These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

COMPLEX IDENTIFICATION OF THERMOPHYSICAL PROPERTIES OF ANISOTROPIC COMPOSITE MATERIAL  

Microsoft Academic Search

The statement and solution algorithm of a two-dimensional thermal conductivity inverse problem on complex identification of thermophysical properties of anisotropic complex material is presented. An experimental facility for carrying out thermophysical research has been worked out. The problem of optimal designing of temperature measurements has been solved in the course of the experiment. Data on the complex of thermophysical properties

O. M. ALIFANOV; Y. JARNY

2

Digital Image Correlation and biaxial test on composite material for anisotropic damage law identification  

E-print Network

materials usually exhibit complex, namely, anisotropic and non linear behaviors. Ceramic Matrix Composites (CMCs) in particular be- have in very distinct ways depending on the loading direction wrt. the fiber prin- cipal strain. Conversely, fiber breakage and interface debonding are related to the fiber

Paris-Sud XI, Université de

3

Guided waves propagating in sandwich structures made of anisotropic, viscoelastic, composite materials.  

PubMed

The propagation of Lamb-like waves in sandwich plates made of anisotropic and viscoelastic material layers is studied. A semi-analytical model is described and used for predicting the dispersion curves (phase velocity, energy velocity, and complex wave-number) and the through-thickness distribution fields (displacement, stress, and energy flow). Guided modes propagating along a test-sandwich plate are shown to be quite different than classical Lamb modes, because this structure does not have the mirror symmetry, contrary to most of composite material plates. Moreover, the viscoelastic material properties imply complex roots of the dispersion equation to be found that lead to connections between some of the dispersion curves, meaning that some of the modes get coupled together. Gradual variation from zero to nominal values of the imaginary parts of the viscoelastic moduli shows that the mode coupling depends on the level of material viscoelasticity, except for one particular case where this phenomenon exists whether the medium is viscoelastic or not. The model is used to quantify the sensitivity of both the dispersion curves and the through-thickness mode shapes to the level of material viscoelasticity, and to physically explain the mode-coupling phenomenon. Finite element software is also used to confirm results obtained for the purely elastic structure. Finally, experiments are made using ultrasonic, air-coupled transducers for generating and detecting guided modes in the test-sandwich structure. The mode-coupling phenomenon is then confirmed, and the potential of the air-coupled system for developing single-sided, contactless, NDT applications of such structures is discussed. PMID:12765380

Castaings, Michel; Hosten, Bernard

2003-05-01

4

A coupled anisotropic damage model for the inelastic response of composite materials  

Microsoft Academic Search

A coupled incremental damage and plasticity theory for rate-independent and rate-dependent composite materials is introduced here. This allows damage to be path-dependent either on the stress history or thermodynamic force conjugate to damage. This is achieved through the use of an incremental damage tensor. Damage and inelastic deformations are incorporated in the proposed model that is used for the analysis

George Z. Voyiadjis; Babur Deliktas

2000-01-01

5

Unit-Sphere Multiaxial Stochastic-Strength Model Applied to Anisotropic and Composite Materials  

NASA Technical Reports Server (NTRS)

Models that predict the failure probability of brittle materials under multiaxial loading have been developed by authors such as Batdorf, Evans, and Matsuo. These "unit-sphere" models assume that the strength-controlling flaws are randomly oriented, noninteracting planar microcracks of specified geometry but of variable size. This methodology has been extended to predict the multiaxial strength response of transversely isotropic brittle materials, including polymer matrix composites (PMCs), by considering (1) flaw-orientation anisotropy, whereby a preexisting microcrack has a higher likelihood of being oriented in one direction over another direction, and (2) critical strength, or K (sub Ic) orientation anisotropy, whereby the level of critical strength or fracture toughness for mode I crack propagation, K (sub Ic), changes with regard to the orientation of the microstructure. In this report, results from finite element analysis of a fiber-reinforced-matrix unit cell were used with the unit-sphere model to predict the biaxial strength response of a unidirectional PMC previously reported from the World-Wide Failure Exercise. Results for nuclear-grade graphite materials under biaxial loading are also shown for comparison. This effort was successful in predicting the multiaxial strength response for the chosen problems. Findings regarding stress-state interactions and failure modes also are provided.

Nemeth, Noel, N.

2013-01-01

6

Enhancement of non-resonant dielectric cloaks using anisotropic composites  

NASA Astrophysics Data System (ADS)

Cloaking techniques conceal objects by controlling the flow of electromagnetic waves to minimize scattering. Herein, the effectiveness of homogenized anisotropic materials in non-resonant dielectric multilayer cloaking is studied. Because existing multilayer cloaking by isotropic materials can be regarded as homogenous anisotropic cloaking from a macroscopic view, anisotropic materials can be efficiently designed through optimization of their physical properties. Anisotropic properties can be realized in two-phase composites if the physical properties of the material are within appropriate bounds. The optimized anisotropic physical properties are identified by a numerical optimization technique based on a full-wave simulation using the finite element method. The cloaking performance measured by the total scattering width is improved by about 2.8% and 25% in eight- and three-layer cylindrical cloaking materials, respectively, compared with multilayer cloaking by isotropic materials. In all cloaking examples, the optimized microstructures of the two-phase composites are identified as the simple lamination of two materials, which maximizes the anisotropy. The same performance as published for eight-layer cloaking by isotropic materials is achieved by three-layer cloaking using the anisotropic material. Cloaking with an approximately 50% reduction of total scattering width is achieved even in an octagonal object. Since the cloaking effect can be realized using just a few layers of the laminated anisotropic dielectric composite, this may have an advantage in the mass production of cloaking devices.

Takezawa, Akihiro; Kitamura, Mitsuru

2014-01-01

7

Anisotropic fiber alignment in composite structures  

DOEpatents

High strength material composite structures are formed with oriented fibers to provide controlled anisotropic fibers. Fibers suspended in non-dilute concentrations (e.g., up to 20 volume percent for fibers having an aspect ratio of 20) in a selected medium are oriented by moving an axially spaced array of elements in the direction of desired fiber alignment. The array elements are generally perpendicular to the desired orientation. The suspension medium may also include sphere-like particles where the resulting material is a ceramic.

Graham, Alan L. (Los Alamos, NM); Mondy, Lisa A. (Cedar Crest, NM); Guell, David C. (Los Alamos, NM)

1993-01-01

8

Anisotropic fiber alignment in composite structures  

DOEpatents

High strength material composite structures are formed with oriented fibers to provide controlled anisotropic fibers. Fibers suspended in non-dilute concentrations (e.g., up to 20 volume percent for fibers having an aspect ratio of 20) in a selected medium are oriented by moving an axially spaced array of elements in the direction of desired fiber alignment. The array elements are generally perpendicular to the desired orientation. The suspension medium may also include sphere-like particles where the resulting material is a ceramic. 5 figures.

Graham, A.L.; Mondy, L.A.; Guell, D.C.

1993-11-16

9

Cryogenic microwave anisotropic artificial materials  

NASA Astrophysics Data System (ADS)

This thesis addresses analysis and design of a cryogenic microwave anisotropic wave guiding structure that isolates an antenna from external incident fields from specific directions. The focus of this research is to design and optimize the radome's constituent material parameters for maximizing the isolation between an interior receiver antenna and an exterior transmitter without significantly disturbing the transmitter antenna far field characteristics. The design, characterization, and optimization of high-temperature superconducting metamaterials constitutive parameters are developed in this work at X-band frequencies. A calibrated characterization method for testing arrays of split-ring resonators at cryogenic temperature inside a TE10 waveguide was developed and used to back-out anisotropic equivalent material parameters. The artificial material elements (YBCO split-ring resonators on MgO substrate) are optimized to improve the narrowband performance of the metamaterial radome with respect to maximizing isolation and minimizing shadowing, defined as a reduction of the transmitted power external to the radome. The optimized radome is fabricated and characterized in a parallel plate waveguide in a cryogenic environment to demonstrate the degree of isolation and shadowing resulting from its presence. At 11.12 GHz, measurements show that the HTS metamaterial radome achieved an isolation of 10.5 dB and the external power at 100 mm behind the radome is reduced by 1.9 dB. This work demonstrates the feasibility of fabricating a structure that provides good isolation between two antennas and low disturbance of the transmitter's fields.

Trang, Frank

10

Elastic properties of spherically anisotropic piezoelectric composites  

NASA Astrophysics Data System (ADS)

Effective elastic properties of spherically anisotropic piezoelectric composites, whose spherically anisotropic piezoelectric inclusions are embedded in an infinite non-piezoelectric matrix, are theoretically investigated. Analytical solutions for the elastic displacements and the electric potentials under a uniform external strain are derived exactly. Taking into account of the coupling effects of elasticity, permittivity and piezoelectricity, the formula is derived for estimating the effective elastic properties based on the average field theory in the dilute limit. An elastic response mechanism is revealed, in which the effective elastic properties increase as inclusion piezoelectric properties increase and inclusion dielectric properties decrease. Moreover, a piezoelectric response mechanism, of which the effective piezoelectric response vanishes due to the symmetry of spherically anisotropic composite, is also disclosed.

Wei, En-Bo; Gu, Guo-Qing; Poon, Ying-Ming

2010-09-01

11

Composite Materials  

NASA Technical Reports Server (NTRS)

Langley Research Center researchers invented an advanced polymer, a chemical compound formed by uniting many small molecules to create a complex molecule with different chemical properties. The material is a thermoplastic polyimide that resists solvents. Other polymers of this generic type are soluble in solvents, thus cannot be used where solvents are present. High Technology Services (HTS), Inc. licensed technology and is engaged in development and manufacture of high performance plastics, resins and composite materials. Techimer Materials Division is using technology for composite matrix resins that offer heat resistance and protection from radiation, electrical and chemical degradation. Applications of new polymer include molding resins, adhesives and matrix resins for fiber reinforced composites.

1988-01-01

12

Graphical retrieval method for orthorhombic anisotropic materials.  

PubMed

We apply the equivalent theory to orthorhombic anisotropic materials and provide a general unit-cell design criterion for achieving a length-independent retrieval of the effective material parameters from a single layer of unit cells. We introduce a graphical retrieval method and phase unwrapping techniques. The graphical method utilizes the linear regression technique. Our method can reduce the uncertainty of experimental measurements and the ambiguity of phase unwrapping. Moreover, the graphical method can simultaneously determine the bulk values of the six effective material parameters, permittivity and permeability tensors, from a single layer of unit cells. PMID:20721089

Feng, Simin

2010-08-01

13

ULTRASONIC CHARACTERIZATION OF ADVANCED COMPOSITE MATERIALS  

Microsoft Academic Search

With increased use of composite materials in critical structural applications it is more important than ever to independently assure structural integrity. Complexity of the advanced composite materials including layered and bonded structures represents challenges in developing optimized ultrasonic tests. Traditional ultrasonic NDT methods are inappropriate and often misleading when applied to anisotropic and nonhomogeneous composite materials. In advanced technology applications

B. Boro Djordjevic

14

Anisotropic magnetostrictive metal-polymer composites for functional devices  

NASA Astrophysics Data System (ADS)

New metal-polymer composites based on mechanochemically synthesized magnetostrictive Fe-Ga phase particles with dimensions of up to 2 ?m dispersed and spatially oriented in a polymer matrix have been studied. The polymer matrix for spatial anisotropic stabilization of particles was represented by modified polyurethane (PU). An increase in the magnetostrictive effect was achieved by directed orientation of particles in a magnetic field applied during polymerization of the PU matrix. The spatial anisotropy of the composite has been studied by the methods of conversion Mössbauer spectroscopy with resonant X-ray detection and scanning electron microscopy. It is shown that the mechanochemical synthesis is an effective method of obtaining particles with microstress-enhanced magnetostriction. The use of these particles for the formation of a functional elastomer composite provides a material with significant magnetostrictive effect, which can be several-fold increased due to orientation of particles in an applied magnetic field. The obtained anisotropic magnetostrictive composite is a promising material for the creation of smart functional components of positioning systems, attenuators, and sensors.

Kiseleva, T. Yu.; Zholudev, S. I.; Il'inykh, I. A.; Novakova, A. A.

2013-12-01

15

Stress concentration and effective stiffness of aligned fiber reinforced composite with anisotropic constituents  

E-print Network

, the representative unit cell approach has been utilized. The micro geometry of the composite is modeled by a periodicStress concentration and effective stiffness of aligned fiber reinforced composite with anisotropic Received in revised form 18 April 2008 Available online 24 May 2008 Keywords: Fibrous composite material

Sevostianov, Igor

16

Ultrasonic assembly of anisotropic short fibre reinforced composites.  

PubMed

We report the successful manufacture of short fibre reinforced polymer composites via the process of ultrasonic assembly. An ultrasonic device is developed allowing the manufacture of thin layers of anisotropic composite material. Strands of unidirectional reinforcement are, in response to the acoustic radiation force, shown to form inside various matrix media. The technique proves suitable for both photo-initiator and temperature controlled polymerisation mechanisms. A series of glass fibre reinforced composite samples constructed in this way are subjected to tensile loading and the stress-strain response is characterised. Structural anisotropy is clearly demonstrated, together with a 43% difference in failure stress between principal directions. The average stiffnesses of samples strained along the direction of fibre reinforcement and transversely across it were 17.66±0.63MPa and 16.36±0.48MPa, respectively. PMID:24360815

Scholz, M-S; Drinkwater, B W; Trask, R S

2014-04-01

17

New, Z-direction anisotropically conductive composites  

NASA Astrophysics Data System (ADS)

This paper reports on the development of a new class of anistropically conductive materials based on magnetic alignment of conductive particles in nonconductive matrix materials such as elastomeric or adhesive polymers. These composites contain many vertically aligned but laterally isolated chains of ferromagnetic metal spheres, the ends of which protrude from the surfaces for better electrical contact. These novel composite structures exhibit Z-direction-only electrical conduction which, in combination with the compliant nature of the materials, can be exploited advantageously for a variety of electronic applications including fine-pitch, area-array, circuit interconnections, circuit-testing, heat sink interfacing, and sensor devices. The movement and alignment of magnetic particles in a viscous medium, and the stability of configurations in a magnetic field are discussed together with the properties of the composite materials as well as potential circuit and device applications.

Jin, S.; Sherwood, R. C.; Mottine, J. J.; Tiefel, T. H.; Opila, R. L.

1988-11-01

18

Composite Materials  

NASA Technical Reports Server (NTRS)

Composites are lighter and stronger than metals. Aramid fibers like Kevlar and Nomex were developed by DuPont Corporation and can be combined in a honeycomb structure which can give an airplane a light, tough structure. Composites can be molded into many aerodynamic shapes eliminating rivets and fasteners. Langley Research Center has tested composites for both aerospace and non-aerospace applications. They are also used in boat hulls, military shelters, etc.

1985-01-01

19

A rate dependent anisotropic damage model for metal matrix composites at elevated temperatures  

Microsoft Academic Search

A rate dependent plastic and anisotropic damage model is developed for a metal matrix composite (MMC) system at elevated temperatures. The developed constitutive model will enable one to predict the inelastic response of the composite material at different loading rates at elevated temperatures. The formulation is thermodynamically based using the concept of internal state variables. Two sets of internal variables

Babur Deliktas

1999-01-01

20

Aeroelastic tailoring of composite materials  

E-print Network

LIST OF FIGURES IiiTRODUCTI ON ST!!UCTURAL RESPONSE Deformation of Uniformly Stressed Isotropic and Anisotropic Plates Characterization of Composite Laminates . Effect of Material Parameters APPLICATIONS Aircraft Propellers Ship Propell rs... com- pliances with laminate rotation 39 15 Variation of (A) extensional ard (8) bending compliances with 0' ply rotation . . . . . . . . . . . . . . . . 40 16 Incremental aerodynamic forces on a typical blade element 43 17 Propeller velocity...

Rogers, Jesse Byron

2012-06-07

21

Brewster's angle for anisotropic material from the extinction theorem  

E-print Network

By the extinction theorem we explore the Brewster effect in the external and internal reflections of electromagnetic wave associated with an anisotropic material that is both dielectric and magnetic, including metamaterials. We obtain Fresnel's coefficients and the condition of Brewster's angle, and give microscopic explanations from the view point of molecular optics. The Brewster angle is the incidence of angle at which the contribution of all electric and magnetic dipoles in the anisotropic material to the reflection field becomes zero. Distinct from isotropic media, the anisotropic material can exhibit Brewster angle for both TE and TM waves due to the anisotropy of the material.

Weixing Shu; Zhongzhou Ren; Hailu Luo; Fei Li

2006-06-06

22

The Features of Self-Assembling Organic Bilayers Important to the Formation of Anisotropic Inorganic Materials in Microgravity Conditions  

NASA Technical Reports Server (NTRS)

There is a growing need for inorganic anisotropic particles in a variety of materials science applications. Structural, optical, and electrical properties can be greatly augmented by the fabrication of composite materials with anisotropic microstructures or with anisotropic particles uniformly dispersed in an isotropic matrix. Examples include structural composites, magnetic and optical recording media, photographic film, certain metal and ceramic alloys, and display technologies including flat panel displays. While considerable progress has been made toward developing an understanding of the synthesis of powders composed of monodispersed, spherical particles, these efforts have not been transferred to the synthesis of anisotropic nanoparticles. The major objective of the program is to develop a fundamental understanding of the growth of anisotropic particles at organic templates, with emphasis on the chemical and structural aspects of layered organic assemblies that contribute to the formation of anisotropic inorganic particles.

Talham, Daniel R.; Adair, James H.

1999-01-01

23

Composite Materials Handbook  

NSDL National Science Digital Library

From the US Army Research Laboratory, Materials Sciences Corporation, and University of Delaware Center for Composite Materials, the Composite Materials Handbook provides the "information and guidance necessary to design and fabricate end items from composite materials." Along with current information on the material properties of these composite materials, the handbook also includes data development and usage guidelines. The information has been divided into three areas: polymer, metal, and ceramic matrix composites. The Polymer Matrix Composites Handbook (three volumes including Guidelines for Characterization of Structural Materials; Material Properties; and Materials Usage, Design, and Analysis) and the Metal Matrix Composites Handbook (one volume, .pdf) are available here. The Ceramic Matrix Composites Handbook has yet to be completed. Users may also download Quick Composites Data in spreadsheet format.

24

The features of self-assembling organic bilayers important to the formation of anisotropic inorganic materials in microgravity conditions  

NASA Technical Reports Server (NTRS)

Materials with directional properties are opening new horizons in a variety of applications including chemistry, electronics, and optics. Structural, optical, and electrical properties can be greatly augmented by the fabrication of composite materials with anisotropic microstructures or with anisotropic particles uniformly dispersed in an isotropic matrix. Examples include structural composites, magnetic and optical recording media, photographic film, certain metal and ceramic alloys, and display technologies including flat panel displays. The new applications and the need for model particles in scientific investigations are rapidly out-distancing the ability to synthesize anisotropic particles with specific chemistries and narrowly distributed physical characteristics (e.g. size distribution, shape, and aspect ratio).

Talham, Daniel R.; Adair, James H.

2005-01-01

25

Composite structural materials  

NASA Technical Reports Server (NTRS)

Various topics relating to composite structural materials for use in aircraft structures are discussed. The mechanical properties of high performance carbon fibers, carbon fiber-epoxy interface bonds, composite fractures, residual stress in high modulus and high strength carbon fibers, fatigue in composite materials, and the mechanical properties of polymeric matrix composite laminates are among the topics discussed.

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

1985-01-01

26

Group velocity of cylindrical guided waves in anisotropic laminate composites.  

PubMed

An explicit expression for the group velocity of wave packets, propagating in a laminate anisotropic composite plate in prescribed directions, is proposed. It is based on the cylindrical guided wave asymptotics derived from the path integral representation for wave fields generated in the composites by given localized sources. The expression derived is theoretically confirmed by the comparison with a known representation for the group velocity vector of a plane guided wave. Then it is experimentally validated against laser vibrometer measurements of guided wave packets generated by a piezoelectric wafer active sensor in a composite plate. PMID:24437754

Glushkov, Evgeny; Glushkova, Natalia; Eremin, Artem; Lammering, Rolf

2014-01-01

27

High field dielectric properties of anisotropic polymer-ceramic composites  

SciTech Connect

Using dielectrophoretic assembly, we create anisotropic composites of BaTiO{sub 3} particles in a silicone elastomer thermoset polymer. We study a variety of electrical properties in these composites, i.e., permittivity, dielectric breakdown, and energy density as function of ceramic volume fraction and connectivity. The recoverable energy density of these electric-field-structured composites is found to be highly dependent on the anisotropy present in the system. Our results indicate that x-y-aligned composites exhibit higher breakdown strengths along with large recoverable energy densities when compared to 0-3 composites. This demonstrates that engineered anisotropy can be employed to control dielectric breakdown strengths and nonlinear conduction at high fields in heterogeneous systems. Consequently, manipulation of anisotropy in high-field dielectric properties can be exploited for the development of high energy density polymer-ceramic systems.

Tomer, V.; Randall, C. A. [Center of Dielectric Studies, Materials Research Institute, Materials Research Laboratory Bldg., Pennsylvania State University, Pennsylvania 16802I (United States)

2008-10-01

28

A General Theory of Strength for Anisotropic Materials  

Microsoft Academic Search

An operationally simple strength criterion for anisotropic materials is developed from a scalar function of two strength tensors. Differing from existing quadratic approximations of failure surfaces, the present theory satisfies the invariant requirements of coordinate transforma tion, treats interaction terms as independent components, takes into account the difference in strengths due to positive and negative stresses, and can be specialized

Stephen W. Tsai; Edward M. Wu

1971-01-01

29

Tough Composite Materials  

NASA Technical Reports Server (NTRS)

Papers and working group summaries are presented which address composite material behavior and performance improvement. Topic areas include composite fracture toughness and impact characterization, constituent properties and interrelationships, and matrix synthesis and characterization.

Vosteen, L. F. (compiler); Johnson, N. J. (compiler); Teichman, L. A. (compiler)

1984-01-01

30

Composite structural materials  

NASA Technical Reports Server (NTRS)

Technology utilization of fiber reinforced composite materials is discussed in the areas of physical properties, and life prediction. Programs related to the Composite Aircraft Program are described in detail.

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

1979-01-01

31

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

32

Anisotropic poly(ethylene glycol)/polycaprolactone hydrogel-fiber composites for heart valve tissue engineering.  

PubMed

The recapitulation of the material properties and structure of the native aortic valve leaflet, specifically its anisotropy and laminate structure, is a major design goal for scaffolds for heart valve tissue engineering. Poly(ethylene glycol) (PEG) hydrogels are attractive scaffolds for this purpose as they are biocompatible, can be modified for their mechanical and biofunctional properties, and can be laminated. This study investigated augmenting PEG hydrogels with polycaprolactone (PCL) as an analog to the fibrosa to improve strength and introduce anisotropic mechanical behavior. However, due to its hydrophobicity, PCL must be modified prior to embedding within PEG hydrogels. In this study, PCL was electrospun (ePCL) and modified in three different ways, by protein adsorption (pPCL), alkali digestion (hPCL), and acrylation (aPCL). Modified PCL of all types maintained the anisotropic elastic moduli and yield strain of unmodified anisotropic ePCL. Composites of PEG and PCL (PPCs) maintained anisotropic elastic moduli, but aPCL and pPCL had isotropic yield strains. Overall, PPCs of all modifications had elastic moduli of 3.79±0.90?MPa and 0.46±0.21?MPa in the parallel and perpendicular directions, respectively. Valvular interstitial cells seeded atop anisotropic aPCL displayed an actin distribution aligned in the direction of the underlying fibers. The resulting scaffold combines the biocompatibility and tunable fabrication of PEG with the strength and anisotropy of ePCL to form a foundation for future engineered valve scaffolds. PMID:24712446

Tseng, Hubert; Puperi, Daniel S; Kim, Eric J; Ayoub, Salma; Shah, Jay V; Cuchiara, Maude L; West, Jennifer L; Grande-Allen, K Jane

2014-10-01

33

On free vibrations of a composite material circular cylindrical shells  

NASA Astrophysics Data System (ADS)

The natural vibrations of a thin walled circular cylindrical shell composed of specially orthotropic composite materials are studied in detail. The work of Koga (1988) for isotropic shells is extended to shells of composite materials. The results are easy to use solutions for the natural frequencies for the composite shell expressed in terms of the natural frequencies for beams with the same boundary conditions at the ends, modified to include the effects of the shell geometry and the anisotropic composite material properties.

Fisher, Christopher A.; Vinson, Jack R.

1993-04-01

34

Composite structural materials  

NASA Technical Reports Server (NTRS)

The purpose of the RPI composites program is to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, reliability and life prediction. Concommitant goals are to educate engineers to design and use composite materials as normal or conventional materials. A multifaceted program was instituted to achieve these objectives.

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

1978-01-01

35

The isotropic material closest to a given anisotropic material  

Microsoft Academic Search

The isotropic elastic moduli closest to a given anisotropic elasticity tensor\\u000aare defined using three definitions of elastic distance, the standard Frobenius\\u000a(Euclidean) norm, the Riemannian distance for tensors, and the log-Euclidean\\u000anorm. The closest moduli are unique for the Riemannian and the log-Euclidean\\u000anorms, independent of whether the difference in stiffness or compliance is\\u000aconsidered. Explicit expressions for the

Andrew N. Norris

2006-01-01

36

Compliance calibration for fracture testing of anisotropic biological materials.  

PubMed

The compliance technique has been used to monitor crack length during fracture and fatigue testing of materials. Difficulties arise when this technique is applied to anisotropic biological materials such as bone. In this tutorial, two different methods of analyzing compliance calibration data are described: the standard ASTM method and a new approach developed by the authors specifically for anisotropic materials. An example is given showing how data from equine cortical bone can be analyzed. In this example, calibration tests were conducted on thirty-six three point bend specimens machined from the mid-diaphysis of six pairs of equine third metacarpal bones. Cracks were propagated in three orientations with respect to the long axis of the bone: transverse, longitudinal, and radial. Specimen compliance was determined for a crack range of 0.30 to 0.65 times the specimen width from load vs. crack opening displacement data. The results demonstrate that the ASTM method is not applicable to anisotropic biomaterials such as bone. Rather, it is necessary to develop separate compliance calibration equations for each crack propagation orientation investigated. PMID:19627864

Creel, J A; Stover, S M; Martin, R B; Fyhrie, D P; Hazelwood, S J; Gibeling, J C

2009-10-01

37

Electrically conductive composite material  

DOEpatents

An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistant pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like.

Clough, Roger L. (Albuquerque, NM); Sylwester, Alan P. (Albuquerque, NM)

1989-01-01

38

Composite Structural Materials  

NASA Technical Reports Server (NTRS)

The development and application of filamentary composite materials, is considered. Such interest is based on the possibility of using relatively brittle materials with high modulus, high strength, but low density in composites with good durability and high tolerance to damage. Fiber reinforced composite materials of this kind offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been made since the initial developments in the mid 1960's. There were only limited applied to the primary structure of operational vehicles, mainly as aircrafts.

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

1984-01-01

39

Electrically conductive composite material  

DOEpatents

An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

Clough, R.L.; Sylwester, A.P.

1989-05-23

40

Electrically conductive composite material  

DOEpatents

An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

Clough, R.L.; Sylwester, A.P.

1988-06-20

41

Composite structural materials  

NASA Technical Reports Server (NTRS)

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.

Loewy, R.; Wiberley, S. E.

1986-01-01

42

Analytical Procedure for Measuring Electrical Resistivity of Anisotropic Materials  

NASA Astrophysics Data System (ADS)

The Montgomery method is used to determine the resistivity tensor of anisotropic materials [1] such as high-TC and FeAs superconductors, 2-layer Mn oxides, organic conductors, and quasi-1D conductors. It uses the Wasscher transformation [2], which calculates an isotropic equivalent sample of the anisotropic sample. This is a timing-consuming task because it is a numerical method based upon graphical analyses obtained from calculations by Logan, Rice, and Wick [3]. In this work we report a simplification of the Montgomery method. Analytical equations are derived and applied to several isotropic and anisotropic samples (Cu, Al, Bi2Sr2CaCu2O8+?, Graphite, SrNbOx, ?-Mo4O11). Comparisons with results obtained by using the standard four-probe method demonstrate the quality and simplicity of the procedure, which can easily be extended to data acquisition systems. This material is based upon work supported by FAPESP (grant No. 07-04572-8), NSF (grants Nos. DMR-0504769 and 0552458), and CNPq (grant Nos. 301334/2007-2 and 201439/2007-7). [1] H. C. Montgomery, J. Appl. Phys. 42, 2971 (1971). [2] J. D. Wasscher, Philips Res. Repts. 16, 301 (1961). [3] B. F. Logan, S. O. Rice, and R. F. Wick, J. Appl. Phys. 42, 2975 (1971).

Dos Santos, C. A. M.; de Lima, B. S.; Shigue, C. Y.; de Campos, A.; da Luz, M. S.; Rice, A. T.; White, B. D.; Neumeier, J. J.

2009-03-01

43

Composite Material Switches  

NASA Technical Reports Server (NTRS)

A device to protect electronic circuitry from high voltage transients is constructed from a relatively thin piece of conductive composite sandwiched between two conductors so that conduction is through the thickness of the composite piece. The device is based on the discovery that conduction through conductive composite materials in this configuration switches to a high resistance mode when exposed to voltages above a threshold voltage.

Javadi, Hamid (Inventor)

2001-01-01

44

Composite Material Switches  

NASA Technical Reports Server (NTRS)

A device to protect electronic circuitry from high voltage transients is constructed from a relatively thin piece of conductive composite sandwiched between two conductors so that conduction is through the thickness of the composite piece. The device is based on the discovery that conduction through conductive composite materials in this configuration switches to a high resistance mode when exposed to voltages above a threshold voltage.

Javadi, Hamid (Inventor)

2002-01-01

45

Mechanics of Composite Materials  

Microsoft Academic Search

The mechanical behavior of composites is traditionally evaluated on both microscopic and macroscopic scale to take into account inhomogeneity. Micromechanics attempts to quantify the interactions of fiber and matrix (reinforcement and resin) on a microscopic scale on par with the diameter of a single fiber. Macromechanics treats composites as homogeneous materials, with mechanical properties representative of the laminate as a

Robert M. Jones

1999-01-01

46

Rectangular waveguide material characterization: anisotropic property extraction and measurement validation  

NASA Astrophysics Data System (ADS)

Rectangular waveguide methods are appealing for measuring isotropic and anisotropic materials because of high signal strength due to field confinement, and the ability to control the polarization of the applied electric field. As a stepping stone to developing methods for characterizing materials with fully-populated anisotropic tensor characteristics, techniques are presented in this dissertation to characterize isotropic, biaxially anisotropic, and gyromagnetic materials. Two characterization techniques are investigated for each material, and thus six different techniques are described. Additionally, a waveguide standard is introduced which may be used to validate the measurement of the permittivity and permeability of materials at microwave frequencies. The first characterization method examined is the Nicolson-Ross-Weir (NRW) technique for the extraction of isotropic parameters of a sample completely filling the cross-section of a rectangular waveguide. A second technique is proposed for the characterization of an isotropic conductor-backed sample filling the cross-section of a waveguide. If the sample is conductor-backed, and occupies the entire cross-section, a transmission measurement is not available, and thus a method must be found for providing two sufficiently different reflection measurements.The technique proposed here is to place a waveguide iris in front of the sample, exposing the sample to a spectrum of evanescent modes. By measuring the reflection coefficient with and without an iris, the necessary two data may be obtained to determine the material parameters. A mode-matching approach is used to determine the theoretical response of a sample placed behind the waveguide iris. This response is used in a root-searching algorithm to determine permittivity and permeability by comparing to measurements of the reflection coefficient. For the characterization of biaxially anisotropic materials, the first method considers an extension of the NRW technique for characterization of a sample filling the cross-section of a waveguide. Due to the rectangular nature of the waveguide, typically three different samples are manufactured from the same material in order to characterize the six complex material parameters. The second technique for measuring the electromagnetic properties of a biaxially anisotropic material sample uses a reduced-aperture waveguide sample holder designed to accommodate a cubical sample. All the tensor material parameters can then be determined by measuring the reflection and transmission coefficients of a single sample placed into several orientations. The parameters are obtained using a root-searching algorithm by comparing theoretically computed and measured reflection and transmission coefficients. The theoretical coefficients are determined using a mode matching technique. The first technique for characterizing the electromagnetic properties of gyromagnetic materials considers requires filling the cross-section of a waveguide. The material parameters are extracted from the measured reflection and transmission coefficients. Since the cross-sectional dimensions of waveguides become prohibitively large at low frequencies, and it is at these frequencies that the gyromagnetic properties are most pronounced, sufficiently large samples may not be available. Therefore, the second technique uses a reduced-aperture sample holder that does not require the sample to fill the entire cross section of the guide. The theoretical reflection and transmission coefficients for both methods are determined using a mode matching technique. A nonlinear least squares method is employed to extract the gyromagnetic material parameters. Finally, this dissertation introduces a waveguide standard that acts as a surrogate material with both electric and magnetic properties and is useful for verifying systems designed to characterize engineered materials using the NRW technique. A genetic algorithm is used to optimize the all-metallic structure to produce a surrogate with both relative permittivity and permeability near s

Crowgey, Benjamin Reid

47

Direct Imaging of Anisotropic Material Properties using Photorefractive Laser Ultrasound  

SciTech Connect

Anisotropic properties of materials can be determined by measuring the propagation of elastic waves in different directions. A laser imaging approach is presented that utilizes the adaptive property of photorefractive materials to produce a real-time measurement of the antisymmetric Lamb or flexural traveling wave mode displacement and phase. Continuous excitation is employed and the data is recorded and displayed in all directions simultaneously at video camera frame rates. Fourier transform of the data produces an image of the wave slowness in all planar directions. The results demonstrate imaging of microstructural isotropy and anisotropy and stress induced ansiotropy in plates.

K.L. Telschow; R.S. Schley; S.M. Watson; V.A. Deason

1999-06-01

48

Direct Imaging of Anisotropic Material Properties using Photorefractive Laser Ultrasound  

SciTech Connect

Anisotropic properties of materials can be determined by measuring the propagation of elastic waves in different directions. A laser imaging approach is presented that utilizes the adaptive property of photorefractive materials to produce a real-time measurement of the antisymmetric Lamb or flexural traveling wave mode displacement and phase. Continuous excitation is employed and the data is recorded and displayed in all directions simultaneously at video camera frame rates. Fourier transform of the data produces an image of the wave slowness in all planar directions. The results demonstrate imaging of microstructural isotropy and anisotropy and stress induced ansiotropy in plates.

Telschow, Kenneth Louis; Deason, Vance Albert; Schley, Robert Scott; Watson, Scott Marshall

1999-07-01

49

Understanding anisotropic plasma etching of two-dimensional polystyrene opals for advanced materials fabrication.  

PubMed

Anisotropic deformation of polystyrene particles in an oxygenated (O2/Ar) plasma is observed for radio frequency (rf) plasma and inductively coupled plasma (ICP). A facile model based on a ratio of completely isotropic and completely anisotropic etching is presented to describe the anisotropy of the etching process and is implemented to determine the height of the spheroid-shaped polystyrene particles. In our systems, we find the plasma etching to be 54% isotropic in the rf plasma and 79% isotropic in the ICP. With this model, the maximum material deposition thickness for nanofabrication with plasma-etched nanosphere lithography or colloid lithography can be predicted. Moreover, the etching of polystyrene particles in an oxygenated plasma is investigated versus the etching time, gas flow, gas composition, temperature, substrate material, and particle size. The results of this study allow precise shape tuning during the fabrication of nanostructured surfaces with size-dependent properties for bionic, medical, and photonic applications. PMID:24580644

Akinoglu, Eser M; Morfa, Anthony J; Giersig, Michael

2014-10-21

50

Nondestructive evaluation of residual stress in anisotropic materials  

SciTech Connect

The specific focus on anisotropic materials in the research was addressed in a manner which was primarily analytical. All of the experiments involving materials with substantial elastic or plastic anisotropy indicated that the materials in question exhibited a level of acoustoelastic response which was at or below the limit for useful stress evaluation. Nevertheless, the analysis performed indicates that if an experimental system is built which allows determination of the velocity variation roughly an order of magnitude more precisely than is possible with the system used in this work, the complete state of residual stress may be obtained, despite the presence of anisotropy. This report consists of a detailed description of the technique and experimental system proposed for the evaluation of residual stress states. The underlying analytical developments are reviewed, and a numerical investigation into the application of this approach for anisotropic materials is presented. It is shown that an accurate assessment of the complete residual stress state may be obtained even in cases of extreme anisotropy. Finally, an experimental investigation of the technique is presented in which the experimentally determined stress state is compared with that predicted numerically. It is shown that the two estimates of stress agree well for the material involved. 12 refs., 5 figs., 1 tab.

Johnson, G.C. (California Univ., Berkeley, CA (USA). Dept. of Mechanical Engineering)

1990-05-01

51

Higher-order compositional modeling with Fickian diffusion in unstructured and anisotropic media  

E-print Network

Higher-order compositional modeling with Fickian diffusion in unstructured and anisotropic media April 2010 Available online 12 May 2010 Keywords: Mixed hybrid finite element Discontinuous Galerkin Compositional modeling Porous media Heterogeneous media Slope limiter Fickian diffusion Unstructured grids We

Firoozabadi, Abbas

52

Exact Solution for Functionally Graded Anisotropic Elastic Composite Laminates  

E-print Network

of multilayered functionally graded materials with their properties varying exponentially in the thickness direction. The present solution extends Pagano's solution to the functionally graded material, and can serve be useful in the design of functionally graded composite laminates. KEY WORDS: functionally graded material

Pan, Ernie

53

FEM Computation of Magnetic Fields in Anisotropic Magnetic Materials  

NASA Astrophysics Data System (ADS)

The magnetic fields in nonlinear anisotropic magnetic materials were analyzed by using the Finite Element Method (FEM). The measured data was directly used in the computation without a complicateded smoothing. The resultant asymmetric linear equations were solved by using the ILUBiCGStab method without symmetrization or the ICCG method with symmetrization. The magnetic flux distributions in a ring core model showed the characteristic patterns according to the non-oriented, grain-oriented and doubly-oriented magnetic properties. The good convergence of the Newton-Raphson nonlinear iteration was attained by the iterative solvers without special techniques for the smoothing.

Kameari, Akihisa; Fujiwara, Koji

54

Composite structural materials  

NASA Technical Reports Server (NTRS)

Progress and plans are reported for investigations of: (1) the mechanical properties of high performance carbon fibers; (2) fatigue in composite materials; (3) moisture and temperature effects on the mechanical properties of graphite-epoxy laminates; (4) the theory of inhomogeneous swelling in epoxy resin; (5) numerical studies of the micromechanics of composite fracture; (6) free edge failures of composite laminates; (7) analysis of unbalanced laminates; (8) compact lug design; (9) quantification of Saint-Venant's principles for a general prismatic member; (10) variation of resin properties through the thickness of cured samples; and (11) the wing fuselage ensemble of the RP-1 and RP-2 sailplanes.

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

1983-01-01

55

An In-Depth Tutorial on Constitutive Equations for Elastic Anisotropic Materials  

NASA Technical Reports Server (NTRS)

An in-depth tutorial on the constitutive equations for elastic, anisotropic materials is presented. Basic concepts are introduced that are used to characterize materials, and notions about how anisotropic material deform are presented. Hooke s law and the Duhamel-Neuman law for isotropic materials are presented and discussed. Then, the most general form of Hooke s law for elastic anisotropic materials is presented and symmetry requirements are given. A similar presentation is also given for the generalized Duhamel-Neuman law for elastic, anisotropic materials that includes thermal effects. Transformation equations for stress and strains are presented and the most general form of the transformation equations for the constitutive matrices are given. Then, specialized transformation equations are presented for dextral rotations about the coordinate axes. Next, concepts of material symmetry are introduced and criteria for material symmetries are presented. Additionally, engineering constants of fully anisotropic, elastic materials are derived from first principles and the specialized to several cases of practical importance.

Nemeth, Michael P.

2011-01-01

56

A simple dynamic measurement technique for comparing thermal insulation performances of anisotropic building materials  

Microsoft Academic Search

Measuring or estimating thermal properties of anisotropic building materials can be key obtaining the optimum performance for a particular application. The intensive researches on development of new building materials have necessitated in situ thermal testing apparatuses in most research laboratories. Only few standardized techniques are available for accurate thermal testing of anisotropic materials, and they are generally expensive. In the

Bulent Yesilata; Paki Turgut

2007-01-01

57

Composite ion exchange materials  

SciTech Connect

Composite ion exchange materials can be formed by sorbing ion exchange polymers on inert, high surface area substrates. In general, the flux of ions and molecules through these composites, as measured electrochemically, increases as the ratio of the surface area of the substrate increases relative to the volume of the ion exchanger. This suggests that fields and gradients established at the interface between the ion exchanger and substrate are important in determining the transport characteristics of the composites. Here, the authors will focus on composites formed with a cation exchange polymer, Nafion, and two different types of microbeads: polystyrene microspheres and polystyrene coated magnetic microbeads. For the polystyrene microbeads, scanning electron micrographs suggest the beads cluster in a self-similar manner, independent of the bead diameter. Flux of Ru(NH3)63+ through the composites was studied as a function of bead fraction, bead radii, and fixed surface area with mixed bead sizes. Flux was well modeled by surface diffusion along a fractal interface. Magnetic composites were formed with columns of magnetic microbeads normal to the electrode surface. Flux of Ru(NH3)63+ through these composites increased exponentially with bead fraction. For electrolyses, the difference in the molar magnetic susceptibility of the products and reactants, Dcm, tends to be non-zero. For seven redox reactions, the ratio of the flux through the magnetic composites to the flux through a Nafion film increases monotonically with {vert_bar}Dcm{vert_bar}, with enhancements as large as thirty-fold. For reversible species, the electrolysis potential through the magnetic composites is 35 mV positive of that for the Nafion films.

