titanium containing composite, amalgam, glass ionomer, glass ionomer cermet, resin-modified glass ionomer, and polyurethane). Materials were manipulated according to manufacturers' instructions for use as cores. Mean compressive and diametral strengths with associated standard errors were calculated for each material (n = 10). Analyses of variance were computed (P <.0001) and multiple comparisons tests discerned many differences among materials. Compressive strengths varied widely from 61.1 MPa for a polyurethane to 250 MPa for a resin composite. Diametral tensile strengths ranged widely from 18.3 MPa for a glass ionomer cermet to 55.1 MPa for a resin composite. Some resin composites had compressive and tensile strengths equal to those of amalgam. Light-cured hybrid resin composites were stronger than autocured titanium containing composites. The strengths of glass ionomer-based materials and of a polyurethane material were considerably lower than for resin composites or amalgam.

Full-field Strain Methods for Investigating Failure Mechanisms in Triaxial Braided Composites

NASA Technical Reports Server (NTRS)

Littell, Justin D.; Binienda, Wieslaw K.; Goldberg, Robert K.; Roberts, Gary D.

2008-01-01

Composite materials made with triaxial braid architecture and large tow size carbon fibers are beginning to be used in many applications, including composite aircraft and engine structures. Recent advancements in braiding technology have led to commercially viable manufacturing approaches for making large structures with complex shape. Although the large unit cell size of these materials is an advantage for manufacturing efficiency, the fiber architecture presents some challenges for materials characterization, design, and analysis. In some cases, the static load capability of structures made using these materials has been higher than expected based on material strength properties measured using standard coupon tests. A potential problem with using standard tests methods for these materials is that the unit cell size can be an unacceptably large fraction of the specimen dimensions. More detailed investigation of deformation and failure processes in large unit cell size triaxial braid composites is needed to evaluate the applicability of standard test methods for these materials and to develop alternative testing approaches. In recent years, commercial equipment has become available that enables digital image correlation to be used on a more routine basis for investigation of full field 3D deformation in materials and structures. In this paper, some new techniques that have been developed to investigate local deformation and failure using digital image correlation techniques are presented. The methods were used to measure both local and global strains during standard straight-sided coupon tensile tests on composite materials made with 12 and 24 k yarns and a 0/+60/-60 triaxial braid architecture. Local deformation and failure within fiber bundles was observed, and this local failure had a significant effect on global stiffness and strength. The matrix material had a large effect on local damage initiation for the two matrix materials used in this investigation. Premature failure in regions of the unit cell near the edge of the straight-sided specimens was observed for transverse tensile tests in which the braid axial fibers were perpendicular to the specimen axis and the bias fibers terminated on the cut edges in the specimen gage section. This edge effect is one factor that could contribute to a measured strength that is lower than the actual material strength in a structure without edge effects.

Characterizing the Response of Composite Panels to a Pyroshock Induced Environment Using Design of Experiments Methodology

NASA Technical Reports Server (NTRS)

Parsons, David S.; Ordway, David; Johnson, Kenneth

2013-01-01

This experimental study seeks to quantify the impact various composite parameters have on the structural response of a composite structure in a pyroshock environment. The prediction of an aerospace structure's response to pyroshock induced loading is largely dependent on empirical databases created from collections of development and flight test data. While there is significant structural response data due to pyroshock induced loading for metallic structures, there is much less data available for composite structures. One challenge of developing a composite pyroshock response database as well as empirical prediction methods for composite structures is the large number of parameters associated with composite materials. This experimental study uses data from a test series planned using design of experiments (DOE) methods. Statistical analysis methods are then used to identify which composite material parameters most greatly influence a flat composite panel's structural response to pyroshock induced loading. The parameters considered are panel thickness, type of ply, ply orientation, and pyroshock level induced into the panel. The results of this test will aid in future large scale testing by eliminating insignificant parameters as well as aid in the development of empirical scaling methods for composite structures' response to pyroshock induced loading.

Characterizing the Response of Composite Panels to a Pyroshock Induced Environment using Design of Experiments Methodology

NASA Technical Reports Server (NTRS)

Parsons, David S.; Ordway, David O.; Johnson, Kenneth L.

2013-01-01

This experimental study seeks to quantify the impact various composite parameters have on the structural response of a composite structure in a pyroshock environment. The prediction of an aerospace structure's response to pyroshock induced loading is largely dependent on empirical databases created from collections of development and flight test data. While there is significant structural response data due to pyroshock induced loading for metallic structures, there is much less data available for composite structures. One challenge of developing a composite pyroshock response database as well as empirical prediction methods for composite structures is the large number of parameters associated with composite materials. This experimental study uses data from a test series planned using design of experiments (DOE) methods. Statistical analysis methods are then used to identify which composite material parameters most greatly influence a flat composite panel's structural response to pyroshock induced loading. The parameters considered are panel thickness, type of ply, ply orientation, and pyroshock level induced into the panel. The results of this test will aid in future large scale testing by eliminating insignificant parameters as well as aid in the development of empirical scaling methods for composite structures' response to pyroshock induced loading.

Analysis of Graphite-Reinforced Cementitious Composites

NASA Technical Reports Server (NTRS)

Vaughan, R. E.

2002-01-01

Strategically embedding graphite meshes in a compliant cementitious matrix produces a composite material with relatively high tension and compressive properties as compared to steel-reinforced structures fabricated from a standard concrete mix. Although these composite systems are somewhat similar, the methods used to analyze steel-reinforced composites often fail to characterize the behavior of their more advanced graphite-reinforced counterparts. This Technical Memorandum describes some of the analytical methods being developed to determine the deflections and stresses in graphite-reinforced cementitious composites. It is initially demonstrated that the standard transform section method fails to provide accurate results when the elastic moduli ratio exceeds 20. An alternate approach is formulated by using the rule of mixtures to determine a set of effective material properties for the composite. Tensile tests are conducted on composite samples to verify this approach. When the effective material properties are used to characterize the deflections of composite beams subjected to pure bending, an excellent agreement is obtained. Laminated composite plate theory is investigated as a means for analyzing even more complex composites, consisting of multiple graphite layers oriented in different directions. In this case, composite beams are analyzed using the laminated composite plate theory with material properties established from tensile tests. Then, finite element modeling is used to verify the results. Considering the complexity of the samples, a very good agreement is obtained.

Measurement of mechanical and thermophysical properties of dimensionally stable materials for space applications

NASA Technical Reports Server (NTRS)

Rawal, Suraj P.; Misra, Mohan S.

1992-01-01

Mechanical, thermal, and physical property test data was generated for as-fabricated advanced composite materials at room temperature (RT), -150 and 250 F. The results are documented of mechanical and thermophysical property tests of IM7/PEEK and discontinuous SiC/Al (particulate (p) and whisker (w) reinforced) composites which were tested at three different temperatures to determine the effect of temperature on material properties. The specific material systems tested were IM7/PEEK (0)8, (0, + or - 45, 90)s, (+ or - 30, 04)s, 25 vol. pct. (v/o) SiCp/Al, and 25 v/o SiCw/Al. RT material property results of IM7/PEEK were in good agreement with the predicted values, providing a measure of consolidation integrity attained during fabrication. Results of mechanical property tests indicated that modulus values at each test temperature were identical, whereas the strength (e.g., tensile, compressive, flexural, and shear) values were the same at -150 F, and RT, and gradually decreased as the test temperature was increased to 250 F. Similar trends in the strength values was also observed in discontinuous SiC/Al composites. These results indicate that the effect of temperature was more pronounced on the strength values than modulus values.

Composite Overwrapped Pressure Vessels (COPV) Materials Aging Issues

NASA Technical Reports Server (NTRS)

2010-01-01

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

Development of Design Analysis Methods for C/SiC Composite Structures

NASA Technical Reports Server (NTRS)

Sullivan, Roy M.; Mital, Subodh K.; Murthy, Pappu L. N.; Palko, Joseph L.; Cueno, Jacques C.; Koenig, John R.

2006-01-01

The stress-strain behavior at room temperature and at 1100 C (2000 F) was measured for two carbon-fiber-reinforced silicon carbide (C/SiC) composite materials: a two-dimensional plain-weave quasi-isotropic laminate and a three-dimensional angle-interlock woven composite. Micromechanics-based material models were developed for predicting the response properties of these two materials. The micromechanics based material models were calibrated by correlating the predicted material property values with the measured values. Four-point beam bending sub-element specimens were fabricated with these two fiber architectures and four-point bending tests were performed at room temperature and at 1100 C. Displacements and strains were measured at various locations along the beam and recorded as a function of load magnitude. The calibrated material models were used in concert with a nonlinear finite element solution to simulate the structural response of these two materials in the four-point beam bending tests. The structural response predicted by the nonlinear analysis method compares favorably with the measured response for both materials and for both test temperatures. Results show that the material models scale up fairly well from coupon to subcomponent level.

Wavelet Analysis of Acoustic Emissions during Tensile Test of Carbon Fibre Reinforced Polymer Composites

NASA Astrophysics Data System (ADS)

Świt, Grzegorz; Adamczak, Anna; Krampikowska, Aleksandra

2017-10-01

The increase of the interest in polymer composites in technology and in people’s everyday lives has been noticed in the recent years. Producing new materials with polymer matrix of particular properties that cannot be achieved by traditional construction materials contributed to high interest in fibre composite materials. However, a wider use of these materials is limited because of the lack of detailed knowledge about their properties and behaviour in various conditions of exposure under load. Mechanical degradation of polymer composites, which is caused by prolonged permanent loads, is connected with the changes of the material structure that are local or that include the whole volume of the element’s body. These changes are in the form of various types of discontinuity, including: deboning, matrix and fibers cracks and delamination. The article presents the example of the application of acoustic emission method based on the analysis of the waves through the use of wavelet analysis for the evaluation of the progress of the destructive processes and the level of the degradation of composite tapes that were subject to tensile testing.

Fatigue damage characterization of braided and woven fiber reinforced polymer matrix composites at room and elevated temperatures

NASA Astrophysics Data System (ADS)

Montesano, John

The use of polymer matrix composites (PMC) for manufacturing primary load-bearing structural components has significantly increased in many industrial applications. Specifically in the aerospace industry, PMCs are also being considered for elevated temperature applications. Current aerospace-grade composite components subjected to fatigue loading are over-designed due to insufficient understanding of the material failure processes, and due to the lack of available generic fatigue prediction models. A comprehensive literature survey reveals that there are few fatigue studies conducted on woven and braided fabric reinforced PMC materials, and even fewer at elevated temperatures. It is therefore the objective of this study to characterize and subsequently model the elevated temperature fatigue behaviour of a triaxial braided PMC, and to investigate the elevated temperature fatigue properties of two additional woven PMCs. An extensive experimental program is conducted using a unique test protocol on the braided and woven composites, which consists of static and fatigue testing at various test temperatures. The development of mechanically-induced damage is monitored using a combination of non-destructive techniques which included infrared thermography, fiber optic sensors and edge replication. The observed microscopic damage development is quantified and correlated to the exhibited macroscopic material behaviour at all test temperatures. The fiber-dominated PMC materials considered in this study did not exhibit notable time- or temperature-dependent static properties. However, fatigue tests reveal that the local damage development is in fact notably influenced by temperature. The elevated temperature environment increases the toughness of the thermosetting polymers, which results in consistently slower fatigue crack propagation rates for the respective composite materials. This has a direct impact on the stiffness degradation rate and the fatigue lives for the braided and woven composites under investigation. The developed analytical fatigue damage prediction model, which is based on actual observed damage mechanisms, accurately predicted the development of damage and the corresponding stiffness degradation for the braided PMC, for all test temperatures. An excellent correlation was found between the experimental and the predicted results to within a 2% accuracy. The prediction model adequately captured the local temperature-induced phenomenon exhibited by the braided PMC material. The results presented in this study are novel for a braided composite material subjected to elevated temperature fatigue.

Investigation of a Macromechanical Approach to Analyzing Triaxially-Braided Polymer Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Blinzler, Brina J.; Binienda, Wieslaw K.

2010-01-01

A macro level finite element-based model has been developed to simulate the mechanical and impact response of triaxially-braided polymer matrix composites. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. The commercial transient dynamic finite element code LS-DYNA is used to conduct the simulations, and a continuum damage mechanics model internal to LS-DYNA is used as the material constitutive model. The material stiffness and strength values required for the constitutive model are determined based on coupon level tests on the braided composite. Simulations of quasi-static coupon tests of a representative braided composite are conducted. Varying the strength values that are input to the material model is found to have a significant influence on the effective material response predicted by the finite element analysis, sometimes in ways that at first glance appear non-intuitive. A parametric study involving the input strength parameters provides guidance on how the analysis model can be improved.

Development of constitutive model for composites exhibiting time dependent properties

NASA Astrophysics Data System (ADS)

Pupure, L.; Joffe, R.; Varna, J.; Nyström, B.

2013-12-01

Regenerated cellulose fibres and their composites exhibit highly nonlinear behaviour. The mechanical response of these materials can be successfully described by the model developed by Schapery for time-dependent materials. However, this model requires input parameters that are experimentally determined via large number of time-consuming tests on the studied composite material. If, for example, the volume fraction of fibres is changed we have a different material and new series of experiments on this new material are required. Therefore the ultimate objective of our studies is to develop model which determines the composite behaviour based on behaviour of constituents of the composite. This paper gives an overview of problems and difficulties, associated with development, implementation and verification of such model.

USSR and Eastern Europe Scientific Abstracts, Materials Science and Metallurgy, Number 56.

DTIC Science & Technology

1978-10-05

metals and materials, coatings, composites , metal corrosion, extraction and refining, forming, instrumentation, lubricants, mechanical and physical...Aluminum and Its Alloys 1 Analysis and Testing 5 Beryllium • > • 1 Coatings • 8 Composite Materials 9 Conferences • 15 Corrosion 18 Graphite...alloys, consisting in changing the chemi- cal composition of the surface layer, which plays an important role in corrosion processes. The content of

Effect of Ingested Liquids on Color Change of Composite Resins.

PubMed

Malek Afzali, Beheshteh; Ghasemi, Amir; Mirani, Asrin; Abdolazimi, Zahra; Akbarzade Baghban, Alireza; Kharazifard, Mohammad Javad

2015-08-01

Color change of composite restorations is well known to dentists. However, the effect of commonly consumed drinks on discoloration of composite resins has yet to be determined. This study sought to assess the color change of a nanofilled (Premise) and a flowable composite resin (Premise flowable) following simulated consumption of tea, cola, iron drops and multivitamin syrup. Forty disk-shaped specimens (7 mm in diameter and 2 mm thick) were fabricated from each composite resin. The baseline color values were measured according to the CIE L*a*b* system using digital imaging. The specimens of each restorative material were randomly divided into five groups (eight each) according to the storage media namely tea, cola, iron drops, multivitamin syrup or distilled water (control). The specimens were immersed in staining solutions for three hours daily over a 40-day test period. Following this, the color change values (ΔE*) were calculated. For statistical analyses, the color differences were analyzed using two-way ANOVA and Tukey's test (P< 0.05). There was no significant difference in ΔE* values between the two types of composite resins (P>0.05). In both composite materials, the difference among the solutions was not significant (P>0.05). Under the tested experimental conditions, both restorative materials were susceptible to discoloration by all four staining solutions. The color change values were not related to the solution or the type of material used.

46 CFR 164.009-21 - Laboratory report.

Code of Federal Regulations, 2010 CFR

2010-10-01

...) Description of the specimens tested if the specimens are prepared from composite material. (i) If the test was... Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL MATERIALS Noncombustible Materials for Merchant Vessels § 164.009-21 Laboratory...

Environmental exposure effects on composite materials for commercial aircraft

NASA Technical Reports Server (NTRS)

Gibbons, M. N.

1982-01-01

The data base for composite materials' properties as they are affected by the environments encountered in operating conditions, both in flight and at ground terminals is expanded. Absorbed moisture degrades the mechanical properties of graphite/epoxy laminates at elevated temperatures. Since airplane components are frequently exposed to atmospheric moisture, rain, and accumulated water, quantitative data are required to evaluate the amount of fluids absorbed under various environmental conditions and the subsequent effects on material properties. In addition, accelerated laboratory test techniques are developed are reliably capable of predicting long term behavior. An accelerated environmental exposure testing procedure is developed, and experimental results are correlated and compared with analytical results to establish the level of confidence for predicting composite material properties.

Power losses of soft magnetic composite materials under two-dimensional excitation

NASA Astrophysics Data System (ADS)

Zhu, J. G.; Zhong, J. J.; Ramsden, V. S.; Guo, Y. G.

1999-04-01

Soft magnetic composite materials produced by powder metallurgy techniques can be very useful for construction of low cost small motors. However, the rotational core losses and the corresponding B-H relationships of soft magnetic composite materials with two-dimensional rotating fluxes have neither been supplied by the manufacturers nor reported in the literature. This article reports the core loss measurement of a soft magnetic composite material, SOMALOY™ 500, Höganäs AB, Sweden, under two-dimensional excitations. The principle of measurement, testing system, and power loss calculation are presented. The results are analyzed and discussed.

Color change of CAD-CAM materials and composite resin cements after thermocycling.

PubMed

Gürdal, Isil; Atay, Ayse; Eichberger, Marlis; Cal, Ebru; Üsümez, Aslihan; Stawarczyk, Bogna

2018-04-24

The color of resin cements and computer-aided-design and computer-aided-manufacturing (CAD-CAM) restorations may change with aging. The purpose of this in vitro study was to analyze the influence of thermocycling on the color of CAD-CAM materials with underlying resin cement. Seven different CAD-CAM materials, composite resins and glass-ceramics were cut into 0.7-mm and 1.2-mm thicknesses (n=10) and cemented with a dual-polymerizing resin cement, a light-polymerizing resin cement, and a preheated composite resin (N=420). Color values were measured by using spectrophotometry. Specimens were subjected to thermocycling (5°C and 55°C; 5000 cycles). The measured color difference (ΔE) data were analyzed by using descriptive statistics. Normality of data distribution was tested by using the Kolmogorov-Smirnov test. Three-way and 1-way ANOVA followed by the Scheffé post-hoc test and unpaired 2-sample Student t test were computed to determine the significant differences among the tested parameters (α=.05). ΔE values were significantly influenced by the CAD-CAM material (η p 2 =0.85, P<.001) and the resin composite cement (η P 2 =0.03, P=.003) but were not influenced by thickness (P=.179). Significant interactions were present among thickness, cement, and CAD-CAM materials (P<.001). Vita Suprinity and GC Cerasmart showed significantly the lowest ΔE values (P<.001). The highest ΔE values were observed for IPS Empress CAD. The dual-polymerizing resin cement showed significantly lower ΔE values than the preheated composite resin (P=.003). Restoration materials and composite resin cement types used for cementation influence the amount of color change due to aging. Copyright © 2018 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Impact Testing and Analysis of Composites for Aircraft Engine Fan Cases

NASA Technical Reports Server (NTRS)

Roberts, Gary D.; Revilock, Duane M.; Binienda, Wieslaw K.; Nie, Walter Z.; Mackenzie, S. Ben; Todd, Kevin B.

2002-01-01

The fan case in a jet engine is a heavy structure because of its size and because of the requirement that it contain a blade released during engine operation. Composite materials offer the potential for reducing the weight of the case. Efficient design, test, and analysis methods are needed to efficiently evaluate the large number of potential composite materials and design concepts. The type of damage expected in a composite case under blade-out conditions was evaluated using a subscale test in which a glass/epoxy composite half-ring target was impacted with a wedge-shaped titanium projectile. Fiber shearing occurred near points of contact between the projectile and target. Delamination and tearing occurred on a larger scale. These damage modes were reproduced in a simpler test in which flat glass/epoxy composites were impacted with a blunt cylindrical projectile. A surface layer of ceramic eliminated fiber shear fracture but did not reduce delamination. Tests on 3D woven carbon/epoxy composites indicated that transverse reinforcement is effective in reducing delamination. A 91 cm (36 in.) diameter full-ring sub-component was proposed for larger scale testing of these and other composite concepts. Explicit, transient, finite element analyses indicated that a full-ring test is needed to simulate complete impact dynamics, but simpler tests using smaller ring sections are adequate when evaluation of initial impact damage is the primary concern.

High Temperature Properties of an Alumina Enhanced Thermal Barrier

NASA Technical Reports Server (NTRS)

Leiser, Daniel B.; Smith, Marnell; Keating, Elizabeth A.

1987-01-01

The heatshield material requirements for future space vehicles (Aerobraking Orbital Transfer Vehicle & National Aerospace Plane) will depend upon the desired flight capability, configuration and location on the vehicle. These requirements will be more demanding and different from those derived for the materials used in the Shuttle Orbiter thermal protection system. Research was therefore initiated into improving the thermal efficiency of this class of materials by first characterizing their thermal and structural capabilities. Alternate material systems have been developed, tested, and compared with the baseline Shuttle system. This research resulted in the development of several very low density, high porosity (80-90%) materials with enhanced durability and temperature capability. One of the developments was a family of materials referred to as Fibrous Refractory Composite Insulation (FRCI) utilizing a mixture of fibers, each serving a unique purpose. One composition of the FRCI family with two fibers was adopted as a baseline material for use on the third and fourth Orbiters in selected areas due to its strength at a lower density compared to earlier materials. A further improvement in the FRCI family of materials is the Alumina Enhanced Thermal Barrier (AETB), a three-fiber composite. It has a higher temperature capability (composition dependent) than the baseline FRCI as proven by convective heating tests of one composition. AETB was studied to better characterize its performance at high temperature and the mechanisms by which its properties change. In conclusion, the shrinkage of AETB is a factor of six better than baseline FRCI at 1260 C (2300 F) with about a 20% improvement in mechanical properties. This improvement could translate into a 110 C (200 F) higher temperature capability in use as a heat shield material, but further testing in a convective heating environment is required to determine the actual improvement attainable.

Flammability of self-extinguishing kenaf/ABS nanoclays composite for aircraft secondary structure

NASA Astrophysics Data System (ADS)

Karunakaran, S.; Majid, D. L.; Mohd Tawil, M. L.

2016-10-01

This study investigates the flammability properties of kenaf fiber reinforced acrylonitrile butadiene styrene (ABS) with nanoclays composites. Natural fiber is one of the potential materials to be used with thermoplastic as a composite due to its attractive properties such as lightweight and strong. In this paper, flammability properties of this material are evaluated through Underwriters Laboratory 94 Horizontal Burning (UL94 HB), which has been conducted for both controlled and uncontrolled conditions, smoke density and limiting oxygen index tests (LOI). These flammability tests are in compliance with the Federal Aviation Regulation (FAR) requirement. The results from UL94 HB and smoke density tests show that the presence of nanoclays with effective composition of kenaf fiber reinforced ABS has enhanced the burning characteristics of the material by hindering propagation of flame spread over the surface of the material through char formation. Consequently, this decreases the burning rate and produces low amount of smoke during burning. On contrary, through LOI test, this material requires less oxygen to burn when exposed to fire, which hinders the enhancement of burning characteristics. This is due to burning mechanism exhibited by nanoclays that catalyzes barrier formation and flame propagation rate over the surface of the biocomposite material. Overall, these experimental results suggest that this biocomposite material is capable of self-extinguishing and possesses effective fire extinction. The observed novel synergism from the result obtained is promising to be implemented in secondary structures of aircraft with significant benefits such as cost-effective, lightweight and biodegradable self-extinguishing biocomposite.

Damage Simulation in Composite Materials: Why It Matters and What Is Happening Currently at NASA in This Area

NASA Technical Reports Server (NTRS)

McElroy, Mack; de Carvalho, Nelson; Estes, Ashley; Lin, Shih-yung

2017-01-01

Use of lightweight composite materials in space and aircraft structure designs is often challenging due to high costs associated with structural certification. Of primary concern in the use of composite structures is durability and damage tolerance. This concern is due to the inherent susceptibility of composite materials to both fabrication and service induced flaws. Due to a lack of general industry accepted analysis tools applicable to composites damage simulation, a certification procedure relies almost entirely on testing. It is this reliance on testing, especially compared to structures comprised of legacy metallic materials where damage simulation tools are available, that can drive costs for using composite materials in aerospace structures. The observation that use of composites can be expensive due to testing requirements is not new and as such, research on analysis tools for simulating damage in composite structures has been occurring for several decades. A convenient approach many researchers/model-developers in this area have taken is to select a specific problem relevant to aerospace structural certification and develop a model that is accurate within that scope. Some examples are open hole tension tests, compression after impact tests, low-velocity impact, damage tolerance of an embedded flaw, and fatigue crack growth to name a few. Based on the premise that running analyses is cheaper than running tests, one motivation that many researchers in this area have is that if generally applicable and reliable damage simulation tools were available the dependence on certification testing could be lessened thereby reducing overall design cost. It is generally accepted that simulation tools if applied in this manner would still need to be thoroughly validated and that composite testing will never be completely replaced by analysis. Research and development is currently occurring at NASA to create numerical damage simulation tools applicable to damage in composites. The Advanced Composites Project (ACP) at NASA Langley has supported the development of composites damage simulation tools in a consortium of aerospace companies with a goal of reducing the certification time of a commercial aircraft by 30%. And while the scope of ACP does not include spacecraft, much of the methodology and simulation capabilities can apply to spacecraft certification in the Space Launch System and Orion programs as well. Some specific applications of composite damage simulation models in a certification program are (1) evaluation of damage during service when maintenance may be difficult or impossible, (2) a tool for early design iterations, (3) gaining insight into a particular damage process and applying this insight towards a test coupon or structural design, and (4) analysis of damage scenarios that are difficult or impossible to recreate in a test. As analysis capabilities improve, these applications and more will become realized resulting in a reduction in cost for use of composites in aerospace vehicles. NASA is engaged in this process from both research and application perspectives. In addition to the background information discussed previously, this presentation covers a look at recent research at NASA in this area and some current/potential applications in the Orion program.

Simulation of ultrasonic NCF composites testing using 3D finite element model

NASA Astrophysics Data System (ADS)

Liu, Z.; Saffari, N.; Fromme, P.

2012-04-01

Composite materials offer many advantages for aerospace applications, e.g., good strength to weight ratio. Different types of composites, such as non-crimp fabrics (NCF), are currently being investigated as they offer reduced manufacturing costs and improved damage tolerance as compared to traditional pre-impregnated composite materials. NCF composites are made from stitched fiber bundles (tows), which typically have a width and thickness in the order of millimeter. This results in strongly inhomogeneous and anisotropic material properties. Different types of manufacturing imperfections, such as porosity, resin pockets, tow crimp and misalignment can lead to reduced material strength and thus to defects following excessive loads or impact, e.g. fracture and delaminations. The ultrasonic non-destructive testing of NCF composites is difficult, as the tow size is comparable to the wavelength, leading to multiple scattering in this inherently three-dimensional structure. For typical material properties and geometry of an NCF composite, a full three-dimensional Finite Element (FE) model has been developed in ABAQUS. The propagation of longitudinal ultrasonic waves has been simulated and the effect of multiple scattering at the fiber tows investigated. The effect of porosity as a typical manufacturing imperfection has been considered. The potential for the detection and quantification of such defects is discussed based on the observed influence on the ultrasonic wave propagation and attenuation.

3D finite element simulation of non-crimp fabric composites ultrasonic testing

NASA Astrophysics Data System (ADS)

Liu, Z.; Saffari, N.; Fromme, P.

2012-05-01

Composite materials offer many advantages for aerospace applications, e.g., good strength to weight ratio. Different types of composites, such as non-crimp fabrics (NCF), are currently being investigated as they offer reduced manufacturing costs and improved damage tolerance as compared to traditional pre-impregnated composite materials. NCF composites are made from stitched fiber bundles (tows), which typically have a width and thickness of less than a millimeter. This results in strongly inhomogeneous and anisotropic material properties. Different types of manufacturing imperfections, such as porosity, resin pockets, tow crimp and misalignment can lead to reduced material strength and thus to defects following excessive loads or impact, e.g., fracture and delaminations. The ultrasonic non-destructive testing of NCF composites is difficult, as the tow size is comparable to the wavelength, leading to multiple scattering in this inherently three-dimensional structure. For typical material properties and geometry of an NCF composite, a full three-dimensional Finite Element (FE) model has been developed in ABAQUS. The propagation of longitudinal ultrasonic waves has been simulated and the effect of multiple scattering at the fiber tows investigated. The influence of porosity in the epoxy matrix as a typical manufacturing defect on the ultrasonic wave propagation and attenuation has been studied.

Composite structural materials

NASA Technical Reports Server (NTRS)

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1982-01-01

Research in the basic composition, characteristics, and processng science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to problems. Detailed descriptions of the progress achieved in the various component parts of his program are presented.

First industrial strength multi-axial Robotic testing campaign for composite material characterization

Treesearch

John G. Michopoulos; John C. Hermanson; Athanasios Iliopoulos

2012-01-01

In this paper we are reporting on the first successful campaign of systematic, automated and massive multiaxial tests for composite material constitutive characterization. The 6 degrees of freedom system developed at the Naval Research Laboratory (NRL) called NRL66.3, was used for this task. This was the inaugural run that served as the validation of the...

Radiation protection using Martian surface materials in human exploration of Mars

NASA Technical Reports Server (NTRS)

Kim, M. H.; Thibeault, S. A.; Wilson, J. W.; Heilbronn, L.; Kiefer, R. L.; Weakley, J. A.; Dueber, J. L.; Fogarty, T.; Wilkins, R.

2001-01-01

To develop materials for shielding astronauts from the hazards of GCR, natural Martian surface materials are considered for their potential as radiation shielding for manned Mars missions. The modified radiation fluences behind various kinds of Martian rocks and regolith are determined by solving the Boltzmann equation using NASA Langley's HZETRN code along with the 1977 Solar Minimum galactic cosmic ray environmental model. To develop structural shielding composite materials for Martian surface habitats, theoretical predictions of the shielding properties of Martian regolith/polyimide composites has been computed to assess their shielding effectiveness. Adding high-performance polymer binders to Martian regolith to enhance structural properties also enhances the shielding properties of these composites because of the added hydrogenous constituents. Heavy ion beam testing of regolith simulant/polyimide composites is planned to validate this prediction. Characterization and proton beam tests are performed to measure structural properties and to compare the shielding effects on microelectronic devices, respectively.

Time-temperature-stress capabilities of composite materials for advanced supersonic technology application, phase 1

NASA Technical Reports Server (NTRS)

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

1980-01-01

Implementation of metal and resin matrix composites into supersonic vehicle usage is contingent upon accelerating the demonstration of service capacity and design technology. Because of the added material complexity and lack of extensive service data, laboratory replication of the flight service will provide the most rapid method of documenting the airworthiness of advanced composite systems. A program in progress to determine the time temperature stress capabilities of several high temperature composite materials includes thermal aging, environmental aging, fatigue, creep, fracture, and tensile tests as well as real time flight simulation exposure. The program has two parts. The first includes all the material property determinations and aging and simulation exposures up through 10,000 hours. The second continues these tests up to 50,000 cumulative hours. Results are presented of the 10,000 hour phase, which has now been completed.

Formulation and Evaluation of a Novel Adhesive Film for Use in Composite Patch Repair

NASA Astrophysics Data System (ADS)

Tsamasphyros, G.; Kalkanis, K.; Maroulas, P.; Anthoulis, G. I.; Grigoryeva, O.

2008-08-01

The current work focuses on the testing of a novel material used as an adhesive film in Composite Patch Repair (CPR). A series of Differential Scanning Calorimetry (DSC) results along with various curing cycles not only led to the optimum material composition but also demonstrated the compatibility to the composite pre-impregnated patches. This in turn was subjected to mechanical testing including shear strength measurements. The substrate was chosen to be 2017 T4 aluminium alloy which is customarily used in the aerospace industry, taking into account that CPR is a technique mainly applied in this field. The subsequent surface preparation of the specimens was investigated for the specified context resulting to the selection of the Ferric Sulphate Sulphuric acid etching process. Finally, a series of specimens representing actual skin repairs were created and subjected to cyclic loading, specifying the suitability of the novel material, compared to commercially available materials.

Structural characterization of high temperature composites

NASA Technical Reports Server (NTRS)

Mandell, J. F.; Grande, D. H.

1991-01-01

Glass, ceramic, and carbon matrix composite materials have emerged in recent years with potential properties and temperature resistance which make them attractive for high temperature applications such as gas turbine engines. At the outset of this study, only flexural tests were available to evaluate brittle matrix composites at temperatures in the 600 to 1000 C range. The results are described of an ongoing effort to develop appropriate tensile, compression, and shear test methods for high temperature use. A tensile test for unidirectional composites was developed and used to evaluate the properties and behavior of ceramic fiber reinforced glass and glass-ceramic matrix composites in air at temperatures up to 1000 C. The results indicate generally efficient fiber reinforcement and tolerance to matrix cracking similar to polymer matrix composites. Limiting properties in these materials may be an inherently very low transverse strain to failure, and high temperature embrittlement due to fiber/matrix interface oxidation.

Composite Development and Applications for RLV Tankage

NASA Technical Reports Server (NTRS)

Wright, Richard J.; Achary, David C.; McBain, Michael C.

2003-01-01

The development of polymer composite cryogenic tanks is a critical step in creating the next generation of launch vehicles. Future launch vehicles need to minimize the gross liftoff weight (GLOW), which is possible due to the 28%-41% reduction in weight that composite materials can provide over current aluminum technology. The development of composite cryogenic tanks, feedlines, and unpressurized structures are key enabling technologies for performance and cost enhancements for Reusable Launch Vehicles (RLVs). The technology development of composite tanks has provided direct and applicable data for feedlines, unpressurized structures, material compatibility, and cryogenic fluid containment for highly loaded complex structures and interfaces. All three types of structure have similar material systems, processing parameters, scaling issues, analysis methodologies, NDE development, damage tolerance, and repair scenarios. Composite cryogenic tankage is the most complex of the 3 areas and provides the largest breakthrough in technology. A building block approach has been employed to bring this family of difficult technologies to maturity. This approach has built up composite materials, processes, design, analysis and test methods technology through a series of composite test programs beginning with the NASP program to meet aggressive performance goals for reusable launch vehicles. In this paper, the development and application of advanced composites for RLV use is described.

Composite Failures: A Comparison of Experimental Test Results and Computational Analysis Using XFEM

DTIC Science & Technology

2016-09-30

NUWC-NPT Technical Report 12,218 30 September 2016 Composite Failures: A Comparison of Experimental Test Results and Computational Analysis...A Comparison of Experimental Test Results and Computational Analysis Using XFEM 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...availability of measurement techniques, experimental testing of composite materials has largely outpaced the computational modeling ability, forcing

Full-scale testing, production and cost analysis data for the advanced composite stabilizer for Boeing 737 aircraft. Volume 1: Technical summary

NASA Technical Reports Server (NTRS)

Aniversario, R. B.; Harvey, S. T.; Mccarty, J. E.; Parsons, J. T.; Peterson, D. C.; Pritchett, L. D.; Wilson, D. R.; Wogulis, E. R.

1983-01-01

The full scale ground test, ground vibration test, and flight tests conducted to demonstrate a composite structure stabilizer for the Boeing 737 aircraft and obtain FAA certification are described. Detail tools, assembly tools, and overall production are discussed. Cost analyses aspects covered include production costs, composite material usage factors, and cost comparisons.

Composite Structures Materials Testing for the Orion Crew Vehicle Heat Shield

NASA Technical Reports Server (NTRS)

Khemani, Farah N.

2011-01-01

As research is being performed for the new heat shield for the Orion capsule, National Aeronautics and Space Administration (NASA) is developing the first composite heat shield. As an intern of the Structures Branch in the Engineering Directorate (ES 2), my main task was to set up a test plan to determine the material properties of the honeycomb that will be used on the Orion Crew Module heat shield to verify that the composite is suitable for the capsule. Before conducting composite shell tests, which are performed to simulate the crush performance of the heat shield on the capsule, it is necessary to determine the compression and shear properties of the composite used on the shell. During this internship, I was responsible for developing a test plan, designing parts for the test fixtures as well as getting them fabricated for the honeycomb shear and compression testing. This involved work in Pro/Engineer as well as coordinating with Fab Express, the Building 9 Composite Shop and the Structures Test Laboratory (STL). The research and work executed for this project will be used for composite sandwich panel testing in the future as well. As a part of the Structures Branch, my main focus was to research composite structures. This involves system engineering and integration (SE&I) integration, manufacturing, and preliminary testing. The procedures for these projects that were executed during this internship included design work, conducting tests and performing analysis.

Contact angle and surface free energy of experimental resin-based dental restorative materials after chewing simulation.

PubMed

Rüttermann, Stefan; Beikler, Thomas; Janda, Ralf

2014-06-01

To investigate contact angle and surface free energy of experimental dental resin composites containing novel delivery systems of polymeric hollow beads and low-surface tension agents after chewing simulation test. A delivery system of novel polymeric hollow beads differently loaded with two low-surface tension agents was used in different amounts to modify commonly formulated experimental dental resin composites. The non-modified resin was used as standard. Surface roughness Ra, contact angle Θ, total surface free energy γS, its apolar γS(LW), polar γS(AB), Lewis acid γS(+) and base γS(-) terms were determined and the results prior to and after chewing simulation test were compared. Significance was p<0.05. After chewing simulation Ra increased, Θ decreased, Ra increased for two test materials and γS decreased or remained constant for the standard or the test materials after chewing simulation. Ra of one test material was higher than of the standard, Θ and γS of the test materials remained lower than of the standard and, indicating their highly hydrophobic character (Θ≈60-75°, γS≈30mJm(-2)). γS(LW), and γS(-) of the test materials were lower than of the standard. Some of the test materials had lower γS(AB) and γS(+) than of the standard. Delivery systems based on novel polymeric hollow beads highly loaded with low-surface tension agents were found to significantly increase contact angle and thus to reduce surface free energy of experimental dental resin composites prior to and after chewing simulation test. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Simulation of router action on a lathe to test the cutting tool performance in edge-trimming of graphite/epoxy composite

NASA Astrophysics Data System (ADS)

Ramulu, M.; Rogers, E.

1994-04-01

The predominant machining application with graphite/epoxy composite materials in aerospace industry is peripheral trimming. The computer numerically controlled (CNC) high speed routers required to do edge trimming work are generally scheduled for production work in industry and are not available for extensive cutter testing. Therefore, an experimental method of simulating the conditions of periphery trim using a lathe is developed in this paper. The validity of the test technique will be demonstrated by conducting carbide tool wear tests under dry cutting conditions. The experimental results will be analyzed to characterize the wear behavior of carbide cutting tools in machining the composite materials.

Effects of elevated temperature on the viscoplastic modeling of graphite/polymeric composites

NASA Technical Reports Server (NTRS)

Gates, Thomas S.

