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1

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

2

Improved understanding of the dynamic response in anisotropic directional composite materials through the combination of experiments and modeling  

NASA Astrophysics Data System (ADS)

Recently there has been renewed interest in the dynamic response of composite materials; specifically low density epoxy matrix binders strengthened with continuous reinforcing fibers. This is in part due to the widespread use of carbon fiber composites in military, commercial, industrial, and aerospace applications. The design community requires better understanding of these materials in order to make full use of their unique properties. Planar impact testing was performed resulting in pressures up to 15 GPa on a unidirectional carbon fiber - epoxy composite, engineered to have high uniformity and low porosity. Results illustrate the anisotropic nature of the response under shock loading. Along the fiber direction, a two-wave structure similar to typical elastic-plastic response is observed, however, when shocked transverse to the fibers, only a single bulk shock wave is detected. At higher pressures, the epoxy matrix dissociates resulting in a loss of anisotropy. Greater understanding of the mechanisms responsible for the observed response has been achieved through numerical modeling of the system at the micromechanical level using the CTH hydrocode. From the simulation results it is evident that the observed two-wave structure in the longitudinal fiber direction is the result of a fast moving elastic precursor wave traveling in the carbon fibers ahead of the bulk response in the epoxy resin. Similarly, in the transverse direction, results show a collapse of the resin component consistent with the experimental observation of a single shock wave traveling at speeds associated with bulk carbon. Experimental and simulation results will be discussed and used to show where additional mechanisms, not fully described by the currently used models, are present.

Alexander, C. S.; Key, C. T.; Schumacher, S. C.

2014-05-01

3

Microrheological Characterisation of Anisotropic Materials  

E-print Network

We describe the measurement of anisotropic viscoelastic moduli in complex soft materials, such as biopolymer gels, via video particle tracking microrheology of colloid tracer particles. The use of a correlation tensor to find the axes of maximum anisotropy, and hence the mechanical director, is described. The moduli of an aligned DNA gel are reported, as a test of the technique; this may have implications for high DNA concentrations in vivo. We also discuss the errors in microrheological measurement, and describe the use of frequency space filtering to improve displacement resolution, and hence probe these typically high modulus materials.

I A Hasnain; A M Donald

2006-03-03

4

Composite structural materials  

NASA Technical Reports Server (NTRS)

Progress is reported in studies of constituent materials composite materials, generic structural elements, processing science technology, and maintaining long-term structural integrity. Topics discussed include: mechanical properties of high performance carbon fibers; fatigue in composite materials; experimental and theoretical studies of moisture and temperature effects on the mechanical properties of graphite-epoxy laminates and neat resins; numerical investigations of the micromechanics of composite fracture; delamination failures of composite laminates; effect of notch size on composite laminates; improved beam theory for anisotropic materials; variation of resin properties through the thickness of cured samples; numerical analysis composite processing; heat treatment of metal matrix composites, and the RP-1 and RP2 gliders of the sailplane project.

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

1984-01-01

5

Dynamic elastic constants of anisotropic materials by resonant ultrasound spectroscopy  

Microsoft Academic Search

Resonant ultrasound spectroscopy (RUS) has been applied to the anisotropic elastic stiffness determination of SiC\\/Al composites and highly textured Zr-2.5 Nb alloys. To determine the elastic stiffness of anisotropic materials, the resonant frequencies of a rectangular parallelepiped specimen were measured and compared with the calculated frequencies based on the input data of the estimated stiffness, dimensions, and density. The initial

Yong-Moo Cheong; Hyun-Kyu Jung; Young-Sang Joo; Sung-Soo Kim; Young-Suk Kim

2000-01-01

6

Composite material  

DOEpatents

A composite biocompatible hydrogel material includes a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa. A calcium comprising salt is disposed in at least some of the pores. The porous polymer matrix can comprise cellulose, including bacterial cellulose. The composite can be used as a bone graft material. A method of tissue repair within the body of animals includes the steps of providing a composite biocompatible hydrogel material including a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa, and inserting the hydrogel material into cartilage or bone tissue of an animal, wherein the hydrogel material supports cell colonization in vitro for autologous cell seeding.

Hutchens, Stacy A. (Knoxville, TN); Woodward, Jonathan (Solihull, GB); Evans, Barbara R. (Oak Ridge, TN); O'Neill, Hugh M. (Knoxville, TN)

2012-02-07

7

Composite Materials  

NSDL National Science Digital Library

This is an activity (located on page 3 of PDF) about composites, materials made of 2 or more different components. Learners will be challenged to build the best mud bricks, one of the earliest examples of composites. From a supply of various building components, which the learners will examine for their different properties, they will build mud bricks, then dry them and put them through several tests. *Bricks must bake in the sun for 2-3 days prior to testing. Resource contains information about how this activity relates to carbon nanotubes and links to video, DragonflyTV Nano: Hockey Sticks.

2012-05-09

8

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

9

Computational Damage Mechanics for Composite Materials Based on Mathematical Homogenization  

E-print Network

1 Computational Damage Mechanics for Composite Materials Based on Mathematical Homogenization Jacob process in composite materi- als, among which the damage mechanics approach is particularly attractive is performed first followed by application of damage mechanics principles to homogenized anisotropic medium

Fish, Jacob

10

Dynamic elastic constants of anisotropic materials by resonant ultrasound spectroscopy.  

PubMed

Resonant ultrasound spectroscopy (RUS) has been applied to the anisotropic elastic stiffness determination of SiC/Al composites and highly textured Zr-2.5 Nb alloys. To determine the elastic stiffness of anisotropic materials, the resonant frequencies of a rectangular parallelepiped specimen were measured and compared with the calculated frequencies based on the input data of the estimated stiffness, dimensions, and density. The initial estimates of the elastic stiffness of SiC/Al composites were calculated using the Mori-Tananka (MT) theory and the concept of effective aspect ratio of reinforcements. For highly textured Zr-2.5 Nb alloy, the initial estimates were obtained from its orientation distribution function, determined by X-ray diffraction, and the reported elastic stiffness of a single crystal zirconium. Through a comparison of calculated frequencies with those measured by RUS, elastic stiffness values have been determined very accurately by iteration and convergence processes. PMID:18238582

Cheong, Y M; Jung, H K; Joo, Y S; Kim, S S; Kim, Y S

2000-01-01

11

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Effective Anisotropic Dielectric Properties of Crystal Composites  

NASA Astrophysics Data System (ADS)

Transformation field method (TFM) is developed to estimate the anisotropic dielectric properties of crystal composites having arbitrary shapes and dielectric properties of crystal inclusions, whose principal dielectric axis are different from those of anisotropic crystal matrix. The complicated boundary-value problem caused by inclusion shapes is circumvented by introducing a transformation electric field into the crystal composites regions, and the effective anisotropic dielectric responses are formulated in terms of the transformation field. Furthermore, the numerical results show that the effective anisotropic dielectric responses of crystal composites periodically vary as a function of the rotating angle between the principal dielectric axes of inclusion and matrix crystal materials. It is found that at larger inclusion volume fraction the inclusion shapes induce profound effect on the effective anisotropic dielectric responses.

Wei, En-Bo; Gu, Guo-Qing; Poon, Ying-Ming; Franklin, G. Shin

2010-02-01

12

On the mechanical response of anisotropic granular materials  

Microsoft Academic Search

The subject of this thesis is the mechanical response of inherently anisotropic granular materials. The study comprises both the experimental and numerical aspects and provides a rigorous methodology for the solution of geotechnical problems involving anisotropic frictional materials. ^ The experimental investigation has been carried out at both the material and structural levels. The material tests involved a series of

Alireza Azami

2010-01-01

13

Compliance calibration for fracture testing of anisotropic biological materials  

Microsoft Academic Search

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.

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

2009-01-01

14

Designing chromonic mesogens for the fabrication of anisotropic optical materials  

NASA Astrophysics Data System (ADS)

Perylene monoimides and diimides have applications as luminescent materials and in organic photovoltaic devices as chromophores and conducting materials. Materials in which these compounds are oriented in a preferred direction will possess useful anisotropic properties that are not attainable from materials in which the compounds are randomly oriented. Anisotropic materials of these compounds can be prepared by taking advantage of the unique properties of chromonic liquid crystals. In this paper we describe the principles for designing perylene monoimides and diimides with desired optical properties and chromonic liquid-crystalline properties. In addition, we demonstrate the fabrication of anisotropic optical materials via organization of these compounds into a lyotropic chromonic liquidcrystalline phase.

Tam-Chang, Suk-Wah; Huang, Liming; Gyan, Aryal; Seo, Wonewoo; Mahinay, Delfin; Iverson, Isaac K.

2008-02-01

15

Anisotropic Cloth Modeling for Material Fabric  

NASA Astrophysics Data System (ADS)

Physically based cloth simulation has been challenging the graphics community for more than three decades. With the developing of virtual reality and clothing CAD, it has become the key technique of virtual garment and try-on system. Although it has received considerable attention in computer graphics, due to its flexible property and realistic feeling that the textile engineers pay much attention to, there is not a successful methodology to simulate cloth both in visual realism and physical accuracy. We present a new anisotropic textile modeling method based on physical mass-spring system, which models the warps and wefts separately according to the different material fabrics. The simulation process includes two main steps: firstly the rigid object simulation and secondly the flexible mass simulation near to be equilibrium. A multiresolution modeling is applied to enhance the tradeoff fruit of the realistic presentation and computation cost. Finally, some examples and the analysis results show the efficiency of the proposed method.

Zhang, Mingmin; Pan, Zhigengx; Mi, Qingfeng

16

Thermographic Imaging of Defects in Anisotropic Composites  

NASA Technical Reports Server (NTRS)

Composite materials are of increasing interest to the aerospace industry as a result of their weight versus performance characteristics. One of the disadvantages of composites is the high cost of fabrication and post inspection with conventional ultrasonic scanning systems. The high cost of inspection is driven by the need for scanning systems which can follow large curve surfaces. Additionally, either large water tanks or water squirters are required to couple the ultrasonics into the part. Thermographic techniques offer significant advantages over conventional ultrasonics by not requiring physical coupling between the part and sensor. The thermographic system can easily inspect large curved surface without requiring a surface following scanner. However, implementation of Thermal Nondestructive Evaluations (TNDE) for flaw detection in composite materials and structures requires determining its limit. Advanced algorithms have been developed to enable locating and sizing defects in carbon fiber reinforced plastic (CFRP). Thermal Tomography is a very promising method for visualizing the size and location of defects in materials such as CFRP. However, further investigations are required to determine its capabilities for inspection of thick composites. In present work we have studied influence of the anisotropy on the reconstructed image of a defect generated by an inversion technique. The composite material is considered as homogeneous with macro properties: thermal conductivity K, specific heat c, and density rho. The simulation process involves two sequential steps: solving the three dimensional transient heat diffusion equation for a sample with a defect, then estimating the defect location and size from the surface spatial and temporal thermal distributions (inverse problem), calculated from the simulations.

Plotnikov, Y. A.; Winfree, W. P.

2000-01-01

17

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

2006-10-16

18

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

19

Composite structural materials  

NASA Technical Reports Server (NTRS)

Transverse properties of fiber constituents in composites, fatigue in composite materials, matrix dominated properties of high performance composites, numerical investigation of moisture effects, numerical investigation of the micromechanics of composite fracture, advanced analysis methods, compact lug design, and the RP-1 and RP-2 sailplanes projects are discussed.

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

1983-01-01

20

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

21

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

22

Nano-composite materials  

DOEpatents

Nano-composite materials are disclosed. An exemplary method of producing a nano-composite material may comprise co-sputtering a transition metal and a refractory metal in a reactive atmosphere. The method may also comprise co-depositing a transition metal and a refractory metal composite structure on a substrate. The method may further comprise thermally annealing the deposited transition metal and refractory metal composite structure in a reactive atmosphere.

Lee, Se-Hee; Tracy, C. Edwin; Pitts, J. Roland

2010-05-25

23

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

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

Toward anisotropic materials via forced assembly coextrusion.  