Amarasinghe, S.; Zook, L.; Leddy, J. [Univ. of Iowa, Iowa City, IA (United States)

1994-12-31

58

Magnetic field manipulation of nanowires for anisotropic polymer composite synthesis  

NASA Astrophysics Data System (ADS)

One-dimensional magnetic nanowires (NWs) have attracted a great deal of attention recently due to their interesting physical properties and applications. This dissertation involves synthesizing magnetic NWs, manipulating NWs under the effect of external magnetic field in various suspensions, and integrating and assembling the NWs in polymer to develop anisotropic nanocomposites. Nickel NWs with high aspect ratio were fabricated in nanoporous alumina membranes by template assisted electrodeposition. Electrodeposition provides the flexibility to control the size, structure, morphology and composition of the NWs. One of the major challenges is to assemble the as-synthesized NWs for the development of polymer nanocomposites and biomedical sensors. In this project, magnetic field was used to assemble NWs by controlling their motion and position in fluids. This is a low-cost, non-contact and easy to scale-up approach. Nanowire rotation in responding to fixed and rotating uniform field in various suspensions has been investigated. Due to strong wire and field interaction, small fields are sufficient to manipulate NWs even in highly viscous fluids. Synchronous rotation of NWs with field has been successfully achieved indicating that NWs can be used as "nano-stir bars". To describe the NW rotation, quantitative model based on the competing magnetic field induced torque and resisting fluid drag torque was developed. As a demonstration of potential applications of the NWs, polymer nanocomposites have been fabricated. Polydimethylsiloxane with low elastic modulus and tensile strength was chosen as the polymer of interest. Based on the magnetic field manipulation, composites with NWs distributed in different orientations (random, longitudinal and transverse) were synthesized. To characterize the nonlinear elastic behavior of the composites, a high resolution strain measurement method using "micro-ruler" was developed. The mechanical and magnetic properties of composite samples were observed to be dependent on the concentration and orientation of the NWs. The elastic modulus and tensile strength increased with the concentration of NWs. Composites with NWs arranged in longitudinal direction to the applied load showed higher ductility and elastic modulus compared to randomly oriented samples. These composites can be used for structural reinforcement, electromagnetic interference shielding and biomedical devices.

Keshoju, Kusuma

59

Aerogel/polymer composite materials  

NASA Technical Reports Server (NTRS)

The invention provides new composite materials containing aerogels blended with thermoplastic polymer materials at a weight ratio of aerogel to thermoplastic polymer of less than 20:100. The composite materials have improved thermal insulation ability. The composite materials also have better flexibility and less brittleness at low temperatures than the parent thermoplastic polymer materials.

Williams, Martha K. (Inventor); Smith, Trent M. (Inventor); Fesmire, James E. (Inventor); Roberson, Luke B. (Inventor); Clayton, LaNetra M. (Inventor)

2010-01-01

60

Calculation of thermoelastic stresses in anisotropic composites exposed to pulses of penetrating radiation  

SciTech Connect

The thermoelastic stresses that arise in a microheterogeneous material with randomly oriented inclusions in exposure to pulsed radiation are correlated with thermal variations in the volume of radiation-heated inclusions and the matrix. The longitudinal thermoelastic pulse arising in thermal variations in the volume is described by introducing the effective Gruneisen parameter of the material, which is a function of the type of radiation and shape and concentration of inclusions in the material and varies during heat exchange between the inclusions and matrix differently heated by the radiation. A model for the description of the thermomechanical behavior of an anisotropic composite which considers the possibility of generation of both longitudinal and transverse elastic waves was investigated in the present study. 9 refs., 1 fig.

Davydov, A.A. [Khar`kov State Univ. (Russian Federation)

1992-11-01

61

Manipulating optical tamm state in one dimensional magnetophotonic crystal by anisotropic materials  

Microsoft Academic Search

Based on transfer matrix method a tunable optical tamm state is revealed in a one dimensional heterogeneous photonic crystal by using anisotropic materials with arbitrary optical axis. Such a tunable effect originates from the optical axis-dependent permittivity of the anisotropic materials, which leads to obvious changes in the dispersion relation and transmission spectrum. Our results provide a new pathway for

Gehao Lu; Jian da; Qi Mo; Pengwu Chen

2011-01-01

62

Mechanics of failure of composite materials  

NASA Technical Reports Server (NTRS)

Composite materials are both inhomogeneous and anisotropic. Both of these characteristics affect the internal stress distributions since inhomogeneity involves variations in both strength and stiffness. The fracture mechanics of nonuniform materials are considered, taking into account the effect of nonuniformity on stress distributions near the crack tip, predicted yield zones in nonuniform and uniform materials, and the fracture of a center-notched unidirectional specimen. The mechanics of failure of laminated materials is discussed. It is found that the development of damage in a laminate with increasing load and, possibly, increasing numbers of cycles of loading is peculiar to the laminate in question, i.e., the material system, the stacking sequence, and the geometry. Approaches for monitoring damage development are also described.

Reifsnider, K. L.

1978-01-01

63

Advanced composite materials and processes  

NASA Technical Reports Server (NTRS)

Composites are generally defined as two or more individual materials, which, when combined into a single material system, results in improved physical and/or mechanical properties. The freedom of choice of the starting components for composites allows the generation of materials that can be specifically tailored to meet a variety of applications. Advanced composites are described as a combination of high strength fibers and high performance polymer matrix materials. These advanced materials are required to permit future aircraft and spacecraft to perform in extended environments. Advanced composite precursor materials, processes for conversion of these materials to structures, and selected applications for composites are reviewed.

Baucom, Robert M.

1991-01-01

64

Anisotropic compositional expansion and chemical potential for amorphous lithiated silicon under stress tensor.  

PubMed

Si is a promising anode material for Li-ion batteries, since it absorbs large amounts of Li. However, insertion of Li leads to 334% of volumetric expansion, huge stresses, and fracture; it can be suppressed by utilizing nanoscale anode structures. Continuum approaches to stress relaxation in LixSi, based on plasticity theory, are unrealistic, because the yield strength of LixSi is much higher than the generated stresses. Here, we suggest that stress relaxation is due to anisotropic (tensorial) compositional straining that occurs during insertion-extraction at any deviatoric stresses. Developed theory describes known experimental and atomistic simulation data. A method to reduce stresses is predicted and confirmed by known experiments. Chemical potential has an additional contribution due to deviatoric stresses, which leads to increases in the driving force both for insertion and extraction. The results have conceptual and general character and are applicable to any material systems. PMID:23563528

Levitas, Valery I; Attariani, Hamed

2013-01-01

65

Fabrication, testing, and analysis of anisotropic carbon/glass hybrid composites: volume 1: technical report.  

SciTech Connect

Anisotropic carbon/glass hybrid composite laminates have been fabricated, tested, and analyzed. The laminates have been fabricated using vacuum-assisted resin transfer molding (VARTM). Five fiber complexes and a two-part epoxy resin system have been used in the study to fabricate panels of twenty different laminate constructions. These panels have been subjected to physical testing to measure density, fiber volume fraction, and void fraction. Coupons machined from these panels have also been subjected to mechanical testing to measure elastic properties and strength of the laminates using tensile, compressive, transverse tensile, and in-plane shear tests. Interlaminar shear strength has also been measured. Out-of-plane displacement, axial strain, transverse strain, and inplane shear strain have also been measured using photogrammetry data obtained during edgewise compression tests. The test data have been reduced to characterize the elastic properties and strength of the laminates. Constraints imposed by test fixtures might be expected to affect measurements of the moduli of anisotropic materials; classical lamination theory has been used to assess the magnitude of such effects and correct the experimental data for the same. The tensile moduli generally correlate well with experiment without correction and indicate that factors other than end constraints dominate. The results suggest that shear moduli of the anisotropic materials are affected by end constraints. Classical lamination theory has also been used to characterize the level of extension-shear coupling in the anisotropic laminates. Three factors affecting the coupling have been examined: the volume fraction of unbalanced off-axis layers, the angle of the off-axis layers, and the composition of the fibers (i.e., carbon or glass) used as the axial reinforcement. The results indicate that extension/shear coupling is maximized with the least loss in axial tensile stiffness by using carbon fibers oriented 15{sup o} from the long axis for approximately two-thirds of the laminate volume (discounting skin layers), with reinforcing carbon fibers oriented axially comprising the remaining one-third of the volume. Finite element analysis of each laminate has been performed to examine first ply failure. Three failure criteria--maximum stress, maximum strain, and Tsai-Wu--have been compared. Failure predicted by all three criteria proves generally conservative, with the stress-based criteria the most conservative. For laminates that respond nonlinearly to loading, large error is observed in the prediction of failure using maximum strain as the criterion. This report documents the methods and results in two volumes. Volume 1 contains descriptions of the laminates, their fabrication and testing, the methods of analysis, the results, and the conclusions and recommendations. Volume 2 contains a comprehensive summary of the individual test results for all laminates.

Wetzel, Kyle K. (Wetzel Engineering, Inc. Lawrence, Kansas); Hermann, Thomas M. (Wichita state University, Wichita, Kansas); Locke, James (Wichita state University, Wichita, Kansas)

2005-11-01

66

Thermal Expansion Coefficients of Composite Materials Based on Energy Principles  

Microsoft Academic Search

Bounds on effective thermal expansion coefficients of isotropic and anisotropic composite materials consisting of isotropic phases are derived by employing extremum principles of thermoelasticity. Inequalities between certain approximate and exact forms of the potential and complementary energy functionals are first estab lished. These inequalities are then used in conjunction with a new method for minimizing the difference between upper and

R. A. Schapery

1968-01-01

67

Free vibration of advanced anisotropic multilayered composites with arbitrary boundary conditions  

NASA Astrophysics Data System (ADS)

Advanced composite stratified structures are of particular interest in numerous industrial areas such as the aerospace and aircraft industries. The main feature of these anisotropic materials is their ability to be tailored for specific applications by optimizing design parameters such as stacking sequence, ply orientation and performance targets. Designing through optimization principles requires the knowledge of an objective function which integrates all the unknowns of the materials therefore an accurate component-level modeling of stratified structures is necessary. Classical formulation available in the literature typically assumes a number of unknowns that increases with the number of layers and this sets serious limitations when trying to solve practical problems. As an alternative an advanced generalized modeling of multilayered composites with arbitrary boundary conditions is proposed in the present paper. This formulation is of a hybrid type which combines the advantages of both single-layer of the First Shear Deformation Theory and multi-layered approach. The number of unknowns is completely independent of the number of layers and a rigorous transfer matrix approach is developed from the interface conditions, which allows the parameters of the last layer to be iteratively related to those of the first layer. The Rayleigh-Ritz method is used in conjunction with a non-orthogonal polynomial basis to establish the free vibration. The model is then validated under free-free boundary conditions against data available in the literature in the case of isotropic, anisotropic angle-ply composites. Excellent agreement is obtained with a relative error less than 1%, which assesses the validity of the present model. In addition a sensitivity analysis is performed on the boundary stiffness required to model boundary conditions to illustrate the complexity associated with the arbitrary boundary conditions when using artificial springs.

Woodcock, Roland L.

2008-05-01

68

Processing composite materials  

NASA Technical Reports Server (NTRS)

The fabrication of several composite structural articles including DC-10 upper aft rudders, L-1011 vertical fins and composite biomedical appliances are discussed. Innovative composite processing methods are included.

Baucom, R. M.

1982-01-01

69

Accelerated Insertion of Materials - Composites.  

National Technical Information Service (NTIS)

The objective of the Accelerated Insertion of Materials - Composites (AIM-C) program is to develop and validate new approaches for materials development that will accelerate the insertion of materials into production hardware.

G. Havskjold

2001-01-01

70

Notched Strength of Composite Materials  

Microsoft Academic Search

A macroscopic model for predicting the strength of a composite laminate containing a circular notch is introduced. A property, which quantifies the reduction in strength of a given composite material or laminate due to a circular notch, is proposed. The superposition of notched strength data for several important composite material systems and laminate stacking sequences is achieved through development of

R. Byron Pipes; Robert C. Wetherhold; John W. Gillespie

1979-01-01

71

Analysis of the anisotropic viscoplastic-damage response of composite laminates - Continuum basis and computational algorithms  

NASA Technical Reports Server (NTRS)

The mathematical structure underlying the rate equations of a recently-developed constitutive model for the coupled viscoplastic-damage response of anisotropic composites is critically examined. In this regard, a number of tensor projection operators have been identified, and their properties were exploited to enable the development of a general computational framework for their numerical implementation using the Euler fully-implicit integration method. In particular, this facilitated (i) the derivation of explicit expressions of the (consistent) material tangent stiffnesses that are valid for both three-dimensional as well as subspace (e.g. plane stress) formulations, (ii) the implications of the symmetry or unsymmetry properties of these tangent operators from a thermodynamic standpoint, and (iii) the development of an effective time-step control strategy to ensure accuracy and convergence of the solution. In addition, the special limiting case of inviscid elastoplasticity is treated. The results of several numerical simulations are given to demonstrate the effectiveness of the schemes developed.

Saleeb, A. F.; Wilt, T. E.

1993-01-01

72

Composite material and method for production of improved composite material  

NASA Technical Reports Server (NTRS)

A laminated composite material with improved interlaminar strength and damage tolerance having short rods distributed evenly throughout the composite material perpendicular to the laminae. Each rod is shorter than the thickness of the finished laminate, but several times as long as the thickness of each lamina. The laminate is made by inserting short rods in layers of prepreg material, and then stacking and curing prepreg material with rods inserted therethrough.

Farley, Gary L. (Inventor)

1996-01-01

73

Composite structural materials  

NASA Technical Reports Server (NTRS)

The composite aircraft program component (CAPCOMP) is a graduate level project conducted in parallel with a composite structures program. The composite aircraft program glider (CAPGLIDE) is an undergraduate demonstration project which has as its objectives the design, fabrication, and testing of a foot launched ultralight glider using composite structures. The objective of the computer aided design (COMPAD) portion of the composites project is to provide computer tools for the analysis and design of composite structures. The major thrust of COMPAD is in the finite element area with effort directed at implementing finite element analysis capabilities and developing interactive graphics preprocessing and postprocessing capabilities. The criteria for selecting research projects to be conducted under the innovative and supporting research (INSURE) program are described.

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

1981-01-01

74

On minimal representations for constitutive equations of anisotropic elastic materials  

Microsoft Academic Search

The problem of determining minimal representations for anisotropic elastic constitutive equations is proposed and investigated. For elastic constitutive equations in any given case of anisotropy, it is shown that there exist generating sets consisting of six generators and such generating sets are minimal in all possible generating sets. This fact implies that most of the established results for representations of

Heng Xiao

1996-01-01

75

Composite materials: A compilation  

NASA Technical Reports Server (NTRS)

Design, analysis and fabrication techniques for boron-aluminum composite-structure technology is presented and a new method of joining different laminated composites without mechanical fasteners is proposed. Also discussed is a low-cost procedure for rigidifying expanded honeycomb tubing and piping simulations. A brief note on patent information is added.

1976-01-01

76

Modelling ultrasonic array signals in multilayer anisotropic materials using the angular spectrum decomposition of plane wave responses  

NASA Astrophysics Data System (ADS)

Ultrasonic arrays have seen increasing use for the characterisation of composite materials. In this paper, ultrasonic wave propagation in multilayer anisotropic materials has been modelled using plane wave and angular spectrum decomposition techniques. Different matrix techniques, such as the stiffness matrix method and the transfer matrix method, are used to calculate the reflection and transmission coefficients of ultrasonic plane waves in the considered media. Then, an angular decomposition technique is used to derive the bounded beams from finite-width ultrasonic array elements from the plane wave responses calculated earlier. This model is considered to be an analytical exact solution for the problem; hence the diffraction of waves in such composite materials can be calculated for different incident angles for a very wide range of frequencies. This model is validated against experimental measurements using the Full-Matrix Capture (FMC) of array data in both a homogeneous isotropic material, i.e. aluminium, and an inhomogeneous multilayer anisotropic material, i.e. a carbon fibre reinforced composite.

Humeida, Yousif; Pinfield, Valerie J.; Challis, Richard E.

2013-08-01

77

Combining topological sensitivity and genetic algorithms for identification inverse problems in anisotropic materials  

Microsoft Academic Search

The identification inverse problem is solved here for flaw detection in anisotropic materials by means of an innovative approach:\\u000a the combination of Genetic Algorithm and the Topological Sensitivity in anisotropic elasticity. The Topological Sensitivity provides a measure of the susceptibility of a defect being at a given\\u000a location. This is based on a linearized topological expansion, applying Boundary Integral Equations

Lucía Comino; Rafael Gallego; Guillermo Rus

2008-01-01

78

Extinction theorem and propagation of electromagnetic waves between two semi-infinite anisotropic magnetoelectric materials  

E-print Network

Based on molecular optics we investigate the reflection and refraction of an electromagnetic wave between two semi-infinite anisotropic magnetoelectric materials. In terms of Hertz vectors and the principle of superposition, we generalize the extinction theorem and derive the propagation characteristics of wave. Using these results we can easily explain the physical origin of Brewster effect. Our results extend the extinction theorem to the propagation of wave between two arbitrary anisotropic materials and the methods used can be applied to other problems of wave propagation in materials, such as scattering of light.

Weixing Shu; Zhongzhou Ren; Hailu Luo; Fei Li; Qin Wu

2006-09-26

79

Nondestructive methods of determining the dielectric constants of anisotropic polymeric materials  

Microsoft Academic Search

Procedures for determining the principal constants of the dielectric constant tensor of anisotropic polymeric materials are described. It is shown that the simplest solution of the problem corresponds to the use of external measuring capacitors. Two variants of measuring apparatus for determining the principal constants of the e tensor and the anisotropy coefficient of polymeric materials are described with reference

V. D. Shtraus

1974-01-01

80

The M-Integral for Computing Stress Intensity Factors in Generally Anisotropic Materials  

NASA Technical Reports Server (NTRS)

The objective of this project is to develop and demonstrate a capability for computing stress intensity factors in generally anisotropic materials. These objectives have been met. The primary deliverable of this project is this report and the information it contains. In addition, we have delivered the source code for a subroutine that will compute stress intensity factors for anisotropic materials encoded in both the C and Python programming languages and made available a version of the FRANC3D program that incorporates this subroutine. Single crystal super alloys are commonly used for components in the hot sections of contemporary jet and rocket engines. Because these components have a uniform atomic lattice orientation throughout, they exhibit anisotropic material behavior. This means that stress intensity solutions developed for isotropic materials are not appropriate for the analysis of crack growth in these materials. Until now, a general numerical technique did not exist for computing stress intensity factors of cracks in anisotropic materials and cubic materials in particular. Such a capability was developed during the project and is described and demonstrated herein.

Warzynek, P. A.; Carter, B. J.; Banks-Sills, L.

2005-01-01

81

Nanophase and Composite Optical Materials  

NASA Technical Reports Server (NTRS)

This talk will focus on accomplishments, current developments, and future directions of our work on composite optical materials for microgravity science and space exploration. This research spans the order parameter from quasi-fractal structures such as sol-gels and other aggregated or porous media, to statistically random cluster media such as metal colloids, to highly ordered materials such as layered media and photonic bandgap materials. The common focus is on flexible materials that can be used to produce composite or artificial materials with superior optical properties that could not be achieved with homogeneous materials. Applications of this work to NASA exploration goals such as terraforming, biosensors, solar sails, solar cells, and vehicle health monitoring, will be discussed.

2003-01-01

82

Carbon–Carbon Composite Materials  

Microsoft Academic Search

Data are summarized on the performance characteristics and properties of Russian-produced and foreign carbon–carbon composite materials for various engineering applications. The effect of neutron irradiation on their macroscopic properties and structure is examined. The relationships between the radiation-induced dimensional changes and properties of the composites are established, which can be used in assessing the engineering performance and optimizing the fabrication

Yu. S. Virgil'ev; I. P. Kalyagina

2004-01-01

83

On the theory of conductivity of anisotropic composites: A linear-concentration approximation of inclusions  

SciTech Connect

A general approach is proposed for calculating the conductivity of anisotropic composites with a low concentration of inclusions of an arbitrary shape. The contribution to effective conductivity {sigma}{sub e} , which is linear in concentration, is expressed in terms of the polarizability of the inclusion defined in a certain transformed system in which the inclusion is surrounded by an isotropic matrix. A transition to this system is performed using a symmetry transformation that does not change the equations for direct current.

Balagurov, B. Ya., E-mail: balagurov@deom.chph.ras.ru [Russian Academy of Science, Emanuel Institute of Biochemical Physics (Russian Federation)

2011-11-15

84

Buckling and Postbuckling of Anisotropic Laminated Cylindrical Shells with Piezoelectric Fiber Reinforced Composite Actuators  

Microsoft Academic Search

Compressive postbuckling under thermal environments and thermal postbuckling due to uniform temperature field are presented for an anisotropic laminated cylindrical thin shell with piezoelectric fiber reinforced composite (PFRC) actuators. The governing equations are based on the classical shell theory with a von Kármán-Donnell-type of kinematic nonlinearity and including the extension-twist, extension-flexural and flexural-twist couplings. The thermo-piezoelectric effects are also included

Hui-Shen Shen

2010-01-01

85

Fabrication, testing, and analysis of anisotropic carbon\\/glass hybrid composites: volume 1: technical report  

Microsoft Academic Search

Anisotropic carbon\\/glass hybrid composite laminates have been fabricated, tested, and analyzed. The laminates have been fabricated using vacuum-assisted resin transfer molding (VARTM). Five fiber complexes and a two-part epoxy resin system have been used in the study to fabricate panels of twenty different laminate constructions. These panels have been subjected to physical testing to measure density, fiber volume fraction, and

Kyle K. Wetzel; Thomas M. Hermann; James E. Locke

2005-01-01

86

Interaction of an anti-plane singularity with interfacial anti-cracks in cylindrically anisotropic composites  

Microsoft Academic Search

Anti-plane problem for a singularity interacting with interfacial anti-cracks (rigid lines) under uniform shear stress at\\u000a infinity in cylindrically anisotropic composites is investigated by utilizing a complex potential technique in this paper.\\u000a After obtaining the general solution for this problem, the closed solution for the interface containing one anti-crack is\\u000a presented analytically. In addition, the complex potentials for a screw

B. Li; Y. W. Liu; Q. H. Fang

2008-01-01

87

Fracture problems in composite materials  

NASA Technical Reports Server (NTRS)

A series of fracture problems in composite materials are identified, their methods of solution are briefly discussed, and some sample results are presented. The main problem of interest is the determination of the stress state in the neighborhood of localized imperfections such as cracks and inclusions which may exist in the composite. Particular emphasis is placed on the evaluation of quantities such as the stress intensity factors, the power of the stress singularity, and the strain energy release rate, which may be used directly or indirectly in connection with an appropriate fracture criterion for the prediction of fracture initiation and propagation load levels. The topics discussed include a crack in layered composites, a crack terminating at and going through a bi-material interface, a penny-shaped crack in a filament-reinforced elastic matrix, and inclusion problems in bonded materials.

Erdogan, F.

1972-01-01

88

Warm Forming of Aluminum Alloys using a Coupled ThermoMechanical Anisotropic Material Model  

Microsoft Academic Search

Temperature-dependant anisotropic material models for two types of automotive aluminum alloys (5754-O and 5182-O) were developed and implemented in LS-Dyna as a user material subroutine (UMAT) for coupled thermo-mechanical finite element analysis (FEA) of warm forming of aluminum alloys. The anisotropy coefficients of the Barlat YLD2000 plane stress yield function for both materials were calculated for the range of temperatures

Nader Abedrabbo; Farhang Pourboghrat; John E. Carsley

2005-01-01

89

Nonlinear optical materials based on ionic liquid crystals and anisotropic glasses of metal alkanoate  

Microsoft Academic Search

High demands of modern photonic technologies stimulate researches to create advanced optical and nonlinear optical materials. In this paper we review our recent results on nonlinear optical properties of novel materials based on ionic liquid crystals and anisotropic glasses of metal alkanoate. Such materials exhibit fast (ns-ps) and high enough ( 10?7?10?9 esu) third-order nonlinear optical response, and are promising

G. Klimusheva; Yu. Garbovskiy; A. Bordyuh; A. Gridyakina; S. Bugaychuk; A. Tolochko; D. Melnik; T. Mirnaya

2011-01-01

90

Anisotropic material properties of fused deposition modeling ABS  

Microsoft Academic Search

Rapid Prototyping (RP) technologies provide the ability to fabricate initial prototypes from various model materials. Stratasys Fused Deposition Modeling (FDM) is a typical RP process that can fabricate prototypes out of ABS plastic. To predict the mechanical behavior of FDM parts, it is critical to understand the material properties of the raw FDM process material, and the effect that FDM

Sung-Hoon Ahn; Michael Montero; Dan Odell; Shad Roundy; Paul K. Wright

2002-01-01

91

Analysis of diametral strain in uniaxial tensile and compression testing of round specimens of anisotropic materials  

Microsoft Academic Search

The development of elliptical cross sections in initially round test pieces of anisotropic materials makes it difficult to measure the true strain on a cross section using a transverse extensometer. In this paper, an analysis is given of the diametral strain and strain rate on a round cross section. Based on the experimental observation that static and dynamic microstructural changes

Henry S. Yang; Xiao-Ping S. Su; Bingzhe Bai

2000-01-01

92

Identification of structural defects in graphitic materials by gas-phase anisotropic etching  

E-print Network

materials by an anisotropic etching technique. Intrinsic and oxygen- or argon- plasma induced artificial could act as the initiation places for gasification reac- tions;3,4 defects in graphite intercalation including hyperthermal treatment by air or molecular oxygen,19­22 ion bombardment,23,24 oxygen plasma,25

Zhang, Guangyu

93

Modeling the Propagation of Elastic Waves in Generally Anisotropic Materials and Austenitic Steel Welds  

NASA Astrophysics Data System (ADS)

The inspection of welds composed of austenitic steels is difficult because these materials tend to form large, elongated anisotropic grains whose specific structure within welds is unknown. These grains are responsible for beam-steering of ultrasound. The paper presents software developed to predict wave interaction at an interface between generally anisotropic media and to trace rays through a previously published model of a multipass metal arc weld. Results involving a crack defect are compared to those of finite element simulations and reasons for differences are discussed.

Connolly, G. D.; Lowe, M. J. S.; Rokhlin, S. I.; Temple, J. A. G.

2008-02-01

94

Magnetoplasmons of the tilted anisotropic Dirac cone material ? -(BEDT-TTF)2I3  

NASA Astrophysics Data System (ADS)

We study the collective modes of a low-energy continuum model of the quasi-two-dimensional electron liquid in a layer of the organic compound ? -(BEDT-TTF)2I3 in a perpendicular magnetic field. As testified by zero magnetic field transport experiments and ab initio theory, this material hosts both massless and massive low-energy carriers, the former being described by two tilted and anisotropic Dirac cones. The polarizability of these cones is anisotropic, and two sets of magnetoplasmon modes occur between any two cyclotron resonances. We show that the tilt of the cones causes a unique intervalley damping effect: the upper hybrid mode of one cone is damped by the particle-hole continuum of the other cone in generic directions. We analyze how the presence of massive carriers affects the response of the system, and demonstrate how doping can tune ? -(BEDT-TTF)2I3 between regimes of isotropic and anisotropic screening.

Sári, Judit; T?ke, Csaba; Goerbig, Mark O.

2014-10-01

95

Pneumatic Characterization of Composite Materials  

Microsoft Academic Search

The dimensional change of some composite materials induced by ambient air pressure change was discovered and dubbed pneumatic strain in 2000. This pneumatic behavior closely resembles hygric behavior, and pneumatic strain is proportional to the ambient air pressure change by the coefficients of the pneumatic expansion. A method termed the suspension method was employed in this work to characterize the

Cho-Liang Tsai; Ming-Chang Cheng; Shun-Fa Hwang; Yi-Shiun Tsai

2002-01-01

96

Predicting Properties Of Composite Materials  

NASA Technical Reports Server (NTRS)

Micromechanical Combined Stress Analysis (MICSTRAN) computer code provides materials engineers with easy-to-use personal-computer-based software tool to calculate overall properties of composite, given properties of fibers and matrix. Computes overall thermoelastic parameters and stresses by micromechanical analysis. Written in FORTRAN 77.

Naik, Rajiv A.

1994-01-01

97

CHARACTERISTICS OF ELECTROMAGNETIC WAVE PROPAGATION IN BIAXIAL ANISOTROPIC LEFT-HANDED MATERIALS  

Microsoft Academic Search

Abstract—This paper investigates the characteristics of electromag- netic wave propagation in biaxially anisotropic left-handed materials (BA-LHMs) theoretically and numerically. We discuss under what con- ditions the anomalous refraction or reflection will occur at the interface when a plane wave passes from one isotropic right-handed material into another BA-LHM. Meanwhile the refraction angle of the wave vector and that of the

Wei Ding; Liang Chen; H. Liang

2007-01-01

98

Models of plates made of an anisotropic material  

Microsoft Academic Search

Numerous investigations including monographs [1 ? 4] are devoted to derivation of two-dimensional (2D) approximate models of plates and shells from the three-dimensional (3D) equations of the theory of elasticity. The presence of anisotropy of a material introduces additional difficulties. The 2D models for orthotropic and transversely isotropic materials [2?6] have been investigated well. The general anisotropy described by 21

P. E. Tovstik

2009-01-01

99

Pneumatic Behavior of Composite Materials  

Microsoft Academic Search

The dimensional change of some composite materials induced by ambient air pressure change was discovered and dubbed as pneumatic\\u000a strain in 2000. This pneumatic behavior is similar to the hygric behavior. The pneumatic strain is proportional to the ambient\\u000a air pressure change by the coefficients of pneumatic expansion. In this work, a technique termed suspending method was employed\\u000a for characterizing

Cho-Liang Tsai; Yi-Shiun Tsai

100

Fracture mechanics for delamination problems in composite materials  

NASA Technical Reports Server (NTRS)

A fracture mechanics approach to the well-known delamination problem in composite materials is presented. Based on the theory of anisotropic laminate elasticity and interlaminar fracture mechanics concepts, the composite delamination problem is formulated and solved. The exact order of the delamination crack-tip stress singularity is determined. Asymptotic stress and displacement fields for an interlaminar crack are obtained. Fracture mechanics parameters such as mixed-mode stress intensity factors, KI, KII, KIII, and the energy release rate, G, for composite delamination problems are defined. To illustrate the fundamental nature of the delamination crack behavior, solutions for edge-delaminated graphite-epoxy composites under uniform axial extension are presented. Effects of fiber orientation, ply thickness, and delamination length on the interlaminar fracture are examined.

Wang, S. S.

1983-01-01

101

An improved boundary force method for analyzing cracked anisotropic materials  

NASA Technical Reports Server (NTRS)

The Boundary Force Method (BFM), a form of indirect boundary element method, is used to analyze composite laminates with cracks. The BFM uses the orthotropic elasticity solution for a concentrated horizontal and vertical force and a moment applied at a point in a cracked, infinite sheet as the fundamental solution. The necessary stress functions for this fundamental solution were formulated using the complex variable theory of orthotropic elasticity. The current method is an improvement over a previous method using only forces and no moment. The improved method was verified by comparing it to accepted solutions for a finite-width, center-crack specimen subjected to uniaxial tension. Four graphite/epoxy laminates were used: (0 + or - 45/90)sub s, (0), (+ or - 45)sub s, and (+ or - 30)sub s. The BFM results agreed well with accepted solutions. Convergence studies showed that with the addition of the moment in the fundamental solution, the number of boundary elements required for a converged solution was significantly reduced. Parametric studies were done for two configurations for which no orthotropic solutions are currently available; a single edge crack and an inclined single edge crack.

Tan, Paul W.; Bigelow, Catherine A.

1988-01-01

102

An improved boundary force method for analysing cracked anisotropic materials  

NASA Technical Reports Server (NTRS)

The Boundary Force Method (BFM), a form of indirect boundary element method, is used to analyze composite laminates with cracks. The BFM uses the orthotropic elasticity solution for a concentrated horizontal and vertical force and a moment applied at a point in a cracked, infinite sheet as the fundamental solution. The necessary stress functions for this fundamental solution were formulated using the complex variables theory of orthotropic elasticity. The current method is an improvement over a previous method using only forces and no moment. The improved method was verified by comparing it to accepted solutions for a finite-width, center-crack specimen subjected to uniaxial tension. Four graphite/epoxy laminates were used: (0 + or - 45/90)sub s, (0), (+ or - 45)sub s, and (+ or - 30)sub s. The BFM results agreed well with accepted solutions. Convergence studies showed that with the addition of the moment in the fundamental solution, the number of boundary elements required for a converged solution was significantly reduced. Parametric studies were done for two configurations for which no orthotropic solutions are currently available; a single edge crack and an inclined single edge crack.

Tan, P. W.; Bigelow, C. A.

1989-01-01

103

Improved Silica Aerogel Composite Materials  

NASA Technical Reports Server (NTRS)

A family of aerogel-matrix composite materials having thermal-stability and mechanical- integrity properties better than those of neat aerogels has been developed. Aerogels are known to be excellent thermal- and acoustic-insulation materials because of their molecular-scale porosity, but heretofore, the use of aerogels has been inhibited by two factors: (1) Their brittleness makes processing and handling difficult. (2) They shrink during production and shrink more when heated to high temperatures during use. The shrinkage and the consequent cracking make it difficult to use them to encapsulate objects in thermal-insulation materials. The underlying concept of aerogel-matrix composites is not new; the novelty of the present family of materials lies in formulations and processes that result in superior properties, which include (1) much less shrinkage during a supercritical-drying process employed in producing a typical aerogel, (2) much less shrinkage during exposure to high temperatures, and (3) as a result of the reduction in shrinkage, much less or even no cracking.

Paik, Jong-Ah; Sakamoto, Jeffrey; Jones, Steven

2008-01-01

104

Anomalous optical behavior of LT-AlInAs related to anisotropic composition modulation  

SciTech Connect

The InGaAs/InAlAs system has proven to be very attractive for the fabrication of high performance electronic devices. Optical measurements and Transmission Electron Microscopy (TEM) were performed on Low Temperature(LT)-AlInAs layers grown by MBE at 400 C and compared with AlInAs grown at 530 C. An anisotropic composition modulation is observed along the [1--10] direction for the low temperature samples. The authors studied the effects of the V/III BEP ratio on this modulation to explain the LT-AlInAs optical properties.

Bearzi, E.; Benyattou, T.; Guillot, G. [INSA de Lyon, Villeurbanne (France); Marty, O.; Pitaval, M. [Univ. Lyon, Villeurbanne (France); Oustric, M.; Gendry, M.; Hollinger, G. [Ecole Centrale de Lyon, Ecully (France); Harmand, J.C.; Quillec, M. [CNET Bagneux (France)

1996-12-31

105

Characterization of Anisotropic Plasticity in Material Systems Using Modified Indentation-Based Techniques  

NASA Astrophysics Data System (ADS)

Plastic anisotropy in rolled sheets has traditionally been analyzed by conducting tensile tests on strips cut at different angles from the rolling direction and measuring the contraction ratios during testing. This method is tedious, yet sufficient for sheet metals but the application to other material systems is limited. For example, if one were to seek the properties of a coating-substrate system, such an analysis would be impractical due to the combined effects of the coating and the substrate on which it lies. Indentation-based experiments are a great candidate for evaluation of such properties in various material systems for a few, main reasons. Indentation testing machines are readily available commercially and in material characterization laboratories world-wide and are currently being used for the classification of various material properties. Second, the systems in which indentation can be used are far from limited; indentation testing is notorious for its large-scale applicability. Finally, indentation provides a means of inducing localized plastic deformation, which can ultimately serve as a great analysis tool for anisotropy in these properties for a given material. It is shown that examination of material flow in the contact region serves to uniquely characterize the degree of anisotropy. Therefore, the work presented in this dissertation pertains to the development, design, and testing of a set of virtual experiments using Finite Element Modeling with the specific aim to uniquely characterize the anisotropic plastic property of a material in all normal directions given minimal material data prior to testing. Current characterization methods and yield criteria are reviewed, and results suggesting anisotropic yielding in coatings are presented. Further, indentation stress-strain behavior of plastically anisotropic materials is examined, and finally, characterization methods involving indentation-based techniques are presented.

Kalkhoran, Salmon Masbooghi

106

Anisotropic material synthesis by capillary flow in a fluid stripe  

PubMed Central

We present a simple bench-top technique to produce centimeter long concentration gradients in biomaterials incorporating soluble, material, and particle gradients. By patterning hydrophilic regions on a substrate, a stripe of prepolymer solution is held in place on a glass slide by a hydrophobic boundary. Adding a droplet to one end of this “pre-wet” stripe causes a rapid capillary flow that spreads the droplet along the stripe to generate a gradient in the relative concentrations of the droplet and pre-wet solutions. The gradient length and shape are controlled by the pre-wet and droplet volumes, stripe thickness, fluid viscosity and surface tension. Gradient biomaterials are produced by crosslinking gradients of prepolymer solutions. Demonstrated examples include a concentration gradient of cells encapsulated in three dimensions (3D) within a homogeneous biopolymer and a constant concentration of cells encapsulated in 3D within a biomaterial gradient exhibiting a gradient in cell spreading. The technique employs coated glass slides that may be purchased or custom made from tape and hydrophobic spray. The approach is accessible to virtually any researcher or student and should dramatically reduce the time required to synthesize a wide range of gradient biomaterials. Moreover, since the technique employs passive mechanisms it is ideal for remote or resource poor settings. PMID:21684595

Hancock, Matthew J.; Piraino, Francesco; Camci-Unal, Gulden; Rasponi, Marco; Khademhosseini, Ali

2011-01-01

107

A critical survey of wave propagation and impact in composite materials  

NASA Technical Reports Server (NTRS)

A review of the field of stress waves in composite materials is presented covering the period up to December 1972. The major properties of waves in composites are discussed and a summary is made of the major experimental results in this field. Various theoretical models for analysis of wave propagation in laminated, fiber and particle reinforced composites are surveyed. The anisotropic, dispersive and dissipative properties of stress pulses and shock waves in such materials are reviewed. A review of the behavior of composites under impact loading is presented along with the application of wave propagation concepts to the determination of impact stresses in composite plates.

Moon, F. C.

1973-01-01

108

Mechanical fastening of composite materials  

NASA Astrophysics Data System (ADS)

High-sensitivity moire interferometry was used to obtain the stress/strain distribution in the vicinity of mechanically fastened hole arrays in a glass/epoxy thermoset composite material. Experimental results are presented for three fastener configurations: the tandem configuration (two holes in a row parallel to the load direction), the parallel configuration (two fastening holes in a row perpendicular to the load direction), and the three-hole fastener array with all three holes equally loaded. The advantage of utilizing as multihole array in a connection rather than a single pin-loaded hole is demonstrated.

Zimmerman, K. B.

1992-08-01

109

Methods of determining loads and fiber orientations in anisotropic non-crystalline materials using energy flux deviation  

NASA Astrophysics Data System (ADS)

An ultrasonic wave is applied to an anisotropic sample material in an initial direction and an angle of flux deviation of the ultrasonic wave front is measured from this initial direction. This flux deviation angle is induced by the unknown applied load. The flux shift is determined between this flux deviation angle and a previously determined angle of flux deviation of an ultrasonic wave applied to a similar anisotropic reference material under an initial known load condition. This determined flux shift is then compared to a plurality of flux shifts of a similarly tested, similar anisotropic reference material under a plurality of respective, known load conditions, whereby the load applied to the particular anisotropic sample material is determined. A related method is disclosed for determining the fiber orientation from known loads and a determined flux shift.

Prosser, William H.; Kriz, Ronald D.; Fitting, Dale W.

1993-05-01

110

http://jtc.sagepub.com Composite Materials  

E-print Network

http://jtc.sagepub.com Composite Materials Journal of Thermoplastic DOI: 10.1177/0892705708089473 2008; 21; 209Journal of Thermoplastic Composite Materials Qinglin Wu Sun-Young Lee, In-Aeh Kang, Geum://www.sagepublications.com at: can be foundJournal of Thermoplastic Composite MaterialsAdditional services and information

111

Properties of composite materials for cryogenic applications  

Microsoft Academic Search

Composite materials are used in a wide variety of cryogenic applications because of their unique and highly tailorable properties. These cryogenic applications of composites may be, for the sake of discussion, classified as support structures, vessels, or electrical insulation. Examples of these applications are presented, with a brief discussion of the critical material properties associated with each application. Composite material

J. B Schutz

1998-01-01

112

Composite materials for fusion applications  

SciTech Connect

Ceramic matrix composites, CMCs, are being considered for advanced first-wall and blanket structural applications because of their high-temperature properties, low neutron activation, low density and low coefficient of expansion coupled with good thermal conductivity and corrosion behavior. This paper presents a review and analysis of the hermetic, thermal conductivity, corrosion, crack growth and radiation damage properties of CMCs. It was concluded that the leak rates of a gaseous coolant into the plasma chamber or tritium out of the blanket could exceed design criteria if matrix microcracking causes existing porosity to become interconnected. Thermal conductivities of unirradiated SiC/SiC and C/SiC materials are about 1/2 to 2/3 that of Type 316 SS whereas the thermal conductivity for C/C composites is seven times larger. The thermal stress figure-of-merit value for CMCs exceeds that of Type 316 SS for a single thermal cycle. SiC/SiC composites are very resistant to corrosion and are expected to be compatible with He or Li coolants if the O{sub 2} concentrations are maintained at the appropriate levels. CMCs exhibit subcritical crack growth at elevated temperatures and the crack velocity is a function of the corrosion conditions. The radiation stability of CMCs will depend on the stability of the fiber, microcracking of the matrix, and the effects of gaseous transmutation products on properties. 23 refs., 14 figs., 1 tab.

Jones, R.H.; Henager, C.H. Jr.; Hollenberg, G.W.

1991-10-01

113

Mechanics of interfacial composite materials.  

PubMed

Recent experiments and simulations have demonstrated that particle-covered fluid/fluid interfaces can exist in stable nonspherical shapes as a result of the steric jamming of the interfacially trapped particles. The jamming confers the interface with solidlike properties. We provide an experimental and theoretical characterization of the mechanical properties of these armored objects, with attention given to the two-dimensional granular state of the interface. Small inhomogeneous stresses produce a plastic response, while homogeneous stresses produce a weak elastic response. Shear-driven particle-scale rearrangements explain the basic threshold needed to obtain the near-perfect plastic deformation that is observed. Furthermore, the inhomogeneous stress state of the interface is exhibited experimentally by using surfactants to destabilize the particles on the surface. Since the interfacially trapped particles retain their individual characteristics, armored interfaces can be recognized as a kind of composite material with distinct chemical, structural, and mechanical properties. PMID:17107022

Subramaniam, Anand Bala; Abkarian, Manouk; Mahadevan, L; Stone, Howard A

2006-11-21

114

Quantum electrodynamics near anisotropic polarizable materials: Casimir-Polder shifts near multilayers of graphene  

NASA Astrophysics Data System (ADS)

In a recent paper, we formulated a theory of nonrelativistic quantum electrodynamics in the presence of an inhomogeneous Huttner-Barnett dielectric. Here we generalize the formalism to anisotropic materials and show how it may be modified to include conducting surfaces. We start with the derivation of the photon propagator for a slab of material and use it to work out the energy-level shift near a medium whose conductivity in the direction parallel to the surface far exceeds that in the direction perpendicular to the surface. We investigate the influence of the anisotropy of the material's electromagnetic response on the Casimir-Polder shifts, both analytically and numerically, and show that it may have a significant impact on the atom-surface interaction, especially in the nonretarded regime, i.e., for small atom-surface separations. Our results for the energy shift may be used to estimate the Casimir-Polder force acting on quantum objects close to multilayers of graphene or graphite. They are particularly important for the case of trapped cold molecules whose dispersive interactions with surfaces often fall within the nonretarded regime where the anisotropy of the material strongly influences the Casimir-Polder force. We also give a formula for the change in the spontaneous decay rate of an excited atom or molecule near an anisotropically conducting surface.