1991-01-01

To support the development of new materials for the design of next generation supersonic transports, a research program is underway at NASA to assess the long term durability of advanced polymer matrix composites (PMC's). One of main objectives of the program was to explore the effects of elevated temperature (23 to 200 C) on the constitutive model's material parameters. To achieve this goal, test data on the observed nonlinear, stress-strain behavior of IM7/5260 and IM7/8320 composites under tension and compression loading were collected and correlated against temperature. These tests, conducted under isothermal conditions using variable strain rates, included such phenomena as stress relaxation and short term creep. The second major goal was the verification of the model by comparison of analytical predictions and test results for off axis and angle ply laminates. Correlation between test and predicted behavior was performed for specimens of both material systems over a range of temperatures. Results indicated that the model provided reasonable predictions of material behavior in load or strain controlled tests. Periods of loading, unloading, stress relaxation, and creep were accounted for.

Mechanical testing and modelling of carbon-carbon composites for aircraft disc brakes

NASA Astrophysics Data System (ADS)

Bradley, Luke R.

The objective of this study is to improve the understanding of the stress distributions and failure mechanisms experienced by carbon-carbon composite aircraft brake discs using finite element (FE) analyses. The project has been carried out in association with Dunlop Aerospace as an EPSRC CASE studentship. It therefore focuses on the carbon-carbon composite brake disc material produced by Dunlop Aerospace, although it is envisaged that the approach will have broader applications for modelling and mechanical testing of carbon-carbon composites in general. The disc brake material is a laminated carbon-carbon composite comprised of poly(acrylonitrile) (PAN) derived carbon fibres in a chemical vapour infiltration (CVI) deposited matrix, in which the reinforcement is present in both continuous fibre and chopped fibre forms. To pave the way for the finite element analysis, a comprehensive study of the mechanical properties of the carbon-carbon composite material was carried out. This focused largely, but not entirely, on model composite materials formulated using structural elements of the disc brake material. The strengths and moduli of these materials were measured in tension, compression and shear in several orientations. It was found that the stress-strain behaviour of the materials were linear in directions where there was some continuous fibre reinforcement, but non-linear when this was not the case. In all orientations, some degree of non-linearity was observed in the shear stress-strain response of the materials. However, this non-linearity was generally not large enough to pose a problem for the estimation of elastic moduli. Evidence was found for negative Poisson's ratio behaviour in some orientations of the material in tension. Additionally, the through-thickness properties of the composite, including interlaminar shear strength, were shown to be positively related to bulk density. The in-plane properties were mostly unrelated to bulk density over the range of densities of the tested specimens.Two types of FE model were developed using a commercially available program. The first type was designed to analyse the model composite materials for comparison with mechanical test data for the purpose of validation of the FE model. Elastic moduli predicted by this type of FE model showed good agreement with the experimentally measured elastic moduli of the model composite materials. This result suggested that the use of layered FE models, which rely upon an isostrain assumption between the layers, can be useful in predicting the elastic properties of different lay-ups of the disc brake material.The second type of FE model analysed disc brake segments, using the experimentally measured bulk mechanical properties of the disc brake material. This FE model approximated the material as a continuum with in-plane isotropy but with different properties in the through-thickness direction. In order to validate this modelling approach, the results of the FE analysis were compared with mechanical tests on disc brake segments, which were loaded by their drive tenons in a manner intended to simulate in-service loading. The FE model showed good agreement with in-plane strains measured on the disc tenon face close to the swept area of the disc, but predicted significantly higher strains than those experimentally measured on the tenon fillet curve. This discrepancy was attributed to the existence of a steep strain gradient on the fillet curve.

Effects of static tensile load on the thermal expansion of Gr/PI composite material

NASA Technical Reports Server (NTRS)

Farley, G. L.

1981-01-01

The effect of static tensile load on the thermal expansion of Gr/PI composite material was measured for seven different laminate configurations. A computer program was developed which implements laminate theory in a piecewise linear fashion to predict the coupled nonlinear thermomechanical behavior. Static tensile load significantly affected the thermal expansion characteristics of the laminates tested. This effect is attributed to a fiber instability micromechanical behavior of the constituent materials. Analytical results correlated reasonably well with free thermal expansion tests (no load applied to the specimen). However, correlation was poor for tests with an applied load.

Correlating PMC-MMC Bonded Joint 3D FEA with Test

NASA Technical Reports Server (NTRS)

Jacobson, Mindy; Rodini, Benjamin; Chen, Wayne C.; Flom, Yury A.; Posey, Alan J.

2005-01-01

A viewgraph presentation on the correlation of Polymer Matrix Composites (PMC) and Metal Matrix Composites (MMC) bonded joints using three dimensional finite element analyses with materials tests is shown.

Deformation and failure information from composite materials via acoustic emission

NASA Technical Reports Server (NTRS)

Hamstad, M. A.

1978-01-01

The paper reviews some principles of applying acoustic emission (AE) to the study of fiber-composite materials and structures. This review covers the basics of using AE to monitor the deformation and fracture processes that occur when fiber-composite materials are stressed. Also, new results in some areas of current research interest are presented. The following areas are emphasized: study of couplants for AE testing of composites, evaluation of a special immersion-type AE transducer, and wave propagation complications and the development of techniques for locating AE sources in Kevlar 49/epoxy composite pre

Ultrasonic Characterization of Fatigue Cracks in Composite Materials

NASA Technical Reports Server (NTRS)

Workman, Gary L.; Watson, Jason; Johnson, Devin; Walker, James; Russell, Sam; Thom, Robert (Technical Monitor)

2002-01-01

Microcracking in composite structures due to combined fatigue and cryogenic loading can cause leakage and failure of the structure and can be difficult to detect in-service. In aerospace systems, these leaks may lead to loss of pressure/propellant, increased risk of explosion and possible cryo-pumping. The success of nondestructive evaluation to detect intra-ply microcracking in unlined pressure vessels fabricated from composite materials is critical to the use of composite structures in future space systems. The work presented herein characterizes measurements of intraply fatigue cracking through the thickness of laminated composite material by means of correlation with ultrasonic resonance. Resonant ultrasound spectroscopy provides measurements which are sensitive to both the microscopic and macroscopic properties of the test article. Elastic moduli, acoustic attenuation, and geometry can all be probed. The approach is based on the premise of half-wavelength resonance. The method injects a broadband ultrasonic wave into the test structure using a swept frequency technique. This method provides dramatically increased energy input into the test article, as compared to conventional pulsed ultrasonics. This relative energy increase improves the ability to measure finer details in the materials characterization, such as microcracking and porosity. As the microcrack density increases, more interactions occur with the higher frequency (small wavelength) components of the signal train causing the spectrum to shift toward lower frequencies. Several methods are under investigation to correlate the degree of microcracking from resonance ultrasound measurements on composite test articles including self organizing neural networks, chemometric techniques used in optical spectroscopy and other clustering algorithms.

Changes in composition and porosity occurring during the thermal degradation of wood and wood components

USGS Publications Warehouse

Rutherford, David W.; Wershaw, Robert L.; Cox, Larry G.

2005-01-01

Samples of pine and poplar wood, pine bark, and purified cellulose and lignin were charred at temperatures ranging from 250?C to 500?C for times ranging from 1 hour to 168 hours. Changes in composition were examined by Fourier Transform Infrared (FTIR) and 13C Nuclear Magnetic Resonance (NMR) spectrometry, mass loss, and elemental composition (carbon, hydrogen, and oxygen) of the char. Structural changes were examined by changes in porosity as measured by nitrogen gas adsorption. 13C NMR spectrometry, mass loss, and elemental composition were combined to estimate the mass of aromatic and aliphatic carbon remaining in the char. Mass loss and elemental composition were combined to estimate the chemical composition of material lost for various time intervals of heating. These analyses showed that aliphatic components in the test materials were either lost or converted to aromatic carbon early in the charring process. Nitrogen adsorption showed that no porosity develops for any of the test materials with heating at 250?C, even though substantial loss of material and changes in composition occurred. Porosity development coincided with the loss of aromatic carbon, indicating that micropores were developing within a fused-ring matrix.

Performance of a Steel/Oxide Composite Waste Form for Combined Waste Steams from Advanced Electrochemical Processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Indacochea, J. E.; Gattu, V. K.; Chen, X.

The results of electrochemical corrosion tests and modeling activities performed collaboratively by researchers at the University of Illinois at Chicago and Argonne National Laboratory as part of workpackage NU-13-IL-UIC-0203-02 are summarized herein. The overall objective of the project was to develop and demonstrate testing and modeling approaches that could be used to evaluate the use of composite alloy/ceramic materials as high-level durable waste forms. Several prototypical composite waste form materials were made from stainless steels representing fuel cladding, reagent metals representing metallic fuel waste streams, and reagent oxides representing oxide fuel waste streams to study the microstructures and corrosion behaviorsmore » of the oxide and alloy phases. Microelectrodes fabricated from small specimens of the composite materials were used in a series of electrochemical tests to assess the corrosion behaviors of the constituent phases and phase boundaries in an aggressive acid brine solution at various imposed surface potentials. The microstructures were characterized in detail before and after the electrochemical tests to relate the electrochemical responses to changes in both the electrode surface and the solution composition. The results of microscopic, electrochemical, and solution analyses were used to develop equivalent circuit and physical models representing the measured corrosion behaviors of the different materials pertinent to long-term corrosion behavior. This report provides details regarding (1) the production of the composite materials, (2) the protocol for the electrochemical measurements and interpretations of the responses of multi-phase alloy and oxide composites, (3) relating corrosion behaviors to microstructures of multi-phase alloys based on 316L stainless steel and HT9 (410 stainless steel was used as a substitute) with added Mo, Ni, and/or Mn, and (4) modeling the corrosion behaviors and rates of several alloy/oxide composite materials made with added lanthanide and uranium oxides. These analyses show the corrosion behaviors of the alloy/ceramic composite materials are very similar to the corrosion behaviors of multi-phase alloy waste forms, and that the presence of oxide inclusions does not impact the corrosion behaviors of the alloy phases. Mixing with metallic waste streams is beneficial to lanthanide and uranium oxides in that they react with Zr in the fuel waste to form highly durable zirconates. The measured corrosion behaviors suggest properly formulated composite materials would be suitable waste forms for combined metallic and oxide waste streams generated during electrometallurgical reprocessing of spent nuclear fuel. Electrochemical methods are suitable for evaluating the durability and modeling long-term behavior of composite waste forms: the degradation model developed for metallic waste forms can be applied to the alloy phases formed in the composite and an affinity-based mineral dissolution model can be applied to the ceramic phases.« less

Dynamic Shock Response of an S2 Glass/SC15 Epoxy Woven Fabric Composite Material System

NASA Astrophysics Data System (ADS)

Key, Christopher; Alexander, Scott; Harstad, Eric; Schumacher, Shane

2017-06-01

The use of S2 glass/SC15 epoxy woven fabric composite materials for blast and ballistic protection has been an area of on-going research over the past decade. In order to accurately model this material system within potential applications under extreme loading conditions, a well characterized and well understood anisotropic equation of state (EOS) is needed. This work details both an experimental program and associated analytical modelling efforts which aim to provide better physical understanding of the anisotropic EOS behavior of this material. Experimental testing focused on planar shock impact tests loading the composite to peak pressures of 15 GPa in both the through-thickness and on-fiber orientation. Test results highlighted the anisotropic response of the material and provided a basis by which the associated numeric micromechanical investigation was compared. Results of the combined experimental and numerical modelling investigation provided insights into not only the constituent material influence on the composite response but also the importance of the geometrical configuration of the plain weave microstructure and the stochastic significance of the microstructural configuration. Sandia National Laboratories is a multi-mission laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin company, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Time-temperature-stress capabilities of composite materials for advanced supersonic technology application

NASA Technical Reports Server (NTRS)

Kerr, James R.; Haskins, James F.

1987-01-01

Advanced composites will play a key role in the development of the technology for the design and fabrication of future supersonic vehicles. However, incorporating the material into vehicle usage is contingent on accelerating the demonstration of service capacity and design technology. Because of the added material complexity and lack of extensive data, laboratory replication of the flight service will provide the most rapid method to document the airworthiness of advanced composite systems. Consequently, a laboratory program was conducted to determine the time-temperature-stress capabilities of several high temperature composites. Tests included were thermal aging, environmental aging, fatigue, creep, fracture, tensile, and real-time flight simulation exposure. The program had two phases. The first included all the material property determinations and aging and simulation exposures up through 10,000 hours. The second continued these tests up to 50,000 cumulative hours. This report presents the results of the Phase 1 baseline and 10,000-hr aging and flight simulation studies, the Phase 2 50,000-hr aging studies, and the Phase 2 flight simulation tests, some of which extended to almost 40,000 hours.

Damage assessment of composite plate structures with material and measurement uncertainty

NASA Astrophysics Data System (ADS)

Chandrashekhar, M.; Ganguli, Ranjan

2016-06-01

Composite materials are very useful in structural engineering particularly in weight sensitive applications. Two different test models of the same structure made from composite materials can display very different dynamic behavior due to large uncertainties associated with composite material properties. Also, composite structures can suffer from pre-existing imperfections like delaminations, voids or cracks during fabrication. In this paper, we show that modeling and material uncertainties in composite structures can cause considerable problem in damage assessment. A recently developed C0 shear deformable locking free refined composite plate element is employed in the numerical simulations to alleviate modeling uncertainty. A qualitative estimate of the impact of modeling uncertainty on the damage detection problem is made. A robust Fuzzy Logic System (FLS) with sliding window defuzzifier is used for delamination damage detection in composite plate type structures. The FLS is designed using variations in modal frequencies due to randomness in material properties. Probabilistic analysis is performed using Monte Carlo Simulation (MCS) on a composite plate finite element model. It is demonstrated that the FLS shows excellent robustness in delamination detection at very high levels of randomness in input data.

Tensile and Flexural Test on Kenaf Hybrid Composites

NASA Astrophysics Data System (ADS)

Salleh, Z.; Yunus, S.; Masdek, N. R. N. M.; Taib, Y. M.; Azhar, I. I. S.; Hyie, K. M.

2018-03-01

The widely use of synthetic materials like carbon and fiberglass in various industries such as automotive and aircraft has lead to human health and environment problems. Therefore, the use of natural fibres such as kenaf has received higher attention as reinforcement. Kenaf or the scientific name is Hibiscus Cannabinus. L is one of the group of Malvecea plant which in the early days, the application of kenaf served only rope and canvas. However, it has more advantages than synthetic materials such as; widely availaible, renewable, lightweight, non-abbrasiveness during processing, high specific strength, free from health hazard and biodegradeable. This study was carried out to investigate the effects of different arrangement of kenaf and fiberglass composites on Young’s Modulus. The material composite was hardened with polyester resin and their properties was characterized. The tensile and the flexural properties is determined using an Instron universal tensile testing machine and carried out by following ASTM D3039 for tensile and ASTM D790 for a flexural test. The experimental program was designed to correlate the flexural and tensile Young’s Modulus of kenaf and fiberglass composite under the same load condition but different arrangement of kenaf and fiberglass on the mold . The resistance to change in shape was described by the behavior and characteristic of the composite materials. The stiffness or the elastic modulus of the composite material was determined at the end of the experiment. The results obtained show that the [±90FG/0/90/90/0/±90FG] kenaf/fiberglass composite arrangement has the highest elastic value.

High-resolution nondestructive testing of multilayer dielectric materials using wideband microwave synthetic aperture radar imaging

NASA Astrophysics Data System (ADS)

Kim, Tae Hee; James, Robin; Narayanan, Ram M.

2017-04-01

Fiber Reinforced Polymer or Plastic (FRP) composites have been rapidly increasing in the aerospace, automotive and marine industry, and civil engineering, because these composites show superior characteristics such as outstanding strength and stiffness, low weight, as well as anti-corrosion and easy production. Generally, the advancement of materials calls for correspondingly advanced methods and technologies for inspection and failure detection during production or maintenance, especially in the area of nondestructive testing (NDT). Among numerous inspection techniques, microwave sensing methods can be effectively used for NDT of FRP composites. FRP composite materials can be produced using various structures and materials, and various defects or flaws occur due to environmental conditions encountered during operation. However, reliable, low-cost, and easy-to-operate NDT methods have not been developed and tested. FRP composites are usually produced as multilayered structures consisting of fiber plate, matrix and core. Therefore, typical defects appearing in FRP composites are disbondings, delaminations, object inclusions, and certain kinds of barely visible impact damages. In this paper, we propose a microwave NDT method, based on synthetic aperture radar (SAR) imaging algorithms, for stand-off imaging of internal delaminations. When a microwave signal is incident on a multilayer dielectric material, the reflected signal provides a good response to interfaces and transverse cracks. An electromagnetic wave model is introduced to delineate interface widths or defect depths from the reflected waves. For the purpose of numerical analysis and simulation, multilayered composite samples with various artificial defects are assumed, and their SAR images are obtained and analyzed using a variety of high-resolution wideband waveforms.

Baseline tensile tests of composite materials for LDEF (Long Duration Exposure Facility) exposure

NASA Technical Reports Server (NTRS)

Witte, William G.

1987-01-01

Tensile specimens of five graphite fiber reinforced composite materials were tested at room temperature to provide baseline data for similar specimens exposed to the space environment in low-Earth orbit on the NASA Long Duration Exposure Facility. All specimens were 4-ply (+ or - 45 deg)s layups; at least five replicate specimens were tested for each parameter evaluated. Three epoxy-matrix materials and two polysulfone-matrix materials, several fiber volume fractions, and two sizes of specimen were evaluated. Stress-strain and Poisson's ratio-stress curves, ultimate stress, strain at failure, secant modulus at 0.004 strain, inplane shear stress-strain curves, and unidirectional shear modulus at .004 shear strain are presented.

Considerations Concerning the Development and Testing of In-situ Materials for Martian Exploration

NASA Technical Reports Server (NTRS)

Kim, M.-H. Y.; Heilbronn, L.; Thibeault, S. A.; Simonsen, L. C.; Wilson, J. W.; Chang, K.; Kiefer, R. L.; Maahs, H. G.

2000-01-01

Natural Martian surface materials are evaluated for their potential use as radiation shields for manned Mars missions. The modified radiation fluences behind various kinds of Martian rocks and regolith are determined by solving the Boltzmann equation using NASA Langley s HZETRN code along with the 1977 Solar Minimum galactic cosmic ray environmental model. To make structural shielding composite materials from constituents of the Mars atmosphere and from Martian regolith for Martian surface habitats, schemes for synthesizing polyimide from the Mars atmosphere and for processing Martian regolith/polyimide composites are proposed. Theoretical predictions of the shielding properties of these composites are computed to assess their shielding effectiveness. Adding high-performance polymer binders to Martian regolith to enhance structural properties enhances the shielding properties of these composites because of the added hydrogenous constituents. Laboratory testing of regolith simulant/polyimide composites is planned to validate this prediction.

Modified glass fibre reinforced polymer composites

NASA Astrophysics Data System (ADS)

Cao, Yumei

A high ratio of strength to density and relatively low-cost are some of the significant features of glass fibre reinforced polymer composites (GFRPCs) that made them one of the most rapidly developed materials in recent years. They are widely used as the material of construction in the areas of aerospace, marine and everyday life, such as airplane, helicopter, boat, canoe, fishing rod, racket, etc. Traditionally, researchers tried to raise the mechanical properties and keep a high strength/weight ratio using all or some of the following methods: increasing the volume fraction of the fibre; using different polymeric matrix material; or changing the curing conditions. In recent years, some new techniques and processing methods were developed to further improve the mechanical properties of glass fibre (GF) reinforced polymer composite. For example, by modifying the surface condition of the GF, both the interface strength between the GF and the polymer matrix and the shear strength of the final composite can be significantly increased. Also, by prestressing the fibre during the curing process of the composite, the tensile, flexural and the impact properties of the composite can be greatly improved. In this research project, a new method of preparing GFRPCs, which combined several traditional and modern techniques together, was developed. This new method includes modification of the surface of the GF with silica particles, application of different levels of prestressing on the GF during the curing process, and the change of the fibre volume fraction and curing conditions in different sets of experiments. The results of the new processing were tested by the three-point bend test, the short beam shear test and the impact test to determine the new set of properties so formed in the composite material. Scanning electronic microscopy (SEM) was used to study the fracture surface of the new materials after the mechanical tests were performed. By taking advantages of the traditional and modern techniques at the same time, the newly developed modified glass fibre reinforced epoxy matrix composites (MGFRECs) have much improved comprehensive properties. The flexural strength, the flexural modulus, the shear modulus and the impact energy (Izod impact test) of the composites were improved up to 87%, 74%, 30% and 89% respectively when modified samples were compared to the samples made by the traditional methods.

Synthesis and Performance of Tungsten Disulfide/Carbon (WS2/C) Composite as Anode Material

NASA Astrophysics Data System (ADS)

Yuan, Zhengyong; Jiang, Qiang; Feng, Chuanqi; Chen, Xiao; Guo, Zaiping

2018-01-01

The precursors of an amorphous WS2/C composite were synthesized by a simple hydrothermal method using Na2WO4·2H2O and CH3CSNH2 as raw materials, polyethylene glycol as dispersant, and glucose as the carbon source. The as-synthesized precursors were further annealed at a low temperature in flowing argon to obtain the final materials (WS2/C composite). The structure and morphology of the WS2/C composite were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, and scanning electron microscopy. The electrochemical properties were tested by galvanostatic charge/discharge testing and alternating current (AC) impedance measurements. The results show that the as-prepared amorphous WS2/C composite features both high specific capacity and good cycling performance at room temperature within the potential window from 3.0 V to 0.01 V (versus Li+/Li) at current density of 100 mAg-1. The achieved initial discharge capacity was 1080 mAhg-1, and 786 mAhg-1 was retained after 170 cycles. Furthermore, the amorphous WS2/C composite exhibited a lower charge/discharge plateau than bare WS2, which is more beneficial for use as an anode. The cyclic voltammetry and AC impedance testing further confirmed the change in the plateau and the decrease in the charge transfer resistance in the WS2/C composite. The chemical formation process and the electrochemical mechanism of the WS2/C composite are also presented. The amorphous WS2/C composite can be used as a new anode material for future applications.

USGS reference materials

USGS Publications Warehouse

,

1995-01-01

Every year in the United States, millions of measurements are made on the chemical composition of items that affect us on a daily basis. Determining the accuracy of these measurements is based on the analysis of appropriate reference materials whose composition was previously determined through rigorous testing. Today, reference materials help us evaluate the composition of the food we eat, medicine we use, soil we grow our crops in, and hundreds of other products that affect our everyday lives.

The experimental behavior of spinning pretwisted laminated composite plates

NASA Technical Reports Server (NTRS)

Kosmatka, John B.; Lapid, Alex J.

1993-01-01

The purpose of the research is to gain an understanding of the material and geometric couplings present in advanced composite turbo-propellers. Twelve pre-twisted laminated composite plates are tested. Three different ply lay-ups (2 symmetric and 1 asymmetric) and four different geometries (flat and 30x pre-twist about the mid-chord, quarter-chord, and leading edge) distinguish each plate from one another. Four rotating and non-rotating tests are employed to isolate the material and geometric couplings of an advanced turbo propeller. The first series of tests consist of non-rotating static displacement, strain, and vibrations. These tests examine the effects of ply lay-up and geometry. The second series of tests consist of rotating displacement, strain, and vibrations with various pitch and sweep settings. These tests utilize the Dynamic Spin Rig Facility at the NASA Lewis Research Center. The rig allows the spin testing of the plates in a near vacuum environment. The tests examine how the material and plate geometry interact with the pitch and sweep geometry of an advanced turbo-propeller.

Quiet Clean Short-haul Experimental Engine (QCSEE) Under-The-Wing (UTW) composite nacelle subsystem test report. [to verify strength of selected composite materials

NASA Technical Reports Server (NTRS)

Stotler, C. L., Jr.; Johnston, E. A.; Freeman, D. S.

1977-01-01

The element and subcomponent testing conducted to verify the under the wing composite nacelle design is reported. This composite nacelle consists of an inlet, outer cowl doors, inner cowl doors, and a variable fan nozzle. The element tests provided the mechanical properties used in the nacelle design. The subcomponent tests verified that the critical panel and joint areas of the nacelle had adequate structural integrity.

Structural studies on carbon materials for advanced space technology. Part 1: Structure and oxidation behavior of some carbon/carbon composite materials

NASA Technical Reports Server (NTRS)

Fischbach, D. B.; Uptegrove, D. R.; Srinivasagopalan, S.

1974-01-01

The microstructure and some microstructural effects of oxidation have been investigated for laminar carbon fiber cloth/cloth binder matrix composite materials. It was found that cloth wave is important in determining the macrostructure of the composites X-ray diffraction analysis showed that the composites were more graphitic than the constituent fiber phases, indicating a graphitic binder matrix phase. Various tests which were conducted to investigate specific properties of the material are described. It was learned that under the moderate temperature and oxidant flow conditions studied, C-700, 730 materials exhibit superior oxidation resistance primarily because of the inhibiting influence of the graphitized binder matrix.

Environmental degradation of composites for marine structures: new materials and new applications

PubMed Central

2016-01-01

This paper describes the influence of seawater ageing on composites used in a range of marine structures, from boats to tidal turbines. Accounting for environmental degradation is an essential element in the multi-scale modelling of composite materials but it requires reliable test data input. The traditional approach to account for ageing effects, based on testing samples after immersion for different periods, is evolving towards coupled studies involving strong interactions between water diffusion and mechanical loading. These can provide a more realistic estimation of long-term behaviour but still require some form of acceleration if useful data, for 20 year lifetimes or more, are to be obtained in a reasonable time. In order to validate extrapolations from short to long times, it is essential to understand the degradation mechanisms, so both physico-chemical and mechanical test data are required. Examples of results from some current studies on more environmentally friendly materials including bio-sourced composites will be described first. Then a case study for renewable marine energy applications will be discussed. In both cases, studies were performed first on coupons at the material level, then during structural testing and analysis of large components, in order to evaluate their long-term behaviour. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’. PMID:27242304

Analysis of shear test method for composite laminates

NASA Technical Reports Server (NTRS)

Bergner, H. W., Jr.; Davis, J. G., Jr.; Herakovich, C. T.

1977-01-01

An elastic plane stress finite element analysis of the stress distributions in four flat test specimens for in-plane shear response of composite materials subjected to mechanical or thermal loads is presented. The shear test specimens investigated include: slotted coupon, cross beam, losipescu, and rail shear. Results are presented in the form of normalized shear contour plots for all three in-plane stess components. It is shown that the cross beam, losipescu, and rail shear specimens have stress distributions which are more than adequate for determining linear shear behavior of composite materials. Laminate properties, core effects, and fixture configurations are among the factors which were found to influence the stress distributions.

ICCM/2; Proceedings of the Second International Conference on Composite Materials, Toronto, Canada, April 16-20, 1978

NASA Technical Reports Server (NTRS)

Noton, B. R. (Editor); Signorelli, R. A.; Street, K. N.; Phillips, L. N.

1978-01-01

Composite materials are discussed with reference to their mechanical and physical properties, fatigue and fracture testing and analysis, nondestructive evaluation, fabrication, and commercial applications. Particular papers are presented on such topics as analysis of mechanical strength data from hybrid laminates of glass and graphite fibers, graphite-aluminum composites, the mechanical behavior of molybdenum-reinforced metal composites, and composite laminate application in magnetic fusion energy superconducting magnet systems.

Cytotoxicity Evaluation of Self Adhesive Composite Resin Cements by Dentin Barrier Test on 3D Pulp Cells.

PubMed

Ulker, Hayriye Esra; Sengun, Abdulkadir

2009-04-01

The aim of this study was to evaluate the effects of five self-etch dental composite resin cements on the cell viability of bovine dental papilla-derived cells. The cytotoxicity of composite resin cements (Rely X Unicem Clicker, 3M ESPE; MaxCem; KERR, Panavia F 2.0; Kuraray, BisCem; Bisco and Bistite II DC; Tokuyama) was analyzed in a dentin barrier test device using three-dimensional (3D) pulp cell cultures. A commercially available cell culture perfusion chamber was separated into two compartments by 500 mum dentin disc. The three dimensional cultures placed on a dentin disk held in place by a special biocompatible stainless-steel holder. Test materials were introduced into the upper compartment in direct contact with the cavity side of the dentin disks according to the manufacturer's instructions. Subsequently, the pulpal part of the perfusion chamber containing the cell cultures was perfused with medium (2 ml/h). After an exposure period of 24 h, the cell survival was determined by the MTT assay. Statistical analyses were performed using the Mann-Whitney U-test. In dentin barrier test, cell survival was similar with Maxcem and negative control group (P>.05), and all other tested materials were cytotoxic for the three dimensional cell cultures (P>.05). The significance of composite resin cements is being more important in dentistry. The cytotoxic potencies demonstrated by these materials might be of clinical relevance. Some composite resin cements include biologically active ingredients and may modify pulp cell metabolism when the materials are used in deep cavities or directly contact pulp tissue.

Determination of mechanical properties of carbon/epoxy plates by tensile stress test

NASA Astrophysics Data System (ADS)

Bere, Paul; Krolczyk, Jolanta B.

2017-10-01

The polymeric composite materials used in aerospace, military, medical or racing cars manufacturing end up being used in our daily life Whether we refer to the performing vehicles, subassemblies or parts for aircrafts, wind, telegraph poles, or medical prostheses they all are present in our lives and they are made of composite materials (CM). This paper presents research regarding three different composite materials, plates by carbon fiber, in epoxy matrix. Starting with materials presentation, manufacturing methodology and determination of mechanical properties at carbon fiber/epoxy were done. Vacuum bag technology to obtain the composite structure offer opportunity to get a very compact and homogeny composite structure. For the moment this technology are adequate for high performances pieces. The mechanical characteristics of plates made of composite materials reinforced presented indicates closed value like metal materials. Based on the results, a comparative study between the reinforced materials typically used to manufacture the plates of CM is carried out.

Determining shear modulus of thin wood composite materials using a cantilever beam vibration method

Treesearch

Cheng Guan; Houjiang Zhang; John F. Hunt; Haicheng Yan

2016-01-01

Shear modulus (G) of thin wood composite materials is one of several important indicators that characterizes mechanical properties. However, there is not an easy method to obtain this value. This study presents the use of a newly developed cantilever beam free vibration test apparatus to detect in-plane G of thin wood composite...

Short beam shear tests of polymeric laminates and unidirectional composites

NASA Technical Reports Server (NTRS)

Stinchcomb, W. W.; Henneke, E. G.

1980-01-01

The application of advanced composite materials in aerospace, ground transportation, and sporting industries are discussed. Failure theories for the design and mechanical behavior of composite materials are emphasized. Methods for detecting specific types of flaws are outlined. The effect of detected flaws on mechanical properties such as stiffness, strength, fatigue lifetime, or residual strength is described.

Use of Thermoset Composite Materials in Cryogenic Tanks

NASA Astrophysics Data System (ADS)

Diaz, V.; Cardone, T.; Ramusat, G.

2014-06-01

To improve the performances of Future Expendable Launchers, one of the key aspects to be considered is the mass optimization of the cryogenic upper stage of the launcher, where a mass saving of one Kg, is directly transferred to one more Kg of payload.This optimization is inherently linked to the use of composite materials in all the structures that conforms the upper stage of the launcher.Currently, most of the upper stage structures of the operational launchers, like Ariane 5, are made in composite materials, with the exception of the cryogenic (LH2 and LOX) tanks which remain metallic.So, from a structural point of view, the next qualitative step in the development of new expendable launcher, would be the manufacturing of the upper stage cryogenic tanks in composite materials.To reach this objective important concerns mainly related to the potential for leaks and the compatibility with the LOX need to be resolved.In the frame of the FLPP (Future Launcher Preparatory Program) funded by ESA, an activity related to the use of thermoset composite material in the cryogenic tanks has been included.This paper presents a summary of the performed work which includes:* The selection and characterization of the most suitable candidate materials for the considered application* The design and analysis of a subscale demonstrator representative of the LH2 compartment* The design, manufacturing and testing of some test articles representatives of the selected design solutions* The manufacturing and testing of the selected subscale demonstrator.

Investigation of mechanical properties of hemp/glass fiber reinforced nano clay hybrid composites

NASA Astrophysics Data System (ADS)

Unki, Hanamantappa Ningappa; Shivanand, H. K.; Vidyasagar, H. N.

2018-04-01

Over the last twenty to thirty years composite materials have been used in engineering field. Composite materials possess high strength, high strength to weight ratio due to these facts composite materials are becoming popular among researchers and scientists. The major proportion of engineering materials consists of composite materials. Composite materials are used in vast applications ranging from day-to-day household articles to highly sophisticated applications. In this paper an attempt is made to prepare three different composite materials using e-glass and Hemp. In this present investigation hybrid composite of Hemp, Glass fiber and Nano clay will be prepared by Hand-layup technique. The glass fiber used in this present investigation is E-glass fiber bi-directional: 90˚ orientation. The composite samples will be made in the form of a Laminates. The wt% of nanoclay added in the preparation of sample is 20 gm constant. The fabricated composite Laminate will be cut into corresponding profiles as per ASTM standards for Mechanical Testing. The effect of addition of Nano clay and variation of Hemp/glass fibers will be studied. In the present work, a new Hybrid composite is developed in which Hemp, E glass fibers is reinforced with epoxy resin and with Nano clay.

Composite materials research and education program: The NASA-Virginia Tech composites program

NASA Technical Reports Server (NTRS)

Herakovich, C. T.

1980-01-01

Major areas of study include: (1) edge effects in finite width laminated composites subjected to mechanical, thermal and hygroscopic loading with temperature dependent material properties and the influence of edge effects on the initiation of failure; (2) shear and compression testing of composite materials at room and elevated temperatures; (3) optical techniques for precise measurement of coefficients of thermal expansion of composites; (4) models for the nonlinear behavior of composites including material nonlinearity and damage accumulation and verification of the models under biaxial loading; (5) compressive failure of graphite/epoxy plates with circular holes and the buckling of composite cylinders under combined compression and torsion; (6) nonlinear mechanical properties of borsic/aluminum, graphite/polyimide and boron/aluminum; (7) the strength characteristics of spliced sandwich panels; and (8) curved graphite/epoxy panels subjected to internal pressure.

Low-Cost Composite Materials and Structures for Aircraft Applications

NASA Technical Reports Server (NTRS)

Deo, Ravi B.; Starnes, James H., Jr.; Holzwarth, Richard C.

2003-01-01

A survey of current applications of composite materials and structures in military, transport and General Aviation aircraft is presented to assess the maturity of composites technology, and the payoffs realized. The results of the survey show that performance requirements and the potential to reduce life cycle costs for military aircraft and direct operating costs for transport aircraft are the main reasons for the selection of composite materials for current aircraft applications. Initial acquisition costs of composite airframe components are affected by high material costs and complex certification tests which appear to discourage the widespread use of composite materials for aircraft applications. Material suppliers have performed very well to date in developing resin matrix and fiber systems for improved mechanical, durability and damage tolerance performance. The next challenge for material suppliers is to reduce material costs and to develop materials that are suitable for simplified and inexpensive manufacturing processes. The focus of airframe manufacturers should be on the development of structural designs that reduce assembly costs by the use of large-scale integration of airframe components with unitized structures and manufacturing processes that minimize excessive manual labor.

Standard Methods for Unnotched Tension Testing of Textile Composites

NASA Technical Reports Server (NTRS)

Portanova, M. A.

1995-01-01

An investigation was conducted by researchers at the Boeing Defense & Space Group to investigate the effects of specimen sizing on several braided textile materials. Test results from this and other test programs were compared in an effort to determine what effect, if any, specimen size has on elastic property measurements of unnotched tension test. In general, the unnotched tensile strength of 2-D braids was found to be insensitive to specimen width, length, or thickness effects. The results from this study suggest that standard testing methods used for tape materials may be sufficient for tension testing of textile composite materials. Specifically, the straight sided specimen geometry described in ASTM 3034, and used by Boeing, should provide acceptable results. Further experiments performed at Boeing and by other investigators on other textile architectures suggest similar results. Although specimen size studies were not conducted, failing stresses varied on the same order as those obtained with the 2-D materials. This suggests that the accuracy of the results were consistent with those obtained with the 2-D materials.

Modifications of system for elevated temperature tensile testing and stress-strain measurement of metal matrix composites

NASA Technical Reports Server (NTRS)

Diaz, J. O.

1985-01-01

Composites consisting of tungsten alloy wires in superalloy matrices are being studied because they offer the potential for increased strength compared to current materials used at temperatures up to at least 1093 C (2000F). Previous research at the NASA Lewis Research Center and at other laboratories in the U.S., Europe, and Japan has demonstrated laboratory feasibility for fiber reinforced superalloys (FRS). The data for the mechanical and physical properties used to evaluate candidate materials is limited and a need exists for a more detailed and complete data base. The focus of this work is to develop a test procedure to provide a more complete FRS data base to quantitatively evaluate the composite's potential for component applications. This paper will describe and discuss the equipment and procedures under development to obtain elevated temperature tensile stress-strain, strength and modulus data for the first generation of tungsten fiber reinforced superalloy composite (TFRS) materials. Tensile stress-strain tests are conducted using a constant crosshead speed tensile testing machine and a modified load-strain measuring apparatus. Elevated temperature tensile tests are performed using a resistance wound commercial furnace capable of heating test specimens up to 1093 C (2000 F). Tensile stress-strain data are obtained for hollow tubular stainless steel specimens serving as a prototype for future composite specimens.

Self-Healing Nanofiber-Reinforced Polymer Composites. 1. Tensile Testing and Recovery of Mechanical Properties.

PubMed

Lee, Min Wook; An, Seongpil; Jo, Hong Seok; Yoon, Sam S; Yarin, Alexander L

2015-09-09

The present work aims at development of self-healing materials capable of partially restoring their mechanical properties under the conditions of prolonged periodic loading and unloading, which is characteristic, for example, of aerospace applications. Composite materials used in these and many other applications frequently reveal multiple defects stemming from their original inhomogeneity, which facilitates microcracking and delamination at ply interfaces. Self-healing nanofiber mats may effectively prevent such damage without compromising material integrity. Two types of core-shell nanofibers were simultaneously electrospun onto the same substrate in order to form a mutually entangled mat. The first type of core-shell fibers consisted of resin monomer (dimethylsiloxane) within the core and polyacrylonitrile within the shell. The second type of core-shell nanofibers consisted of cure (dimethyl-methyl hydrogen-siloxane) within the core and polyacrylonitrile within the shell. These mutually entangled nanofiber mats were used for tensile testing, and they were also encased in polydimethylsiloxane to form composites that were also subsequently subjected to tensile testing. During tensile tests, the nanofibers can be damaged in stretching up to the plastic regime of deformation. Then, the resin monomer and cure was released from the cores and the polydimethylsiloxane resin was polymerized, which might be expected to result in the self-healing properties of these materials. To reveal and evaluate the self-healing properties of the polyacrylonitrile-resin-cure nanofiber mats and their composites, the results were compared to the tensile test results of the monolithic polyacrylonitrile nanofiber mats or composites formed by encasing polyacrylonitrile nanofibers in a polydimethylsiloxane matrix. The latter do not possess self-healing properties, and indeed, do not recover their mechanical characteristics, in contrast to the polyacrylonitrile-resin-cure nanofiber mats and the composites reinforced by such mats. This is the first work, to the best of our knowledge, where self-healing nanofibers and composites based on them were developed, tested, and revealed restoration of mechanical properties (stiffness) in a 24 h rest period at room temperature.