PubMed

Multilayer coextrusion offers a diverse platform to examine layer dependent confinement effects on self-assembling nanomaterials via conventional extrusion technology. A triblock copolymer (BCP) with a cylindrical microstructure was processed via "forced assembly" to elucidate the effect of microdomain orientation on the mechanical behavior of multilayer films. The mechanical response was investigated in both the extrusion (ED) and transverse directions (TD) of the multilayer systems, revealing an influence of both cylinder-orientation and the interface on the mechanical response with decreasing layer thickness. The stress-strain curves for samples with the stress field along the cylinder axis revealed a sharp yielding phenomenon, while curves for specimens with the stress field applied perpendicular to the axis exhibited weak yielding behavior. The extensibility of the multilayer films stressed in the ED increases with decreasing layer thickness, but remains constant when deformed along the TD. Coextrusion technology allows for tunable mechanical toughness in industrial grade polymers via a continuous process. By altering the layer thickness of the two polymeric materials, we can tune the mechanics from strong, brittle behavior to a tough, ductile response by manipulation of the hierarchical structure. The enabling technology provides a unique platform to couple the inherent mechanical response of dissimilar polymers and allows for the design of composite materials with tailored mechanics. PMID:22991945

Burt, Tiffani M; Jordan, Alex M; Korley, LaShanda T J

2012-10-24

26

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

27

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

28

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

29

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

30

A Multisurface Anisotropic Model for Quasi-brittle Materials  

Microsoft Academic Search

A novel yield criterion capable of modelling the softening behaviour of anisotropic materials under plane stress conditions is presented. Individual yield criteria are considered for tension and compression, according to two different failure mechanisms. The former is associated with a localised fracture process, denoted by cracking of the material, and, the latter, is associated with a more distributed fracture process

Paulo B. Lourenço; Jan G. Rots

1996-01-01

31

Composite structural materials  

NASA Technical Reports Server (NTRS)

The promise of filamentary composite materials, whose development may be considered as entering its second generation, continues to generate intense interest and applications activity. Fiber reinforced composite materials offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been achieved since the initial developments in the mid 1960's. Rather limited applications to primary aircraft structure have been made, however, mainly in a material-substitution mode on military aircraft, except for a few experiments currently underway on large passenger airplanes in commercial operation. To fulfill the promise of composite materials completely requires a strong technology base. NASA and AFOSR recognize the present state of the art to be such that to fully exploit composites in sophisticated aerospace structures, the technology base must be improved. This, in turn, calls for expanding fundamental knowledge and the means by which it can be successfully applied in design and manufacture.

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

1982-01-01

32

Composite structural materials  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

33

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

34

Edge singularities in 3-D elastic anisotropic and multi-material domains  

Microsoft Academic Search

The solution to elasticity problems in three-dimensional (3-D) polyhedral multi-material anisotropic domains in the vicinity of an edge is addressed. It includes eigen-functions (similar to 2-D domains) complemented by shadow-functions and their associated edge stress intensity functions (ESIFs), which are functions along the edge. These can be complex and are of major engineering importance in composite materials because failure theories

Netta Omer; Zohar Yosibash

2008-01-01

35

Composite structural materials  

NASA Technical Reports Server (NTRS)

The development and application of composite materials to aerospace vehicle structures which began in the mid 1960's has now progressed to the point where what can be considered entire airframes are being designed and built using composites. Issues related to the fabrication of non-resin matrix composites and the micro, mezzo and macromechanics of thermoplastic and metal matrix composites are emphasized. Several research efforts are presented. They are entitled: (1) The effects of chemical vapor deposition and thermal treatments on the properties of pitch-based carbon fiber; (2) Inelastic deformation of metal matrix laminates; (3) Analysis of fatigue damage in fibrous MMC laminates; (4) Delamination fracture toughness in thermoplastic matrix composites; (5) Numerical investigation of the microhardness of composite fracture; and (6) General beam theory for composite structures.

Loewy, Robert G.; Wiberley, Stephen E.

1987-01-01

36

COMPOSITES FROM RECYCLED MATERIALS  

Microsoft Academic Search

A reduction is urgently needed in the quan- tities of industrial and municipal solid waste materials that are being landfilled currently. Major components of municipal solid waste include waste wood, paper. plastics. fly ash. gypsum. and other biomass fibers -- materials that offer great opportunities as recycled ingre- dients in wood composites. This paper dis- cusses possibilities for manufacturing selected

ROGER M. ROWELL; JOHN A. YOUNGQUIST

37

Finite element modelling of anisotropic elasto-plastic timber composite beams with openings  

Microsoft Academic Search

In this paper, constitutive equations to model anisotropic elasto-plastic timber composite beams with openings were formulated and implemented into the finite element (FE) package ABAQUS, via a user-defined subroutine. The Tsai–Hill criterion was applied to judge failure of Oriented Strand Board (OSB) and timber in tension. Both OSB and timber in tension were modelled as linear orthotropic elastic materials, and

Z. W. Guan; E. C. Zhu

2009-01-01

38

Nanostructured composite reinforced material  

DOEpatents

A family of materials wherein nanostructures and/or nanotubes are incorporated into a multi-component material arrangement, such as a metallic or ceramic alloy or composite/aggregate, producing a new material or metallic/ceramic alloy. The new material has significantly increased strength, up to several thousands of times normal and perhaps substantially more, as well as significantly decreased weight. The new materials may be manufactured into a component where the nanostructure or nanostructure reinforcement is incorporated into the bulk and/or matrix material, or as a coating where the nanostructure or nanostructure reinforcement is incorporated into the coating or surface of a "normal" substrate material. The nanostructures are incorporated into the material structure either randomly or aligned, within grains, or along or across grain boundaries.

Seals, Roland D. (Oak Ridge, TN); Ripley, Edward B. (Knoxville, TN); Ludtka, Gerard M. (Oak Ridge, TN)

2012-07-31

39

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

40

Modified Composite Materials Workshop  

NASA Technical Reports Server (NTRS)

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

Dicus, D. L. (compiler)

1978-01-01

41

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

42

Introduction to Advanced Composite Materials  

NSDL National Science Digital Library

This presentation provides an introduction to composite materials and curriculum guidelines. Topics include applications of composites, advantages and disadvantages, and advice for developing a curriculum on advanced composite materials. This document is available for download as a PDF.

Stuart, Joe

43

Structure, thermodynamics, mechanical properties and glassy dynamics in anisotropic polymeric materials  

Microsoft Academic Search

Anisotropic polymeric materials are ubiquitous. They can form via self assembly, external mechanical deformation or by geometric confinement. Important examples of anisotropic polymeric materials include liquid crystalline polymers and elastomers, amorphous rubber networks, confined films and grafted polymer brushes. A common feature of these materials is the anisotropic conformation of the constituent polymer chains which leads to significant modification of

Folusho Taiwo Oyerokun

2005-01-01

44

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

45

Combined thermomagnetic and laser treatments of anisotropic electrical materials  

NASA Astrophysics Data System (ADS)

Methods of improving functional characteristics of soft magnetic anisotropic materials based on the Fe-3% Si alloy and of amorphous ribbons of the Fe81Si7B12 and Fe81Si4B13C2 alloys have been considered. An efficient method of combined local laser treatment and high-frequency thermomagnetic treatment has been developed. These methods provide an optimization of the magnetic domain structure, a twofold-threefold enhancement of magnetic permeability, a significant reduction of magnetic losses (by 25-30%) and of the coercive force (by 30-40%) of soft magnetic anisotropic materials. A physical method and means for controlling efficiency of the local laser treatment of moving bands of electrotechnical materials have been developed.

Dragoshanskii, Yu. N.; Pudov, V. I.; Gubernatorov, V. V.

2011-05-01

46

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

47

Finite element analysis of damaged woven fabric composite materials  

Microsoft Academic Search

Since fiber reinforced composite materials have been used in main parts of structures, an accurate evaluation of their mechanical characteristics becomes very important. Due to their anisotropic nature and complicated architecture, it is very difficult to reveal the damage mechanisms of these materials from the results of mechanical tests. Therefore, there is a need to conduct reliable simulations and analytical

Masaru Zako; Yasutomo Uetsuji; Tetsusei Kurashiki

2003-01-01

48

NDE of composite materials  

NASA Astrophysics Data System (ADS)

The NDE methods applicable to composite material integrity evaluations encompass X-ray and neutron radiography, thermography, holography and interferometry, acoustic emission, ultrasonic, and EM methods. A development status evaluation is presented for each of these techniques. Attention is given to impact-damage C-scans for quasi-isotropic laminates, 3D view of defects of an impact-loaded specimen, and a modified through-transmission C-scan apparatus.

Daniel, I. M.

49

Guided waves in anisotropic and quasi-isotropic aerospace composites: three-dimensional simulation and experiment.  

PubMed

Three-dimensional (3D) elastic wave simulations can be used to investigate and optimize nondestructive evaluation (NDE) and structural health monitoring (SHM) ultrasonic damage detection techniques for aerospace materials. 3D anisotropic elastodynamic finite integration technique (EFIT) has been implemented for ultrasonic waves in carbon fiber reinforced polymer (CFRP) composite laminates. This paper describes 3D EFIT simulations of guided wave propagation in undamaged and damaged anisotropic and quasi-isotropic composite plates. Comparisons are made between simulations of guided waves in undamaged anisotropic composite plates and both experimental laser Doppler vibrometer (LDV) wavefield data and dispersion curves. Time domain and wavenumber domain comparisons are described. Wave interaction with complex geometry delamination damage is then simulated to investigate how simulation tools incorporating realistic damage geometries can aid in the understanding of wave interaction with CFRP damage. In order to move beyond simplistic assumptions of damage geometry, volumetric delamination data acquired via X-ray microfocus computed tomography is directly incorporated into the simulation. Simulated guided wave interaction with the complex geometry delamination is compared to experimental LDV time domain data and 3D wave interaction with the volumetric damage is discussed. PMID:23769180

Leckey, Cara A C; Rogge, Matthew D; Raymond Parker, F

2014-01-01

50

Conduction degradation in anisotropic multi-cracked materials  

NASA Astrophysics Data System (ADS)

The electrical and thermal conduction properties of disordered solids and the possible degradation processes induced by the generation of cracks are central issues in the field of the heterogeneous materials. However, most of the existing theories are unable to consider an arbitrary density of cracks. We obtained an exact result for the fields induced within an elliptic anisotropic inhomogeneity embedded in a different anisotropic (two-dimensional) conductor. Then, we applied it to show that the degradation process strongly depends on the statistical orientational distribution of defects: in particular we theoretically prove that parallel cracks lead to the power law decay log ? ˜ - log N while random oriented cracks lead to the exponential law decay log ? ˜ - N (where ? is the effective conductivity of a region with a large number N of defects), as recently predicted by numerical findings.

Giordano, S.; Palla, P. L.

2012-02-01

51

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Effective Anisotropic Dielectric Properties of Crystal Composites  

Microsoft Academic Search

Transformation field method (TFM) is developed to estimate the anisotropic dielectric properties of crystal composites having arbitrary shapes and dielectric properties of crystal inclusions, whose principal dielectric axis are different from those of anisotropic crystal matrix. The complicated boundary-value problem caused by inclusion shapes is circumvented by introducing a transformation electric field into the crystal composites regions, and the effective

En-Bo Wei; Guo-Qing Gu; Ying-Ming Poon; G. Shin Franklin

2010-01-01

52

Materials Science and Engineering A313 (2001) 115 On the yield condition for anisotropic porous materials  

E-print Network

Materials Science and Engineering A313 (2001) 1­15 On the yield condition for anisotropic porous The plastic yield condition for a porous material that explicitly reflects pore shapes and orientations: Porous material; Plasticity; Yield; Anisotropy www.elsevier.com/locate/msea 1. Introduction It is well

Sevostianov, Igor

53

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

54

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

55

Frequency response of anisotropic ionic polymer metal composites (IPMC) transducers  

NASA Astrophysics Data System (ADS)

The emergence of soft polymer actuators brings a great deal of excitement in the robotics and biomedical engineering community because of the possibilities to easily mimic the motion of living organisms and ability to manipulate living tissue and cells without damaging it. Some of the applications of soft polymer actuators, such as micropumps, require them to operate at high frequency and large displacement, which usually achieved near resonance. It would be beneficial for the designer, if he could easily tailor the frequency response and the resonance frequency to suit the operating conditions. We propose such an effective method of modification of the frequency response of ionic polymer metal composite (IPMC) actuators by introducing an anisotropic roughness on their surface.

Stoimenov, Boyko L.; Rossiter, Jonathan; Mukai, Toshiharu; Asaka, Kinji

2008-03-01

56

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

57

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

58

Anisotropic photoelectric film assembled from mesoporous silica (MS)@CuO@FeS2 composite microspheres for improving photoelectric conversion.  