Eberlein, Claudia; Zietal, Robert

2012-12-01

115

Strain rate behavior of composite materials  

Microsoft Academic Search

The effect of strain rate on the compressive and shear behavior of carbon\\/epoxy composite materials was investigated. Strain rate behavior of composites with fiber waviness was also studied. Falling weight impact system and servohydraulic testing machine were used for dynamic characterisation of composite materials in compression at strain rates up to several hundred per second. Strain rates below 10s?1 were

H. M. Hsiao; I. M. Daniel

1998-01-01

116

Warm Forming of Aluminum Alloys using a Coupled Thermo-Mechanical Anisotropic Material Model  

SciTech Connect

Temperature-dependant anisotropic material models for two types of automotive aluminum alloys (5754-O and 5182-O) were developed and implemented in LS-Dyna as a user material subroutine (UMAT) for coupled thermo-mechanical finite element analysis (FEA) of warm forming of aluminum alloys. The anisotropy coefficients of the Barlat YLD2000 plane stress yield function for both materials were calculated for the range of temperatures 25 deg. C-260 deg. C. Curve fitting was used to calculate the anisotropy coefficients of YLD2000 and the flow stress as a function of temperature. This temperature-dependent material model was successfully applied to the coupled thermo-mechanical analysis of stretching of aluminum sheets and results were compared with experiments.

Abedrabbo, Nader; Pourboghrat, Farhang [Department of Mechanical Engineering, Michigan State University, East Lansing, MI 48824-1226 (United States); Carsley, John E. [General Motors Research and Development Center, Warren, MI 48090 (United States)

2005-08-05

117

Polyolefin composites containing a phase change material  

DOEpatents

A composite useful in thermal energy storage, said composite being formed of a polyolefin matrix having a phase change material such as a crystalline alkyl hydrocarbon incorporated therein, said polyolefin being thermally form stable; the composite is useful in forming pellets, sheets or fibers having thermal energy storage characteristics; methods for forming the composite are also disclosed.

Salyer, Ival O. (Dayton, OH)

1991-01-01

118

Thin film dielectric composite materials  

DOEpatents

A dielectric composite material comprising at least two crystal phases of different components with TiO.sub.2 as a first component and a material selected from the group consisting of Ba.sub.1-x Sr.sub.x TiO.sub.3 where x is from 0.3 to 0.7, Pb.sub.1-x Ca.sub.x TiO.sub.3 where x is from 0.4 to 0.7, Sr.sub.1-x Pb.sub.x TiO.sub.3 where x is from 0.2 to 0.4, Ba.sub.1-x Cd.sub.x TiO.sub.3 where x is from 0.02 to 0.1, BaTi.sub.1-x Zr.sub.x O.sub.3 where x is from 0.2 to 0.3, BaTi.sub.1-x Sn.sub.x O.sub.3 where x is from 0.15 to 0.3, BaTi.sub.1-x Hf.sub.x O.sub.3 where x is from 0.24 to 0.3, Pb.sub.1-1.3x La.sub.x TiO.sub.3+0.2x where x is from 0.23 to 0.3, (BaTiO.sub.3).sub.x (PbFeo.sub.0.5 Nb.sub.0.5 O.sub.3).sub.1-x where x is from 0.75 to 0.9, (PbTiO.sub.3).sub.- (PbCo.sub.0.5 W.sub.0.5 O.sub.3).sub.1-x where x is from 0.1 to 0.45, (PbTiO.sub.3).sub.x (PbMg.sub.0.5 W.sub.0.5 O.sub.3).sub.1-x where x is from 0.2 to 0.4, and (PbTiO.sub.3).sub.x (PbFe.sub.0.5 Ta.sub.0.5 O.sub.3).sub.1-x where x is from 0 to 0.2, as the second component is described. The dielectric composite material can be formed as a thin film upon suitable substrates.

Jia, Quanxi (Los Alamos, NM); Gibbons, Brady J. (Los Alamos, NM); Findikoglu, Alp T. (Los Alamos, NM); Park, Bae Ho (Los Alamos, NM)

2002-01-01

119

Slab waveguide with air core layer and anisotropic left-handed material claddings as a sensor  

NASA Astrophysics Data System (ADS)

A three-layer slab waveguide with air core layer and anisotropic left-handed material claddings is investigated for sensing applications. Different from the waveguide mode sensors and surface plasmon resonance sensors in which the analyte is placed in the evanescent field region, the proposed sensor contains the sample in the core region that supports the oscillating field. Due to the strong concentration of the electromagnetic field in the analyte medium, the proposed device exhibits unusual sensitivity enhancement. The simulations revealed that the sensitivity improvement of TE3 mode compared to conventional evanescent wave sensor is approximately a factor of 20.

Taya, S. A.

2014-12-01

120

Study on the anisotropic photonic band gaps in three-dimensional tunable photonic crystals containing the epsilon-negative materials and uniaxial materials  

NASA Astrophysics Data System (ADS)

In this paper, the properties of anisotropic photonic band gaps (PBGs) for three-dimensional (3D) photonic crystals (PCs) composed of the anisotropic positive-index materials (the uniaxial materials) and the epsilon-negative (ENG) materials with body-centered-cubic (bcc) lattices are theoretically studied by a modified plane wave expansion (PWE) method, which are the uniaxial materials spheres inserted in the epsilon-negative materials background. The anisotropic photonic band gaps (PBGs) and one flatbands region can be achieved in first irreducible Brillouin zone. The influences of the ordinary-refractive index, extraordinary-refractive index, filling factor, the electronic plasma frequency, the dielectric constant of ENG materials and the damping factor on the properties of anisotropic PBGs for such 3D PCs are studied in detail, respectively, and some corresponding physical explanations are also given. The numerical results show that the anisotropy can open partial band gaps in such 3D PCs with bcc lattices composed of the ENG materials and uniaxial materials, and the complete PBGs can be obtained compared to the conventional 3D PCs containing the isotropic materials. The calculated results also show that the anisotropic PBGs can be manipulated by the parameters as mentioned above except for the damping factor. Introducing the uniaxial materials into 3D PCs containing the ENG materials can obtain the larger complete PBGs as such 3D PCs with high symmetry, and also provides a way to design the tunable devices.

Zhang, Hai-Feng; Liu, Shao-Bin; Li, Bing-Xiang

2014-08-01

121

Nonlinear Dynamic Properties of Layered Composite Materials  

SciTech Connect

We present an application of the asymptotic homogenization method to study wave propagation in a one-dimensional composite material consisting of a matrix material and coated inclusions. Physical nonlinearity is taken into account by considering the composite's components as a Murnaghan material, structural nonlinearity is caused by the bonding condition between the components.

Andrianov, Igor V.; Topol, Heiko; Weichert, Dieter [Institute of General Mechanics, RWTH Aachen University, Termplergraben 64, Aachen, D-52062 (Germany); Danishevs'kyy, Vladyslav V. [Prydniprovs'ka State Academy of Civil Engineering and Architecture, Dnipropetrovs'k, Chernishevs'kogo 24a, UA-49600 (Ukraine)

2010-09-30

122

A fatigue damage model of composite materials  

Microsoft Academic Search

The mechanical properties of composite materials degrade progressively with the increasing of the number of cyclic loadings. Based on the stiffness degradation rule of composites, a phenomenological fatigue damage model is presented in this paper, which contains two material parameters. They are proportional to the fatigue life of materials and inversely proportional to the fatigue loading level. Thirteen sets of

Fuqiang Wu; WeiXing Yao

2010-01-01

123

Design, fabrication and characterization of a monolithic focusing piezoceramic transducer for an anisotropic material  

NASA Astrophysics Data System (ADS)

Piezoceramic transducers shaped as spherical caps are widely used to focus ultrasound waves in isotropic materials. For anisotropic materials, the sound wave surface is not spherical and the transducer surface should be adjusted to reproduce a portion of this wave surface to focus the emitted sound properly. In this article, we show how to design such a transducer and how to fabricate it in lab on a standard machine from a rod of raw piezo ceramic material. The main features of its electrical impedance response are well reproduced by a numerical model, allowing the identification of most of its vibrational modes. We finally measured the sound field emitted by such a transducer and found its focusing efficiency similar to that of spherical caps in isotropic media.

Souris, Fabien; Grucker, Jules; Garroum, Nabil; Leclercq, Arnaud; Isac, Jean-Michel; Dupont-Roc, Jacques; Jacquier, Philippe

2014-06-01

124

Mechanical Fasteners for Advanced Composite Materials  

NASA Technical Reports Server (NTRS)

Advanced composite materials, which are increasingly being used to build aircraft, have different properties than the metals they replace. Fasteners intended for composite-material joints must be designed and selected to allow for these differences. For example, blind fasteners (one-sided access) used to assemble composite-to-composite joints have been redesigned to expand to larger diameters to resist pull-through and cocking failures. The fastener designs needed for composite materials are reviewed. Topics discussed are: galvanic corrosion, pull-through resistance, fastener rotation, installation damage, fastener galling and conductivity. A blind fastener recently developed by SPS Technologies is described to show how these requirements are incorporated.

Landt, R. C.

1985-01-01

125

Method for machining holes in composite materials  

NASA Technical Reports Server (NTRS)

A method for boring well defined holes in a composite material such as graphite/epoxy is discussed. A slurry of silicon carbide powder and water is projected onto a work area of the composite material in which a hole is to be bored with a conventional drill bit. The silicon carbide powder and water slurry allow the drill bit, while experiencing only normal wear, to bore smooth, cylindrical holes in the composite material.

Daniels, Julia G. (inventor); Ledbetter, Frank E., III (inventor); Clemons, Johnny M. (inventor); Penn, Benjamin G. (inventor); White, William T. (inventor)

1987-01-01

126

Morphology and microstructure of composite materials  

NASA Technical Reports Server (NTRS)

Lightweight continuous carbon fiber based polymeric composites are currently enjoying increasing acceptance as structural materials capable of replacing metals and alloys in load bearing applications. As with most new materials, these composites are undergoing trials with several competing processing techniques aimed at cost effectively producing void free consolidations with good mechanical properties. As metallic materials have been in use for several centuries, a considerable database exists on their morphology - microstructure; and the interrelationships between structure and properties have been well documented. Numerous studies on composites have established the crucial relationship between microstructure - morphology and properties. The various microstructural and morphological features of composite materials, particularly those accompanying different processing routes, are documented.

Tiwari, S. N.; Srinivansan, K.

1991-01-01

127

Rediscovering black phosphorus as an anisotropic layered material for optoelectronics and electronics  

NASA Astrophysics Data System (ADS)

Graphene and transition metal dichalcogenides (TMDCs) are the two major types of layered materials under intensive investigation. However, the zero-bandgap nature of graphene and the relatively low mobility in TMDCs limit their applications. Here we reintroduce black phosphorus (BP), the most stable allotrope of phosphorus with strong intrinsic in-plane anisotropy, to the layered-material family. For 15-nm-thick BP, we measure a Hall mobility of 1,000 and 600?cm2?V-1?s-1 for holes along the light (x) and heavy (y) effective mass directions at 120?K. BP thin films also exhibit large and anisotropic in-plane optical conductivity from 2 to 5??m. Field-effect transistors using 5?nm BP along x direction exhibit an on-off current ratio exceeding 105, a field-effect mobility of 205?cm2?V-1?s-1, and good current saturation characteristics all at room temperature. BP shows great potential for thin-film electronics, infrared optoelectronics and novel devices in which anisotropic properties are desirable.

Xia, Fengnian; Wang, Han; Jia, Yichen

2014-07-01

128

Quantitative ultrasonic testing of acoustically anisotropic materials with verification on austenitic and dissimilar weld joints  

NASA Astrophysics Data System (ADS)

Austenitic stainless steel materials are widely used in a variety of industry sectors. In particular, the material is qualified to meet the design criteria of high quality in safety related applications. For example, the primary loop of the most of the nuclear power plants in the world, due to high durability and corrosion resistance, is made of this material. Certain operating conditions may cause a range of changes in the integrity of the component, and therefore require nondestructive testing at reasonable intervals. These in-service inspections are often performed using ultrasonic techniques, in particular when cracking is of specific concern. However, the coarse, dendritic grain structure of the weld material, formed during the welding process, is extreme and unpredictably anisotropic. Such structure is no longer direction-independent to the ultrasonic wave propagation; therefore, the ultrasonic beam deflects and redirects and the wave front becomes distorted. Thus, the use of conventional ultrasonic testing techniques using fixed beam angles is very limited and the application of ultrasonic Phased Array techniques becomes desirable. The "Sampling Phased Array" technique, invented and developed by Fraunhofer IZFP, allows the acquisition of time signals (A-scans) for each individual transducer element of the array along with fast image reconstruction techniques based on synthetic focusing algorithms. The reconstruction considers the sound propagation from each image pixel to the individual sensor element. For anisotropic media, where the sound beam is deflected and the sound path is not known a-priori, a novel phase adjustment technique called "Reverse Phase Matching" is implemented. By taking into account the anisotropy and inhomogeneity of the weld structure, a ray tracing algorithm for modeling the acoustic wave propagation and calculating the sound propagation time is applied. This technique can be utilized for 2D and 3D real time image reconstruction. The "Gradient Constant Descent Method" (GECDM), an iterative algorithm, is implemented, which is essential for examination of inhomogeneous anisotropic media having unknown properties (elastic constants). The Sampling Phased Array technique with Reverse Phase Matching extended by GECDM-technique determines unknown elastic constants and provides reliable and efficient quantitative flaw detection in the austenitic welds. The validation of ray-tracing algorithm and GECDM-method is performed by number of experiments on test specimens with artificial as well as natural material flaws. A mechanized system for ultrasonic testing of stainless steel and dissimilar welds is developed. The system works on both conventional and Sampling Phased Array techniques. The new frontend ultrasonic unit with optical data link allows the 3D visualization of the inspection results in real time.

Boller, C.; Pudovikov, S.; Bulavinov, A.

2012-05-01

129

Integral Equation Method for Electromagnetic Wave Propagation in Stratified Anisotropic Dielectric-Magnetic Materials  

NASA Astrophysics Data System (ADS)

We investigate the propagation of electromagnetic waves in stratified anisotropic dielectric-magnetic materials using the integral equation method (IEM). Based on the superposition principle, we use Hertz vector formulations of radiated fields to study the interaction of wave with matter. We derive in a new way the dispersion relation, Snell's law and reflection/transmission coefficients by self-consistent analyses. Moreover, we find two new forms of the generalized extinction theorem. Applying the IEM, we investigate the wave propagation through a slab and disclose the underlying physics, which are further verified by numerical simulations. The results lead to a unified framework of the IEM for the propagation of wave incident either from a medium or vacuum in stratified dielectric-magnetic materials.

Shu, Wei-Xing; Fu, Na; Lü, Xiao-Fang; Luo, Hai-Lu; Wen, Shuang-Chun; Fan, Dian-Yuan

2010-11-01

130

Composite materials and method of making  

DOEpatents

A method for forming improved composite materials using a thermosetting polyester urethane hybrid resin, a closed cavity mold having an internal heat transfer mechanism used in this method, and the composite materials formed by this method having a hybrid of a carbon fiber layer and a fiberglass layer.

Simmons, Kevin L [Kennewick, WA; Wood, Geoffrey M [North Saanich, CA

2011-05-17

131

Composite materials for biomedical applications: a review.  

PubMed

The word "composite" refers to the combination, on a macroscopic scale, of two or more materials, different for composition, morphology and general physical properties. In many cases, and depending on the constituent properties, composites can be designed with a view to produce materials with properties tailored to fulfill specific chemical, physical or mechanical requirements. Therefore over the past 40 years the use of composites has progressively increased, and today composite materials have many different applications, i.e., aeronautic, automotive, naval, and so on. Consequently many composite biomaterials have recently been studied and tested for medical application. Some of them are currently commercialized for their advantages over traditional materials. Most human tissues such as bones, tendons, skin, ligaments, teeth, etc., are composites, made up of single constituents whose amount, distribution, morphology and properties determine the final behavior of the resulting tissue or organ. Man-made composites can, to some extent, be used to make prostheses able to mimic these biological tissues, to match their mechanical behavior and to restore the mechanical functions of the damaged tissue. Different types of composites that are already in use or are being investigated for various biomedical applications are presented in this paper. Specific advantages and critical issues of using composite biomaterials are also described (Journal of Applied Bio-materials & Biomechanics 2003; 1: 3-18). PMID:20803468

Salernitano, E; Migliaresi, C

2003-01-01

132

Flame-retardant composite materials  

NASA Technical Reports Server (NTRS)

The properties of eight different graphite composite panels fabricated using four different resin matrices and two types of graphite reinforcement are described. The resin matrices included: VPSP/BMI, a blend of vinylpolystyryl pyridine and bismaleimide; BMI, a bismaleimide; and phenolic and PSP, a polystyryl pyridine. The graphite fiber used was AS-4 in the form of either tape or fabric. The properties of these composites were compared with epoxy composites. It was determined that VPSP/BMI with the graphite tape was the optimum design giving the lowest heat release rate.

Kourtides, Demetrius A.

1991-01-01

133

Fourth Symposium on Composite Materials  

Microsoft Academic Search

The high temperature fatigue of a (O)12 tungsten fiber reinforced copper matrix composite was investigated. Specimens having fiber volume percentages of 10 and 36 were fatigued under fully-reversed, strain-controlled conditions at both 260 and 560 C. The fatigue life was found to be independent of fiber volume fraction because fatigue damage preferentially occurred in the matrix. Also, the composite fatigue

M. J. Verrilli; T. P. Gabb

1990-01-01

134

New textile composite materials development, production, application  

NASA Technical Reports Server (NTRS)

New textile composite materials development, production, and application are discussed. Topics covered include: super-high-strength, super-high-modulus fibers, filaments, and materials manufactured on their basis; heat-resistant and nonflammable fibers, filaments, and textile fabrics; fibers and textile fabrics based on fluorocarbon poylmers; antifriction textile fabrics based on polyfen filaments; development of new types of textile combines and composite materials; and carbon filament-based fabrics.

Mikhailov, Petr Y.

1993-01-01

135

Polarization in Cary model 14 spectrophotometers and its effect on transmittance measurements of anisotropic materials.  

PubMed

Cary model 14 spectrophotometers like other prism and grating instruments have polarization characteristics that affect the transmittance values of anisotropic or dichroic materials. In the uv, the degree of polarization is fairly constant from 3000 A to 4000 A, whereas in the visible, it shows some variation with wavelength. In the near ir, the variation of the degree of polarization with wavelength is large, showing sharply defined maxima at approximately 0.77 micro, 0.97 micro, and 1.27 micro. The spectral transmittance of optical quality sapphire, a uniaxial crystal, cut at 45 degrees , 60 degrees , and 90 degrees to the c axis, showed undulations for certain orientations of the privileged directions. PMID:20068821

Hills, M E; Olsen, A L; Nichols, L W

1968-08-01

136

Resin impregnation during the manufacturing of composite materials  

SciTech Connect

A numerical and experimental study of resin-impregnation processes during the manufacturing of composite materials was performed. A formulation of the problem was accomplished using ideas taken from the theory of flow through anisotropic porous media. A treatment of the resin-impregnation front that exists during impregnation processes was also suggested. Using these ideas, a methodology for simulating two-dimensional isothermal resin-impregnation processes under conditions of specified injection rate or specified applied pressure was developed. Special attention was directed at the simulation of resin-transfer modeling and resin film stacking/compression modeling processes. Due to the geometrical complexity of the situations to be modeled, the computational technique of boundary-fitted coordinate systems encompassing numerical grid generation was chosen. It was found that the simulation of impregnation under specified applied-pressure loading conditions is much more involved than that of the specified resin injection rate conditions.

Coulter, J.P.

1988-01-01

137

Combinatorial synthesis of inorganic or composite materials  

DOEpatents

Methods and apparatus for the preparation and use of a substrate having an array of diverse materials in predefined regions thereon. A substrate having an array of diverse materials thereon is generally prepared by delivering components of materials to predefined regions on a substrate, and simultaneously reacting the components to form at least two materials or, alternatively, allowing the components to interact to form at least two different materials. Materials which can be prepared using the methods and apparatus of the present invention include, for example, covalent network solids, ionic solids and molecular solids. More particularly, materials which can be prepared using the methods and apparatus of the present invention include, for example, inorganic materials, intermetallic materials, metal alloys, ceramic materials, organic materials, organometallic materials, nonbiological organic polymers, composite materials (e.g., inorganic composites, organic composites, or combinations thereof), etc. Once prepared, these materials can be screened for useful properties including, for example, electrical, thermal, mechanical, morphological, optical, magnetic, chemical, or other properties. Thus, the present invention provides methods for the parallel synthesis and analysis of novel materials having useful properties.

Goldwasser, Isy (Palo Alto, CA); Ross, Debra A. (Mountain Ranch, CA); Schultz, Peter G. (La Jolla, CA); Xiang, Xiao-Dong (Danville, CA); Briceno, Gabriel (Baldwin Park, CA); Sun, Xian-Dong (Fremont, CA); Wang, Kai-An (Cupertino, CA)

2010-08-03

138

Materials research at Stanford University. [composite materials, crystal structure, acoustics  

NASA Technical Reports Server (NTRS)

Research activity related to the science of materials is described. The following areas are included: elastic and thermal properties of composite materials, acoustic waves and devices, amorphous materials, crystal structure, synthesis of metal-metal bonds, interactions of solids with solutions, electrochemistry, fatigue damage, superconductivity and molecular physics and phase transition kinetics.

1975-01-01

139

Oxygen Compatibility Testing of Composite Materials  

NASA Technical Reports Server (NTRS)

Composite materials offer significant weight-saving potential for aerospace applications in propellant and oxidizer tanks. This application for oxygen tanks presents the challenge of being oxygen compatible in addition to complying with the other required material characteristics. This effort reports on the testing procedures and data obtained in examining and selecting potential composite materials for oxygen tank usage. Impact testing of composites has shown that most of these materials initiate a combustion event when impacted at 72 ft-lbf in the presence of liquid oxygen, though testing has also shown substantial variability in reaction sensitivities to impact. Data for screening of 14 potential composites using the Bruceton method is given herein and shows that the 50-percent reaction frequencies range from 17 to 67 ft-lbf. The pressure and temperature rises for several composite materials were recorded to compare the energy releases as functions of the combustion reactions with their respective reaction probabilities. The test data presented are primarily for a test pressure of 300 psia in liquid oxygen. The impact screening process is compared with oxygen index and autogenous ignition test data for both the composite and the basic resin. The usefulness of these supplemental tests in helping select the most oxygen compatible materials is explored. The propensity for mechanical impact ignition of the composite compared with the resin alone is also examined. Since an ignition-free composite material at the peak impact energy of 72 ft-lbf has not been identified, composite reactivity must be characterized over the impact energy level and operating pressure ranges to provide data for hazard analyses in selecting the best potential material for liquid tank usage.

Engel, Carl D.; Watkins, Casey N.

2006-01-01

140

Homogenization of two-phase elasto-plastic composite materials and structures  

Microsoft Academic Search

We develop homogenization schemes and numerical algorithms for two-phase elasto-plastic composite materials and structures. A Hill-type incremental formulation enables the simulation of unloading and cyclic loadings. It also allows to handle any rate-independent model for each phase. We study the crucial issue of tangent operators: elasto-plastic (or “continuum”) versus algorithmic (or “consistent”), and anisotropic versus isotropic. We apply two methods

I. Doghri; A. Ouaar

2003-01-01

141

Cryogenic Microwave Anisotropic Artificial Frank Trang  

E-print Network

Cryogenic Microwave Anisotropic Artificial Materials by Frank Trang B.S., University of California entitled: Cryogenic Microwave Anisotropic Artificial Materials written by Frank Trang has been approved.D., Electrical Engineering) Cryogenic Microwave Anisotropic Artificial Materials Thesis directed by Professor

Popovic, Zoya

142

Thermal Characterization of Anisotropic Materials at High Temperature Through Integral Methods and Localized Pulsed Technique  

NASA Astrophysics Data System (ADS)

New applications in aerospace or energy industries require the development of new materials at high temperature exhibiting high anisotropic properties. Their thermal characterization requires the development of specific experimental benches. In this article, a new experiment is presented which allows one to estimate through only one experiment the three diffusivities of an orthotropic material at high temperatures without the need of vacuum. The estimation procedure is very fast and accurate due to using, on the one hand, integral transforms that allows one to get rid of the spatial distribution of the flash energy, and on the other hand, an infrared camera that provides a large amount of experimental data. And thanks to the use of a nonlinear parameter estimation and estimations made directly on Fourier transforms of the temperature field, the heat flux stimulation is no longer necessary to be Dirac in time. To validate the method and the experimental facility, measurements were performed on a Ti-6Al-4V alloy from room temperature up to 1000 ^{circ }{ C }. In addition, particular attention has been paid to the thermal coupling that can appear between the low conducting materials and the air, and a criterion has been established to determine if the in-plane thermal diffusivity measurements can be affected or not.

Souhar, Youssef; Rémy, Benjamin; Degiovanni, Alain

2013-02-01

143

Life prediction and constitutive models for engine hot section anisotropic materials  

NASA Technical Reports Server (NTRS)

The results are presented of a program designed to develop life prediction and constitutive models for two coated single crystal alloys used in gas turbine airfoils. The two alloys are PWA 1480 and Alloy 185. The two oxidation resistant coatings are PWA 273, an aluminide coating, and PWA 286, an overlay NiCoCrAlY coating. To obtain constitutive and fatigue data, tests were conducted on uncoated and coated specimens loaded in the CH76 100 CH110 , CH76 110 CH110 , CH76 111 CH110 and CH76 123 CH110 crystallographic directions. Two constitutive models are being developed and evaluated for the single crystal materials: a micromechanic model based on crystallographic slip systems, and a macroscopic model which employs anisotropic tensors to model inelastic deformation anisotropy. Based on tests conducted on the overlay coating material, constitutive models for coatings also appear feasible and two initial models were selected. A life prediction approach was proposed for coated single crystal materials, including crack initiation either in the coating or in the substrate. The coating initiated failures dominated in the tests at load levels typical of gas turbine operation. Coating life was related to coating stress/strain history which was determined from specimen data using the constitutive models.

Swanson, G. A.; Linask, I.; Nissley, D. M.; Norris, P. P.; Meyer, T. G.; Walker, K. P.

1987-01-01

144

Multiscale Modeling and Homogenization of Composite Materials  

E-print Network

of composites that account for the micro-structuralpertinent micro-structural infor- mation. For compositecomposite materials is to use the finite element method. In particular, since accounting for all the micro-

Mseis, George

2010-01-01

145

Reliability and micromechanics of composite materials  

Microsoft Academic Search

A methodology is proposed to evaluate the reliability of composites. Micromechanical analysis is utilized as a basis for the representation of the effects of constituent properties on global response. The analysis is then combined with the models of structural reliability to study the influence of micro-level material parameters on reliability of composites under static loadings.

Zhanjun Gao

1992-01-01

146

Composite Materials for Wind Power Turbine Blades  

Microsoft Academic Search

Renewable energy resources, of which wind energy is prominent, are part of the solution to the global energy problem. Wind turbine and the rotorblade concepts are reviewed, and loadings by wind and gravity as important factors for the fatigue performance of the materials are considered. Wood and composites are discussed as candidates for rotorblades. The fibers and matrices for composites

Povl Brøndsted; Hans Lilholt; Aage Lystrup

2005-01-01

147

Composite materials inspection. [ultrasonic vibration holographic NDT  

NASA Technical Reports Server (NTRS)

Investigation of the application requirements, advantages, and limitations of nondestructive testing by a technique of ultrasonic-vibration holographic-interferometry readout used in a production control facility for the inspection of a single product such as composite compressor blades. It is shown that, for the detection and characterization of disbonds in composite material structures, this technique may represent the most inclusive test method.

Erf, R. K.

1974-01-01

148

Candida albicans adhesion to composite resin materials  

Microsoft Academic Search

The adhesion of Candida albicans to dental restorative materials in the human oral cavity may promote the occurrence of oral candidosis. This study aimed\\u000a to compare the susceptibility of 14 commonly used composite resin materials (two compomers, one ormocer, one novel silorane,\\u000a and ten conventional hybrid composites) to adhere Candida albicans. Differences in the amount of adhering fungi should be

Ralf Bürgers; Wulf Schneider-Brachert; Martin Rosentritt; Gerhard Handel; Sebastian Hahnel

2009-01-01

149

Method to fabricate layered material compositions  

DOEpatents

A new class of processes suited to the fabrication of layered material compositions is disclosed. Layered material compositions are typically three-dimensional structures which can be decomposed into a stack of structured layers. The best known examples are the photonic lattices. The present invention combines the characteristic features of photolithography and chemical-mechanical polishing to permit the direct and facile fabrication of, e.g., photonic lattices having photonic bandgaps in the 0.1-20.mu. spectral range.

Fleming, James G. (Albuquerque, NM); Lin, Shawn-Yu (Albuquerque, NM)

2002-01-01

150

Acoustic emission monitoring of polymer composite materials  

NASA Technical Reports Server (NTRS)

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.

Bardenheier, R.

1981-01-01

151

Method of making a composite refractory material  

DOEpatents

A composite refractory material is prepared by combining boron carbide with furan resin to form a mixture containing about 8 wt. % furan resin. The mixture is formed into a pellet which is placed into a grit pack comprising an oxide of an element such as yttrium to form a sinterable body. The sinterable body is sintered under vacuum with microwave energy at a temperature no greater than 2000.degree. C. to form a composite refractory material.

Morrow, Marvin S. (Kingston, TN); Holcombe, Cressie E. (Knoxville, TN)

1995-01-01

152

Fatigue and fracture research in composite materials  

NASA Technical Reports Server (NTRS)

The fatigue, fracture, and impact behavior of composite materials are investigated. Bolted and bonded joints are included. The solutions developed are generic in scope and are useful for a wide variety of structural applications. The analytical tools developed are used to demonstrate the damage tolerance, impact resistance, and useful fatigue life of structural composite components. Standard tests for screening improvements in materials and constituents are developed.

Obrien, T. K.

1982-01-01

153

Measuring the elastic properties of anisotropic materials by means of indentation experiments  

Microsoft Academic Search

The unloading process in an indentation experiment is usually modeled by considering the contact of a rigid punch with an elastically isotropic half space. Here we extend the analysis to elastically anisotropic solids, We review some of the basic formulae for describing the indentation of elastically anisotropic solids with axisymmetric indenters, We show how the indentation modulus can be calculated

JOOST J. VLASSAK; W. D. NIX

1994-01-01

154

Offgassing test methodology for composite materials  

NASA Technical Reports Server (NTRS)

A significant increase in the use of composite materials has occurred during the past 20 years. Associated with this increased use is the potential for employees to be exposed to offgassing components from composite systems. Various components in composite systems, particularly residual solvents, offgas under various conditions. The potential for offgassing to occur increases as a composite material is heated either during cure or during lay-up operations. Various techniques can be employed to evaluate the offgassing characteristics of a composite system. A joint effort between AIA and SACMA resulted in the drafting of a proposed test method for evaluating the offgassing potential of composite materials. The purpose of testing composite materials for offgassing is to provide the industrial hygienist with information which can be used to assess the safety of the workplace. This paper outlines the proposed test method and presents round robin testing data associated with the test method. Also in this presentation is a discussion of classes of compounds which require specialized sampling techniques.

Scheer, Dale A.

1994-01-01

155

Anisotropically structured magnetic aerogel monoliths.  

PubMed

Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture. PMID:25255203

Heiligtag, Florian J; Airaghi Leccardi, Marta J I; Erdem, Derya; Süess, Martin J; Niederberger, Markus

2014-10-01

156

Micromechanical modeling of damage and inelasticity of composite materials in macroscopic structural analysis  

SciTech Connect

The method of cells has been extended to include damage or debonding between all adjacent subcells using a finite element formulation for the original cells assembly. Damage is implemented by placing a nonlinear three-dimensional spring between adjacent subcells. With this arrangement the damage is inherently anisotropic. The ``nonlinear substructure`` cells finite element model is incorporated as a user defined material routine in a general purpose finite element code. The primary motivation for casting the method of cells as a finite element assemblage is to provide a composite constitutive model that facilitates the incorporation of various constituent material models, as well as any level of detail desired in the microstructure geometry. At present, the constituent material models may be anisotropic elastic or isotropic viscoelastic-plastic, while damage evolution is based on the macroscopic strain. The capability of the model is demonstrated through analyses of some simple structures loaded to failure.

Macek, R.W.; Gardner, J.P. [Los Alamos National Lab., NM (United States); Hackett, R.M. [Mississippi Univ., University, MS (United States)

1994-12-01

157

3-D textile reinforcements in composite materials  

SciTech Connect

Laminated composite materials have been used in structural applications since the 1960s. However, their high cost and inability to accommodate fibers in the laminate`s thickness direction greatly reduce their damage tolerance and impact resistance. The second generation of materials--3-D textile reinforced composites--offers significant cost reduction, and by incorporating reinforcement in the thickness direction, dramatically increases damage tolerance and impact resistance. However, methods for predicting mechanical properties of 3-D textile reinforced composite materials tend to be more complex. These materials also have disadvantages--particularly in regard to crimps in the yarns--that require more research. Textile preforms, micro- and macromechanical modeling, manufacturing processes, and characterization all need further development. As researchers overcome these problems, this new generation of composites will emerge as a highly competitive family of materials. This book provides a state-of-the-art account of this promising technology. In it, top experts describe the manufacturing processes, highlight the advantages, identify the main applications, analyze methods for predicting mechanical properties, and detail various reinforcement strategies, including grid structure, knitted fabric composites, and the braiding technique. Armed with the information in this book, readers will be prepared to better exploit the advantages of 3-D textile reinforced composites, overcome its disadvantages, and contribute to the further development of the technology.

Miravete, A. [Univ. of Zaragoza (Spain)

1999-11-01

158

Micromechanics of composite materials under compressive loading  

Microsoft Academic Search

A common thread joining many engineered materials used dominantly under compressive loading is the presence of a high modulus secondary phase, either fiber or particulate, embedded within a lower modulus matrix phase. To improve their toughness, a frictional or a less-than-coherent interface is strived for in the manufacture of these composite materials. To form a better understanding of the complex

G. Laird; T. C. Kennedy

1995-01-01

159

ADVANCED COMPOSITE MATERIALS FOR BRIDGES Sami RIZKALLA  

E-print Network

1. SUMMARY ADVANCED COMPOSITE MATERIALS FOR BRIDGES Sami RIZKALLA ISIS Canada Network of Centres bridges are being built with materials that have significantly higher strength in comparison to steel associated with concrete bridges due to the corrosion of steel reinforcements. This paper presents

160

Gradient composite materials for artificial intervertebral discs.  

PubMed

Composites with the gradient of Young's modulus constitute a new group of biomimetic materials which affect the proper distribution of stresses between the implant and the bone. The aim of this article was to examine the mechanical properties of gradient materials based on carbon fibre-polysulfone composite, and to compare them to the properties of a natural intervertebral disc. Gradient properties were provided by different orientation or volume fraction of carbon fibres in particular layers of composites. The results obtained during in vitro tests displayed a good durability of the gradient materials put under long-term static load. However, the configuration based on a change in the volume fraction of the fibres seems more advantageous than the one based on a change of the fibres' orientation. The materials under study were designed to replace the intervertebral disc. The effect of Young's modulus of the material layers on the stress distribution between the tissue and the implant was analyzed and the biomimetic character of the gradient composites was stated. Unlike gradient materials, the pure polysulfone and the non-gradient composite resulted in the stress concentration in the region of nucleus pulposus, which is highly disadvantageous and does not occur in the stress distribution of natural intervertebral discs. PMID:25306938

Migacz, Katarzyna; Ch?opek, Jan; Morawska-Chochó?, Anna; Ambroziak, Maciej

2014-01-01

161

Anisotropically structured magnetic aerogel monoliths  

NASA Astrophysics Data System (ADS)

Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture.Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture. Electronic supplementary information (ESI) available: Digital photographs of dispersions and gels with different water-to-ethanol ratios; magnetic measurements of an anatase aerogel containing 0.25 mol% Fe3O4 nanoparticles; XRD patterns of the iron oxide and titania nanoparticles. See DOI: 10.1039/c4nr04694c

Heiligtag, Florian J.; Airaghi Leccardi, Marta J. I.; Erdem, Derya; Süess, Martin J.; Niederberger, Markus

2014-10-01

162

Scalable fabrication of anisotropic micro-rods from food-grade materials using an in shear flow dispersion–solvent attrition technique  

Microsoft Academic Search

We report a scalable fabrication of novel, food-grade anisotropic micro-rods from shellac and ethyl cellulose with controllable morphology which was studied using scanning electron microscopy and optical microscopy. The aqueous suspensions of these anisotropic materials show great potential for preparation of super-stable food-grade foams.

Andrew L. Campbell; Benjamin L. Holt; Simeon D. Stoyanov; Vesselin N. Paunov

2008-01-01

163

Composite Materials for Wind Power Turbine Blades  

NASA Astrophysics Data System (ADS)

Renewable energy resources, of which wind energy is prominent, are part of the solution to the global energy problem. Wind turbine and the rotorblade concepts are reviewed, and loadings by wind and gravity as important factors for the fatigue performance of the materials are considered. Wood and composites are discussed as candidates for rotorblades. The fibers and matrices for composites are described, and their high stiffness, low density, and good fatigue performance are emphasized. Manufacturing technologies for composites are presented and evaluated with respect to advantages, problems, and industrial potential. The important technologies of today are prepreg (pre-impregnated) technology and resin infusion technology. The mechanical properties of fiber composite materials are discussed, with a focus on fatigue performance. Damage and materials degradation during fatigue are described. Testing procedures for documentation of properties are reviewed, and fatigue loading histories are discussed, together with methods for data handling and statistical analysis of (large) amounts of test data. Future challenges for materials in the field of wind turbines are presented, with a focus on thermoplastic composites, new structural materials concepts, new structural design aspects, structural health monitoring, and the coming trends and markets for wind energy.

Brøndsted, Povl; Lilholt, Hans; Lystrup, Aage

2005-08-01

164

Fabrication of single-crystalline microspheres with high sphericity from anisotropic materials.  

PubMed

Microspheres with high sphericity exhibit unique functionalities. In particular, their high symmetry makes them excellent omnidirectional optical resonators. As such perfect micrometre-sized spheres are known to be formed by surface tension, melt cooling is a popular method for fabricating microspheres. However, it is extremely difficult to produce crystalline microspheres using this method because their surfaces are normally faceted. Only microspheres of polymers, glass, or ceramics have been available, while single-crystalline microspheres, which should be useful in optical applications, have been awaiting successful production. Here we report the fabrication of single-crystalline semiconductor microspheres that have surfaces with atomic-level smoothness. These microspheres were formed by performing laser ablation in superfluid helium to create and moderately cool a melt of the anisotropic semiconductor material. This novel method provides cooling conditions that are exceptionally suited for the fabrication of single-crystalline microspheres. This finding opens a pathway for studying the hidden mechanism of anisotropy-free crystal growth and its applications. PMID:24898213

Okamoto, Shinya; Inaba, Kazuhiro; Iida, Takuya; Ishihara, Hajime; Ichikawa, Satoshi; Ashida, Masaaki

2014-01-01

165

New demands on manufacturing of composite materials  

SciTech Connect

Traditionally the field of advanced composites has been dominated by the needs of the aerospace industry. This has strongly influenced the materials and processes developed. However, during the last few years, a shift of emphasis into other engineering areas has been obvious. Branches such as the mechanical industry, ground transportation, the building industry and the leisure industry are today defining many of the new areas of application for these materials. In these applications fiber-reinforced composites are not just used in large structures but also in crucial small complex-shaped elements of larger machinery in order to improve overall performance. To satisfy these new demands, it is essential to develop innovative material systems and processing techniques which enable the production of composite parts with complex geometries at reasonable cost and with high precision. Most likely the solution to this task lies in the closely integrated development of the material system and the manufacturing method. Several different approaches are today taken in order to reach this goal for composite materials. Furthermore, it is nowadays important that the introduction of any new material or application, especially for high volume production, be accompanied by a thorough life-cycle and environmental plan.

Manson, J.A.E. [Ecole Polytechnique Federale de Lausanne (Switzerland). Lab. de Technologie des Composites et Polymeres

1994-12-31

166

Ultrasonic Nondestructive Evaluation Techniques Applied to the Quantitative Characterization of Textile Composite Materials  

NASA Technical Reports Server (NTRS)

In this Progress Report, we describe our further development of advanced ultrasonic nondestructive evaluation methods applied to the characterization of anisotropic materials. We present images obtained from experimental measurements of ultrasonic diffraction patterns transmitted through water only and transmitted through water and a thin woven composite. All images of diffraction patterns have been included on the accompanying CD-ROM in the JPEG format and Adobe TM Portable Document Format (PDF), in addition to the inclusion of hardcopies of the images contained in this report. In our previous semi-annual Progress Report (NAG 1-1848, December, 1996), we proposed a simple model to simulate the effect of a thin woven composite on an insonifying ultrasonic pressure field. This initial approach provided an avenue to begin development of a robust measurement method for nondestructive evaluation of anisotropic materials. In this Progress Report, we extend that work by performing experimental measurements on a single layer of a five-harness biaxial woven composite to investigate how a thin, yet architecturally complex, material interacts with the insonifying ultrasonic field. In Section 2 of this Progress Report we describe the experimental arrangement and methods for data acquisition of the ultrasonic diffraction patterns upon transmission through a thin woven composite. We also briefly describe the thin composite specimen investigated. Section 3 details the analysis of the experimental data followed by the experimental results in Section 4. Finally, a discussion of the observations and conclusions is found in Section 5.

Miller, James G.

1997-01-01

167

Impact testing of textile composite materials  

NASA Technical Reports Server (NTRS)

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.

Portanova, Marc

1995-01-01

168

Computational modeling of composite material fires.  