Advanced composites: Fabrication processes for selected resin matrix materials

NASA Technical Reports Server (NTRS)

Welhart, E. K.

1976-01-01

This design note is based on present state of the art for epoxy and polyimide matrix composite fabrication technology. Boron/epoxy and polyimide and graphite/epoxy and polyimide structural parts can be successfully fabricated. Fabrication cycles for polyimide matrix composites have been shortened to near epoxy cycle times. Nondestructive testing has proven useful in detecting defects and anomalies in composite structure elements. Fabrication methods and tooling materials are discussed along with the advantages and disadvantages of different tooling materials. Types of honeycomb core, material costs and fabrication methods are shown in table form for comparison. Fabrication limits based on tooling size, pressure capabilities and various machining operations are also discussed.

Damage monitoring of aircraft structures made of composite materials using wavelet transforms

NASA Astrophysics Data System (ADS)

Molchanov, D.; Safin, A.; Luhyna, N.

2016-10-01

The present article is dedicated to the study of the acoustic properties of composite materials and the application of non-destructive testing methods to aircraft components. A mathematical model of a wavelet transformed signal is presented. The main acoustic (vibration) properties of different composite material structures were researched. Multiple vibration parameter dependencies on the noise reduction factor were derived. The main steps of a research procedure and new method algorithm are presented. The data obtained was compared with the data from a three dimensional laser-Doppler scanning vibrometer, to validate the results. The new technique was tested in the laboratory and on civil aircraft at a training airfield.

Mechanical Properties of Composite Waste Material Based Styrofoam, Baggase and Eggshell Powder for Application of Drone Frames

NASA Astrophysics Data System (ADS)

Perdana, Mastariyanto; Prastiawan; Hadi, Syafrul

2017-12-01

The garbage issue becomes a very serious problem at the moment. Much research has been done to make waste into useful materials. One of the utilization of waste is as the basic material of composite material that can be applied in the field of engineering. Some of the wastes generated are styrofoam, bagasse and eggshell. Styrofoam, bagasse and eggshell can be applied to a composite material. Styrofoam serves as a composite binder material while the bagasse and eggshells serve as a reinforcement. Volume fraction between styrofoam, bagasse and eggshell are 80%:10%:10%, 70%:15%:15%, 60%:20%:20%, and 50%:25%:25%. The aims of research are determine the mechanical properties of composite material based waste materials from styrofoam, bagasse and eggshell. Mechanical properties tested in this study are bending strength and toughness of composite materials. The results showed bending strength of composite for each volume fraction of 80%:10%:10%, 70%:15%:15%, 60%:20%:20%, and 50%:25%:25% are 5.07 MPa, 8.45 MPa, 8.68 MPa, and 11.01 MPa, respectively. Toughness of composite materials for each volume fraction of 80%:10%:10%, 70%:15%:15%, 60%:20%:20%, and 50%:25%:25% are 0.33 J/mm2, 0.42 J/mm2, 0.75 J/mm2, and 0.75 J/mm2, respectively. Composite materials based on waste materials from styrofoam, bagasse and eggshell can be used as an alternative material for drone frames.

Study of the time varying properties of flax fiber reinforced composites

NASA Astrophysics Data System (ADS)

Stochioiu, Constantin; Chettah, Ameur; Piezel, Benoit; Fontaine, Stéphane; Gheorghiu, Horia-Miron

2018-02-01

Bio materials have seen an increase of interest from the scientific community and the industry as a possible future generation of mass produced materials, some of the main arguments being their renewability, low production costs and recyclability. The current work is focused on the experimental data required for the viscoelastic characterization of a composite material. Similar work has been conducted on different types of composite materials by Tuttle and Brinson [1] who verified for a carbon epoxy laminate the possibility of long term predicament of creep. Nordin et al [2] studied paper impregnated with phenol-formaldehyde under compression. Muliana [3] conducted experiments on E-glass/vinyl ester materials. Behavior characterization was based on a model presented by Schapery [4]. The main objective of this work is to understand the mechanical behaviors of bio-laminates structures subjected to long and severe operating conditions. The studied material is a bio composite laminate consisting in long flax fibers embedded in an epoxy resin system. The laminates were obtained from pre-impregnated unidirectional fibers, which were cured though a thermo-compression cycle followed by a post curing cycle. Test specimens were cut down to sizes, with the help of an electric saw. The concerned fiber direction was 0° with sample dimensions of 250x25x2 mm. First, testing consisted in quasi static mechanical tests. Second, to characterize linear viscoelastic behavior of the bio-laminates, creep - recovery tests with multiple load levels have been performed for the chosen fiber direction.

Repairability of CAD/CAM high-density PMMA- and composite-based polymers.

PubMed

Wiegand, Annette; Stucki, Lukas; Hoffmann, Robin; Attin, Thomas; Stawarczyk, Bogna

2015-11-01

The study aimed to analyse the shear bond strength of computer-aided design and computer-aided manufacturing (CAD/CAM) polymethyl methacrylate (PMMA)- and composite-based polymer materials repaired with a conventional methacrylate-based composite after different surface pretreatments. Each 48 specimens was prepared from six different CAD/CAM polymer materials (Ambarino high-class, artBloc Temp, CAD-Temp, Lava Ultimate, Telio CAD, Everest C-Temp) and a conventional dimethacrylate-based composite (Filtek Supreme XTE, control) and aged by thermal cycling (5000 cycles, 5-55 °C). The surfaces were left untreated or were pretreated by mechanical roughening, aluminium oxide air abrasion or silica coating/silanization (each subgroup n = 12). The surfaces were further conditioned with an etch&rinse adhesive (OptiBond FL) before the repair composite (Filtek Supreme XTE) was adhered to the surface. After further thermal cycling, shear bond strength was tested, and failure modes were assessed. Shear bond strength was statistically analysed by two- and one-way ANOVAs and Weibull statistics, failure mode by chi(2) test (p ≤ 0.05). Shear bond strength was highest for silica coating/silanization > aluminium oxide air abrasion = mechanical roughening > no surface pretreatment. Independently of the repair pretreatment, highest bond strength values were observed in the control group and for the composite-based Everest C-Temp and Ambarino high-class, while PMMA-based materials (artBloc Temp, CAD-Temp and Telio CAD) presented significantly lowest values. For all materials, repair without any surface pretreatment resulted in adhesive failures only, which mostly were reduced when surface pretreatment was performed. Repair of CAD/CAM high-density polymers requires surface pretreatment prior to adhesive and composite application. However, four out of six of the tested CAD/CAM materials did not achieve the repair bond strength of a conventional dimethacrylate-based composite. Repair of PMMA- and composite-based polymers can be achieved by surface pretreatment followed by application of an adhesive and a conventional methacrylate-based composite.

Blade System Design Study. Part II, final project report (GEC).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Griffin, Dayton A.

2009-05-01

As part of the U.S. Department of Energy's Low Wind Speed Turbine program, Global Energy Concepts LLC (GEC)1 has studied alternative composite materials for wind turbine blades in the multi-megawatt size range. This work in one of the Blade System Design Studies (BSDS) funded through Sandia National Laboratories. The BSDS program was conducted in two phases. In the Part I BSDS, GEC assessed candidate innovations in composite materials, manufacturing processes, and structural configurations. GEC also made recommendations for testing composite coupons, details, assemblies, and blade substructures to be carried out in the Part II study (BSDS-II). The BSDS-II contract periodmore » began in May 2003, and testing was initiated in June 2004. The current report summarizes the results from the BSDS-II test program. Composite materials evaluated include carbon fiber in both pre-impregnated and vacuum-assisted resin transfer molding (VARTM) forms. Initial thin-coupon static testing included a wide range of parameters, including variation in manufacturer, fiber tow size, fabric architecture, and resin type. A smaller set of these materials and process types was also evaluated in thin-coupon fatigue testing, and in ply-drop and ply-transition panels. The majority of materials used epoxy resin, with vinyl ester (VE) resin also used for selected cases. Late in the project, testing of unidirectional fiberglass was added to provide an updated baseline against which to evaluate the carbon material performance. Numerous unidirectional carbon fabrics were considered for evaluation with VARTM infusion. All but one fabric style considered suffered either from poor infusibility or waviness of fibers combined with poor compaction. The exception was a triaxial carbon-fiberglass fabric produced by SAERTEX. This fabric became the primary choice for infused articles throughout the test program. The generally positive results obtained in this program for the SAERTEX material have led to its being used in innovative prototype blades of 9-m and 30-m length, as well as other non-wind related structures.« less

Chemical Stability of Bioglass in Simulated Oral Environment.

PubMed

Sm, Moazzami; R, Sadid Zadeh; K, Kianoush; M, Sarmad; F, Barani Karbaski; R, Amiri Daluyi; Rb, Kazemi

2016-09-01

Bioglasses are a series of biocompatible dental materials, which are considered as light conducting inserts in resin composite restorations. Consequently, their chemical stability is more essential when they are used in conjunction with resin composite. The aim of this study was to evaluate and compare the chemical stability of Bioglass with dental porcelain and resin composite by determining the amount of released K+, Na+, Ca2+ ions and silicone elements from these materials as a result of exposure to tested solutions with different pH levels including: Sodium Bicarbonate [SB, (pH=9.2)], Sodium Buffer Lactate [SBL, (pH=2.4)], Acetic Acid [AA, (pH=2.4)], and Distilled Water [DW, (pH=6.2)]. In this experimental study, forty 2.0 × 4.0 cylindrical rods for each tested material group (Dental porcelain, Resin composite and Bioglass) were prepared. They were divided into four subgroups of 10 rods each, which immersed in one of the four testing solutions in a designated container. The containers were stored at 50°C and 100% humidity for one week. The released ions were measured by using a spectrophotometer (µg/cm 2 /ml). The data were statistically analyzed by nonparametric Kruskal-Wallis H test. It was observed that the tested materials released ions at different levels of concentration. The significant amounts of Sodium, Calcium, and Silicon ions release were measured in Bioglass subgroups in all the tested solutions ( p < 0.001). Potassium ion release from dental porcelain was the largest in all solutions except for AA in which Bioglass had the greatest potassium ion release ( p < 0.001). A greater structural instability was observed for Biogalss group than dental porcelain and resin composite in testing solutions with different pH levels.

Three-body wear of resin denture teeth with and without nanofillers.

PubMed

Stober, Thomas; Henninger, Moritz; Schmitter, Marc; Pritsch, Maria; Rammelsberg, Peter

2010-02-01

The wear behavior of newly developed denture teeth with nanofillers may be different from teeth with other chemical formulations. The purpose of this study was to examine the 3-body wear resistance of 11 different commercially available resin denture teeth. The materials tested were conventional (SR Orthotyp PE, Orthognath) and cross-linked acrylic resin teeth without inorganic fillers (Premium 8, SR Postaris DCL, Trubyte Portrait, Artiplus), composite resin teeth with inorganic fillers (SR Orthosit PE, Vitapan), and composite resin teeth (experimental materials) with inorganic nanofillers (NC Veracia Posterior, e-Ha, Mondial). Human enamel and a ceramic denture tooth (Lumin Vacuum) were used as reference materials. The 3-body wear test was performed in a wear machine developed by the Academic Center for Dentistry Amsterdam (ACTA), with millet suspension acting as an abrasive medium (n=10, test load: 15 N, slip rate: 20%, number of cycles: 100,000). Wear was determined with the aid of a profilometer. Data were analyzed with the Kruskal-Wallis test and Mann-Whitney U test using the closed testing approach (significance level for familywise error rate, alpha=.05). None of the acrylic and composite resin materials tested in this study demonstrated the 3-body wear resistance of ceramic teeth or human enamel. Teeth with inorganic fillers demonstrated significantly lower wear values than conventional or cross-linked acrylic resin teeth without fillers. Composite resin teeth with traditional fillers showed significantly lower wear than composite resin teeth with nanofillers. Denture teeth with and without inorganic fillers differed significantly with regard to the degree of wear generated in the ACTA wear simulator. The incorporation of nanofillers did not improve the wear resistance compared to teeth with traditional fillers.

Volume imaging NDE and serial sectioning of carbon fiber composites

NASA Astrophysics Data System (ADS)

Hakim, Issa; Schumacher, David; Sundar, Veeraraghavan; Donaldson, Steven; Creuz, Aline; Schneider, Rainer; Keller, Juergen; Browning, Charles; May, Daniel; Ras, Mohamad Abo; Meyendorf, Norbert

2018-04-01

A composite material is a combination of two or more materials with very different mechanical, thermal and electrical properties. The various forms of composite materials, due to their high material properties, are widely used as structural materials in the aviation, space, marine, automobile, and sports industries. However, some defects like voids, delamination, or inhomogeneous fiber distribution that form during the fabricating processes of composites can seriously affect the mechanical properties of the composite material. In this study, several imaging NDE techniques such as: thermography, high frequency eddy current, ultrasonic, x-ray radiography, x-ray laminography, and high resolution x-ray CT were conducted to characterize the microstructure of carbon fiber composites. Then, a 3D analysis was implemented by the destructive technique of serial sectioning for the same sample tested by the NDE methods. To better analyze the results of this work and extract a clear volume image for all features and defects contained in the composite material, an intensive comparison was conducted among hundreds of 3D-NDE and multi serial sections' scan images showing the microstructure variation.

Carbon Fiber Reinforced Ceramic Composites for Propulsion Applications

NASA Technical Reports Server (NTRS)

Freedman, Marc (Technical Monitor); Shivakumar, Kunigal N.

2003-01-01

Fiber reinforced ceramic composites are materials of choice for gas turbine engines because of their high thermal efficiency, thrust/weight ratio, and operating temperatures. However, the successful introduction of ceramic composites to hot structures is limited because of excessive cost of manufacturing, reproducibility, nonuniformity, and reliability. Intense research is going on around the world to address some of these issues. The proposed effort is to develop a comprehensive status report of the technology on processing, testing, failure mechanics, and environmental durability of carbon fiber reinforced ceramic composites through extensive literature study, vendor and end-user survey, visits to facilities doing this type of work, and interviews. Then develop a cooperative research plan between NASA GRC and NCA&T (Center for Composite Materials Research) for processing, testing, environmental protection, and evaluation of fiber reinforced ceramic composites.

Kevlar 49/Epoxy COPV Aging Evaluation

NASA Technical Reports Server (NTRS)

Sutter, James K.; Salem, Jonathan L.; Thesken, John C.; Russell, Richard W.; Littell, Justin; Ruggeri, Charles; Leifeste, Mark R.

2008-01-01

NASA initiated an effort to determine if the aging of Kevlar 49/Epoxy composite overwrapped pressure vessels (COPV) affected their performance. This study briefly reviews the history and certification of composite pressure vessels employed on NASA Orbiters. Tests to evaluate overwrap tensile strength changes compared 30 year old samples from Orbiter vessels to new Kevlar/Epoxy pressure vessel materials. Other tests include transverse compression and thermal analyses (glass transition and moduli). Results from these tests do not indicate a noticeable effect due to aging of the overwrap materials.

Design, ancillary testing, analysis and fabrication data for the advanced composite stabilizer for Boeing 737 aircraft, volume 2

NASA Technical Reports Server (NTRS)

Aniversario, R. B.; Harvey, S. T.; Mccarty, J. E.; Parsons, J. T.; Peterson, D. C.; Pritchett, L. D.; Wilson, D. R.; Wogulis, E. R.

1982-01-01

Results of tests conducted to demonstrate that composite structures save weight, possess long term durability, and can be fabricated at costs competitive with conventional metal structures are presented with focus on the use of graphite-epoxy in the design of a stabilizer for the Boeing 737 aircraft. Component definition, materials evaluation, material design properties, and structural elements tests are discussed. Fabrication development, as well as structural repair and inspection are also examined.

Evaluation of mechanical and optical behavior of current esthetic dental restorative CAD/CAM composites.

PubMed

Stawarczyk, Bogna; Liebermann, Anja; Eichberger, Marlis; Güth, Jan-Frederik

2015-03-01

To determine the mechanical and optical properties of CAD/CAM composites (LAVA Ultimate, Cerasmart, Shofu Block and two exp. CAD/CAM composites), a hybrid material (VITA Enamic), a leucite (IPS Empress CAD) and a lithium disilicate glass-ceramic (IPS e.max CAD). Three-point flexural strength (FS) was investigated according ISO 6872:2008 (N=240/n=30). Two-body wear (TBW) was analyzed in a chewing simulator (1,200,000 cycles, 50N, 5°/55°C) using human teeth as antagonists (N=120/n=15). Quantitative analysis of wear was carried out with a 3D-scanner and associated matching software. Discoloration rate (DR) after 14 days of storage in cress, curry, red wine, and distilled water (N=384/n=12), and translucency (T) (N=384/n=48) of CAD/CAM materials were measured in a spectrophotometer (400-700nm wavelength). Data were analyzed using two-/one-way ANOVA with Scheffé post-hoc test, Kruskal-Wallis-H test, and linear mixed models (α=0.05). IPS e.max CAD showed the highest FS (p<0.001), followed by LAVA Ultimate; however, not different from the remaining CAD/CAM composites (exception: Shofu Block). The lowest FS showed VITA Enamic and IPS Empress CAD (p<0.001). IPS Empress CAD, VITA Enamic, exp. CAD/CAM composite 2, followed by IPS e.max presented lower material TBW than the remaining CAD/CAM materials (p<0.001). The highest antagonist wear was observed for the tested glass-ceramics and the hybrid material (p<0.001). Storage medium (red wine>curry>cress>distilled water) exerted the highest influence on DR (p<0.001), closely followed by CAD/CAM material. Glass-ceramics showed lower DR than CAD/CAM composites (p<0.001). CAD/CAM composites presented moderate FS, high T and antagonist friendly behavior. Glass-ceramic demonstrated the most favorable DR and lowest TBW on the material side. Copyright © 2015 Elsevier Ltd. All rights reserved.

A geochemical approach to constraining the formation of glassy fallout debris from nuclear tests

DOE PAGES

Bonamici, Chloë E.; Kinman, William S.; Fournelle, John H.; ...

2016-12-15

Reprocessed earth material is a glassy nuclear fallout debris from near-surface nuclear tests. A geochemical approach to analysis of glassy fallout is uniquely suited to determine the means of reprocessing and shed light on the mechanisms of fallout formation. An improved understanding of fallout formation is of interest both for its potential to guide post-detonation nuclear forensic investigations and in the context of possible affinities between glassy debris and other glasses generated by high-energy natural events, such as meteorite impacts and lightning strikes. Our study presents a large major-element compositional dataset for glasses within aerodynamic fallout from the Trinity nuclearmore » test (“trinitite”) and a geochemically based analysis of the glass compositional trends. Silica-rich and alkali-rich trinitite glasses show compositions and textures consistent with formation through melting of individual mineral grains—quartz and alkali feldspar, respectively—from the test-site sediment. Furthermore, the volumetrically dominant glass phase—called the CaMgFe glass—shows extreme major-element compositional variability. Compositional trends in the CaMgFe glass are most consistent with formation through volatility-controlled condensation from compositionally heterogeneous plasma. Radioactivity occurs only in CaMgFe glass, indicating that co-condensation of evaporated bulk ground material and trace device material was the main mechanism of radioisotope incorporation into trinitite. CaMgFe trinitite glasses overlap compositionally with basalts, rhyolites, fulgurites, tektites, and microtektites but display greater compositional diversity than all of these naturally formed glasses. Indeed, the most refractory CaMgFe glasses compositionally resemble early solar system condensates—specifically, CAIs.« less

A geochemical approach to constraining the formation of glassy fallout debris from nuclear tests

NASA Astrophysics Data System (ADS)

Bonamici, Chloë E.; Kinman, William S.; Fournelle, John H.; Zimmer, Mindy M.; Pollington, Anthony D.; Rector, Kirk D.

2017-01-01

Glassy nuclear fallout debris from near-surface nuclear tests is fundamentally reprocessed earth material. A geochemical approach to analysis of glassy fallout is uniquely suited to determine the means of reprocessing and shed light on the mechanisms of fallout formation. An improved understanding of fallout formation is of interest both for its potential to guide post-detonation nuclear forensic investigations and in the context of possible affinities between glassy debris and other glasses generated by high-energy natural events, such as meteorite impacts and lightning strikes. This study presents a large major-element compositional dataset for glasses within aerodynamic fallout from the Trinity nuclear test ("trinitite") and a geochemically based analysis of the glass compositional trends. Silica-rich and alkali-rich trinitite glasses show compositions and textures consistent with formation through melting of individual mineral grains—quartz and alkali feldspar, respectively—from the test-site sediment. The volumetrically dominant glass phase—called the CaMgFe glass—shows extreme major-element compositional variability. Compositional trends in the CaMgFe glass are most consistent with formation through volatility-controlled condensation from compositionally heterogeneous plasma. Radioactivity occurs only in CaMgFe glass, indicating that co-condensation of evaporated bulk ground material and trace device material was the main mechanism of radioisotope incorporation into trinitite. CaMgFe trinitite glasses overlap compositionally with basalts, rhyolites, fulgurites, tektites, and microtektites but display greater compositional diversity than all of these naturally formed glasses. Indeed, the most refractory CaMgFe glasses compositionally resemble early solar system condensates—specifically, CAIs.

Design, Static Analysis And Fabrication Of Composite Joints

NASA Astrophysics Data System (ADS)

Mathiselvan, G.; Gobinath, R.; Yuvaraja, S.; Raja, T.

2017-05-01

The Bonded joints will be having one of the important issues in the composite technology is the repairing of aging in aircraft applications. In these applications and also for joining various composite material parts together, the composite materials fastened together either using adhesives or mechanical fasteners. In this paper, we have carried out design, static analysis of 3-D models and fabrication of the composite joints (bonded, riveted and hybrid). The 3-D model of the composite structure will be fabricated by using the materials such as epoxy resin, glass fibre material and aluminium rivet for preparing the joints. The static analysis was carried out with different joint by using ANSYS software. After fabrication, parametric study was also conducted to compare the performance of the hybrid joint with varying adherent width, adhesive thickness and overlap length. Different joint and its materials tensile test result have compared.

Mechanical properties of neat polymer matrix materials and their unidirectional carbon fiber-reinforced composites

NASA Technical Reports Server (NTRS)

Zimmerman, Richard S.; Adams, Donald F.

1988-01-01

The mechanical properties of two neat resin systems for use in carbon fiber epoxy composites were characterized. This included tensile and shear stiffness and strengths, coefficients of thermal and moisture expansion, and fracture toughness. Tests were conducted on specimens in the dry and moisture-saturated states, at temperatures of 23, 82 and 121 C. The neat resins tested were American Cyanamid 1806 and Union Carbide ERX-4901B(MPDA). Results were compared to previously tested neat resins. Four unidirectional carbon fiber reinforced composites were mechanically characterized. Axial and transverse tension and in-plane shear strengths and stiffness were measured, as well as transverse coefficients of thermal and moisture expansion. Tests were conducted on dry specimens only at 23 and 100 C. The materials tested were AS4/3502, AS6/5245-C, T300/BP907, and C6000/1806 unidirectional composites. Scanning electron microscopic examination of fracture surfaces was performed to permit the correlation of observed failure modes with the environmental test conditions.

Acoustic emission monitoring of polymer composite materials

NASA Technical Reports Server (NTRS)

Bardenheier, R.

1981-01-01

The techniques of acoustic emission monitoring of polymer composite materials is described. It is highly sensitive, quasi-nondestructive testing method that indicates the origin and behavior of flaws in such materials when submitted to different load exposures. With the use of sophisticated signal analysis methods it is possible the distinguish between different types of failure mechanisms, such as fiber fracture delamination or fiber pull-out. Imperfections can be detected while monitoring complex composite structures by acoustic emission measurements.

Comparative study of mechanical properties of direct core build-up materials

PubMed Central

Kumar, Girish; Shivrayan, Amit

2015-01-01

Background and Objectives: The strength greatly influences the selection of core material because core must withstand forces due to mastication and para-function for many years. This study was conducted to evaluate certain mechanical properties of commonly used materials for direct core build-up, including visible light cured composite, polyacid modified composite, resin modified glass ionomer, high copper amalgam, and silver cermet cement. Materials and Methods: All the materials were manipulated according to the manufacturer's recommendations and standard test specimens were prepared. A universal testing machine at different cross-head speed was used to determine all the four mechanical properties. Mean compressive strength, diametral tensile strength, flexural strength, and elastic modulus with standard deviations were calculated. Multiple comparisons of the materials were also done. Results: Considerable differences in compressive strength, diametral tensile strength, and flexural strength were observed. Visible light cured composite showed relatively high compressive strength, diametral tensile strength, and flexural strength compared with the other tested materials. Amalgam showed the highest value for elastic modulus. Silver cermet showed less value for all the properties except for elastic modulus. Conclusions: Strength is one of the most important criteria for selection of a core material. Stronger materials better resist deformation and fracture provide more equitable stress distribution, greater stability, and greater probability of clinical success. PMID:25684905

Fire test method for graphite fiber reinforced plastics

NASA Technical Reports Server (NTRS)

Bowles, K. J.

1980-01-01

A potential problem in the use of graphite fiber reinforced resin matrix composites is the dispersal of graphite fibers during accidential fires. Airborne, electrically conductive fibers originating from the burning composites could enter and cause shorting in electrical equipment located in surrounding areas. A test method for assessing the burning characteristics of graphite fiber reinforced composites and the effectiveness of the composites in retaining the graphite fibers has been developed. The method utilizes a modified rate of heat release apparatus. The equipment and the testing procedure are described. The application of the test method to the assessment of composite materials is illustrated for two resin matrix/graphite composite systems.

Effect of short-term water storage on the elastic properties of some dental restorative materials--A resonant ultrasound spectroscopy study.

PubMed

Pastila, Pirjo; Lassila, Lippo V J; Jokinen, Mikko; Vuorinen, Jyrki; Vallittu, Pekka K; Mäntylä, Tapio

2007-07-01

This study was aimed to determine if short-term water storage would change elastic properties of dental composite materials. Particulate filler composite resin and continuous unidirectional E-glass FRC materials were photopolymerized and additionally post-polymerized by heat for testing elastic properties with the Resonance Ultrasound Spectroscopy method as a function of time in water storage. The test specimens were stored in 37 degrees C water for up to 30 days. About 1% weight increase due to water sorption was observed in both materials with both polymerization methods. Water sorption did not change the resonance frequencies towards lower values, indicating no significant decrease in elastic properties in these materials. Because of high damping of the polymer composite materials leading to wide resonance peaks and low number of the recorded peaks, accurate determination of the elastic properties was not possible. Results suggest that the most likely explanation for the previously observed decrease in bending stiffness of FRC materials is the decreased yield limit of the hydrated polymer matrix. It is important to recognize that water sorption has the effect on mechanical properties of dental composite materials by changing the yield limit of the matrix rather than by changing the elastic properties of the material.

Porous composite with negative thermal expansion obtained by photopolymer additive manufacturing

NASA Astrophysics Data System (ADS)

Takezawa, Akihiro; Kobashi, Makoto; Kitamura, Mitsuru

2015-07-01

Additive manufacturing (AM) could be a novel method of fabricating composite and porous materials having various effective performances based on mechanisms of their internal geometries. Materials fabricated by AM could rapidly be used in industrial application since they could easily be embedded in the target part employing the same AM process used for the bulk material. Furthermore, multi-material AM has greater potential than usual single-material AM in producing materials with effective properties. Negative thermal expansion is a representative effective material property realized by designing a composite made of two materials with different coefficients of thermal expansion. In this study, we developed a porous composite having planar negative thermal expansion by employing multi-material photopolymer AM. After measurement of the physical properties of bulk photopolymers, the internal geometry was designed by topology optimization, which is the most effective structural optimization in terms of both minimizing thermal stress and maximizing stiffness. The designed structure was converted to a three-dimensional stereolithography (STL) model, which is a native digital format of AM, and assembled as a test piece. The thermal expansions of the specimens were measured using a laser scanning dilatometer. Negative thermal expansion corresponding to less than -1 × 10-4 K-1 was observed for each test piece of the N = 3 experiment.

Synthesis, Characterization and Applications of Ethyl Cellulose-Based Polymeric Calcium(II) Hydrogen Phosphate Composite

NASA Astrophysics Data System (ADS)

Mohammad, Faruq; Arfin, Tanvir; Al-Lohedan, Hamad A.

2018-03-01

The present report deals with the synthesis, characterization and testing of an ethyl cellulose-calcium(II) hydrogen phosphate (EC-CaHPO4) composite, where a sol-gel synthesis method was applied for the preparation of the composite so as to test its efficacy towards the electrochemical, biological, and adsorption related applications. The physical properties of the composite were characterized by using scanning electron microscopy (SEM), ultraviolet- visible (UV-Vis) spectroscopy, and fourier transform-infrared (FTIR) spectroscopy. On testing, the mechanical properties indicated that the composite is highly stable due to the cross-linked rigid framework and the enhanced interactions offered by the EC polymer supported for its binding very effectively. In addition, the conductivity of EC-CaHPO4 is completely governed by the transport mechanism where the electrolyte concentration has preference towards the adsorption of ions and the variations in the conductivity significantly affected the material's performance. We observed an increasing order of KCl > NaCl for the conductivity when 1:1 electrolytes were applied. Further, the material was tested for its usefulness towards the purification of industrial waste waters by removing harmful metal ions from the samples collected near the Aligarh city, India where the data indicates that the material has highest affinity towards Pb2+, Cu2+, Ni2+ and Fe3+ metal ions. Finally, the biological efficiency of the material was confirmed by means of testing the antibacterial activity against two gram positive (staphylococcus aureus and Bacillus thuringiensis) and two gram negative bacteriums (Pseudomonas aeruginosa and Patoea dispersa). Thus, from the cumulative study of outcomes, it indicates that the EC-CaHPO4 composite found to serve as a potential smart biomaterial due to its efficiency in many different applications that includes the electrical conductivity, adsorption capability, and antimicrobial activity.

ASTM and VAMAS activities in titanium matrix composites test methods development

NASA Technical Reports Server (NTRS)

Johnson, W. S.; Harmon, D. M.; Bartolotta, P. A.; Russ, S. M.

1994-01-01

Titanium matrix composites (TMC's) are being considered for a number of aerospace applications ranging from high performance engine components to airframe structures in areas that require high stiffness to weight ratios at temperatures up to 400 C. TMC's exhibit unique mechanical behavior due to fiber-matrix interface failures, matrix cracks bridged by fibers, thermo-viscoplastic behavior of the matrix at elevated temperatures, and the development of significant thermal residual stresses in the composite due to fabrication. Standard testing methodology must be developed to reflect the uniqueness of this type of material systems. The purpose of this paper is to review the current activities in ASTM and Versailles Project on Advanced Materials and Standards (VAMAS) that are directed toward the development of standard test methodology for titanium matrix composites.

Effect of Load Rate on Ultimate Tensile Strength of Ceramic Matrix Composites at Elevated Temperatures

NASA Technical Reports Server (NTRS)

Choi, Sung R.; Gyekenyesi, John P.

2001-01-01

The strengths of three continuous fiber-reinforced ceramic composites, including SiC/CAS-II, SiC/MAS-5 and SiC/SiC, were determined as a function of test rate in air at 1100 to 1200 C. All three composite materials exhibited a strong dependency of strength on test rate, similar to the behavior observed in many advanced monolithic ceramics at elevated temperatures. The application of the preloading technique as well as the prediction of life from one loading configuration (constant stress-rate) to another (constant stress loading) suggested that the overall macroscopic failure mechanism of the composites would be the one governed by a power-law type of damage evolution/accumulation, analogous to slow crack growth commonly observed in advanced monolithic ceramics. It was further found that constant stress-rate testing could be used as an alternative to life prediction test methodology even for composite materials, at least for short range of lifetimes and when ultimate strength is used as the failure criterion.

Pulse Power Capability Of High Energy Density Capacitors Based on a New Dielectric Material

NASA Technical Reports Server (NTRS)

Winsor, Paul; Scholz, Tim; Hudis, Martin; Slenes, Kirk M.

1999-01-01

A new dielectric composite consisting of a polymer coated onto a high-density metallized Kraft has been developed for application in high energy density pulse power capacitors. The polymer coating is custom formulated for high dielectric constant and strength with minimum dielectric losses. The composite can be wound and processed using conventional wound film capacitor manufacturing equipment. This new system has the potential to achieve 2 to 3 J/cu cm whole capacitor energy density at voltage levels above 3.0 kV, and can maintain its mechanical properties to temperatures above 150 C. The technical and manufacturing development of the composite material and fabrication into capacitors are summarized in this paper. Energy discharge testing, including capacitance and charge-discharge efficiency at normal and elevated temperatures, as well as DC life testing were performed on capacitors manufactured using this material. TPL (Albuquerque, NM) has developed the material and Aerovox (New Bedford, MA) has used the material to build and test actual capacitors. The results of the testing will focus on pulse power applications specifically those found in electro-magnetic armor and guns, high power microwave sources and defibrillators.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gregory Corman; Krishan Luthra

This report covers work performed under the Continuous Fiber Ceramic Composites (CFCC) program by GE Global Research and its partners from 1994 through 2005. The processing of prepreg-derived, melt infiltrated (MI) composite systems based on monofilament and multifilament tow SiC fibers is described. Extensive mechanical and environmental exposure characterizations were performed on these systems, as well as on competing Ceramic Matrix Composite (CMC) systems. Although current monofilament SiC fibers have inherent oxidative stability limitations due to their carbon surface coatings, the MI CMC system based on multifilament tow (Hi-Nicalon ) proved to have excellent mechanical, thermal and time-dependent properties. Themore » materials database generated from the material testing was used to design turbine hot gas path components, namely the shroud and combustor liner, utilizing the CMC materials. The feasibility of using such MI CMC materials in gas turbine engines was demonstrated via combustion rig testing of turbine shrouds and combustor liners, and through field engine tests of shrouds in a 2MW engine for >1000 hours. A unique combustion test facility was also developed that allowed coupons of the CMC materials to be exposed to high-pressure, high-velocity combustion gas environments for times up to {approx}4000 hours.« less

On the Constitutive Response Characterization for Composite Materials Via Data-Driven Design Optimization

Treesearch

John G. Michopoulos; John G. Hermanson; Athanasios lliopoulos; Samuel Lambrakos; Tomonari Furukawa

2011-01-01

In the present paper we focus on demonstrating the use of design optimization for the constitutive characterization of anisotropic material systems such as polymer matrix composites, with or without damage. All approaches are based on the availability of experimental data originating from mechatronic material testing systems that can expose specimens to...

Progress in composite structure and space construction systems technology

NASA Technical Reports Server (NTRS)

Bodle, J. B.; Jenkins, L. M.

1981-01-01

The development of deployable and fabricated composite trusses for large space structures by NASA and private industry is reviewed. Composite materials technology is discussed with a view toward fabrication processes and the characteristics of finished truss beams. Advances in roll-forming open section caps from graphite-composite strip material and new ultrasonic welding techniques are outlined. Vacuum- and gravity-effect test results show that the ultrasonic welding of graphite-thermoplastic materials in space is feasible. The structural characteristics of a prototype truss segment are presented. A new deployable graphite-composite truss with high packaging density for broad application to large space platforms is described.

High Volume Fraction Carbon Nanotube Composites for Aerospace Applications

NASA Technical Reports Server (NTRS)

Siochi, E. J.; Kim, J.-W.; Sauti, G.; Cano, R. J.; Wincheski, R. A.; Ratcliffe, J. G.; Czabaj, M.

2016-01-01

Reported mechanical properties of carbon nanotubes (CNTs) at the nanoscale suggest their potential to enable significantly lighter structures of interest for space applications. However, their utility depends on the retention of these properties in bulk material formats that permit practical fabrication of large structures. This presentation summarizes recent progress made to produce carbon nanotube composites with specific tensile properties that begin to rival those of carbon fiber reinforced polymer composites. CNT content in these nanocomposites was greater than 70% by weight. Tested nanocomposite specimens were fabricated from kilometers or tens of square meters of CNT, depending on the starting material format. Processing methods to yield these results, and characterization and testing to evaluate the performance of these composites will be discussed. The final objective is the demonstration of a CNT composite overwrapped pressure vessel to be flight tested in the Fall of 2016.

Surface hardness evaluation of different composite resin materials: influence of sports and energy drinks immersion after a short-term period

PubMed Central

ERDEMİR, Ugur; YİLDİZ, Esra; EREN, Meltem Mert; OZEL, Sevda

2013-01-01

Objectives: This study evaluated the effect of sports and energy drinks on the surface hardness of different composite resin restorative materials over a 1-month period. Material and Methods: A total of 168 specimens: Compoglass F, Filtek Z250, Filtek Supreme, and Premise were prepared using a customized cylindrical metal mould and they were divided into six groups (N=42; n=7 per group). For the control groups, the specimens were stored in distilled water for 24 hours at 37º C and the water was renewed daily. For the experimental groups, the specimens were immersed in 5 mL of one of the following test solutions: Powerade, Gatorade, X-IR, Burn, and Red Bull, for two minutes daily for up to a 1-month test period and all the solutions were refreshed daily. Surface hardness was measured using a Vickers hardness measuring instrument at baseline, after 1-week and 1-month. Data were statistically analyzed using Multivariate repeated measure ANOVA and Bonferroni's multiple comparison tests (α=0.05). Results: Multivariate repeated measures ANOVA revealed that there were statistically significant differences in the hardness of the restorative materials in different immersion times (p<0.001) in different solutions (p<0.001). The effect of different solutions on the surface hardness values of the restorative materials was tested using Bonferroni's multiple comparison tests, and it was observed that specimens stored in distilled water demonstrated statistically significant lower mean surface hardness reductions when compared to the specimens immersed in sports and energy drinks after a 1-month evaluation period (p<0.001). The compomer was the most affected by an acidic environment, whereas the composite resin materials were the least affected materials. Conclusions: The effect of sports and energy drinks on the surface hardness of a restorative material depends on the duration of exposure time, and the composition of the material. PMID:23739850

Material Property Characterization of Potential Nanocarbon Metal-Matrix Composite: An Investigational Study

NASA Astrophysics Data System (ADS)

Zavala, Mitchel

Metal-matrix composites (MMCs) are engineered combinations of two or more materials. Tailored properties are achieved by systematic combinations of different constituents. Specialized design and synthesis procedures allow unique sets of material properties in composites. Covetics are a new type of metal-matrix nano-composite (MMnC) material. These materials are formed from FCC metals which are super-saturated with up to 10 wt. % of activated nano-carbon powder. The idea is that the nano-carbon particles will enhance the material properties of the base metal matrix, however most of the physical and mechanical properties of covetics have not been well characterized. The foci of this study are to optimize the covetic casting synthesis process under controlled conditions, to understand and analyze the microstructures of the synthesized copper and aluminum covetic, to provide a thorough analysis of the chemical composition of the synthesized covetic materials, and to characterize physical and mechanical properties of both of these materials using meticulously prepared samples and test procedures.