PubMed

We report a novel strategy for the fabrication of mesoporous silica (MS)@CuO@FeS2 composite microsphere-based anisotropic films that combine the advantages of the CuO and FeS2 materials to improve photoelectric conversion. This was achieved by aligning MS@CuO@FeS2 composite microspheres in a cross-linked gel under a homogeneous magnetic field. The MS@CuO@FeS2 composite microspheres, which were synthesized by a simple layer-by-layer (LbL) self-assembly technique together with a solvothermal method, can absorb a wide range of light and exhibit ferromagnetic properties. In addition, the resulting MS@CuO@FeS2 composite microsphere-based anisotropic film shows photoelectric anisotropy. Such systems are promising for improving the performance of solar cells. PMID:23660025

Zong, Jie; Zhu, Yihua; Shen, Jianhua; Yang, Xiaoling; Li, Chunzhong

2013-07-15

59

Quantifying the Nonlinear, Anisotropic Material Response of Spinal Ligaments  

NASA Astrophysics Data System (ADS)

Spinal ligaments may be a significant source of chronic back pain, yet they are often disregarded by the clinical community due to a lack of information with regards to their material response, and innervation characteristics. The purpose of this dissertation was to characterize the material response of spinal ligaments and to review their innervation characteristics. Review of relevant literature revealed that all of the major spinal ligaments are innervated. They cause painful sensations when irritated and provide reflexive control of the deep spinal musculature. As such, including the neurologic implications of iatrogenic ligament damage in the evaluation of surgical procedures aimed at relieving back pain will likely result in more effective long-term solutions. The material response of spinal ligaments has not previously been fully quantified due to limitations associated with standard soft tissue testing techniques. The present work presents and validates a novel testing methodology capable of overcoming these limitations. In particular, the anisotropic, inhomogeneous material constitutive properties of the human supraspinous ligament are quantified and methods for determining the response of the other spinal ligaments are presented. In addition, a method for determining the anisotropic, inhomogeneous pre-strain distribution of the spinal ligaments is presented. The multi-axial pre-strain distributions of the human anterior longitudinal ligament, ligamentum flavum and supraspinous ligament were determined using this methodology. Results from this work clearly demonstrate that spinal ligaments are not uniaxial structures, and that finite element models which account for pre-strain and incorporate ligament's complex material properties may provide increased fidelity to the in vivo condition.

Robertson, Daniel J.

60

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

61

Composite structural materials  

NASA Technical Reports Server (NTRS)

A decade long program to develop critical advanced composite technology in the areas of physical properties, structural concept and analysis, manufacturing, reliability, and life predictions is reviewed. Specific goals are discussed. The status of the chemical vapor deposition effects on carbon fiber properties; inelastic deformation of metal matrix laminates; fatigue damage in fibrous MMC laminates; delamination fracture toughness in thermoplastic matrix composites; and numerical analysis of composite micromechanical behavior are presented.

Loewy, Robert G.; Wiberley, Stephen E.

1988-01-01

62

Composite Materials: Sticks and Glue  

NSDL National Science Digital Library

This learning activity will provide a good example of "the effect on strength and stiffness of a material when it is manufactured as a composite." Popsicle sticks will be used to demonstrate the difference between singular materials and composite materials. Students will be able to see the added benefits of using composite materials. This activity would be suitable for elementary school through college level students, with each grade level gaining different educational benefits. The lesson should take from 5 to 20 minutes, depending on grade level. This document will serve as a framework for instructors and may be downloaded in PDF format.

Stoebe, Thomas G.

63

Anisotropic Compositional Expansion and Chemical Potential for Amorphous Lithiated Silicon under Stress Tensor  

PubMed Central

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

64

Composite structural materials. [aircraft structures  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

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

Reversibly assembled cellular composite materials.  

PubMed

We introduce composite materials made by reversibly assembling a three-dimensional lattice of mass-produced carbon fiber-reinforced polymer composite parts with integrated mechanical interlocking connections. The resulting cellular composite materials can respond as an elastic solid with an extremely large measured modulus for an ultralight material (12.3 megapascals at a density of 7.2 milligrams per cubic centimeter). These materials offer a hierarchical decomposition in modeling, with bulk properties that can be predicted from component measurements and deformation modes that can be determined by the placement of part types. Because site locations are locally constrained, structures can be produced in a relative assembly process that merges desirable features of fiber composites, cellular materials, and additive manufacturing. PMID:23950496

Cheung, Kenneth C; Gershenfeld, Neil

2013-09-13

67

Effect of initial flaw shape on crack extension in orthotropic composite materials  

NASA Technical Reports Server (NTRS)

An analytical study is presented showing the effects of the notch tip geometry on the location and direction of crack growth from an existing notch in a unidirectional fibrous composite modelled as a homogeneous, anisotropic, elastic material. Anisotropic elasticity and the normal stress ratio theory are used to study crack growth from elliptical notches in unidirectional composites. Sharp cracks, circular holes, and ellipses are studied under far-field tension and shear loading. Limited comparisons are made showing good correlation with experimental results.

Gurdal, Z.; Herakovich, C. T.

1987-01-01

68

Acoustics of two-component porous materials with anisotropic tortuosity  

NASA Astrophysics Data System (ADS)

The paper is devoted to the analysis of monochromatic waves in two-component poroelastic materials described by a Biot-like model whose stress-strain relations are isotropic but the permeability is anisotropic. This anisotropy is induced by the anisotropy of the tortuosity which is given by a second order symmetric tensor. This is a new feature of the model while in earlier papers only isotropic permeabilities were considered. We show that this new model describes four modes of propagation. For our special choice of orientation of the direction of propagation these are two pseudo longitudinal modes P1 and P2, one pseudo transversal mode S2 and one transversal mode S1. The latter becomes also pseudo transversal in the general case of anisotropy. We analyze the speeds of propagation and the attenuation of these waves as well as the polarization properties in dependence on the orientation of the principal directions of the tortuosity. We indicate the practical importance of different shear (transversal) modes of propagation in a possible new nondestructive test of geophysical materials.

Albers, Bettina; Wilmanski, Krzysztof

2012-11-01

69

Piezoelectric composite materials  

NASA Technical Reports Server (NTRS)

A laminated structural devices has the ability to change shape, position and resonant frequency without using discrete motive components. The laminate may be a combination of layers of a piezoelectrically active, nonconductive matrix material. A power source selectively places various levels of charge in electrically conductive filaments imbedded in the respective layers to produce various configurations in a predetermined manner. The layers may be electrically conductive having imbedded piezoelectrically active filaments. A combination of layers of electrically conductive material may be laminated to layers of piezoelectrically active material.

Kiraly, L. J. (inventor)

1983-01-01

70

Study of anisotropic moisture diffusion in paper material  

NASA Astrophysics Data System (ADS)

The influence of moisture on the final use of paper has been a critical issue for papermakers. In this thesis, we studied transient and steady state moisture diffusion in paper under different humidity conditions and its relationship to sheet structure. Moisture transport through this medium occurs by a number of mechanisms, which the most important are: diffusion through the pores, diffusion of condensed water through the cell-wall of the fibers, surface diffusion and capillary transport. In the first part of this work, we investigated the sorption of moisture by paper sheets exposed to rapid changes in the external humidity. We found that transient moisture transported in paper material is Non-Fickian, most likely being caused by two sequential diffusion steps: the first being a rapid diffusion through the pores followed by a slow diffusion through the fibers/cell wall material. External boundary layers cause further departures from Fickian sorption. The porous structure of paper significantly impacts its diffusion characteristics. At low to moderate moisture contents, it is the pore space that conducts water vapor by diffusion: transport is therefore proportional to the sheet porosity and is inversely proportional to the tortuosity. Pulp refining reduces the porosity and increases tortuosity, decreasing the moisture diffusivity. Since the pore structure is strongly anisotropic, reflecting the layered structure of paper, diffusion is also anisotropic and is usually greater in the lateral (in-plane or XY) dimensions as compared to the transverse (through plane or ZD) dimension. In machine made paper, there could be a weak dependence on the in-plane fiber orientation giving rise to higher diffusion in the machine direction (MD) as compared to the cross machine direction, (CD). Parameters describing the moisture diffusivity in paper are necessary for calculating transport rates and moisture profiles. Therefore, we present diffusion parameters for moisture transport through the pore space (Dp) and the non-linear diffusivity of condensed phase moisture (D q0 and m) for sheets made from bleached kraft softwood pulps refined to different levels. We demonstrate the utility of the diffusion parameters by estimating moisture profiles through a stack of sheets using a mathematical model for transient moisture transport. The model predictions agreed with our measurements of the moisture profiles showing the usefulness of these diffusion parameters. Keywords: moisture diffusion, paper, water vapor, bound water.

Massoquete, A.

71

Characterizing dielectric tensors of anisotropic materials from a single measurement  

NASA Astrophysics Data System (ADS)

Ellipsometry techniques look at changes in polarization states to measure optical properties of thin film materials. A beam reflected from a substrate measures the real and imaginary parts of the index of the material represented as n and k, respectively. Measuring the substrate at several angles gives additional information that can be used to measure multilayer thin film stacks. However, the outstanding problem in standard ellipsometry is that it uses a limited number of incident polarization states (s and p). This limits the technique to isotropic materials. The technique discussed in this paper extends the standard process to measure anisotropic materials by using a larger set of incident polarization states. By using a polarimeter to generate several incident polarization states and measure the polarization properties of the sample, ellipsometry can be performed on biaxial materials. Use of an optimization algorithm in conjunction with biaxial ellipsometry can more accurately determine the dielectric tensor of individual layers in multilayer structures. Biaxial ellipsometry is a technique that measures the dielectric tensors of a biaxial substrate, single-layer thin film, or multi-layer structure. The dielectric tensor of a biaxial material consists of the real and imaginary parts of the three orthogonal principal indices (n x + ikx, ny +iky and nz + i kz) as well as three Euler angles (alpha, beta and gamma) to describe its orientation. The method utilized in this work measures an angle-of-incidence Mueller matrix from a Mueller matrix imaging polarimeter equipped with a pair of microscope objectives that have low polarization properties. To accurately determine the dielectric tensors for multilayer samples, the angle-of-incidence Mueller matrix images are collected for multiple wavelengths. This is done in either a transmission mode or a reflection mode, each incorporates an appropriate dispersion model. Given approximate a priori knowledge of the dielectric tensor and film thickness, a Jones reflectivity matrix is calculated by solving Maxwell's equations at each surface. Converting the Jones matrix into a Mueller matrix provides a starting point for optimization. An optimization algorithm then finds the best fit dielectric tensor based on the measured angle-of-incidence Mueller matrix image. This process can be applied to polarizing materials, birefringent crystals and the multilayer structures of liquid crystal displays. In particular, the need for such accuracy in liquid crystal displays is growing as their applications in industry evolve.

Smith, Paula Kay

72

Vibrational dynamic materials and composites  

NASA Astrophysics Data System (ADS)

In this paper, the concept of dynamic materials is briefly outlined and exemplified following the work of the author published during the last decade. Then, a special kind of kinetic dynamic materials is introduced, the so-called 'vibrational dynamics' material with vibrational composites being its special case. A parametrically produced, vibrational dynamic material definition is introduced. Among such materials can also be a range of known systems, which can be considered to be capable of changing their properties under the action of vibration. As a case in point, an unusual dynamic material is considered, in the form of a pipe conveying a pulsating fluid.

Blekhman, I. I.

2008-11-01

73

Fracturing of ductile anisotropic multilayers: influence of material strength  

NASA Astrophysics Data System (ADS)

Fractures in rocks deformed under dominant ductile conditions typically form simultaneously with viscous flow. Material strength plays a fundamental role on fracture development in such cases, since fracture propagation can be strongly reduced by the high energy absorption of the material. Additionally, the degree and nature of anisotropy can influence the orientation and type of resulting fractures. In this study, four plasticine multilayer models have been deformed under coaxial boundary conditions to investigate the influence of strength and anisotropy on the formation of fracture networks. The experiments were made of different mixtures and presented two types of anisotropy: composite and composite-intrinsic. The transition from non-localised deformation to systems where fracture networks control deformation accommodation is determined by the ability of the material to dissipate the external work and relax the elastic strain during loading, either by viscous flow or by coeval flow and failure. Tension cracks grow in experiments with composite anisotropy, giving rise to a network of shear fractures when they collapse and coalesce with progressive deformation. The presence of an additional intrinsic anisotropy enhances the direct nucleation of shear fractures, whose propagation and final length depend on the rigidity of the medium. Material strength increases the fracture maximum displacement (dmax) to fracture length (L) ratio, and the resulting values are significantly higher than those from fractures in elastic-brittle rocks. This is associated with the low propagation rates of fractures in rocks undergoing ductile deformation.