SciTech Connect

Composite materials behave differently from conventional fuel sources and have the potential to smolder and burn for extended time periods. As the amount of composite materials on modern aircraft continues to increase, understanding the response of composites in fire environments becomes increasingly important. An effort is ongoing to enhance the capability to simulate composite material response in fires including the decomposition of the composite and the interaction with a fire. To adequately model composite material in a fire, two physical model development tasks are necessary; first, the decomposition model for the composite material and second, the interaction with a fire. A porous media approach for the decomposition model including a time dependent formulation with the effects of heat, mass, species, and momentum transfer of the porous solid and gas phase is being implemented in an engineering code, ARIA. ARIA is a Sandia National Laboratories multiphysics code including a range of capabilities such as incompressible Navier-Stokes equations, energy transport equations, species transport equations, non-Newtonian fluid rheology, linear elastic solid mechanics, and electro-statics. To simulate the fire, FUEGO, also a Sandia National Laboratories code, is coupled to ARIA. FUEGO represents the turbulent, buoyantly driven incompressible flow, heat transfer, mass transfer, and combustion. FUEGO and ARIA are uniquely able to solve this problem because they were designed using a common architecture (SIERRA) that enhances multiphysics coupling and both codes are capable of massively parallel calculations, enhancing performance. The decomposition reaction model is developed from small scale experimental data including thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) in both nitrogen and air for a range of heating rates and from available data in the literature. The response of the composite material subject to a radiant heat flux boundary condition is examined to study the propagation of decomposition fronts of the epoxy and carbon fiber and their dependence on the ambient conditions such as oxygen concentration, surface flow velocity, and radiant heat flux. In addition to the computational effort, small scaled experimental efforts to attain adequate data used to validate model predictions is ongoing. The goal of this paper is to demonstrate the progress of the capability for a typical composite material and emphasize the path forward.

Brown, Alexander L.; Erickson, Kenneth L.; Hubbard, Joshua Allen; Dodd, Amanda B.

2010-10-01

169

Formation of binary phase gratings in photopolymer-liquid crystal composites by a surface-controlled anisotropic phase separation  

SciTech Connect

We report on formation of binary phase gratings in photopolymer-liquid crystal (PLC) composites using a surface-controlled phase separation method. The binary nature of the PLC phase gratings is produced by employing a single step photo-ablation through an amplitude photomask which precisely controls the interfacial interactions between the LC and the photopolymer on the alignment layer. A subsequent illumination of the ultraviolet light onto the whole PLC promotes an anisotropic phase separation resulting in the formation of distinct binary patterns for the PLC structure. The electrically tunable diffraction properties of the binary phase gratings are presented.

Park, Jae-Hong; Khoo, Iam Choon; Yu, Chang-Jae; Jung, Min-Sik; Lee, Sin-Doo [216 Electrical Engineering East, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); School of Electrical Engineering no. 32, Seoul National University, Kwanak P.O. Box 34, Seoul 151-600 (Korea, Republic of)

2005-01-10

170

Investigation of anisotropic photonic band gaps in three-dimensional magnetized plasma photonic crystals containing the uniaxial material  

NASA Astrophysics Data System (ADS)

In this paper, the dispersive properties of three-dimensional (3D) magnetized plasma photonic crystals (MPPCs) composed of anisotropic dielectric (the uniaxial material) spheres immersed in homogeneous magnetized plasma background with face-centered-cubic (fcc) lattices are theoretically investigated by the plane wave expansion method, as the Voigt effects of magnetized plasma are considered. The equations for calculating the anisotropic photonic band gaps (PBGs) in the first irreducible Brillouin zone are theoretically deduced. The anisotropic PBGs and two flatbands regions can be obtained. The effects of the ordinary-refractive index, extraordinary-refractive index, filling factor, plasma frequency, and external magnetic field on the dispersive properties of the 3D MPPCs are investigated in detail, respectively, and some corresponding physical explanations are also given. The numerical results show that the anisotropy can open partial band gaps in 3D MPPCs with fcc lattices and the complete PBGs can be found compared to the conventional 3D MPPCs doped by the isotropic material. The bandwidths of PBGs can be tuned by introducing the magnetized plasma into 3D PCs containing the uniaxial material. It is also shown that the anisotropic PBGs can be manipulated by the ordinary-refractive index, extraordinary-refractive index, filling factor, plasma frequency, and external magnetic field, respectively. The locations of flatbands regions cannot be manipulated by any parameters except for the plasma frequency and external magnetic field. Introducing the uniaxial material can obtain the complete PBGs as the 3D MPPCs with high symmetry and also provides a way to design the tunable devices.

Zhang, Hai-Feng; Liu, Shao-Bin; Kong, Xiang-Kun

2013-09-01

171

Investigation of anisotropic photonic band gaps in three-dimensional magnetized plasma photonic crystals containing the uniaxial material  

SciTech Connect

In this paper, the dispersive properties of three-dimensional (3D) magnetized plasma photonic crystals (MPPCs) composed of anisotropic dielectric (the uniaxial material) spheres immersed in homogeneous magnetized plasma background with face-centered-cubic (fcc) lattices are theoretically investigated by the plane wave expansion method, as the Voigt effects of magnetized plasma are considered. The equations for calculating the anisotropic photonic band gaps (PBGs) in the first irreducible Brillouin zone are theoretically deduced. The anisotropic PBGs and two flatbands regions can be obtained. The effects of the ordinary-refractive index, extraordinary-refractive index, filling factor, plasma frequency, and external magnetic field on the dispersive properties of the 3D MPPCs are investigated in detail, respectively, and some corresponding physical explanations are also given. The numerical results show that the anisotropy can open partial band gaps in 3D MPPCs with fcc lattices and the complete PBGs can be found compared to the conventional 3D MPPCs doped by the isotropic material. The bandwidths of PBGs can be tuned by introducing the magnetized plasma into 3D PCs containing the uniaxial material. It is also shown that the anisotropic PBGs can be manipulated by the ordinary-refractive index, extraordinary-refractive index, filling factor, plasma frequency, and external magnetic field, respectively. The locations of flatbands regions cannot be manipulated by any parameters except for the plasma frequency and external magnetic field. Introducing the uniaxial material can obtain the complete PBGs as the 3D MPPCs with high symmetry and also provides a way to design the tunable devices.

Zhang, Hai-Feng [College of Electronic and Information Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China) [College of Electronic and Information Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Nanjing Artillery Academy, Nanjing 211132 (China)] [China; Liu, Shao-Bin; Kong, Xiang-Kun [College of Electronic and Information Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)] [College of Electronic and Information Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)

2013-09-15

172

Surface Waves in Anisotropic Elastic Materials for Which the Matrix N(v) is Extraordinary Degenerate, Degenerate, or Semisimple  

Microsoft Academic Search

The 6 × 6 real matrix N(v) for anisotropic elastic materials under a two-dimensional steady-state motion with speed v is extraordinary degenerate when N(v) has three identical complex eigenvalues p but has only one associated eigenvector. It has been an open question if such an N(v) exists for surface waves. In this paper we first modify the solution for ordinary

T. C. T. Ting

1997-01-01

173

Testing of NCSX Composite Coil Material Properties  

SciTech Connect

The National Compact Stellarator Experiment (NCSX) is now in design and requires 18 modular coils that are constructed to a highly complex geometry. The modular coil conductors are designed as a composite of a fine gauge stranded copper cable shaped to the required geometry and vacuum impregnated with a resin. These composite conductors exhibit unique material properties that must be determined and verified through testing. The conductor material properties are necessary for design modeling and performance validation. This paper will present the methods used to test and measure the coil conductor material properties, the unique challenges in measuring these complex materials at both room and liquid nitrogen temperatures and the results of those tests.

Kozub, Thomas; Jurczynski, Stephan; Chrzanowski, James [Princeton Plasma Physics Laboratory (United States)

2005-05-15

174

Ground exposure of composite materials for helicopters  

NASA Technical Reports Server (NTRS)

Residual strength results are presented on four composite material systems that were exposed for three years at locations on the North American Continent. The exposure locations are near the areas where Bell Model 206L Helicopters, that are in a NSA/U.S. Army sponsored flight service program, are flying in daily commercial service. The composite 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. All material systems exhibited good strength retention in compression and short beam shear. The Kevlar-49/LRF-277 epoxy retained 88 to 93 percent of the baseline strength while the other material systems exceeded 95 percent of baseline strength. Residual tensile strength of all materials did not show a significant reduction. The available moisture absorption data is also presented.

Baker, D. J.

1984-01-01

175

Thermographic analysis of the anisotropy in the thermal conductivity of composite materials  

NASA Astrophysics Data System (ADS)

Pitch-based graphite fibers, when used as a reinforcement in either polymeric or metal matrix composites, can significantly increase the in- plane thermal conductivity. An opportunity is thus presented by these composite materials to passively manage waste heat in electronics applications. Rule-of-mixtures calculations have predicted the thermal management performance of these composite materials when the fibrous reinforcements are in the form of either woven fabric or tape layups and the reinforcement orientation is either unidirectional or cross-plied. Many factors, however, complicate the prediction, including: fiber-to- matrix interfacial thermal resistance, the interply thermal resistance, and the highly anisotropic fiber thermal conductivity. Verification of the predictions was sought by the use of IR thermography. Heat was applied by a point source to the surface of the composite while the resulting thermal pattern was monitored and recorded thermographically.

Burleigh, Douglas D.; De La Torre, William

1991-03-01

176

Composite materials for rail transit systems  

NASA Technical Reports Server (NTRS)

The potential is explored for using composite materials in urban mass transit systems. The emphasis was to identify specific advantages of composite materials in order to determine their actual and potential usage for carbody and guideway structure applications. The literature was reviewed, contacts were made with major domestic system operators, designers, and builders, and an analysis was made of potential composite application to railcar construction. Composites were found to be in use throughout the transit industry, usually in secondary or auxiliary applications such as car interior and nonstructural exterior panels. More recently, considerable activity has been initiated in the area of using composites in the load bearing elements of civil engineering structures such as highway bridges. It is believed that new and improved manufacturing refinements in pultrusion and filament winding will permit the production of beam sections which can be used in guideway structures. The inherent corrosion resistance and low maintenance characteristics of composites should result in lowered maintenance costs over a prolonged life of the structure.

Griffin, O. Hayden, Jr.; Guerdal, Zafer; Herakovich, Carl T.

1987-01-01

177

Composite materials in flexible multibody systems  

Microsoft Academic Search

In this work the flexible multibody dynamics formulations of complex models are extended to include elastic components made of laminated composite materials. The only limitation for the deformation of a structural member is that it must be elastic and linear when described in a body fixed frame. A finite element model for each flexible body is obtained such that the

Maria Augusta Neto; Jorge A. C. Ambrósio; Rogério P. Leal

2006-01-01

178

MECHANICS METHODOLOGY FOR TEXTILE PREFORM COMPOSITE MATERIALS  

Microsoft Academic Search

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

Clarence C. Poe

1996-01-01

179

Data-mined similarity function between material compositions  

E-print Network

A new method for assessing the similarity of material compositions is described. A similarity measure is important for the classification and clustering of compositions. The similarity of the material compositions is ...

Yang, Lusann

180

Wave propagation in anisotropic medium due to an oscillatory point source with application to unidirectional composites  

NASA Technical Reports Server (NTRS)

The far-field displacements in an infinite transversely isotropic elastic medium subjected to an oscillatory concentrated force are derived. The concepts of velocity surface, slowness surface and wave surface are used to describe the geometry of the wave propagation process. It is shown that the decay of the wave amplitudes depends not only on the distance from the source (as in isotropic media) but also depends on the direction of the point of interest from the source. As an example, the displacement field is computed for a laboratory fabricated unidirectional fiberglass epoxy composite. The solution for the displacements is expressed as an amplitude distribution and is presented in polar diagrams. This analysis has potential usefulness in the acoustic emission (AE) and ultrasonic nondestructive evaluation of composite materials. For example, the transient localized disturbances which are generally associated with AE sources can be modeled via this analysis. In which case, knowledge of the displacement field which arrives at a receiving transducer allows inferences regarding the strength and orientation of the source, and consequently perhaps the degree of damage within the composite.

Williams, J. H., Jr.; Marques, E. R. C.; Lee, S. S.

1986-01-01

181

Anisotropic Thermal and Electrical Properties of Thin Thermal Interface Layers of Graphite Nanoplatelet-Based Composites  

PubMed Central

Thermal interface materials (TIMs) are crucial components of high density electronics and the high thermal conductivity of graphite makes this material an attractive candidate for such applications. We report an investigation of the in-plane and through-plane electrical and thermal conductivities of thin thermal interface layers of graphite nanoplatelet (GNP) based composites. The in-plane electrical conductivity exceeds its through-plane counterpart by three orders of magnitude, whereas the ratio of the thermal conductivities is about 5. Scanning electron microscopy reveals that the anisotropy in the transport properties is due to the in-plane alignment of the GNPs which occurs during the formation of the thermal interface layer. Because the alignment in the thermal interface layer suppresses the through-plane component of the thermal conductivity, the anisotropy strongly degrades the performance of GNP-based composites in the geometry required for typical thermal management applications and must be taken into account in the development of GNP-based TIMs.

Tian, Xiaojuan; Itkis, Mikhail E.; Bekyarova, Elena B.; Haddon, Robert C.

2013-01-01

182

Autophagous spacecraft composite materials for orbital propulsion  

NASA Astrophysics Data System (ADS)

We are developing structural polymer composite materials that can be converted into fuels and combusted with oxidizers for orbital propulsion of spacecraft. We have identified candidate materials and demonstrated sustained combustion with nitrogen tetroxide (NTO) as an oxidizer. To improve reaction chemistry we have evaluated several energetic additives. Detailed material compatibility tests were conducted to identify stable combinations of structural polymer and energetic additives. We have also demonstrated sustained combustion of structural polymeric materials with embedded additives and NTO. In the next phase of research, we plan to investigate hydrogen peroxide as the oxidizer. Samples of composites comprising thin metallic facesheets, structural polymer propellant matrix, and metallic mesh reinforcements (that also serve as electrical heaters/igniters for pyrolysis) were fabricated and their mechanical properties were measured. Concept of a spacecraft structural stringer, which also functions as a thruster, was developed using the composite material formulation. Both all solid and hybrid stringer-thruster designs have been developed. Prototype stringer-thrusters will be fabricated and tested in Phase II.

Joshi, Prakash; Upschulte, Bernard L.; Gelb, Alan H.; Green, B. David; Lester, Dean M.; Wallace, Ingvar; Starrett, W. David; Marshall, David W.

2002-07-01

183

Accelerated Aging of Polymer Composite Bridge Materials  

SciTech Connect

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

J. G. Rodriguez; L. G. Blackwood; L. L. Torres; N. M. Carlson; T. S. Yoder

1999-03-01

184

Microfluidic Synthesis of Composite Cross-Gradient Materials for Investigating Cell-Biomaterial Interactions  

PubMed Central

Combinatorial material synthesis is a powerful approach for creating composite material libraries for the high-throughput screening of cell–material interactions. Although current combinatorial screening platforms have been tremendously successful in identifying target (termed “hit”) materials from composite material libraries, new material synthesis approaches are needed to further optimize the concentrations and blending ratios of the component materials. Here we employed a microfluidic platform to rapidly synthesize composite materials containing cross-gradients of gelatin and chitosan for investigating cell–biomaterial interactions. The microfluidic synthesis of the cross-gradient was optimized experimentally and theoretically to produce quantitatively controllable variations in the concentrations and blending ratios of the two components. The anisotropic chemical compositions of the gelatin/chitosan cross-gradients were characterized by Fourier transform infrared spectrometry and X-ray photoelectron spectrometry. The three-dimensional (3D) porous gelatin/chitosan cross-gradient materials were shown to regulate the cellular morphology and proliferation of smooth muscle cells (SMCs) in a gradient-dependent manner. We envision that our microfluidic cross-gradient platform may accelerate the material development processes involved in a wide range of biomedical applications. PMID:20721897

He, Jiankang; Du, Yanan; Guo, Yuqi; Hancock, Matthew J.; Wang, Ben; Shin, Hyeongho; Wu, Jinhui; Li, Dichen; Khademhosseini, Ali

2010-01-01

185

Composite materials for precision space reflector panels  

NASA Technical Reports Server (NTRS)

One of the critical technology needs of large precision reflectors for future astrophysical and optical communications satellites lies in the area of structural materials. Results from a materials research and development program at NASA Langley Research Center to provide materials for these reflector applications are discussed. Advanced materials that meet the reflector panel requirements are identified, and thermal, mechanical and durability properties of candidate materials after exposure to simulated space environments are compared. A parabolic, graphite-phenolic honeycomb composite panel having a surface accuracy of 70.8 microinches rms and an areal weight of 1.17 lbm/sq ft was fabricated with T50/ERL1962 facesheets, a PAEI thermoplastic surface film, and Al and SiO(x) coatings.

Tompkins, Stephen S.; Funk, Joan G.; Bowles, David E.; Towell, Timothy W.; Connell, John W.

1992-01-01

186

Bulk anisotropic composite rare earth magnets S. Bauser, A. Higgins, C. Chen,b  

E-print Network

­Fe­Ga­B powder with an -Fe or Fe­Co powder followed by hot compaction at 600­700 °C and hot deformation die. INTRODUCTION It is well known that in order to obtain an anisotropic Nd­Fe­B magnet by hot deformation were made by hot compacting and hot deform- ing two Nd­Fe­B powders, one with a Nd content slightly

Laughlin, David E.

187

Composite strings in (2+1)-dimensional anisotropic weakly coupled Yang-Mills theory  

SciTech Connect

The small-scale structure of a string connecting a pair of static sources is explored for the weakly coupled anisotropic SU(2) Yang-Mills theory in (2+1) dimensions. A crucial ingredient in the formulation of the string Hamiltonian is the phenomenon of color smearing of the string constituents. The quark-antiquark potential is determined. We close with some discussion of the standard, fully Lorentz-invariant Yang-Mills theory.

Orland, Peter [Isaac Newton Institute for the Mathematical Sciences, 20 Clarkson Road, Cambridge, CB3 OEH (United Kingdom); Niels Bohr Institute, Niels Bohr International Academy, Blegdamsvej 17, DK-2100, Copenhagen O (Denmark); Physics Program, Graduate School and University Center, City University of New York, 365 Fifth Avenue, New York, New York 10016 (United States); Department of Natural Sciences, Baruch College, City University of New York, 17 Lexington Avenue, New York, New York 10010 (United States)

2008-01-15

188

Compression Testing of Textile Composite Materials  

NASA Technical Reports Server (NTRS)

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.

Masters, John E.

1996-01-01

189

An anisotropic model of damage and frictional sliding for brittle materials  

Microsoft Academic Search

The paper provides important developments for the model of anisotropic damage by mesocrack growth, accounting for unilateral behaviour relative to crack closure (Dragon and Halm, 1996, Halm and Dragon, 1996). Frictional sliding of closed microcrack systems is introduced here as an additional dissipative mechanism, which is considered to be coupled with the primary dissipative mechanism (damage by microcrack growth). Indeed,

D. Halm; A. Dragon

1998-01-01

190

Journal of Magnetism and Magnetic Materials 248 (2002) 164180 General spin wave instability theory for anisotropic  

E-print Network

for anisotropic ferromagnetic insulators at high microwave power levels A.V. Nazarov*, C.E. Patton, R.G. Cox, L with a general polarization for the microwave field was considered by Yakovlev [4], Green et al. [5], and Patton by Haubenreisser et al. [8,9], Petra- kovskii [10], Yakovlev [11], and Patton [12]. Refs. [8,10] were for parallel

Patton, Carl

191

NUMERICAL SIMULATION OF HEAT TRANSFER IN MATERIALS WITH ANISOTROPIC THERMAL CONDUCTIVITY  

E-print Network

crystal seed. 4: Gas enclosure. 5: SiC powder source. 6: Quartz. = 6 m=1 m. Figure 1: Axisymmetric domain hole (for cooling and measurements). 1: Insulation (often anisotropic). 2: Graphite crucible. 3: SiC representing a growth apparatus used in silicon carbide single crystal growth by physical vapor transport (PVT

192

Theory of indentation on multiferroic composite materials  

NASA Astrophysics Data System (ADS)

This article presents a general theory on indentation over a multiferroic composite half-space. The material is transversely isotropic and magneto-electro-elastic with its axis of symmetry normal to the surface of the half-space. Based on the corresponding half-space Green's functions to point sources applied on the surface, explicit expressions for the generalized pressure vs. indentation depth are derived for the first time for the three common indenters (flat-ended, conical, and spherical punches). The important multiphase coupling issue is discussed in detail, with the weak and strong coupling being correctly revisited. The derived analytical solutions of indentation will not only serve as benchmarks for future numerical studies of multiphase composites, but also have important applications to experimental test and characterization of multiphase materials, in particular, of multiferroic properties.

Chen, Weiqiu; Pan, Ernian; Wang, Huiming; Zhang, Chuanzeng

2010-10-01

193

Advanced Technology Composite Fuselage - Materials and Processes  

NASA Technical Reports Server (NTRS)

The goal of Boeing's Advanced Technology Composite Aircraft Structures (ATCAS) program was to develop the technology required for cost and weight efficient use of composite materials in transport fuselage structure. This contractor report describes results of material and process selection, development, and characterization activities. Carbon fiber reinforced epoxy was chosen for fuselage skins and stiffening elements and for passenger and cargo floor structures. The automated fiber placement (AFP) process was selected for fabrication of monolithic and sandwich skin panels. Circumferential frames and window frames were braided and resin transfer molded (RTM'd). Pultrusion was selected for fabrication of floor beams and constant section stiffening elements. Drape forming was chosen for stringers and other stiffening elements. Significant development efforts were expended on the AFP, braiding, and RTM processes. Sandwich core materials and core edge close-out design concepts were evaluated. Autoclave cure processes were developed for stiffened skin and sandwich structures. The stiffness, strength, notch sensitivity, and bearing/bypass properties of fiber-placed skin materials and braided/RTM'd circumferential frame materials were characterized. The strength and durability of cocured and cobonded joints were evaluated. Impact damage resistance of stiffened skin and sandwich structures typical of fuselage panels was investigated. Fluid penetration and migration mechanisms for sandwich panels were studied.

Scholz, D. B.; Dost, E. F.; Flynn, B. W.; Ilcewicz, L. B.; Nelson, K. M.; Sawicki, A. J.; Walker, T. H.; Lakes, R. S.

1997-01-01

194

Thermoplastic constructional composite material for radiation protection  

Microsoft Academic Search

The possibility of synthesis of filled metallooligomer powders on the basis of lead ethylsiliconate is considered by a method\\u000a of heterophase interaction, in siloksan chains of which chemically bound lead with a high concentration of atoms of lead is\\u000a contained. Thermoplastic constructional composite materials for radiation protection on the basis of a polystyrene polymeric\\u000a matrix modified by waterproof oligomer lead

V. I. Pavlenko; I. S. Epifanovskii; R. N. Yastrebinskii; O. V. Kuprieva

2011-01-01

195

The physical properties of composite materials  

Microsoft Academic Search

In this review, the physical properties of composite materials are discussed; however, discussion of the mechanical properties\\u000a has been excluded except when necessary for the consideration of properties such as thermal expansion or swelling and shrinkage.\\u000a One of the main aims in the review has been to show how the theoretical and experimental information that is already available\\u000a may be

D. K. Hale

1976-01-01

196

Alkali metal protective garment and composite material  

DOEpatents

A protective garment and composite material providing satisfactory heat resistance and physical protection for articles and personnel exposed to hot molten alkali metals, such as sodium. Physical protection is provided by a continuous layer of nickel foil. Heat resistance is provided by an underlying backing layer of thermal insulation. Overlying outer layers of fireproof woven ceramic fibers are used to protect the foil during storage and handling.

Ballif, III, John L. (Salt Lake City, UT); Yuan, Wei W. (Seattle, WA)

1980-01-01

197

Stresses around fasteners in composite materials  

NASA Astrophysics Data System (ADS)

Stress distributions around fasteners in composite materials were experimentally and theoretically studied. The fasteners were cheesehead and countersunk bolts. It was found that samples fastened with countersunk bolts tended to fatigue more rapidly than specimens with cheesehead bolts. Fewer fatigue cycles were needed for damage to initiate in plates with countersunk bolts, and higher direct stress and shear stress values are predicted to occur in plates with countersunk bolts. The principal failure mechanism was delamination, probably due to high direct and shear stresses.

Benchekchou, B.; White, R. G.

1993-04-01

198

ACEE Composite Structures Technology: Review of selected NASA research on composite materials and structures  

NASA Technical Reports Server (NTRS)

The NASA Aircraft Energy Efficiency (ACEE) Composite Primary Aircraft Structures Program was designed to develop technology for advanced composites in commercial aircraft. Research on composite materials, aircraft structures, and aircraft design is presented herein. The following parameters of composite materials were addressed: residual strength, damage tolerance, toughness, tensile strength, impact resistance, buckling, and noise transmission within composite materials structures.

1984-01-01

199

Fiber Reinforced Composite Materials Used for Tankage  

NASA Technical Reports Server (NTRS)

The Nonmetallic Materials and Processes Group is presently working on several projects to optimize cost while providing effect materials for the space program. One factor that must be considered is that these materials must meet certain weight requirements. Composites contribute greatly to this effort. Through the use of composites the cost of launching payloads into orbit will be reduced to one-tenth of the current cost. This research project involved composites used for aluminum pressure vessels. These tanks are used to store cryogenic liquids during flight. The tanks need some type of reinforcement. Steel was considered, but added too much weight. As a result, fiber was chosen. Presently, only carbon fibers with epoxy resin are wrapped around the vessels as a primary source of reinforcement. Carbon fibers are lightweight, yet high strength. The carbon fibers are wet wound onto the pressure vessels. This was done using the ENTEC Filament Winding Machine. It was thought that an additional layer of fiber would aid in reinforcement as well as containment and impact reduction. Kevlar was selected because it is light weight, but five times stronger that steel. This is the same fiber that is used to make bullet-proof vests trampolines, and tennis rackets.

Cunningham, Christy

2005-01-01

200

Impact of solids on composite materials  

NASA Technical Reports Server (NTRS)

The failure modes of composite materials as a result of low velocity impact were investigated by simulating the impact with a finite element analysis. An important facet of the project is the modeling of the impact of a solid onto cylindrical shells composed of composite materials. The model under development will simulate the delamination sustained when a composite material encounters impact from another rigid body. The computer equipment was installed, the computer network tested, and a finite element method model was developed to compare results with known experimental data. The model simulated the impact of a steel rod onto a rotating shaft. Pre-processing programs (GMESH and TANVEL) were developed to generate node and element data for the input into the three dimensional, dynamic finite element analysis code (DYNA3D). The finite element mesh was configured with a fine mesh near the impact zone and a coarser mesh for the impacting rod and the regions surrounding the impacting zone. For the computer simulation, five impacting loads were used to determine the time history of the stresses, the scribed surface areas, and the amount of ridging. The processing time of the computer codes amounted from 1 to 4 days. The calculated surface area were within 6-12 percent, relative error when compated to the actual scratch area.

Bronson, Arturo; Maldonado, Jerry; Chern, Tzong; Martinez, Francisco; Mccord-Medrano, Johnnie; Roschke, Paul N.

1987-01-01

201

Flexible Composite-Material Pressure Vessel  

NASA Technical Reports Server (NTRS)

A proposed lightweight pressure vessel would be made of a composite of high-tenacity continuous fibers and a flexible matrix material. The flexibility of this pressure vessel would render it (1) compactly stowable for transport and (2) more able to withstand impacts, relative to lightweight pressure vessels made of rigid composite materials. The vessel would be designed as a structural shell wherein the fibers would be predominantly bias-oriented, the orientations being optimized to make the fibers bear the tensile loads in the structure. Such efficient use of tension-bearing fibers would minimize or eliminate the need for stitching and fill (weft) fibers for strength. The vessel could be fabricated by techniques adapted from filament winding of prior composite-material vessels, perhaps in conjunction with the use of dry film adhesives. In addition to the high-bias main-body substructure described above, the vessel would include a low-bias end substructure to complete coverage and react peak loads. Axial elements would be overlaid to contain damage and to control fiber orientation around side openings. Fiber ring structures would be used as interfaces for connection to ancillary hardware.

Brown, Glen; Haggard, Roy; Harris, Paul A.

2003-01-01

202

Putting it Together: The Science and Technology of Composite Materials  

NSDL National Science Digital Library

Composite materials are light, strong, corrosion-resistant composites of two or more materials used commonly in manufacturing. This recent report is from the Australian Academy of Science with support from The Cooperative Research Centre for Advanced Composite Structures, Ltd. and the Commonwealth Department of Industry, Science and Resources. It gives information on the history, manufacturing techniques, and efficiency of composite materials. A glossary, reference list, and links to educational sites as well as other composite materials sites are also featured.

2000-01-01

203

The right circular polarized waves in the three-dimensional anisotropic dispersive photonic crystals consisting of the magnetized plasma and uniaxial material as the Faraday effects considered  

NASA Astrophysics Data System (ADS)

In this paper, the properties of the right circular polarized (RCP) waves in the three-dimensional (3D) dispersive photonic crystals (PCs) consisting of the magnetized plasma and uniaxial material with face-centered-cubic (fcc) lattices are theoretically investigated by the plane wave expansion method, which the homogeneous anisotropic dielectric spheres (the uniaxial material) immersed in the magnetized plasma background, as the Faraday effects of magnetized plasma are considered (the incidence electromagnetic wave vector is parallel to the external magnetic field at any time). The equations for calculating the anisotropic photonic band gaps (PBGs) for the RCP waves in the first irreducible Brillouin zone are theoretically deduced. The anisotropic PBGs and a flatbands region can be obtained. The effects of the ordinary-refractive index, extraordinary-refractive index, anisotropic dielectric filling factor, plasma frequency, and plasma cyclotron frequency (the external magnetic field) on the properties of first two anisotropic PBGs for the RCP waves are investigated in detail, respectively. The numerical results show that the anisotropy can open partial band gaps in fcc lattices at U and W points, and the complete PBGs for the RCP waves can be achieved compared to the conventional 3D dispersive PCs composed of the magnetized plasma and isotropic material. It is also shown that the first two anisotropic PBGs can be tuned by those parameters as mentioned above. Those PBGs can be enlarged by introducing the uniaxial material into such 3D PCs as the Faraday effects are considered.

Zhang, Hai-Feng; Liu, Shao-Bin; Zhen, Jian-Ping; Tang, Yi-Jun

2014-03-01

204

Inverse relationships for reflection diagnostics of uniaxially anisotropic nanoscale films on isotropic materials.  

PubMed

The possibilities of determining the parameters of uniaxially anisotropic ultrathin nonabsorbing dielectric films on absorbing or transparent isotropic substrates by surface differential reflectance measurements are analyzed. The analysis is based on analytical reflection formulas obtained in the framework of a long-wavelength approximation. It is shown that, in the case of transparent substrates, it is always possible to determine the thickness of a uniaxially ultrathin film and its four parameters of anisotropy (optical constants n(o) and n(e) and angles ? and ?) simultaneously. However, for such films on absorbing substrates, it is possible to decouple the thickness and optical constants by differential reflectance measurements only if ??0. The accuracy of the obtained analytic formulas for determining the parameters of ultrathin films is estimated by computer simulations where the reflection problem was solved numerically on the basis of the rigorous electromagnetic theory for anisotropic layered systems. PMID:21673783

Adamson, Peep

2011-06-10

205

Dielectric response of graded spherical particles of anisotropic materials Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong  

E-print Network

occurs naturally due to the presence of gradation, like in functionally graded materials or graded of Physics. DOI: 10.1063/1.1633648 I. INTRODUCTION The concept of functionally graded materials FGM , whichDielectric response of graded spherical particles of anisotropic materials L. Dong Department

Huang, Ji-Ping

206

Composite material systems for hydrogen management  

NASA Technical Reports Server (NTRS)

The task of managing hydrogen entry into elevated temperature structural materials employed in turbomachinery is a critical engineering area for propulsion systems employing hydrogen or decomposable hydrocarbons as fuel. Extant structural materials, such as the Inconel series, are embrittled by the ingress of hydrogen in service, leading to a loss of endurance and general deterioration of load-bearing dependability. Although the development of hydrogen-insensitive material systems is an obvious engineering option, to date insensitive systems cannot meet the time-temperature-loading service extremes encountered. A short-term approach that is both feasible and technologically sound is the development and employment of hydrogen barrier coatings. The present project is concerned with developing, analyzing, and physically testing laminate composite hydrogen barrier systems, employing Inconel 718 as the structural material to be protected. Barrier systems will include all metallic, metallic-to-ceramic, and, eventually, metallic/ceramic composites as the lamellae. Since space propulsion implies repetitive engine firings without earth-based inspection and repair, coating durability will be closely examined, and testing regimes will include repetitive thermal cycling to simulate damage accumulation. The target accomplishments include: generation of actual hydrogen permeation data for metallic, ceramic-metallic, and hybrid metallic/ceramic composition barrier systems, practically none of which is currently extant; definition of physical damage modes imported to barrier systems due to thermal cycling, both transient temperature profiles and steady-state thermal mismatch stress states being examined as sources of damage; and computational models that incorporate general laminate schemes as described above, including manufacturing realities such as porosity, and whatever defects are introduced through service and characterized during the experimental programs.

Pangborn, R. N.; Queeney, R. A.

1991-01-01

207

BIEM for 2D steady-state problems in cracked anisotropic materials  

Microsoft Academic Search

The two-dimensional ‘in-plane’ time-harmonic elasto-dynamic problem for anisotropic cracked solid is studied. The non-hypersingular traction boundary integral equation method (BIEM) is used in conjunction with closed form frequency dependent fundamental solution, obtained by Radon transform. Accuracy and convergence of the numerical solution for stress intensity factor (SIF) is studied by comparison with existing solutions in isotropic, transversely-isotropic and orthotropic cases.

P. Dineva; T. Rangelov; D. Gross

2005-01-01

208

Energy absorbing hybrid nano-composite materials  

NASA Astrophysics Data System (ADS)

Base Epon 862 resin was enhanced with two types of fillers, graphitized carbon nanofiber (CNF) and silicon dioxide (SiO2) particles. The effect of both filler type and filler loading were investigated with respect to the energy absorbing capacity as well as the thermal stability of the hybrid composite material, measured in terms of the coefficient of thermal expansion (CTE). As well the composites with combinations of the fillers were evaluated for both enhanced damping and thermal stability, making it suitable for structural materials that need multiple functions. The composites were evaluated with dynamic mechanical analysis (DMA) to evaluate viscoelastic response, and using strain gauges to measure thermal strain responses. It has been found that the addition of 3wt% SiO2 along with 3wt% CNF can improve damping loss factors by up to 26% while at the same time improving thermal stability with reductions in CTE of up to 16.5%. Furthermore, these fillers loadings were successfully dispersed as received by mechanical mixing technique, making fabrication more economically suited to engineering applications.

Jang, Jae-Soon; Varischetti, Joshua; Lee, Gyo Woo; Suhr, Jonghwan

2009-03-01

209

Composite materials for thermal energy storage  

DOEpatents

The present invention discloses composite material for thermal energy storage based upon polyhydric alcohols, such as pentaerythritol, trimethylol ethane (also known as pentaglycerine), neopentyl glycol and related compounds including trimethylol propane, monoaminopentaerythritol, diamino-pentaerythritol and tris(hydroxymethyl)acetic acid, separately or in combinations, which provide reversible heat storage through crystalline phase transformations. These phase change materials do not become liquid during use and are in contact with at least one material selected from the group consisting of metals, carbon siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, porous rock, and mixtures thereof. Particulate additions, such as aluminum or graphite powders, as well as metal and carbon fibers can also be incorporated therein. Particulate and/or fibrous additions can be introduced into molten phase change materials which can then be cast into various shapes. After the phase change materials have solidified, the additions will remain dispersed throughout the matrix of the cast solid. The polyol is in contact with at least one material selected from the group consisting of metals, carbon siliceous, plastic, cellulosic, natural fiber, artificial fiber, concrete, gypsum, and mixtures thereof.

Benson, David K. (Golden, CO); Burrows, Richard W. (Conifer, CO); Shinton, Yvonne D. (Northglenn, CO)

1986-01-01

210

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

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,…

Massuda, Rachel

211

Color masterbatch resin composition for packaging material for photographic photosensitive material and packaging material  

US Patent & Trademark Office Database

A color masterbach resin composition for a packaging material for a photographic photosensitive material which does not adversely affect photographic properties of the photographic photosensitive material, comprising a light-shielding material in a concentration thrice as much as or more that of the packaging material for a photographic photosensitive material, and a thermoplastic resin of which 50 wt. % or more is the same type as a thermoplastic resin occupying 50 wt. % or more of the total thermoplastic resin composing the packaging material for a photographic photosensitive material, production thereof, a packaging material for a photographic photosensitive material formed of a color masterbatch resin composition, and production thereof. In the color masterbatch resin composition and the packaging material for a photographic photosensitive material of the invention, light-shielding material is dispersed uniformly by employing a special resin composition, and thereby, adverse affects upon photographic hpotosensitive materials are prevented, and favorable appearance can be ensured. Moreover, fog with time, abnormal sensitivity, abrasion, pressure marks, etc. can be prevented.

1998-09-29

212

Simulation of tensile strength of anisotropic fibre-reinforced composites at low temperature  

NASA Astrophysics Data System (ADS)

This article presents a simulation scheme to predict the effect of fibre anisotropy on composite tensile failure strength at room and low temperatures. The simulation model combines the shear lag equation with the chain of bundles probability model to describe the composite failure behaviour. The effect of fibre anisotropy on thermal stresses developed in composite constituents due to cooling to low temperatures is considered. The failure strength of composites composed of fibres with different degrees of anisotropy is obtained and comparisons are made with experiments. Simulated results for E-glass-, graphite- and Kevlar-epoxy type composites showed close agreement with the experiments.

Abdelmohsen, H. H.

213

Composite Materials Instruction at the United States Naval Academy.  

National Technical Information Service (NTIS)

Composite materials are widely becoming the material of choice for many structural and nonstructural applications. The aircraft industry for example, has used composites for wing skins and other control surfaces that provide savings in fuel consumption an...

J. O. Barton, P. H. Miller

2003-01-01

214

Determination of moisture effects on impact properties of composite materials  

Microsoft Academic Search

Many applications of structural materials involving composites include impact or dynamic loading in a humid environment. Composite materials are known to degrade when subjected to humid conditions, and therefore the humidity confounds the difficulty of determining the high strain rate behavior of composites. Several researchers have found that water absorption by composites causes degradation of matrix dominated quasi-static properties. However,

E. Woldesenbet; N. Gupta; J. R. Vinson

2002-01-01

215

Use of advanced composite materials for innovative building design solutions/  

E-print Network

Advanced composite materials become popular in construction industry for the innovative building design solutions including strengthening and retrofitting of existing structures. The interface between different materials ...

Lau, Tak-bun, Denvid

2009-01-01

216

Bending and stretching finite element analysis of anisotropic viscoelastic composite plates  

NASA Technical Reports Server (NTRS)

Finite element algorithms have been developed to analyze linear anisotropic viscoelastic plates, with or without holes, subjected to mechanical (bending, tension), temperature, and hygrothermal loadings. The analysis is based on Laplace transforms rather than direct time integrations in order to improve the accuracy of the results and save on extensive computational time and storage. The time dependent displacement fields in the transverse direction for the cross ply and angle ply laminates are calculated and the stacking sequence effects of the laminates are discussed in detail. Creep responses for the plates with or without a circular hole are also studied. The numerical results compare favorably with analytical solutions, i.e. within 1.8 percent for bending and 10(exp -3) 3 percent for tension. The tension results of the present method are compared with those using the direct time integration scheme.

Hilton, Harry H.; Yi, Sung

1990-01-01

217

Filler Materials for Polyphenylenesulphide Composite Coatings: Preprint  

SciTech Connect

Researchers at Brookhaven National Laboratory and the National Renewable Energy Laboratory have tested polymer-based coating systems to reduce the capital equipment and maintenance costs of heat exchangers in corrosive and fouling geothermal environments. These coating systems act as barriers to corrosion to protect low-cost carbon steel tubing; they are formulated to resist wear from hydroblasting and to have high thermal conductivity. Recently, new filler materials have been developed for coating systems that use polyphenylenesulphide as a matrix. These materials include boehmite crystals (orthorhombic aluminum hydroxide, which is grown in situ as a product of reaction with the geothermal fluid), which enhance wear and corrosion resistance, and carbon fibers, which improve mechanical, thermal, and corrosion-resistance properties of the composite.

Sugama, T.; Gawlik, K.

2001-07-17

218

Composite materials flown on the Long Duration Exposure Facility  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

219

Characterization of the pneumatic behavior of carbon\\/epoxy composites  

Microsoft Academic Search

The anisotropic nature of composite materials and environmental effects always make the behavior of composite materials more complicated than that of conventional materials. Applications of composite materials, including containers, boats, aircraft and aerospace structures, etc, must take into consideration several important environmental effects like hygric and thermal effects. A composite engineer should be familiar with the hygrothermal behavior of composite

Cho-Liang Tsai; Yun Du

2001-01-01

220

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

NASA Astrophysics Data System (ADS)

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.

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

2011-06-01

221

Viscoelastic behavior of fiber-reinforced composite materials undergoing cure  

E-print Network

A viscoelastic material model has been proposed to characterize the curing and thermal effects on the viscoelastic material properties of both the matrix material and the composite lamina. Micromechanics simulations are used to generate...

Wang, Kai

2012-06-07

222

The anisotropic photonic band gaps in three-dimensional photonic crystals with high-symmetry lattices composed of metamaterials and uniaxial materials  

NASA Astrophysics Data System (ADS)

In this paper, the properties of anisotropic photonic band gaps (PBGs) for three-dimensional (3D) photonic crystals (PCs) composed of tellurium (Te) spheres (the uniaxial materials) in homogeneous single-negative metamaterials (epsilon-negative materials) background with high-symmetry (simple-cubic) lattices are theoretically investigated based on the plane wave expansion method. The equations for calculating the anisotropic PBGs in the first irreducible Brillouin zone are theoretically deduced. The influences of the ordinary-refractive index, extraordinary-refractive index, filling factor of dielectric, the electronic plasma frequency, the dielectric constant of epsilon-negative materials on the anisotropic PBGs are also studied in detail, respectively, and some corresponding physical explanations are also given. The numerical results show that the anisotropy can open partial band gaps in simple-cubic lattices and the complete PBGs also can be achieved compared to such 3D PCs doped by the conventional isotropic materials. It also is shown that the anisotropic PBGs can be manipulated by the parameters as mentioned above. Introducing the uniaxial materials into 3D dielectric-epsilon-negative materials PCs can enlarge the PBGs, and also provide a way to obtain the complete PBGs as such kind of 3D PCs with high-symmetry lattices.

Zhang, Hai-Feng; Liu, Shao-Bin

2014-03-01

223

Composition and method for removing photoresist materials from electronic components  

DOEpatents

Composition and method for removing photoresist materials from electronic components. The composition is a mixture of at least one dense phase fluid and at least one dense phase fluid modifier. The method includes exposing a substrate to at least one pulse of the composition in a supercritical state to remove photoresist materials from the substrate.