Immediate versus one-month wet storage fatigue of restorative materials.

PubMed

Gladys, S; Braem, M; Van Meerbeek, B; Lambrechts, P; Vanherle, G

1998-03-01

Immediate finishing is a highly desirable property of restorative materials. In general, the resin composites, the polyacid-modified resin composites and resin-modified glass-ionomers are finished immediately after light-curing. For the conventional glass-ionomers a waiting period of 24 h is recommended. Therefore, the objective of this study was to investigate whether immediate finishing and application of cyclic loading under water spray on resin-modified glass-ionomers, a conventional glass-ionomer, a polyacid-modified resin composite and a resin composite are reflected in their Young's modulus and fatigue resistance after 1-month wet storage compared with a control group that could mature untroubled for 1 month. From this study, it could be concluded that there is a material-dependent response on immediate finishing. For the conventional glass-ionomer, the waiting period of 24 h is highly advisable. The resin composite suffered more than the other test materials. A second statement is that one must be cautious by the extrapolation of findings obtained on quasi static tests (Young's modulus) towards dynamic properties (flexural fatigue limit).

Degradable phosphate glass fiber reinforced polymer matrices: mechanical properties and cell response.

PubMed

Brauer, Delia S; Rüssel, Christian; Vogt, Sebastian; Weisser, Jürgen; Schnabelrauch, Matthias

2008-01-01

The development of biodegradable materials for internal fracture fixation is of great interest, as they would both eliminate the problem of stress shielding and obviate the need for a second operation to remove fixation devices. Preliminary investigations for the production of degradable fiber reinforced polymer composite materials are detailed. Composites were produced of phosphate invert glass fibers of the glass system P(2)O(5)-CaO-MgO-Na(2)O-TiO(2), which showed a low solubility in previous work. The fibers were embedded into a matrix of a degradable organic polymer network based on methacrylate-modified oligolactide. Fracture behavior, bending strength and elastic modulus were evaluated during 3-point bending tests and the fracture surface of the composites was investigated using a scanning electron microscope. Short-term biocompatibility was tested in an FDA/EtBr viability assay using MC3T3-E1 murine pre-osteoblast cells and showed a good cell compatibility of the composite materials. Results suggested that these composite materials are biocompatible and show mechanical properties which are of interest for the production of degradable bone fixation devices.

Cryogenic materials selection, availability, and cost considerations

NASA Technical Reports Server (NTRS)

Rush, H. F.

1983-01-01

The selection of structural alloys, composite materials, solder alloys, and filler materials for use in cryogenic models is discussed. In particular, materials testing programs conducted at Langley are described.

Corrosion assessment of refractory materials for high temperature waste vitrification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marra, J.C.; Congdon, J.W.; Kielpinski, A.L.

1995-11-01

A variety of vitrification technologies are being evaluated to immobilize radioactive and hazardous wastes following years of nuclear materials production throughout the Department of Energy (DOE) complex. The compositions and physical forms of these wastes are diverse ranging from inorganic sludges to organic liquids to heterogeneous debris. Melt and off-gas products can be very corrosive at the high temperatures required to melt many of these waste streams. Ensuring material durability is required to develop viable treatment processes. Corrosion testing of materials in some of the anticipated severe environments is an important aspect of the materials identification and selection process. Corrosionmore » coupon tests on typical materials used in Joule heated melters were completed using glass compositions with high salt contents. The presence of chloride in the melts caused the most severe attack. In the metal alloys, oxidation was the predominant corrosion mechanism, while in the tested refractory material enhanced dissolution of the refractory into the glass was observed. Corrosion testing of numerous different refractory materials was performed in a plasma vitrification system using a surrogate heterogeneous debris waste. Extensive corrosion was observed in all tested materials.« less

Review of Aircraft Crash Structural Response Research.

DTIC Science & Technology

1982-08-01

structures consisting of conventional built-up metallic construction and those consisting of advanced composite materials were of interest. The latter...increasing importance. Some recent theoretical and experimental studies of the behavior of composite - material structures subjected to severe static...dynamic, and/or impact conditions are noted. Such topics as crashworthiness testing ot composite fuselage structures, the impact resistance of graphite and

Testing an Impedance Non-destructive Method to Evaluate Steel-Fiber Concrete Samples

NASA Astrophysics Data System (ADS)

Komarkova, Tereza; Fiala, Pavel; Steinbauer, Miloslav; Roubal, Zdenek

2018-02-01

Steel-fiber reinforced concrete is a composite material characterized by outstanding tensile properties and resistance to the development of cracks. The concrete, however, exhibits such characteristics only on the condition that the steel fibers in the final, hardened composite have been distributed evenly. The current methods to evaluate the distribution and concentration of a fiber composite are either destructive or exhibit a limited capability of evaluating the concentration and orientation of the fibers. In this context, the paper discusses tests related to the evaluation of the density and orientation of fibers in a composite material. Compared to the approaches used to date, the proposed technique is based on the evaluation of the electrical impedance Z in the band close to the resonance of the sensor-sample configuration. Using analytically expressed equations, we can evaluate the monitored part of the composite and its density at various depths of the tested sample. The method employs test blocks of composites, utilizing the resonance of the measuring device and the measured sample set; the desired state occurs within the interval of between f=3 kHz and 400 kHz.

PMR Graphite Engine Duct Development

NASA Technical Reports Server (NTRS)

Stotler, C. L.; Yokel, S. A.

1989-01-01

The objective was to demonstrate the cost and weight advantages that could be obtained by utilizing the graphite/PMR15 material system to replace titanium in selected turbofan engine applications. The first component to be selected as a basis for evaluation was the outer bypass duct of the General Electric F404 engine. The operating environment of this duct was defined and then an extensive mechanical and physical property test program was conducted using material made by processing techniques which were also established by this program. Based on these properties, design concepts to fabricate a composite version of the duct were established and two complete ducts fabricated. One of these ducts was proof pressure tested and then run successfully on a factory test engine for over 1900 hours. The second duct was static tested to 210 percent design limit load without failure. An improved design was then developed which utilized integral composite end flanges. A complete duct was fabricated and successfully proof pressure tested. The net results of this effort showed that a composite version of the outer duct would be 14 percent lighter and 30 percent less expensive that the titanium duct. The other type of structure chosen for investigation was the F404 fan stator assembly, including the fan stator vanes. It was concluded that it was feasible to utilize composite materials for this type structure but that the requirements imposed by replacing an existing metal design resulted in an inefficient composite design. It was concluded that if composites were to be effectively used in this type structure, the design must be tailored for composite application from the outset.

The influence of matrix microstructure

NASA Astrophysics Data System (ADS)

Vyletel, G. M.; Allison, J. E.; Aken, D. C.

1993-11-01

The low-cycle and high-cycle fatigue behavior and cyclic response of naturally aged and artificially aged 2219/TiC/15p and unreinforced 2219 Al were investigated utilizing plastic strain-controlled and stress-controlled testing. The cyclic response of both the reinforced and un-reinforced materials was similar for all plastic strain amplitudes tested except that the saturation stress level for the composite was always greater than that of the unreinforced material. The cyclic response of the naturally aged materials exhibited cyclic hardening and, in some cases, cyclic softening, while the cyclic response for the artificially aged materials showed no evidence of either cyclic hardening or softening. The higher ductility of the unreinforced material made it more resistant to fatigue failure at high strains, and thus, at a given plastic strain, it had longer fatigue life. It should be noted that the tensile ductilities of the 2219/TiC/15p were significantly higher than those previously reported for 2XXX-series composites. During stress-controlled test-ing at stresses below 220 MPa, the presence of TiC particles lead to an improvement in fatigue life. Above 220 MPa, no influence of TiC reinforcement on fatigue life could be detected. In both the composite and unreinforced materials, the low-cycle and high-cycle fatigue lives were found to be virtually independent of matrix microstructure.

Advanced numerical models and material characterisation techniques for composite materials subject to impact and shock wave loading

NASA Astrophysics Data System (ADS)

Clegg, R. A.; White, D. M.; Hayhurst, C.; Ridel, W.; Harwick, W.; Hiermaier, S.

2003-09-01

The development and validation of an advanced material model for orthotropic materials, such as fibre reinforced composites, is described. The model is specifically designed to facilitate the numerical simulation of impact and shock wave propagation through orthotropic materials and the prediction of subsequent material damage. Initial development of the model concentrated on correctly representing shock wave propagation in composite materials under high and hypervelocity impact conditions [1]. This work has now been extended to further concentrate on the development of improved numerical models and material characterisation techniques for the prediction of damage, including residual strength, in fibre reinforced composite materials. The work is focussed on Kevlar-epoxy however materials such as CFRP are also being considered. The paper describes our most recent activities in relation to the implementation of advanced material modelling options in this area. These enable refined non-liner directional characteristics of composite materials to be modelled, in addition to the correct thermodynamic response under shock wave loading. The numerical work is backed by an extensive experimental programme covering a wide range of static and dynamic tests to facilitate derivation of model input data and to validate the predicted material response. Finally, the capability of the developing composite material model is discussed in relation to a hypervelocity impact problem.

The effects of simulated space environmental parameters on six commercially available composite materials

NASA Technical Reports Server (NTRS)

Funk, Joan G.; Sykes, George F., Jr.

1989-01-01

The effects of simulated space environmental parameters on microdamage induced by the environment in a series of commercially available graphite-fiber-reinforced composite materials were determined. Composites with both thermoset and thermoplastic resin systems were studied. Low-Earth-Orbit (LEO) exposures were simulated by thermal cycling; geosynchronous-orbit (GEO) exposures were simulated by electron irradiation plus thermal cycling. The thermal cycling temperature range was -250 F to either 200 F or 150 F. The upper limits of the thermal cycles were different to ensure that an individual composite material was not cycled above its glass transition temperature. Material response was characterized through assessment of the induced microcracking and its influence on mechanical property changes at both room temperature and -250 F. Microdamage was induced in both thermoset and thermoplastic advanced composite materials exposed to the simulated LEO environment. However, a 350 F cure single-phase toughened epoxy composite was not damaged during exposure to the LEO environment. The simuated GEO environment produced microdamage in all materials tested.

Combustion Gas Heating Tests of C/C Composites Coated with SiC Layer

NASA Astrophysics Data System (ADS)

Sato, Masaki; Moriya, Shin-ichi; Sato, Masahiro; Tadano, Makoto; Kusaka, Kazuo; Hasegawa, Keiichi; Kumakawa, Akinaga; Yoshida, Makoto

2008-02-01

In order to examine the applicability of carbon fiber/carbon matrix composites coated with a silicon carbide layer (C/C-SiCs) to an advanced nozzle for the future reusable rocket engines, two series of combustion gas heating tests were conducted using a small rocket combustor. In the first series of heating tests, five different kinds of C/C-SiCs were tested with specimens in the shape of a square plate for material screening. In the second series of heating tests, two selected C/C-SiCs were tested with specimens in the shape of a small nozzle. The effectiveness of an interlayer between a C/C composite and a SiC layer, which was introduced to improve the durability based on the concept of functionally graded materials (FGMs), can be observed. The typical damage mode was also pointed out in the results of heating test using the small nozzle specimens.

Mechanical properties of 2D and 3D braided textile composites

NASA Technical Reports Server (NTRS)

Norman, Timothy L.

1991-01-01

The purpose of this research was to determine the mechanical properties of 2D and 3D braided textile composite materials. Specifically, those designed for tension or shear loading were tested under static loading to failure to investigate the effects of braiding. The overall goal of the work was to provide a structural designer with an idea of how textile composites perform under typical loading conditions. From test results for unnotched tension, it was determined that the 2D is stronger, stiffer, and has higher elongation to failure than the 3D. It was also found that the polyetherether ketone (PEEK) resin system was stronger, stiffer, and had higher elongation at failure than the resin transfer molding (RTM) epoxy. Open hole tension tests showed that PEEK resin is more notch sensitive than RTM epoxy. Of greater significance, it was found that the 3D is less notch sensitive than the 2D. Unnotched compression tests indicated, as did the tension tests, that the 2D is stronger, stiffer, and has higher elongation at failure than the RTM epoxy. The most encouraging results were from compression after impact. The 3D braided composite showed a compression after impact failure stress equal to 92 percent of the unimpacted specimen. The 2D braided composite failed at about 67 percent of the unimpacted specimen. Higher damage tolerance is observed in textiles over conventional composite materials. This is observed in the results, especially in the 3D braided materials.

Material, process, and product design of thermoplastic composite materials

NASA Astrophysics Data System (ADS)

Dai, Heming

Thermoplastic composites made of polypropylene (PP) and E-glass fibers were investigated experimentally as well as theoretically for two new classes of product designs. The first application was for reinforcement of wood. Commingled PP/glass yarn was consolidated and bonded on wood panel using a tie layer. The processing parameters, including temperature, pressure, heating time, cooling time, bonding strength, and bending strength were tested experimentally and evaluated analytically. The thermoplastic adhesive interface was investigated with environmental scanning electron microscopy. The wood/composite structural design was optimized and evaluated using a Graphic Method. In the second application, we evaluated use of thermoplastic composites for explosion containment in an arrester. PP/glass yarn was fabricated in a sleeve form and wrapped around the arrester. After consolidation, the flexible composite sleeve forms a solid composite shell. The composite shell acts as a protection layer in a surge test to contain the fragments of the arrester. The manufacturing process for forming the composite shell was designed. Woven, knitted, and braided textile composite shells made of commingled PP/glass yarn were tested and evaluated. Mechanical performance of the woven, knitted, and braided composite shells was examined analytically. The theoretical predictions were used to verify the experimental results.

Composite Materials for Hazard Mitigation of Reactive Metal Hydrides.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pratt, Joseph William; Cordaro, Joseph Gabriel; Sartor, George B.

2012-02-01

In an attempt to mitigate the hazards associated with storing large quantities of reactive metal hydrides, polymer composite materials were synthesized and tested under simulated usage and accident conditions. The composites were made by polymerizing vinyl monomers using free-radical polymerization chemistry, in the presence of the metal hydride. Composites with vinyl-containing siloxane oligomers were also polymerized with and without added styrene and divinyl benzene. Hydrogen capacity measurements revealed that addition of the polymer to the metal hydride reduced the inherent hydrogen storage capacity of the material. The composites were found to be initially effective at reducing the amount of heatmore » released during oxidation. However, upon cycling the composites, the mitigating behavior was lost. While the polymer composites we investigated have mitigating potential and are physically robust, they undergo a chemical change upon cycling that makes them subsequently ineffective at mitigating heat release upon oxidation of the metal hydride. Acknowledgements The authors would like to thank the following people who participated in this project: Ned Stetson (U.S. Department of Energy) for sponsorship and support of the project. Ken Stewart (Sandia) for building the flow-through calorimeter and cycling test stations. Isidro Ruvalcaba, Jr. (Sandia) for qualitative experiments on the interaction of sodium alanate with water. Terry Johnson (Sandia) for sharing his expertise and knowledge of metal hydrides, and sodium alanate in particular. Marcina Moreno (Sandia) for programmatic assistance. John Khalil (United Technologies Research Corp) for insight into the hazards of reactive metal hydrides and real-world accident scenario experiments. Summary In an attempt to mitigate and/or manage hazards associated with storing bulk quantities of reactive metal hydrides, polymer composite materials (a mixture of a mitigating polymer and a metal hydride) were synthesized and tested under simulated usage and accident conditions. Mitigating the hazards associated with reactive metal hydrides during an accident while finding a way to keep the original capability of the active material intact during normal use has been the focus of this work. These composites were made by polymerizing vinyl monomers using free-radical polymerization chemistry, in the presence of the metal hydride, in this case a prepared sodium alanate (chosen as a representative reactive metal hydride). It was found that the polymerization of styrene and divinyl benzene could be initiated using AIBN in toluene at 70°C. The resulting composite materials can be either hard or brittle solids depending on the cross-linking density. Thermal decomposition of these styrene-based composite materials is lower than neat polystyrene indicating that the chemical nature of the polymer is affected by the formation of the composite. The char-forming nature of cross-linked polystyrene is low and therefore, not an ideal polymer for hazard mitigation. To obtain composite materials containing a polymer with higher char-forming potential, siloxane-based monomers were investigated. Four vinyl-containing siloxane oligomers were polymerized with and without added styrene and divinyl benzene. Like the styrene materials, these composite materials exhibited thermal decomposition behavior significantly different than the neat polymers. Specifically, the thermal decomposition temperature was shifted approximately 100 °C lower than the neat polymer signifying a major chemical change to the polymer network. Thermal analysis of the cycled samples was performed on the siloxane-based composite materials. It was found that after 30 cycles the siloxane-containing polymer composite material has similar TGA/DSC-MS traces as the virgin composite material indicating that the polymer is physically intact upon cycling. Hydrogen capacity measurements revealed that addition of the polymer to the metal hydride in the form of a composite material reduced the inherent hydrogen storage capacity of the material. This reduction in capacity was observed to be independent of the amount of charge/discharge cycles except for the composites containing siloxane, which showed less of an impact on hydrogen storage capacity as it was cycled further. While the reason for this is not clear, it may be due to a chemically stabilizing effect of the siloxane on the metal hydride. Flow-through calorimetry was used to characterize the mitigating effectiveness of the different composites relative to the neat (no polymer) material. The composites were found to be initially effective at reducing the amount of heat released during oxidation, and the best performing material was the siloxane-containing composite which reduced the heat release to less than 50% of the value of the neat material. However, upon cycling the composites, all mitigating behavior was lost. The combined results of the flow-through calorimetry, hydrogen capacity, and thermogravimetric analysis tests lead to the proposed conclusion that while the polymer composites have mitigating potential and are physically robust under cycling, they undergo a chemical change upon cycling that makes them ineffective at mitigating heat release upon oxidation of the metal hydride.« less

Acoustic emission: A useful tool for damage evaluation in composite materials

NASA Astrophysics Data System (ADS)

Mouzakis, Dionysios E.; Dimogianopoulos, Dimitrios G.

2018-02-01

High performance composites for aviation-related structures are prone to constant aging by environmental agents. Previous data from our work reported on the stiffening behaviour of glass fibre polyester composites used in the manufacturing of wind turbine blades. Airplanes from such composites are already on service nowadays. This justifies the detailed study of the exposure of high performance materials to environmental conditions such as varying temperature, humidity, ultraviolet radiation, in order to assess the impact of these important aging factors on their mechanical behaviour. The dramatic changes in the dynamic mechanical response of polymer matrix carbon fibre composites upon exposure to acceleration aging has been assessed in the present study. In order to assess the synergistic effect action of temperature and humidity on composites subjected to changes of temperature from -35 to +40 °C and humidity variations from <10% to 95% RH (non-condensing) specimens were stored in a climatic chamber for 60 days. Conditions were cycled, as if actual flight cycles of 3-4 hours per flight, were to be simulated. Dynamic mechanical analysis tests were performed in three point bending mode. Scanning of frequency and temperature were performed in order to determine both the viscoelastic response as well as the time-dependent behaviour of the aged materials. All tests were run both for aged and pristine materials for comparison purposes. Three point bending testing was performed in both static as well as in Dynamic mechanical analysis, for a range of temperatures and frequencies. Acoustic Emission damage detection was also performed during the three point bending test both in static and dynamic mode. The aged materials had gained in dynamic stiffness. In addition, that, the gain in the storage moduli, was accompanied by a decrease in the material damping ability, as determined by the tanδ parameter. In the final stages of the study, impact testing was performed on both pristine and aged specimens. The experimentally recorded force/time signals were utilized for concluding on the specimens' condition, by means of signal based damage detection methodologies. Effort was invested in utilizing signal analysis in order to get comparative aging-related information on the tested specimens in order to ultimately validate results of mechanical testing.

Flight service evaluation of composite helicopter components

NASA Technical Reports Server (NTRS)

Mardoian, George H.; Ezzo, Maureen B.

1990-01-01

An assessment is presented of ten composite tail rotor spars and four horizontal stabilizers exposed to the effects of in-flight commercial service for up to nine years to establish realistic environmental factors for use in future designs. This evaluation is supported by test results of helicopter components and panels which have been exposed to outdoor environmental effects since 1979. Full scale static and fatigue tests were conducted on graphite/epoxy and Kevlar/epoxy composite components removed from Sikorsky Model S-76 helicopters in commercial operations off the Gulf Coast of Louisiana. Small scale static and fatigue tests were conducted on coupons obtained from panels exposed to outdoor conditions in Stratford, CT and West Palm Beach, Florida. The panel materials and ply configurations were representative of the S-76 components. The results are discussed of moisture analyses and strength tests on both the S-76 components and composite panels after up to nine years of outdoor exposure. Full scale tests performed on the helicopter components did not disclose any significant reductions from the baseline strengths. The results increased confidence in the long term durability of advanced composite materials in helicopter structural applications.

Experimental Studies on Strength Behaviour of Notched Glass/Epoxy Laminated Composites under Uni-axial and Bi-axial Loading

NASA Astrophysics Data System (ADS)

Guptha, V. L. Jagannatha; Sharma, Ramesh S.

2017-11-01

The use of FRP composite materials in aerospace, aviation, marine, automotive and civil engineering industry has increased rapidly in recent years due to their high specific strength and stiffness properties. The structural members contrived from such composite materials are generally subjected to complex loading conditions and leads to multi-axial stress conditions at critical surface localities. Presence of notches, much required for joining process of composites, makes it further significant. The current practice of using uni-axial test data alone to validate proposed material models is inadequate leading to evaluation and consideration of bi-axial test data. In order to correlate the bi-axial strengths with the uni-axial strengths of GFRP composite laminates in the presence of a circular notch, bi-axial tests using four servo-hydraulic actuators with four load cells were carried out. To determine the in-plane strength parameters, bi-axial cruciform test specimen model was considered. Three different fibre orientations, namely, 0°, 45°, and 90° are considered with a central circular notch of 10 mm diameter in the present investigation. From the results obtained, it is observed that there is a reduction in strength of 5.36, 2.41 and 13.92% in 0°, 45°, and 90° fibre orientation, respectively, under bi-axial loading condition as compared to that of uni-axial loading in laminated composite.

Development of Composite Honeycomb and Solid Laminate Reference Standards to Aid Aircraft Inspections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dorrell, L.; Roach, D.

1999-03-04

The rapidly increasing use of composites on commercial airplanes coupled with the potential for economic savings associated with their use in aircraft structures means that the demand for composite materials technology will continue to increase. Inspecting these composite structures is a critical element in assuring their continued airworthiness. The FAA's Airworthiness Assurance NDI Validation Center, in conjunction with the Commercial Aircraft Composite Repair Committee (CACRC), is developing a set of composite reference standards to be used in NDT equipment calibration for accomplishment of damage assessment and post-repair inspection of all commercial aircraft composites. In this program, a series of NDImore » tests on a matrix of composite aircraft structures and prototype reference standards were completed in order to minimize the number of standards needed to carry out composite inspections on aircraft. Two tasks, related to composite laminates and non-metallic composite honeycomb configurations, were addressed. A suite of 64 honeycomb panels, representing the bounding conditions of honeycomb construction on aircraft, were inspected using a wide array of NDI techniques. An analysis of the resulting data determined the variables that play a key role in setting up NDT equipment. This has resulted in a prototype set of minimum honeycomb reference standards that include these key variables. A sequence of subsequent tests determined that this minimum honeycomb reference standard set is able to fully support inspections over the fill range of honeycomb construction scenarios. Current tasks are aimed at optimizing the methods used to engineer realistic flaws into the specimens. In the solid composite laminate arena, we have identified what appears to be an excellent candidate, G11 Phenolic, as a generic solid laminate reference standard material. Testing to date has determined matches in key velocity and acoustic impedance properties, as well as, low attenuation relative to carbon laminates. Furthermore, comparisons of resonance testing response curves from the G11 Phenolic prototype standard was very similar to the resonance response curves measured on the existing carbon and fiberglass laminates. NDI data shows that this material should work for both pulse-echo (velocity-based) and resonance (acoustic impedance-based) inspections. Additional testing and industry review activities are underway to complete the validation of this material.« less

Determination of Significant Composite Processing Factors by Designed Experiment (MSFC Center Director's Discretionary Fund)

NASA Technical Reports Server (NTRS)

Finckenor, J. L.

2003-01-01

To determie composite material properties' effects from porcessing variables, a 3 factorial designed experiment with two replicates was conducted. The factors were cure method (oven versus autoclave), layup (hand versus tape-laying machine), and thickness (8 versus 52 ply). Four material systems were tested: AS4/3501-6, IM7/8551-7, IM7/F655 bismaleimide (BMI), and shear tests on IM7/F584. Material properties were G(sub 12), v(sub 12), E(sub 1c) and E(sub 2c). Since the samples were necessarily nonstandard, strengths, though recorded, cannot be considered valid. Void content was also compared. Autoclave curing helped material properties for the low modulus fiber material but showed little benefit for higher stiffness fibers. The number of plies was very important for epoxy composites but not for the BMI. E(sub 1) was generally unaffected by any factor. Particularly high void content did correlate to reduced properties. Autoclave curing reduced void content over oven curiing but a moderate amount of voids, less than 1 percent void content, didnot correlate with material properties. Oven cures and hand layups can produce high-quality parts. Part thickness of epoxy composites is important, though cure optimization may improve performance. Significant variations can be caused by processing and it is important that test coupons always reflect the layup and processes of the final part.

49 CFR 178.802 - Preparation of fiberboard IBCs for testing.

Code of Federal Regulations, 2010 CFR

2010-10-01

... MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SPECIFICATIONS... IBCs and composite IBCs with fiberboard outer packagings must be conditioned for at least 24 hours in..., fiberboard IBCs or composite IBCs with fiberboard outer packagings may be at ambient conditions. [Amdt. 178...

Influence of polymerization time and depth of cure of resin composites determined by Vickers hardness.

PubMed

Lombardini, Marco; Chiesa, Marco; Scribante, Andrea; Colombo, Marco; Poggio, Claudio

2012-11-01

Adequate polymerization of resin composites could be considered as a crucial factor in obtaining good clinical performance, particularly in stress-bearing areas. An insufficient curing degree affects the resin composite's chemical properties The current in vitro study evaluated the influence of polymerization time and depth of cure of six commercial resin composites by Vickers microhardness (VK). SIX RESIN COMPOSITES WERE SELECTED: Three microhybrid (Esthet.X HD, Amaris, Filtek Silorane), two nanohybrid (Grandio, Ceram.X mono), and one nanofilled (Filtek Supreme XT). The VK of the surface was determined by a microhardness tester using a Vickers diamond indenter and a 200 g load applied for 15 s. The bottom to top mean VK ratio was calculated using the formula: Hardness ratio = VK of bottom surface/VK of top surface. Vickers hardness values of test materials during exposure time of 20 and 40 s and depths of cure of 2 and 3 mm were determined and compared. Data were analyzed using analysis of variance (ANOVA) test. For all the tested materials and with all the exposure time periods, hardness ratio was higher than the minimum value indicated in literature (0.8). Exposure time and depth of cure did not affect hardness ratio values for Filtek Silorane, Grandio, and Filtek Supreme XT. Among the materials tested, the nanofilled and the nanohybrid resin composites were rather insensible to thickness variations. Miicrohybrid composites, instead, had features different from one another.

Deployment Testing of Flexible Composite Hinges in Bi-Material Beams

NASA Technical Reports Server (NTRS)

Sauder, Jonathan F.; Trease, Brian

2016-01-01

Composites have excellent properties for strength, thermal stability, and weight. However, they are traditionally highly rigid, and when used in deployable structures require hinges bonded to the composite material, which increases complexity and opportunities for failure. Recent research in composites has found by adding an elastomeric soft matrix, often silicone instead of an epoxy, the composite becomes flexible. This work explores the deployment repeatability of silicone matrix composite hinges which join rigid composite beams. The hinges were found to have sub-millimeter deployment repeatability. Also, an interesting creep effect was discovered, that a hinges deployment error would decrease with time.

Creep of Carbon Fibre Reinforced Plastics

DTIC Science & Technology

1976-12-01

Details of the laminat - 5ing technique have already been given elsewhere The nominal thickness of material I composite was 2.5mm. All the other...TEST RESULTS 6 5 DISCUSSION 8 5.1 Composites containing 00 fibres 8 5.2 Multi-plied 90 ± 450 material 80I5,3 Angle-plied ±450 material 9 5.4 The...influence of laminate construction on the creep of CFRP 9 5.5 The relationship between creep strain and time under load in carbon fibre composites 10 6

Feasibility study on measuring axial and transverse stress/strain components in composite materials using Bragg sensors

NASA Astrophysics Data System (ADS)

Luyckx, G.; Degrieck, J.; De Waele, W.; Van Paepegem, W.; Van Roosbroeck, J.; Chah, K.; Vlekken, J.; McKenzie, I.; Obst, A.

2017-11-01

A fibre optic sensor design is proposed for simultaneously measuring the 3D stress (or strain) components and temperature inside thermo hardened composite materials. The sensor is based on two fibre Bragg gratings written in polarisation maintaining fibre. Based on calculations of the condition number, it will be shown that reasonable accuracies are to be expected. First tests on the bare sensors and on the sensors embedded in composite material, which confirm the expected behaviour, will be presented.

Stress Analysis and Permeability Testing of Cryogenic Composite Feed Line

NASA Technical Reports Server (NTRS)

Chu, Tsuchin Philip

1999-01-01

For the next generation Single-Stage-To-Orbit (SSTO) Reusable Launch Vehicle (RLV), the use of advanced composite materials is highly desirable and critical to the success of the mission. NASA Marshall Space Flight Center (MSFC) has been working with the aerospace industry for many years to develop and demonstrate the cryogenic composite propellant tanks and feed lines technologies. A 50.8-mm diameter composite feed line for the Clipper Graham (DCY.A) was developed and tested. The purpose of the program is to demonstrate the LH2 permeability, composite to composite and metal joints, as well as composite flange interface of the composite feed line. Stress analysis and permeability testing have been performed on this article. Recently, a larger composite feed line design is being investigated and developed at MSFC for potential use in future RLV. The diameter of the feed line is 203 mm and the overall length is approximately 2.2 meters. This one piece unlined feed line consists of three straight tubular sections joined by two 90 degree elbows. The material chosen is IM7/977-3 prepreg fabric. The lay-up pattern is [0/90, plus or minus 45]s and is built up to 18 plies to the flanges at both ends. A preliminary stress analysis has been conducted to identify potential critical stresses and to develop the finite element analysis (FEA) capability of composite feed lines. As expected, the critical stresses occurred at the rims of some flange holes and the onset of the tapered tubular sections. Further analysis is required to determine the loads, flange deflection, vibration, and combined maximum loads. Two permeability-testing apparatuses were also designed for both flat panel specimens and curved feed line sections after impact damage. A larger permeant gas exposed area is required to accurately determine the effect of impact damage on the permeability of the feed line materials. The flat panel tester was fabricated and assembled. Three test coupons were made of graphite/epoxy plain weave prepreg and unidirectional prepreg. The flow rate was calculated by measuring the change of manometer fluid height per unit time. The permeability of the coupons is then calculated according to Darcy's Law. The pressure increase due to the head rise in the manometer was not considered for the initial estimation. The result of the unidirectional composite coupon agreed with that obtained from the DC-XA feed line testing of a similar material. Further improvement on the design may be required to improve the accuracy and efficiency of permeability testing.

Third Conference on Fibrous Composites in Flight Vehicle Design, part 1

NASA Technical Reports Server (NTRS)

1976-01-01

The use of fibrous composite materials in the design of aircraft and space vehicle structures and their impact on future vehicle systems are discussed. The topics covered include: flight test work on composite components, design concepts and hardware, specialized applications, operational experience, certification and design criteria. Contributions to the design technology base include data concerning material properties, design procedures, environmental exposure effects, manufacturing procedures, and flight service reliability. By including composites as baseline design materials, significant payoffs are expected in terms of reduced structural weight fractions, longer structural life, reduced fuel consumption, reduced structural complexity, and reduced manufacturing cost.

Three-body-wear resistance of the experimental composites containing filler treated with hydrophobic silane coupling agents.

PubMed

Nihei, Tomotaro; Dabanoglu, Alp; Teranaka, Toshio; Kurata, Shigeaki; Ohashi, Katsura; Kondo, Yukishige; Yoshino, Norio; Hickel, Reinhard; Kunzelmann, Karl-Heinz

2008-06-01

This paper evaluated the wear resistance of resin composite materials with fillers which were modified with a novel hydrophobic silane coupling agent. The novel silane coupling agent containing hydrophobic phenyl group 3-(3-methoxy-4-methacryloyloxyphenyl)propyltrimethoxysilane (p-MBS) was synthesized. The experimental light-cure hybrid composites containing 85wt% of filler modified with this silane were formulated. Twelve specimens were prepared for the three-body-wear test with the ACTA machine and the collected data were analyzed statistically using a one-way ANOVA and Tukey's multiple comparison test as the post hoc test. The wear of the composites containing fillers treated with p-MBS was significantly lower compared with the composite materials containing fillers pretreated with 3-methacryloyloxypropyltrimethoxysilane or the commercially composites (AP-X and ELS extra low shrinkage) after a wear test for 200,000 cycles (p<0.05). It is suggested that the resin composites containing fillers modified with the novel hydrophobic silane has high wear resistant, because of the coupling layers treated with this silane had an excellent affinity with the base resin and formed a highly hydrophobic layer on the filler surface.

Mechanical Property Allowables Generated for the Solid Rocket Booster Composite Note Cap

NASA Technical Reports Server (NTRS)

Hodge, A. J.

2000-01-01

Mechanical property characterization was performed on AS4/3501-6 graphite/epoxy and SC350G syntactic foam for the SRB Composite Nose Cap Shuttle Upgrades Project. Lamina level properties for the graphite/epoxy were determined at room temperature, 240 F, 350 F, 480 F, 600 F, and 350 F after a cycle to 600 F. Graphite/epoxy samples were moisture conditioned prior to testing. The syntactic foam material was tested at room temperature, 350 F, and 480 F. A high-temperature test facility was developed at MSFC. Testing was performed with quartz lamp heaters and high resistance heater strips. The thermal history profile of the nose cap was simulated in order to test materials at various times during launch. A correlation study was performed with Southern Research Institute to confirm the test methodology and validity of test results. A-basis allowables were generated from the results of testing on three lots of material.

Preparation Torque Limit for Composites Joined with Mechanical Fasteners

NASA Technical Reports Server (NTRS)

Thomas, Frank P.; Yi, Zhao

2005-01-01

Current design guidelines for determining torque ranges for composites are based on tests and analysis from isotropic materials. Properties of composites are not taken into account. No design criteria based upon a systematic analytical and test analyses is available. This paper is to study the maximum torque load a composite component could carry prior to any failure. Specifically, the torque-tension tests are conducted. NDT techniques including acoustic emission, thermography and photomicroscopy are also utilized to characterize the damage modes.

In-Situ Strain Analysis of Potential Habitat Composites Exposed to a Simulated Long-Term Lunar Radiation Exposure

NASA Technical Reports Server (NTRS)

Rojdev, Kristina; O'Rourke, Mary Jane; Hill, Charles; Nutt, Steven; Atwell, William

2010-01-01

NASA is studying the effects of long-term space radiation on potential multifunctional composite materials for habitats to better determine their characteristics in the harsh space environment. Two composite materials were selected for the study and were placed in a test stand that simulated the stresses of a pressure vessel wall on the material. The samples in the test stand were exposed to radiation at either a fast dose rate or a slow dose rate, and their strain and temperature was recorded during the exposure. It was found that during a fast dose rate exposure the materials saw a decreased strain with time, or a shrinking of the materials. Given previous radiation studies of polymers, this is believed to be a result of crosslinking occurring in the matrix material. However, with a slow dose rate, the materials saw an increase in strain with time, or a stretching of the materials. This result is consistent with scission or degradation of the matrix occurring, possibly due to oxidative degradation.

Research priorities and history of advanced composite compression testing

NASA Technical Reports Server (NTRS)

Baumann, K. J.

1981-01-01

Priorities for standard compression testing research in advanced laminated fibrous composite materials are presented along with a state of the art survey (completed in 1979) including history and commentary on industrial test methods. Historically apparent research priorities and consequent (lack of) progress are supporting evidence for newly derived priorities.

Finite-Element Modeling of a Damaged Pipeline Repaired Using the Wrap of a Composite Material

NASA Astrophysics Data System (ADS)

Lyapin, A. A.; Chebakov, M. I.; Dumitrescu, A.; Zecheru, G.

2015-07-01

The nonlinear static problem of FEM modeling of a damaged pipeline repaired by a composite material and subjected to internal pressure is considered. The calculation is carried out using plasticity theory for the pipeline material and considering the polymeric filler and the composite wrap. The level of stresses in various zones of the structure is analyzed. The most widespread alloy used for oil pipelines is selected as pipe material. The contribution of each component of the pipeline-filler-wrap system to the level of stresses is investigated. The effect of the number of composite wrap layers is estimated. The results obtained allow one to decrease the costs needed for producing test specimens.

Effects of thermal cycling on composite materials for space structures

NASA Technical Reports Server (NTRS)

Tompkins, Stephen S.

1989-01-01

The effects of thermal cycling on the thermal and mechanical properties of composite materials that are candidates for space structures are briefly described. The results from a thermal analysis of the orbiting Space Station Freedom is used to define a typical thermal environment and the parameters that cause changes in the thermal history. The interactions of this environment with composite materials are shown and described. The effects of this interaction on the integrity as well as the properties of GR/thermoset, Gr/thermoplastic, Gr/metal and Gr/glass composite materials are discussed. Emphasis is placed on the effects of the interaction that are critical to precision spacecraft. Finally, ground test methodology are briefly discussed.

Full in-vitro analyses of new-generation bulk fill dental composites cured by halogen light.

PubMed

Tekin, Tuçe Hazal; Kantürk Figen, Aysel; Yılmaz Atalı, Pınar; Coşkuner Filiz, Bilge; Pişkin, Mehmet Burçin

2017-08-01

The objective of this study was to investigate the full in-vitro analyses of new-generation bulk-fill dental composites cured by halogen light (HLG). Two types' four composites were studied: Surefill SDR (SDR) and Xtra Base (XB) as bulk-fill flowable materials; QuixFill (QF) and XtraFill (XF) as packable bulk-fill materials. Samples were prepared for each analysis and test by applying the same procedure, but with different diameters and thicknesses appropriate to the analysis and test requirements. Thermal properties were determined by thermogravimetric analysis (TG/DTG) and differential scanning calorimetry (DSC) analysis; the Vickers microhardness (VHN) was measured after 1, 7, 15 and 30days of storage in water. The degree of conversion values for the materials (DC, %) were immediately measured using near-infrared spectroscopy (FT-IR). The surface morphology of the composites was investigated by scanning electron microscopes (SEM) and atomic-force microscopy (AFM) analyses. The sorption and solubility measurements were also performed after 1, 7, 15 and 30days of storage in water. In addition to his, the data were statistically analyzed using one-way analysis of variance, and both the Newman Keuls and Tukey multiple comparison tests. The statistical significance level was established at p<0.05. According to the ISO 4049 standards, all the tested materials showed acceptable water sorption and solubility, and a halogen light source was an option to polymerize bulk-fill, resin-based dental composites. Copyright © 2017 Elsevier B.V. All rights reserved.