Gomez-Rivas, E.; Griera, A.; Llorens, M.-G.

2015-01-01

74

A new method for anisotropic materials characterization based on phased-array ultrasonic transducers technology  

SciTech Connect

A method for materials characterization based on the utilization of a ultrasonic array transducer of conical shape has been developed at the CEA. The specific design of this transducer allows the generation and the detection of leaky surface acoustic waves (LSAW) in an efficient way. Additionally, anisotropic materials can be investigated in several azimuthal directions without any mechanical movement. The characterization process relies on the velocity measurement of the LSAW. Experimental results on both isotropic an anisotropic material are reported.

Frenet, D.; Calmon, P.; Paradis, L. [Commissariat a l'Energie Atomique/CEREM, Saclay (France); Ouaftouh, M. [Institut d'Electronique et de Microelectronique du Nord, Universite de Valenciennes (France)

1999-12-02

75

Multilayer Electroactive Polymer Composite Material  

NASA Technical Reports Server (NTRS)

An electroactive material comprises multiple layers of electroactive composite with each layer having unique dielectric, electrical and mechanical properties that define an electromechanical operation thereof when affected by an external stimulus. For example, each layer can be (i) a 2-phase composite made from a polymer with polarizable moieties and an effective amount of carbon nanotubes incorporated in the polymer for a predetermined electromechanical operation, or (ii) a 3-phase composite having the elements of the 2-phase composite and further including a third component of micro-sized to nano-sized particles of an electroactive ceramic incorporated in the polymer matrix.

Ounaies, Zoubeida (Inventor); Park, Cheol (Inventor); Harrison, Joycelyn S. (Inventor); Holloway, Nancy M. (Inventor); Draughon, Gregory K. (Inventor)

2011-01-01

76

Ski Technology And Composite Materials  

NSDL National Science Digital Library

The following resource is from Lessonopoly, which has created student activities and lesson plans to support the video series, Science of the Olympic Winter Games, created by NBC Learn and the National Science Foundation. Featuring exclusive footage from NBC Sports and contributions from Olympic athletes and NSF scientists, the series will help teach your students valuable scientific concepts. Students will learn the basic engineering issues related to ski design. They will learn about composite materials and polymer materials. Also, students will create and test a composite material.

2010-01-01

77

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

78

Composite materials for space applications  

NASA Technical Reports Server (NTRS)

The objectives of the program were to: generate mechanical, thermal, and physical property test data for as-fabricated advanced materials; design and fabricate an accelerated thermal cycling chamber; and determine the effect of thermal cycling on thermomechanical properties and dimensional stability of composites. In the current program, extensive mechanical and thermophysical property tests of various organic matrix, metal matrix, glass matrix, and carbon-carbon composites were conducted, and a reliable database was constructed for spacecraft material selection. Material property results for the majority of the as-fabricated composites were consistent with the predicted values, providing a measure of consolidation integrity attained during fabrication. To determine the effect of thermal cycling on mechanical properties, microcracking, and thermal expansion behavior, approximately 500 composite specimens were exposed to 10,000 cycles between -150 and +150 F. These specimens were placed in a large (18 cu ft work space) thermal cycling chamber that was specially designed and fabricated to simulate one year low earth orbital (LEO) thermal cycling in 20 days. With this rate of thermal cycling, this is the largest thermal cycling unit in the country. Material property measurements of the thermal cycled organic matrix composite laminate specimens exhibited less than 24 percent decrease in strength, whereas, the remaining materials exhibited less than 8 percent decrease in strength. The thermal expansion response of each of the thermal cycled specimens revealed significant reduction in hysteresis and residual strain, and the average CTE values were close to the predicted values.

Rawal, Suraj P.; Misra, Mohan S.; Wendt, Robert G.

1990-01-01

79

Composite material impregnation unit  

NASA Technical Reports Server (NTRS)

This memorandum presents an introduction to the NASA multi-purpose prepregging unit which is now installed and fully operational at the Langley Research Center in the Polymeric Materials Branch. A description of the various impregnation methods that are available to the prepregger are presented. Machine operating details and protocol are provided for its various modes of operation. These include, where appropriate, the related equations for predicting the desired prepreg specifications. Also, as the prepregger is modular in its construction, each individual section is described and discussed. Safety concerns are an important factor and a chapter has been included that highlights the major safety features. Initial experiences and observations for fiber impregnation are described. These first observations have given great insight into the areas of future work that need to be addressed. Future memorandums will focus on these individual processes and their related problems.

Wilkinson, S. P.; Marchello, J. M.; Johnston, N. J.

1993-01-01

80

Fiber composite materials technology development  

SciTech Connect

The FY1980 technical accomplishments from the Lawrence Livermore National laboratory (LLNL) for the Fiber Composite Materials Technology Development Task fo the MEST project are summarized. The task is divided into three areas: Engineering data base for flywheel design (Washington University will report this part separately), new materials evaluation, and time-dependent behavior of Kevlar composite strands. An epoxy matrix was formulated which can be used in composites for 120/sup 0/C service with good processing and mechanical properties. Preliminary results on the time-dependent properties of the Kevlar 49/epoxy strands indicate: Fatigue loading, as compared to sustained loading, drastically reduces the lifetime of a Kevlar composie; the more the number of on-off load cycles, the less the lifetime; and dynamic fatigue of the Kevlar composite can not be predicted by current damage theories such as Miner's Rule.

Chiao, T.T.

1980-10-23

81

Computation of Anisotropic Bi-Material Interfacial Fracture Parameters and Delamination Creteria  

NASA Technical Reports Server (NTRS)

This report documents the recent developments in methodologies for the evaluation of the integrity and durability of composite structures, including i) the establishment of a stress-intensity-factor based fracture criterion for bimaterial interfacial cracks in anisotropic materials (see Sec. 2); ii) the development of a virtual crack closure integral method for the evaluation of the mixed-mode stress intensity factors for a bimaterial interfacial crack (see Sec. 3). Analytical and numerical results show that the proposed fracture criterion is a better fracture criterion than the total energy release rate criterion in the characterization of the bimaterial interfacial cracks. The proposed virtual crack closure integral method is an efficient and accurate numerical method for the evaluation of mixed-mode stress intensity factors.

Chow, W-T.; Wang, L.; Atluri, S. N.

1998-01-01

82

Dense, finely, grained composite materials  

DOEpatents

Dense, finely grained composite materials comprising one or more ceramic phase or phase and one or more metallic and/or intermetallic phase or phases are produced by combustion synthesis. Spherical ceramic grains are homogeneously dispersed within the matrix. Methods are provided, which include the step of applying mechanical pressure during or immediately after ignition, by which the microstructures in the resulting composites can be controllably selected.

Dunmead, Stephen D. (Davis, CA); Holt, Joseph B. (San Jose, CA); Kingman, Donald D. (Danville, CA); Munir, Zuhair A. (Davis, CA)

1990-01-01

83

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

84

Tunable positive liquid coefficient of an anisotropically conductive carbon nanotube-polymer composite  

Microsoft Academic Search

The anisotropic carbon nanotubes (CNTs)\\/polycarbonate (PC)\\/polyethylene (PE) conductive polymer composite possesses a strong\\u000a positive liquid coefficient (PLC), which can be attributed to the microfibrillar structure in the composite. A facile method,\\u000a namely the isothermal treatment (IT), is proposed to manipulate the PLC of the CNTs\\/PC\\/PE composite. Different PLC intensities\\u000a are achieved by controlling IT temperature and time. The PLC can

Jie-Feng Gao; Ding-Xiang Yan; Hua-Dong Huang; Xiang-Bu Zeng; Wei-Qin Zhang; Zhong-Ming Li

85

Delamination growth in composite materials  

NASA Technical Reports Server (NTRS)

Research related to growth of an imbedded through-width delamination (ITWD) in a compression loaded composite structural element is presented. Composites with widely different interlaminar fracture resistance were examined, viz., graphite/epoxy (CYCOM 982) and graphite/PEEK (APC-2). The initial part of the program consisted of characterizing the material in tension, compression and shear mainly to obtain consistent material properties for analysis, but also as a check of the processing method developed for the thermoplastic APC-2 material. The characterization of the delamination growth in the ITWD specimen, which for the unidirectional case is essentially a mixed Mode 1 and 2 geometry, requires verified mixed-mode growth criteria for the two materials involved. For this purpose the main emphasis during this part of the investigation was on Mode 1 and 2 fracture specimens, namely the Double Cantilever Beam (DCB) and End Notched Flexure (ENF) specimens.

Gillespie, J. W., Jr.; Carlson, L. A.; Pipes, R. B.; Rothschilds, R.; Trethewey, B.; Smiley, A.

1985-01-01

86

Characterization of anisotropic elastic constants of silicon-carbide particulate reinforced aluminum metal matrix composites; Part 2: Theory  

SciTech Connect

The effective elastic constants of composite materials contain arbitrarily oriented ellipsoidal fibers were derived using the concept of orientation-dependent average fields and the strain concentration factor tensors. Under the prescribed boundary condition, the concentration factor was evaluated by the Mori-Tanaka method and the Eshelby's equivalent inclusion principle. The fourth-rank tensor expression for the elastic stiffnesses was recast into matrix form for easier numerical computations. The theoretical model developed was applied to the computation of the anisotropic elastic constants of the extruded Al/SiC[sub p] composites considered in Part 1 of this series. Good agreement was found between the model predictions and the ultrasonic measurement results. Comparisons with the Hashin-Shtrikman (H-S) bounds for isotropic composites were also presented. It was found that while the H-S lower bound predicted the out-of-plane properties, it generally gave a poor estimate for the in-plane properties of these composites.

Jeong, H. (Agency for Defense Development, DaeJon (Korea, Republic of)); Hsu, D.K. (Iowa State Univ., Ames, IA (United States). Center for Nondestructive Evaluation); Shannon, R.E. (Westinghouse Science Technology Center, Pittsburgh, PA (United States). Materials Reliability Dept.); Liaw, P.K. (Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering)

1994-04-01

87

Energy producing waste material composition  

SciTech Connect

Waste materials from the conversion of iron ore to pig iron or steel combine with a reducing metal, such as aluminum or magnesium, and a small portion of a mineral acid to form a reaction mixture which gives a heat output superior to many conventional fuels. The materials are processed in several steps to produce either a shaped or loose composition, a portion of which is then heated to a reaction temperature. Retardants for the reaction may be added.

Cundari, S.M.; Deardorff, P.A.; Wood, R.C.

1980-06-17

88

Anisotropic polymer composites synthesized by immobilizing cellulose nanocrystal suspensions specifically oriented under magnetic fields.  

PubMed

Novel polymer composites reinforced with an oriented cellulose nanocrystal (CNC) assembly were prepared from suspensions of CNC in aqueous 2-hydroxyethyl methacrylate (HEMA) via magnetic field application to the suspensions followed by polymerization treatment. The starting suspensions used at ?6 wt % CNC separated into an upper isotropic phase and a lower anisotropic (chiral nematic) one in the course of quiescent standing. A static or rotational magnetic field was applied to the isolated isotropic and anisotropic phases. UV-induced polymerization of HEMA perpetuated the respective states of magnetic orientation invested for the CNC dispersions to yield variously oriented CNC/poly(2-hydroxyethyl methacrylate) composites. The structural characterization was carried out by use of X-ray diffractometry and optical and scanning electron microscopy. The result indicated that CNCs were aligned in the composites distinctively according to the static or rotational magnetic application when the anisotropic phases were used, whereas such a specific CNC orientation was not appreciable when the isotropic phases were sampled. This marks out effectiveness of a coherent response of CNCs in the mesomorphic assembly. In dynamic mechanical experiments in tensile or compressive mode, we observed a clear mechanical anisotropy for the polymer composites synthesized from wholly anisotropic suspensions under static or rotational magnetization. The higher modulus (in compression) was detected for a composite reinforced by locking-in the uniaxial CNC alignment attainable through conversion of the initial chiral nematic phase into a nematic phase in the rotational magnetic field. PMID:25390070

Tatsumi, Mio; Kimura, Fumiko; Kimura, Tsunehisa; Teramoto, Yoshikuni; Nishio, Yoshiyuki

2014-12-01

89

Durability of aircraft composite materials  

NASA Technical Reports Server (NTRS)

Confidence in the long term durability of advanced composites is developed through a series of flight service programs. Service experience is obtained by installing secondary and primary composite components on commercial and military transport aircraft and helicopters. Included are spoilers, rudders, elevators, ailerons, fairings and wing boxes on transport aircraft and doors, fairings, tail rotors, vertical fins, and horizontal stabilizers on helicopters. Materials included in the evaluation are boron/epoxy, Kevlar/epoxy, graphite/epoxy and boron/aluminum. Inspection, maintenance, and repair results for the components in service are reported. The effects of long term exposure to laboratory, flight, and outdoor environmental conditions are reported for various composite materials. Included are effects of moisture absorption, ultraviolet radiation, and aircraft fuels and fluids.