Davenhall, Leisa B. (Santa Fe, NM); Rubin, James B. (Los Alamos, NM); Taylor, Craig M. V. (Jemez Springs, NM)

2008-06-03

224

Microrobotics Using Composite Materials: The Micromechanical Flying Insect Thorax  

E-print Network

Microrobotics Using Composite Materials: The Micromechanical Flying Insect Thorax R. J. Wood S, srinath, manas, ronf}@robotics.eecs.berkeley.edu Abstract The use of high performance composite materials, and higher stiffness to weight ratios than most metals. Composite structures yield remarkable improvements

Fearing, Ron

225

Composite materials: Tomorrow for the day after tomorrow  

NASA Technical Reports Server (NTRS)

A description is given of the history of the use of composite materials in the aerospace industry. Research programs underway to obtain exact data on the behavior of composite materials over time are discussed. It is concluded that metal composites have not yet replaced metals, but that that this may be a future possibility.

Condom, P.

1982-01-01

226

NDE Elastic Properties of Fiber-Reinforced Composite Materials  

NASA Technical Reports Server (NTRS)

Fiber-reinforced composites are increasingly replacing metallic alloys as structural materials for primary components of fracture-critical structures. This trend is a result of the growing understanding of material behavior and recognition of the desirable properties of composites. A research program was conducted on NDE methods for determining the elastic properties of composites.

Bar-Cohen, Y.

1995-01-01

227

AN ANISOTROPIC NANOFIBER/MICROSPHERE COMPOSITE WITH CONTROLLED RELEASE OF BIOMOLECULES FOR FIBROUS TISSUE ENGINEERING  

PubMed Central

Aligned nanofibrous scaffolds can recapitulate the structural hierarchy of fiber-reinforced tissues of the musculoskeletal system. While these electrospun fibrous scaffolds provide physical cues that can direct tissue formation when seeded with cells, the ability to chemically guide a population of cells, without disrupting scaffold mechanical properties, would improve the maturation of such constructs and add additional functionality to the system both in vitro and in vivo. In this study, we developed a fabrication technique to entrap drug-delivering microspheres within nanofibrous scaffolds. We hypothesized that entrapping microspheres between fibers would have a less adverse impact on mechanical properties than placing microspheres within the fibers themselves, and that the composite would exhibit sustained release of multiple model compounds. Our results show that microspheres ranging from 10~20 microns in diameter could be electrospun in a dose-dependent manner to form nanofibrous composites. When delivered in a sacrificial PEO fiber population, microspheres remained securely entrapped between slow-degrading PCL fibers after removal of the sacrificial delivery component. Stiffness and modulus of the composite decreased with increasing microsphere density for composites in which microspheres were entrapped within each fiber, while stiffness did not change when microspheres were entrapped between fibers. The release profiles of the composite structures were similar to free microspheres, with an initial burst release followed by a sustained release of the model molecules over 4 weeks. Further, multiple model molecules were released from a single scaffold composite, demonstrating the capacity for multi-factor controlled release ideal for complex growth factor delivery from these structures. PMID:20149432

Ionescu, Lara C.; Lee, Gregory C.; Sennett, Brian J.; Burdick, Jason A.; Mauck, Robert L.

2010-01-01

228

Stiffness Transfer Matrix Method (STMM) for stable dispersion curves solution in anisotropic composites  

NASA Astrophysics Data System (ADS)

This paper discusses combined transfer matrix method (TMM) with stiffness matrix method (SMM) for obtaining a stable solution for dispersion curves of Lamb wave propagation in non-isotropic layers. TMM developed by Thomson and Haskell experiences numerical deficiency at high frequency thickness simulations. SMM was proposed by different researchers to solve the instability issue of TMM. This study shows that stable SMM is good at high frequencies, and TMM needs to be combined with SMM to obtain stable and robust behavior over the frequency range. Numerical simulations of dispersion curves are presented for wave propagation in orthotropic unidirectional fiber composites and cross ply composites. The paper ends with conclusions and future work.

Kamal, Ayman; Giurgiutiu, Victor

2014-03-01

229

Spark-plasma-sintering magnetic field assisted compaction of Co80Ni20 nanowires for anisotropic ferromagnetic bulk materials  

NASA Astrophysics Data System (ADS)

We developed a two-step process showing the way for sintering anisotropic nanostructured bulk ferromagnetic materials. A new reactor has been optimized allowing the synthesis of several grams per batch of nanopowders via a polyol soft chemistry route. The feasibility of the scale-up has been successfully demonstrated for Co80Ni20 nanowires and a massic yield of ˜97% was obtained. The thus obtained nanowires show an average diameter of ˜6 nm and a length of ˜270 nm. A new bottom-up strategy allowed us to compact the powder into a bulk nanostructured system. We used a spark-plasma-sintering technique under uniaxial compression and low temperature assisted by a permanent magnetic field of 1 T. A macroscopic pellet of partially aligned nanowire arrays has been easily obtained. This showed optimized coercive properties along the direction of the magnetic field applied during compaction (i.e., the nanowires' direction).

Ouar, Nassima; Schoenstein, Frédéric; Mercone, Silvana; Farhat, Samir; Villeroy, Benjamin; Leridon, Brigitte; Jouini, Noureddine

2013-10-01

230

Multi-scale Modeling for Piezoelectric Composite Materials  

E-print Network

In this paper, we focus on multi-scale modeling and simulation of piezoelectric composite materials. A multi-scale model for piezoelectric composite materials under the framework of Heterogeneous Multi-scale Method(HMM) is proposed. For materials with periodic microstructure, macroscopic model is derived from microscopic model of piezoelectric composite material by asymptotic expansion. Convergence analysis under the framework of homogenization theory is carried out. Moreover, error estimate between HMM solutions and homogenization solutions is derived. A 3-D numerical example of 1-3 type piezoelectric composite materials is employed to verify the error estimate.

Qian Zhang; Xingye Yue

2014-02-02

231

Tailoring The Microwave Permittivity And Permeability Of Composite Materials  

E-print Network

selective surfaces such as bandpass and lowpass filters as well as radar absorbing materials1 Tailoring The Microwave Permittivity And Permeability Of Composite Materials Kenneth M. Bober/Lowell, Lowell, MA 01854 ABSTRACT The microwave permittivity( r ) and permeability( r ) of composite materials

Massachusetts at Lowell, University of

232

Using of Composite Material in Wind Turbine Blades  

Microsoft Academic Search

The turbines manufactured from the mid 1980s until the late 1990s were mainly constructed using standard components. After that period, special components started being designed and manufactured for turbine use only. One of the best solutions is using composite materials in wind turbine. Most composites are made up of just two materials. One material (the matrix or binder) binds together

Bulent Eker; Aysegul Akdogan; Ali Vardar

2006-01-01

233

Oxygen isotope composition of trinitite postdetonation materials.  

PubMed

Trinitite is the melt glass produced subsequent the first nuclear bomb test conducted on July 16, 1945, at White Sands Range (Alamagordo, NM). The geological background of the latter consists of arkosic sand that was fused with radioactive debris and anthropogenic materials at ground zero subsequent detonation of the device. Postdetonation materials from historic nuclear weapon test sites provide ideal samples for development of novel forensic methods for attribution and studying the chemical/isotopic effects of the explosion on the natural geological environment. In particular, the latter effects can be evaluated relative to their spatial distribution from ground zero. We report here ?(18)O(‰) values for nonmelted, precursor minerals phases (quartz, feldspar, calcite), "feldspathic-rich" glass, "average" melt glass, and bulk (natural) unmelted sand from the Trinity site. Prior to oxygen isotope analysis, grains/crystals were examined using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) to determine their corresponding major element composition. ?(18)O values for bulk trinitite samples exhibit a large range (11.2-15.5‰) and do not correlate with activity levels for activation product (152)Eu; the latter levels are a function of their spatial distribution relative to ground zero. Therefore, the slow neutron flux associated with the nuclear explosion did not perturb the (18)O/(16)O isotope systematics. The oxygen isotope values do correlate with the abundances of major elements derived from precursor minerals present within the arkosic sand. Hence, the O isotope ratios documented here for trinitite melt glass can be attributed to a mixture of the respective signatures for precursor minerals at the Trinity site prior to the nuclear explosion. PMID:24304329

Koeman, Elizabeth C; Simonetti, Antonio; Chen, Wei; Burns, Peter C

2013-12-17

234

Frequency dependent directivity of guided waves excited by circular transducers in anisotropic composite plates.  

PubMed

Lamb wave propagation in fiber-reinforced composite plates is featured by a pronounced directivity of wave energy transfer along the fibers from a point surface source. In the case of non-point (sized) source, the main lobe of radiation diagram may turn with frequency up to the orthogonal to the fibers direction. This effect has been theoretically studied and physically explained in the context of semi-analytical integral-equation based mathematical model. The present paper gives its experimental verification. PMID:22894309

Glushkov, Evgeny; Glushkova, Natalia; Eremin, Artem; Lammering, Rolf; Neumann, Mirko

2012-08-01

235

Material, process, and product design of thermoplastic composite materials  

NASA Astrophysics Data System (ADS)

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.

Dai, Heming

236

A spectrally formulated plate element for wave propagation analysis in anisotropic material  

Microsoft Academic Search

A new spectrally formulated plate element is developed to study wave propagation in composite structures. The element is based on the classical lamination plate theory. Recently developed method based on singular value decomposition (SVD) is used in the element formulation. Along with this, a new strategy based on the method of solving polynomial eigenvalue problem (PEP) is proposed in this

A. Chakraborty; S. Gopalakrishnan

2005-01-01

237

Some functional properties of composite material based on scrap tires  

NASA Astrophysics Data System (ADS)

The utilization of scrap tires still obtains a remarkable importance from the aspect of unloading the environment from non-degradable waste [1]. One of the most prospective ways for scrap tires reuse is a production of composite materials [2] This research must be considered as a continuation of previous investigations [3, 4]. It is devoted to the clarification of some functional properties, which are considered important for the view of practical applications, of the composite material. Some functional properties of the material were investigated, for instance, the compressive stress at different extent of deformation of sample (till 67% of initial thickness) (LVS EN 826) [5] and the resistance to UV radiation (modified method based on LVS EN 14836) [6]. Experiments were realized on the purposefully selected samples. The results were evaluated in the correlation with potential changes of Shore C hardness (Shore scale, ISO 7619-1, ISO 868) [7, 8]. The results showed noticeable resistance of the composite material against the mechanical influence and ultraviolet (UV) radiation. The correlation with the composition of the material, activity of binder, definite technological parameters, and the conditions supported during the production, were determined. It was estimated that selected properties and characteristics of the material are strongly dependent from the composition and technological parameters used in production of the composite material, and from the size of rubber crumb. Obtained results show possibility to attain desirable changes in the composite material properties by changing both the composition and technological parameters of examined material.

Plesuma, Renate; Malers, Laimonis

2013-09-01

238

Strongly anisotropic media: the THz perspectives of left-handed materials  

E-print Network

We demonstrate that non-magnetic ($\\mu \\equiv 1$) left-handed materials can be effectively used for waveguide imaging systems. We also propose a specific THz realization of the non-magnetic left-handed material based on homogeneous, naturally-occurring media.

Viktor A. Podolskiy; Leo Alekseev; Evgenii E. Narimanov

2005-05-03

239

Composite materials: Fatigue and fracture. Vol. 3  

NASA Technical Reports Server (NTRS)

The present volume discusses topics in the fields of matrix cracking and delamination, interlaminar fracture toughness, delamination analysis, strength and impact characteristics, and fatigue and fracture behavior. Attention is given to cooling rate effects in carbon-reinforced PEEK, the effect of porosity on flange-web corner strength, mode II delamination in toughened composites, the combined effect of matrix cracking and free edge delamination, and a 3D stress analysis of plain weave composites. Also discussed are the compression behavior of composites, damage-based notched-strength modeling, fatigue failure processes in aligned carbon-epoxy laminates, and the thermomechanical fatigue of a quasi-isotropic metal-matrix composite.

O'Brien, T. K. (editor)

1991-01-01

240

Electromagnetic properties of Permendur granular composite materials containing flaky particles  

NASA Astrophysics Data System (ADS)

Electromagnetic properties of Permendur (Fe50Co50 alloy) granular composite materials containing flaky particle have been studied from the RF to microwave frequency range. Properties of the flaky particle composites were compared with the spherical particle ones. The electrical conductivity of the flaky particle composite was higher than that of the spherical particle composite at the same particle content. An insulator to metal transition was observed at the percolation threshold ?c in both composites. The ?c of the flaky particle composite was lower than that of the spherical one. The relative complex permittivity indicates that the insulating state has dielectric properties. For the spherical particle composite, the permittivity enhancement caused by particle cluster formation can be described by the effective cluster model (ECM). The enhancement of the dielectric constant in the flaky particle composite is larger than the ECM prediction. A negative permittivity spectrum indicating a low frequency plasmonic state was observed in the metallic 70 vol. % flaky particle composite. The relative complex permeability spectra of the flaky particle composite are different from those of the spherical one. The flaky particle composite shows a larger permeability value and lower permeability dispersion frequency than the spherical particle composite. Negative permeability spectra were observed in the both composite materials. The negative permeability frequency band of the flaky particle composite is lower than that of the spherical particle composite owing to the demagnetizing field effect.

Kasagi, Teruhiro; Tsutaoka, Takanori; Hatakeyama, Kenichi

2014-10-01

241

Controlling Performance of Laminated Composites Using Piezoelectric Materials  

E-print Network

-electro-elastic constitutive model for transversely isotropic materials is used for each ply in the composite laminates. The first-ply failure and ultimate laminate failure criteria of composite laminates are used to predict the failure stress and mode of the composite...

Hasan, Zeaid

2012-02-14

242

Structural assessment of a novel carpet composite material  

NASA Astrophysics Data System (ADS)

Noise pollution caused by vehicles has always been a concern to the communities in the vicinity of highways and busy roadways. The carpet composite material was recently developed and proposed to be utilized as sound-walls in highways. In the carpet composite material post-consumer carpet is used as reinforcing element inside and epoxy matrix. The main focus of this work is to assess flexural behavior of this novel material. Tests were performed on the individual components of the composite material. Using the results from the test and a theoretical approach, a model was proposed that describes the flexural behavior and also a close estimate of the flexural strength of the carpet composite material. In this work the contribution of the carpet in flexural behavior of the composite material was investigated. It was found that the carpet is weaker than the epoxy and the contribution of the carpet in flexural strength of the composite material is small. It was also found that using the carpet inside the epoxy results in 63% decrease in ultimate strength of the section, however; the gain in ductility is considerable. Based on the flexural test results the composite section follows a bilinear behavior. To determine the capacity of the composite, the effective epoxy section is to be determined before and after the tension cracks form at the bottom of the section. Using the epoxy section analysis described in this work, the strength of the composite section can be calculated at cracking and ultimate capacity.

Abbaszadeh, Ali

243

Composite materials for precision space reflector panels  

Microsoft Academic Search

One of the critical technology needs of large precision reflectors for future astrophysical and optical communications satellites lies in the area of structural materials. Results from a materials research and development program at NASA Langley Research Center to provide materials for these reflector applications are discussed. Advanced materials that meet the reflector panel requirements are identified and thermal, mechanical and

Stephen S. Tompkins; Joan G. Funk; David E. Bowles; Timothy W. Towell; John W. Connell

1992-01-01

244

Evaluation of Composite Materials for Use on Launch Complexes  

NASA Technical Reports Server (NTRS)

Commercially available composite structural shapes were evaluated for use. These composites, fiberglass-reinforced polyester and vinylester resin materials are being used extensively in the fabrication and construction of low maintenance, corrosion resistant structures. The evaluation found that in many applications these composite materials can be successfully used at the space center. These composite materials should not be used where they will be exposed to the hot exhaust plume/cloud of the launch vehicle during the liftoff, and caution should be taken in their use in areas where electrostatic discharge and hypergolic propellant compatibility are primary concerns.

Finchum, A.; Welch, Peter J.

1989-01-01

245

Process for fabricating composite material having high thermal conductivity  

DOEpatents

A process for fabricating a composite material such as that having high thermal conductivity and having specific application as a heat sink or heat spreader for high density integrated circuits. The composite material produced by this process has a thermal conductivity between that of diamond and copper, and basically consists of coated diamond particles dispersed in a high conductivity metal, such as copper. The composite material can be fabricated in small or relatively large sizes using inexpensive materials. The process basically consists, for example, of sputter coating diamond powder with several elements, including a carbide forming element and a brazeable material, compacting them into a porous body, and infiltrating the porous body with a suitable braze material, such as copper-silver alloy, thereby producing a dense diamond-copper composite material with a thermal conductivity comparable to synthetic diamond films at a fraction of the cost.

Colella, Nicholas J. (Livermore, CA); Davidson, Howard L. (San Carlos, CA); Kerns, John A. (Livermore, CA); Makowiecki, Daniel M. (Livermore, CA)

2001-01-01

246

Advanced organic composite materials for aircraft structures: Future program  

NASA Technical Reports Server (NTRS)

Revolutionary advances in structural materials have been responsible for revolutionary changes in all fields of engineering. These advances have had and are still having a significant impact on aircraft design and performance. Composites are engineered materials. Their properties are tailored through the use of a mix or blend of different constituents to maximize selected properties of strength and/or stiffness at reduced weights. More than 20 years have passed since the potentials of filamentary composite materials were identified. During the 1970s much lower cost carbon filaments became a reality and gradually designers turned from boron to carbon composites. Despite progress in this field, filamentary composites still have significant unfulfilled potential for increasing aircraft productivity; the rendering of advanced organic composite materials into production aircraft structures was disappointingly slow. Why this is and research and technology development actions that will assist in accelerating the application of advanced organic composites to production aircraft is discussed.

1987-01-01

247

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

NASA Technical Reports Server (NTRS)

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.

1975-01-01

248

NEW ECO-FRIENDLY HYBRID COMPOSITE MATERIALS FOR CIVIL CONSTRUCTION  

Microsoft Academic Search

This paper concerns the development of new hybrid composite materials using granulated cork, a by-product of cork industry, cellulose pulp, from recycling of paper residues, and hemp fibres. The binder used is either cellulose pulp or lime-pozzolan mixture. Such materials may be used as composite boards and mortars for non structural elements of construction, such as dry walls and ceiling

R. Eires; J. P. Nunes; R. Fangueiro; S. Jalali; A. Camões

249

Pistons and Cylinders Made of Carbon-Carbon Composite Materials  

NASA Technical Reports Server (NTRS)

An improved reciprocating internal combustion engine has a plurality of engine pistons, which are fabricated from carbon---carbon composite materials, in operative association with an engine cylinder block, or an engine cylinder tube, or an engine cylinder jug, all of which are also fabricated from carbon-carbon composite materials.

Rivers, H. Kevin (Inventor); Ransone, Philip O. (Inventor); Northam, G. Burton (Inventor); Schwind, Francis A. (Inventor)

2000-01-01

250

Pistons and Cylinders Made of Carbon-Carbon Composite Materials  

NASA Technical Reports Server (NTRS)

An improved reciprocating internal combustion engine has a plurality of engine pistons, which are fabricated from carbon-carbon composite materials, in operative association with an engine cylinder block, or an engine cylinder tube, or an engine cylinder jug, all of which are also fabricated from carbon-carbon composite materials.

Rivers, H. Kevin (Inventor); Ransone, Philip O. (Inventor); Northam, G. Burton (Inventor); Schwind, Francis A. (Inventor)

2000-01-01

251

Progressive failure analysis of fibrous composite materials and structures  

NASA Technical Reports Server (NTRS)

A brief description is given of the modifications implemented in the PAFAC finite element program for the simulation of progressive failure in fibrous composite materials and structures. Details of the memory allocation, input data, and the new subroutines are given. Also, built-in failure criteria for homogeneous and fibrous composite materials are described.

Bahei-El-din, Yehia A.

1990-01-01

252

Finite Element Analysis of Layered Fiber Composite Structures Accounting for the Material's Microstructure and Delamination  

NASA Astrophysics Data System (ADS)

The present paper focuses on composite structures which consist of several layers of carbon fiber reinforced plastics (CFRP). For such layered composite structures, delamination constitutes one of the major failure modes. Predicting its initiation is essential for the design of these composites. Evaluating stress-strength relation based onset criteria requires an accurate representation of the through-the-thickness stress distribution, which can be particularly delicate in the case of shell-like structures. Thus, in this paper, a solid-shell finite element formulation is utilized which allows to incorporate a fully three-dimensional material model while still being suitable for applications involving thin structures. Moreover, locking phenomena are cured by using both the EAS and the ANS concept, and numerical efficiency is ensured through reduced integration. The proposed anisotropic material model accounts for the material's micro-structure by using the concept of structural tensors. It is validated by comparison to experimental data as well as by application to numerical examples.

Stier, Bertram; Simon, Jaan-Willem; Reese, Stefanie

2014-05-01

253

Characterization and prediction of abrasive wear of powder composite materials  

Microsoft Academic Search

Composite materials produced by powder metallurgy provide a solution in many engineering applications where materials with high abrasion and erosion resistance are required. The actual wear behaviour of the material is associated with many external factors (particle size, velocity, angularity, etc.) and intrinsic material properties (hardness, toughness, Young modulus, etc.). Hardness and toughness properties of such tribomaterials are highly dependent

R. Veinthal; P. Kulu; J. Pirso; H. Käerdi

2009-01-01

254

Advanced composite structures. [metal matrix composites - structural design criteria for spacecraft construction materials  

NASA Technical Reports Server (NTRS)

A monograph is presented which establishes structural design criteria and recommends practices to ensure the design of sound composite structures, including composite-reinforced metal structures. (It does not discuss design criteria for fiber-glass composites and such advanced composite materials as beryllium wire or sapphire whiskers in a matrix material.) Although the criteria were developed for aircraft applications, they are general enough to be applicable to space vehicles and missiles as well. The monograph covers four broad areas: (1) materials, (2) design, (3) fracture control, and (4) design verification. The materials portion deals with such subjects as material system design, material design levels, and material characterization. The design portion includes panel, shell, and joint design, applied loads, internal loads, design factors, reliability, and maintainability. Fracture control includes such items as stress concentrations, service-life philosophy, and the management plan for control of fracture-related aspects of structural design using composite materials. Design verification discusses ways to prove flightworthiness.

1974-01-01

255

Buckling analyses of composite laminate skew plates with material nonlinearity  

Microsoft Academic Search

A nonlinear material constitutive model, including a nonlinear in-plane shear formulation and the Tsai–Wu failure criterion, for fiber–composite laminate materials is employed to carry out finite element buckling analyses for composite laminate skew plates under uniaxial compressive loads. The influences of laminate layup, plate skew angle and plate aspect ratio on the buckling resistance of composite laminate skew plates are

Hsuan-Teh Hu; Chia-Hao Yang; Fu-Ming Lin

2006-01-01

256

21 CFR 878.3500 - Polytetrafluoroethylene with carbon fibers composite implant material.  

Code of Federal Regulations, 2010 CFR

... Polytetrafluoroethylene with carbon fibers composite implant material... Polytetrafluoroethylene with carbon fibers composite implant material...A polytetrafluoroethylene with carbon fibers composite implant...

2010-04-01

257

Nano composite phase change materials microcapsules  

NASA Astrophysics Data System (ADS)

MicroPCMs with nano composite structures (NC-MicroPCMs) have been systematically studied. NC-MicroPCMs were fabricated by the in situ polymerization and addition of silver NPs into core-shell structures. A full factorial experiment was designed, including three factors of core/shell, molar ratio of formaldehyde/melamine and NPs addition. 12 MicroPCMs samples were prepared. The encapsulated efficiency is approximately 80% to 90%. The structural/morphological features of the NC-MicroPCMs were evaluated. The size was in a range of 3.4 mu m to 4.0 mu m. The coarse appearance is attributed to NPs and NPs are distributed on the surface, within the shell and core. The NC-MicroPCMs contain new chemical components and molecular groups, due to the formation of chemical bonds after the pretreatment of NPs. Extra X-ray diffraction peaks of silver were found indicating silver nano-particles were formed into an integral structure with the core/shell structure by means of chemical bonds and physical linkages. Extra functionalities were found, including: (1) enhancement of IR radiation properties; (2) depression of super-cooling, and (3) increase of thermal stabilities. The effects of SERS (Surface Enhanced Raman Spectroscopy) arising from the silver nano-particles were observed. The Raman scattering intensity was magnified more than 100 times. These effects were also exhibited in macroscopic level in the fabric coatings as enhanced IR radiation properties were detected by the "Fabric Infrared Radiation Management Tester" (FRMT). "Degree of Crystallinity" (DOC) was measured and found the three factors have a strong influence on it. DOC is closely related to thermal stability and MicroPCMs with a higher DOC show better temperature resistance. The thermal regulating effects of the MicroPCMs coatings were studied. A "plateau regions" was detected around the temperature of phase change, showing the function of PCMs. Addition of silver nano-particles to the MicroPCMs has a positive influence on it. NC-MicroPCMs with introducing silver nano particles into the MicroPCMs structure, have shown excellent multifunctional thermal properties and thermal stabilities that are far beyond those of the conventional MicroPCMs. The novel NC-MicroPCMs can be used to develop advanced smart materials and products with prosperous and promising applications in a number of industries.

Song, Qingwen

258

Corrosion inhibiting composition for treating asbestos containing materials  

DOEpatents

A composition for transforming a chrysotile asbestos-containing material into a non-asbestos material is disclosed. The composition comprises water, at least about 30% by weight of an acid component, optionally a source of fluoride ions, and a corrosion inhibiting amount of thiourea, a lower alkylthiourea, a C{sub 8}{single_bond}C{sub 15} alkylpyridinium halide or mixtures. A method of transforming an asbestos-containing building material, while part of a building structure, into a non-asbestos material by using the present composition also is disclosed.

Hartman, J.R.

1998-04-21

259

Nondestructive evaluation of composite materials - A design philosophy  

NASA Technical Reports Server (NTRS)

Efficient and reliable structural design utilizing fiber reinforced composite materials may only be accomplished if the materials used may be nondestructively evaluated. There are two major reasons for this requirement: (1) composite materials are formed at the time the structure is fabricated and (2) at practical strain levels damage, changes in the condition of the material, that influence the structure's mechanical performance is present. The fundamental basis of such a nondestructive evaluation capability is presented. A discussion of means of assessing nondestructively the material condition as well as a damage mechanics theory that interprets the material condition in terms of its influence on the mechanical response, stiffness, strength and life is provided.

Duke, J. C., Jr.; Henneke, E. G., II; Stinchcomb, W. W.; Reifsnider, K. L.

1984-01-01

260

Reflection and transmission for layered composite materials  

NASA Technical Reports Server (NTRS)

A layered planar structure consisting of different bianisotropic materials separated by jump-immittance sheets is considered. Reflection and transmission coefficients are determined via a chain-matrix algorithm. Applications are important for radomes and radar-absorbing materials.

Graglia, Roberto D.; Uslenghi, Piergiorgio L. E.

1991-01-01

261

Optical determination of anisotropic material properties of bovine articular cartilage in compression  

Microsoft Academic Search

The precise nature of the material symmetry of articular cartilage in compression remains to be elucidated. The primary objective of this study was to determine the equilibrium compressive Young's moduli and Poisson's ratios of bovine cartilage along multiple directions (parallel and perpendicular to the split line direction, and normal to the articular surface) by loading small cubic specimens (0.9 ?

B. Wang; Nadeen O. Chahine; Clark T. Hung; Gerard A. Ateshian

262

Cyanide Bridged Molecular Magnetic Materials with Anisotropic Transition Metal Ions: Investigation of Bistable Magnetic Phenomena  

E-print Network

, with the highest ordering temperature being observed for the K+ analog which exhibits a TC of 28.5 K. The phenomenon of linkage isomerism reported for PB analogs and other molecular materials that incorporate the [Cr(CN)6]3- ion wherein the CN ligand reverses its...

Avendano, Carolina

2011-08-08

263

Multilayer composite material and method for evaporative cooling  

NASA Technical Reports Server (NTRS)

A multilayer composite material and method for evaporative cooling of a person employs an evaporative cooling liquid that changes phase from a liquid to a gaseous state to absorb thermal energy. The evaporative cooling liquid is absorbed into a superabsorbent material enclosed within the multilayer composite material. The multilayer composite material has a high percentage of the evaporative cooling liquid in the matrix. The cooling effect can be sustained for an extended period of time because of the high percentage of phase change liquid that can be absorbed into the superabsorbent. Such a composite can be used for cooling febrile patients by evaporative cooling as the evaporative cooling liquid in the matrix changes from a liquid to a gaseous state to absorb thermal energy. The composite can be made with a perforated barrier material around the outside to regulate the evaporation rate of the phase change liquid. Alternatively, the composite can be made with an imperveous barrier material or semipermeable membrane on one side to prevent the liquid from contacting the person's skin. The evaporative cooling liquid in the matrix can be recharged by soaking the material in the liquid. The multilayer composite material can be fashioned into blankets, garments and other articles.

Buckley, Theresa M. (Inventor)

2002-01-01

264

Using internal fibre geometry to improve the performance of pin-loaded holes in composite materials  

NASA Astrophysics Data System (ADS)

The anisotropic nature of fibre reinforced composites leads to large stress concentrations around pin-loaded holes through standard weave cloths. Proper understanding of how this anisotropic nature affects the load distribution around holes can be utilised to reduce these concentrations if sufficient thought is given to the internal fibre geometry near to the hole. Such local reinforcements need not be highly complex and can be readily produced without excessive effort, producing significant improvements in performance.

Jones, S. E.; Platts, M. J.

1996-03-01

265

Scattering loss in electro-optic particulate composite materials  

E-print Network

The effective permittivity dyadic of a composite material containing particulate constituent materials with one constituent having the ability to display the Pockels effect is computed, using an extended version of the strong-permittivity-fluctuation theory which takes account of both the distributional statistics of the constituent particles and their sizes. Scattering loss, thereby incorporated in the effective electromagnetic response of the homogenized composite material, is significantly affected by the application of a low-frequency (dc) electric field.

MacKay, T G; Mackay, Tom G.; Lakhtakia, Akhlesh

2007-01-01

266

LDEF fiber-composite materials characterization  

NASA Technical Reports Server (NTRS)

Degradation of a number of fiber/polymer composites located on the leading and trailing surfaces of LDEF where the atomic oxygen (AO) fluences ranged from 10(exp 22) to 10(exp 4) atoms/cm(sup 2), respectively, was observed and compared. While matrices of the composites on the leading edge generally exhibited considerable degradation and erosion-induced fragmentation, this 'asking' process was confined to the near surface regions because these degraded structures acted as a 'protective blanket' for deeper-lying regions. This finding leads to the conclusion that simple surface coatings can significantly retard AO and other combinations of degrading phenomena in low-Earth orbit. Micrometeoroid and debris particle impacts were not a prominent feature on the fiber composites studied and apparently do not contribute in a significant way to their degradation or alteration in low-Earth orbit.

Miglionico, C. J.; Stein, C.; Roybal, R. E.; Murr, L. E.

1993-01-01

267

Flexible composite material with phase change thermal storage  

NASA Technical Reports Server (NTRS)

A highly flexible composite material having a flexible matrix containing a phase change thermal storage material. The composite material can be made to heat or cool the body or to act as a thermal buffer to protect the wearer from changing environmental conditions. The composite may also include an external thermal insulation layer and/or an internal thermal control layer to regulate the rate of heat exchange between the composite and the skin of the wearer. Other embodiments of the PCM composite also provide 1) a path for evaporation or direct absorption of perspiration from the skin of the wearer for improved comfort and thermal control, 2) heat conductive pathways within the material for thermal equalization, 3) surface treatments for improved absorption or rejection of heat by the material, and 4) means for quickly regenerating the thermal storage capacity for reuse of the material. Applications of the composite materials are also described which take advantage of the composite's thermal characteristics. The examples described include a diver's wet suit, ski boot liners, thermal socks, gloves and a face mask for cold weather activities, and a metabolic heating or cooling blanket useful for treating hypothermia or fever patients in a medical setting and therapeutic heating or cooling orthopedic joint supports.

Buckley, Theresa M. (Inventor)

1999-01-01

268

Flexible composite material with phase change thermal storage  

NASA Technical Reports Server (NTRS)

A highly flexible composite material having a flexible matrix containing a phase change thermal storage material. The composite material can be made to heat or cool the body or to act as a thermal buffer to protect the wearer from changing environmental conditions. The composite may also include an external thermal insulation layer and/or an internal thermal control layer to regulate the rate of heat exchange between the composite and the skin of the wearer. Other embodiments of the PCM composite also provide 1) a path for evaporation or direct absorption of perspiration from the skin of the wearer for improved comfort and thermal control, 2) heat conductive pathways within the material for thermal equalization, 3) surface treatments for improved absorption or rejection of heat by the material, and 4) means for quickly regenerating the thermal storage capacity for reuse of the material. Applications of the composite materials are also described which take advantage of the composite's thermal characteristics. The examples described include a diver's wet suit, ski boot liners, thermal socks, ,gloves and a face mask for cold weather activities, and a metabolic heating or cooling blanket useful for treating hypothermia or fever patients in a medical setting and therapeutic heating or cooling orthopedic joint supports.

Buckley, Theresa M. (Inventor)

2001-01-01

269

Damage detection in composite materials by FBGs  

NASA Astrophysics Data System (ADS)

Embedded fiber Bragg gratings (FBGs) are sensitive to changes of near strain fields in a composite host monolithic structure, typical of aircraft airframes. FBGs have been embedded in different configurations (a typical position is the skin -- stiffener interface in a monolithic structure) for detecting events associated to damage occurrence. Thus, it is possible to think in FBGs not only as strain sensors, in a classical load monitoring configuration, but as a part of a structural health monitoring (SHM) system in composite structures dimensioned following damage tolerance criteria.

Menendez, Jose M.; Munoz, Pedro; Pintado, J. M.; Guemes, Alfredo

2004-06-01

270

Thermal expansion behaviour of thermoplastic composite materials  

SciTech Connect

The thermal expansion behavior of a number of commercially available and experimental continuous fiber-reinforced PEEK composites is assessed. The thermal expansion characteristics of Hercules AS4 reinforced PEEK (APC-2/AS4, ICI Fiberite) are reported in some detail, and it is shown that behavior is both reasonable and predictable. Further, it is found that repeated thermal cycling between -160 C and +120 C has no effect on the behavior of unidirectional laminates, and that the inherent characteristics of the composite are likely to promote such insensitivity. 16 refs.

Barnes, J.A.; Simms, I.J.; Farrow, G.J.; Jackson, D.; Wostenholm, G. (Imperial Chemical Industries, PLC, Materials Research Centre, Wilton (England) Salford Univ. (England))

1990-01-01

271

Deformation and failure information from composite materials via acoustic emission  

NASA Technical Reports Server (NTRS)

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

Hamstad, M. A.

1978-01-01

272

Two-dimensional optimization of material composition of functionally graded materials using meshless analyses  

E-print Network

Two-dimensional optimization of material composition of functionally graded materials using-dimensional simulation and optimization of material distribution of functionally graded materials for thermomechanical processes. The proposed approach focuses on metal/ceramic functionally graded materials, which offer great

Vel, Senthil

273

Solid freeform fabrication of highly loaded composite materials  

NASA Astrophysics Data System (ADS)

Composites are known for their unique blend of modulus, strength, and toughness. This study focuses on two types of composites; organic-inorganic hybrids and the mineralization of highly swollen polymer gels. Both of these composite systems mimic the biological process of composite formation, known as biomineralization. Biomineralization allows for the control of the precipitating phase through an interaction with the organic matrix. This allows higher volume fractions of inorganic material than can be achieved by many traditional processing techniques. Solid freeform fabrication is a processing method that builds materials by the sequential addition of thin layers. As long as the material can easily be converted from a liquid to a solid, it should be amenable for this processing technique. Freeform fabrication has three distinctions from traditional processing techniques that may enable the formation of composite materials with improved mechanical properties. These are the sequential addition of layers, which allows a layer by layer influence of chemistry, the ability to form complex geometries, and finally, extrusion freeform fabrication has been shown to align fibers due to the extrusion of the slurry through a needle. Cracking and shrinkage still play a major role in forming solid parts. The use of an open mesh structure in combination with proper materials selection allowed the formation of highly loaded composite materials without cracking. The modulus values of these materials ranged from 0.1 GPa to 6.0 GPa. The mechanical properties of these materials were modeled.

Souvignier, Chad William

274

Advanced AE Techniques in Composite Materials Research  

NASA Technical Reports Server (NTRS)

Advanced, waveform based acoustic emission (AE) techniques have been successfully used to evaluate damage mechanisms in laboratory testing of composite coupons. An example is presented in which the initiation of transverse matrix cracking was monitored. In these tests, broad band, high fidelity acoustic sensors were used to detect signals which were then digitized and stored for analysis. Analysis techniques were based on plate mode wave propagation characteristics. This approach, more recently referred to as Modal AE, provides an enhanced capability to discriminate and eliminate noise signals from those generated by damage mechanisms. This technique also allows much more precise source location than conventional, threshold crossing arrival time determination techniques. To apply Modal AE concepts to the interpretation of AE on larger composite specimens or structures, the effects of modal wave propagation over larger distances and through structural complexities must be well characterized and understood. To demonstrate these effects, measurements of the far field, peak amplitude attenuation of the extensional and flexural plate mode components of broad band simulated AE signals in large composite panels are discussed. These measurements demonstrated that the flexural mode attenuation is dominated by dispersion effects. Thus, it is significantly affected by the thickness of the composite plate. Furthermore, the flexural mode attenuation can be significantly larger than that of the extensional mode even though its peak amplitude consists of much lower frequency components.

Prosser, William H.

1996-01-01

275

Delamination durability of composite materials for rotorcraft  

NASA Technical Reports Server (NTRS)

Delamination is the most commonly observed failure mode in composite rotorcraft dynamic components. Although delamination may not cause immediate failure of the composite part, it often precipitates component repair or replacement, which inhibits fleet readiness, and results in increased life cycle costs. A fracture mechanics approach for analyzing, characterizing, and designing against delamination will be outlined. Examples of delamination problems will be illustrated where the strain energy release rate associated with delamination growth was found to be a useful generic parameter, independent of thickness, layup, and delamination source, for characterizing delamination failure. Several analysis techniques for calculating strain energy release rates for delamination from a variety of sources will be outlined. Current efforts to develop ASTM standard test methods for measuring interlaminar fracture toughness and developing delamination failure criteria will be reviewed. A technique for quantifying delamination durability due to cyclic loading will be presented. The use of this technique for predicting fatigue life of composite laminates and developing a fatigue design philosophy for composite structural components will be reviewed.

Obrien, T. Kevin

1988-01-01

276

LIGNOCELLULOSIC-PLASTIC COMPOSITES FROM RECYCLED MATERIALS  

EPA Science Inventory

Waste wood, waste paper, and waste plastics are major components of MSW and offer great opportunities as recycled ingredients in wood-fiber plastic composites. USEPA and the USDA Forest Products Laboratory (FPL) are collaborating on a research project to investigate the processin...

277

Advanced composites: Fabrication processes for selected resin matrix materials  

NASA Technical Reports Server (NTRS)

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.

Welhart, E. K.

1976-01-01

278

Preparation of composite materials in space. Volume 2: Technical report  

NASA Technical Reports Server (NTRS)

A study to define promising materials, significant processing criteria, and the related processing techniques and apparatus for the preparation of composite materials in space was conducted. The study also established a program for zero gravity experiments and the required developmental efforts. The following composite types were considered: (1) metal-base fiber and particle composites, including cemented compacts, (2) controlled density metals, comprising plain and reinforced metal foams, and (3) unidirectionally solidified eutectic alloys. A program of suborbital and orbital experiments for the 1972 to 1978 time period was established to identify materials, processes, and required experiment equipment.

Steurer, W. H.; Kaye, S.

1973-01-01

279

Composite metal foil and ceramic fabric materials  

DOEpatents

The invention comprises new materials useful in a wide variety of terrestrial and space applications. In one aspect, the invention comprises a flexible cloth-like material comprising a layer of flexible woven ceramic fabric bonded with a layer of metallic foil. In another aspect, the invention includes a flexible fluid impermeable barrier comprising a flexible woven ceramic fabric layer having metal wire woven therein. A metallic foil layer is incontinuously welded to the woven metal wire. In yet another aspect, the invention includes a material comprising a layer of flexible woven ceramic fabric bonded with a layer of an organic polymer. In still another aspect, the invention includes a rigid fabric structure comprising a flexible woven ceramic fabric and a resinous support material which has been hardened as the direct result of exposure to ultraviolet light. Inventive methods for producing such material are also disclosed.

Webb, Brent J. (Richland, WA); Antoniak, Zen I. (Richland, WA); Prater, John T. (Chapel Hill, NC); DeSteese, John G. (Kennewick, WA)

1992-01-01

280

Temperature dependence of the anisotropic deformation of Zr-2.5%Nb pressure tube material during micro-indentation  

NASA Astrophysics Data System (ADS)

The effect of temperature on the anisotropic plastic deformation of textured Zr-2.5%Nb pressure tube material was studied using micro-indentation tests performed in the axial, radial, and transverse directions of the tube over the temperature range from 25 to 400 °C. The ratio of the indentation stress in the transverse direction relative to that in the radial and axial directions was 1.29:1 and 1.26:1 at 25 °C but decreased to 1.22:1 and 1.05:1 at 400 °C. The average activation energy of the obstacles that limit the rate of indentation creep increases, from 0.72 to 1.33 eV, with increasing temperature from 25 to 300 °C and is independent of indentation direction. At temperature between 300 °C and 400 °C the measured activation energy is considerably reduced for indentation creep in the transverse direction relative to that of either the axial or radial directions. We conclude that, over this temperature range, the strength of the obstacles that limit the time-dependent dislocation glide on the pyramidal slip system changes relative to that on the prismatic slip system. These findings provide new data on the temperature dependence of the yield stress and creep rate, particularly in the radial direction, of Zr-2.5%Nb pressure tubes and shed new light on the effect of temperature on the operation of dislocation glide on the prismatic and pyramidal slip systems which ultimately determines the degree of mechanical anisotropy in the highly textured Zr-2.5Nb pressure tube material used in CANDU nuclear reactors.

Bose, B.; Klassen, R. J.