Carbon fiber based composites stress analysis. Experimental and computer comparative studies

NASA Astrophysics Data System (ADS)

Sobek, M.; Baier, A.; Buchacz, A.; Grabowski, Ł.; Majzner, M.

2015-11-01

Composite materials used nowadays for the production of composites are the result of advanced research. This allows assuming that they are among the most elaborate tech products of our century. That fact is evidenced by the widespread use of them in the most demanding industries like aerospace and space industry. But the heterogeneous materials and their advantages have been known to mankind in ancient times and they have been used by nature for millions of years. Among the fibers used in the industry most commonly used are nylon, polyester, polypropylene, boron, metal, glass, carbon and aramid. Thanks to their physical properties last three fiber types deserve special attention. High strength to weight ratio allow the use of many industrial solutions. Composites based on carbon and glass fibers are widely used in the automotive. Aramid fibers ideal for the fashion industry where the fabric made from the fibers used to produce the protective clothing. In the paper presented issues of stress analysis of composite materials have been presented. The components of composite materials and principles of composition have been discussed. Particular attention was paid to the epoxy resins and the fabrics made from carbon fibers. The article also includes basic information about strain measurements performed on with a resistance strain gauge method. For the purpose of the laboratory tests a series of carbon - epoxy composite samples were made. For this purpose plain carbon textile was used with a weight of 200 g/mm2 and epoxy resin LG730. During laboratory strain tests described in the paper Tenmex's delta type strain gauge rosettes were used. They were arranged in specific locations on the surface of the samples. Data acquisition preceded using HBM measurement equipment, which included measuring amplifier and measuring head. Data acquisition was performed using the Easy Catman. In order to verify the results of laboratory tests numerical studies were carried out in a computing environment, Siemens PLM NX 9.0. For this purpose, samples were modeled composite corresponding to real samples. Tests were made for boundary conditions compatible with the laboratory tests boundary conditions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonamici, Chloë E.; Kinman, William S.; Fournelle, John H.

Reprocessed earth material is a glassy nuclear fallout debris from near-surface nuclear tests. A geochemical approach to analysis of glassy fallout is uniquely suited to determine the means of reprocessing and shed light on the mechanisms of fallout formation. An improved understanding of fallout formation is of interest both for its potential to guide post-detonation nuclear forensic investigations and in the context of possible affinities between glassy debris and other glasses generated by high-energy natural events, such as meteorite impacts and lightning strikes. Our study presents a large major-element compositional dataset for glasses within aerodynamic fallout from the Trinity nuclearmore » test (“trinitite”) and a geochemically based analysis of the glass compositional trends. Silica-rich and alkali-rich trinitite glasses show compositions and textures consistent with formation through melting of individual mineral grains—quartz and alkali feldspar, respectively—from the test-site sediment. Furthermore, the volumetrically dominant glass phase—called the CaMgFe glass—shows extreme major-element compositional variability. Compositional trends in the CaMgFe glass are most consistent with formation through volatility-controlled condensation from compositionally heterogeneous plasma. Radioactivity occurs only in CaMgFe glass, indicating that co-condensation of evaporated bulk ground material and trace device material was the main mechanism of radioisotope incorporation into trinitite. CaMgFe trinitite glasses overlap compositionally with basalts, rhyolites, fulgurites, tektites, and microtektites but display greater compositional diversity than all of these naturally formed glasses. Indeed, the most refractory CaMgFe glasses compositionally resemble early solar system condensates—specifically, CAIs.« less

Production integrated nondestructive testing of composite materials and material compounds - an overview

NASA Astrophysics Data System (ADS)

Straß, B.; Conrad, C.; Wolter, B.

2017-03-01

Composite materials and material compounds are of increasing importance, because of the steadily rising relevance of resource saving lightweight constructions. Quality assurance with appropriate Nondestructive Testing (NDT) methods is a key aspect for reliable and efficient production. Quality changes have to be detected already in the manufacturing flow in order to take adequate corrective actions. For materials and compounds the classical NDT methods for defectoscopy, like X-ray and Ultrasound (US) are still predominant. Nevertheless, meanwhile fast, contactless NDT methods, like air-borne ultrasound, dynamic thermography and special Eddy-Current techniques are available in order to detect cracks, voids, pores and delaminations but also for characterizing fiber content, distribution and alignment. In Metal-Matrix Composites US back-scattering can be used for this purpose. US run-time measurements allow the detection of thermal stresses at the metal-matrix interface. Another important area is the necessity for NDT in joining. To achieve an optimum material utilization and product safety as well as the best possible production efficiency, there is a need for NDT methods for in-line inspection of the joint quality while joining or immediately afterwards. For this purpose EMAT (Electromagnetic Acoustic Transducer) technique or Acoustic Emission testing can be used.

Meso-modeling of Carbon Fiber Composite for Crash Safety Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Shih-Po; Chen, Yijung; Zeng, Danielle

2017-04-06

In the conventional approach, the material properties for crash safety simulations are typically obtained from standard coupon tests, where the test results only provide single layer material properties used in crash simulations. However, the lay-up effects for the failure behaviors of the real structure were not considered in numerical simulations. Hence, there was discrepancy between the crash simulations and experimental tests. Consequently, an intermediate stage is required for accurate predictions. Some component tests are required to correlate the material models in the intermediate stage. In this paper, a Mazda Tube under high-impact velocity is chosen as an example for themore » crash safety analysis. The tube consists of 24 layers of uni-directional (UD) carbon fiber composite materials, in which 4 layers are perpendicular to, while the other layers are parallel to the impact direction. An LS-DYNA meso-model was constructed with orthotropic material models counting for the single-layer material behaviors. Between layers, a node-based tie-break contact was used for modeling the delamination of the composite material. Since fiber directions are not single-oriented, the lay-up effects could be an important effect. From the first numerical trial, premature material failure occurred due to the use of material parameters obtained directly from the coupon tests. Some parametric studies were conducted to identify the cause of the numerical instability. The finding is that the material failure strength used in the numerical model needs to be enlarged to stabilize the numerical model. Some hypothesis was made to provide the foundation for enlarging the failure strength and the corresponding experiments will be conducted to validate the hypothesis.« less

Compression Behavior of Fluted-Core Composite Panels

NASA Technical Reports Server (NTRS)

Schultz, Marc R.; Oremont, Leonard; Guzman, J. Carlos; McCarville, Douglas; Rose, Cheryl A.; Hilburger, Mark W.

2011-01-01

In recent years, fiber-reinforced composites have become more accepted for aerospace applications. Specifically, during NASA s recent efforts to develop new launch vehicles, composite materials were considered and baselined for a number of structures. Because of mass and stiffness requirements, sandwich composites are often selected for many applications. However, there are a number of manufacturing and in-service concerns associated with traditional honeycomb-core sandwich composites that in certain instances may be alleviated through the use of other core materials or construction methods. Fluted-core, which consists of integral angled web members with structural radius fillers spaced between laminate face sheets, is one such construction alternative and is considered herein. Two different fluted-core designs were considered: a subscale design and a full-scale design sized for a heavy-lift-launch-vehicle interstage. In particular, axial compression of fluted-core composites was evaluated with experiments and finite-element analyses (FEA); axial compression is the primary loading condition in dry launch-vehicle barrel sections. Detailed finite-element models were developed to represent all components of the fluted-core construction, and geometrically nonlinear analyses were conducted to predict both buckling and material failures. Good agreement was obtained between test data and analyses, for both local buckling and ultimate material failure. Though the local buckling events are not catastrophic, the resulting deformations contribute to material failures. Consequently, an important observation is that the material failure loads and modes would not be captured by either linear analyses or nonlinear smeared-shell analyses. Compression-after-impact (CAI) performance of fluted core composites was also investigated by experimentally testing samples impacted with 6 ft.-lb. impact energies. It was found that such impacts reduced the ultimate load carrying capability by approximately 40% on the subscale test articles and by less than 20% on the full-scale test articles. Nondestructive inspection of the damage zones indicated that the detectable damage was limited to no more than one flute on either side of any given impact. More study is needed, but this may indicate that an inherent damage-arrest capability of fluted core could provide benefits over traditional sandwich designs in certain weight-critical applications.

Research on mechanical properties of carbon fiber /polyamide reinforced PP composites

NASA Astrophysics Data System (ADS)

Chen, Xinghui; Yu, Qiang; Liu, Lixia; Ji, Wenhua; Yang, Li; Fan, Dongli

2017-10-01

The polyamide composites reinforced by carbon fiber/polypropylene are produced by injection molding processing. The flow abilities and mechanical properties of the CF/PA/PP composite materials are studied by the fusion index instrument and the universal testing machine. The results show that with the content of carbon fiber/polyamide increase, the impact breaking strength and the tensile property of the composite materials increase, which is instructive to the actual injection production of polypropylene products.

Static and dynamic strain energy release rates in toughened thermosetting composite laminates

NASA Technical Reports Server (NTRS)

Cairns, Douglas S.

1992-01-01

In this work, the static and dynamic fracture properties of several thermosetting resin based composite laminates are presented. Two classes of materials are explored. These are homogeneous, thermosetting resins and toughened, multi-phase, thermosetting resin systems. Multi-phase resin materials have shown enhancement over homogenous materials with respect to damage resistance. The development of new dynamic tests are presented for composite laminates based on Width Tapered Double Cantilevered Beam (WTDCB) for Mode 1 fracture and the End Notched Flexure (ENF) specimen. The WTDCB sample was loaded via a low inertia, pneumatic cylinder to produce rapid cross-head displacements. A high rate, piezo-electric load cell and an accelerometer were mounted on the specimen. A digital oscilloscope was used for data acquisition. Typical static and dynamic load versus displacement plots are presented. The ENF specimen was impacted in three point bending with an instrumented impact tower. Fracture initiation and propagation energies under static and dynamic conditions were determined analytically and experimentally. The test results for Mode 1 fracture are relatively insensitive to strain rate effects for the laminates tested in this study. The test results from Mode 2 fracture indicate that the toughened systems provide superior fracture initiation and higher resistance to propagation under dynamic conditions. While the static fracture properties of the homogeneous systems may be relatively high, the apparent Mode 2 dynamic critical strain energy release rate drops significantly. The results indicate that static Mode 2 fracture testing is inadequate for determining the fracture performance of composite structures subjected to conditions such as low velocity impact. A good correlation between the basic Mode 2 dynamic fracture properties and the performance is a combined material/structural Compression After Impact (CAI) test is found. These results underscore the importance of examining rate-dependent behavior for determining the longevity of structures manufactured from composite materials.

Mechanical Properties of T650-35/AFR-PE-4 at Elevated Temperatures for Lightweight Aeroshell Designs

NASA Technical Reports Server (NTRS)

Whitley, Karen S.; Collins, TImothy J.

2006-01-01

Considerable efforts have been underway to develop multidisciplinary technologies for aeroshell structures that will significantly increase the allowable working temperature for the aeroshell components, and enable the system to operate at higher temperatures while sustaining performance and durability. As part of these efforts, high temperature polymer matrix composites and fabrication technologies are being developed for the primary load bearing structure (heat shield) of the spacecraft. New high-temperature resins and composite material manufacturing techniques are available that have the potential to significantly improve current aeroshell design. In order to qualify a polymer matrix composite (PMC) material as a candidate aeroshell structural material, its performance must be evaluated under realistic environments. Thus, verification testing of lightweight PMC's at aeroshell entry temperatures is needed to ensure that they will perform successfully in high-temperature environments. Towards this end, a test program was developed to characterize the mechanical properties of two candidate material systems, T650-35/AFR-PE-4 and T650-35/RP46. The two candidate high-temperature polyimide resins, AFR-PE-4 and RP46, were developed at the Air Force Research Laboratory and NASA Langley Research Center, respectively. This paper presents experimental methods, strength, and stiffness data of the T650-35/AFR-PE-4 material as a function of elevated temperatures. The properties determined during the research test program herein, included tensile strength, tensile stiffness, Poisson s ratio, compressive strength, compressive stiffness, shear modulus, and shear strength. Unidirectional laminates, a cross-ply laminate and two eight-harness satin (8HS)-weave laminates (4-ply and 10-ply) were tested according to ASTM standard methods at room and elevated temperatures (23, 316, and 343 C). All of the relevant test methods and data reduction schemes are outlined along with mechanical data. These data contribute to a database of material properties for high-temperature polyimide composites that will be used to identify the material characteristics of potential candidate materials for aeroshell structure applications.

Investigating compression failure mechanisms in composite laminates with a transparent fiberglass-epoxy birefringent materials

NASA Technical Reports Server (NTRS)

Shuart, M. J.; Williams, J. G.

1984-01-01

The response and failure of a + or - 45s class laminate was studied by transparent fiberglass epoxy composite birefringent material. The birefringency property allows the laminate stress distribution to be observed during the test and also after the test if permanent residual stresses occur. The location of initial laminate failure and of the subsequent failure propagation are observed through its transparency characteristics. Experimental results are presented.

Hydrogen Permeability of a Polymer Based Composite Tank Material Under Tetra-Axial Strain

NASA Technical Reports Server (NTRS)

Stokes, Eric H.

2003-01-01

In order to increase the performance of future expendable and reusable launch vehicles and reduce per-pound payload launch costs, weight reductions have been sought in vehicle components. Historically, the cryogenic propellant tanks for launch vehicles have been constructed from metal. These are some of the largest structural components in the vehicle and contribute significantly to the vehicles total dry weight. A successful replacement material will be conformable, have a high strength to weight ratio, and have a low gas-permeability to the cryogens being stored, i.e., oxygen and hydrogen. Polymer-based composites are likely candidates to fill this role. Polymer and polymer-based composites in general are known to have acceptable gas permeation properties in their as-cured state.1 The use of polymer-based composites for this application has been proposed for some time.2 Some successes have been reported with oxygen3, but other than the DC-XA experience, those with hydrogen have been limited. The primary reason for this has been the small molecular diameter of hydrogen, the lower temperatures of the liquid, and that the composite materials examined to date have all been susceptible to microcrack formation in response to the thermal-mechanical cycles experienced in the use-environment. There have been numerous accounts of composite materials with reported acceptable resistance to the formation of microcracks when exposed to various mechanical and/or thermal cycles. However, virtually all of these studies have employed uniaxial loads and there has been no discussion or empirical evidence pertaining to how these loads relate to the biaxial state of stress in the material in its use environment. Furthermore, many of these studies have suffered from a lack of instrument sensitivity in detecting hydrogen permeability, no standards, insufficient documentation of test conditions, testing of cycled materials in their unload state, and/or false assumptions about the nature of the microcracks in the material. This paper documents the results of hydrogen permeability testing on a Bismaleimide (BMI) based graphite fiber composite material under a variety of tetra-axial strain states.

Fire test method for graphite fiber reinforced plastics

NASA Technical Reports Server (NTRS)

Bowles, K. J.

1980-01-01

A potential problem in the use of graphite fiber reinforced resin matrix composites is the dispersal of graphite fibers during accidental fires. Airborne, electrically conductive fibers originating from the burning composites could enter and cause shorting in electrical equipment located in surrounding areas. A test method for assessing the burning characteristics of graphite fiber reinforced composites and the effectiveness of the composites in retaining the graphite fibers has been developed. The method utilizes a modified Ohio State University Rate of Heat Release apparatus. The equipment and the testing procedure are described. The application of the test method to the assessment of composite materials is illustrated for two resin matrix/graphite composite systems.

A high temperature testing system for ceramic composites

NASA Technical Reports Server (NTRS)

Hemann, John

1994-01-01

Ceramic composites are presently being developed for high temperature use in heat engine and space power system applications. The operating temperature range is expected to be 1090 to 1650 C (2000 F to 3000 F). Very little material data is available at these temperatures and, therefore, it is desirable to thoroughly characterize the basic unidirectional fiber reinforced ceramic composite. This includes testing mainly for mechanical material properties at high temperatures. The proper conduct of such characterization tests requires the development of a tensile testing system includes unique gripping, heating, and strain measuring devices which require special considerations. The system also requires an optimized specimen shape. The purpose of this paper is to review various techniques for measuring displacements or strains, preferably at elevated temperatures. Due to current equipment limitations it is assumed that the specimen is to be tested at a temperature of 1430 C (2600F) in an oxidizing atmosphere. For the most part, previous high temperature material characterization tests, such as flexure and tensile tests, have been performed in inert atmospheres. Due to the harsh environment in which the ceramic specimen is to be tested, many conventional strain measuring techniques can not be applied. Initially a brief description of the more commonly used mechanical strain measuring techniques is given. Major advantages and disadvantages with their application to high temperature tensile testing of ceramic composites are discussed. Next, a general overview is given for various optical techniques. Advantages and disadvantages which are common to these techniques are noted. The optical methods for measuring strain or displacement are categorized into two sections. These include real-time techniques. Finally, an optical technique which offers optimum performance with the high temperature tensile testing of ceramic composites is recommended.

Gas sensors based on carbon nanoflake/tin oxide composites for ammonia detection.

PubMed

Lee, Soo-Keun; Chang, Daeic; Kim, Sang Wook

2014-03-15

Carbon nanoflake (CNFL) was obtained from graphite pencil by using the electrochemical method and the CNFL/SnO2 composite material assessed its potential as an ammonia gas sensor. A thin film resistive gas sensor using the composite material was manufactured by the drop casting method, and the sensor was evaluated to test in various ammonia concentrations and operating temperatures. Physical and chemical characteristics of the composite material were assessed using SEM, TEM, SAED, EDS and Raman spectroscopy. The composite material having 10% of SnO2 showed 3 times higher sensor response and better repeatability than the gas sensor using pristine SnO2 nano-particle at the optimal temperature of 350°C. Copyright © 2013 Elsevier B.V. All rights reserved.

Effect of Data Reduction and Fiber-Bridging on Mode I Delamination Characterization of Unidirectional Composites

NASA Technical Reports Server (NTRS)

Murri, Gretchen B.

2011-01-01

Reliable delamination characterization data for laminated composites are needed for input in analytical models of structures to predict delamination onset and growth. The double-cantilevered beam (DCB) specimen is used to measure fracture toughness, GIc, and strain energy release rate, GImax, for delamination onset and growth in laminated composites under mode I loading. The current study was conducted as part of an ASTM Round Robin activity to evaluate a proposed testing standard for Mode I fatigue delamination propagation. Static and fatigue tests were conducted on specimens of IM7/977-3 and G40-800/5276-1 graphite/epoxies, and S2/5216 glass/epoxy DCB specimens to evaluate the draft standard "Standard Test Method for Mode I Fatigue Delamination Propagation of Unidirectional Fiber-Reinforced Polymer Matrix Composites." Static results were used to generate a delamination resistance curve, GIR, for each material, which was used to determine the effects of fiber-bridging on the delamination growth data. All three materials were tested in fatigue at a cyclic GImax level equal to 90% of the fracture toughness, GIc, to determine the delamination growth rate. Two different data reduction methods, a 2-point and a 7-point fit, were used and the resulting Paris Law equations were compared. Growth rate results were normalized by the delamination resistance curve for each material and compared to the nonnormalized results. Paris Law exponents were found to decrease by 5.4% to 46.2% due to normalizing the growth data. Additional specimens of the IM7/977-3 material were tested at 3 lower cyclic GImax levels to compare the effect of loading level on delamination growth rates. The IM7/977-3 tests were also used to determine the delamination threshold curve for that material. The results show that tests at a range of loading levels are necessary to describe the complete delamination behavior of this material.

Testing of felt-ceramic materials for combustor applications

NASA Technical Reports Server (NTRS)

Venkat, R. S.; Roffe, G.

1983-01-01

The feasibility of using composite felt ceramic materials as combustor liners was experimentally studied. The material consists of a porous felt pad sandwiched between a layer of ceramic and one of solid metal. Flat, rectangular test panels, which encompassed several design variations of the basic composite material, were tested, two at a time, in a premixed gas turbine combustor as sections of the combustor wall. Tests were conducted at combustor inlet conditions of 0.5 MPa and 533 K with a reference velocity of 25 m/s. The panels were subjected to a hot gas temperature of 2170 K with 1% of the total airflow used to film cool the ceramic surface of the test panel. In general, thin ceramic layers yield low ceramic stress levels with high felt ceramic interface temperatures. On the other hand, thick ceramic layers result in low felt ceramic interface temperatures but high ceramic stress levels. Extensive thermal cycling appears to cause material degradation, but for a limited number of cycles, the survivability of felt ceramic materials, even under extremely severe combustor operating conditions, was conclusively demonstrated.

Manufacturing Methods and Technology Project Summary Reports

DTIC Science & Technology

1984-06-01

was selected as the composite material. This selection was based upon the following advantages in comparison to aluminum: 0 Stiffness to weight...closer to titanium than aluminum. Other composite candidate materials considered ( glass , Kevlar and metal matrix) did not offer all of these...of the bearing support ring, and the attachment of the bearing support ring to the composite gimbal base plate. A thermal test structure, which

Optimum design of structures of composite materials in response to aerodynamic noise and noise transmission

NASA Technical Reports Server (NTRS)

Yang, J. C. S.; Tsui, C. Y.

1977-01-01

Elastic wave propagation and attenuation in a model fiber matrix was investigated. Damping characteristics in graphite epoxy composite materials were measured. A sound transmission test facility suitable to incorporate into NASA Ames wind tunnel for measurement of transmission loss due to sound generation in boundary layers was constructed. Measurement of transmission loss of graphite epoxy composite panels was also included.

A Study on Tribological Behavior of Glass-Epoxy Composite Filled with Granite Dust

NASA Astrophysics Data System (ADS)

Ray, Subhrajit; Rout, Arun Ku; KuSahoo, Ashok

2017-08-01

Granite powder is one of the solid wastes generated from stone processing industry used as organic filler replacing the conventional ceramic fillers in polymer matrix composite to increase the mechanical properties. The present work investigates the addition of granite powder on erosion wear properties of epoxy-glass fiber composite. The solid particle erosion wear rates of these hybrid composites are recorded considering various control parameters as impingement angles, erodent sizes and impact velocities following erosion resistance test in an air erosion test device at room temperatures. The test was conducted as per the Taguchi experimental design to minimize the erosion loss of material. The SEM views show the surface resistivity for the granite added specimens. The microscopic study also indicates various methods of material removal, crater wear and other subjective allocation during erosion experiment of the samples.

Damage development in titanium metal matrix composites subjected to cyclic loading

NASA Technical Reports Server (NTRS)

Johnson, W. S.

1992-01-01

Several layups of SCS-6/Ti-15-3 composites were investigated. Fatigue tests were conducted and analyzed for both notched and unnotched specimens at room temperature and elevated temperatures. Thermo-mechanical fatigue results were analyzed. Test results indicated that the stress in the 0 degree fibers is the controlling factor in fatigue life. The static and fatigue strength of these materials is shown to be strongly dependent on the level of residual stresses and the fiber/matrix interfacial strength. Fatigue tests of notched specimens showed that cracks can initiate and grow many fiber spacings in the matrix materials without breaking fibers. Fiber bridging models were applied to characterize the crack growth behavior. The matrix cracks are shown to significantly reduce the residual strength of notched composites. The notch strength of these composites was accurately predicted using a micromechanics based methodology.

Damage development in titanium metal-matrix composites subjected to cyclic loading

NASA Technical Reports Server (NTRS)

Johnson, W. S.

1993-01-01

Several layups of SCS-6/Ti-15-3 composites were investigated. Fatigue tests were conducted and analyzed for both notched and unnotched specimens at room temperature and elevated temperatures. Thermo-mechanical fatigue results were analyzed. Test results indicated that the stress in the 0 degree fibers is the controlling factor in fatigue life. The static and fatigue strength of these materials is shown to be strongly dependent on the level of residual stresses and the fiber/matrix interfacial strength. Fatigue tests of notched specimens showed that cracks can initiate and grow many fiber spacings in the matrix materials without breaking fibers. Fiber bridging models were applied to characterize the crack growth behavior. The matrix cracks are shown to significantly reduce the residual strength of notched composites. The notch strength of these composites was accurately predicted using a micromechanics based methodology.

Evaluation of several additional dry lubricants for spacecraft applications

NASA Technical Reports Server (NTRS)

Vest, C. E.

1973-01-01

Four transfer-film ball-bearing retainer materials were evaluated for their lubricating ability and wear capability under conditions of 120-gram radial load, 450-gram axial load, 3600-rpm unidirectional rotation, 23 C ambient temperature, and less than .1 microtorr pressure, using R-2 sized unshielded ball bearings. The 'stop-test' criterion was a total of one billion revolutions or a torque buildup greater than 18 gm-cm per bearing pair. A PTFE-fiberglass-MoS2 composite, a PTFE-bronze composite, and a tantalum-molybdenum-MoS2 composite operated for one billion revolutions without reaching the 18-gram torque limit. A p-oxybenzoyl polymer-MoS2 composite operated sixteen million revolutions before reaching the 18-gm cm stop-test torque. The first three materials are considered as suitable lubricants under the test conditions employed.

Unlined Reuseable Filament Wound Composite Cryogenic Tank Testing

NASA Technical Reports Server (NTRS)

Murphy, A. W.; Lake, R. E.; Wilkerson, C.

1999-01-01

An unlined reusable filament wound composite cryogenic tank was tested at the Marshall Space Flight Center using LH2 cryogen and pressurization to 320 psig. The tank was fabricated by Phillips Laboratory and Wilson Composite Group, Inc., using an EnTec five-axis filament winder and sand mandrels. The material used was IM7/977-2 (graphite/epoxy).

High Speed Thermal Imaging on Ballistic Impact of Triaxially Braided Composites

NASA Technical Reports Server (NTRS)

Johnston, Joel P.; Pereira, J. Michael; Ruggeri, Charles R.; Roberts, Gary D.

2017-01-01

Ballistic impact experiments were performed on triaxially braided polymer matrix composites to study the heat generated in the material due to projectile velocity and penetration damage. Quantifying the heat generation phenomenon is crucial for attaining a better understanding of composite behavior and failure under impact loading. The knowledge gained can also be used to improve physics-based models which can numerically simulate impact of composites. Triaxially braided (0/+60/-60) composite panels were manufactured with T700S standard modulus carbon fiber and two epoxy resins. The PR520 (toughened) and 3502 (untoughened) resin systems were used to make different panels to study the effects of resin properties on temperature rise. Ballistic impact tests were conducted on these composite panels using a gas gun, and different projectile velocities were applied to study the effect on the temperature results. Temperature contours were obtained from the rear surface of the panel during the test through a high speed, infrared (IR) thermal imaging system. The contours show that high temperatures were locally generated and more pronounced along the axial tows for the T700S/PR520 composite specimens; whereas, tests performed on T700S/3502 composite panels using similar impact velocities demonstrated a widespread area of lower temperature rises. Nondestructive, ultrasonic C-scan analyses were performed to observe and verify the failure patterns in the impacted panels. Overall, the impact experimentation showed temperatures exceeding 525 K (485degF) in both composites which is well above the respective glass transition temperatures for the polymer constituents. This expresses the need for further high strain rate testing and measurement of the temperature and deformation fields to fully understand the complex behavior and failure of the material in order to improve the confidence in designing aerospace components with these materials.

Experimental investigation of the crashworthiness of scaled composite sailplane fuselages

NASA Technical Reports Server (NTRS)

Kampf, Karl-Peter; Crawley, Edward F.; Hansman, R. John, Jr.

1989-01-01

The crash dynamics and energy absorption of composite sailplane fuselage segments undergoing nose-down impact were investigated. More than 10 quarter-scale structurally similar test articles, typical of high-performance sailplane designs, were tested. Fuselages segments were fabricated of combinations of fiberglass, graphite, Kevlar, and Spectra fabric materials. Quasistatic and dynamic tests were conducted. The quasistatic tests were found to replicate the strain history and failure modes observed in the dynamic tests. Failure modes of the quarter-scale model were qualitatively compared with full-scale crash evidence and quantitatively compared with current design criteria. By combining material and structural improvements, substantial increases in crashworthiness were demonstrated.

Moisture effect on mechanical properties of polymeric composite materials

NASA Astrophysics Data System (ADS)

Airale, A. G.; Carello, M.; Ferraris, A.; Sisca, L.

2016-05-01

The influence of moisture on the mechanical properties of fibre-reinforced polymer matrix composites (PMCs) was investigated. Four materials had been take into account considering: both 2×2-Twill woven carbon fibre or glass fibre, thermosetting matrix (Epoxy Resin) or thermoplastic matrix (Polyphenylene Sulfide). The specimens were submitted for 1800 hours to a hygrothermic test to evaluate moisture absorption on the basis of the Fick's law and finally tested to verify the mechanical properties (ultimate tensile strength). The results showed that the absorbed moisture decreases those properties of composites which were dominated by the matrix or the interface, while was not detectable the influence of water on the considered fibre. An important result is that the diffusion coefficient is highest for glass/PPS and lowest for carbon/epoxy composite material. The results give useful suggestions for the design of vehicle components that are exposed to environmental conditions (rain, snow and humidity).

Effects of age condition on the distribution and integrity of inorganic fillers in dental resin composites.

PubMed

D'Alpino, Paulo Henrique Perlatti; Svizero, Nádia da Rocha; Bim Júnior, Odair; Valduga, Claudete Justina; Graeff, Carlos Frederico de Oliveira; Sauro, Salvatore

2016-06-01

The aim of this study is to evaluate the distribution of the filler size along with the zeta potential, and the integrity of silane-bonded filler surface in different types of restorative dental composites as a function of the material age condition. Filtek P60 (hybrid composite), Filtek Z250 (small-particle filled composite), Filtek Z350XT (nanofilled composite), and Filtek Silorane (silorane composite) (3M ESPE) were tested at different stage condition (i.e., fresh/new, aged, and expired). Composites were submitted to an accelerated aging protocol (Arrhenius model). Specimens were obtained by first diluting each composite specimen in ethanol and then dispersed in potassium chloride solution (0.001 mol%). Composite fillers were characterized for their zeta potential, mean particle size, size distribution, via poly-dispersion dynamic light scattering. The integrity of the silane-bonded surface of the fillers was characterized by FTIR. The material age influenced significantly the outcomes; Zeta potential, filler characteristics, and silane integrity varied both after aging and expiration. Silorane presented the broadest filler distribution and lowest zeta potential. Nanofilled and silorane composites exhibited decreased peak intensities in the FTIR analysis, indicating a deficiency of the silane integrity after aging or expiry time. Regardless to the material condition, the hybrid and the small-particle-filled composites were more stable overtime as no significant alteration in filler size distribution, diameter, and zeta potential occurred. A deficiency in the silane integrity in the nanofilled and silorane composites seems to be affected by the material stage condition. The materials conditions tested in this study influenced the filler size distribution, the zeta potential, and integrity of the silane adsorbed on fillers in the nanofilled and silorane composites. Thus, this may result in a decrease of the clinical performance of aforementioned composites, in particular, if these are used after inappropriate storage conditions.

Fire Tests of Automotive Grade Carbon Fiber Composites

DOT National Transportation Integrated Search

1980-06-01

This report presents the results of a fire test study on selected composite materials containing carbon fibers that are planned for use, or that have a high potential for use, in automobiles and other vehicles. The study objectives were to determine ...

Advanced Composite Wind Turbine Blade Design Based on Durability and Damage Tolerance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abumeri, Galib; Abdi, Frank

2012-02-16

The objective of the program was to demonstrate and verify Certification-by-Analysis (CBA) capability for wind turbine blades made from advanced lightweight composite materials. The approach integrated durability and damage tolerance analysis with robust design and virtual testing capabilities to deliver superior, durable, low weight, low cost, long life, and reliable wind blade design. The GENOA durability and life prediction software suite was be used as the primary simulation tool. First, a micromechanics-based computational approach was used to assess the durability of composite laminates with ply drop features commonly used in wind turbine applications. Ply drops occur in composite joints andmore » closures of wind turbine blades to reduce skin thicknesses along the blade span. They increase localized stress concentration, which may cause premature delamination failure in composite and reduced fatigue service life. Durability and damage tolerance (D&DT) were evaluated utilizing a multi-scale micro-macro progressive failure analysis (PFA) technique. PFA is finite element based and is capable of detecting all stages of material damage including initiation and propagation of delamination. It assesses multiple failure criteria and includes the effects of manufacturing anomalies (i.e., void, fiber waviness). Two different approaches have been used within PFA. The first approach is Virtual Crack Closure Technique (VCCT) PFA while the second one is strength-based. Constituent stiffness and strength properties for glass and carbon based material systems were reverse engineered for use in D&DT evaluation of coupons with ply drops under static loading. Lamina and laminate properties calculated using manufacturing and composite architecture details matched closely published test data. Similarly, resin properties were determined for fatigue life calculation. The simulation not only reproduced static strength and fatigue life as observed in the test, it also showed composite damage and fracture modes that resemble those reported in the tests. The results show that computational simulation can be relied on to enhance the design of tapered composite structures such as the ones used in turbine wind blades. A computational simulation for durability, damage tolerance (D&DT) and reliability of composite wind turbine blade structures in presence of uncertainties in material properties was performed. A composite turbine blade was first assessed with finite element based multi-scale progressive failure analysis to determine failure modes and locations as well as the fracture load. D&DT analyses were then validated with static test performed at Sandia National Laboratories. The work was followed by detailed weight analysis to identify contribution of various materials to the overall weight of the blade. The methodology ensured that certain types of failure modes, such as delamination progression, are contained to reduce risk to the structure. Probabilistic analysis indicated that composite shear strength has a great influence on the blade ultimate load under static loading. Weight was reduced by 12% with robust design without loss in reliability or D&DT. Structural benefits obtained with the use of enhanced matrix properties through nanoparticles infusion were also assessed. Thin unidirectional fiberglass layers enriched with silica nanoparticles were applied to the outer surfaces of a wind blade to improve its overall structural performance and durability. The wind blade was a 9-meter prototype structure manufactured and tested subject to three saddle static loading at Sandia National Laboratory (SNL). The blade manufacturing did not include the use of any nano-material. With silica nanoparticles in glass composite applied to the exterior surfaces of the blade, the durability and damage tolerance (D&DT) results from multi-scale PFA showed an increase in ultimate load of the blade by 9.2% as compared to baseline structural performance (without nano). The use of nanoparticles lead to a delay in the onset of delamination. Load-displacement relationships obtained from testing of the blade with baseline neat material were compared to the ones from analytical simulation using neat resin and using silica nanoparticles in the resin. Multi-scale PFA results for the neat material construction matched closely those from test for both load displacement and location and type of damage and failure. AlphaSTAR demonstrated that wind blade structures made from advanced composite materials can be certified with multi-scale progressive failure analysis by following building block verification approach.« less

Thermal-mechanical behavior of high precision composite mirrors

NASA Technical Reports Server (NTRS)

Kuo, C. P.; Lou, M. C.; Rapp, D.

1993-01-01

Composite mirror panels were designed, constructed, analyzed, and tested in the framework of a NASA precision segmented reflector task. The deformations of the reflector surface during the exposure to space enviroments were predicted using a finite element model. The composite mirror panels have graphite-epoxy or graphite-cyanate facesheets, separated by an aluminum or a composite honeycomb core. It is pointed out that in order to carry out detailed modeling of composite mirrors with high accuracy, it is necessary to have temperature dependent properties of the materials involved and the type and magnitude of manufacturing errors and material nonuniformities. The structural modeling and analysis efforts addressed the impact of key design and materials parameters on the performance of mirrors.

Composite materials for space applications

NASA Technical Reports Server (NTRS)

Rawal, Suraj P.; Misra, Mohan S.; Wendt, Robert G.

1990-01-01

The objectives of the program were to: generate mechanical, thermal, and physical property test data for as-fabricated advanced materials; design and fabricate an accelerated thermal cycling chamber; and determine the effect of thermal cycling on thermomechanical properties and dimensional stability of composites. In the current program, extensive mechanical and thermophysical property tests of various organic matrix, metal matrix, glass matrix, and carbon-carbon composites were conducted, and a reliable database was constructed for spacecraft material selection. Material property results for the majority of the as-fabricated composites were consistent with the predicted values, providing a measure of consolidation integrity attained during fabrication. To determine the effect of thermal cycling on mechanical properties, microcracking, and thermal expansion behavior, approximately 500 composite specimens were exposed to 10,000 cycles between -150 and +150 F. These specimens were placed in a large (18 cu ft work space) thermal cycling chamber that was specially designed and fabricated to simulate one year low earth orbital (LEO) thermal cycling in 20 days. With this rate of thermal cycling, this is the largest thermal cycling unit in the country. Material property measurements of the thermal cycled organic matrix composite laminate specimens exhibited less than 24 percent decrease in strength, whereas, the remaining materials exhibited less than 8 percent decrease in strength. The thermal expansion response of each of the thermal cycled specimens revealed significant reduction in hysteresis and residual strain, and the average CTE values were close to the predicted values.

Self-healing in single and multiple fiber(s) reinforced polymer composites

NASA Astrophysics Data System (ADS)

Woldesenbet, E.

2010-06-01

You Polymer composites have been attractive medium to introduce the autonomic healing concept into modern day engineering materials. To date, there has been significant research in self-healing polymeric materials including several studies specifically in fiber reinforced polymers. Even though several methods have been suggested in autonomic healing materials, the concept of repair by bleeding of enclosed functional agents has garnered wide attention by the scientific community. A self-healing fiber reinforced polymer composite has been developed. Tensile tests are carried out on specimens that are fabricated by using the following components: hollow and solid glass fibers, healing agent, catalysts, multi-walled carbon nanotubes, and a polymer resin matrix. The test results have demonstrated that single fiber polymer composites and multiple fiber reinforced polymer matrix composites with healing agents and catalysts have provided 90.7% and 76.55% restoration of the original tensile strength, respectively. Incorporation of functionalized multi-walled carbon nanotubes in the healing medium of the single fiber polymer composite has provided additional efficiency. Healing is found to be localized, allowing multiple healing in the presence of several cracks.

Preparation of Polyurethane/Graphite Composite Films with Stable Mechanical Property and Wear Resistance Underwater.

PubMed

Wang, Miaomiao; Wang, Zubin; Chen, Qirong; Meng, Xiangfu; Heng, Liping

2018-06-01

The wear resistance and stable mechanical properties affect the service life of the underwater functional materials to a certain extent. Unfortunately, the current study of underwater functional materials is rarely related to these aspects. Herein, we successfully designed and prepared polyurethane/graphite nanosheet (PU/GN) composite materials, which exhibited excellent wear resistance and stable mechanical properties underwater. The PU/GN composite films were prepared by evaporating a mixed solution of PU and GN on concave hexagonal honeycomb silicon templates. The mechanical properties of the composite films were determined by tensile test, and the wear resistance was evaluated by comparing the surface morphology before and after grind. By adjusting the content of graphite in the composite films, we found that the composite films containing 23 wt% GN had higher tensile strength and superior wear resistance. Moreover, this composite film showed an outstanding stability when expose to water. The impressive results along with simple preparation process made PU/GN composite films had potential applications in robust underwater functional materials.