Dextern, H. B.

1982-01-01

90

Joining of polymer composite materials  

SciTech Connect

Under ideal conditions load bearing structures would be designed without joints, thus eliminating a source of added weight, complexity and weakness. In reality the need for accessibility, repair, and inspectability, added to the size limitations imposed by the manufacturing process and transportation/assembly requirements mean that some minimum number of joints will be required in most structures. The designer generally has two methods for joining fiber composite materials, adhesive bonding and mechanical fastening. As the use of thermoplastic materials increases, a third joining technique -- welding -- will become more common. It is the purpose of this document to provide a review of the available sources pertinent to the design of joints in fiber composites. The primary emphasis is given to adhesive bonding and mechanical fastening with information coming from documentary sources as old as 1961 and as recent as 1989. A third, shorter section on composite welding is included in order to provide a relatively comprehensive treatment of the subject.

Magness, F.H.

1990-11-01

91

Mechanical properties of composite materials  

NASA Technical Reports Server (NTRS)

A composite material incorporates high strength, high modulus fibers in a matrix (polymer, metal, or ceramic). The fibers may be oriented in a manner to give varying in-plane properties (longitudinal, transverse-stress, strain, and modulus of elasticity). The lay-up of the composite laminates is such that a center line of symmetry and no bending moment exist through the thickness. The laminates are tabbed, with either aluminum or fiberglass, and are ready for tensile testing. The determination of the tensile properties of resin matrix composites, reinforced by continuous fibers, is outlined in ASTM standard D 3039, Tensile Properties of Oriented Fiber Composites. The tabbed flat tensile coupons are placed into the grips of a tensile machine and load-deformation curves plotted. The load-deformation data are translated into stress-strain curves for determination of mechanical properties (ultimate tensile strength and modulus of elasticity).

Thornton, H. Richard; Cornwell, L. R.

1993-01-01

92

An anisotropic gradient damage model for quasi-brittle materials  

Microsoft Academic Search

An anisotropic continuum damage model based on the microplane concept is elaborated. Scalar damage laws are formulated on several individual microplanes representing the planes of potential failure. These uniaxial constitutive laws can be cast into a fourth-order damage formulation such that anisotropy of the overall constitutive law is introduced in a natural fashion. Strain gradients are incorporated in the constitutive

Ellen Kuhl; Ekkehard Ramm; René de Borst

2000-01-01

93

Analytical calculation of intrinsic shielding effectiveness for isotropic and anisotropic materials based on measured electrical parameters  

NASA Astrophysics Data System (ADS)

This contribution contains the mechanisms for calculation of magnetic shielding effectiveness from material samples, based on measured electrical parameters. For this, measurement systems for the electrical conductivity of high and low conductive material samples with respect to the direction of current flow are presented and discussed. Also a definition of isotropic and anisotropic materials with electrical circuit diagrams is given. For prediction of shielding effectiveness for isotropic and anisotropic materials, several analytical models are presented. Also adaptions to gain a near field solution are part of this contribution. All analytical models will also be validated with an adequate measurement system.

Kühn, M.; John, W.; Weigel, R.

2014-11-01

94

Dynamic permeability in soft magnetic composite materials  

NASA Astrophysics Data System (ADS)

This article reports on an isotropic model of the magnetic susceptibility based on an average field theory and proposes to predict the dynamic behaviors of powder magnetic materials. It was essentially built around a so-called effective demagnetizing factor capable of taking the particle shapes into account. So, for a population of randomly distributed particles of anisotropic shapes like, for instance, needles or flakes, we show that the effective demagnetizing factor of this population of particles can be significantly lowered with regard to the well known value of 1/3 classically used to represent the isotropy state. This phenomenon is interpreted as the natural tendency of particles to form clusters to which a moving demagnetizing factor must be assigned. Taking then the aggregation process of particles into account, the ability of the model to predict the dynamic properties of many composite magnetic materials is successfully demonstrated. Our development is illustrated by experimental results concerning a nickel-zinc ferrimagnetic (Ni0.7Zn0.3Fe2O4) powder.

Chevalier, A.; Le Floc'h, M.

2001-10-01

95

Hamiltonian system based Saint Venant solutions for multi-layered composite plane anisotropic plates  

Microsoft Academic Search

This paper presents Hamiltonian system based Saint Venant solutions for the problem of multi-layered composite plane anisotropic plates. A mixed energy variational principle is proposed, and dual equations are derived in the symplectic space. The schemes of separation of variables and eigenfunction expansion, instead of the traditional semi-inverse method, are implemented, and compatibility conditions at interfaces are formulated by dual

Weian Yao; Haitian Yang

2001-01-01

96

Liquid crystalline (cyanoethylpropyl)cellulose and its optically anisotropic composites with acrylic polymers  

Microsoft Academic Search

Described herein are anisotropic polymer composites, made up of (cyanoethylpropyl)cellulose (CEPC) and acrylic polymer. A band texture (which can be seen with a polarisation microscope) forms in CEPC and its lyotropic solutions in acrylic monomer after orientation as a result of relaxation phenomena. The photopolymerisation of acrylic monomer (acrylic or methacrylic acid) in an oriented lyotropic solution of CEPC ‘freezes’

Lidia Okrasa; Jacek Ulanski; Gisèle Boiteux

2002-01-01

97

Determining thermal diffusivity components in thick anisotropic composites by IR thermography  

NASA Astrophysics Data System (ADS)

The paper contains theoretical and experimental thermal diffusivity data on anisotropic carbon and glass fiber reinforced composite laminates up to 5 mm thick. The effectiveness of the theory is evaluated by using a 3D numerical model. Both spot-mask and slit-mask techniques for determining lateral thermal diffusivity components are analyzed.

Vavilov, Vladimir P.; Burleigh, Douglas D.

2006-04-01

98

Continuum Damage Mechanics, Anisotropy and Damage Deactivation for Brittle Materials Like Concrete and Ceramic Composites  

Microsoft Academic Search

The main lines of a Continuum Damage Mechanics Modelling are reviewed, for applications to brittle materials treated as elastic damageable ones.The proposed damage models consider in the same framework the cases of initially isotropic materials like concrete and anisotropic composites.Attention is focused on the damage deactivation effects and on the possibility to describe irreversible strains directly associated to the damaging

J. L. Chaboche; P. M. Lesne; J. F. Maire

1995-01-01

99

Graphene-based composite materials.  

PubMed

Graphene sheets--one-atom-thick two-dimensional layers of sp2-bonded carbon--are predicted to have a range of unusual properties. Their thermal conductivity and mechanical stiffness may rival the remarkable in-plane values for graphite (approximately 3,000 W m(-1) K(-1) and 1,060 GPa, respectively); their fracture strength should be comparable to that of carbon nanotubes for similar types of defects; and recent studies have shown that individual graphene sheets have extraordinary electronic transport properties. One possible route to harnessing these properties for applications would be to incorporate graphene sheets in a composite material. The manufacturing of such composites requires not only that graphene sheets be produced on a sufficient scale but that they also be incorporated, and homogeneously distributed, into various matrices. Graphite, inexpensive and available in large quantity, unfortunately does not readily exfoliate to yield individual graphene sheets. Here we present a general approach for the preparation of graphene-polymer composites via complete exfoliation of graphite and molecular-level dispersion of individual, chemically modified graphene sheets within polymer hosts. A polystyrene-graphene composite formed by this route exhibits a percolation threshold of approximately 0.1 volume per cent for room-temperature electrical conductivity, the lowest reported value for any carbon-based composite except for those involving carbon nanotubes; at only 1 volume per cent, this composite has a conductivity of approximately 0.1 S m(-1), sufficient for many electrical applications. Our bottom-up chemical approach of tuning the graphene sheet properties provides a path to a broad new class of graphene-based materials and their use in a variety of applications. PMID:16855586

Stankovich, Sasha; Dikin, Dmitriy A; Dommett, Geoffrey H B; Kohlhaas, Kevin M; Zimney, Eric J; Stach, Eric A; Piner, Richard D; Nguyen, SonBinh T; Ruoff, Rodney S

2006-07-20

100

Surface effects on photopolymerization induced anisotropic phase separation in liquid crystal and polymer composites  

SciTech Connect

The surface effects on the anisotropic phase separation in photopolymerization induced phase separation of liquid crystal and polymer composites have been studied. It was found that the surface interaction between the substrate and the prepolymer and/or liquid crystal plays a crucial role in anisotropic phase separation. A theoretical model is suggested to describe the surface effects by adapting a phenomenological free energy approach. The formation of polymer layer in the presence of surface effects can be understood as competition between entropic flow and surface directed flow of polymer and liquid crystal.

Jin, Min Young; Lee, Tae-Hee; Jung, Jong-Wook; Kim, Jae-Hoon [Research Institute of Information Display, Hanyang University, Seoul 133-791 (Korea, Republic of); Department of Information Display Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Department of Electronics and Computer Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)

2007-05-07

101

Method of determining load in anisotropic non-crystalline materials using energy flux deviation  

NASA Technical Reports Server (NTRS)

An ultrasonic wave is applied to an anisotropic sample material in an initial direction and the intensity of the ultrasonic wave is measured on an opposite surface of the sample material by two adjacent receiving points located in an array of receiving points. A ratio is determined between the measured intensities of two adjacent receiving points, the ratio being indicative of an angle of flux deviation from the initial direction caused by an unknown applied load. This determined ratio is then compared to a plurality of ratios 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. (inventor); Kriz, Ronald D. (inventor); Fitting, Dale W. (inventor)

1994-01-01

102

Asymmetric Dielectric Elastomer Composite Material  

NASA Technical Reports Server (NTRS)

Embodiments of the invention provide a dielectric elastomer composite material comprising a plurality of elastomer-coated electrodes arranged in an assembly. Embodiments of the invention provide improved force output over prior DEs by producing thinner spacing between electrode surfaces. This is accomplished by coating electrodes directly with uncured elastomer in liquid form and then assembling a finished component (which may be termed an actuator) from coated electrode components.

Stewart, Brian K. (Inventor)

2014-01-01

103

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

2006-10-11

104

Measurement of the intrinsic attenuation of longitudinal waves in anisotropic material from uncorrected raw data.  

PubMed

Among the physical parameters characterising the interaction of the ultrasonic beam with its supporting medium, ultrasonic attenuation is an important input parameter to simulate wave propagation and defect-beam phenomena. The measurement of the intrinsic attenuation in anisotropic material however is a difficult task. The paper presents an approach to determine intrinsic attenuation in anisotropic materials such as austenitic stainless steel welds and cladding. It deals with improvements on the initial device, based on measurements on two samples with different thicknesses (10mm and 20mm). A previous paper presented preliminary results with this new approach for isotropic materials. PMID:23601966

Seldis, Thomas

2013-09-01

105

MATERIAL COMPOSITIONS FOR REINFORCING IONIC POLYMER COMPOSITES  

Technology Transfer Automated Retrieval System (TEKTRAN)

The invention is related to the preparation of an ionic polymer composition containing soy spent flakes, defatted soy flour, or soy protein concentrate composite reinforcement. The composite composition is formed by incorporating soy spent flakes, defatted soy flour, or soy protein concentrate comp...