2011-12-01

281

Quantum Storage of Heralded Polarization Qubits in Birefringent and Anisotropically Absorbing Materials  

NASA Astrophysics Data System (ADS)

Storage of quantum information encoded into heralded single photons is an essential constituent of long-distance quantum communication based on quantum repeaters and of optical quantum information processing. The storage of photonic polarization qubits is, however, difficult because many materials are birefringent and have polarization-dependent absorption. Here we present a simple scheme that eliminates these polarization effects, and we demonstrate it by storing heralded polarization qubits into a solid-state quantum memory. The quantum memory is implemented with a biaxial yttrium orthosilicate (Y2SiO5) crystal doped with rare-earth ions. Heralded single photons generated from a filtered spontaneous parametric down-conversion source are stored, and quantum state tomography of the retrieved polarization state reveals an average fidelity of 97.5±0.4%, which is significantly higher than what is achievable with a measure-and-prepare strategy.

Clausen, Christoph; Bussières, Félix; Afzelius, Mikael; Gisin, Nicolas

2012-05-01

282

Numerical simulation of ultrasonic wave propagation in anisotropic and attenuative solid materials.  

PubMed

The axisymmetric elastodynamic finite element code developed is capable of predicting quantitatively accurate displacement fields for elastic wave propagation in isotropic and transversely isotropic materials. The numerical algorithm incorporates viscous damping by adding a time-dependent tensor to Hooke's law. Amplitude comparisons are made between the geometric attenuation in the far field and the corresponding finite element predictions to investigate the quality and validity of the code. Through-transmission experimental measurements made with a 1 MHz L-wave transducer attached to an aluminum sample support the code predictions. The algorithm successfully models geometric beam spreading dispersion and energy absorption due to viscous damping. This numerical model is a viable tool for the study of elastic wave propagation in nondestructive testing applications. PMID:18267605

You, Z; Lusk, M; Ludwig, R; Lord, W

1991-01-01

283

Microbiological destruction of composite polymeric materials in soils  

NASA Astrophysics Data System (ADS)

Representatives of the same species of microscopic fungi developed on composite materials with similar polymeric matrices independently from the type of soils, in which the incubation was performed. Trichoderma harzianum, Penicillium auranthiogriseum, and Clonostachys solani were isolated from the samples of polyurethane. Fusarium solani, Clonostachys rosea, and Trichoderma harzianum predominated on the surface of ultrathene samples. Ulocladium botrytis, Penicillium auranthiogriseum, and Fusarium solani predominated in the variants with polyamide. Trichoderma harzianum, Penicillium chrysogenum, Aspergillus ochraceus, and Acremonium strictum were isolated from Lentex-based composite materials. Mucor circinelloides, Trichoderma harzianum, and Penicillium auranthiogriseum were isolated from composite materials based on polyvinyl alcohol. Electron microscopy demonstrated changes in the structure of polymer surface (loosening and an increase in porosity) under the impact of fungi. The physicochemical properties of polymers, including their strength, also changed. The following substances were identified as primary products of the destruction of composite materials: stearic acid for polyurethane-based materials; imide of dithiocarbonic acid and 1-nonadecen in variants with ultrathene; and tetraaminopyrimidine and isocyanatodecan in variants with polyamide. N,N-dimethyldodecan amide, 2-methyloximundecanon and 2-nonacosane were identified for composites on the base of Lentex A4-1. Allyl methyl sulfide and imide of dithiocarbonic acid were found in variants with the samples of composites based on polyvinyl alcohol. The identified primary products of the destruction of composite materials belong to nontoxic compounds.

Legonkova, O. A.; Selitskaya, O. V.

2009-01-01

284

Machine augmented composite materials for damping purposes  

E-print Network

are formed by inserting simple machines into a matrix material. In this work the machines take the form of fluid filled tubes, and the tube cross-sectional geometry induces fluid flow when it is deformed in its plane. This flow dissipates mechanical... to the product of the driving frequency and the fluid dynamic viscosity. This is a measure of the ratio of elastic forces in the solid material to the viscous forces in the fluid material that makes up a MAC lamina. Governing equations and simulation methods...

McCutcheon, David Matthew

2005-02-17

285

Electrical Characterizations of Lightning Strike Protection Techniques for Composite Materials  

NASA Technical Reports Server (NTRS)

The growing application of composite materials in commercial aircraft manufacturing has significantly increased the risk of aircraft damage from lightning strikes. Composite aircraft designs require new mitigation strategies and engineering practices to maintain the same level of safety and protection as achieved by conductive aluminum skinned aircraft. Researchers working under the NASA Aviation Safety Program s Integrated Vehicle Health Management (IVHM) Project are investigating lightning damage on composite materials to support the development of new mitigation, diagnosis & prognosis techniques to overcome the increased challenges associated with lightning protection on composite aircraft. This paper provides an overview of the electrical characterizations being performed to support IVHM lightning damage diagnosis research on composite materials at the NASA Langley Research Center.

Szatkowski, George N.; Nguyen, Truong X.; Koppen, Sandra V.; Ely, Jay J.; Mielnik, John J.

2009-01-01

286

Characterization of thermoplastic polyamide composite matrix material  

SciTech Connect

The research described here involves a study for a representative matrix resin, the J1-polymer (a polyamide) proposed by DuPont. The research was conducted in parallel with related studies, primarily by other personnel, of graphite fiber/J1-polymer unidirectional composites. X-ray and transmission electron microscopy studies were conducted to examine the structure/morphology of the neat resin. Thermal analysis by differential scanning calorimetry was used to investigate the effects of different heating and cooling rates and various processing conditions. Dynamic mechanical properties of the neat resin were characterized. The fundamental mechanisms of deformation and failure, including creep, crack growth and fracture behaviors, were examined both at room temperature and at elevated temperature. A number of the techniques were extended to characterize the composite as well as the neat resin.

Chen, W.L.A.

1987-01-01

287

Photorefractivity in liquid crystalline composite materials  

SciTech Connect

We report recent improvements in the photorefractive of liquid crystalline thin film composites containing electron donor and acceptor molecules. The improvements primarily result from optimization of the exothermicity of the intermolecular charge transfer reaction and improvement of the diffusion characteristics of the photogenerated ions. Intramolecular charge transfer dopants produce greater photorefractivity and a 10-fold decrease in the concentration of absorbing chromophores. The mechanism for the generation of mobile ions is discussed.

Wiederrecht, G.P. [Argonne National Lab., IL (United States); Wasielewski, M.R. [Northwestern Univ., Evanston, IL (United States). Dept. of Chemistry

1997-09-01

288

Digital cellular solids : reconfigurable composite materials  

E-print Network

Digital materials are comprised of a small number of types of discrete physical building blocks, which assemble to form constructions that meet the versatility and scalability of digital computation and communication ...

Cheung, Kenneth Chun-Wai

2012-01-01

289

Sulphidation resistance of composite boiler tube materials  

SciTech Connect

A lab-based testing program was undertaken to generate data to better define the sulphidation resistance of composite tubes installed in the lower-furnace section of black liquor recovery boilers. All composite tube cladding alloys tested were observed to have an acceptable corrosion rate at normal operating temperatures (up to 400 C) in the synthetic lower-furnace gaseous environment tested (1% H{sub 2}S-99% N{sub 2}). This acceptable corrosion resistance is due to the expected formation of a relatively protective chromium-rich inner sulphide scale. An increase in temperature up to 560 C was found to significantly increase the corrosion rate. Of the various alloys tested, Alloy HR11N exhibited the lowest corrosion rate at each of the three temperatures tested. Moreover, the corrosion rate was found not to be strongly dependent on the fabrication route (weld overlay versus co-extruded). To minimize corrosion, operating conditions that promote prolonged exposure to elevated temperatures in the lower-furnace section of black liquor recovery boilers should be avoided, regardless of the type of composite tube installed.

Kish, Joseph [McMaster University; Eng, Philip [FPInnovations; Singbeil, Douglas [FPInnovations; Keiser, James R [ORNL

2008-01-01

290

Life prediction and constitutive models for engine hot section anisotropic materials program  

NASA Technical Reports Server (NTRS)

This report presents the results of the first year of a program designed to develop life prediction and constitutive models for two coated single crystal alloys used in gas turbine airfoils. The two alloys are PWA 1480 and Alloy 185. The two oxidation resistant coatings are PWA 273, an aluminide coating, and PWA 286, an overlay NiCoCrAlY coating. To obtain constitutive and/or fatigue data, tests were conducted on coated and uncoated PWA 1480 specimens tensilely loaded in the 100 , 110 , 111 , and 123 directions. A literature survey of constitutive models was completed for both single crystal alloys and metallic coating materials; candidate models were selected. One constitutive model under consideration for single crystal alloys applies Walker's micromechanical viscoplastic formulation to all slip systems participating in the single crystal deformation. The constitutive models for the overlay coating correlate the viscoplastic data well. For the aluminide coating, a unique test method is under development. LCF and TMF tests are underway. The two coatings caused a significant drop in fatigue life, and each produced a much different failure mechanism.

Swanson, G. A.; Linask, I.; Nissley, D. M.; Norris, P. P.; Meyer, T. G.; Walker, K. P.

1986-01-01

291

Metal oxide composite dosimeter method and material  

DOEpatents

The present invention is a method of measuring a radiation dose wherein a radiation responsive material consisting essentially of metal oxide is first exposed to ionizing radiation. The metal oxide is then stimulating with light thereby causing the radiation responsive material to photoluminesce. Photons emitted from the metal oxide as a result of photoluminescence may be counted to provide a measure of the ionizing radiation.

Miller, Steven D. (Richland, WA)

1998-01-01

292

Material Delivery System for Aircraft Composite Component Manufacturing Workshop  

E-print Network

Abstract—This paper presents a material delivery system for the aircraft composite component manufacturing workshop. By analyzing the disadvantages of the passive material supply model, an active material delivery model is proposed. Subsequently, an improved work flow of material delivery is introduced in detail for optimizing the traditional material supply. Barcode technology is used to collect the data of material receiving and issuing in the warehouse. By scanning the barcode, material information and working personnel information can be collected and inputted into the system in real time. The function module of material delivery system is composed of material delivery management, inventory management, and production planning management. The integration relationship between the material delivery system and other systems is also described. Three-layer structure is adopted to design and develop the system. The material delivery system has been implemented in an aircraft composite component manufacturing workshop. The results show that material supply time and cost has been reduced. Index Terms—material delivery, composite component, MES, barcode

Mei Zhongyi; Liu Yongjin; Muhammad Younus

293

Health, safety and environmental requirements for composite materials  

NASA Technical Reports Server (NTRS)

The health, safety and environmental requirements for the production of composite materials are discussed. The areas covered include: (1) chemical identification for each chemical; (2) toxicology; (3) industrial hygiene; (4) fire and safety; (5) environmental aspects; and (6) medical concerns.

Hazer, Kathleen A.

1994-01-01

294

Nondestructive testing of polymer composite materials using THz radiation  

NASA Astrophysics Data System (ADS)

This paper shows an ability to find internal defects in construction of polymer composite material using THz imaging. Using THz vision system resulted in an example of finding internal non-impregnated area in fiberglass.

Yakovlev, Egor V.; Zaytsev, Kirill I.; Fokina, Irina N.; Karasik, Valeriy E.; Yurchenko, Stanislav O.

2014-03-01

295

Flight service environmental effects on composite materials and structures  

NASA Technical Reports Server (NTRS)

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.

Dexter, H. Benson; Baker, Donald J.

1992-01-01

296

ENG 4793: Composite Materials and Processes 1 Combining Thermoplastics with  

E-print Network

1 ENG 4793: Composite Materials and Processes 1 Combining Thermoplastics with Reinforcing Fibers and Processes 7 Short Fiber Processes Thermoplastic Pellets Chopped Fibers Extruder Strand Die Water Bath Pellets Cooler Rovings Thermoplastic Pellets Counter Flow Die ( USP 5,176,775 ) #12;3 ENG 4793: Composite

Colton, Jonathan S.

297

Composite materials based on wastes of flat glass processing  

Microsoft Academic Search

Glass mirrors scrap and poly (vinyl) butiral waste (PVB) obtained from flat glass processing plants were investigated as raw materials to produce composites. The emphasis was on studying the influence of milled glass mirror waste contents on properties of composites produced with PVB. The characterization involved: elongation under rupture, water absorption, tensile strength and elastic modulus tests. The results showed

A. V. Gorokhovsky; J. I. Escalante-Garcia; G. Yu. Gashnikova; L. P. Nikulina; S. E. Artemenko

2005-01-01

298

Structurally integrated fiber optic damage assessment system for composite materials  

Microsoft Academic Search

Progress toward the development of a fiber optic damage assessment system for composite materials is reported. This system, based on the fracture of embedded optical fibers, has been characterized with respect to the orientation and location of the optical fibers in the composite. Together with a special treatment, these parameters have been tailored to yield a system capable of detecting

N. D. W. Glossop; J. Lymer; M. Leblanc; S. Dubois; W. Tsaw; R. C. Tennyson

1989-01-01

299

A physically-based abrasive wear model for composite materials  

Microsoft Academic Search

A simple physically-based model for the abrasive wear of composite materials is presented based on the mechanics and mechanisms associated with sliding wear in soft (ductile)- matrix composites containing hard (brittle) reinforcement particles. The model is based on the assumption that any portion of the reinforcement that is removed as wear debris cannot contribute to the wear resistance of the

Gun Y. Lee; C. K. H. Dharan; R. O. Ritchie

2002-01-01

300

A physically-based abrasive wear model for composite materials  

Microsoft Academic Search

A simple physically-based model for the abrasive wear of composite materials is presented based on the mechanics and mechanisms associated with sliding wear in soft (ductile) matrix composites containing hard (brittle) reinforcement particles. The model is based on the assumption that any portion of the reinforcement that is removed as wear debris cannot contribute to the wear resistance of the

Gun Y. Lee; C. K. H. Dharan; Robert O. Ritchie

2001-01-01

301

Polymer?Nanoparticle Composites: Preparative Methods and Electronically Active Materials  

Microsoft Academic Search

The field of nanoparticle?polymer composites is attractive from the standpoint of integrating the key features of both polymers and nanoparticles into hybrid or composite materials. Nanocomposites geared towards electronic and photophysical targets comprise an intriguing subset of the field, and benefit from interdisciplinary efforts in nanoparticle and polymer synthesis, along with methodology that provides the dispersion, orientation, and\\/or the assembly

P. K. Sudeep; Todd Emrick

2007-01-01

302

Magnetic-marker system using ferrite composite materials  

SciTech Connect

The author`s group has developed some new ferrite composite materials by mixing ferrite by-products with binders such as cement, asphalt cement and epoxy resin. The authors have also developed a magnetic marker sensing system consisting of the ferrite composite material used as a magnetic marker embedded in an asphalt pavement or other surface and a portable magnetic sensor. This system has been applied in a guide lane for the blind and in a speed meter for a motor vehicle.

Mayama, Masakazu [Hokkaido Institute of Technology, Sapporo (Japan)

1993-12-31

303

Teaching Composition in Prisons: Methods and Materials.  

ERIC Educational Resources Information Center

A pilot study gathered information on materials and methods used by writing instructors teaching in prisons in Tennessee, Kentucky, Illinois, and Missouri via a questionnaire. The classes taught by the respondents were all at the college level, were sponsored by various universities and colleges, and all but two were taught at maximum security…

Mowery, Carl D., Jr.

304

Coplanar circulator made from composite magnetic material  

Microsoft Academic Search

This paper deals with the operation of a Y- junction coplanar circulator. It operates at high frequencies (>40 GHz). Barium hexaferrite particles within a host matrix form the integrated magnetic material in this device. The structure of this 3-port microwave device and its different characteristics are presented. A three dimensional finite element method was used to calculate the S-parameters and

Taline Boyajian; Didier Vincent; Sophie Neveu; Martine LeBerre; Jean-Jacques Rousseau

2011-01-01

305

Viscoelastic models for polymeric composite materials  

Microsoft Academic Search

An improved model of the mechanical properties of the explosive contained in conventional munitions is needed to accurately simulate performance and accident scenarios in weapons storage facilities. A specific class of explosives can be idealized as a mixture of two components: energetic crystals randomly suspended in a polymeric matrix (binder). Strength characteristics of each component material are important in the

S. G. Bardenhagen; E. N. Harstad; J. C. Jr. Foster; P. J. Maudlin

1996-01-01

306

Composite Structures and Materials Research at NASA Langley Research Center  

NASA Technical Reports Server (NTRS)

A summary of recent composite structures and materials research at NASA Langley Research Center is presented. Fabrication research to develop low-cost automated robotic fabrication procedures for thermosetting and thermoplastic composite materials, and low-cost liquid molding processes for preformed textile materials is described. Robotic fabrication procedures discussed include ply-by-ply, cure-on-the-fly heated placement head and out-of-autoclave electron-beam cure methods for tow and tape thermosetting and thermoplastic materials. Liquid molding fabrication processes described include Resin Film Infusion (RFI), Resin Transfer Molding (RTM) and Vacuum-Assisted Resin Transfer Molding (VARTM). Results for a full-scale composite wing box are summarized to identify the performance of materials and structures fabricated with these low-cost fabrication methods.

Starnes, James H., Jr.; Dexter, H. Benson; Johnston, Norman J.; Ambur, Damodar R.; Cano, roberto J.

2003-01-01

307

Composite Structures and Materials Research at NASA Langley Research Center  

NASA Technical Reports Server (NTRS)

A summary of recent composite structures and materials research at NASA Langley Research Center is presented. Fabrication research to develop low-cost automated robotic fabrication procedures for thermosetting and thermoplastic composite materials, and low-cost liquid molding processes for preformed textile materials is described. Robotic fabrication procedures discussed include ply-by-ply, cure-on-the-fly heated placement head and out-of-autoclave electron-beam cure methods for tow and tape thermosetting and thermoplastic materials. Liquid molding fabrication processes described include Resin Film Infusion (RFI) Resin Transfer Molding (RTM) and Vacuum-Assisted Resin Transfer Molding (VARTM). Results for a full-scale composite wing box are summarized to identify the performance of materials and structures fabricated with these low-cost fabrication methods.

Starnes, James H., Jr.; Dexter, H. Benson; Johnston, Norman J.; Ambur, Damodar R.; Cano, Roberto J.

2001-01-01

308

Method and apparatus for gripping uniaxial fibrous composite materials  

NASA Technical Reports Server (NTRS)

A strip specimen is cut from a unidirectional strong, brittle fiber composite material, and the surfaces of both ends of the specimen are grit blasted. The specimen is then placed between metal load transfer members having grit blasted surfaces. Sufficient compressive stress is applied to the load transfer members to prevent slippage during testing at both elevated temperatures and room temperatures. The need for adhesives, load pads, and other secondary composite processing is eliminated. This gripping system was successful in tensile testing, creep rupture testing, and fatigue testing uniaxial composite materials at 316 C.

Whittenberger, J. D.; Hurwitz, F. I. (inventors)

1984-01-01

309

Composition and process for making an insulating refractory material  

DOEpatents

A composition and process are disclosed for making an insulating refractory material. The composition includes calcined alumina powder, flash activated alumina powder, an organic polymeric binder and a liquid vehicle which is preferably water. Starch or modified starch may also be added. A preferred insulating refractory material made with the composition has a density of about 2.4--2.6 g/cm{sup 3} with reduced thermal conductivity, compared with tabular alumina. Of importance, the formulation has good abrasion resistance and crush strength during intermediate processing (commercial sintering) to attain full strength and refractoriness.

Pearson, A.; Swansiger, T.G.

1998-04-28

310

Composition and process for making an insulating refractory material  

DOEpatents

A composition and process for making an insulating refractory material. The composition includes calcined alumina powder, flash activated alumina powder, an organic polymeric binder and a liquid vehicle which is preferably water. Starch or modified starch may also be added. A preferred insulating refractory material made with the composition has a density of about 2.4-2.6 g/cm.sup.3 with reduced thermal conductivity, compared with tabular alumina. Of importance, the formulation has good abrasion resistance and crush strength during intermediate processing (commercial sintering) to attain full strength and refractoriness, good abrasion resistance and crush strength.

Pearson, Alan (Murrysville, PA); Swansiger, Thomas G. (Apollo, PA)

1998-04-28

311

Composition/bandgap selective dry photochemical etching of semiconductor materials  

DOEpatents

Disclosed is a method of selectively photochemically dry etching a first semiconductor material of a given composition and direct bandgap Eg/sub 1/ in the presence of a second semiconductor material of a different composition and direct bandgap Eg/sub 2/, wherein Eg/sub 2/ > Eg/sub 1/, said second semiconductor material substantially not being etched during said method. The method comprises subjecting both materials to the same photon flux and to the same gaseous etchant under conditions where said etchant would be ineffective for chemical etching of either material were the photons not present, said photons being of an energy greater than Eg/sub 1/ but less than Eg/sub 2/, whereby said first semiconductor material is photochemically etched and said second material is substantially not etched.

Ashby, C.I.H.; Dishman, J.L.

1985-10-11

312

Composition/bandgap selective dry photochemical etching of semiconductor materials  

DOEpatents

A method of selectively photochemically dry etching a first semiconductor material of a given composition and direct bandgap Eg.sub.1 in the presence of a second semiconductor material of a different composition and direct bandgap Eg.sub.2, wherein Eg.sub.2 >Eg.sub.1, said second semiconductor material substantially not being etched during said method, comprises subjecting both materials to the same photon flux and to the same gaseous etchant under conditions where said etchant would be ineffective for chemical etching of either material were the photons not present, said photons being of an energy greater than Eg.sub.1 but less than Eg.sub.2, whereby said first semiconductor material is photochemically etched and said second material is substantially not etched.

Ashby, Carol I. H. (Edgewood, NM); Dishman, James L. (Albuquerque, NM)

1987-01-01

313

Carbon Cryogel Silicon Composite Anode Materials for Lithium Ion Batteries  

NASA Technical Reports Server (NTRS)

A variety of materials are under investigation for use as anode materials in lithium-ion batteries, of which, the most promising are those containing silicon. 10 One such material is a composite formed via the dispersion of silicon in a resorcinol-formaldehyde (RF) gel followed by pyrolysis. Two silicon-carbon composite materials, carbon microspheres and nanofoams produced from nano-phase silicon impregnated RF gel precursors have been synthesized and investigated. Carbon microspheres are produced by forming the silicon-containing RF gel into microspheres whereas carbon nano-foams are produced by impregnating carbon fiber paper with the silicon containing RF gel to create a free standing electrode. 1-4,9 Both materials have demonstrated their ability to function as anodes and utilize the silicon present in the material. Stable reversible capacities above 400 mAh/g for the bulk material and above 1000 mAh/g of Si have been observed.

Woodworth James; Baldwin, Richard; Bennett, William

2010-01-01

314

Fracture analysis of composite materials by using photoelastic technique  

SciTech Connect

In this paper analytical equations have been derived for the determination of strain energy density factor (S-factor) and damage energy density factor (Z-factor) in composite materials. Dilatational and distortional energy density factors are discussed. Applications of stress-optical law in composite fracture analysis are studied. Equations to determine stress intensity factors in composite structure by using photoelastic coating techniques are also derived. The technique and equations introduced in this paper can be effectively applied in complicated composite structure for fracture analysis. They are specially useful for solving engineering problems in which no theoretical results are available.

Zhang, S.Q.; Wang, J.; Zu, J.B.; Sun, H.

1993-12-31

315

Accelerated hygrothermal stabilization of composite materials  

SciTech Connect

Experimentation validated a simple moisture conditioning scheme to prepare Gr/Ep composite parts for precision applications by measuring dimensional changes over 90 days. It was shown that an elevated temperature moisture conditioning scheme produced a dimensionally stable part from which precision structures could be built/machined without significant moisture induced dimensional changes after fabrication. Conversely, that unconditioned Gr/Ep composite panels exhibited unacceptably large dimensional changes (i.e., greater than 125 ppM). It was also shown that time required to produce stable parts was shorter, by more than an order of magnitude, employing the conditioning scheme than using no conditioning scheme (46 days versus 1000+ days). Two final use environments were chosen for the experiments: 50% RH/21C and 0% RH/21C. Fiberite 3034K was chosen for its widespread use in aerospace applications. Two typical lay-ups were chosen, one with low sensitivity to hygrothermal distortions and the other high sensitivity: [0, {plus_minus} 45, 90]s, [0, {plus_minus} 15, 0]s. By employing an elevated temperature, constant humidity conditioning scheme, test panels achieved an equilibrium moisture content in less time, by more than an order of magnitude, than panels exposed to the same humidity environment and ambient temperature. Dimensional changes, over 90 days, were up to 4 times lower in the conditioned panels compared to unconditioned panels. Analysis of weight change versus time of test coupons concluded that the out-of-autoclave moisture content of Fiberite 3034K varied between 0.06 and 0.1%.

Gale, J.A.

1994-05-01

316

Lightweight Composite Materials for Heavy Duty Vehicles  

SciTech Connect

The main objective of this project is to develop, analyze and validate data, methodologies and tools that support widespread applications of automotive lightweighting technologies. Two underlying principles are guiding the research efforts towards this objective: • Seamless integration between the lightweight materials selected for certain vehicle systems, cost-effective methods for their design and manufacturing, and practical means to enhance their durability while reducing their Life-Cycle-Costs (LCC). • Smooth migration of the experience and findings accumulated so far at WVU in the areas of designing with lightweight materials, innovative joining concepts and durability predictions, from applications to the area of weight savings for heavy vehicle systems and hydrogen storage tanks, to lightweighting applications of selected systems or assemblies in light–duty vehicles.

Pruez, Jacky; Shoukry, Samir; Williams, Gergis; Shoukry, Mark

2013-08-31

317

Electrospun Nanofiber Coating of Fiber Materials: A Composite Toughening Approach  

NASA Technical Reports Server (NTRS)

Textile-based composites could significantly benefit from local toughening using nanofiber coatings. Nanofibers, thermoplastic or otherwise, can be applied to the surface of the fiber tow bundle, achieving toughening of the fiber tow contact surfaces, resulting in tougher and more damage-resistant/tolerant composite structures. The same technique could also be applied to other technologies such as tape laying, fiber placement, or filament winding operations. Other modifications to the composite properties such as thermal and electrical conductivity could be made through selection of appropriate nanofiber material. Control of the needle electric potential, precursor solution, ambient temperature, ambient humidity, airflow, etc., are used to vary the diameter and nanofiber coating morphology as needed. This method produces a product with a toughening agent applied to the fiber tow or other continuous composite precursor material where it is needed (at interfaces and boundaries) without interfering with other composite processing characteristics.

Kohlman, Lee W.; Roberts, Gary D.

2012-01-01

318

Olivine Composite Cathode Materials for Improved Lithium Ion Battery Performance  

SciTech Connect

Composite cathode materials in lithium ion batteries have become the subject of a great amount of research recently as cost and safety issues related to LiCoO2 and other layered structures have been discovered. Alternatives to these layered materials include materials with the spinel and olivine structures, but these present different problems, e.g. spinels have low capacities and cycle poorly at elevated temperatures, and olivines exhibit extremely low intrinsic conductivity. Previous work has shown that composite structures containing spinel and layered materials have shown improved electrochemical properties. These types of composite structures have been studied in order to evaluate their performance and safety characteristics necessary for use in lithium ion batteries in portable electronic devices, particularly hybrid-electric vehicles. In this study, we extended that work to layered-olivine and spinel-olivine composites. These materials were synthesized from precursor salts using three methods: direct reaction, ball-milling, and a coreshell synthesis method. X-ray diffraction spectra and electrochemical cycling data show that the core-shell method was the most successful in forming the desired products. The electrochemical performance of the cells containing the composite cathodes varied dramatically, but the low overpotential and reasonable capacities of the spinel-olivine composites make them a promising class for the next generation of lithium ion battery cathodes.

Ward, R.M.; Vaughey, J.T.

2006-01-01

319

Anisotropic layered high-temperature thermoelectric materials based on the two-phase CrSi2-?-FeSi2 system  

NASA Astrophysics Data System (ADS)

The feasibility of synthesizing a wide spectrum of multiphase microstructurally ordered high-temperature thermoelectrics with highly anisotropic thermoelectric parameters is demonstrated with an aluminum-doped CrSi2-?-FeSi2 system the composition of which varies from Cr0.1Fe0.9Si2- x Al x to Cr0.9Fe0.1Si2- x Al x ( x = 0.0-0.4). Doping of either phase (CrSi2 and ?-FeSi2) is viewed as a promising way for synthesizing n- and p-type domains inside the same sample.

Solomkin, F. Yu.; Zaitsev, V. K.; Novikov, S. V.; Samunin, A. Yu.; Pshenai-Severin, D. A.; Isachenko, G. N.

2014-08-01

320

Examination of conversion degree of composite insulating materials  

Microsoft Academic Search

Composite insulating materials have their important place in high-voltage insulating technology. The quality and high reliability of electrical devices is much affected by the curing level of these materials. Curing level is quantified by so-called degree of conversion and there are several possibilities how to determine this degree in practice. Attention is given mainly to kinetic analysis based techniques. Kinetic

V. Mentlik; R. Polansky

2007-01-01

321

3D Magnetic Reluctivity Tensor of Soft Magnetic Composite Material  

Microsoft Academic Search

Soft magnetic composite (SMC) materials are particularly suitable for construction of electrical machines with complex structure and 3D magnetic flux. For design and analysis of such 3D flux machines, 3D magnetic properties of the magnetic materials should be properly determined, modeled and applied for calculating the magnetic field distribution, parameters and performance. This paper presents the 3D magnetic property measurement

Y. G. Guo; J. G. Zhu; Z. W. Lin; J. J. Zhong; H. Y. Lu; S. H. Wang

2006-01-01

322

SIMULATION OF DELAMINATION UNDER HIGH CYCLE FATIGUE IN COMPOSITE MATERIALS  

Microsoft Academic Search

Mechanical fatigue, especially high-cycle fatigue, is a common cause of failure of aerospace structures. In laminated composite materials, the fatigue process involves several damage mechanisms that result in the degradation of the material. One of the most important fatigue damage mechanisms is interlaminar damage (delamination), especially in the case of laminated structures devoid of reinforcement in the thickness direction. There

Albert Turon; Josep Costa; Pedro P. Camanho; Carlos G. Davila

323

Polymeric compositions incorporating polyethylene glycol as a phase change material  

DOEpatents

A polymeric composition comprising a polymeric material and polyethylene glycol or end-capped polyethylene glycol as a phase change material, said polyethylene glycol and said end-capped polyethylene glycol having a molecular weight greater than about 400 and a heat of fusion greater than about 30 cal/g; the composition is useful in making molded and/or coated materials such as flooring, tiles, wall panels and the like; paints containing polyethylene glycols or end-capped polyethylene glycols are also disclosed.

Salyer, Ival O. (Dayton, OH); Griffen, Charles W. (Mason, OH)

1989-01-01

324

Composite material fabrication techniques. CRADA final report  

SciTech Connect

This report describes a low cost method of fabricating components for mockups and training simulators used in the transportation industry. This technology was developed jointly by the Oak Ridge National Laboratory (ORNL) and Metters Industries, Incorporated (MI) as part of a Cooperative Research and Development Agreement (CRADA) ORNL94-0288 sponsored by the Department of Energy (DOE) Office of Economic Impace and Diversity Minority Business Technology Transfer Consortium. The technology involves fabricating component replicas from fiberglass/epoxy composites using a resin transfer molding (RTM) process. The original components are used as masters to fabricate the molds. The molding process yields parts that duplicate the significant dimensional requirements of the original component while still parts that duplicate the significant dimensional requirements of the original component while still providing adequate strength and stiffness for use in training simulators. This technology permits MI to overcome an acute shortage in surplus military hardware available to them for use in manufacturing training simulators. In addition, the cost of the molded fiberglass components is expected to be less than that of procuring the original components from the military.

Frame, B J; Paulauskas, F L [Oak Ridge National Lab., TN (United States); Miller, J; Parzych, W [Metters Industries, Inc. (United States)

1996-09-30

325

Biotransformation of an uncured composite material  

NASA Technical Reports Server (NTRS)

The feasibility of biologically degrading prepreg wastes was studied. The work was conducted with the intention of obtaining baseline data that would facilitate the achievement of two long-range goals. These goals are: (1) the biological remediation of the hazardous components in the prepreg wastes, and (2) providing the potential for recycling the prepreg waste fibers. The experiments examined a prepreg that employs an bismaleimide resin system. Initial results demonstrated an obvious deterioration of the prepreg material when incubated with several bacterial strains. The most active cultures were identified as a mixture of 'Bacillus cereus' and 'Pseudomonas sp'. Gas chromatography analyses revealed seven primary compounds in the resin mixture. Biotransformation studies, using the complete prepreg material, demonstrated on obvious loss of all seven organic compounds. Gas chromatography-mass spectrometry analyses resulted in structure assignments for the two primary components of the resin. Both were analogs of Bisphenol A; one being bismaleimide, and the other being Bisphenol A containing a diglycidyl moiety. The 'diglycidyl analog' was purified using thin-layer chromatography and the biotransformation of this compound (at 27 ug/ml bacterial culture) was monitored. After a seven-day incubation, approximately 40% of the organic compound was biotransformed. These results demonstrate the biotransformation of the prepreg resin and indicate that biological remediation of the prepreg wastes is feasible.

Welsh, Clement J.; Glass, Michael J.; Cheslack, Brian; Pryor, Robert; Tran, Duan K.; Bowers-Irons, Gail

1994-01-01

326

A grammatical approach to customization of shape and composite materials  

NASA Astrophysics Data System (ADS)

With the increasing use of composite materials in Mechanical and Aerospace industries, an approach is required to facilitate designing of components using composite materials, while ensuring customization of the shape such a way that multiple design goals for the components are satisfied. Existing design methods may be used in some cases, where the component shape and loadings are simple. While a significant amount of research has been conducted to study the properties of composite materials, little attention has been paid to find out a design approach such that (1) the user requirements in the very general form may be used directly and as the input for the design, (2) the best possible composite material are selected to meet multiple desired functions, and (3) shape variation is analyzed in order to enable mass customization of the design. Thus an approach is required that will be able to handle both the shape and the material in order to design a load bearing component using composite materials. In this research the focus is to develop a design approach that will consider the user requirements for a composite component in its very general form and generate component shape and material details in a systematic order so that the designed component can withstand a given loading condition. Consequently, the Primary Research Question is: How to simultaneously explore shape and composite materials during the design of a product to meet multiple property and functional goals? The wide range of properties, covered by various fiber-matrix combinations, along with their directional property characteristics, maximizes the flexibility of the designers, while designing composite material products. Meeting multiple property goals, however, complicates the design process as both the composite material selection and the component shape formation becomes highly intricate with the loading conditions and a number of matrix calculations needs to be performed to determine theoretical value of composite material properties. A grammar is a formal definition of a language written in transformational form. To address these issues, in this research a grammatical approach is developed that will generate a shape grammar to perform shape optimization, and then incorporate a composite material selection system and loading analysis techniques of Solid Mechanics in order to design load bearing components of irregular shape. The approach will be able to consider the user requirements in the very general text form, convert them to the design requirements for the component, generate optimized shape based on multiple design constraints, perform the complete design work, and generate the component. The major contributions include: (1) generating a shape grammar to represent functions of the load bearing component such a way that mass-customization of shape is possible, (2) developing a composite material customization system in order to satisfy directional property requirements, and (3) introducing a unique laminate design approach in order to satisfy design property requirements at the critical cross-sections locally that can result in highly efficient design compared to conventional design method. Verification of the approach will focus on its application to simultaneously explore shapes and customization of composite materials.

Nandi, Soumitra

327

Anisotropic Layered Absorbers on Cylindrical Structures  

Microsoft Academic Search

A curved structure consisting of an imperfectly conducting circular cylinder coated by any number of coaxial thin anisotropic layers separated by isotroplc regions of different materials is considered. Each thin anisotroplc layer is represented by a sheet with an anisotropic Jump Impedance. Thus, the structure is a generalization to the anisotropic case of Jaumann absorbers on curved surfaces. For a

R. D. Graglia; P. L. E. Uslenghi

1987-01-01

328

The Yeh-Stratton Criterion for Composite Materials  

Microsoft Academic Search

A new criterion for composite failure is proposed based on the Yeh Stratton (Y-S) criterion which is proven to work well for isotropic materials. Since the Y-S criterion requires three yield strengths from simple tension, compression, and torsion tests, the Y-S criterion can be applicable for ductile materials as well as brittle materials with different strengths in tension and compression.

Hsien-Yang Yeh; Chang H. Kim

1994-01-01

329

Measurement of Damping of Composite Materials for Turbomachinery Applications  

NASA Technical Reports Server (NTRS)

The scientific community has felt that ceramic matrix composite (CMC) materials possess more material damping than the superalloys used in the production of rocket engine turbomachinery turbine-end components. The purpose of this NASA/MFSC study is to quantify the damping in CMC's as compared to a typical super-alloy, Inconel 718. It was observed through testing of beam coupons and disk specimens that the CMC's do indeed possess more material damping than the baselined alloy Inconel 718.

Harris, D. L.

1998-01-01

330

Fracture toughness of fibrous composite materials  

NASA Technical Reports Server (NTRS)

Laminates with various proportions of 0 deg, 45 deg, and 90 deg plies were fabricated from T300/5208 and T300/BP-907 graphite/epoxy prepreg tape material. The fracture toughness of each laminate orientation or lay-up was determined by testing center-cracked specimens, and it was also predicted with the general fracture-toughness parameter. The predictions were good except when crack-tip splitting was large, at which time the toughness and strengths tended to be underpredicted. By using predictions, a parametric study was also made of factors that influence fracture toughness. Fiber and matrix properties as well as lay-up were investigated. Without crack-tip splitting, fracture toughness increases in proportion to fiber strength and fiber volume fraction, increases linearly with E(22)/E(11), is largest when the modulus for non-0 deg fibers is greater than that of 0 deg fibers, and is smallest for 0(m)/90(p)(s) lay-ups. (The E(11) and E(22) are Young's moduli of the lamina parallel to and normal to the direction of the fibers, respectively). For a given proportion of 0 deg plies, the most notch-sensitive lay-ups are 0(m)/90(p)(s) and the least sensitive are 0(m)/45(n)(s) and alpha(s). Notch sensitivity increases with the proportion of 0 deg plies and decreases with alpha. Strong, tough matrix materials, which inhibit crack-tip splitting, generally lead to minimum fracture toughness.

Poe, C. C., Jr.

1984-01-01

331

Development of chemical vapor composites, CVC materials. Final report  

SciTech Connect

Industry has a critical need for high-temperature operable ceramic composites that are strong, non-brittle, light weight, and corrosion resistant. Improvements in energy efficiency, reduced emissions and increased productivity can be achieved in many industrial processes with ceramic composites if the reaction temperature and pressure are increased. Ceramic composites offer the potential to meet these material requirements in a variety of industrial applications. However, their use is often restricted by high cost. The Chemical Vapor composite, CVC, process can reduce the high costs and multiple fabrication steps presently required for ceramic fabrication. CVC deposition has the potential to eliminate many difficult processing problems and greatly increase fabrication rates for composites. With CVC, the manufacturing process can control the composites` density, microstructure and composition during growth. The CVC process: can grow or deposit material 100 times faster than conventional techniques; does not require an expensive woven preform to infiltrate; can use high modulus fibers that cannot be woven into a preform; can deposit composites to tolerances of less than 0.025 mm on one surface without further machining.

NONE

1998-10-05

332

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

NASA Technical Reports Server (NTRS)

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.

Herakovich, C. T.

1980-01-01

333

Probabilistic fatigue life prediction of metallic and composite materials  

NASA Astrophysics Data System (ADS)

Fatigue is one of the most common failure modes for engineering structures, such as aircrafts, rotorcrafts and aviation transports. Both metallic materials and composite materials are widely used and affected by fatigue damage. Huge uncertainties arise from material properties, measurement noise, imperfect models, future anticipated loads and environmental conditions. These uncertainties are critical issues for accurate remaining useful life (RUL) prediction for engineering structures in service. Probabilistic fatigue prognosis considering various uncertainties is of great importance for structural safety. The objective of this study is to develop probabilistic fatigue life prediction models for metallic materials and composite materials. A fatigue model based on crack growth analysis and equivalent initial flaw size concept is proposed for metallic materials. Following this, the developed model is extended to include structural geometry effects (notch effect), environmental effects (corroded specimens) and manufacturing effects (shot peening effects). Due to the inhomogeneity and anisotropy, the fatigue model suitable for metallic materials cannot be directly applied to composite materials. A composite fatigue model life prediction is proposed based on a mixed-mode delamination growth model and a stiffness degradation law. After the development of deterministic fatigue models of metallic and composite materials, a general probabilistic life prediction methodology is developed. The proposed methodology combines an efficient Inverse First-Order Reliability Method (IFORM) for the uncertainty propogation in fatigue life prediction. An equivalent stresstransformation has been developed to enhance the computational efficiency under realistic random amplitude loading. A systematical reliability-based maintenance optimization framework is proposed for fatigue risk management and mitigation of engineering structures.

Xiang, Yibing

334

Chemistry and technology of radiation processed composite materials  

NASA Astrophysics Data System (ADS)

Composite materials of synthetics (based on monomers, oligomers and thermoplastics) and of natural polymers (wood and other fibrous cellulosics) prepared by radiation processing, offer valuable structural materials with enhanced coupling forces between the components. The applied polymer chemistry of such composites shows several common features with that of radiation grafting. E.g. the polymerization rate of oligomer-monomer mixtures in wood remains in most cases proportional to the square-root of the initiating dose-rate, just as in the simultaneous grafting, demonstrating that the chain termination kinetics remain regularly bimolecular in the corresponding dose-rate ranges. In the processing experiences of such composites, low dose requirement, easy process-control, and good technical feasibility have been found for composites of wood with oligomer-monomer mixtures, for coconut fibres with unsaturated polyesters and for pretreated wood fibre with polypropylene.

Czvikovszky, T.

335

Simulation of composite material response under dynamic compressive loading  

SciTech Connect

Realistic computer prediction of high-velocity impact and penetration events involving composite materials requires a knowledge of the material behavior under large compressive stresses at high rates of deformation. As an aid to the development of constitutive models for composites under these conditions, methods for numerical simulation of the material response at the microstructural level are being developed. At present, the study is confined to glass fiber/epoxy composites. The technique uses a numerical model of a representative sample of the microstructure with randomly distributed fibers. By subjecting the boundary of this numerical sample to prescribed loading histories, a statistical interpretation allows prediction of the global material response. Because the events at the microstructural scale involve locally large deformation, and because of the constantly changing picture with regard to contact between the fibers, the Eulerian code CTH is used for these calculations. Certain aspects of material failure can also be investigated using this approach. The method allows the mechanical behavior of composite materials to be studied with fewer assumptions about constituent behavior and morphology than typically required in analytical efforts.

Silling, S.A.; Taylor, P.A.

1993-12-31

336

Experimental Investigation of Textile Composite Materials Using Moire Interferometry  

NASA Technical Reports Server (NTRS)

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.

Ifju, Peter G.