New ASTM Standards for Nondestructive Testing of Aerospace Composites

NASA Technical Reports Server (NTRS)

Waller, Jess M.; Saulsberry, Regor L.

2010-01-01

Problem: Lack of consensus standards containing procedural detail for NDE of polymer matrix composite materials: I. Flat panel composites. II. Composite components with more complex geometries a) Pressure vessels: 1) composite overwrapped pressure vessels (COPVs). 2) composite pressure vessels (CPVs). III. Sandwich core constructions. Metal and brittle matrix composites are a possible subject of future effort.

Torque Limit for Bolted Joint for Composites. Part A; TTTC Properties of Laminated Composites

NASA Technical Reports Server (NTRS)

Zhao, Yi

2003-01-01

The existing design code for torque limit of bolted joints for composites at Marshall Space Flight Center is MSFC-STD-486B, which was originally developed in 1960s for metallic materials. The theoretical basis for this code was a simplified mechanics analysis, which takes into account only the bolt, nut and washers, but not the structural members to be connected. The assumption was that metallic materials would not fail due to the bearing stress at the contact area between washer and the mechanical member. This is true for metallic materials; but for composite materials the results could be completely different. Unlike most metallic materials, laminated composite materials have superior mechanical properties (such as modulus and strength) in the in-plane direction, but not in the out-of-plane, or through-the-thickness (TTT) direction. During the torquing, TTT properties (particularly compressive modulus and compressive strength) play a dominant role in composite failure. Because of this concern, structural design engineers at Marshall are currently using a compromised empirical approach: using 50% of the torque value for composite members. Companies like Boeing is using a similar approach. An initial study was conducted last summer on this topic to develop theoretical model(s) that takes into consideration of composite members. Two simplified models were developed based on stress failure criterion and strain failure criterion, respective. However, these models could not be used to predict the torque limit because of the unavailability of material data, specifically, through-the-thickness compression (TTTC) modulus and strength. Therefore, the task for this summer is to experimentally determine the TTTC properties. Due to the time limitation, only one material has been tested: IM7/8552 with [0 degrees,plus or minus 45 degrees, 90 degree ] configuration. This report focuses the test results and their significance, while the experimentation will be described in a separate report by Mr. Kris Kostreva.

Characterization of B4C-composite-reinforced aluminum alloy composites

NASA Astrophysics Data System (ADS)

Singh, Ram; Rai, R. N.

2018-04-01

Dry sliding wear tests conducted on Pin-on-disk wear test machine. The rotational speed of disc is ranging from (400-600rpm) and under loads ranging from (30-70 N) the contact time between the disc and pin is constant for each pin specimen of composites is 15 minute. In all manufacturing industries the uses of composite materials has been increasing globally, In the present study, an aluminum 5083 alloy is used as the matrix and 5% of weight percentage of Boron Carbide (B4C) as the reinforcing material. The composite is produced using stir casting technique. This is cost effective method. The aluminum 5083 matrix can be strengthened by reinforcing with hard ceramic particles like silicon carbide and boron carbide. In this experiment, aluminum 5083 alloy is selected as one of main material for making parts of the ship it has good mechanical properties, good corrosion resistance and it is can welded very easily and does have good strength. The samples are tested for hardness and tensile strength. The mechanical properties like Hardness can be increased by reinforcing aluminum 5083alloy 5% boron carbide (B4C) particles and tensile strength. Finally the Scanning Electron Microscope (SEM) analysis and EDS is done, which helps to study topography of composites and it produces images of a sample by scanning it with a focused beam of electrons and the presence of composition found in the matrix.

Development and characterization of self-healing carbon fabric/ionomer composite through stitched polymeric artificial muscle

NASA Astrophysics Data System (ADS)

Gabriel, Mark Joseph

Typical cracks in composite materials are hard to detect, because they may be very small or occur inside the material. This study investigates the development and characterization of carbon fiber and an ionomer, self-healing, laminate composite, enhanced with stitched artificial muscle elements. Although the carbon fiber is used as a structural reinforcement, the carbon fiber can also act as a resistive heating element in order to activate the healing elements in a Close-Then-Heal (CTH) approach. However in this study, hot air in an oven was used to activate the, SurlynRTM 8940, self-healing matrix. Artificial muscle was prepared from commercial fishing line to stitch reinforce the carbon laminate composite in the Z plane. Holes were drilled into the final composite and the muscle was stitched into the composite for active reinforcement. Differential scanning calorimetry was used to characterize the matrix and fishing line properties. The resulting smart composite was subjected to low velocity impact tests and consequential damage before healing in an oven, followed by three point bending flexure tests. Cracks in the carbon fiber reinforcement formed more easily than expected after impact because the holes were drilled to facilitate the muscle stitching. The matrix material could heal, but the reinforcement carbon could not. Several equipment issues and failures limited the amount of samples that could be created to continue testing with new parameters.

Identification of explosives and drugs and inspection of material defects with THz radiation

NASA Astrophysics Data System (ADS)

Zhang, Cunlin; Mu, Kaijun; Jiang, Xue; Jiao, Yueying; Zhang, Liangliang; Zhou, Qingli; Zhang, Yan; Shen, Jingling; Zhao, Guoshong; Zhang, X.-C.

2008-03-01

We report the sensing of explosive materials and illicit drugs by using terahertz time-domain spectroscopy (THz-TDS) and imaging. Several explosive materials, such as γ-HNIW, RDX, 2,4-DNT, TNT, Nitro-aniline, and illicit drugs, such as methamphetamine (MA) etc were researched here. Non-destructive testing, as one of the major applications of THz imaging, can be applied to an area of critical need: the testing of aerospace materials. Composite materials such as carbon fiber are widely used in this industry. The nature of their use requires technologies that are able to differentiate between safe and unsafe materials, due to either manufacturing tolerance or damage acquired while in use. In this paper, we discuss the applicability of terahertz (THz) imaging systems to this purpose, focusing on graphite fiber composite materials, carbon silicon composite materials and so on. We applied THz imaging technology to evaluate the fire damage to a variety of carbon fiber composite samples. Major carbon fiber materials have polarization-dependent reflectivity in THz frequency range, and we show how the polarization dependence changes versus the burned damage level. Additionally, time domain information acquired through a THz time-domain spectroscopy (TDS) system provides further information with which to characterize the damage. We also detect fuel tank insulation foam panel defects with pulse and continuous-wave (CW) terahertz system.

Studies of the Surface Treatment and Sizing of Carbon Fiber Surfaces on the Mechanical Properties of Composites Containing Carbon Fibers

NASA Technical Reports Server (NTRS)

Sherwood, Peter M. A.; Lease, Kevin B.; Locke, James E.; Tomblin, John S.; Wang, Youqi

1996-01-01

Carbon fiber reinforced composites are materials where carbon fibers are used to reinforce a matrix to produce a light and strong material with important applications in the aerospace industry. There are many aspects of the preparation of these materials that would benefit from a study which combines the research of groups involved in the production, testing and analysis of these materials, and studies of the basic surface chemistry involved. This final reports presents the results of a project that has developed a collaboration between groups in all three of the major research universities in the State of Kansas, and promises to lead to a collaborative program that covers the major aspects of composite development and application. Sherwood has provided initial fiber surface treatment and sizing together with fiber and composite surface analysis; Lease, Tomblin and Wang have worked together toward the goal of preparing pre-preg and fabrication of laminated panels; Locke has developed computational models to evaluate the effect of surface treatment (and chemistry) on mechanical properties; Lease, Tomblin and Wang have worked together to perform all necessary mechanical testing. The research has been focused on materials that would benefit the High Speed Civil Transport (HSCT) program. The group has visited Dr. Howard Maars and his colleagues at NASA Langley, and has focused their studies on the NASA requirements discussed in this meeting. An important development, requested by NASA scientists, has been the acquisition and study of K3B as a matrix material for the composites. The project has led to the successful acquisition and surface analysis of K3B, together with the successful deposition of this material onto surface oxidized carbon fibers. Mechanical testing, modelling and the construction of composite preparation equipment has been achieved during the grant period.

Post-irradiation hardness development, chemical softening, and thermal stability of bulk-fill and conventional resin-composites.

PubMed

Alshali, Ruwaida Z; Salim, Nesreen A; Satterthwaite, Julian D; Silikas, Nick

2015-02-01

To measure bottom/top hardness ratio of bulk-fill and conventional resin-composite materials, and to assess hardness changes after dry and ethanol storage. Filler content and kinetics of thermal decomposition were also tested using thermogravimetric analysis (TGA). Six bulk-fill (SureFil SDR, Venus bulk fill, X-tra base, Filtek bulk fill flowable, Sonic fill, and Tetric EvoCeram bulk-fill) and eight conventional resin-composite materials (Grandioso flow, Venus Diamond flow, X-flow, Filtek Supreme Ultra Flowable, Grandioso, Venus Diamond, TPH Spectrum, and Filtek Z250) were tested (n=5). Initial and 24h (post-cure dry storage) top and bottom microhardness values were measured. Microhardness was re-measured after the samples were stored in 75% ethanol/water solution. Thermal decomposition and filler content were assessed by TGA. Results were analysed using one-way ANOVA and paired sample t-test (α=0.05). All materials showed significant increase of microhardness after 24h of dry storage which ranged from 100.1% to 9.1%. Bottom/top microhardness ratio >0.9 was exhibited by all materials. All materials showed significant decrease of microhardness after 24h of storage in 75% ethanol/water which ranged from 14.5% to 74.2%. The extent of post-irradiation hardness development was positively correlated to the extent of ethanol softening (R(2)=0.89, p<0.001). Initial thermal decomposition temperature assessed by TGA was variable and was correlated to ethanol softening. Bulk-fill resin-composites exhibit comparable bottom/top hardness ratio to conventional materials at recommended manufacturer thickness. Hardness was affected to a variable extent by storage with variable inorganic filler content and initial thermal decomposition shown by TGA. The manufacturer recommended depth of cure of bulk-fill resin-composites can be reached based on the microhardness method. Characterization of the primary polymer network of a resin-composite material should be considered when evaluating its stability in the aqueous oral environment. Copyright © 2014 Elsevier Ltd. All rights reserved.

Damage tolerant functionally graded materials for advanced wear and friction applications

NASA Astrophysics Data System (ADS)

Prchlik, Lubos

The research work presented in this dissertation focused on processing effects, microstructure development, characterization and performance evaluation of composite and graded coatings used for friction and wear control. The following issues were addressed. (1) Definition of prerequisites for a successful composite and graded coating formation by means of thermal spraying. (2) Improvement of characterization methods available for homogenous thermally sprayed coating and their extension to composite and graded materials. (3) Development of novel characterization methods specifically for FGMs, with a focus on through thickness property measurement by indentation and in-situ curvature techniques. (4) Design of composite materials with improved properties compared to homogenous coatings. (5) Fabrication and performance assessment of FGM with improved wear and impact damage properties. Materials. The materials studied included several material systems relevant to low friction and contact damage tolerant applications: MO-Mo2C, WC-Co cermets as materials commonly used sliding components of industrial machinery and NiCrAlY/8%-Yttria Partially Stabilized Zirconia composites as a potential solution for abradable sections of gas turbines and aircraft engines. In addition, uniform coatings such as molybdenum and Ni5%Al alloy were evaluated as model system to assess the influence of microstructure variation onto the mechanical property and wear response. Methods. The contact response of the materials was investigated through several techniques. These included methods evaluating the relevant intrinsic coating properties such as elastic modulus, residual stress, fracture toughness, scratch resistance and tests measuring the abrasion and friction-sliding behavior. Dry-sand and wet two-body abrasion testing was performed in addition to traditional ball on disc sliding tests. Among all characterization techniques the spherical indentation deserved most attention and enabled to measure elastic-plastic properties of uniform and graded structures. In-situ curvature method used for residual stress and elastic modulus measurement was extended from uniform coatings to coatings with compositional/property gradients. Properties of composite and graded materials were measured using the inverse analysis. Conclusions. The specifics of the elastic-plastic response for thermally sprayed coatings were demonstrated. These included the strain dependence of elastic modulus and damage accumulation related to unloading/reloading loop formation. The measurement of elastic-plastic characteristics of composite coatings revealed the mixing and bonding mechanisms unique for thermally sprayed materials. Microstructural and compositional factors governing the frictional vs. abrasion response of carbide-metallic composite coatings were described. The measurement of abrasion resistance and friction sliding properties demonstrated that grading of cermet and ceramic coatings by adding moderate amount of metallic alloys can enhance elastic-properties radically and have a beneficial effect onto the coating performance.

Self-Repairing Mechanism of MUF/Epoxy Microcapsules for Epoxy Material

NASA Astrophysics Data System (ADS)

Ni, Zhuo; Lin, Yuhao; Zhou, Xiaobo

2017-12-01

In this paper, a post curing reaction for the microcapsule/epoxy composite material and the conditions of thermal treatment for self-healing process were studied by differential scanning calorimetry (DSC). The condition of thermal treatment for post curing (60°C, 2 hours) was employed to fully cure the epoxy composite. Damage mechanism for the epoxy material was demonstrated via data simulation and three-point bending experiment for the stress distribution reveals that micro-cracks are more likely to be generated on the central region in stress concentration area of two constrained boundaries and the numbers of micro-cracks are reduced from the central area to the two ends of the material. Self-repairing performances of MUF microcapsule/epoxy composite materials were characterized using both destructive bending tests and non-destructive DMA measurements. Self-healing efficiencies of the composites embedded 2% and 5% microcapsule content measured by DMA are 101% and 104% respectively which are close to those results of 104% and 113% correspondingly measured by bending tests. Crack formation and development, core material releasing for MUF microcapsules and physiochemical process of the self-repairing were investigated by using OM, fluorescent technique and infrared microscope. These provide detailed evidences and important information on self-healing mechanism of the microcapsule/epoxy self-repairing material.

Margin adaptation of indirect composite inlays fabricated on flexible dies.

PubMed

Price, R B; Gerrow, J D

2000-03-01

Indirect composite restorations can be made in 1 appointment using a flexible die. Interactions between different impression materials and flexible die materials may affect the accuracy of fit and margin adaptation of the restoration. This study compared the margin adaptation of composite inlays made using the following 5 impression/flexible die material combinations; condensation silicone/polyvinyl siloxane (CS/PVS), wash viscosity polyvinyl siloxane/medium or heavy viscosity polyvinyl siloxane (PVS/PVS), irreversible hydrocolloid impression/medium viscosity polyvinyl siloxane (IH/PVS), wash viscosity polyvinyl siloxane impression/polyether (PVS/PE), with composite inlays made using a control system of a wash viscosity polyvinyl siloxane impression and a type IV stone die. For each test and control system, 10 impressions were made of a class II composite inlay preparation in a metal master die. One die was made from each impression and one composite inlay was made and finished on each die (a total of 60 inlays). Inlays were placed on the master die and the margin opening at the buccal, distal, and gingival sites was recorded with a measuring microscope (x40 magnification). The overall mean +/- SD margin openings of inlays made from the systems were as follows: PVS wash/PVS heavy viscosity 149.5 +/- 107. 4 microm; PVS wash/PVS medium viscosity 87.4 +/- 63.0 microm; IH/PVS medium viscosity 76.7 +/- 48.9 microm; CS/PVS 73.3 +/- 48.7 microm, PVS wash viscosity/PE 64.0 +/- 44.3 microm, PVS wash viscosity/stone 53.9 +/- 48.3 microm. Composite inlays made using the PVS wash viscosity/PVS heavy viscosity system had significantly larger distal, gingival, and overall mean margin openings than all other inlays (ANOVA and Fisher PLSD test; P =.05). The separating medium required between some impression and die materials did not work consistently. Composite inlays fabricated on dies made of material different than the impression material had mean buccal, distal, gingival, and overall margin openings < or =100 microm. Composite inlays made on the CS/PVS, IH/PVS medium viscosity, PVS wash viscosity/PE flexible dies, and control PVS wash viscosity/stone dies had statistically similar (P =.05) mean buccal, distal, gingival, and overall mean margin openings that were < or =100 microm. Composite inlays made on dies that were made of the same type of material as the impression material (PVS/PVS) had mean gingival margin openings >100 microm that were significantly larger than all other systems tested (P =.05).

Carbon Nanofiber Cement Sensors to Detect Strain and Damage of Concrete Specimens Under Compression.

PubMed

Galao, Oscar; Baeza, F Javier; Zornoza, Emilio; Garcés, Pedro

2017-11-24

Cement composites with nano-additions have been vastly studied for their functional applications, such as strain and damage sensing. The capacity of a carbon nanofiber (CNF) cement paste has already been tested. However, this study is focused on the use of CNF cement composites as sensors in regular concrete samples. Different measuring techniques and humidity conditions of CNF samples were tested to optimize the strain and damage sensing of this material. In the strain sensing tests (for compressive stresses up to 10 MPa), the response depends on the maximum stress applied. The material was more sensitive at higher loads. Furthermore, the actual load time history did not influence the electrical response, and similar curves were obtained for different test configurations. On the other hand, damage sensing tests proved the capability of CNF cement composites to measure the strain level of concrete samples, even for loads close to the material's strength. Some problems were detected in the strain transmission between sensor and concrete specimens, which will require specific calibration of each sensor one attached to the structure.

Application of advanced material systems to composite frame elements

NASA Technical Reports Server (NTRS)

Llorente, Steven; Minguet, Pierre; Fay, Russell; Medwin, Steven

1992-01-01

A three phase program has been conducted to investigate DuPont's Long Discontinuous Fiber (LDF) composites. Additional tests were conducted to compare LDF composites against toughened thermosets and a baseline thermoset system. Results have shown that the LDF AS4/PEKK offers improved interlaminar (flange bending) strength with little reduction in mechanical properties due to the discontinuous nature of the fibers. In the third phase, a series of AS4/PEKK LDF C-section curved frames (representing a typical rotorcraft light frame) were designed, manufactured and tested. Specimen reconsolidation after 'stretch forming' and frame thickness were found to be key factors in this light frame's performance. A finite element model was constructed to correlate frame test results with expected strain levels determined from material property tests. Adequately reconsolidated frames performed well and failed at strain levels at or above baseline thermoset material test strains. Finally a cost study was conducted which has shown that the use of LDF for this frame would result in a significant cost savings, for moderate to large lot sizes compared with the hand lay-up of a thermoset frame.

Crash Testing of Helicopter Airframe Fittings

NASA Technical Reports Server (NTRS)

Clarke, Charles W.; Townsend, William; Boitnott, Richard

2004-01-01

As part of the Rotary Wing Structures Technology Demonstration (RWSTD) program, a surrogate RAH-66 seat attachment fitting was dynamically tested to assess its response to transient, crash impact loads. The dynamic response of this composite material fitting was compared to the performance of an identical fitting subjected to quasi-static loads of similar magnitude. Static and dynamic tests were conducted of both smaller bench level and larger full-scale test articles. At the bench level, the seat fitting was supported in a steel fixture, and in the full-scale tests, the fitting was integrated into a surrogate RAH-66 forward fuselage. Based upon the lessons learned, an improved method to design, analyze, and test similar composite material fittings is proposed.

Modification of the Interfacial Interaction between Carbon Fiber and Epoxy with Carbon Hybrid Materials

PubMed Central

Yu, Kejing; Wang, Menglei; Wu, Junqing; Qian, Kun; Sun, Jie; Lu, Xuefeng

2016-01-01

The mechanical properties of the hybrid materials and epoxy and carbon fiber (CF) composites were improved significantly as compared to the CF composites made from unmodified epoxy. The reasons could be attributed to the strong interfacial interaction between the CF and the epoxy composites for the existence of carbon nanomaterials. The microstructure and dispersion of carbon nanomaterials were characterized by transmission electron microscopy (TEM) and optical microscopy (OM). The results showed that the dispersion of the hybrid materials in the polymer was superior to other carbon nanomaterials. The high viscosity and shear stress characterized by a rheometer and the high interfacial friction and damping behavior characterized by dynamic mechanical analysis (DMA) indicated that the strong interfacial interaction was greatly improved between fibers and epoxy composites. Remarkably, the tensile tests presented that the CF composites with hybrid materials and epoxy composites have a better reinforcing and toughening effect on CF, which further verified the strong interfacial interaction between epoxy and CF for special structural hybrid materials. PMID:28335217

Hygrothermal properties of composites

NASA Technical Reports Server (NTRS)

Arsenovic, Petar

1996-01-01

The testing procedure and acceptance criteria for outgassing selection of materials to be used in spacecraft has been reviewed. Outgassing testing should be conducted according to ASTM Standard E 595-90. In general, materials with CVCM less than or equal to 0.10% and TML less than or equal to 1.00% are acceptable for space applications. Next, test data on several types of graphite-epoxy composite materials are presented over time at various relative humidity levels at room temperature for moisture absorption, and under vacuum at several temperatures for moisture desorption (outgassing). The data can be accurately represented by simple equations which are useful for materials characterization. Finally, a laser dilatometer systems of extremely high sensitivity and accuracy was assembled and used to measure the coefficient of thermal expansion (CTE) of several types of graphite-epoxy structures, culminating in the ability to perform loading and thermal expansion tests on a prototype optical bench.

Custom Machines Advance Composite Manufacturing

NASA Technical Reports Server (NTRS)

2012-01-01

Here is a brief list of materials that NASA will not be using to construct spacecraft: wood, adobe, fiberglass, bone. While it might be obvious why these materials would not make for safe space travel, they do share a common characteristic with materials that may well be the future foundation of spacecraft design: They all are composites. Formed of two or more unlike materials - such as cellulose and lignin in the case of wood, or glass fibers and plastic resin in the case of fiberglass-composites provide enhanced mechanical and physical properties through the combination of their constituent materials. For this reason, composites are used in everything from buildings, bathtubs, and countertops to boats, racecars, and sports equipment. NASA continually works to develop new materials to enable future space missions - lighter, less expensive materials that can still withstand the extreme demands of space travel. Composites such as carbon fiber materials offer promising solutions in this regard, providing strength and stiffness comparable to metals like aluminum but with less weight, allowing for benefits like better fuel efficiency and simpler propulsion system design. Composites can also be made fatigue tolerant and thermally stable - useful in space where temperatures can swing hundreds of degrees. NASA has recently explored the use of composites for aerospace applications through projects like the Composite Crew Module (CCM), a composite-constructed version of the aluminum-lithium Multipurpose Crew Capsule. The CCM was designed to give NASA engineers a chance to gain valuable experience developing and testing composite aerospace structures.

Development and implementation of an automatic integration system for fibre optic sensors in the braiding process with the objective of online-monitoring of composite structures

NASA Astrophysics Data System (ADS)

Hufenbach, W.; Gude, M.; Czulak, A.; Kretschmann, Martin

2014-04-01

Increasing economic, political and ecological pressure leads to steadily rising percentage of modern processing and manufacturing processes for fibre reinforced polymers in industrial batch production. Component weights beneath a level achievable by classic construction materials, which lead to a reduced energy and cost balance during product lifetime, justify the higher fabrication costs. However, complex quality control and failure prediction slow down the substitution by composite materials. High-resolution fibre-optic sensors (FOS), due their low diameter, high measuring point density and simple handling, show a high applicability potential for an automated sensor-integration in manufacturing processes, and therefore the online monitoring of composite products manufactured in industrial scale. Integrated sensors can be used to monitor manufacturing processes, part tests as well as the component structure during product life cycle, which simplifies allows quality control during production and the optimization of single manufacturing processes.[1;2] Furthermore, detailed failure analyses lead to a enhanced understanding of failure processes appearing in composite materials. This leads to a lower wastrel number and products of a higher value and longer product life cycle, whereby costs, material and energy are saved. This work shows an automation approach for FOS-integration in the braiding process. For that purpose a braiding wheel has been supplemented with an appliance for automatic sensor application, which has been used to manufacture preforms of high-pressure composite vessels with FOS-networks integrated between the fibre layers. All following manufacturing processes (vacuum infiltration, curing) and component tests (quasi-static pressure test, programmed delamination) were monitored with the help of the integrated sensor networks. Keywords: SHM, high-pressure composite vessel, braiding, automated sensor integration, pressure test, quality control, optic-fibre sensors, Rayleigh, Luna Technologies

Cumulative Damage Model for Advanced Composite Materials.

DTIC Science & Technology

1984-03-09

Masters, J.L., "Investigation of Characteristic Damage States in Composites Laminat -s," ASME Paper No. 79-WA-AERO-4, 1978. [26] Jivinall, R.C., "Stress...AD-A144 84e CUMULATIVE DAMAGE MODEL FOR RDVRNCED COMPOSITE 1/2 MATERIRLS(U) DYNA EAST CORP PHILADELPHIA PA P C CHOU ET AL. 09 MAR 84 RFWRL-TR-84-4084...MICROCOPY RESOLUTION TEST CHART NATIONAL BUREAU OF STANDARDS- 1963-A AFWAL-TR-84-4004 •S CUMULATIVE DAMAGE MODEL FOR ADVANCED COMPOSITE MATERIALS PHASE II 0

Definition and Modeling of Critical Flaws in Graphite Fiber Reinforced Epoxy Resin Matrix Composite Materials.

DTIC Science & Technology

1978-01-01

14. "C" Scans of a Composite Plate after Fabrication, a Plate with End Tabs, and a Machined Specimen tIyj - - . I. NArc-7 6228-30 f 4... COMPOSITE MATERIALS 0I Prepared for: Approved by: Naval Air Development Center Warminster, PA 18974 January 1978 B. Walter Rosen, President ILUE BELL...Imperfections in Composite Structures. . . . . . . . . . . . . 41 2 Static Test Data for [(04/+452/7452/04)sIs AS/3501 Laminates With and Without

Mechanical behavior of carbon-carbon composites

NASA Technical Reports Server (NTRS)

Rozak, G. A.

1984-01-01

A general background, test plan, and some results of preliminary examinations of a carbon-carbon composite material are presented with emphasis on mechanical testing and inspection techniques. Experience with testing and evaluation was gained through tests of a low modulus carbon-carbon material, K-Karb C. The properties examined are the density - 1.55 g/cc; four point flexure strength in the warp - 137 MPa (19,800 psi) and the fill - 95.1 MPa (13,800 psi,) directions; and the warp interlaminar shear strength - 14.5 MPa (2100 psi). Radiographic evaluation revealed thickness variations and the thinner areas of the composite were scrapped. The ultrasonic C-scan showed attenuation variations, but these did not correspond to any of the physical and mechanical properties measured. Based on these initial tests and a survey of the literature, a plan has been devised to examine the effect of stress on the oxidation behavior, and the strength degradation of coated carbon-carbon composites. This plan will focus on static fatigue tests in the four point flexure mode in an elevated temperature, oxidizing environment.

Ablative material testing for low-pressure, low-cost rocket engines

NASA Technical Reports Server (NTRS)

Richter, G. Paul; Smith, Timothy D.

1995-01-01

The results of an experimental evaluation of ablative materials suitable for the production of light weight, low cost rocket engine combustion chambers and nozzles are presented. Ten individual specimens of four different compositions of silica cloth-reinforced phenolic resin materials were evaluated for comparative erosion in a subscale rocket engine combustion chamber. Gaseous hydrogen and gaseous oxygen were used as propellants, operating at a nominal chamber pressure of 1138 kPa (165 psi) and a nominal mixture ratio (O/F) of 3.3. These conditions were used to thermally simulate operation with RP-1 and liquid oxygen, and achieved a specimen throat gas temperature of approximately 2456 K (4420 R). Two high-density composition materials exhibited high erosion resistance, while two low-density compositions exhibited approximately 6-75 times lower average erosion resistance. The results compare favorably with previous testing by NASA and provide adequate data for selection of ablatives for low pressure, low cost rocket engines.

The effect of fibre loading and graphene on the mechanical properties of goat hair fibre epoxy composite

NASA Astrophysics Data System (ADS)

Jayaseelan, J.; Vijayakumar, K. R.; Ethiraj, N.; Sivabalan, T.; nallayan, W. Andrew

2017-12-01

Composite materials are heterogenous materials containing one or more solid phases. In recent years cost-effective composite making is an ideal task. Hence we have come out with a natural fibre composite, which contains goat hair and epoxy as a binding element, with the combination of Graphene as a main source of enhanced mechanical property. Fabrication of natural composite consists of five layers of goat hair sandwiched in epoxy matrix. These composites made are tested for mechanical properties including Tensile strength, Flexural strength, Inter laminar shear and Impact strength. The mechanical properties of the six composite sets are analyzed and reported.

Deployment Testing of Flexible Composite Hinges in Bi-Material Beams

NASA Technical Reports Server (NTRS)

Sauder, Jonathan F.; Trease, Brian

2016-01-01

Composites have excellent properties for strength, thermal stability, and weight. However, they are traditionally highly rigid, and when used in deployable structures require hinges bonded to the composite material, which increases complexity and opportunities for failure. Recent research in composites has found by adding an elastomeric soft matrix, often silicone instead of an epoxy, the composite becomes flexible. This work explores the deployment repeatability of silicone matrix composite hinges which join rigid composite beams. The hinges were found to have sub-millimeter linear deployment repeatability, and sub-degree angular deployment repeatability. Also, an interesting relaxation effect was discovered, as a hinges deployment error would decrease with time.

Strength and deformability of compressed concrete elements with various types of non-metallic fiber and rods reinforcement under static loading

NASA Astrophysics Data System (ADS)

Nevskii, A. V.; Baldin, I. V.; Kudyakov, K. L.

2015-01-01

Adoption of modern building materials based on non-metallic fibers and their application in concrete structures represent one of the important issues in construction industry. This paper presents results of investigation of several types of raw materials selected: basalt fiber, carbon fiber and composite fiber rods based on glass and carbon. Preliminary testing has shown the possibility of raw materials to be effectively used in compressed concrete elements. Experimental program to define strength and deformability of compressed concrete elements with non-metallic fiber reinforcement and rod composite reinforcement included design, manufacture and testing of several types of concrete samples with different types of fiber and longitudinal rod reinforcement. The samples were tested under compressive static load. The results demonstrated that fiber reinforcement of concrete allows increasing carrying capacity of compressed concrete elements and reducing their deformability. Using composite longitudinal reinforcement instead of steel longitudinal reinforcement in compressed concrete elements insignificantly influences bearing capacity. Combined use of composite rod reinforcement and fiber reinforcement in compressed concrete elements enables to achieve maximum strength and minimum deformability.

Attritional wear and abrasive surface alterations of composite resin materials in vitro.

PubMed

Göhring, T N; Besek, M J; Schmidlin, P R

2002-01-01

A laboratory study was performed with 232 specimens and 72 human enamel, 24 gold, 24 ceramic and 12 composite antagonists in 22 groups to test attritional and abrasive wear behavior of composite materials compared to wear behavior of human enamel. Belleglass HP, Concept Inlay/Onlay, Targis and Targis Upgrade 99 composite resin for lab-made restorations was tested as well as Tetric Ceram and FHC Merz light as resins for direct restorations. Natural human enamel specimens served as control. All specimens were subjected to long-term thermo-mechanical loading in a computer-controlled masticator, chemical degradation and toothbrush/toothpaste abrasion. Wear of specimen in occlusal contact area (OCA), contact-free occlusal area and wear of natural enamel cusps as well as antagonists made of gold, ceramic and composite in identical form was measured after 120,000, 240,000, 640,000 and 1200,000 load cycles. A qualitative SEM analysis was performed to support quantitative data. Belleglass HP and Targis Upgrade 99 restorative materials showed wear resistance comparable to human enamel when loaded with enamel cusps. Wear of Targis versus composite and gold antagonists was significantly higher (p<0.0001). Analysis of surface alterations showed hygroscopic expansion in all composite resins during the test. As a consequence of this study, necessity to further improve physical properties of composites for long lasting restorations was obvious. Beside of attritional wear in OCA, attention must be given to stable filler-matrix interfaces and prevention of water sorption.

Synthesis, Characterization, and Modeling of Nanotube Materials with Variable Stiffness Tethers

NASA Technical Reports Server (NTRS)

Frankland, S. J. V.; Herzog, M. N.; Odegard, G. M.; Gates, T. S.; Fay, C. C.

2004-01-01

Synthesis, mechanical testing, and modeling have been performed for carbon nanotube based materials. Tests using nanoindentation indicated a six-fold enhancement in the storage modulus when comparing the base material (no nanotubes) to the composite that contained 5.3 wt% of nanotubes. To understand how crosslinking the nanotubes may further alter the stiffness, a model of the system was constructed using nanotubes crosslinked with a variable stiffness tether (VST). The model predicted that for a composite with 5 wt% nanotubes at random orientations, crosslinked with the VST, the bulk Young's modulus was reduced by 30% compared to the noncrosslinked equivalent.

Mechanics Methodology for Textile Preform Composite Materials

NASA Technical Reports Server (NTRS)

Poe, Clarence C., Jr.

1996-01-01

NASA and its contractors have completed a program to develop a basic mechanics underpinning for textile composites. Three major deliverables were produced by the program: 1. A set of test methods for measuring material properties and design allowables; 2. Mechanics models to predict the effects of the fiber preform architecture and constituent properties on engineering moduli, strength, damage resistance, and fatigue life; and 3. An electronic data base of coupon type test data. This report describes these three deliverables.

The Experiment and Numerical Simulation of Composite Countersunk-head Fasteners Pull-through Mechanical Behavior

NASA Astrophysics Data System (ADS)

Mu, Junwu; Guan, Zhidong; Bian, Tianya; Li, Zengshan; Wang, Kailun; Liu, Sui

2014-10-01

Fasteners made of the anisotropic carbon/carbon (C/C) composite material have been developed for joining C/C composite material components in the high-temperature environment. The fastener specimens are fabricated from the C/C composites which are made from laminated carbon cloths with Z-direction carbon fibers being punctured as perform. Densification process cycles such as the thermal gradient chemical vapor infiltration (CVI) technology were repeated to obtain high density C/C composites fastener. The fasteners were machined parallel to the carbon cloths (X-Y direction). A method was proposed to test pull-through mechanical behavior of the countersunk-head C/C composite material fasteners. The damage morphologies of the fasteners were observed through the charge coupled device (CCD) and the scanning electron microscope (SEM). The internal micro-structure were observed through the high-resolution Mirco-CT systems. Finally, an excellent simulation of the C/C composite countersunk-head fasteners were performed with the finite element method (FEM), in which the damage evolution model of the fastener was established based on continuum damage mechanics. The simulation is correspond well with the test result . The damage evolution process and the relation between the countersunk depth and the ultimate load was investigated.

Experimental investigation of CNT effect on curved beam strength and interlaminar fracture toughness of CFRP laminates

NASA Astrophysics Data System (ADS)

Arca, M. A.; Coker, D.

2014-06-01

High mechanical properties and light weight structures of composite materials and advances in manufacturing processes have increased the use of composite materials in the aerospace and wind energy industries as a primary load carrying structures in complex shapes. However, use of composite materials in complex geometries such as L-shaped laminates creates weakness at the radius which causes delamination. Carbon nanotubes (CNTs) is preferred as a toughening materials in composite matrices due to their high mechanical properties and aspect ratios. However, effect of CNTs on curved beam strength (CBS) is not investigated in literature comprehensively. The objective of this study is to investigate the effect of CNT on Mode I and Mode II fracture toughness and CBS. L-shaped beams are fabric carbon/epoxy composite laminates manufactured by hand layup technique. Curved beam composite laminates were subjected to four point bending loading according to ASTM D6415/D6415M-06a. Double cantilever beam (DCB) tests and end notch flexure (ENF) tests were conducted to determine mode-I and mode-II fracture toughness, respectively. Preliminary results show that 3% CNT addition to the resin increased the mode-I fracture toughness by %25 and mode-II fracture toughness by %10 compared to base laminates. In contrast, no effect on curved beam strength was found.

Characterization of third-body media particles and their effect on in vitro composite wear

PubMed Central

Lawson, Nathaniel C.; Cakir, Deniz; Beck, Preston; Litaker, Mark S.; Burgess, John O.

2012-01-01

Objectives The purpose of this study was to compare four medium particles currently used for in vitro composite wear testing (glass and PMMA beads and millet and poppy seeds). Methods Particles were prepared as described in previous wear studies. Hardness of medium particles was measured with a nano-indentor, particle size was measured with a particle size analyzer, and the particle form was determined with light microscopy and image analysis software. Composite wear was measured using each type of medium and water in the Alabama wear testing device. Four dental composites were compared: a hybrid (Z100), flowable microhybrid (Estelite Flow Quick), micromatrix (Esthet-X), and nano-filled (Filtek Supreme Plus). The test ran for 100,000 cycles at 1.2Hz with 70N force by a steel antagonist. Volumetric wear was measured by non-contact profilometry. A two-way analysis of variance (ANOVA) and Tukey's test was used to compare both materials and media. Results Hardness values (GPa) of the particles are (glass, millet, PMMA, poppy respectively): 1.310(0.150), 0.279(.170), 0.279(0.095), and 0.226(0.146). Average particle sizes (μm) are (glass, millet, PMMA, poppy respectively): 88.35(8.24), 8.07(4.05), 28.95(8.74), and 14.08(7.20). Glass and PMMA beads were considerably more round than the seeds. During composite wear testing, glass was the only medium that produced more wear than the use of water alone. The rank ordering of the materials varied with each medium, however, the glass and PMMA bead medium allowed better discrimination between materials. Significance PMMA beads are a practical and relevant choice for composite wear testing because they demonstrate similar physical properties as seeds but reduce the variability of wear measurements. PMID:22578990

Nondestructive evaluation of a ceramic matrix composite material

NASA Technical Reports Server (NTRS)

Grosskopf, Paul P.; Duke, John C., Jr.

1992-01-01

Monolithic ceramic materials have proven their usefulness in many applications, yet, their potential for critical structural applications is limited because of their sensitivity to small imperfections. To overcome this extreme sensitivity to small imperfections, ceramic matrix composite materials have been developed that have the ability to withstand some distributed damage. A borosilicate glass reinforced with several layers of silicon-carbide fiber mat has been studied. Four-point flexure and tension tests were performed not only to determine some of the material properties, but also to initiate a controlled amount of damage within each specimen. Acousto-ultrasonic (AU) measurements were performed periodically during mechanical testing. This paper will compare the AU results to the mechanical test results and data from other nondestructive methods including acoustic emission monitoring and X-ray radiography. It was found that the AU measurements were sensitive to the damage that had developed within the material.