106

Plastic yield surfaces of anisotropic porous materials in terms of effective electric conductivities  

E-print Network

Plastic yield surfaces of anisotropic porous materials in terms of effective electric University, 204 Anderson Hall, Medford, MA 02155, USA Received 10 December 2004 Abstract Plastic yield analysis of a plastic flow in a porous material. Interna- tional Journal of Plasticity 18, 1649­1659] show

Sevostianov, Igor

107

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

108

A study of interface crack branching in dissimilar anisotropic bimaterial composites including thermal effects  

NASA Astrophysics Data System (ADS)

The interface crack branching phenomena, including thermal effects, has been investigated by using complex variable method and Stroh's dislocation theory, extended to thermo-elasticity in matrix notation. As one of the most catastrophic failure modes in structures like laminated and sandwich composites in aerospace and marine construction, thin film in electronic packaging, rotators in high speed engine of aircraft and reactor in nuclear power station, the study of interface crack branching has become a topic not only having theoretical importance, but also having practical significance. A unified approach is presented to address the thermoelastic interface crack problems in dissimilar anisotropic bimaterial composites, and a compact closed form solution is formulated by analytical continuation principle of complex analysis. Employing the contour integral method, an explicit solution to the interaction between the dislocations and the interface crack is obtained. By modeling the branched portion as a continuous distribution of the dislocations, the thermoelastic interface crack branching problem is then converted to a set of semi-coupled singular integral equations and solved by Gauss-Jacobi integration schemes. The influence of material property mismatches between the two constituents and the thermal loading effects on the interface crack branching are demonstrated by extensive numerical simulation. Some useful criteria for predicting the interface crack branching growth and guidance for optimal composites design are suggested. Further, a contact model to eliminate the overlapping between the two surfaces of an interface crack is also proposed and some new parameters which could influence the interpenetrating phenomena are also discovered. The technique to extend the current method to three dimensional problems is also outlined. Furthermore, the C++ source code has been implemented to manipulate the complicated complex operations for numerically solving the singular integral equations in complex matrix form.

Li, Renfu

109

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

110

Edge stress intensity functions in 3-D anisotropic composites Zohar Yosibash a,*, Netta Omer a  

E-print Network

or interface cracks between plies lead most frequently to catastrophic failures in cross-ply laminates. Many of these laminates are made of brittle anisotropic materials and occupy three-dimensional (3-D) domains, therefore been provided and the quasi-dual function method was proposed for the extraction of edge stress

Yosibash, Zohar

111

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

112

The factorization method for a defective region in an anisotropic material  

NASA Astrophysics Data System (ADS)

In this paper we consider the inverse acoustic scattering (in {{{R}}3}) or electromagnetic scattering (in {{{R}}2}, for the scalar TE-polarization case) problem of reconstructing possibly multiple defective penetrable regions in a known anisotropic material of compact support. We develop the factorization method for a non-absorbing anisotropic background media containing penetrable defects. In particular, under appropriate assumptions on the anisotropic material properties of the media we develop a rigorous characterization for the support of the defective regions from the given far field measurements. Finally we present some numerical examples in the two-dimensional case to demonstrate the feasibility of our reconstruction method including examples for the case when the defects are voids (i.e. subregions with refractive index the same as the background outside the inhomogeneous hosting media).

Cakoni, Fioralba; Harris, Isaac

2015-02-01

113

Anisotropic friction for deformable surfaces and solids  

Microsoft Academic Search

This paper presents a method for simulating anisotropic friction for deforming surfaces and solids. Frictional contact is a complex phenomenon that fuels research in mechanical engineering, computational contact mechan- ics, composite material design and rigid body dynamics, to name just a few. Many real-world materials have anisotropic surface properties. As an example, most textiles exhibit direction-dependent frictional behavior, but despite

Simon Pabst; Bernhard Thomaszewski; Wolfgang Straßer

2009-01-01

114

The anisotropic diffusion of water in Kevlar-epoxy composites  

Microsoft Academic Search

The diffusion of water into unidirectional Kevlar fibre reinforced epoxy resins was studied as a function of fibre orientation and, for unidirectional (0°) composites, as a function of volume fraction (Vf). As the angle increased from 0 to 90°, the diffusivity increased dramatically; i.e. as more and more fibre-ends were exposed to the shorter diffusion path, the diffusivity increased. The

Marc T. Aronhime; Shoshana Neumann; Gad Marom

1987-01-01

115

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

116

Air Force requirements for NDE of composite materials  

NASA Astrophysics Data System (ADS)

The usage of composite materials has increased and continues to grow in advanced and sophisticated weapon systems. The complexity of structures, and the need for rapid inspection and assessment of systems require further development of existing inspection methods to provide the accuracy and reliability desired. Because of the inherently anisotropic and sometimes nonuniform layered nature of composites, detection and interpretation of defects in operational systems is difficult. Further compounding the inspection problem is the growing requirement to assess the integrity of large structures, and to acquire and interpret large data sets in near real time. This paper examines various aspects of composite development, manufacture, assembly, and inspection issues as they relate to Air Force needs and requirements. Current and future initiatives are detailed and an attempt is made to highlight the inadequacies of current inspection procedures: their reliability and sensitivity to discriminate among various defect states.

Cordell, T. M.; Bhagat, P. K.

117

An anisotropic mechanical fatigue damage evolution model for Pb-free solder materials  

Microsoft Academic Search

Evaluating state of damage in a ductile material as it experiences mechanical fatigue and cyclic loading poses much complexity, and has been the subject of many researches. This study revisits the anisotropic damage model developed by Lemaitre [Lemaitre, J. 1992. A course on damage mechanics. Springer-Verlag Publishing, Berlin] and proposes to use his model combined with two damage models, a

Leila J. Ladani; Jafar Razmi

2009-01-01

118

An anisotropic fibre-matrix material model at finite elastic-plastic strains  

Microsoft Academic Search

In this paper a constitutive model for anisotropic finite strain plasticity, which considers the major effects of the macroscopic behaviour of matrix-fibre materials, is presented. As essential feature matrix and fibres are treated separately, which allows as many bundles of fibres as desired. The free energy function is additively split into a part related to the matrix and in parts

S. Klinkel; C. Sansour; W. Wagner

2005-01-01

119

Space processing of composite materials  

NASA Technical Reports Server (NTRS)

Materials and processes for the testing of aluminum-base fiber and particle composites, and of metal foams under extended-time low-g conditions were investigated. A wetting and dispersion technique was developed, based on the theory that under the absence of a gas phase all solids are wetted by liquids. The process is characterized by a high vacuum environment and a high temperature cycle. Successful wetting and dispersion experiments were carried out with sapphire fibers, whiskers and particles, and with fibers of silicon carbide, pyrolytic graphite and tungsten. The developed process and facilities permit the preparation of a precomposite which serves as sample material for flight experiments. Low-g processing consists then merely in the uniform redistribution of the reinforcements during a melting cycle. For the preparation of metal foams, gas generation by means of a thermally decomposing compound was found most adaptable to flight experiments. For flight experiments, the use of compacted mixture of the component materials limits low-g processing to a simple melt cycle.

Steurer, W. H.; Kaye, S.

1975-01-01

120

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

121

Simulation of ultrasonic array imaging of composite materials with defects.  

PubMed

Ultrasonic transducer arrays are extensively used for the nondestructive evaluation of materials for aerospace and other applications. However, their use with composites requires some technique development because of reflections at the layer boundaries and the effects of attenuation. When used in full matrix capture mode, algorithms such as the total focusing method (TFM) must be applied to obtain the image. In composite materials, improvement to the algorithm is required to include the effects of material anisotropy (affecting wave speed) and optimum aperture limits to optimize the signal-to-noise ratio and location detection for a defect in the material. This paper presents simulations of the ultrasonic array signals in multilayer anisotropic materials with and without a simulated defect. A kernel model for plane wave propagation in the material is combined with an angular spectrum decomposition (for finite transducer elements) and transducer frequency response, to model the full array signals. Inclusion of the defect is through its far-field scattering response. The model facilitates the study of imaging algorithm development by identification of the effects of anisotropy, signal-to-noise ratio, and aperture limit. An analytical method for the calculation of the effective group velocity in the composite at low frequency is demonstrated, permitting rapid calculation of time delay laws in practice. PMID:24658724

Humeida, Yousif; Pinfield, Valerie J; Challis, Richard E; Wilcox, Paul D; Li, Chuan

2013-09-01

122

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

123

Thermal properties of composite materials with a complex fractal structure  

NASA Astrophysics Data System (ADS)

In this work, we report the thermal characterization of platelike composite samples made of polyester resin and magnetite inclusions. By means of photoacoustic spectroscopy and thermal relaxation, the thermal diffusivity, conductivity and volumetric heat capacity of the samples were experimentally measured. The volume fraction of the inclusions was systematically varied in order to study the changes in the effective thermal conductivity of the composites. For some samples, a static magnetic field was applied during the polymerization process, resulting in anisotropic inclusion distributions. Our results show a decrease in the thermal conductivity of some of the anisotropic samples, compared to the isotropic randomly distributed ones. Our analysis indicates that the development of elongated inclusion structures leads to the formation of magnetite and resin domains, causing this effect. We correlate the complexity of the inclusion structure with the observed thermal response through a multifractal and lacunarity analysis. All the experimental data are contrasted with the well known Maxwell-Garnett effective media approximation for composite materials.

Cervantes-Álvarez, F.; Reyes-Salgado, J. J.; Dossetti, V.; Carrillo, J. L.

2014-06-01

124

Delamination growth in composite materials  

NASA Technical Reports Server (NTRS)

The Double Cantilever Beam (DCB) and the End Notched Flexure (ENF) specimens are employed to characterize MODE I and MODE II interlaminar fracture resistance of graphite/epoxy (CYCOM 982) and graphite/PEEK (APC2) composites. Sizing of test specimen geometries to achieve crack growth in the linear elastic regime is presented. Data reduction schemes based upon beam theory are derived for the ENF specimen and include the effects of shear deformation and friction between crack surfaces on compliance, C, and strain energy release rate, G sub II. Finite element (FE) analyses of the ENF geometry including the contact problem with friction are presented to assess the accuracy of beam theory expressions for C and G sub II. Virtual crack closure techniques verify that the ENF specimen is a pure Mode II test. Beam theory expressions are shown to be conservative by 20 to 40 percent for typical unidirectional test specimen geometries. A FE parametric study investigating the influence of delamination length and depth, span, thickness and material properties on G sub II is presented. Mode I and II interlaminar fracture test results are presented. Important experimental parameters are isolated, such as precracking techniques, rate effects, and nonlinear load-deflection response. It is found that subcritical crack growth and inelastic materials behavior, responsible for the observed nonlinearities, are highly rate-dependent phenomena with high rates generally leading to linear elastic response.

Gillespie, J. W., Jr.; Carlsson, L. A.; Pipes, R. B.; Rothschilds, R.; Trethewey, B.; Smiley, A.

1986-01-01

125

Modelling and simulation of electric and magnetic fields in homogeneous non-dispersive anisotropic materials  

Microsoft Academic Search

The paper describes a new efficient method for finding and simulation of electric and magnetic fields in homogeneous non-dispersive electrically anisotropic materials. Electromagnetic wave propagation in these materials is descried by the time-dependent Maxwell’s system which implies initial value problems (IVPs) for electric and magnetic fields. Our method essentially uses matrix symbolic calculations in MATLAB and allows us to compute

V. G. Yakhno; T. M. Yakhno

2007-01-01

126

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

127

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

128

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

129

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

130

Process for producing dispersed particulate composite materials  

DOEpatents

This invention is directed to a process for forming noninterwoven dispersed particulate composite products. In one case a composite multi-layer film product comprises a substantially noninterwoven multi-layer film having a plurality of discrete layers. This noninterwoven film comprises at least one discrete layer of a first material and at least one discrete layer of a second material. In another case the first and second materials are blended together with each other. In either case, the first material comprises a metalloid and the second material a metal compound. At least one component of a first material in one discrete layer undergoes a solid state displacement reaction with at least one component of a second material thereby producing the requisite noninterwoven composite film product. Preferably, the first material comprises silicon, the second material comprises Mo.sub.2 C, the third material comprises SiC and the fourth material comprises MoSi.sub.2.