1995-01-01

337

Pin bearing evaluation of LTM25 composite materials  

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

338

A physically-based abrasive wear model for composite materials  

SciTech Connect

A simple physically-based model for the abrasive wear of composite materials is presented based on the mechanics and mechanisms associated with sliding wear in soft (ductile) matrix composites containing hard (brittle) reinforcement particles. The model is based on the assumption that any portion of the reinforcement that is removed as wear debris cannot contribute to the wear resistance of the matrix material. The size of this non-contributing portion of the reinforcement is estimated by modeling the three primary wear mechanisms, specifically plowing, interfacial cracking and particle removal. Critical variables describing the role of the reinforcement, such as its relative size and the nature of the matrix/reinforcement interface, are characterized by a single contribution coefficient, C. Predictions are compared with the results of experimental two-body (pin-on drum) abrasive wear tests performed on a model aluminum particulate-reinforced epoxy matrix composite material.

Lee, Gun Y.; Dharan, C.K.H.; Ritchie, Robert O.

2001-05-01

339

Brazing of sheet composite materials with aluminium matrix  

NASA Astrophysics Data System (ADS)

The technique of brazing composite sheets with an aluminum matrix is investigated for Al matrices with either stainless steel or boron fibers. Brazing is compared to other joining techniques, and the relationship between heating and pressure levels is studied by characterizing the joint qualities microscopically. Solder composition is similarly analyzed, and brazing recommendations are given for ranges of joint sizes. Calculations of the temperature fields for the brazing of these composite materials yield specific-heat input data. Optimal brazing modes thus derived for the Al-matrix composites yield joints free of the intermetallide phases that degrade the performance of brazed structures. The tensile strength of the optimized joints is shown to be good relative to the strength of the original composites with Al matrices.

Khorunov, V. F.; Kuchuk-Iatsenko, V. S.; Dykhno, I. S.; Kasatkina, N. V.

340

Simulation of perforation and penetration in metal matrix composite materials using coupled viscoplastic damage model  

Microsoft Academic Search

In the first part of the two companion papers, theoretical formulation of the multiscale micromechanical constitutive model that couples the anisotropic damage mechanism with the viscoplastic deformation is presented. In the second part of these companion papers the numerical simulation of the computational aspects of the theory are elaborated. The perforation and penetration problem of metal matrix composites (MMCs) due

Babur Deliktas; George Z. Voyiadjis; Anthony N. Palazotto

2009-01-01

341

Delamination, durability and damage tolerance of laminated composite materials  

NASA Technical Reports Server (NTRS)

Research exploring the role of delamination on the durability and damage tolerance of advanced composite materials is reviewed. Recent studies on the characterization of composite delamination are summarized. Recent analytical solutions for interlaminar stresses and strain energy release rates associated with common sources of delamination are also reviewed. The role of delamination in low velocity impact, residual compression strength, and in fatigue is highlighted. Delamination is shown to be the common damage mode observed in all of these problems. A Damage Threshold/Fail-safety concept for addressing composite damage tolerance is discussed.

O'Brien, T. K.

1991-01-01

342

Flame-Resistant Composite Materials For Structural Members  

NASA Technical Reports Server (NTRS)

Matrix-fiber composite materials developed for structural members occasionally exposed to hot, corrosive gases. Integral ceramic fabric surface layer essential for resistance to flames and chemicals. Endures high temperature, impedes flame from penetrating to interior, inhibits diffusion of oxygen to interior where it degrades matrix resin, resists attack by chemicals, helps resist erosion, and provides additional strength. In original intended application, composite members replace steel structural members of rocket-launching structures that deteriorate under combined influences of atmosphere, spilled propellants, and rocket exhaust. Composites also attractive for other applications in which corrosion- and fire-resistant structural members needed.

Spears, Richard K.

1995-01-01

343

Fungal degradation of fiber-reinforced composite materials  

NASA Technical Reports Server (NTRS)

As described in a previous report, a fungal consortium isolated from degraded polymeric materials was capable of growth on presterilized coupons of five composites, resulting in deep penetration into the interior of all materials within five weeks. Data describing the utilization of composite constituents as nutrients for the microflora are described in this article. Increased microbial growth was observed when composite extract was incubated with the fungal inoculum at ambient temperatures. Scanning electron microscopic observation of carbon fibers incubated with a naturally developed population of microorganisms showed the formation of bacterial biofilms on the fiber surfaces, suggesting possible utilization of the fiber chemical sizing as carbon and energy sources. Electrochemical impedance spectroscopy was used to monitor the phenomena occurring at the fiber-matrix interfaces. Significant differences were observed between inoculated and sterile panels of the composite materials. A progressive decline in impedance was detected in the inoculated panels. Several reaction steps may be involved in the degradation process. Initial ingress of water into the resin matrix appeared to be followed by degradation of fiber surfaces, and separation of fibers from the resin matrix. This investigation suggested that composite materials are susceptible to microbial attack by providing nutrients for growth.

Gu, J. D.; Lu, C.; Mitchell, R.; Thorp, K.; Crasto, A.

1997-01-01

344

Novel Composite Materials for SOFC Cathode-Interconnect Contact  

SciTech Connect

This report summarized the research efforts and major conclusions of our University Coal Research Project, which focused on developing a new class of electrically-conductive, Cr-blocking, damage-tolerant Ag-perovksite composite materials for the cathode-interconnect contact of intermediate-temperature solid oxide fuel cell (SOFC) stacks. The Ag evaporation rate increased linearly with air flow rate initially and became constant for the air flow rate {ge} {approx} 1.0 cm {center_dot} s{sup -1}. An activation energy of 280 KJ.mol{sup -1} was obtained for Ag evaporation in both air and Ar+5%H{sub 2}+3%H{sub 2}O. The exposure environment had no measurable influence on the Ag evaporation rate as well as its dependence on the gas flow rate, while different surface morphological features were developed after thermal exposure in the oxidizing and reducing environments. Pure Ag is too volatile at the SOFC operating temperature and its evaporation rate needs to be reduced to facilitate its application as the cathode-interconnect contact. Based on extensive evaporation testing, it was found that none of the alloying additions reduced the evaporation rate of Ag over the long-term exposure, except the noble metals Au, Pt, and Pd; however, these noble elements are too expensive to justify their practical use in contact materials. Furthermore, the addition of La{sub 0.8}Sr{sub 0.2}MnO{sub 3} (LSM) into Ag to form a composite material also did not significantly modify the Ag evaporation rate. The Ag-perovskite composites with the perovskite being either (La{sub 0.6}Sr{sub 0.4})(Co{sub 0.8}Fe{sub 0.2})O{sub 3} (LSCF) or LSM were systematically evaluated as the contact material between the ferritic interconnect alloy Crofer 22 APU and the LSM cathode. The area specific resistances (ASRs) of the test specimens were shown to be highly dependent on the volume percentage and the type of the perovskite present in the composite contact material as well as the amount of thermal cycling that the specimens were subjected to during testing. The Ag-LSCF composite contact materials proved more effective in trapping Cr within the contact material and preventing Cr migration into the cathode than the Ag-LSM composites. Ag-perovskite composite contact materials are promising candidates for use in intermediate-temperature SOFC stacks with ferritic stainless steel interconnects due to their ability to maintain acceptably low ASRs while reducing Cr migration into the cathode material.

J. H. Zhu

2009-07-31

345

Application of magnetic abrasive polishing to composite materials  

Microsoft Academic Search

Magnetic abrasive polishing (MAP) is an advanced machining process that can produce smoother surfaces in many material types.\\u000a The present study conducted an experimental assessment of MAP for a newly developed, non-ferrous and aluminum-based composite\\u000a material. A permanent magnet was installed under the workpiece to enhance its magnetic flux density, which had proved insufficient\\u000a for effective MAP. The success of

Tae-Wan Kim; Dae-Min Kang; Jae-Seob Kwak

2010-01-01

346

Inhibition of catalytic oxidation of carbon\\/carbon composite materials  

Microsoft Academic Search

An investigation coupling experimental efforts with computational chemistry analysis was conducted to study the inhibition effects of phosphorous or boron on the oxidation of carbon\\/carbon composite materials catalyzed by potassium or calcium acetate (KAC or CaAC). Commercial aircraft brakes were used, which are exposed during use to K- or Ca-containing runway deicing agents. The reactivity of inhibitor-doped carbon materials was

Xianxian Wu

2002-01-01

347

Polymer composites and porous materials prepared by thermally induced phase separation and polymer-metal hybrid methods  

NASA Astrophysics Data System (ADS)

The primary objective of this research is to investigate the morphological and mechanical properties of composite materials and porous materials prepared by thermally induced phase separation. High melting crystallizable diluents were mixed with polymers so that the phase separation would be induced by the solidification of the diluents upon cooling. Theoretical phase diagrams were calculated using Flory-Huggins solution thermodynamics which show good agreement with the experimental results. Porous materials were prepared by the extraction of the crystallized diluents after cooling the mixtures (hexamethylbenzene/polyethylene and pyrene/polyethylene). Anisotropic structures show strong dependence on the identity of the diluents and the composition of the mixtures. Anisotropic crystal growth of the diluents was studied in terms of thermodynamics and kinetics using DSC, optical microscopy and SEM. Microstructures of the porous materials were explained in terms of supercooling and dendritic solidification. Dual functionality of the crystallizable diluents for composite materials was evaluated using isotactic polypropylene (iPP) and compatible diluents that crystallize upon cooling. The selected diluents form homogeneous mixtures with iPP at high temperature and lower the viscosity (improved processability), which undergo phase separation upon cooling to form solid particles that function as a toughening agent at room temperature. Tensile properties and morphology of the composites showed that organic crystalline particles have the similar effect as rigid particles to increase toughness; de-wetting between the particle and iPP matrix occurs at the early stage of deformation, followed by unhindered plastic flow that consumes significant amount of fracture energy. The effect of the diluents, however, strongly depends on the identity of the diluents that interact with the iPP during solidification step, which was demonstrated by comparing tetrabromobisphenol-A and phthalic anhydride. A simple method to prepare composite surfaces that can change the wettability in response to the temperature change was proposed and evaluated. Composite surfaces prepared by nanoporous alumina templates filled with polymers showed surface morphology and wettability that depend on temperature. This effect is attributed to the significant difference in thermal conductivity and the thermal expansion coefficient between the alumina and the polymers. The reversibility in thermal response depends on the properties of the polymers.

Yoon, Joonsung

348

Mishap risk control for advanced aerospace/composite materials  

NASA Technical Reports Server (NTRS)

Although advanced aerospace materials and advanced composites provide outstanding performance, they also present several unique post-mishap environmental, safety, and health concerns. The purpose of this paper is to provide information on some of the unique hazards and concerns associated with these materials when damaged by fire, explosion, or high-energy impact. Additionally, recommended procedures and precautions are addressed as they pertain to all phases of a composite aircraft mishap response, including fire-fighting, investigation, recovery, clean-up, and guidelines are general in nature and not application-specific. The goal of this project is to provide factual and realistic information which can be used to develop consistent and effective procedures and policies to minimize the potential environmental, safety, and health impacts of a composite aircraft mishap response effort.

Olson, John M.

1994-01-01

349

Ptah-socar fuel-cooled composite materials structure  

NASA Astrophysics Data System (ADS)

One of the key points for the development of dual-mode ramjets operating up to Mach 8 or more is the mastery of fuel-cooled composite materials structures, which are needed, at least, for the combustion chamber. MBDA France and EADS ST have been working on the development of a particular technology for such structures taking advantage of the background of MBDA France in the field of dual-mode ramjet and fuel-cooled structures and of ASTRIUM-EADS ST in the field of high-temperature composite materials. They have developed an innovative technology for advanced monobloc cooled C/C/SiC structures. The paper gives an updated status of the development of Paroi Tissée Application Hypersonique - Simple Operational Composite for Advanced Ramjet (PTAH-SOCAR) technology, including test results, and presents some results obtained during system and demonstrator studies.

Bouchez, M.; Beyer, S.

2009-09-01

350

Dynamically Driven Phase Transformations in Damaged Composite Materials  

SciTech Connect

A model developed for composite materials undergoing dynamicaly driven phase transitions in its constituents has been extended to allow for complex material micro-structure and evolution of damage. In this work, damage is described by interfacial debonding and micro-crack growth. We have applied the analysis to silicon carbide-titanium (SiC-Ti) unidirectional metal matrix composites. In these composites, Ti can undergo a low pressure and temperature solid-solid phase transition. With these extensions we have carried out simulations to study the complex interplay between loading rates, micro-structure, damage, and the thermo-mechanical response of the system as it undergoes a solid-solid phase transitions.

Plohr, JeeYeon N. [Theoretical Division, MS B221, LANL, Los Alamos, NM 87545 (United States); Clements, Brad E.; Addessio, Frank L

2006-07-28

351

Ultrasonic Nondestructive Evaluation Techniques Applied to the Quantitative Characterization of Textile Composite Materials  

NASA Technical Reports Server (NTRS)

In this Progress Report, we describe our recent developments of advanced ultrasonic nondestructive evaluation methods applied to the characterization of anisotropic materials. We present images obtained from experimental measurements of ultrasonic diffraction patterns for a thin woven composite in an immersion setup. In addition, we compare apparent signal loss measurements of the thin woven composite for phase-sensitive and phase-insensitive detection methods. All images of diffraction patterns have been included on the accompanying CD-ROM in the Adobe(Trademark) Portable Document Format (PDF). Due to the extensive amount of data, however, hardcopies of only a small representative selection of the images are included within the printed report. This Progress Report presents experimental results that support successful implementation of single element as well as one and two-dimensional ultrasonic array technologies for the inspection of textile composite structures. In our previous reports, we have addressed issues regarding beam profiles of ultrasonic pressure fields transmitted through a water reference path and transmitted through a thin woven composite sample path. Furthermore, we presented experimental results of the effect of a thin woven composite on the magnitude of an insonifying ultrasonic pressure field. In addition to the study of ultrasonic beam profiles, we consider issues relevant to the application of single-element, one-dimensional, and two-dimensional array technologies towards probing the mechanical properties of advanced engineering composites and structures. We provide comparisons between phase-sensitive and phase-insensitive detection methods for determination of textile composite structure parameters. We also compare phase-sensitive and phase-insensitive - - ---- ----- apparent signal loss measurements in an effort to study the phenomenon of phase cancellation at the face of a finite-aperture single-element receiver. Furthermore, in this Progress Report we extend our work on ultrasonic beam profile issues through investigation of the phase fronts of the pressure field. In Section H of this Progress Report we briefly describe the experimental arrangement and methods for data acquisition of the ultrasonic diffraction patterns upon transmission through a thin woven composite. Section III details the analysis of the experimental data followed by the experimental results in Section IV. Finally, a discussion of the observations and conclusions is found in Section V.

Miller, James G.

1997-01-01

352

INTERNATIONAL CONFERENCE ON COMPOSITE MATERIALS 1. General Introduction  

E-print Network

Framework Directive [5] and the Directive on End Of Life Vehicles [6], thermoplastic CFRP (TP to a patent[9] clearly describing how strip pieces (chips) made of chopped thermoplastic pre FOR THE AEROSPACE WITH DISCONTINUOUS NOVELAND RECYCLED THERMOPLASTIC COMPOSITE MATERIALS N.Eguémann1, 2* , L.Giger1

Boyer, Edmond

353

NASA Composite Materials Development: Lessons Learned and Future Challenges  

NASA Technical Reports Server (NTRS)

Composite materials have emerged as the materials of choice for increasing the performance and reducing the weight and cost of military, general aviation, and transport aircraft and space launch vehicles. Major advancements have been made in the ability to design, fabricate, and analyze large complex aerospace structures. The recent efforts by Boeing and Airbus to incorporate composite into primary load carrying structures of large commercial transports and to certify the airworthiness of these structures is evidence of the significant advancements made in understanding and use of these materials in real world aircraft. NASA has been engaged in research on composites since the late 1960 s and has worked to address many development issues with these materials in an effort to ensure safety, improve performance, and improve affordability of air travel for the public good. This research has ranged from synthesis of advanced resin chemistries to development of mathematical analyses tools to reliably predict the response of built-up structures under combined load conditions. The lessons learned from this research are highlighted with specific examples to illustrate the problems encountered and solutions to these problems. Examples include specific technologies related to environmental effects, processing science, fabrication technologies, nondestructive inspection, damage tolerance, micromechanics, structural mechanics, and residual life prediction. The current state of the technology is reviewed and key issues requiring additional research identified. Also, grand challenges to be solved for expanded use of composites in aero structures are identified.

Tenney, Darrel R.; Davis, John G., Jr.; Pipes, R. Byron; Johnston, Norman

2009-01-01

354

Numerical Simulation of Delamination Growth in Composite Materials  

Microsoft Academic Search

Abstract The use of decohesion elements for the simulation of delamination in composite materials is reviewed The test methods available to measure the interfacial fracture toughness used in the formulation of decohesion elements are described initially After a brief presentation of the virtual crack closure technique, the technique most widely used to simulate delamination growth, the formulation of interfacial decohesion

P. P. Camanho; D. R. Ambur

2001-01-01

355

Development of active and sensitive material systems based on composites  

Microsoft Academic Search

This paper describes new concepts proposed by the author to realize active and sensitive structural material systems. Two examples of multifunctional composites were fabricated and evaluated in this study as follows: (1) An active laminate of aluminum plate (works as muscle), epoxy film (as insulator), unidirectional CFRP prepreg (as bone and blood vessel) and copper foil electrode (to apply voltage

Hiroshi Asanuma

2002-01-01

356

Inspection for kissing bonds in composite materials using vibration measurements  

NASA Astrophysics Data System (ADS)

Improper bonding of composite structures can result in close contact cracks under compressive stresses, called kissing bonds. These bond defects are very difficult to detect using conventional inspection techniques such as tap testing or local ultrasonic scanning and can lead to local propagation of damage if the structure is subjected to crack opening stresses. A method is investigated for identifying kissing bonds in composite material repairs based on vibration measurements. A damage feature of the kissing bond is extracted from the response of the input-output measurement that is a function of the structural path. This path exhibits local decoupling associated with the close contact cracks. Experimental vibration measurements from sandwich composite materials are presented along with the results of the damage detection algorithm for the healthy sections of the material and the kissing bond sections. A vibration based inspection technique could increase the ability to detect kissing bonds in composite material repairs while decreasing inspection time. Benefits of this method of identification over conventional techniques include its robust, objective damage detection methodology and the reduced requirement for specimen preparation and surface texture when compared to ultrasonic scanning.

Adams, Douglas E.; Sharp, Nathan D.; Myrent, Noah; Sterkenburg, Ronald

2011-04-01

357

Characterization of a High Strain Composite Material I. Maqueda  

E-print Network

respectively from the Weibull distribution of the strength of a single fiber combined with a simple bundle no damage, as elastic microbuckling of the fibers acts as a stress relief mechanism that prevents them from and developed a high-strain composite material consisting of car- bon fibers embedded in a silicone matrix

Pellegrino, Sergio

358

Design And Formability Of A New Composite Material  

SciTech Connect

Composite materials with metallic cover sheets have been established based on their low weight potential in industrial applications. Further requirements such as high stiffness of component, vibration damping and formability today are only partially met by these composites. For that reason, in current research work, great efforts are being made to develop materials which can be adapted to their later use and load in terms of improving noise, vibration and harshness. Thus, greater stiffness of component structure with a simultaneous reduction of weight can be achieved. This article presents a new composite material which consists of a plane sheet, a thin intermediate damping-layer and a sheet with formed elements to increase stiffness of component such as beads. The plane side can be used as the visible part side. The shape elements increase strength due to work hardening and can be used as design or functional elements. Thus, this composite material results in several advantages within the single layers. Possible flexibility in component design enables new semi-finished or tailored components.

Bolay, C.; Liewald, M. [Institute for Metal Forming Technology (IFU)-Holzgartenstr. 17, 70174 Stuttgart (Germany)

2011-05-04

359

Review of probabilistic models of the strength of composite materials  

Microsoft Academic Search

The available literature concerning probabilistic models describing the strength of composite materials has been reviewed to highlight the important aspects of this behaviour which will be of interest to the modelling and analysis of a complex system. The success with which these theories have been used to predict experimental results has been discussed. Since the brittle reinforcement phase largely controls

L. S. Sutherland; C. Guedes Soares

1997-01-01

360

Recycling By Solvolysis Thermosetting Composite Materials Of Sustainable Surface Transport  

Microsoft Academic Search

A solvolysis process is studied to degrade an unsaturated polyester resin based on DCPD (dicyclopentadiene) and crosslinked with styrene, as the matrix of a composite material reinforced with long glass fibers. The study presented here investigates in particular the hydrolysis in conditions below the critical point of water (T<374° C and P<221bar) in a batch reactor. Process window and parameter

Géraldine Oliveux; Eric Le Gal La Salle; Jean-Luc Bailleul

2011-01-01

361

Fractography of modern engineering materials: Composites and metals, Second volume  

SciTech Connect

This book contains the manuscripts of eleven papers that were presented at the Second Symposium on Fractography of Modern Engineering Materials held in May 1992. The numerous advances in materials science in the six year period following the First Symposium dictated this second meeting. Not only had new materials been developed in the intervening years, but understanding of older materials had also progressed. Similarly, advances in the technology and the techniques of fractography had occurred. The objective of the symposium was to extend the colloquy on fractography to include these many advances. The paper may be divided into three sections: Unique Fractographic Techniques; Metallic Materials; Polymeric and Composite Materials. The section titles reflect the diversity of materials discussed in the meeting. The range of materials included cross-linked polyethylene, AISI 52100 steel, 2024 aluminum, and a variety of organic and metal matrix fibrous composites. The case studies presented also covered a wide range. They included failure investigations of an antenna used in deep space exploration and chemical storage tanks. Advances in the techniques of fractography were also reflected in a number of presentations; quantitative techniques and expert systems were also subjects of presentations. A short precis of each paper is included here to assist the readers in identifying works of particular interest.

Masters, J.E.; Gilbertson, L.N. (eds.)

1993-01-01

362

Surface composites: A new class of engineered materials Rajiv Singh and James Fitz-Gerald  

E-print Network

are different from existing engineered materials such as "bulk composites" and "functionally graded materials, such that the phase composition is linearly graded as a function of distance from the surface. Surface composites composites and func- tionally graded materials (FGM) have been developed to combine desirable materials

Fitz-Gerald, James M.

363

A method of two-scale analysis with micro-macro decoupling scheme: application to hyperelastic composite materials  

NASA Astrophysics Data System (ADS)

The aim of this study is to propose a strategy for performing nonlinear two-scale analysis for composite materials with periodic microstructures (unit cells), based on the assumption that a functional form of the macroscopic constitutive equation is available. In order to solve the two-scale boundary value problems (BVP) derived within the framework of the homogenization theory, we employ a class of the micro-macro decoupling scheme, in which a series of numerical material tests (NMTs) is conducted on the unit cell model to obtain the data used for the identification of the material parameters in the assumed constitutive model. For the NMTs with arbitrary patterns of macro-scale loading, we propose an extended system of the governing equations for the micro-scale BVP, which is equipped with the external material points or, in the FEM, control nodes. Taking an anisotropic hyperelastic constitutive model for fiber-reinforced composites as an example of the assumed macroscopic material behavior, we introduce a tensor-based method of parameter identification with the ‘measured’ data in the NMTs. Once the macro-scale material behavior is successfully fitted with the identified parameters, the macro-scale analysis can be performed, and, as may be necessary, the macro-scale deformation history at any point in the macro-structure can be applied to the unit cell to evaluate the actual micro-scale response.

Terada, K.; Kato, J.; Hirayama, N.; Inugai, T.; Yamamoto, K.

2013-11-01

364

Predictors of clinical wear of restorative dental composite materials.  

PubMed

The mode-I plane-strain fracture toughness values of eight posterior restorative composite materials were determined using straight-sided chevron-notch short-rod specimens and a special loading module. These results, together with the values of the modulus of elasticity, modulus of resilience, and flexural strength of these materials (as given in a paper by a previous worker) were used in a detailed correlational exercise, with the values of the clinical wear of restorations made from these materials (as given in the aforementioned paper) being the dependent variable. It was found that clinical wear may best be predicted using values of all four aforementioned mechanical properties. PMID:8193568

Lewis, G

1993-01-01

365

Strength criteria for composite materials (a literature survey)  

NASA Technical Reports Server (NTRS)

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.

Roode, F.

1982-01-01

366

Future trends in advanced fibers and composite materials technology  

SciTech Connect

By drawing on the wealth of new knowledge in advanced materials, bioscience, and information science, advanced fiber and composite systems are entering a new phase of development. Advances in the understanding of structure/property relationships of materials and related processing technologies have made it possible to tailor-make new material systems, molecule by molecule, to meet specific engineering needs better than metals. The theoretical limits for strength and stiffness of fibers can be predicted based on bond strength and cohesive forces. In the future, fiber technology will continue to advance toward achieving fiber properties closer to theoretical, increasing chemical stability, and developing new product forms tailored for specific engineering needs. The development of tailored high performance fibers and resins systems combined with advances in enabling technologies will provide most efficient solutions to engineering problems. In the future, self-monitoring and self-correcting ``smart`` composite systems will not only sense their structural environment but also respond to prevent structural failures. Just as man-made fibers revolutionized what people wear, man-made composite material systems will revolutionize how people design and build structural material systems.

Dhingra, A.K.; Doherty, T.P. [DuPont, Wilmington, DE (United States)

1993-12-31

367

Investigation of low velocity impact damage on filamentary composite materials  

NASA Technical Reports Server (NTRS)

Presented are the results of an investigation of the effect of low velocity impact on the residual modulus and residual strength of flat filamentary composite materials. Theoretical analysis of composite materials indicates that the modulus of the material must decrease as impact damage increases. This decrease must also correlate to the decrease in residual strength. This study attempts to verify these hypotheses. Graphite/epoxy laminates (AS4/3501-6) of various fiber orientations (8 (0 deg), 2 (+ or - 45 deg)sub 8) were impacted using a falling weight impact tester. Impact energies ranged from 0.42 to 1.55 ft-lb, with impact velocities from 2.03 to 3.98 ft/sec. The results show that there is a reduction in residual modulus of the plate as the impact energy increases.

Bower, Mark V.

1987-01-01

368

High resolution computed tomography of advanced composite and ceramic materials  

NASA Technical Reports Server (NTRS)

Advanced composite and ceramic materials are being developed for use in many new defense and commercial applications. In order to achieve the desired mechanical properties of these materials, the structural elements must be carefully analyzed and engineered. A study was conducted to evaluate the use of high resolution computed tomography (CT) as a macrostructural analysis tool for advanced composite and ceramic materials. Several samples were scanned using a laboratory high resolution CT scanner. Samples were also destructively analyzed at the locations of the scans and the nondestructive and destructive results were compared. The study provides useful information outlining the strengths and limitations of this technique and the prospects for further research in this area.

Yancey, R. N.; Klima, S. J.

1991-01-01

369

Endogenous plastic composite material in the Alzheimer's brain.  

PubMed

Accumulation of amyloid beta (Abeta) peptide in brain is the hallmark of Alzheimer's disease (AD). The resulting plaques though fibrous in nature may also consist of additional structures currently poorly defined. We hypothesize that plastic composite material contributes to plaque formation. This material is organized by polymers of acrolein, which is an oxidized lipid fragment found in AD. Acrolein, a 3-carbon compound, contains a carbonyl and a vinyl group that participate in polymerization via fundamental latex chemistry. The redox and surfactant properties of Abeta allow it to catalyze the polymerization of acrolein. We previously reported observations of thin plastic fragments of Abeta-polyacrolein. The current paper outlines the proposed steps in forming these plastic fragments. Endogenous plastic composite material may significantly contribute to the pathogenesis of AD. PMID:16678976

Seidler, N W; Craig, H D; Squire, T J

2006-01-01

370

A general methodology for inverse estimation of the elastic and anelastic properties of anisotropic open-cell porous materials—with application to a melamine foam  

NASA Astrophysics Data System (ADS)

This paper proposes an inverse estimation method for the characterisation of the elastic and anelastic properties of the frame of anisotropic open-cell foams used for sound absorption. A model of viscoelasticity based on a fractional differential constitutive equation is used, leading to an augmented Hooke's law in the frequency domain, where the elastic and anelastic phenomena appear as distinctive terms in the stiffness matrix. The parameters of the model are nine orthotropic elastic moduli, three angles of orientation of the material principal directions and three parameters governing the anelastic frequency dependence. The inverse estimation consists in numerically fitting the model on a set of transfer functions extracted from a sample of material. The setup uses a seismic-mass measurement repeated in the three directions of space and is placed in a vacuum chamber in order to remove the air from the pores of the sample. The method allows to reconstruct the full frequency-dependent complex stiffness matrix of the frame of an anisotropic open-cell foam and in particular it provides the frequency of maximum energy dissipation by viscoelastic effects. The characterisation of a melamine foam sample is performed and the relation between the fractional-derivative model and other types of parameterisations of the augmented Hooke's law is discussed.

Cuenca, Jacques; Van der Kelen, Christophe; Göransson, Peter

2014-02-01

371

Materials and processes laboratory composite materials characterization task, part 1. Damage tolerance  

NASA Technical Reports Server (NTRS)

A test run was performed on IM6/3501-6 carbon-epoxy in which the material was processed, machined into specimens, and tested for damage tolerance capabilities. Nondestructive test data played a major role in this element of composite characterization. A time chart was produced showing the time the composite material spent within each Branch or Division in order to identify those areas which produce a long turnaround time. Instrumented drop weight testing was performed on the specimens with nondestructive evaluation being performed before and after the impacts. Destructive testing in the form of cross-sectional photomicrography and compression-after-impact testing were used. Results show that the processing and machining steps needed to be performed more rapidly if data on composite material is to be collected within a reasonable timeframe. The results of the damage tolerance testing showed that IM6/3501-6 is a brittle material that is very susceptible to impact damage.

Nettles, A. T.; Tucker, D. S.; Patterson, W. J.; Franklin, S. W.; Gordon, G. H.; Hart, L.; Hodge, A. J.; Lance, D. G.; Russel, S. S.

1991-01-01

372

Stress and Damage in Polymer Matrix Composite Materials Due to Material Degradation at High Temperatures  

NASA Technical Reports Server (NTRS)

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.

McManus, Hugh L.; Chamis, Christos C.

1996-01-01

373

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

Microsoft Academic Search

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

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

2003-01-01

374

A Study of Failure Criteria of Fibrous Composite Materials  

NASA Technical Reports Server (NTRS)

The research described in this paper is focused on two areas: (1) evaluation of existing composite failure criteria in the nonlinear, explicit transient dynamic finite element code, MSC.Dytran, and (2) exploration of the possibilities for modification of material and failure models to account for large deformations, progressive failure, and interaction of damage accumulation with stress/strain response of laminated composites. Following a review of the MSC.Dytran user manual, a bibliographical review of existing failure criteria of composites was performed. The papers considered most interesting for the objective of this report are discussed in section 2. The failure criteria included in the code under consideration are discussed in section 3. A critical summary of the present procedures to perform analysis and design of composites is presented in section 4. A study of the most important historical failure criteria for fibrous composite materials and some of the more recent modifications proposed were studied. The result of this analysis highlighted inadequacies in the existing failure criteria and the need to perform some numerical analyses to elucidate the answer to questions on which some of the proposed criteria are based. A summary of these ideas, which is a proposal of studies to be developed, is presented in section 5. Finally, some ideas for future developments are summarized in section 6.

Paris, Federico; Jackson, Karen E. (Technical Monitor)

2001-01-01

375

Dual-nanoparticulate-reinforced aluminum matrix composite materials  

NASA Astrophysics Data System (ADS)

Aluminum (Al) matrix composite materials reinforced with carbon nanotubes (CNT) and silicon carbide nanoparticles (nano-SiC) were fabricated by mechanical ball milling, followed by hot-pressing. Nano-SiC was used as an active mixing agent for dispersing the CNTs in the Al powder. The hardness of the produced composites was dramatically increased, up to eight times higher than bulk pure Al, by increasing the amount of nano-SiC particles. A small quantity of aluminum carbide (Al4C3) was observed by TEM analysis and quantified using x-ray diffraction. The composite with the highest hardness values contained some nanosized Al4C3. Along with the CNT and the nano-SiC, Al4C3 also seemed to play a role in the enhanced hardness of the composites. The high energy milling process seems to lead to a homogeneous dispersion of the high aspect ratio CNTs, and of the nearly spherical nano-SiC particles in the Al matrix. This powder metallurgical approach could also be applied to other nanoreinforced composites, such as ceramics or complex matrix materials.

Kwon, Hansang; Cho, Seungchan; Leparoux, Marc; Kawasaki, Akira

2012-06-01

376

Test Report: Direct and Indirect Lightning Effects on Composite Materials  

NASA Technical Reports Server (NTRS)

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.

Evans, R. W.

1997-01-01

377

Elastoplastic analysis of thermal cycling: Layered materials with compositional gradients  

SciTech Connect

Elastoplastic analyses are presented for the cyclic thermal response in multi-layered materials which comprise layers of fixed compositions of a metal and a ceramic, and a compositionally graded interface. Analytical solutions for the characteristic temperature at which the onset of thermally induced plastic deformation occurs are derived for the layered composite. Solutions for the evolution of curvature and thermal strains, and for the initiation of plastic yielding are also obtained for different combinations of the geometry, physical properties and compositional gradation for both thermoelastic and thermoplastic deformation. Finite-element formulations incorporating continuous and smooth spatial variations in the composition and properties of the graded layer are used to simulate the evolution of thermal stresses, the accumulation of plastic strains, and the development of monotonic and cyclic plastic zones at the interfaces, edges and free surfaces of different layers during thermal cycling. Engineering diagrams detailing the effects of compositional gradients are also presented for optimizing thermal residual stresses, layer geometry, and plastic strain accumulation.

Giannakopulos, A.E.; Olsson, M. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Solid Mechanics] [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Solid Mechanics; Suresh, S.; Finot, M. [Massachusetts Inst. of Tech., Cambridge, MA (United States)] [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1995-04-01

378

Material and structural studies of metal and polymer matrix composites  

NASA Technical Reports Server (NTRS)

Fiber-reinforced composites and design analysis methods for these materials are being developed because of the vast potential of composites for decreasing weight and/or increasing use temperature capability in aerospace systems. These composites have potential for use in airbreathing engine components as well as aeronautical and space vehicle structures. Refractory wire-superalloy composites for use up to 2200 F or more and metal-matrix composites for lower temperature applications such as aerospace structures and turbojet fan and compressor blades are under investigation and are discussed. The development of a number of resin systems, including the polyimides and polyphenylquinoxalines, is described and their potential for use at temperatures approaching 315 C (600 F) is indicated. Various molecular modifications that improve processability and/or increase thermal and oxidative resistance of the resins are also described. Structural analysis methods are discussed for determining the stresses and deformations in complex composite systems. Consideration is also given to residual stresses resulting from the curing process and to the foreign object damage problem in fan blade applications.

Signorelli, R. A.; Serafini, T. T.; Johns, R. H.

1973-01-01

379

The mechanics of delamination in fiber-reinforced composite materials. II - The delamination behavior and fracture mechanics parameters  

NASA Technical Reports Server (NTRS)

Based on theories of laminate anisotropic elasticity and interlaminar fracture, the complete solution structure associated with a composite delamination is determined. Fracture mechanics parameters characterizing the interlaminar crack behavior are defined from asymptotic stress solutions for delaminations with different crack-tip deformation configurations. A numerical method employing singular finite elements is developed to study delaminations in fiber composites with any arbitrary combinations of lamination, material, geometric, and crack variables. The special finite elements include the exact delamination stress singularity in its formulation. The method is shown to be computationally accurate and efficient, and operationally simple. To illustrate the basic nature of composite delamination, solutions are shown for edge-delaminated (0/-0/-0/0) and (+ or - 0/+ or - 0/90/90 deg) graphite-epoxy systems under uniform axial extension. Three-dimensional crack-tip stress intensity factors, associated energy release rates, and delamination crack-closure are determined for each individual case. The basic mechanics and mechanisms of composite delamination are studied, and fundamental characteristics unique to recently proposed tests for interlaminar fracture toughness of fiber composite laminates are examined. Previously announced in STAR as N84-13222

Wang, S. S.; Choi, I.

1983-01-01

380

The mechanics of delamination in fiber-reinforced composite materials. Part 2: Delamination behavior and fracture mechanics parameters  

NASA Technical Reports Server (NTRS)

Based on theories of laminate anisotropic elasticity and interlaminar fracture, the complete solution structure associated with a composite delamination is determined. Fracture mechanics parameters characterizing the interlaminar crack behavior are defined from asymptotic stress solutions for delaminations with different crack-tip deformation configurations. A numerical method employing singular finite elements is developed to study delaminations in fiber composites with any arbitrary combinations of lamination, material, geometric, and crack variables. The special finite elements include the exact delamination stress singularity in its formulation. The method is shown to be computationally accurate and efficient, and operationally simple. To illustrate the basic nature of composite delamination, solutions are shown for edge-delaminated (0/-0/-0/0) and (+ or - 0/+ or - 0/90/90 deg) graphite-epoxy systems under uniform axial extenstion. Three-dimensional crack-tip stress intensity factors, associated energy release rates, and delamination crack-closure are determined for each individual case. The basic mechanics and mechanisms of composite delamination are studied, and fundamental characteristics unique to recently proposed tests for interlaminar fracture toughness of fiber composite laminates are examined.

Wang, S. S.; Choi, I.

1983-01-01

381

The percolation staircase model and its manifestation in composite materials  

NASA Astrophysics Data System (ADS)

We studied the tunneling percolation conductivity dependence on the site or bond occupation probability in the square lattice. The model predicts that in both, lattice and continuum systems in which there is a hierarchy of the local conductances, the dependence of the global conductivity on the site or volume occupation probability will yield a conductivity staircase. In particular we evaluate the implications of the staircase on the critical behavior of the conductivity. We then show experimental evidence for the predicted percolation-tunneling staircase in a Ag-Al2O3 granular metal system and in a carbon black-polymer composite. Following that, we propose that for carbon nanotube (CNT) polymer composites the data in the literature give ample support to a percolation-dispersion staircase behavior. The implication of the present findings on the percolation-hopping problem in composite materials is also discussed.

Balberg, I.; Azulay, D.; Goldstein, Y.; Jedrzejewski, J.; Ravid, G.; Savir, E.

2013-10-01

382

Compendium of Material Composition Data for Radiation Transport Modeling  

SciTech Connect

Introduction Meaningful simulations of radiation transport applications require realistic definitions of material composition and densities. When seeking that information for applications in fields such as homeland security, radiation shielding and protection, and criticality safety, researchers usually encounter a variety of materials for which elemental compositions are not readily available or densities are not defined. Publication of the Compendium of Material Composition Data for Radiation Transport Modeling, Revision 0, in 2006 was the first step toward mitigating this problem. Revision 0 of this document listed 121 materials, selected mostly from the combined personal libraries of staff at the Pacific Northwest National Laboratory (PNNL), and thus had a scope that was recognized at the time to be limited. Nevertheless, its creation did provide a well-referenced source of some unique or hard-to-define material data in a format that could be used directly in radiation transport calculations being performed at PNNL. Moreover, having a single common set of material definitions also helped to standardize at least one aspect of the various modeling efforts across the laboratory by providing separate researchers the ability to compare different model results using a common basis of materials. The authors of the 2006 compendium understood that, depending on its use and feedback, the compendium would need to be revised to correct errors or inconsistencies in the data for the original 121 materials, as well as to increase (per users suggestions) the number of materials listed. This 2010 revision of the compendium has accomplished both of those objectives. The most obvious change is the increased number of materials from 121 to 372. The not-so-obvious change is the mechanism used to produce the data listed here. The data listed in the 2006 document were compiled, evaluated, entered, and error-checked by a group of individuals essentially by hand, providing no library file or mechanism for revising the data in a consistent and traceable manner. The authors of this revision have addressed that problem by first compiling all of the information (i.e., numbers and references) for all the materials into a single database, maintained at PNNL, that was then used as the basis for this document.

McConn, Ronald J.; Gesh, Christopher J.; Pagh, Richard T.; Rucker, Robert A.; Williams III, Robert

2011-03-04

383

Degradation of experimental composite materials and in vitro wear simulation  

NASA Astrophysics Data System (ADS)

The material, mechanical, and clinical aspects of surface degradation of resin composite dental restorative materials by in vitro wear simulation continues to be an area of active research. To investigate wear mechanisms, a series of experimental resin composites with variable and controlled filler particle shape and loading were studied by in vitro wear simulation. The current investigation utilized a simulation that isolated the wear environment, entrapped high and low modulus debris, and evaluated the process including machine and fluid flow dynamics. The degradation was significantly affected by filler particle shape and less by particle loading. The spherical particle composites demonstrated wear loss profiles suggesting an optimized filler loading may exist. This was also demonstrated by the trends in the mechanical properties. Very little difference in magnitude was noted for the wear of irregular particle composites as a function of particulate size; and as a group they were more wear resistant than spherical particle composites. This was the result of different mechanisms of wear that were correlated with the three-dimensional particle shape. The abrasive effects of the aggregate particles and the polymeric stabilization of the irregular shape versus the destabilization and "plucking" of the spherical particles resulted in an unprotected matrix that accounted for significantly greater wear of spherical composite. A model and analysis was developed to explain the events associated with the progressive material wear loss. The initial phase was explained by fatigue-assisted microcracking and loss of material segments in a zone of high stress immediately beneath a point of high stress contact. The early phase was characterized by the development of a small facet primarily by fatigue-assisted microcracking. Although the translation effects were minimal, some three-body and initial two-body wear events were also present. In the late phases, the abrasive effects of the debris aggregate predominated the wear process. The non-linear rate of wear loss was accelerated as the facet deepened. Physical effects, such as thermal fatigue, and chemical effects were less important but contributed to the degradation process. This study provides new insight into the role(s) of high modulus third body debris in the wear of dental composites.

Givan, Daniel Allen

2001-12-01

384

Ultrasonic Characterization of Fatigue Cracks in Composite Materials  

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

385

DOE/MSU composite material fatigue database: Test methods, materials, and analysis  

SciTech Connect

This report presents a detailed analysis of the results from fatigue studies of wind turbine blade composite materials carried out at Montana State University (MSU) over the last seven years. It is intended to be used in conjunction with the DOE/MSU composite Materials Fatigue Database. The fatigue testing of composite materials requires the adaptation of standard test methods to the particular composite structure of concern. The stranded fabric E-glass reinforcement used by many blade manufacturers has required the development of several test modifications to obtain valid test data for materials with particular reinforcement details, over the required range of tensile and compressive loadings. Additionally, a novel testing approach to high frequency (100 Hz) testing for high cycle fatigue using minicoupons has been developed and validated. The database for standard coupon tests now includes over 4,100 data points for over 110 materials systems. The report analyzes the database for trends and transitions in static and fatigue behavior with various materials parameters. Parameters explored are reinforcement fabric architecture, fiber content, content of fibers oriented in the load direction, matrix material, and loading parameters (tension, compression, and reversed loading). Significant transitions from good fatigue resistance to poor fatigue resistance are evident in the range of materials currently used in many blades. A preliminary evaluation of knockdowns for selected structural details is also presented. The high frequency database provides a significant set of data for various loading conditions in the longitudinal and transverse directions of unidirectional composites out to 10{sup 8} cycles. The results are expressed in stress and strain based Goodman Diagrams suitable for design. A discussion is provided to guide the user of the database in its application to blade design.