High performance structural laminate composite material for use to 1000.degree. F. and above, apparatus for and method of manufacturing same, and articles made with same

NASA Technical Reports Server (NTRS)

Seal, Ellis C. (Inventor); Biggs, Jr., Robert William (Inventor); Bodepudi, Venu Prasad (Inventor); Cranston, John A. (Inventor)

2003-01-01

A novel materials technology has been developed and demonstrated for providing a high modulus composite material for use to 1000.degree. F. and above. This material can be produced at 5-20% of the cost of refractory materials, and has higher structural properties. This technology successfully resolves the problem of thermal shock or ply lift, which limits traditional high temperature laminates (such as graphite/polyimide and graphite/phenolic) to temperatures of 550-650.degree. F. in thicker (0.25 and above) laminates. The technology disclosed herein is an enabling technology for the nose for the External Tank (ET) of the Space Shuttle, and has been shown to be capable of withstanding the severe environments encountered by the nose cone through wind tunnel testing, high temperature subcomponent testing, and full scale structural, dynamic, acoustic, and damage tolerance testing.

Impact response of composite materials

NASA Technical Reports Server (NTRS)

Tiwari, S. N.; Srinivasan, K.

1991-01-01

Composite materials composed of carbon fibers and resin matrices offer great promise in reducing the weight of aerospace structures. However they remain extremely vulnerable to out of plane impact loads, which lead to severe losses in strength and stiffness. The results of an experimental program, undertaken to investigate the low velocity impact damage tolerance of composite materials is presented. The objectives were to identify key neat resin/composite properties that lead to enhancement of composite impact damage tolerance and to find a small scale test that predicts compression after impact properties of panels. Five materials were selected for evaluation. These systems represented different classes of material behavior such as brittle epoxy, modified epoxies, and amorphous and semicrystalling thermoplastics. The influence of fiber properties on the impact performance was also studied in one material, i.e., in polyether ether ketone (PEEK). Several 24 and 48 ply quasi-isotropic and 24 ply orthotropic laminates were examined using an instrumented drop weight impactor. Correlations with post impact compression behavior were made.

Application of far infrared rare earth mineral composite materials to liquefied petroleum gas.

PubMed

Zhu, Dongbin; Liang, Jinsheng; Ding, Yan; Xu, Anping

2010-03-01

Far infrared rare earth mineral composite materials were prepared by the coprecipitation method using tourmaline, cerium acetate, and lanthanum acetate as raw materials. The results of Fourier transform infrared spectroscopy show that tourmaline modified with the rare earths La and Ce has a better far infrared emitting performance. Through XRD analysis, we attribute the improved far infrared emission properties of the tourmaline to the unit cell shrinkage of the tourmaline arising from La enhancing the redox properties of nano-CeO2. The effect of the composite materials on the combustion of liquefied petroleum gas (LPG) was studied by the flue gas analysis and water boiling test. Based on the results, it was found that the composite materials could accelerate the combustion of LPG, and that the higher the emissivity of the rare earth mineral composite materials, the better the effects on combustion of LPG. In all activation styles, both air and LPG to be activated has a best effect, indicating the activations having a cumulative effect.

NASA Glenn Research Center UEET (Ultra-Efficient Engine Technology) Program: Agenda and Abstracts

NASA Technical Reports Server (NTRS)

Manthey, Lri

2001-01-01

Topics discussed include: UEET Overview; Technology Benefits; Emissions Overview; P&W Low Emissions Combustor Development; GE Low Emissions Combustor Development; Rolls-Royce Low Emissions Combustor Development; Honeywell Low Emissions Combustor Development; NASA Multipoint LDI Development; Stanford Activities In Concepts for Advanced Gas Turbine Combustors; Large Eddy Simulation (LES) of Gas Turbine Combustion; NASA National Combustion Code Simulations; Materials Overview; Thermal Barrier Coatings for Airfoil Applications; Disk Alloy Development; Turbine Blade Alloy; Ceramic Matrix Composite (CMC) Materials Development; Ceramic Matrix Composite (CMC) Materials Characterization; Environmental Barrier Coatings (EBC) for Ceramic Matrix Composite (CMC) Materials; Ceramic Matrix Composite Vane Rig Testing and Design; Ultra-High Temperature Ceramic (UHTC) Development; Lightweight Structures; NPARC Alliance; Technology Transfer and Commercialization; and Turbomachinery Overview; etc.

Microshear Bond Strength of Tri-Calcium Silicate-based Cements to Different Restorative Materials.

PubMed

Cengiz, Esra; Ulusoy, Nuran

To evaluate the microshear bond strength of tri-calcium silicate-based materials to different restorative materials. Thirty-five disks of TheraCal LC and Biodentine were fabricated using teflon molds according to manufacturers' instructions. Then the specimens were randomly divided into 7 groups according to the materials applied: Fuji IX, Fuji II, Equia Fil, Vertise Flow, Filtek Bulk Fill Posterior Restorative, Filtek Z250 with Prime&Bond NT and with Clearfil SE Bond. All restorative materials were placed onto the disks using tygon tubes. Following a storage period, the specimens underwent microshear bond strength testing in a universal testing machine, and fracture modes were analyzed. Data were analyzed using one-way ANOVA and Tukey's post-hoc test. For all restorative materials, TheraCal LC showed significantly higher μSBS values compared to Biodentine. GIC based materials showed the lowest μSBS for TheraCal and Biodentine. For Biodentine, Filtek Z250 applied with Prime&Bond NT and Filtek Bulk Fill Posterior Restorative applied with Scotchbond Universal Adhesive exhibited the highest μSBS, while Filtek Z250 applied with Clearfil SE Bond revealed the highest bond strength to TheraCal LC. For all restorative materials tested in this study, TheraCal LC showed higher μSBS compared to Biodentine. For both TheraCal LC and Biodentine, the placement of GIC-based materials prior to composite resin restorations might decrease the bond strength. Composite resins applied with self-etching adhesives increased the bond strength of TheraCal LC; however, for Biodentine, application of etch-and-rinse adhesives may improve the adhesion of composite resins.

The effect of fiber treatment on abrasive wear properties of palm fiber reinforced epoxy composite

NASA Astrophysics Data System (ADS)

Razak, Muhammad Firdaus Abdul; Bakar, Mimi Azlina Abu; Kasolang, Salmiah; Ahmad, Mohamad Ali

2017-12-01

Oil palm industries generate at least 30 million tons of lignocellulosic biomass annually in the form of oil palm trunks (OPT), empty fruit bunches (EFB), oil palm fronds (OPF) and palm pressed fibres (PPF). The palm fiber is one of the natural fibers used as reinforcement in composite materials in order to decrease environmental issues and promotes utilization of renewable resources. This paper presents a study on the effect of alkaline treatment on wear properties of palm fiber reinforced epoxy resin composite. Abrasive wear testing was deployed to investigate the wear profile of the composite surfaces. Testing was carried out which focused on the effect of alkaline treatment to the palm fiber under different amounts of fiber loading i.e. 1 wt%, 3 wt%, 5 wt% and 7 wt%. The palm fibers were soaked into 6 % of alkaline solution or natrium hydroxide (NaOH) for 12 hours. The fiber was treated in order to remove amorphous materials such as hemicelluloses, lignins and pectins of the fiber. The wear test samples were fabricated using hand lay-up technique and cured at room temperature for 24 hours. Surface roughness of the composite material was also measured using the surface measuring instrument. Dry sliding wear test was performed at room temperature at a constant velocity of 1.4 m/s with a constant load of 10 N by using the Abrasion Test Machine. Result shows that 5 wt% and 7 wt% treated palm fiber loadings have better specific wear rate compared to lower fiber loadings. The finding of this study contributes towards material development and utilization in promoting `waste into wealth' which is in line with national aspiration.

Composite Materials for Low-Temperature Applications

NASA Technical Reports Server (NTRS)

2008-01-01

Composite materials with improved thermal conductivity and good mechanical strength properties should allow for the design and construction of more thermally efficient components (such as pipes and valves) for use in fluid-processing systems. These materials should have wide application in any number of systems, including ground support equipment (GSE), lunar systems, and flight hardware that need reduced heat transfer. Researchers from the Polymer Science and Technology Laboratory and the Cryogenics Laboratory at Kennedy Space Center were able to develop a new series of composite materials that can meet NASA's needs for lightweight materials/composites for use in fluid systems and also expand the plastic-additive markets. With respect to thermal conductivity and physical properties, these materials are excellent alternatives to prior composite materials and can be used in the aerospace, automotive, military, electronics, food-packaging, and textile markets. One specific application of the polymeric composition is for use in tanks, pipes, valves, structural supports, and components for hot or cold fluid-processing systems where heat flow through materials is a problem to be avoided. These materials can also substitute for metals in cryogenic and other low-temperature applications. These organic/inorganic polymeric composite materials were invented with significant reduction in heat transfer properties. Decreases of 20 to 50 percent in thermal conductivity versus that of the unmodified polymer matrix were measured. These novel composite materials also maintain mechanical properties of the unmodified polymer matrix. These composite materials consist of an inorganic additive combined with a thermoplastic polymer material. The intrinsic, low thermal conductivity of the additive is imparted into the thermoplastic, resulting in a significant reduction in heat transfer over that of the base polymer itself, yet maintaining most of the polymer's original properties. Normal polymer processing techniques can turn these composite materials into unique, custom parts for ground support, Shuttle, and Constellation needs. We fabricated test specimens of the composite and base materials for thermal and mechanical characterization and found that the strength of the composite material at nominal-percentage loading remained relatively unchanged from the base material.

Impact Behavior of Composite Fan Blade Leading Edge Subcomponent with Thermoplastic Polyurethane Interleave

NASA Technical Reports Server (NTRS)

Miller, Sandi G.; Roberts, Gary D.; Kohlman, Lee W.; Heimann, Paula J.; Pereira, J. Michael; Ruggeri, Charles R.; Martin, Richard E.; McCorkle, Linda S.

2015-01-01

Impact damage tolerance and damage resistance is a critical metric for application of polymer matrix composites where failure caused by impact damage could compromise structural performance and safety. As a result, several materials and/or design approaches to improve impact damage tolerance have been investigated over the past several decades. Many composite toughening methodologies impart a trade-off between increased fracture toughness and compromised in-plane strength and modulus. In large part, mechanical tests to evaluate composite damage tolerance include static methods such as Mode I, Mode II, and mixed mode failures. However, ballistic impact damage resistance does not always correlate with static properties. The intent of this paper is to evaluate the influence of a thermoplastic polyurethane veil interleave on the static and dynamic performance of composite test articles. Static coupon tests included tension, compression, double cantilever beam, and end notch flexure. Measurement of the resistance to ballistic impact damage were made to evaluate the composites response to high speed impact. The interlayer material showed a decrease of in-plane performance with only a moderate improvement to Mode I and Mode II fracture toughness. However, significant benefit to impact damage tolerance was observed through ballistic tests.

Multifunctional Characteristics of Carbon Nanotube (CNT) Yarn Composites

NASA Technical Reports Server (NTRS)

Hernandez, Corey D.; Zhang, Mei; Fang, Shaoli; Baughman, Ray H.; Gates, Thomas S.; Kahng, Seun K.

2006-01-01

By forming composite structures with Carbon Nanotube (CNT) yarns we achieve materials capable of measuring strain and composite structures with increased mechanical strength. The CNT yarns used are of the 2-ply and 4-ply variety with the yarns having diameters of about 15-30 micrometers. The strain sensing characteristics of the yarns are investigated on test beams with the yarns arranged in a bridge configuration. Additionally, the strain sensing properties are also investigated on yarns embedded on the surface of a flexible membrane. Initial mechanical strength tests also show an increase in the modulus of elasticity of the composite materials while incurring a weight penalty of less than one-percent. Also presented are initial temperature characterizations of the yarns.

Detection of defects in multi-layered aramid composites by ultrasonic IR thermography

NASA Astrophysics Data System (ADS)

Pracht, Monika; Swiderski, Waldemar

2017-10-01

In military applications, laminates reinforced with aramid, carbon, and glass fibers are used for the construction of protection products against light ballistics. Material layers can be very different by their physical properties. Therefore, such materials represent a difficult inspection task for many traditional techniques of non-destructive testing (NDT). Defects which can appear in this type of many-layered composite materials usually are inaccuracies in gluing composite layers and stratifications or delaminations occurring under hits of fragments and bullets. IR thermographic NDT is considered as a candidate technique to detect such defects. One of the active IR thermography methods used in nondestructive testing is vibrothermography. The term vibrothermography was created in the 1990s to determine the thermal test procedures designed to assess the hidden heterogeneity of structural materials based on surface temperature fields at cyclical mechanical loads. A similar procedure can be done with sound and ultrasonic stimulation of the material, because the cause of an increase in temperature is internal friction between the wall defect and the stimulation mechanical waves. If the cyclic loading does not exceed the flexibility of the material and the rate of change is not large, the heat loss due to thermal conductivity is small, and the test object returns to its original shape and temperature. The most commonly used method is ultrasonic stimulation, and the testing technique is ultrasonic infrared thermography. Ultrasonic IR thermography is based on two basic phenomena. First, the elastic properties of defects differ from the surroundings, and acoustic damping and heating are always larger in the damaged regions than in the undamaged or homogeneous areas. Second, the heat transfer in the sample is dependent on its thermal properties. In this paper, both modelling and experimental results which illustrate the advantages and limitations of ultrasonic IR thermography in inspecting multi-layered aramide composite materials will be presented.

[Research on bond durability among different core materials and zirconia ceramic cemented by self-adhesive resin cements].

PubMed

Xinyu, Luo; Xiangfeng, Meng

2017-02-01

This research estimated shear bond durability of zirconia and different substrates cemented by two self-adhesive resin cements (Clearfil SA Luting and RelyX U100) before and after aging conditioning. Machined zirconia ceramic discs were cemented with four kinds of core material (cobalt-chromium alloy, flowable composite resin core material, packable composite resin, and dentin) with two self-adhesive resin cements (Clearfil SA Luting and RelyX U100). All specimens were divided into eight test groups, and each test group was divided into two subgroups. Each subgroup was subjected to shear test before and after 10 000 thermal cycles. All factors (core materials, cements, and thermal cycle) significantly influenced bond durability of zirconia ceramic (P<0.00 1). After 10 000 thermal cycles, significant decrease was not observed in shear bond strength of cobalt-chromium alloy luted with Clearfil SA Luting (P>0.05); observed shear bond strength was significantly higher than those of other substrates (P<0.05). Significantly higher shear bond strength was noted in Clearfil SA Luting luted with cobalt-chromium alloy, flowable composite resin core material, and packable composite resin than that of RelyX U100 (P<0.05). However, significant difference was not observed in shear bond strength of dentin luted with Clearfil SA Luting and RelyX U100 (P>0.05). Different core materials and self-adhesive resin cements can significantly affect bond durability of zirconia ceramic. 
.

Optimization of sensor introduction into laminated composite materials

NASA Astrophysics Data System (ADS)

Schaaf, Kristin; Nemat-Nasser, Sia

2008-03-01

This work seeks to extend the functionality of the composite material beyond that of simply load-bearing and to enable in situ sensing, without compromising the structural integrity of the host composite material. Essential to the application of smart composites is the issue of the mechanical coupling of the sensor to the host material. Here we present various methods of embedding sensors within the host composite material. In this study, quasi-static three-point bending (short beam) and fatigue three-point bending (short beam) tests are conducted in order to characterize the effects of introducing the sensors into the host composite material. The sensors that are examined include three types of polyvinylidene fluoride (PVDF) thin film sensors: silver ink with a protective coating of urethane, silver ink without a protective coating, and nickel-copper alloy without a protective coating. The methods of sensor integration include placement at the midplane between the layers of prepreg material as well as a sandwich configuration in which a PVDF thin film sensor is placed between the first and second and nineteenth and twentieth layers of prepreg. Each PVDF sensor is continuous and occupies the entire layer, lying in the plane normal to the thickness direction in laminated composites. The work described here is part of an ongoing effort to understand the structural effects of integrating microsensor networks into a host composite material.

Composites Materials and Manufacturing Technologies for Space Applications

NASA Technical Reports Server (NTRS)

Vickers, J. H.; Tate, L. C.; Gaddis, S. W.; Neal, R. E.

2016-01-01

Composite materials offer significant advantages in space applications. Weight reduction is imperative for deep space systems. However, the pathway to deployment of composites alternatives is problematic. Improvements in the materials and processes are needed, and extensive testing is required to validate the performance, qualify the materials and processes, and certify components. Addressing these challenges could lead to the confident adoption of composites in space applications and provide spin-off technical capabilities for the aerospace and other industries. To address the issues associated with composites applications in space systems, NASA sponsored a Technical Interchange Meeting (TIM) entitled, "Composites Materials and Manufacturing Technologies for Space Applications," the proceedings of which are summarized in this Conference Publication. The NASA Space Technology Mission Directorate and the Game Changing Program chartered the meeting. The meeting was hosted by the National Center for Advanced Manufacturing (NCAM)-a public/private partnership between NASA, the State of Louisiana, Louisiana State University, industry, and academia, in association with the American Composites Manufacturers Association. The Louisiana Center for Manufacturing Sciences served as the coordinator for the TIM.

Influence of copper composition on mechanical properties of biodegradable material Mg-Zn-Cu for orthopedic application

NASA Astrophysics Data System (ADS)

Purniawan, A.; Maulidiah, H. M.; Purwaningsih, H.

2018-04-01

Implant is usually used as a treatment of bone fracture. At the moment, non-biodegradable implants is still widely employed in this application. Non-biodegradable implant requires re-surgery to retrieve implants that are installed in the body. It increase the cost and it is painful for the patient itself. In order to solve the problem, Mg-based biodegradable metals is developing so that the material will be compatible with body and gradually degrade in patient's body. However, magnesium has several disadvantages such as high degradation rates and low mechanical properties when compared to the mechanical properties of natural bone. Therefore, it is necessary to add elements into the magnesium alloy. In this research, copper (Cu) was alloyed in Mg alloy based biodegradable material. In addition, Cu is not only strengthening the structure but also for supporting element for the immune system, antibacterial and antifungal. The purpose of this research is to improve mechanical properties of Mg-based biodegradable material using Cu alloying. Powder metallurgy method was used to fabricate the device. The variation used in this research is the composition of Cu (0.5, 1, and 1.5% Cu). The porosity test was performed using apparent porosity test, compressive test and hardness test to know the mechanical properties of the alloy, and the weightless test to find out the material degradation rate. Based on the results can be conclude that Mg-Zn-Cu alloy material with 1% Cu composition is the most suitable specimen to be applied as a candidate for orthopedic devices material with hardness value is 393.6 MPa. Also obtained the value of the compressive test is 153 MPa.

Influence of different staining beverages on color stability, surface roughness and microhardness of silorane and methacrylate-based composite resins.

PubMed

Karaman, Emel; Tuncer, Duygu; Firat, Esra; Ozdemir, Oguz Suleyman; Karahan, Sevilay

2014-05-01

To investigate the influence of different staining beverages on color stability, surface roughness and microhardness of silorane and methacrylate-based composite resins. Three different composite resins (Filtek Silorane, Filtek P60, Filtek Supreme XT) were tested. Thirty cylindrical specimens (10 × 2 mm) per material were prepared and polished with a series of aluminum-oxide polishing disks. Each group was then randomly subdivided into three groups according to the test beverages: distilled water (control), cola and coffee. The samples were immersed into different beverages for 15 days. Color, surface roughness and microhardness values were measured by a spectrophotometer, prophylometer and Vickers hardness device respectively, at baseline and after 15 days. The data were subjected to statistical analysis. Immersion in coffee resulted in a significant discoloration for all the composites tested, although the color change was lower in Filtek Silorane than that of MBCs (p < 0.05). All the composites tested showed similar surface roughness changes after immersion in different beverages (p > 0.05). Besides coffee caused more roughness change than others. Immersion in coffee caused highest microhardness change in Filtek Supreme XT (p < 0.05). Cola and coffee altered, to some degree, the color, surface roughness and/or microhardness of the tested resin composites, depending on the characteristics of the materials.

In vitro wear rates of materials under different loads and varying pH.

PubMed

Shabanian, Mitra; Richards, Lindsay C

2002-06-01

Despite the need for information about the wear characteristics of restorative materials, there have been few systemic studies of the factors that influence the rate of material wear. This study compared the wear rates of enamel and 3 tooth-colored restorative materials under different loads (0, 3.2, 6.7, and 9.95 kg) and pH levels (1.2, 3.3, and 7.0). An electromechanical tooth wear machine was used so that standard restorations representing 3 materials could be worn by opposing enamel under controlled conditions. The wear rates of enamel, composite (Z100), a conventional glass ionomer cement (Fuji IX), and a resin-modified glass ionomer cement (Fuji II LC) were compared at a range of loads (0 to 9.95 kg) and pH levels (1.2 to 7.0) and also at different sites across each restoration. Ten specimens were randomly assigned to each experimental group. Wear assessment was performed with a modified light microscope to quantify the height changes at defined points across wear facets. Four-way analysis of variance was used to compare wear rates among materials, pH levels, loads, and sites. Post-hoc t tests identified significant differences between specific pairs of experimental conditions (P<.05). The wear rates of enamel and the other test materials varied significantly with pH (P<.0001), load (P<.0001), and type of material (P<.0001). Enamel wear was influenced most by varied pH, whereas the composite was least affected by acid. The conventional glass ionomer cement was more susceptible than the composite to the effects of varied pH; the acid susceptibility of the resin-modified glass ionomer cement was generally between that of the composite and conventional glass ionomer cement. Enamel and the conventional glass ionomer cement were affected similarly by load. The composite was more resistant than the conventional glass ionomer cement to wear at higher loads; the resin-modified glass ionomer cement exhibited intermediate load resistance. Within the limitations of this study, the 3 test materials were more resistant than enamel to acid, with the composite demonstrating the lowest susceptibility to acid. The acid- and load-resistance of the resin-modified glass ionomer cement was consistently less than that of the composite and greater than that of the conventional glass ionomer cement.

Stress and Damage in Polymer Matrix Composite Materials Due to Material Degradation at High Temperatures

NASA Technical Reports Server (NTRS)

McManus, Hugh L.; Chamis, Christos C.

1996-01-01

This report describes analytical methods for calculating stresses and damage caused by degradation of the matrix constituent in polymer matrix composite materials. Laminate geometry, material properties, and matrix degradation states are specified as functions of position and time. Matrix shrinkage and property changes are modeled as functions of the degradation states. The model is incorporated into an existing composite mechanics computer code. Stresses, strains, and deformations at the laminate, ply, and micro levels are calculated, and from these calculations it is determined if there is failure of any kind. The rationale for the model (based on published experimental work) is presented, its integration into the laminate analysis code is outlined, and example results are given, with comparisons to existing material and structural data. The mechanisms behind the changes in properties and in surface cracking during long-term aging of polyimide matrix composites are clarified. High-temperature-material test methods are also evaluated.

Fatigue testing of low-cost fiberglass composite wind turbine blade materials

NASA Technical Reports Server (NTRS)

Hofer, K. E.; Bennett, L. C.

1981-01-01

The static and fatigue behavior of transverse filament tape (TFT) fiberglass/epoxy and TFT/polyester composites was established by the testing of specimens cut from panels fabricated by a filament winding process used for the construction of large experimental wind turbine blades.

Damage and fracture in fabric-reinforced composites under quasi-static and dynamic bending

NASA Astrophysics Data System (ADS)

Ullah, H.; Harland, A. R.; Silberschmidt, V. V.

2013-07-01

Fabric-reinforced polymer composites used in sports products can be exposed to different in-service conditions such as large deformations caused by quasi-static and dynamic loading. Composite materials subjected to such bending loads can demonstrate various damage modes - matrix cracking, delamination and, ultimately, fabric fracture. Damage evolution in composites affects both their in-service properties and performance that can deteriorate with time. Such behaviour needs adequate means of analysis and investigation, the main approaches being experimental characterisation and non-destructive examination of internal damage in composite laminates. This research deals with a deformation behaviour and damage in carbon fabric-reinforced polymer (CFRP) laminates caused by quasi-static and dynamic bending. Experimental tests were carried out to characterise the behaviour of a CFRP material under large-deflection bending, first in quasi-static and then in dynamic conditions. Izod-type impact bending tests were performed on un-notched specimens of CFRP using a Resil impactor to assess the transient response and energy absorbing capability of the material. X-ray micro computed tomography (micro-CT) was used to analyse various damage modes in the tested specimens. X-ray tomographs revealed that through-thickness matrix cracking, inter-ply and intra-ply delamination such as tow debonding, and fabric fracture were the prominent damage modes both in quasi-static and dynamic test specimens. However, the inter-ply damage was localised at impact location in dynamically tested specimens, whereas in the quasi-static specimens, it spread almost over the entire interface.

Database of Mechanical Properties of Textile Composites

NASA Technical Reports Server (NTRS)

Delbrey, Jerry

1996-01-01

This report describes the approach followed to develop a database for mechanical properties of textile composites. The data in this database is assembled from NASA Advanced Composites Technology (ACT) programs and from data in the public domain. This database meets the data documentation requirements of MIL-HDBK-17, Section 8.1.2, which describes in detail the type and amount of information needed to completely document composite material properties. The database focuses on mechanical properties of textile composite. Properties are available for a range of parameters such as direction, fiber architecture, materials, environmental condition, and failure mode. The composite materials in the database contain innovative textile architectures such as the braided, woven, and knitted materials evaluated under the NASA ACT programs. In summary, the database contains results for approximately 3500 coupon level tests, for ten different fiber/resin combinations, and seven different textile architectures. It also includes a limited amount of prepreg tape composites data from ACT programs where side-by-side comparisons were made.

Influence of clamp-up force on the strength of bolted composite joints

NASA Astrophysics Data System (ADS)

Horn, Walter J.; Schmitt, Ron R.

1994-03-01

Composite materials offer the potential for a reduction in the number of individual parts and joints in a structure because large one-piece components can replace multipart assemblies. Nevertheless, there are many situations where composite parts must be joined and often mechanical fasteners provide the only practical method of joining those parts. The long-term strength of mechanically fastened joints of composite members can be directly affected by the clamp-up force of the fastener and thus perhaps by the relaxation of this force due to the viscoelastic character of the composite materials of the joint. Methods for predicting the effect of bolt clamp-up force relaxation on the strength of mechanically fastened joints of thermoplastic composite materials were investigated during the present study. A test program, using two thermoplastic composite materials, was conducted to determine the influence of clamp-up force on joint strength, to measure the relaxation of the joint clamp-up force with time, and to measure the change of joint strength as a function of time.

An investigation into the impact of cryogenic environment on mechanical stresses in FRP composites

NASA Astrophysics Data System (ADS)

Fifo, O.; Basu, B.

2015-07-01

Fibre reinforced polymer (FRP) composites are fast becoming a highly utilised engineering material for high performance applications due to their light weight and high strength. Carbon fibre and other high strength fibres are commonly used in design of aerospace structures, wind turbine blades, etc. and potentially for propellant tanks of launch vehicles. For the aforementioned fields of application, stability of the material is essential over a wide range of temperature particularly for structures in hostile environments. Many studies have been conducted, experimentally, over the last decade to investigate the mechanical behaviour of FRP materials at varying subzero temperature. Likewise, tests on aging and cycling effect (room to low temperature) on the mechanical response of FRP have been reported. However, a relatively lesser focused area has been the mechanical behaviour of FRP composites under cryogenic environment. This article reports a finite element method of investigating the changes in the mechanical characteristics of an FRP material when temperature based analysis falls below zero. The simulated tests are carried out using a finite element package with close material properties used in the cited literatures. Tensile test was conducted and the results indicate that the mechanical responses agree with those reported in the literature sited.

27 CFR 19.453 - Testing of denaturants.

Code of Federal Regulations, 2010 CFR

2010-04-01

... Denaturation § 19.453 Testing of denaturants. (a) Testing. Proprietors shall ensure that the materials they... shall be taken in such manner as to represent a true composite of the total lot being sampled. When... part 21, the proprietor shall not use the material unless he treats or manipulates the denaturant to...

Adhesive Defect Monitoring of Glass Fiber Epoxy Plate Using an Impedance-Based Non-Destructive Testing Method for Multiple Structures

PubMed Central

Na, Wongi S.; Baek, Jongdae

2017-01-01

The emergence of composite materials has revolutionized the approach to building engineering structures. With the number of applications for composites increasing every day, maintaining structural integrity is of utmost importance. For composites, adhesive bonding is usually the preferred choice over the mechanical fastening method, and monitoring for delamination is an essential factor in the field of composite materials. In this study, a non-destructive method known as the electromechanical impedance method is used with an approach of monitoring multiple areas by specifying certain frequency ranges to correspond to a certain test specimen. Experiments are conducted using various numbers of stacks created by attaching glass fiber epoxy composite plates onto one another, and two different debonding damage types are introduced to evaluate the performance of the multiple monitoring electromechanical impedance method. PMID:28629194

Composite Crew Module: Primary Structure

NASA Technical Reports Server (NTRS)

Kirsch, Michael T.

2011-01-01

In January 2007, the NASA Administrator and Associate Administrator for the Exploration Systems Mission Directorate chartered the NASA Engineering and Safety Center to design, build, and test a full-scale crew module primary structure, using carbon fiber reinforced epoxy based composite materials. The overall goal of the Composite Crew Module project was to develop a team from the NASA family with hands-on experience in composite design, manufacturing, and testing in anticipation of future space exploration systems being made of composite materials. The CCM project was planned to run concurrently with the Orion project's baseline metallic design within the Constellation Program so that features could be compared and discussed without inducing risk to the overall Program. This report discusses the project management aspects of the project including team organization, decision making, independent technical reviews, and cost and schedule management approach.

Composite Cryotank Technologies and Demonstration

NASA Technical Reports Server (NTRS)

Vickers, John

2015-01-01

NASA is exploring advanced composite materials and processes to reduce the overall cost and weight of liquid hydrogen (LH2) cryotanks while maintaining the reliability of existing metallic designs. The fundamental goal of the composite cryotank project was to provide new and innovative technologies that enable human space exploration to destinations beyond low-Earth orbit such as the Moon, near-Earth asteroids, and Mars. In September 2011, NASA awarded Boeing the contract to design, manufacture, and test two lightweight composite cryogenic propellant tanks. The all-composite tanks shown iare fabricated with an automated fiber placement machine using a prepreg system of IM7 carbon fiber/CYCOM 5320-1 epoxy resin. This is a resin system developed for out-of-autoclave applications. Switching from metallic to composite construction holds the potential to dramatically increase the performance capabilities of future space systems through a dramatic reduction in weight. Composite Cryotank Technologies and Demonstration testing was an agency-wide effort with NASA Marshall Space Flight Center (MSFC) leading project management, manufacturing, and test; Glenn Research Center leading the materials; and Langley Research Center leading the structures effort for this project. Significant contributions from NASA loads/stress personnel contributed to the understanding of thermal/mechanical strain response while undergoing testing at cryogenic temperatures. The project finalized in September 2014.

Experimental Techniques for Evaluating the Effects of Aging on Impact and High Strain Rate Properties of Triaxial Braided Composite Materials

NASA Technical Reports Server (NTRS)

Pereira, J. Michael; Roberts, Gary D.; Ruggeri, Charles R.; Gilat, Amos; Matrka, Thomas

2010-01-01

An experimental program is underway to measure the impact and high strain rate properties of triaxial braided composite materials and to quantify any degradation in properties as a result of thermal and hygroscopic aging typically encountered during service. Impact tests are being conducted on flat panels using a projectile designed to induce high rate deformation similar to that experienced in a jet engine fan case during a fan blade-out event. The tests are being conducted on as-fabricated panels and panels subjected to various numbers of aging cycles. High strain rate properties are being measured using a unique Hopkinson bar apparatus that has a larger diameter than conventional Hopkinson bars. This larger diameter is needed to measure representative material properties because of the large unit cell size of the materials examined in this work. In this paper the experimental techniques used for impact and high strain rate testing are described and some preliminary results are presented for both as-fabricated and aged composites.

Nondestructive inspection of bonded composite doublers for aircraft

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roach, D.; Moore, D.; Walkington, P.

1996-12-31

One major thrust in FAA`s National Aging Aircraft Research Program is to foster new technologies in civil aircraft maintenance. Recent DOD and other government developments in using bonded composite doublers on metal structures support the need for validation of such doubler applications on US certificated airplanes. In this study, a specific composite application was chosen on an L-1011 aircraft. Primary inspection requirements for these doublers include identifying disbonds between composite laminate and aluminum parent material, and delaminations in the composite laminate. Surveillance of cracks or corrosion in the parent aluminum material beneath the double is also a concern. No singlemore » NDI method can inspect for every flaw type, therefore we need to know NDI capabilities and limitations. This paper reports on a series of NDI tests conducted on laboratory test structures and on a fuselage section from a retired L-1011. Application of ultrasonics, x-ray, and eddy current to composite doublers and results from test specimens loaded to provide a changing flaw profile, are presented in this paper. Development of appropriate inspection calibration standards are also discussed.« less

Effect of Cold Forging on Microstructure and MechanicalProperties of Al/SiC Composites

NASA Astrophysics Data System (ADS)

Hanamantraygouda, M. B.; Shivakumar, B. P., Dr; Siddappa, P. N.; Sampathkumar, L.; Prashanth, L.

2018-02-01

The objective of this work was to investigate the effect of cold forging on mechanical properties and microstructural study of Al MMCs, at different wt% of SiC and forging cycle. The Al-SiC composite material was fabricated by stir casting method at different weight percentage of SiC such as 2.5, 5, 7.5 and 10%. Further, the deformation characteristics during open-die forging of Al-SiC composite at cold conditions was investigated. Cast and forged composite material was subjected to hardness test, tensile test and impact test. The grain size, microstructure behaviour was investigated using optical microscope. The results show that hardness and strength of Al-SiC composite increases and ductility decreases as compared to Al alloy in both as-cast and forged conditions. Optical microscope images showed that the distribution of SiC in Al matrix was more homogeneous in a forged composite as compared to cast one and reduction of porosity was found. Further, it showed that due to forging cycle the grain size was reduced by 30% to 35% from initial size.

New materials for high temperature turbines; ONERA's DS composites confronted with blade problems

NASA Technical Reports Server (NTRS)

Bibring, H.

1977-01-01

ONERA's refractory DS composites were cited as materials required for use in advanced aircraft turbines, operating at high temperatures. These materials were found to be reliable in the construction of turbine blades. Requirements for a blade material in aircraft turbines operating at higher temperatures were compared with the actual performance as found in COTAC DS composite testing. The structure and properties of the more fully developed 74 and 741 types were specified. High temperature structural stability, impact of thermal and mechanical fatigue, oxidation resistance and coating capability were thoroughly evaluated. The problem of cooling passages in DS eutectic blades is also outlined.

Emissivity Results on High Temperature Coatings for Refractory Composite Materials

NASA Technical Reports Server (NTRS)

Ohlhorst, Craig W.; Vaughn, Wallace L.; Daryabeigi, Kamran; Lewis, Ronald K.; Rodriguez, Alvaro C.; Milhoan, James D.; Koenig, John R.

2007-01-01

The directional emissivity of various refractory composite materials considered for application for reentry and hypersonic vehicles was investigated. The directional emissivity was measured at elevated temperatures of up to 3400 F using a directional spectral radiometric technique during arc-jet test runs. A laboratory-based relative total radiance method was also used to measure total normal emissivity of some of the refractory composite materials. The data from the two techniques are compared. The paper will also compare the historical database of Reinforced Carbon-Carbon emissivity measurements with emissivity values generated recently on the material using the two techniques described in the paper.

Active thermography in qualitative evaluation of protective materials.

PubMed

Gralewicz, Grzegorz; Wiecek, Bogusław

2009-01-01

This is a study of the possibilities of a qualitative evaluation of protective materials with active thermography. It presents a simulation of a periodic excitation of a multilayer composite material. Tests were conducted with lock-in thermography on Kevlar composite consisting of 16 layers of Kevlar fabric reinforced with formaldehyde resin with implanted delamination defects. Lock-in thermography is a versatile tool for nondestructive evaluation. It is a fast, remote and nondestructive procedure. Hence, it was used to detect delaminations in the composite structure of materials used in the production of components designed for personal protection. This method directly contributes to an improvement in safety.

GROWING ALTERNATIVE SUSTAINABLE BUILDINGS: BIO-COMPOSITE PRODUCTS FROM NATURAL FIBER, BIODEGRADABLE AND RECYCLABLE POLYMER MATERIALS FOR LOAD-BEARING CONSTRUCTION COMPONENTS

EPA Science Inventory

The project is an integrative educational and research project that will revolutionize design and construction methods towards more sustainable buildings. The project will develop and test new product design concepts using bio-composite materials in load-bearing and fa&cced...

A new experimental method for the accelerated characterization of composite materials

NASA Technical Reports Server (NTRS)

Yeow, Y. T.; Morris, D. H.; Brinson, H. F.

1978-01-01

The use of composite materials for a variety of practical structural applications is presented and the need for an accelerated characterization procedure is assessed. A new experimental and analytical method is presented which allows the prediction of long term properties from short term tests. Some preliminary experimental results are presented.

Robotic and Multiaxial Testing for the Constitutive Characterization of Composites

Treesearch

John Michopoulos; Athanasios Iliopoulos; John Hermanson

2012-01-01

As wind energy production drives the manufacturing of wind turbine blades, the utilization of glass and carbon fiber composites as a material of choice continuousiy increases. Consequently, the needs for accurate structural design and material qualification and certification as well as the needs for aging predictions furlher underline the need for accurate constitutive...

Structural materials from lunar simulants through thermal liquefaction

NASA Technical Reports Server (NTRS)

Desai, Chandra S.; Girdner, Kirsten

1992-01-01

Thermal liquefaction that allows development of intermediate ceramic composites from a lunar simulant with various admixtures is used to develop structural materials for construction on the moon. Bending and compressive properties of resulting composites are obtained from laboratory tests and evaluated with respect to the use of three different types and fibers.

Macro Scale Independently Homogenized Subcells for Modeling Braided Composites

NASA Technical Reports Server (NTRS)

Blinzler, Brina J.; Goldberg, Robert K.; Binienda, Wieslaw K.

2012-01-01

An analytical method has been developed to analyze the impact response of triaxially braided carbon fiber composites, including the penetration velocity and impact damage patterns. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. Currently, each shell element is considered to be a smeared homogeneous material. The commercial transient dynamic finite element code LS-DYNA is used to conduct the simulations, and a continuum damage mechanics model internal to LS-DYNA is used as the material constitutive model. To determine the stiffness and strength properties required for the constitutive model, a top-down approach for determining the strength properties is merged with a bottom-up approach for determining the stiffness properties. The top-down portion uses global strengths obtained from macro-scale coupon level testing to characterize the material strengths for each subcell. The bottom-up portion uses micro-scale fiber and matrix stiffness properties to characterize the material stiffness for each subcell. Simulations of quasi-static coupon level tests for several representative composites are conducted along with impact simulations.

Ten-year ground exposure of composite materials used on the Bell Model 206L helicopter flight service program

NASA Technical Reports Server (NTRS)

Baker, Donald J.