Henager, Jr., Charles H. (Richland, WA); Hirth, John P. (Viola, ID)

1995-01-01

131

NASA technology utilization survey on composite materials  

NASA Technical Reports Server (NTRS)

NASA and NASA-funded contractor contributions to the field of composite materials are surveyed. Existing and potential non-aerospace applications of the newer composite materials are emphasized. Economic factors for selection of a composite for a particular application are weight savings, performance (high strength, high elastic modulus, low coefficient of expansion, heat resistance, corrosion resistance,), longer service life, and reduced maintenance. Applications for composites in agriculture, chemical and petrochemical industries, construction, consumer goods, machinery, power generation and distribution, transportation, biomedicine, and safety are presented. With the continuing trend toward further cost reductions, composites warrant consideration in a wide range of non-aerospace applications. Composite materials discussed include filamentary reinforced materials, laminates, multiphase alloys, solid multiphase lubricants, and multiphase ceramics. New processes developed to aid in fabrication of composites are given.

Leeds, M. A.; Schwartz, S.; Holm, G. J.; Krainess, A. M.; Wykes, D. M.; Delzell, M. T.; Veazie, W. H., Jr.

1972-01-01

132

Composite structural materials. [fiber reinforced composites for aircraft structures  

NASA Technical Reports Server (NTRS)

Physical properties of fiber reinforced composites; structural concepts and analysis; manufacturing; reliability; and life prediction are subjects of research conducted to determine the long term integrity of composite aircraft structures under conditions pertinent to service use. Progress is reported in (1) characterizing homogeneity in composite materials; (2) developing methods for analyzing composite materials; (3) studying fatigue in composite materials; (4) determining the temperature and moisture effects on the mechanical properties of laminates; (5) numerically analyzing moisture effects; (6) numerically analyzing the micromechanics of composite fracture; (7) constructing the 727 elevator attachment rib; (8) developing the L-1011 engine drag strut (CAPCOMP 2 program); (9) analyzing mechanical joints in composites; (10) developing computer software; and (11) processing science and technology, with emphasis on the sailplane project.

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

1981-01-01

133

Anisotropic deformation of Zr-2.5Nb pressure tube material at high temperatures  

NASA Astrophysics Data System (ADS)

Zr-2.5Nb alloy is used for the pressure tubes in CANDU® reactor fuel channels. In reactor, the pressure tube normally operates at 300 °C and experiences a primary coolant fluid internal pressure of approximately 10 MPa. Manufacturing and processing procedures generate an anisotropic state in the pressure tube which makes the tube stronger in the hoop (transverse) direction than in the axial (longitudinal) direction. This anisotropy condition is present for temperatures less than 500 °C. During postulated accident conditions where the material temperature could reach 1000 °C, it might be assumed that the high temperature and subsequent phase change would reduce the inherent anisotropy, and thus affect the deformation behaviour (ballooning) of the pressure tube. From constant-load, rapid-temperature-ramp, uniaxial deformation tests, the deformation rate in the longitudinal direction of the tube behaves differently than the deformation rate in the transverse direction of the tube. This anisotropic mechanical behaviour appears to persist at temperatures up to 1000 °C. This paper presents the results of high-temperature deformation tests using longitudinal and transverse specimens taken from as-received Zr-2.5Nb pressure tubes. It is shown that the anisotropic deformation behaviour observed at high temperatures is largely due to the stable crystallographic texture of the ?-Zr phase constituent in the material that was previously observed by neutron diffraction measurements during heating at temperatures up to 1050 °C. The deformation behaviour is also influenced by the phase transformation occurring at high temperatures during heating. The effects of texture and phase transformation on the anisotropic deformation of as-received Zr-2.5Nb pressure tube material are discussed in the context of the tube ballooning behaviour. Because of the high temperatures in postulated accident scenarios, any irradiation damage will be annealed from the pressure tube material and thus the unirradiated material results presented in this paper are also applicable to irradiated pressure tubes.

Fong, R. W. L.

2013-09-01

134

Control of the Anisotropic Phase Separation and the Electro-Optical Stability of Ferroelectric Liquid Crystal-Photopolymer Composites  

Microsoft Academic Search

The criteria for controlling the anisotropic phase separation process in ferroelectric liquid crystal (FLC)-photopolymer mixtures are presented. Depending on the FLC composition and the irradiated intensity of the ultraviolet light, one of the polymer-dispersed, anisotropic phase separated (PS), and polymer-network structures is found to be energetically favored to form it from the FLC-photopolymer mixture. In contrast to a surface-stabilized FLC

Jae-Hong Park; Won-Je Lee; Jae-Hoon Kim; Sin-Doo Lee

2003-01-01

135

Anisotropic surface roughness enhances the bending response of ionic polymer-metal composite (IPMC) artificial muscles  

NASA Astrophysics Data System (ADS)

Demands from the fields of bio-medical engineering and biologically-inspired robotics motivate a growing interest in actuators with properties similar to biological muscle, including ionic polymer-metal composites (IPMC), the focus of this study. IPMC actuators consist of an ion-conductive polymer membrane, coated with thin metal electrodes on both sides and bend when voltage is applied. Some of the advantages of IPMC actuators are their softness, lack of moving parts, easy miniaturization, light weight and low actuation voltage. When used in bio-mimetic robotic applications, such as a snake-like swimming robot, locomotion speed can be improved by increasing the bending amplitude. However, it cannot be improved much by increasing the driving voltage, because of water electrolysis. To enhance the bending response of IPMCs we created a "preferred" bending direction by anisotropic surface modification. Introduction of anisotropic roughness with grooves across the length of the actuator improved the bending response by a factor of 2.1. Artificially introduced cracks on the electrodes in direction, in which natural cracks form by bending, improved bending response by a factor of 1.6. Anisotropic surface modification is an effective method to enhance the bending response of IPMC actuators and does not compromise their rigidity under loads perpendicular to the bending plane.

Stoimenov, Boyko L.; Rossiter, Jonathan M.; Mukai, Toshiharu

2007-01-01

136

Analytical Approach to Predict Anisotropic Material Properties from Cup Drawings  

Microsoft Academic Search

Typical beverage can alloys have limited elongation (about 3–5%) under uniaxial tension. However, in order to obtain correct\\u000a material properties, it is recommended to have elongations over 10 percent. Thus, it is very difficult to predict stable r-value\\u000a and stress directionalities experimentally, which are essential for FE simulation of rigid-packing sheet forming operation.\\u000a An innovative simplified analytical approach that relates

J. W. Yoon; R. E. Dick; F. Barlat

2008-01-01

137

Magnetoelectric Interactions in Bi-Anisotropic Media  

Microsoft Academic Search

Classification of bi-anisotropic media based on the structure of magnetoelectric coupling dyadics is proposed. It appears that the most general bi-anisotropic media can be modeled as composites of only a few basic idealized elements: for reciprocal materials, these elements are uniaxial helices and \\

S. A. Tretyakov; A. H. Sihvola; A. A. Sochava; C. R. Simovski

1998-01-01

138

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

139

Clues for biomimetics from natural composite materials  

PubMed Central

Bio-inspired material systems are derived from different living organisms such as plants, arthropods, mammals and marine organisms. These biomaterial systems from nature are always present in the form of composites, with molecular-scale interactions optimized to direct functional features. With interest in replacing synthetic materials with natural materials due to biocompatibility, sustainability and green chemistry issues, it is important to understand the molecular structure and chemistry of the raw component materials to also learn from their natural engineering, interfaces and interactions leading to durable and highly functional material architectures. This review will focus on applications of biomaterials in single material forms, as well as biomimetic composites inspired by natural organizational features. Examples of different natural composite systems will be described, followed by implementation of the principles underlying their composite organization into artificial bio-inspired systems for materials with new functional features for future medicine. PMID:22994958

Lapidot, Shaul; Meirovitch, Sigal; Sharon, Sigal; Heyman, Arnon; Kaplan, David L; Shoseyov, Oded

2013-01-01

140

Precipitate strengthening in nanostructured metallic material composites  

Microsoft Academic Search

Nanostructured metallic material (NMM) composites are a new class of materials that exhibit high structural stability, mechanical strength, high ductility, toughness and resistance to fracture and fatigue; these properties suggest that these materials can play a leading role in the future micromechanical devices. However, before those materials are put into service in any significant applications, many important fundamental issues remain

N. Abdolrahim; I. N. Mastorakos; H. M. Zbib

2012-01-01

141

Artificial anisotropic chiral materials for decrease of reflection of electromagnetic waves from metallic surfaces  

NASA Astrophysics Data System (ADS)

Paying attention to the possibility of making the covers with low reflection of electromagnetic waves we have analyzed the characteristics of the electromagnetic waves under the condition of transmission through the artificial anisotropic medium on the metallic layer. The boundary value problem for normal incidence of electromagnetic waves on stratified periodic structure we have solved in case of the following structure: air- artificial anisotropic medium - layer of metal - air. Amplitude and phase characteristics of reflected and transmitted waves were calculated depending on the parameters of an artificial anisotropic medium and metallic layer, and the complex influence of anisotropic and chiral properties was also investigated. We find the optimum features of the structure required for reducing the intensity of a reflected wave on the certain frequency, here we take into account the absorption of waves in the sample and metal. Aluminum is taken as a metallic substrate. The artificial material is dielectric with the metallic microspirals, inserted in it. The axes of spirals are oriented in the same direction. IN this case the medium is characterized by uniaxial tensors of permittivity and chirality. For the orientation of the axes of spirals in the same direction the Nylon threads can be used, on which the spirals are reeled up. Samples of similar media were recently obtained at Stellenbosch University in Southern Africa. Our calculations allow to predict the experimental results in case of deposition of similar covers on the metallic substrate.

Semchenko, Igor V.; Khakhomov, Sergei A.; Fedosenko, Elena A.

2001-03-01

142

Composite materials and method of making  

SciTech Connect

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

143

Composite, nanostructured, super-hydrophobic material  

DOEpatents

A hydrophobic disordered composite material having a protrusive surface feature includes a recessive phase and a protrusive phase, the recessive phase having a higher susceptibility to a preselected etchant than the protrusive phase, the composite material having an etched surface wherein the protrusive phase protrudes from the surface to form a protrusive surface feature, the protrusive feature being hydrophobic.

D'Urso, Brian R. (Clinton, TN); Simpson, John T. (Clinton, TN)

2007-08-21

144

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

145

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

146

A meshless microscale bone tissue trabecular remodelling analysis considering a new anisotropic bone tissue material law.  

PubMed

In this work, a novel anisotropic material law for the mechanical behaviour of the bone tissue is proposed. This new law, based on experimental data, permits to correlate the bone apparent density with the obtained level of stress. Combined with the proposed material law, a biomechanical model for predicting bone density distribution was developed, based on the assumption that the bone structure is a gradually self-optimising anisotropic biological material that maximises its own structural stiffness. The strain and the stress field required in the iterative remodelling process are obtained by means of an accurate meshless method, the Natural Neighbour Radial Point Interpolation Method (NNRPIM). Comparing with other numerical approaches, the inclusion of the NNRPIM presents numerous advantages such as the high accuracy and the smoother stress and strain field distribution. The natural neighbour concept permits to impose organically the nodal connectivity and facilitates the analysis of convex boundaries and extremely irregular meshes. The viability and efficiency of the model were tested on several trabecular benchmark patch examples. The results show that the pattern of the local bone apparent density distribution and the anisotropic bone behaviour predicted by the model for the microscale analysis are in good agreement with the expected structural architecture and bone apparent density distribution. PMID:22309146

Belinha, Jorge; Jorge, Renato M Natal; Dinis, Lúcia M J S

2013-01-01

147

New topics on nanoindentation of polymers and composite materials  

NASA Astrophysics Data System (ADS)

In this study, nanoindentation was used to determine Young's modulus of homogeneous plastic materials as well as inhomogeneous epoxy woven fabric composites using various indenters. In the first part, homogeneous PMMA and polycarbonate were characterized using conical and spherical indenters. The conventional approach of the inverse analysis was modified in order to account for effects obtained during spherical nanoindentation. The experimental results were verified using FEA analysis in ABAQUS. It was found that viscous effects were present in conical nanoindentations which led to an overestimation of contact stiffness. The second part, the response of carbon and glass fiber woven fabric epoxy composites was investigated using Berkovich and spherical indenters. Localized nanoindentation was performed using the Berkovich probe in both materials which led to determination of glass fibers and matrix stiffnesses. The anisotropic nature of the response was treated modifying the classical approach to calculate transverse modulus of a unidirectional composite. Finally, fiber volume ratios were calculated according to type of composite and indenter used.