Mandell, J.F.; Samborsky, D.D. [Montana State Univ., Bozeman, MT (United States). Dept. of Chemical Engineering

1997-12-01

386

Carbonization of wood at 400°C for composite materials  

NASA Astrophysics Data System (ADS)

The carbonization process for large pieces of wood was investigated to produce a solid carbonized wood skeleton precursor that retains the cellular structure of the wood without the formation of cracks and with reduced longitudinal deformation. Two carbonization schedules were designed for the conversion of sugar maple (Acer saccharum) and southern pine ( Pinus spp) into amorphous carbon at a heat treatment temperature of 400°C. Samples from commercial lumber were carbonized to produce the materials. Each schedule was designed meticulously through DTA-TGA for each wood species. The materials were characterized by their average yields, dimensional changes, density, porosity, SEM and mechanical testing. Also, the materials were used as solid carbon skeletons for making resin-infused carbon composites. Structural epoxy resin was infused into the carbon material template and cured at a maximum temperature of 125°C. The depth of the resin infusion was assessed by SEM examination and the retention was analyzed by total weight gain. The strength and the stiffness of the composite materials were evaluated through mechanical testing. It was demonstrated that southern pine and sugar maple should require different heat treatment schedules for carbonization. The schedules were able to reduce the longitudinal deformation and to keep the final products free of cracks. The yield averaged around 28% for both southern pine and sugar maple. Carbonized southern pine exhibited lower density and higher porosity than carbonized sugar maple. The resin treatment increased specific gravity of carbonized materials by 9.6% and 11.6% for maple and southern pine respectively. The resin infusion improved the average MOR values by 140% and 275%. MOE of the composites was similar to that of pure epoxy.

Randrianarisoa, Bernard Laurent

387

Magnetic sensor for high temperature using a laminate composite of magnetostrictive material and piezoelectric material  

NASA Astrophysics Data System (ADS)

A high sensitive and heat-resistive magnetic sensor using a magnetostrictive/piezoelectric laminate composite is investigated. The sensing principle is based on the magnetostrictive- and piezoelectric effect, whereby a detected yoke displacement is transduced into a voltage on the piezoelectric materials. The sensor is intended to detect the displacement of a ferromagnetic object in a high temperature environment, where conventional magnetic sensors are not useful. Such applications include sensors in engine of automobile and machinery used in material processing. The sensor features combination of a laminate composite of magnetostrictive/piezoelectric materials with high Curie temperatures and an appropriate magnetic circuit to convert mechanical displacement to sensor voltages and suppress temperature fluctuation. This paper describes the sensing principle and shows experimental results using a composite of Terfenol-D and Lithium Niobate to assure high sensitivity of 50V/mm at bias gap of 0.1mm and a temperature operating range over 200 °C.

Ueno, Toshiyuki; Higuchi, Toshiro

2005-05-01

388

Flight simulation testing equipment for composite material systems  

NASA Technical Reports Server (NTRS)

A test program is discussed which aims at establishing the time-temperature-stress characteristics of several classes of high-temperature composite materials in order to determine their suitability for applications in supersonic cruise aircraft. Five advanced composite materials (a boron epoxy, a boron polyimide, a graphite epoxy, a graphite polyimide, and diffusion-bonded boron aluminum) are being evaluated using a flight-test simulator capable of long-term automatic testing based on random loading and realistic flight temperature profiles. The design, construction, and checkout of this simulator are described along with the digital load programmer, load magnitude controllers, the hydraulic pumping system, the heating and cooling systems, the control console, and the data recording system. Typical results for short-term tests performed at constant temperatures and accelerated load rates are presented in terms of a random-load spectrum and a wearout model.

Haskins, J. F.; Wilkins, D. J.; Stein, B. A.

1976-01-01

389

The dynamic inelastic behavior in fiber reinforced composite materials  

SciTech Connect

Accurately simulating the complete dynamic behavior, elastic and inelastic, of engineering structures composed of fiber reinforced composite materials can be accomplished by integrating three components: (1) a physically based micromechanical material model that accounts for the experimentally observed mechanisms producing the inelastic behavior; (2) a dynamic three-dimensional continuum simulation capability in which the physically based micromechanical material model is incorporated; and (3) a complete set of robust dynamic experiments. These experiments are used (1) to establish the microstructural mechanisms that produce inelastic behavior and (2) to validate the dynamic simulation capability. This paper focuses on the implementation of a physically based micromechanical material model into an explicit 3D finite element code and shows the experimental comparison.

Haberman, K.S.; Bennett, J.G.; Liu, Cheng [and others

1997-03-01

390

Intermetallic and titanium matrix composite materials for hypersonic applications  

SciTech Connect

As part of the French Program of Research and Technology for Advanced Hypersonic Propulsion (PREPHA) which was launched in 1992 between Aerospatiale, Dassault Aviation, ONERA, SNECMA and SEP, an important work is specially devoted to the development of titanium and intermetallic composite materials for large airframe structures. At Dassault Aviation, starting from a long experience in Superplastic Forming - Diffusion Bonding (SPF-DB) of titanium parts, the effort is brought on the manufacturing and characterization of composites made from Timet beta 21S or IMI 834 foils and Textron SCS6 fiber fabrics. At `Aersopatiale Espace & Defence`, associated since a long time about intermetallic composite materials with university research laboratories, the principal effort is brought on plasma technology to develop the gamma titanium aluminide TiAl matrix composite reinforced by protected silicon carbide fibers (BP SM 1240 or TEXTRON SCS6). The objective, is to achieve, after 3 years of time, to elaborate a medium size integrally stiffened panel (300 x 600 sq mm).

Berton, B.; Surdon, G.; Colin, C. [Dassault Aviation, Saint-Cloud (France)]|[Aersopatiale Space & Defence, St Medard en Jalles (France)

1995-09-01

391

Conducting polymer composite materials for smart microwave windows  

NASA Astrophysics Data System (ADS)

Samples of poly(aniline)-silver-polymer electrolyte particulate composites have been characterized at microwave frequencies when small d.c. electric fields are applied across them in both coaxial line and waveguide measurement test sets. The experimental data shows that the initial conductivity of the materials is dependent on the concentration of sliver metal and suggest that changes in resistance due to chemical switching take place, at least in part, in the manufacture of the composites. When silver is used as the electrodes, the experimental data show that changes in the slope of the cyclic voltammograms coincide with large changes in microwave reflectivity or transmission consistent with increasing conductivity of the composites when fields are applied. The reverse change occurs when the fields are removed. Measurements have shown that the composites are able to switch between the two impedance stats in times of less than one second for well over a million cycles with no apparent depreciation in material properties. Large area films have also been prepared and studied using the 'free space' technique.

Barnes, Alan; Lees, K.; Wright, Peter V.; Chambers, Barry

1999-07-01

392

Materials and Process Activities for NASA's Composite Crew Module  

NASA Technical Reports Server (NTRS)

In January 2007, the NASA Administrator and Associate Administrator for the Exploration Systems Mission Directorate chartered the NASA Engineering and Safety Center (NESC) to design, build, and test a full-scale Composite Crew Module (CCM). The overall goal of the CCM 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. The materials and process activities were prioritized based on a rapid prototype approach. This approach focused developmental activities on design details with greater risk and uncertainty, such as out-of-autoclave joining, over some of the more traditional lamina and laminate building block levels. While process development and associated building block testing were performed, several anomalies were still observed at the full-scale level due to interactions between process robustness and manufacturing scale-up. This paper describes the process anomalies that were encountered during the CCM development and the subsequent root cause investigations that led to the final design solutions. These investigations highlight the importance of full-scale developmental work early in the schedule of a complex composite design/build project.

Polis, Daniel L.

2012-01-01

393

Probability techniques for reliability analysis of composite materials  

NASA Technical Reports Server (NTRS)

Traditional design approaches for composite materials have employed deterministic criteria for failure analysis. New approaches are required to predict the reliability of composite structures since strengths and stresses may be random variables. This report will examine and compare methods used to evaluate the reliability of composite laminae. The two types of methods that will be evaluated are fast probability integration (FPI) methods and Monte Carlo methods. In these methods, reliability is formulated as the probability that an explicit function of random variables is less than a given constant. Using failure criteria developed for composite materials, a function of design variables can be generated which defines a 'failure surface' in probability space. A number of methods are available to evaluate the integration over the probability space bounded by this surface; this integration delivers the required reliability. The methods which will be evaluated are: the first order, second moment FPI methods; second order, second moment FPI methods; the simple Monte Carlo; and an advanced Monte Carlo technique which utilizes importance sampling. The methods are compared for accuracy, efficiency, and for the conservativism of the reliability estimation. The methodology involved in determining the sensitivity of the reliability estimate to the design variables (strength distributions) and importance factors is also presented.

Wetherhold, Robert C.; Ucci, Anthony M.

1994-01-01

394

Characterization of carbon fiber composite materials for RF applications  

NASA Astrophysics Data System (ADS)

Carbon Fiber Composite (CFC) materials have been used for decades in the aerospace, automotive, and naval industries. They have often been used because of their mechanical advantages. These advantageous characteristics have typically included low weight and high strength. It is also a benefit that CFC materials can be made into nearly any shape or size. With the abundant use of CFC materials, it seems desirable to better under- stand the electromagnetic applications of these materials. CFC materials consist of a non-conductive resin or epoxy in addition to conductive carbon fibers. The carbon fibers can be oriented and layered in many different configurations. The specific orientation and layering of the carbon fibers has a direct impact on its electrical characteristics. One specific characteristic of interest is the conductivity of CFC materials. The work in this paper deals with probing the conductivity characteristics of CFC materials for applications in antenna and radar design. Multiple layouts of carbon fiber are investigated. The DC conductivity was measured by applying a conductive epoxy to sample edges and using a milliohm meter. Shielding effectiveness was then predicted based on fundamental electromagnetics for conducting media. Finally, prototype dipole antennas made from CFC materials were investigated.

Riley, Elliot J.; Lenzing, Erik H.; Narayanan, Ram M.

2014-05-01

395

Nanocrystal-Based Polymer Composites as Novel Functional Materials  

Microsoft Academic Search

\\u000a This chapter provides an overall picture of nanocrystal-polymer based composites and describes the key properties of these\\u000a original functional materials, particularly suited for advanced applications in photonic, optoelectronic as well as in sensing.\\u000a Here, we aim at pointing out the relevance of the incorporation of inorganic colloidal nanocrystals with size-dependent properties\\u000a in highly processable polymers. Due to the countless different

M. Striccoli; M. L. Curri; R. Comparelli

396

Development of active composites using conventional structural materials  

Microsoft Academic Search

Development of new active composites using conventional structural materials are described in this paper. An active CFRP\\/Al laminate was proposed and developed, which became flat when it was kept at its hot pressing temperature 393K by electric resistance heating of the carbon fiber in the CFRP layer, and its curvature increased when it was air-cooled. The mechanism of its actuation

Hiroshi Asanuma; Osamu Haga; Genji Hakoda; Junichiro Ohira

2001-01-01

397

Application of fictitious domain method to analysis of composite materials  

Microsoft Academic Search

A method that allows one to solve general three-dimensional nonlinear problems arising in the micromechanics of composite materials is introduced. The principal idea of the method is to replace a boundary-value problem defined on a complicated domain by a set of boundary-value problems defined on simple domains. This replacement allows one to avoid complicated mesh generation and to exploit fast

Eugene Grigorievich Podnos

1999-01-01

398

Manganese oxide–carbon composite as supercapacitor electrode materials  

Microsoft Academic Search

Nano-sized manganese oxide (Mn2O3) was incorporated homogeneously in templated mesoporous carbon to prepare Mn2O3–carbon nanocomposites, which were used as supercapacitor electrodes. Cyclic voltammetry was employed to investigate the electrochemical properties of the composite materials in an aqueous electrolyte under different scan rates. Results showed that templated mesoporous carbon with layered graphene domains holds a great promise for high-rate supercapacitor applications.

Li Li Zhang; Tianxin Wei; Wenjuan Wang; X. S. Zhao

2009-01-01

399

Degradation, Fatigue, and Failure of Resin Dental Composite Materials  

Microsoft Academic Search

The intent of this article is to review the numerous factors that affect the mechanical properties of particle-or fiber-filler-containing indirect dental resin composite materials. The focus will be on the effects of degradation due to aging in different media, mainly water and water and ethanol, cyclic loading, and mixed-mode loading on flexure strength and fracture toughness. Several selected papers will

J. L. Drummond

2008-01-01

400

Mechanical response of a mine composite material to extreme heat  

Microsoft Academic Search

The use of cemented paste backfills (CPB, a mine composite tailings material) in underground mining is currently increasing\\u000a in importance globally. However, despite the tremendous progress made in understanding the factors affecting the performance\\u000a of CPB, little attention has been devoted to the impact of high temperatures on its mechanical properties. This article presents\\u000a the results of experimental investigations into

L. Orejarena; M. Fall

2008-01-01

401

Non-destructive evaluation of composite materials using ultrasound  

NASA Technical Reports Server (NTRS)

Investigation of the nondestructive evaluation of advanced composite-laminates is summarized. Indices derived from the measurement of fundamental acoustic parameters are used in order to quantitatively estimate the local material properties of the laminate. The following sections describe ongoing studies of phase insensitive attenuation measurements, and discuss several phenomena which influences the previously reported technique of polar backscatter. A simple and effective programmable gate circuit designed for use in estimating attenuation from backscatter is described.

Miller, J. G.

1984-01-01

402

Quasidislocations in anisotropic bicrystals  

NASA Astrophysics Data System (ADS)

Weertman has recently pointed out that an elastic line singularity of dislocation/force line character but of zero Burgers vector and zero line force can move at the Stoneley velocity along the interface in a bicrystal of two different isotropic materials [J. Weertman, Phys. Rev. Lett. 93, 2655 (2004)]. The theory of this quasidislocation is generalized to the case of anisotropic bicrystals. The quasidislocation-Stoneley wave connection remains generally true and is further elucidated.

Lothe, Jens

2005-08-01

403

Facesheet Delamination of Composite Sandwich Materials at Cryogenic Temperatures  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

404

The Abundance and Isotopic Composition of Hg in Extraterrestrial Materials  

NASA Technical Reports Server (NTRS)

During the past three year grant period we made excellent progress in our study of the abundances and isotopic compositions of Hg and other volatile trace elements in extraterrestrial materials. As part of my startup package I received funds to construct a state-of-the-art experimental facility to study gas-solid reaction kinetics. Much of our effort was spent developing the methodology to measure the abundance and isotopic composition of Hg at ultratrace levels in solid materials. In our first study, the abundance and isotopic composition of Hg was determined in bulk samples of the Murchison (CM) and Allende (CV) carbonaceous chondrites. We have continued our study of mercury in primitive meteorites and expanded the suite of meteorites to include other members of the CM and CV chondrite group as well as CI and CO chondrites. Samples of the CI chondrite Orgueil, the CM chondrites Murray, Nogoya, and Cold Bokkeveld, the CO chondrites Kainsaz, Omans, and Isna, and the CV chondrites Vigarano, Mokoia, and Grosnaja were tested. We have developed a thermal analysis ICP-MS technique and applied it to the study of a suite of thermally labile elements (Zn, As, Se, Cd, In, Sn, Sb, Te, Hg, Au, Tl, Pb, and Bi) in geologic materials as well.

Lauretta, D. S.

2004-01-01

405

Characterization of Triaxial Braided Composite Material Properties for Impact Simulation  

NASA Technical Reports Server (NTRS)

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.

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

2009-01-01

406

Strain Gage Selection Criteria for Textile Composite Materials  

NASA Technical Reports Server (NTRS)

This report will provide a review of efforts to establish a set of strain gage selection guidelines for textile reinforced composite materials. A variety of strain gages were evaluated in the study to determine the sensitivity of strain measurements to the size of the strain gage. The strain gages were chosen to provide a range of gage lengths and widths. The gage aspect ratio (the length-to-width ratio) was also varied. The gages were tested on a diverse collection of textile composite laminates. Test specimens featured eleven different textile architectures: four 2-D triaxial braids, six 3-D weaves, and one stitched uniweave architecture. All specimens were loaded in uniaxial tension. The materials' moduli were measured in both the longitudinal (parallel to the O deg. yarns) and the transverse (perpendicular to the O deg. yarns) directions. The results of these measurements were analyzed to establish performance levels for extensometers and strain gages on textile composite materials. Conclusions are expressed in a summary that discusses instrumentation practices and defines strain gage selection criteria.

Masters, John E.

1996-01-01

407

Multi-physics computational grains (MPCGs) for direct numerical simulation (DNS) of piezoelectric composite/porous materials and structures  

NASA Astrophysics Data System (ADS)

Conceptually simple and computationally most efficient polygonal computational grains with voids/inclusions are proposed for the direct numerical simulation of the micromechanics of piezoelectric composite/porous materials with non-symmetrical arrangement of voids/inclusions. These are named "Multi-Physics Computational Grains" (MPCGs) because each "mathematical grain" is geometrically similar to the irregular shapes of the physical grains of the material in the micro-scale. So each MPCG element represents a grain of the matrix of the composite and can include a pore or an inclusion. MPCG is based on assuming independent displacements and electric-potentials in each cell. The trial solutions in each MPCG do not need to satisfy the governing differential equations, however, they are still complete, and can efficiently model concentration of electric and mechanical fields. MPCG can be used to model any generally anisotropic material as well as nonlinear problems. The essential idea can also be easily applied to accurately solve other multi-physical problems, such as complex thermal-electro-magnetic-mechanical materials modeling. Several examples are presented to show the capabilities of the proposed MPCGs and their accuracy.

Bishay, Peter L.; Dong, Leiting; Atluri, Satya N.

2014-11-01

408

Determination of Residual Stress in Composite Materials Using Ultrasonic Waves  

NASA Technical Reports Server (NTRS)

The performance of high temperature composites can be significantly affected by the presence of residual stresses. These stresses arise during cooling processes from fabrication to room temperature due to mismatch of thermal expansion coefficients between matrix and fiber materials. This effect is especially pronounced in metal matrix and intermetallic composites. It can lead to plastic deformations, matrix cracking and fiber/matrix interface debonding. In this work the feasibility of ultrasonic techniques for residual stress assessment in composites is addressed. A novel technique for absolute stress determination in orthotropic materials from angular dependencies of ultrasonic velocities is described. The technique is applicable for determination of both applied and residual stresses and does not require calibration measurements on a reference sample. The important advantage of this method is that stress is determined simultaneously with stress-dependent elastic constants and is thus decoupled from the material texture. It is demonstrated that when the principal plane stress directions coincide with acoustical axes, the angular velocity data in the plane perpendicular to the stress plane may be used to determine both stress components. When the stress is off the acoustical axes, the shear and the difference of the normal stress components may be determined from the angular dependence of group velocities in the plane of stresses. Synthetic sets of experimental data corresponding to materials with different anisotropy and stress levels are used to check the applicability of the technique. The method is also verified experimentally. A high precision ultrasonic wave transmission technique is developed to measure angular dependence of ultrasonic velocities. Examples of stress determination from experimental velocity data are given. A method is presented for determination of velocities of ultrasonic waves propagating through the composite material with residual stresses. It is based on the generalized self-consistent multiple scattering model. Calculation results for longitudinal and shear ultrasonic wave velocities propagating perpendicular to the fibers direction in SCS-6/Ti composite with and without residual stresses are presented. They show that velocity changes due to presence of stresses are of order 1%.

Rokhlin, S. I.

1997-01-01

409

Theoretical prediction of dynamic composite material properties for hypervelocity impact simulations  

Microsoft Academic Search

Recent advances in the description of fibre-reinforced polymer composite material behaviour under extreme loading rates provide a significant extension in capabilities for numerical simulation of hypervelocity impact on composite satellite structures. Given the complexity of the material model, extensive material characterisation is required, however, as the properties of composite materials are commonly tailored for a specific application, experimental characterisation is

S. Ryan; M. Wicklein; A. Mouritz; W. Riedel; F. Schäfer; K. Thoma

2009-01-01

410

TRANSTRAIN: A program to compute strain transformations in composite materials  

SciTech Connect

Over the years, the solid rocket motor community has made increasing use of composite materials for thermal and structural applications. This is particularly true of solid rocket nozzles, which have used carbon phenolic and, increasingly, carbon-carbon materials to provide structural integrity and thermal protection at the high temperatures encountered during motor burn. To evaluate the degree of structural performance of nozzles and their materials and to verify analysis models, many subscale and full-scale tests are run. These provide engineers with valuable data needed to optimize design and to analyze nozzle hardware. Included among these data are strains, pressures, thrust, temperatures, and displacements. Recent nozzle test hardware has made increasing use of strain gauges embedded in the carbon composite material to measure internal strains. In order to evaluate strength, these data must be transformed into strains along the fiber directions. The fiber-direction stresses can then be calculated. A computer program written to help engineers correctly manipulate the strain data into a form that can be used to evaluate structural integrity of the nozzle is examined.

Ahmed, R.

1990-07-01

411

Development of active composites using conventional structural materials  

NASA Astrophysics Data System (ADS)

Development of new active composites using conventional structural materials are described in this paper. An active CFRP/Al laminate was proposed and developed, which became flat when it was kept at its hot pressing temperature 393K by electric resistance heating of the carbon fiber in the CFRP layer, and its curvature increased when it was air-cooled. The mechanism of its actuation is fundamentally the same as that of bimetal, but its major advantage is its directional actuation due to directionality of the reinforcement fiber and its anisotropy of CTE. FRM based active material was also developed. SiC fiber reinforced aluminum composite was laminated with unreinforced aluminum plate by the interphase forming/bonding method using copper insert foil. Curvature of the material monotonically changed as a function of temperature. It was also clarified that the copper concentrated around the SiC fiber which was introduced by the interphase forming/bonding method contributed to curvature increase of the actuator. In order to detect its deformation, pre-notched optical fiber was embedded in the active material and successfully broken in it to form an optical loss type sensor. Using this sensor, a simple relation between curvature change and change of optical loss to be used for its shape control was successfully obtained.

Asanuma, Hiroshi; Haga, Osamu; Hakoda, Genji; Ohira, Junichiro

2001-04-01

412

Fatigue Crack Measurement in Composite Materials by Ultrasonic Methods  

NASA Technical Reports Server (NTRS)

The nondestructive detection of intra-ply microcracking in unlined pressure vessels fabricated from composite materials is critical to ensuring mission success. Microcracking in composite structures due to combined fatigue and cryogenic thermal loading can be very troublesome to detect in-service and when it begins to link through the thickness can cause leakage and failure of the structure. These leaks may lead to loss of pressure/propellant, increased risk of explosion and possible cryo-pumping. The work presented herein develops a method and an instrument to locate and measure 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 an object. 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 spike pulsed ultrasonics. This relative energy increase improves the ability to measure finer details in the materials character, such as micro-cracking and porosity. As the micro-crack density increases, more interactions occur with the higher frequency (small wavelength) components of the signal train causing the spectrum to shift toward lower frequencies. Preliminary experiments have verified a measurable effect on the resonance spectrum of the ultrasonic data to detect microcracking. Methods involving self organizing neural networks and other clustering algorithms show that the resonance ultrasound signatures from composites vary with the degree of microcracking and can be separated and identified.

Walker, James L.; Russell, Samuel S.; Suits, Michael W.; Workman, Gary L.; Watson, Jason M.; Thom, Robert (Technical Monitor)

2002-01-01

413

Influence of Material Distribution on Impact Resistance of Hybrid Composites  

NASA Technical Reports Server (NTRS)

Impact events occur in a wide variety of circumstances. A typical example is a bullet impacting a target made of composite material. These impact events produce time-varying loads on a structure that can result in damage. As a first step to understanding the damage resistance issue in composite laminates, an accurate prediction of the transient response during an impact event is necessary. The analysis of dynamic loadings on laminated composite plates has undergone considerable development recently. Rayleigh-Ritz energy method was used to determine the impact response of laminated plates. The impact response of composite plates using shear deformation plate theory was analyzed. In recent work a closed-form solution was obtained for a rectangular plate with four edges simply supported subjected to a center impact load using classical plate theory. The problem was further investigated and the analysis results compared of both classical plate theory and shear deformation theory, and found that classical plate theory predicts very accurate results for the range of small deformations considered. In this study, the influence of cross sectional material distribution on the comparative impact responses of hybrid metal laminates subjected to low and medium velocity impacts is investigated. A simple linear model to evaluate the magnitude of the impact load is proposed first, and it establishes a relation between the impact velocity and the impact force. Then a closed-form solution for impact problem is presented. The results were compared with the finite element analysis results. For an 11 layer-hybrid laminate, the impact response as a function of material distribution in cross-section is presented. With equal areal weight, the effect of the number of laminate layers on the impact resistance is also investigated. Finally, the significance of the presented results is discussed.

Abatan, Ayu; Hu, Hurang

1998-01-01

414

Semi-annual report on materials research in support of superconducting machinery. Final report. [Composite materials  

Microsoft Academic Search

The following five areas are discussed: advanced composites, elastic properties, fatigue resistance and fracture toughness, magnetothermal conductivity, and thermal conductivity. Material properties were studied over the temperature range 4 to 300°K. Materials studied include: aluminum alloy 5083, copper--0.3 cadmium--0.3 tin, copper--28 nickel, iron--48 nickel, 3.5 Ni and 9 Ni steels, titanium--4 aluminum--6 vanadium, titanium--5 aluminum--2.5 tin, stainless steel 21-6-9, several

R. P. Reed; J. G. Hust; M. B. Kasen; H. M. Ledbetter; H. I. McHenry

1976-01-01

415

Measuring the insulating ability of anisotropic thermal conductors via principal Dirichlet eigenvalue  

Microsoft Academic Search

We consider the thermal insulation property of homogeneous anisotropically heat-conducting bodies, i.e. those whose thermal tensor (matrix) A is constant throughout the body but not generally a constant times the identity. This anisotropy is a common feature of nano- composite materials. We propose using the principal Dirichlet eigenvalue ? of the associated elliptic differential operator ?? · A? as a

STEVE R OSENCRANS; XUEFENG WANG; WILLIAM W INTER

2009-01-01

416

Voigt waves in electro-optic homogenized composite materials  

NASA Astrophysics Data System (ADS)

A study was undertaken into Voigt wave propagation in a homogenized composite material (HCM). The HCM investigated arose from a porous electro-optic host material infiltrated by a fluid of refractive index na, considered in the long-wavelength regime. The extended Bruggeman homogenization formalism was employed to estimate the constitutive parameters of the HCM. In principle, the directions which support Voigt wave propagation in the HCM may be controlled by means of an applied dc electric field; and the degree of control may be sensitive to the porosity of the host material, the shapes, sizes and orientations of the pores, as well as the refractive index na. Here the theoretical methodology is presented; numerical results are presented elsewhere.

Mackay, Tom G.

2014-08-01

417

Composition and mineralogy of dark material units on Vesta  

NASA Astrophysics Data System (ADS)

Vesta is the asteroid with the largest albedo variation among the known rocky Solar System objects and shows a widespread occurrence of dark material (DM) and bright material (BM) units. In the first observation phases by the Dawn spacecraft, two main extensions of low albedo areas were identified on Vesta and found to be closely correlated with carbonaceous, OH-rich, material. In this work we use the hyperspectral data provided by the VIR-Dawn imaging spectrometer onboard Dawn to detect and analyze individual, well-defined, dark material units. We define DM units assuming a relative criterion, i.e. reflectance lower than the surroundings. By coupling visible and infrared images of the same area we are able to select real dark material units, discarding false detections created by shadowing effects. A detailed final catalogue of 123 dark units is presented, containing the geographical parameters and the main spectral characteristics for each unit. Independently of the geological context of the dark units, all DMs show similar spectral properties, dominated by the pyroxene absorption features, as is the average spectrum of Vesta. This finding suggests a similar composition, with the presence of darkening agents that also weaken pyroxene band depths. The majority (90%) of the DM units shows a positive correlation between low albedo and an OH band centered at 2.8 ?m, confirming the hypothesis that the darkening agents are carbonaceous chondrites, probably delivered by low-velocity impacts of primitive asteroids. A comparison with laboratory spectra allows us to better constrain the size and the composition of the darkening agents. These DM areas seem to be made of eucritic material. The regolith grain size seems to be nearly constant around an average value of 25 ?m, and is quite homogenous at least in the first hundreds of meters beneath the Vesta surface, suggesting similar processing mechanisms for both DM and BM.

Palomba, Ernesto; Longobardo, Andrea; De Sanctis, Maria Cristina; Zambon, Francesca; Tosi, Federico; Ammannito, Eleonora; Capaccioni, Fabrizio; Frigeri, Alessandro; Capria, Maria Teresa; Cloutis, Edward A.; Jaumann, Ralf; Combe, Jean-Philippe; Raymond, Carol A.; Russell, Christopher T.

2014-09-01

418

Woven fabric composite material model with material nonlinearity for nonlinear finite element simulation  

Microsoft Academic Search

The objective of the current investigation is to develop a simple, yet generalized, model which considers the two-dimensional extent of woven fabric, and to have an interface with nonlinear finite element codes. A micromechanical composite material model for woven fabric with nonlinear stress-strain relations is developed and implemented in ABAQUS for nonlinear finite element structural analysis. Within the model a

A. Tabiei; Y. Jiang

1999-01-01

419

Composition of Surface Materials on the Moons of Mars  

NASA Astrophysics Data System (ADS)

The two small asteroid-like bodies orbiting Mars, Phobos and Deimos, are low albedo and exhibit similar visible to near-infrared spectra. Determining the origin of these moons is closely tied to determining their composition. From available spectroscopic data Phobos exhibits two distinct types of materials across its surface, and data from both Mars Express and Mars Reconnaissance Orbiter have provided additional details about the properties of these materials and their spatial relation to one another. Although no prominent diagnostic absorptions have been detected, systematic weak features are seen in some data. An extensive regolith is observed to have developed on both moons with characteristics that may be unique due to their special environment in Mars orbit. Understanding the character and evolution of the regolith of Phobos and Deimos is central to interpreting the moons' physical and optical properties. The cumulative data available for compositional analyses across the surface of Phobos and Deimos, however, remain incomplete in scope and character and ambiguous in interpretation. Consequently the composition of the moons of Mars remains uncertain.

Pieters, Carle M.; Murchie, Scott; Thomas, Nicolas; Britt, Daniel

2014-11-01

420

A boundary element analysis of metal matrix composite materials  

SciTech Connect

Various Metal Matrix Composite systems are modeled using Boundary Element Methods. The predicted material properties are compared with properties obtained using Finite Element Methods, and good agreement is found. When elastic properties are sought, BEM has a distinct advantage over FEM in terms of efficiency. When plastic properties are simulated the advantage is of a lesser magnitude. BEM also allows easy modeling of the behavior of the composite at the interface between the strengthening particle and the matrix. Such a model is implemented here. Finally, the predicted elastic properties of MMC systems of various reinforcement content are compared with experimentally determined properties of corresponding specimens. Good agreement is found for reinforcement volume fractions up to 20%.

Mammoli, A.A.; Bush, M. [Univ. of Western Australia, Nedlands (Australia). Dept. of Mechanical and Materials Engineering

1993-12-31

421

Recycling By Solvolysis Thermosetting Composite Materials Of Sustainable Surface Transport  

SciTech Connect

A solvolysis process is studied to degrade an unsaturated polyester resin based on DCPD (dicyclopentadiene) and crosslinked with styrene, as the matrix of a composite material reinforced with long glass fibers. The study presented here investigates in particular the hydrolysis in conditions below the critical point of water (T<374 deg. C and P<221bar) in a batch reactor. Process window and parameter influences were studied by a Design of Experiments (DOE) approach (1). A tar-like substance issued from thermal degradations is formed in greater or lesser quantities depending on the operating conditions, and coats the fibers. The appearance of the composite samples and the degree of conversion for the degradation at 250 deg. C lead us to make a parallel with osmosis phenomena to explain the initiation mechanism of the degradation.

Oliveux, Geraldine; Le Gal La Salle, Eric [Laboratoire de Thermocinetique de Nantes (LTN), UMR CNRS 6607, Ecole Polytechnique de l'Universite de Nantes, Rue Christian Pauc, 44303 Nantes (France); Bailleul, Jean-Luc [Laboratoire Energetique, Mecanique et Materiaux(LE2M) de l'Institut Catholique des Arts et Metiers de Nantes, 35 avenue du champ de Manoeuvres, 44470 Carquefou (France)

2011-01-17

422

Lightweight Impact-Resistant Composite Materials: Lessons from Mantis Shrimp  

NASA Astrophysics Data System (ADS)

Nature has evolved efficient strategies to synthesize complex mineralized structures that exhibit exceptional damage tolerance. One such example is found in the hyper-mineralized hammer-like dactyl clubs of the stomatopods, a group of highly aggressive marine crustaceans. The dactyl clubs from one such species, Odontodactylus Scyllarus, exhibit an impressive set of characteristics adapted for surviving high velocity impacts with the heavily mineralized prey species on which they feed. Consisting of a multi-phase composite of oriented crystalline hydroxyapatite and amorphous calcium phosphate and carbonate, in conjunction with a highly expanded helicoidal organization of the fibrillar chitinous organic matrix, these structures display several effective lines of defense against catastrophic failure during repetitive high energy loading events. The study of this organism and its relatives has lead to design cues, which were incorporated into prototype composite materials designed for applications in aviation, body armor, and entertainment.

Milliron, Garrett Wayne

423

Early detection of fatigue damage in composite materials  

NASA Technical Reports Server (NTRS)

Early detection of fatigue damage in composite materials by nondestructive inspection (NDI) techniques has been demonstrated for glass/epoxy, graphite/glass/epoxy, and graphite/epoxy composites. Modulus and temperature were monitored and a correlation between them observed. Axial modulus and torsional modulus changes were a function of the laminate orientation. Torsional modulus measurements and coin tap tests were performed at 0, 1 million, 5 million, and 10 million cycles, on axial fatigue specimens. Three distinct regions were noted. In the primary region a small but rapid change in stiffness was noted in the first few thousand cycles. This was followed by a secondary region of little or no stiffness change. The tertiary region was characterized by an increasing rate of stiffness change leading to fracture. NDI procedures including holographic interferometry, ultrasonics, penetrant, and X-ray radiography were evaluated for fatigue damage detection.

Salkind, M. J.

1975-01-01

424

Damage and strength of composite materials: Trends, predictions, and challenges  

NASA Technical Reports Server (NTRS)

Research on damage mechanisms and ultimate strength of composite materials relevant to scaling issues will be addressed in this viewgraph presentation. The use of fracture mechanics and Weibull statistics to predict scaling effects for the onset of isolated damage mechanisms will be highlighted. The ability of simple fracture mechanics models to predict trends that are useful in parametric or preliminary designs studies will be reviewed. The limitations of these simple models for complex loading conditions will also be noted. The difficulty in developing generic criteria for the growth of these mechanisms needed in progressive damage models to predict strength will be addressed. A specific example for a problem where failure is a direct consequence of progressive delamination will be explored. A damage threshold/fail-safety concept for addressing composite damage tolerance will be discussed.

Obrien, T. Kevin

1994-01-01

425

Compressive strength of fiber-reinforced composite materials  

NASA Technical Reports Server (NTRS)

Results of an experimental and analytical investigation of the compressive strength of unidirectional boron-epoxy composite material are presented. Observation of fiber coordinates in a boron-epoxy composite indicates that the fibers contain initial curvature. Combined axial compression and torsion tests were conducted on boron-epoxy tubes and it was shown that the shear modulus is a function of axial compressive stress. An analytical model which includes initial curvature in the fibers and permits an estimate of the effect of curvature on compressive strength is proposed. Two modes of failure which may result from the application of axial compressive stress are analyzed - delamination and shear instability. Based on tests and analysis, failure of boron-epoxy under axial compressive load is due to shear instability.

Davis, J. G., Jr.

1975-01-01

426

Tuneable broadband optical filter based on soft-composite materials  

NASA Astrophysics Data System (ADS)

We report on the realization and characterization of a ‘free space’ diffractive optical filter based on a periodic structure realized in soft composite materials. By combining a high stability optical holographic setup with a light sensitive composite mixture, we have realized a structure made of polymeric slices alternated to pure, well aligned, nematic liquid crystals. Its polarization dependent diffractive properties have been exploited for realizing a diffractive, band-gap based, broadband optical filter. The sample is characterized in terms of its morphological, optical and electro-optical properties. We show that both electric fields and temperature variations can be exploited to tune the position of the diffractive band-gap of about 83 nm and 116 nm respectively.

De Sio, Luciano; Caligiuri, Vincenzo; Umeton, Cesare

2014-06-01

427

Recycling By Solvolysis Thermosetting Composite Materials Of Sustainable Surface Transport  

NASA Astrophysics Data System (ADS)

A solvolysis process is studied to degrade an unsaturated polyester resin based on DCPD (dicyclopentadiene) and crosslinked with styrene, as the matrix of a composite material reinforced with long glass fibers. The study presented here investigates in particular the hydrolysis in conditions below the critical point of water (T<374° C and P<221bar) in a batch reactor. Process window and parameter influences were studied by a Design of Experiments (DOE) approach (1). A tar-like substance issued from thermal degradations is formed in greater or lesser quantities depending on the operating conditions, and coats the fibers. The appearance of the composite samples and the degree of conversion for the degradation at 250° C lead us to make a parallel with osmosis phenomena to explain the initiation mechanism of the degradation.

Oliveux, Géraldine; Le Gal La Salle, Eric; Bailleul, Jean-Luc

2011-01-01

428

Physics in ``Polymers, Composites, and Sports Materials" an Interdisciplinary Course  

NASA Astrophysics Data System (ADS)

The undergraduate science course described uses the themes of polymers and composites, as used in sports materials, to teach some key concepts in introductory chemistry and physics. The course is geared towards students who are interested in science, but are still completing prerequisite mathematics courses required for science majors. Each class is built around a laboratory activity. Atoms, molecules and chemical reactions are taught in reference to making polyvinyl acetate (white glue) and polyvinyl alcohol (gel glue). These materials, combined with borax, form balls which are subsequently used in physics activities centered on free-fall and the coefficient of restitution. These activities allow the introduction of kinematics and dynamics. A free fall activity involving ice pellets, with and without embedded tissue paper, illustrates the properties of composites. The final series of activities uses balls, shoes, racquets and bats to further illustrate dynamics concepts (including friction, momentum and energy). The physical properties of these sports objects are discussed in terms of the materials of which they are made. The evaluation plan to determine the effectiveness of these activities and preliminary results are also presented.

Hagedorn, Eric; Suskavcevic, Milijana

2007-10-01

429

Finite element analysis of composites materials for aerospace applications  

NASA Astrophysics Data System (ADS)

Composites materials are intended to be used more extensively as an alternative of aluminum structure in aircraft and aerospace applications. This is due to their attractive properties as high strength-to-weight ratio and stiffness-to-weight ratio. Besides that it clarifies the growing interest for composites materials due to advantages of lightweight, high strength, high stiffness, superior fatigue life, tremendous corrosion resistance and low cost manufacturing. In this study, a finite element analysis (FEA) of fiberglass unidirectional E-type was analyzed in the framework of ABAQUS finite element commercial software. The analysis was done to quantify the mechanical properties and response of unidirectional E-glass in term of tensile, compression and thermal responses. From the analysis, the maximum and minimum values of stress and strain for E-glass 21xK43 Gevetex and Silenka E-glass 1200tex were obtained and stress-strain curve is presented. The ultimate load of failure, elastic behavior, tensile strength and other properties for each laminated plates under tensile and thermal-stress are determined from stress-strain curves. The simulation will run twice for each material where the first simulation based on orientation angles of 45° for ply-1, -45° for ply-2 and 90° for ply-3 while the second simulation, the orientation angles is 0° for all plies. The simulation is successfully conducted and verified by experimental data.

Nurhaniza, M.; Ariffin, M. K. A.; Ali, Aidy; Mustapha, F.; Noraini, A. W.

2010-05-01

430

Interlaminar shear fracture toughness and fatigue thresholds for composite materials  

NASA Technical Reports Server (NTRS)

Static and cyclic end notched flexure tests were conducted on a graphite epoxy, a glass epoxy, and graphite thermoplastic to determine their interlaminar shear fracture toughness and fatigue thresholds for delamination in terms of limiting values of the mode II strain energy release rate, G-II, for delamination growth. The influence of precracking and data reduction schemes are discussed. Finite element analysis indicated that the beam theory calculation for G-II with the transverse shear contribution included was reasonably accurate over the entire range of crack lengths. Cyclic loading significantly reduced the critical G-II for delamination. A threshold value of the maximum cyclic G-II below which no delamination occurred after one million cycles was identified for each material. Also, residual static toughness tests were conducted on glass epoxy specimens that had undergone one million cycles without delamination. A linear mixed-mode delamination criteria was used to characterize the static toughness of several composite materials; however, a total G threshold criterion appears to characterize the fatigue delamination durability of composite materials with a wide range of static toughness.

O'Brien, T. Kevin; Murri, Gretchen B.; Salpekar, Satish A.

1989-01-01

431

Interlaminar shear fracture toughness and fatigue thresholds for composite materials  

NASA Technical Reports Server (NTRS)

Static and cyclic end notched flexure tests were conducted on a graphite epoxy, a glass epoxy, and graphite thermoplastic to determine their interlaminar shear fracture toughness and fatigue thresholds for delamination in terms of limiting values of the mode II strain energy release rate, G-II, for delamination growth. The influence of precracking and data reduction schemes are discussed. Finite element analysis indicated that the beam theory calculation for G-II with the transverse shear contribution included was reasonably accurate over the entire range of crack lengths. Cyclic loading significantly reduced the critical G-II for delamination. A threshold value of the maximum cyclic G-II below which no delamination occurred after one million cycles was identified for each material. Also, residual static toughness tests were conducted on glass epoxy specimens that had undergone one million cycles without delamination. A linear mixed-mode delamination criteria was used to characterize the static toughness of several composite materials; however, a total G threshold criterion appears to characterize the fatigue delamination durability of composite materials with a wide range of static toughness.

Obrien, T. Kevin; Murri, Gretchen B.; Salpekar, Satish A.