1994-01-01

Residual strength results are presented for four composite material systems that have been exposed for up to 10 years to the environment at five different locations on the North American continent. The exposure locations are near where the Bell Model 206L helicopters, which participated in a flight service program sponsored by NASA Langley Research Center and the U.S. Army, were flying in daily commercial service. The composite material systems are (1) Kevlar-49 fabric/F-185 epoxy; (2) Kevlar-49 fabric/LRF-277 epoxy; (3) Kevlar-49 fabric/CE-306 epoxy; and (4) T-300 graphite/E-788 epoxy. Six replicates of each material were removed and tested after 1, 3, 5, 7, and 10 years of exposure. The average baseline strength was determined from testing six as-fabricated specimens. More than 1700 specimens have been tested. All specimens that were tested to determine their strength were painted with a polyurethane paint. Each set of specimens also included an unpainted panel for observing the weathering effects on the composite materials. A statistically based procedure has been used to determine the strength value above which at least 90 percent of the population is expected to fall with a 95-percent confidence level. The computed compression strengths are 80 to 90 percent of the baseline (no-exposure) strengths. The resulting compression strengths are approximately 8 percent below the population mean strengths. The computed short-beam-shear strengths are 83 to 92 percent of the baseline (no-exposure) strengths. The computed tension strength of all materials is 93 to 97 percent of the baseline (no-exposure) strengths.

A generalized methodology to characterize composite materials for pyrolysis models

NASA Astrophysics Data System (ADS)

McKinnon, Mark B.

The predictive capabilities of computational fire models have improved in recent years such that models have become an integral part of many research efforts. Models improve the understanding of the fire risk of materials and may decrease the number of expensive experiments required to assess the fire hazard of a specific material or designed space. A critical component of a predictive fire model is the pyrolysis sub-model that provides a mathematical representation of the rate of gaseous fuel production from condensed phase fuels given a heat flux incident to the material surface. The modern, comprehensive pyrolysis sub-models that are common today require the definition of many model parameters to accurately represent the physical description of materials that are ubiquitous in the built environment. Coupled with the increase in the number of parameters required to accurately represent the pyrolysis of materials is the increasing prevalence in the built environment of engineered composite materials that have never been measured or modeled. The motivation behind this project is to develop a systematic, generalized methodology to determine the requisite parameters to generate pyrolysis models with predictive capabilities for layered composite materials that are common in industrial and commercial applications. This methodology has been applied to four common composites in this work that exhibit a range of material structures and component materials. The methodology utilizes a multi-scale experimental approach in which each test is designed to isolate and determine a specific subset of the parameters required to define a material in the model. Data collected in simultaneous thermogravimetry and differential scanning calorimetry experiments were analyzed to determine the reaction kinetics, thermodynamic properties, and energetics of decomposition for each component of the composite. Data collected in microscale combustion calorimetry experiments were analyzed to determine the heats of complete combustion of the volatiles produced in each reaction. Inverse analyses were conducted on sample temperature data collected in bench-scale tests to determine the thermal transport parameters of each component through degradation. Simulations of quasi-one-dimensional bench-scale gasification tests generated from the resultant models using the ThermaKin modeling environment were compared to experimental data to independently validate the models.

Diagnostics of Polymer Composite Materials and Analysis of Their Production Technology by Using the Method of Acoustic Emission

NASA Astrophysics Data System (ADS)

Bashkov, O. V.; Protsenko, A. E.; Bryanskii, A. A.; Romashko, R. V.

2017-09-01

The strength properties of glass-fiber-reinforced plastics produced by vacuum and vacuum autoclave molding techniques are studied. Based on acoustic emission data, a method of diagnostic and prediction of the bearing capacity of polymer composite materials by using data from three-point bending tests is developed. The method is based on evaluating changes in the exponent of a power function relating the total acoustic emission to the test stress.

Effect of Er,Cr:YSGG laser on the surface of composite restoratives during in-office tooth bleaching.

PubMed

Dionysopoulos, Dimitrios; Strakas, Dimitrios; Tsitrou, Effrosyni; Tolidis, Kosmas; Koumpia, Effimia

2016-07-01

The aim of this in vitro study was to investigate the effect of Er,Cr:YSGG laser on the surface roughness and microhardness of various composite restoratives during in-office tooth bleaching. Five highly viscous composite restoratives and three flowable composite restoratives were investigated. Thirty cylindrical specimens of each material were made using Teflon molds. The specimens of each composite were randomly divided into three groups (n = 10). Group 1 specimens did not receive bleaching treatment, group 2 received a conventional in-office bleaching treatment, and group 3 received a laser-assisted in-office bleaching treatment using an Er,Cr:YSGG laser. Two-way ANOVA was used to determine significant interactions between materials and bleaching methods. One-way ANOVA and Tukey's post hoc test were used to compare the mean surface microhardness and roughness between materials for each treatment group (a = 0.05). Τhere were no significant differences in surface microhardness between the two bleached experimental groups for all the tested composites (p > 0.05). The reduction of surface microhardness after bleaching procedures ranged from 0.72 to 16.93 % for the specimens received conventional treatment and from 1.30 to 11.51 % for those received laser-assisted treatment. Moreover, there were no significant differences in Ra values between the experimental groups (p > 0.05) in all cases. The increase of surface roughness after the bleaching treatments was negligible and was between 0.43 and 4.78 %. The use of Er,Cr:YSGG laser during in-office tooth bleaching treatment did not affect the surface microhardness and roughness of the tested composite restorative materials.

Composite Materials Characterization and Development at AFWAL

NASA Technical Reports Server (NTRS)

Browning, C. E.

1984-01-01

The development of test methodology for characterizing matrix dominated failure modes is discussed emphasizing issues of matrix cracking, delamination under static loading, and the relationship of composite properties to matrix properties. Both strength characterization and classical techniques of linear elastic fracture mechanics were examined. Materials development studies are also discussed. Major areas of interest include acetylene-terminated and bismaleimide resins for 350 to 450 deg use, thermoplastics development, and failure resistant composite concepts.

The ultimate state of polymeric materials and laminated and fibrous composites under asymmetric high-cycle loading

NASA Astrophysics Data System (ADS)

Golub, V. P.; Pogrebniak, A. D.; Kochetkova, E. S.

2008-01-01

The prediction of the high-cycle fatigue strength of polymeric and composite materials in asymmetric loading is considered. The problem is solved on the basis of a nonlinear model of ultimate state allowing us to describe all typical forms of the diagrams of ultimate stresses. The material constants of the model are determined from the results of fatigue tests in symmetric reversed cycling, in a single fatigue test with the minimum stress equal to zero, and in a short-term strength test. The fatigue strength characteristics of some polymers, glass-fiber laminates, glass-fiber-reinforced plastics, organic-fiber-reinforced plastics, and wood laminates in asymmetric tension-compression, bending, and torsion have been calculated and approved experimentally.

Material properties and fractography of an indirect dental resin composite.

PubMed

Quinn, Janet B; Quinn, George D

2010-06-01

Determination of material and fractographic properties of a dental indirect resin composite material. A resin composite (Paradigm, 3M-ESPE, MN) was characterized by strength, static elastic modulus, Knoop hardness, fracture toughness and edge toughness. Fractographic analyses of the broken bar surfaces was accomplished with a combination of optical and SEM techniques, and included determination of the type and size of the failure origins, and fracture mirror and branching constants. The flexure test mean strength+/-standard deviation was 145+/-17 MPa, and edge toughness, T(e), was 172+/-12N/mm. Knoop hardness was load dependent, with a plateau at 0.99+/-0.02 GPa. Mirrors in the bar specimens were measured with difficulty, resulting in a mirror constant of approximately 2.6 MPa m(1/2). Fracture in the bar specimens initiated at equiaxed material flaws that had different filler concentrations that sometimes were accompanied by partial microcracks. Using the measured flaw sizes, which ranged from 35 to 100 microm in size, and using estimates of the stress intensity shape factors, fracture toughness was estimated to be 1.1+/-0.2 MPa m(1/2). Coupling the flexure tests with fractographic examination enabled identification of the intrinsic strength limiting flaws. The same techniques could be useful in determining if clinical restorations of similar materials fail from the same causes. The existence of a strong load-dependence of the Knoop hardness of the resin composite is not generally mentioned in the literature, and is important for material comparisons and wear evaluation studies. Finally, the edge toughness test was found promising as a quantitative measure of resistance to edge chipping, an important failure mode in this class of materials. Copyright (c) 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Composite panel development at JPL

NASA Technical Reports Server (NTRS)

Mcelroy, Paul; Helms, Rich

1988-01-01

Parametric computer studies can be use in a cost effective manner to determine optimized composite mirror panel designs. An InterDisciplinary computer Model (IDM) was created to aid in the development of high precision reflector panels for LDR. The materials properties, thermal responses, structural geometries, and radio/optical precision are synergistically analyzed for specific panel designs. Promising panels designs are fabricated and tested so that comparison with panel test results can be used to verify performance prediction models and accommodate design refinement. The iterative approach of computer design and model refinement with performance testing and materials optimization has shown good results for LDR panels.

The effect of instrument lubricant on the diametral tensile strength and water uptake of posterior composite restorative material.

PubMed

Patel, J; Granger, C; Parker, S; Patel, M

2017-01-01

This in-vitro study investigated the effect of 'instrument lubricants' used during placement of composite restorative material, on the diametral tensile strength (DTS) and water uptake of composite specimens. 300 posterior composite cylindrical specimens were manufactured: 60 with each instrument lubricant (ethanol, 3-step, 2-step and 1-step 'bonding agent') and 60 with no lubricant (controls). Each set of 60 specimens was evenly allocated to one of the following test groups (n=100/group): Group 1 - tested for DTS immediately after manufacture; Groups 2 and 3 - tested for DTS after immersion in phosphate-buffered saline (PBS) for 1 and 12-weeks respectively, using a Universal Instron machine. Water uptake was assessed gravimetrically. Data were statistically analysed with two-way ANOVA and Tukey's post hoc test (α=0.05). The mean DTS and percentage weight change of composite specimens ranged between 32.49-53.14MPa and 0.51-1.36% and varied with lubricant used and time incubated in PBS. All control groups exhibited significantly higher DTS (MPa) (groups 1-3: 53.17±1.78; 50.64±1.85; 45.17±1.77) and lower percentage weight change (groups 2-3: 0.51±0.03; 0.61±0.01) than specimens placed with an instrument lubricant, with significant differences between certain lubricant groups. Data from the present study suggest that the use of instrument lubricant may adversely effect the DTS and water uptake of composite restorative material. The use of instrument lubricants to aid composite placement is widespread however based on the data obtained it is suggested that discontinuing or limiting the use of instrument lubricants, and if necessary using the 'bonding agent' from a 3-step adhesive system is recommended as results suggest this has the least deleterious effect upon material properties.​. Copyright © 2016 Elsevier Ltd. All rights reserved.

Surface Hardness of Dental Composite Resin Restorations in Response to Preventive Agents.

PubMed

Al-Samadani, Khalid H

2016-12-01

To assess the impact of using preventive mouthwash agents on the surface hardness of various resins composites. Hundred specimens were prepared from five types of composite resin material in a Teflon mold. Five specimens from each type of restorative materials (Herculite XRV Ultra, Estelite Σ Quick, Z Hermack, Versa Comp Sultan, and Empress Direct IPS) were evaluated posttreatment with immersion in four types of preventive mouthwashes gels and rinses - group 1: Flocare gel (0.4% stannous fluoride), group 2: Pascal gel (topical APF fluoride), group 3: Pro-relief mouthwash (Na fluoride), and group 4: Plax Soin mouthwash (Na fluoride) - at 37°C in a dark glass container at 24, 48, and 72 hours. Surface hardness measurement was made for each tested material. Statistically, we analyzed the mean values with one-way analysis of variance (ANOVA) and Tukey's test, with significance level of p < 0.05. All composite resin materials showed decrease in their surface hardness with the time elapsed (24, 48, and 72 hours) postimmersion in the preventive mouthwashes and gels except the Herculite XRV Ultra and Versa Comp Sultan materials. Flocare gel group showed increase in the surface hardness after 48 hours of immersion than the other periods and in Estelite Σ Quick after 72 hours. There was significant differences in all materials tested with the immersion in the preventive mouthwashes and gels, such as Flocare gel (0.4% stannous fluoride), Pro-relief mouthwash (Na fluoride), and Plax Soin mouthwash (Na fluoride) except Pascal gel (topical APF fluoride) (p > 0.05), at time intervals mentioned earlier (p < 0.05). The effect of preventive mouthwashes and gels on resin composite materials was decreased surface hardness with the time elapse of immersion for all materials except the Flocare gel group, which contains 0.4% stannous fluoride as a preventive ingredient increases the surface hardness after 48 h for Herculite XRV Ultra and Versa Comp Sultan and Estelite Σ Quick after 72 hours. The preventive agents in the form of mouthwash and gel are used to prevent oral diseases that affect the surface hardness of composite resin, and this leads to occlusion, color stability, and surface roughness.

Natural Kenaf Fiber Reinforced Composites as Engineered Structural Materials

NASA Astrophysics Data System (ADS)

Dittenber, David B.

The objective of this work was to provide a comprehensive evaluation of natural fiber reinforced polymer (NFRP)'s ability to act as a structural material. As a chemical treatment, aligned kenaf fibers were treated with sodium hydroxide (alkalization) in different concentrations and durations and then manufactured into kenaf fiber / vinyl ester composite plates. Single fiber tensile properties and composite flexural properties, both in dry and saturated environments, were assessed. Based on ASTM standard testing, a comparison of flexural, tensile, compressive, and shear mechanical properties was also made between an untreated kenaf fiber reinforced composite, a chemically treated kenaf fiber reinforced composite, a glass fiber reinforced composite, and oriented strand board (OSB). The mechanical properties were evaluated for dry samples, samples immersed in water for 50 hours, and samples immersed in water until saturation (~2700 hours). Since NFRPs are more vulnerable to environmental effects than synthetic fiber composites, a series of weathering and environmental tests were conducted on the kenaf fiber composites. The environmental conditions studied include real-time outdoor weathering, elevated temperatures, immersion in different pH solutions, and UV exposure. In all of these tests, degradation was found to be more pronounced in the NFRPs than in the glass FRPs; however, in nearly every case the degradation was less than 50% of the flexural strength or stiffness. Using a method of overlapping and meshing discontinuous fiber ends, large mats of fiber bundles were manufactured into composite facesheets for structural insulated panels (SIPs). The polyisocyanurate foam cores proved to be poorly matched to the strength and stiffness of the NFRP facesheets, leading to premature core shear or delamination failures in both flexure and compressive testing. The NFRPs were found to match well with the theoretical stiffness prediction methods of classical lamination theory, finite element method, and Castigliano's method in unidirectional tension and compression, but are less accurate for the more bond-dependent flexural and shear properties. With the acknowledged NFRP matrix bonding issues, the over-prediction of these theoretical models indicates that the flexural stiffness of the kenaf composite may be increased by up to 40% if a better bond between the fiber and matrix can be obtained. The sustainability of NFRPs was examined from two perspectives: environmental and socioeconomic. While the kenaf fibers themselves possess excellent sustainability characteristics, costing less while possessing a lesser environmental impact than the glass fibers, the vinyl ester resin used in the composites is environmentally hazardous and inflated the cost and embodied energy of the composite SIPs. Consistent throughout all the designs was a correlation between the respective costs of the raw materials and the respective environmental impacts. The socioeconomic study looked at the sustainability of natural fiber reinforced composite materials as housing materials in developing countries. A literature study on the country of Bangladesh, where the fibers in this study were grown, showed that the jute and kenaf market would benefit from the introduction of a value-added product like natural fiber composites. The high rate of homeless and inadequately housed in Bangladesh, as well as in the US and throughout the rest of the world, could be somewhat alleviated if a new, affordable, and durable material were introduced. While this study found that natural fiber composites possess sufficient mechanical properties to be adopted as primary structural members, the two major remaining hurdles needing to be overcome before natural fiber composites can be adopted as housing materials are the cost and sustainability of the resin system and the moisture resistance/durability of the fibers. (Abstract shortened by UMI.)

Effect of tooth brush abrasion and thermo-mechanical loading on direct and indirect veneer restorations.

PubMed

Rosentritt, Martin; Sawaljanow, Alexander; Behr, Michael; Kolbeck, Carola; Preis, Verena

2015-01-01

This study investigated toothbrush abrasion and in vitro aging on ceramic (indirect technique) and composite veneers (direct technique). Identical composite and individual human incisors were restored with industrially preformed composite veneers, indirectly produced ceramic veneers, and direct composite restorations. Surface roughness was determined before and after tooth brushing. A 5-year period of oral service was simulated by thermal cycling and mechanical loading (TCML). After TCML, all specimens were examined with microscopy and scanning electron microscopy. Specimens without failures during TCML were loaded until failure. analysis of variance; Bonferroni's post hoc analysis, Kaplan-Meier-Log Rank test (α = 0.05). Tooth brushing yielded a non-significant increase (p = 0.560) in roughness in all materials (industrial veneer, 0.12+/-0.07 μm, direct restoration, 0.18+/-0.14 μm, ceramic, 0.35+/-0.16 μm). No significant differences in roughness could be determined between the materials, neither before nor after testing (p < 0.001). After TCML of artificial teeth, direct and preformed composite veneers on composite teeth showed no failures or damages. Two ceramic veneers showed cracking in the labial area. After TCML of human teeth, transmission microscopy indicated a facial crack in a ceramic veneer and chipping in the cervical area of a preformed veneer. Two direct composite veneers lost retention. No significantly different survival rates were found between the three veneer groups. Fracture force on human teeth varied between 527.8+/-132.4 N (ceramic), 478.3+/-165.4 N (preformed composite), and 605.0+/-263.5 N (direct composite). All materials revealed comparable wear resistance. Indirect ceramic, direct restorative composite, and preformed composite veneers showed comparable failure rates and satisfying longevity. The results indicate similar longevity of the chosen materials for veneer restorations.

49 CFR 178.810 - Drop test.

Code of Federal Regulations, 2010 CFR

2010-10-01

... preparation for the drop test. (1) Metal, rigid plastic, and composite IBCs intended to contain solids must be.... (4) Rigid plastic IBCs and composite IBCs with plastic inner receptacles must be conditioned for... material having essentially the same physical characteristics. (3) The specific gravity and viscosity of a...

FRP/steel composite damage acoustic emission monitoring and analysis

NASA Astrophysics Data System (ADS)

Li, Dongsheng; Chen, Zhi

2015-04-01

FRP is a new material with good mechanical properties, such as high strength of extension, low density, good corrosion resistance and anti-fatigue. FRP and steel composite has gotten a wide range of applications in civil engineering because of its good performance. As the FRP/steel composite get more and more widely used, the monitor of its damage is also getting more important. To monitor this composite, acoustic emission (AE) is a good choice. In this study, we prepare four identical specimens to conduct our test. During the testing process, the AE character parameters and mechanics properties were obtained. Damaged properties of FRP/steel composite were analyzed through acoustic emission (AE) signals. By the growing trend of AE accumulated energy, the severity of the damage made on FRP/steel composite was estimated. The AE sentry function has been successfully used to study damage progression and fracture emerge release rate of composite laminates. This technique combines the cumulative AE energy with strain energy of the material rather than analyzes the AE information and mechanical separately.

Bulk metallic glass matrix composites: Processing, microstructure, and application as a kinetic energy penetrator

NASA Astrophysics Data System (ADS)

Dandliker, Richard B.

The development of alloys with high glass forming ability allows fabrication of bulk samples of amorphous metal. This capability makes these materials available for applications which require significant material thickness in all three dimensions. Superior mechanical properties and advantages in processing make metallic glass a choice candidate as a matrix material for composites. This study reports techniques for making composites by melt-infiltration casting using the alloy Zrsb{41.2}Tisb{13.8}Cusb{12.5}Nisb{10.0}Besb{22.5} (VitreloyspTM 1) as a matrix material. Composite rods 5 cm in length and 7 mm in diameter were made and found to have a nearly fully amorphous matrix; there was less than 3 volume percent crystallized matrix material. The samples were reinforced by continuous metal wires, tungsten powder, or silicon carbide particulate preforms. The most easily processed samples were made with uniaxially aligned tungsten and carbon steel continuous wire reinforcement; the majority of the analysis presented is of these samples. The measured porosity was typically less than 3%. The results also indicate necessary guidelines for developing processing techniques for large scale production, new reinforcement materials, and other metallic glass compositions. Analysis of the microstructure of the tungsten wire and steel wire reinforced composites was performed by x-ray diffraction, scanning electron microscopy, scanning Auger microscopy, transmission electron microscopy, and energy dispersive x-ray spectroscopy. The most common phase in the crystallized matrix is most likely a Laves phase with the approximate formula Besb{12}Zrsb3TiNiCu. In tungsten-reinforced composites, a crystalline reaction layer 240 nm thick of tungsten nanocrystals in an amorphous matrix formed. In the steel reinforced composites, the reaction layer was primarily composed of a mixed metal carbide, mainly ZrC. One promising application of the metallic glass matrix composite is as a kinetic energy penetrator material. Ballistic tests show that a composite of 80 volume percent uniaxially aligned tungsten wires and a VitreloyspTM 1 matrix has self-sharpening behavior, which is a necessary characteristic of superior penetrator materials. Small-scale tests with both aluminum and steel targets show that this composite performs better than tungsten heavy alloys typically used for penetrator applications, and comparably with depleted uranium.

[Evaluation of mechanical properties of four kinds of composite resins for inlay].

PubMed

Jiang, Ling-ling; Liu, Hong; Wang, Jin-rui

2011-04-01

To evaluate the compressive strength, wear resistance, hardness, and soaking fatigue of four composite resins for inlay, which were Ceramage, Surefil, Solitaire 2, and Filtek(TM) Z350. Scanning electron microscope (SEM) was used to analyze the microstructures of the wear surface of the samples. The samples for the compression test, hardness test and wear were prepared. The samples were respectively immersed in the artificial saliva for 2 months for immersed test. The electronic universal testing machine was used to test the compression strength. Hardness was quantified by micro-Vickers hardness test. The wear tester was used for the wear test. SEM was used to analyze the microstructures of the wear surface of samples. All the data was analyzed by using SPSS17.0 software package. The compressive strength of Surefil was the biggest which was significantly higher than the other three resins before soaking (P<0.05). After soaking, there was no significant difference between the composite resins (P>0.05). The hardness of Surefil was the best, and significant difference was found between the hardness of the materials before soaking (P<0.05). After soaking, no significant difference was obtained between the hardness of Surefil and Filtek(TM) Z350 (P>0.05).The compressive strength and hardness of 4 materials decreased after soaking in artificial saliva. But only the compressive strength of Filtek(TM) Z350 had no significant change after immersion (P>0.05). Except Filtek(TM) Z350, there was significant difference between the other three materials (P<0.05). Significant relationship was observed between wear and hardness of three materials (P<0.05). According to SEM observation, abrasive wear occurred in four materials. In addition to Ceramage, other composite resins had adhesive wear. The mechanical property of Surefil is the best, and it is suitable for fabrication of posterior inlay. Filtek(TM) Z350's ability to resist fatigue is the best.

Shear bond strength between an indirect composite layering material and feldspathic porcelain-coated zirconia ceramics.

PubMed

Fushiki, Ryosuke; Komine, Futoshi; Blatz, Markus B; Koizuka, Mai; Taguchi, Kohei; Matsumura, Hideo

2012-10-01

This study aims to evaluate the effect of both feldspathic porcelain coating of zirconia frameworks and priming agents on shear bond strength between an indirect composite material and zirconia frameworks. A total of 462 airborne-particle-abraded zirconia disks were divided into three groups: untreated disks (ZR-AB), airborne-particle-abraded zirconia disks coated with feldspathic porcelain, (ZR-PO-AB), and hydrofluoric acid-etched zirconia disks coated with feldspathic porcelain (ZR-PO-HF). Indirect composite (Estenia C&B) was bonded to zirconia specimens with no (CON) or one of four priming agents--Clearfil Photo Bond (CPB), Clearfil Photo Bond with Clearfil Porcelain Bond Activator (CPB + activator), Estenia Opaque primer, or Porcelain Liner M Liquid B (PLB)--with or without an opaque material (Estenia C&B Opaque). All specimens were tested for shear bond strength before and after 20,000 thermocycles. The Steel-Dwass test and Mann-Whitney U test were used to compare shear bond strength. In ZR-AB specimens, the initial bond strength of the CPB and CPB + Activator groups was significantly higher as compared with the other three groups (P < 0.05), whereas the PLB and CPB + Activator groups had the highest pre- and post-thermocycling bond strengths in ZR-PO-AB and ZR-PO-HF specimens. Among CON disks without opaque material, bond strength was significantly lower in ZR-AB specimens than in ZR-PO-AB and ZR-PO-HF specimens (P < 0.05). Feldspathic porcelain coating of a Katana zirconia framework enhanced the bond strength of Estenia C&B indirect composite to zirconia independent of surface treatment. The use of a silane coupling agent and opaque material yields durable bond strength between the indirect composite and feldspathic-porcelain-coated zirconia. The results of the present study suggest that feldspathic porcelain coating of zirconia frameworks is an effective method to obtain clinically acceptable bond strengths of a layering indirect composite material to a zirconia framework.

Lead isotopic composition of trinitite melt glass: evidence for the presence of Canadian industrial lead in the first atomic weapon test.

PubMed

Bellucci, Jeremy J; Simonetti, Antonio; Wallace, Christine; Koeman, Elizabeth C; Burns, Peter C

2013-08-06

The Pb isotopic compositions for 51 spots of melt glass in 11 samples of trinitite have been determined by laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). Trinitite glass yields a large range of Pb isotopic compositions (i.e., (206)Pb/(204)Pb = 17.08-19.04), which reflect mixing between industrial Pb from materials used in the Trinity test and natural geologic components. Areas within trinitite melt glass containing high concentrations of both Cu and Pb, which are derived from the bomb and blast site-related components, were used for delineating the Pb isotopic composition corresponding to the anthropogenic Pb component. Comparison between the isotopic composition estimated here for the industrial Pb used in the Trinity test and those from known Pb deposits worldwide indicates close agreement with ore from the Buchans mine (Newfoundland, Canada). The Buchans mine was active during the time of the Trinity test and was operated by the American Smelting and Refining Company, which could have provided the Pb used in the test. The industrial Pb used in the Trinity test materials is not documented in the literature (or declassified) but could have been present in bricks, solder, pigs, or some other anthropogenic component related to the experiment.

Thermal loading in the laser holography nondestructive testing of a composite structure

NASA Technical Reports Server (NTRS)

Liu, H. K.; Kurtz, R. L.

1975-01-01

A laser holographic interferometry method that has variable sensitivity to surface deformation was applied to the investigation of composite test samples under thermal loading. A successful attempt was made to detect debonds in a fiberglass-epoxy-ceramic plate. Experimental results are presented along with the mathematical analysis of the physical model of the thermal loading and current conduction in the composite material.

Advanced composites in sailplane structures: Application and mechanical properties

NASA Technical Reports Server (NTRS)

Muser, D.

1979-01-01

Advanced Composites in sailplanes mean the use of carbon and aramid fibers in an epoxy matrix. Weight savings were in the range of 8 to 18% in comparison with glass fiber structures. The laminates will be produced by hand-layup techniques and all material tests were done with these materials. These values may be used for calculation of strength and stiffness, as well as for comparison of the materials to get a weight-optimum construction. Proposals for material-optimum construction are mentioned.

Strength criteria for composite materials (a literature survey)

NASA Technical Reports Server (NTRS)

Roode, F.

1982-01-01

Literature concerning strength (failure) criteria for composite materials is reviewed with emphasis on phenomenological failure criteria. These criteria are primarily intended to give a good estimation of the safety margin with respect to failure for arbitrary multiaxial stress states. The failure criteria do not indicate the types of fracture that will occur in the material. The collection of failure criteria is evaluated for applicability for the glass reinforced plastics used in mine detectors. Material tests necessary to determine the parameters in the failure criteria are discussed.

Progressive Damage and Failure Analysis of Composite Laminates

NASA Astrophysics Data System (ADS)

Joseph, Ashith P. K.

Composite materials are widely used in various industries for making structural parts due to higher strength to weight ratio, better fatigue life, corrosion resistance and material property tailorability. To fully exploit the capability of composites, it is required to know the load carrying capacity of the parts made of them. Unlike metals, composites are orthotropic in nature and fails in a complex manner under various loading conditions which makes it a hard problem to analyze. Lack of reliable and efficient failure analysis tools for composites have led industries to rely more on coupon and component level testing to estimate the design space. Due to the complex failure mechanisms, composite materials require a very large number of coupon level tests to fully characterize the behavior. This makes the entire testing process very time consuming and costly. The alternative is to use virtual testing tools which can predict the complex failure mechanisms accurately. This reduces the cost only to it's associated computational expenses making significant savings. Some of the most desired features in a virtual testing tool are - (1) Accurate representation of failure mechanism: Failure progression predicted by the virtual tool must be same as those observed in experiments. A tool has to be assessed based on the mechanisms it can capture. (2) Computational efficiency: The greatest advantages of a virtual tools are the savings in time and money and hence computational efficiency is one of the most needed features. (3) Applicability to a wide range of problems: Structural parts are subjected to a variety of loading conditions including static, dynamic and fatigue conditions. A good virtual testing tool should be able to make good predictions for all these different loading conditions. The aim of this PhD thesis is to develop a computational tool which can model the progressive failure of composite laminates under different quasi-static loading conditions. The analysis tool is validated by comparing the simulations against experiments for a selected number of quasi-static loading cases.

Evaluation of Microleakage and Marginal Ridge Fracture Resistance of Primary Molars Restored with Three Restorative Materials: A Comparative in vitro Study

PubMed Central

Yeolekar, Tapan Satish; Mukunda, KS; Kiran, NK

2015-01-01

ABSTRACT Composite restorations are popular because of their superior esthetics and acceptable clinical performance. But shrinkage is still a drawback. Polymerization shrinkage results in volumetric contraction, leading to deformation of the cusps, microleakage, decrease of marginal adaptation, enamel micro-cracks and postoperative sensitivity. A new class of ring opening resin composite based on silorane chemistry has been introduced with claims of less than 1% shrinkage during polymerization. The present study was conducted to evaluate and compare the ability of low shrink silorane based material, a packable composite and a compomer to resist microleakage in class II restorations on primary molars and evaluate marginal ridge fracture resistance of these materials. Sixty human primary molars were selected. Class II cavities were prepared and the teeth were divided into three groups of twenty each. Groups were as follows group I: low shrink composite resin (Filtek P90). Group II: packable composite (Filtek P60) and Group III: compomer (Compoglass F). Half of the teeth were used for microleakage and the rest for marginal ridge fracture resistance. For microleakage testing, dye penetration method was used with 1% methylene blue dye. Followed by evaluation and grading under stereomicroscope at 10* magnification. Fracture resistance was tested with universal testing machine. It was concluded that low shrink silorane based composite resin showed the least amount of microleakage, whereas compomer showed the highest microleakage. Packable composite resisted fracture of marginal ridge better than other composite resins. Marginal ridge fracture resistance of packable composite was comparable to the intact side. How to cite this article: Yeolekar TS, Chowdhary NR, Mukunda KS, Kiran NK. Evaluation of Microleakage and Marginal Ridge Fracture Resistance of Primary Molars Restored with Three Restorative Materials: A Comparative in vitro Study. Int J Clin Pediatr Dent 2015;8(2):108-113. PMID:26379377

High-Strength Composite Fabric Tested at Structural Benchmark Test Facility

NASA Technical Reports Server (NTRS)

Krause, David L.

2002-01-01

Large sheets of ultrahigh strength fabric were put to the test at NASA Glenn Research Center's Structural Benchmark Test Facility. The material was stretched like a snare drum head until the last ounce of strength was reached, when it burst with a cacophonous release of tension. Along the way, the 3-ft square samples were also pulled, warped, tweaked, pinched, and yanked to predict the material's physical reactions to the many loads that it will experience during its proposed use. The material tested was a unique multi-ply composite fabric, reinforced with fibers that had a tensile strength eight times that of common carbon steel. The fiber plies were oriented at 0 and 90 to provide great membrane stiffness, as well as oriented at 45 to provide an unusually high resistance to shear distortion. The fabric's heritage is in astronaut space suits and other NASA programs.

Evaluation of dredged material proposed for ocean disposal from Shark River Project area

DOE Office of Scientific and Technical Information (OSTI.GOV)

Antrim, L.D.; Gardiner, W.W.; Barrows, E.S.

1996-09-01

The objective of the Shark River Project was to evaluate proposed dredged material to determine its suitability for unconfined ocean disposal at the Mud Dump Site. Tests and analyses were conducted on the Shark River sediments. The evaluation of proposed dredged material consisted of bulk sediment chemical and physical analysis, chemical analyses of dredging site water and elutriate, water-column and benthic acute toxicity tests, and bioaccumulation tests. Individual sediment core samples collected from the Shark River were analyzed for grain size, moisture content, and total organic carbon (TOC). One sediment composite was analyzed for bulk density, specific gravity, metals, chlorinatedmore » pesticides, polychlorinated biphenyl (PCB) congeners, polynuclear aromatic hydrocarbons (PAHs), and 1,4- dichlorobenzene. Dredging site water and elutriate, prepared from suspended-particulate phase (SPP) of the Shark River sediment composite, were analyzed for metals, pesticides, and PCBs. Benthic acute toxicity tests and bioaccumulation tests were performed.« less

Test and analysis of Celion 3000/PMR-15, graphite/polyimide bonded composite joints: Data report

NASA Technical Reports Server (NTRS)

Cushman, J. B.; Mccleskey, S. F.; Ward, S. H.

1982-01-01

Standard single lap, double lap and symmetric step lap bonded joints of Celion 3000/PMR-15 graphite/polyimide composite were evaluated. Composite to composite and composite to titanium joints were tested at 116 K (-250 F), 294 K (70 F) and 561 K (550 F). Joint parameters evaluated are lap length, adherend thickness, adherend axial stiffness, lamina stacking sequence and adherend tapering. Advanced joint concepts were examined to establish the change in performance of preformed adherends, scalloped adherends and hybrid systems. The material properties of the high temperature adhesive, designated A7F, used for bonding were established. The bonded joint tests resulted in interlaminar shear or peel failures of the composite and there were very few adhesive failures. Average test results agree with expected performance trends for the various test parameters. Results of finite element analyses and of test/analysis correlations are also presented.

Research on Antiphonic Characteristic of AlMg10-SiC Ultralight Composite Materials

NASA Astrophysics Data System (ADS)

Rusu, O.; Rusu, I.

2018-06-01

The paper presents the results on the absorption sound testing of an ultralight cellular composite material AlMg10-SiC, obtained by sputtering method. We have chosen this type of material because its microstructure generally comprises open cells (and relatively few semi-open cells), evenly distributed in the material, a structure that, at least theoretically, has a favorable behavior in relation to sound damping. The tests were performed on three types of samples, namely P11 – AlMg10 – 5%SiC, P12 – AlMg10 – 10%SiC şi P13 – AlMg10 – 15%SiC. The 15% SiC (P13) cellular material sample has the best sound-absorbing characteristics and the highest practical absorption degree.

Oxidation Resitant HfC-TaC Rocket Thruster for High Performance Propellants

NASA Technical Reports Server (NTRS)

Patterson, Mark

1999-01-01

The purpose of this reasearch effort was to develop high temperature, oxidation resistant thrusters which would lessen the thruster cooling requirements, resulting in increased performance and longer life for onboard propulsion systems for spacecraft. This research effort focussed on developing ceramic matrix composites (CMCs) for this application, and specifically investigated the use of HfC stabilized with TaC. This material composition can potentially operate in a stoichiometric oxygen to hydrogen ratio at a temperature of 5000 deg F (2760 deg C) in a radiatively cooled mode. Various compositions of Hafnium Carbide (HfC) and Tantalum Carbide (TaC) were deposited by chemical vapor deposition (CVD) and tested, in an attempt to identify the composition which offered the best oxidation resistance. Although it was identified that small amounts of TaC appeared to offer improved oxidation resistance over HfC alone, an optimal composition was not identified. A 251bf thruster was fabricated from a novel CMC sandwich construction with a HfC-TaC matrix, and survived two test firings, each of 5 seconds before a failure in the injector caused the run to be aborted. It was not possible to control the relative stoichiometry of the HfC and TaC composition throughout the reactor due to the large difference in the thermodynamics of the HfC and TaC formation from their respective chlorides. This also resulted in an inability to infiltrate TaC into the preform under the experimental conditions investigated. Other material compositions were fabricated and tested and two material systems; HfC-SiC functionally graded to C(sub f)/C and Re functionally graded to C(sub f)/C were selected for further testing. These functionally graded composites have use in a number of propulsion applications presently of interest to NASA and the defense industry. Their ability to withstand extremely hostile thermal environments and the light-weight and high-strength exhibited from the C(sub f)/C composite make these materials particularly suited for these applications. In the Phase III which is presently underway, Re functionally graded to C(sub f)/C is being further developed and tested for application in the thrust cells for the Linear Aerospike Engine for the X33 and RLV.

Cryogenic Fluid Management Experiment (CFME) trunnion verification testing

NASA Technical Reports Server (NTRS)

Bailey, W. J.; Fester, D. A.

1983-01-01

The Cryogenic Fluid Management Experiment (CFME) was designed to characterize subcritical liquid hydrogen storage and expulsion in the low-g space environment. The CFME has now become the storage and supply tank for the Cryogenic Fluid Management Facility, which includes transfer line and receiver tanks, as well. The liquid hydrogen storage and supply vessel is supported within a vacuum jacket to two fiberglass/epoxy composite trunnions which were analyzed and designed. Analysis using the limited available data indicated the trunnion was the most fatigue critical component in the storage vessel. Before committing the complete storage tank assembly to environmental testing, an experimental assessment was performed to verify the capability of the trunnion design to withstand expected vibration and loading conditions. Three tasks were conducted to evaluate trunnion integrity. The first determined the fatigue properties of the trunnion composite laminate materials. Tests at both ambient and liquid hydrogen temperatures showed composite material fatigue properties far in excess of those expected. Next, an assessment of the adequacy of the trunnion designs was performed (based on the tested material properties).

Evaluation of Braided Stiffener Concepts for Transport Aircraft Wing Structure Applications

NASA Technical Reports Server (NTRS)

Deaton, Jerry W.; Dexter, H. Benson (Editor); Markus, Alan; Rohwer, Kim

1995-01-01

Braided composite materials have potential for application in aircraft structures. Stiffeners, wing spars, floor beams, and fuselage frames are examples where braided composites could find application if cost effective processing and damage requirements are met. Braiding is an automated process for obtaining near-net shape preforms for fabrication of components for structural applications. Previous test results on braided composite materials obtained at NASA Langley indicate that damage tolerance requirements can be met for some applications. In addition, the braiding industry is taking steps to increase the material through-put to be more competitive with other preform fabrication processes. Data are presented on the compressive behavior of three braided stiffener preform fabric constructions as determined from individual stiffener crippling test and three stiffener wide panel tests. Stiffener and panel fabrication are described and compression data presented for specimens tested with and without impact damage. In addition, data are also presented on the compressive behavior of the stitched stiffener preform construction currently being used by McDonnell Douglas Aerospace in the NASA ACT wing development program.