Martinez Hernandez, Ricardo

148

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

NASA Technical Reports Server (NTRS)

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. (inventor); Kriz, Ronald D. (inventor); Fitting, Dale W. (inventor)

1993-01-01

149

Machine augmented composite materials for damping purposes  

E-print Network

Matthew McCutcheon, B.S., Arkansas Tech University Co-Chairs of Advisory Committee: Dr. J. N. Reddy Dr. Terry Creasy In this study the energy dissipation performance of machine augmented composite (MAC) materials is investigated. MAC materials... MACHINE AUGMENTED COMPOSITE MATERIALS FOR DAMPING PURPOSES A Thesis by DAVID MATTHEW MCCUTCHEON Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements...

McCutcheon, David Matthew

2005-02-17

150

Continuation of tailored composite structures of ordered staple thermoplastic material  

NASA Technical Reports Server (NTRS)

The search for the cost effective composite structure has motivated the investigation of several approaches to develop composite structure from innovative material forms. Among the promising approaches is the conversion of a planar sheet to components of complex curvature through sheet forming or stretch forming. In both cases, the potential for material stretch in the fiber direction appears to offer a clear advantage in formability over continuous fiber systems. A framework was established which allows the simulation of the anisotropic mechanisms of deformation of long discontinuous fiber laminates wherein the matrix phase is a viscous fluid. Predictions for the effective viscosities of a hyper-anisotropic medium consisting of collimated, discontinuous fibers suspended in viscous matrix were extended to capture the characteristics of typical polymers including non-Newtonian behavior and temperature dependence. In addition, the influence of fiber misorientation was also modeled by compliance averaging to determine ensemble properties for a given orientation distribution. A design tool is presented for predicting the effect of material heterogeneity on the performance of curved composite beams such as those used in aircraft fuselage structures. Material heterogeneity can be induced during manufacturing processes such as sheet forming and stretch forming of thermoplastic composites. This heterogeneity can be introduced in the form of fiber realignment and spreading during the manufacturing process causing radial and tangential gradients in material properties. Two analysis procedures are used to solve the beam problems. The first method uses separate two-dimensional elasticity solutions for the stresses in the flange and web sections of the beam. The separate solutions are coupled by requiring that forces and displacements match section boundaries. The second method uses an approximate Rayleigh-Ritz technique to find the solutions for more complex beams. Analyses are performed for curved beams of various cross-sections loaded in pure bending and with a uniform distributed load. Preliminary results show that the geometry of the beam dictates the effect of heterogeneity on performance. The role of heterogeneity is larger in beams with a small average radius-to-depth ration, R/t, where R is the average radius of the beam and t is the difference between the inside and outside radii. Results of the anlysis are in the form of stresses and displacements and are compared to both mechanics of materials and numerical solutions obtained using finite element analysis.

Santare, Michael H.; Pipes, R. Byron

1992-01-01

151

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

152

Graphene aerogel/epoxy composites with exceptional anisotropic structure and properties.  

PubMed

3D interconnected graphene aerogels (GAs) are prepared through one-step chemical reduction and rational assembly of graphene oxide (GO) sheets, so that the difficulties to uniformly disperse the individual graphene sheets in the polymer matrixes are avoided. Apart from ultralow density, high porosity, high electrical conductivity, and excellent compressibility, the resulting GAs possess a cellular architecture with a high degree of alignment when the graphene content is above a threshold, ?0.5 wt %. The composites prepared by infiltrating GA with epoxy resin present excellent electrical conductivities, together with high mechanical properties and fracture toughness. The unusual anisotropic structure gives rise to ?67% and ?113% higher electrical conductivity and fracture toughness of the composites, respectively, in the alignment direction than that transverse to it. PMID:25691257

Wang, Zhenyu; Shen, Xi; Akbari Garakani, Mohammad; Lin, Xiuyi; Wu, Ying; Liu, Xu; Sun, Xinying; Kim, Jang-Kyo

2015-03-11

153

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

154

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

155

Advanced composite materials for precision segmented reflectors  

NASA Technical Reports Server (NTRS)

The objective in the NASA Precision Segmented Reflector (PSR) project is to develop new composite material concepts for highly stable and durable reflectors with precision surfaces. The project focuses on alternate material concepts such as the development of new low coefficient of thermal expansion resins as matrices for graphite fiber reinforced composites, quartz fiber reinforced epoxies, and graphite reinforced glass. Low residual stress fabrication methods will be developed. When coupon specimens of these new material concepts have demonstrated the required surface accuracies and resistance to thermal distortion and microcracking, reflector panels will be fabricated and tested in simulated space environments. An important part of the program is the analytical modeling of environmental stability of these new composite materials concepts through constitutive equation development, modeling of microdamage in the composite matrix, and prediction of long term stability (including viscoelasticity). These analyses include both closed form and finite element solutions at the micro and macro levels.

Stein, Bland A.; Bowles, David E.

1988-01-01

156

Composite Material Application to Liquid Rocket Engines  

NASA Technical Reports Server (NTRS)

The substitution of reinforced plastic composite (RPC) materials for metal was studied. The major objectives were to: (1) determine the extent to which composite materials can be beneficially used in liquid rocket engines; (2) identify additional technology requirements; and (3) determine those areas which have the greatest potential for return. Weight savings, fabrication costs, performance, life, and maintainability factors were considered. Two baseline designs, representative of Earth to orbit and orbit to orbit engine systems, were selected. Weight savings are found to be possible for selected components with the substitution of materials for metal. Various technology needs are identified before RPC material can be used in rocket engine applications.

Judd, D. C.

1982-01-01

157

NASA Thermographic Inspection of Advanced Composite Materials  

NASA Technical Reports Server (NTRS)

As the use of advanced composite materials continues to increase in the aerospace community, the need for a quantitative, rapid, in situ inspection technology has become a critical concern throughout the industry. In many applications it is necessary to monitor changes in these materials over an extended period of time to determine the effects of various load conditions. Additionally, the detection and characterization of defects such as delaminations, is of great concern. This paper will present the application of infrared thermography to characterize various composite materials and show the advantages of different heat source types. Finally, various analysis methodologies used for quantitative material property characterization will be discussed.

Cramer, K. Elliott

2004-01-01

158

Mechanics of composite materials: Unified micromechanical approach  

SciTech Connect

Although many books have been written on the mechanics of composite materials, only a vew few have been devoted almost exclusively to the micromechanics aspects. The present monograph is devoted primarily to the micromechanics of fiber and particle reinforced composites with some additional treatment of laminates as well. Thus, this book would probably be more suitable as a reference book than a textbook.

Aboundi, J.

1991-12-31

159

Self-healing structural composite materials  

Microsoft Academic Search

A self-healing fiber-reinforced structural polymer matrix composite material is demonstrated. In the composite, a microencapsulated healing agent and a solid chemical catalyst are dispersed within the polymer matrix phase. Healing is triggered by crack propagation through the microcapsules, which then release the healing agent into the crack plane. Subsequent exposure of the healing agent to the chemical catalyst initiates polymerization

M. R. Kessler; N. R. Sottos; S. R. White

2003-01-01

160

Combustion joining of refractory materials: Carboncarbon composites  

E-print Network

Combustion joining of refractory materials: Carbon­carbon composites Jeremiah D.E. White Department­carbon composite is achieved by employing self-sustained, oxygen-free, high-temperature combustion reactions to a used "core" to produce a brake that meets the performance specifications. The combustion-joining (CJ

Mukasyan, Alexander

161

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

162

Composite materials with improved phyllosilicate dispersion  

DOEpatents

The present invention provides phyllosilicates edge modified with anionic surfactants, composite materials made from the edge modified phyllosilicates, and methods for making the same. In various embodiments the phyllosilicates are also surface-modified with hydrophilic lipophilic balance (HLB) modifying agents, polymeric hydrotropes, and antioxidants. The invention also provides blends of edge modified phyllosilicates and semicrystalline waxes. The composite materials are made by dispersing the edge modified phyllosilicates with polymers, particularly polyolefins and elastomers.

Chaiko, David J.

2004-09-14

163

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

164

Composite, ordered material having sharp surface features  

DOEpatents

A composite material having sharp surface features includes a recessive phase and a protrusive phase, the recessive phase having a higher susceptibility to a preselected etchant than the protrusive phase, the composite material having an etched surface wherein the protrusive phase protrudes from the surface to form a sharp surface feature. The sharp surface features can be coated to make the surface super-hydrophobic.

D'Urso, Brian R.; Simpson, John T.

2006-12-19

165

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

166

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 C to form a composite refractory material.

Morrow, M.S.; Holcombe, C.E.

1995-09-26

167

Laser welding of discontinuously reinforced composite materials  

NASA Astrophysics Data System (ADS)

The features of metal composite materials fusion welding are examined and the main defects arising at argon-arc, electron-beam and laser welding of alloys Al-Be-Mg, Fe-Cu-Pb and Al-Pb are revealed. The defects formation mechanisms are indicated and technological welding methods of metal composite materials are developed. These methods allow to prevent defects formation and obtain the welds with required mechanical properties and quality.

Shiganov, I. N.

1999-01-01

168

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

169

Fast, all-optical Rayleigh wave microscope: imaging on isotropic and anisotropic materials.  

PubMed

A fast, non-contact Rayleigh wave scanning microscope is demonstrated, which is capable of scan rates of up to a maximum of 1000 measurements/s with typical speeds of up to 250 measurements/s on real samples. The system uses a mode-locked, Q-switched Nd:YAG laser operating at a mode-locked frequency of 82 MHz and a Q-switch frequency of 1 kHz. The Q-switch frequency determines the upper limit of the scanning rate. The generating laser illumination is delivered and controlled by a computer-generated hologram (CGH). The generating laser produces around 30 pulses at 82 MHz and additional harmonics at 164 and 246 MHz and above. The microscope can operate at these harmonics provided the spatial bandwidth of the optics and the temporal bandwidth of the electronics are suitable. The ultrasound is detected with a specialized knife-edge detector. The microscope has been developed for imaging on isotropic materials. Despite this, the system can be used on anisotropic materials, but imaging and interpreting images can be difficult. The anisotropy and grain structure of the material can distort the Rayleigh wavefront, leading to signal loss. A model has been developed to simulate polycrystalline-anisotropic materials; this is discussed along with possible solutions that would overcome the problems associated with anisotropy. Rayleigh wave amplitude images are demonstrated on silicon nitride at 82 and 164 MHz and on polycrystalline aluminium at 82 MHz. PMID:18238518

Clark, M; Sharples, S D; Somekh, M G

2000-01-01

170

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

171

Determination of aggregate physical properties and its effects on cross-anisotropic behavior of unbound aggregate materials  

E-print Network

in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY August 2004 Major Subject: Civil Engineering DETERMINATION OF AGGREGATE PHYSICAL PROPERTIES AND ITS EFFECT ON CROSS-ANISOTROPIC BEHAVIOR OF UNBOUND AGGREGATE... of Department) August 2004 Major Subject: Civil Engineering iii ABSTRACT Determination of Aggregate Physical Properties and Its Effect on Cross-Anisotropic Behavior of Unbound Aggregate Materials. (August 2004) Sung-Hee Kim, B.S., Inha University...

Kim, Sung-Hee

2005-11-01

172

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

173

Oxygen Compatibility Testing of Composite Materials  

NASA Technical Reports Server (NTRS)

The development of polymer composite liquid oxygen LO2 tanks is a critical step in creating the next generation of launch vehicles. Future launch vehicles need to minimize the gross liftoff weight (GLOW), which is possible due to the 25%-40% reduction in weight that composite materials could provide over current aluminum technology. Although a composite LO2 tank makes these weight savings feasible, composite materials have not historically been viewed as "LO2 compatible." To be considered LO2 compatible, materials must be selected that will resist any type of detrimental, combustible reaction when exposed to usage environments. This is traditionally evaluated using a standard set of tests. However, materials that do not pass the standard tests can be shown to be safe for a particular application. This paper documents the approach and results of a joint NASA/Lockheed Martin program to select and verify LO2 compatible composite materials for liquid oxygen fuel tanks. The test approach developed included tests such as mechanical impact, particle impact, puncture, electrostatic discharge, friction, and pyrotechnic shock. These tests showed that composite liquid oxygen tanks are indeed feasible for future launch vehicles.

Graf, Neil A.; Hudgins, Richard J.; McBain, Michael

2000-01-01

174

Ultrasonic stress wave characterization of composite materials  

NASA Technical Reports Server (NTRS)

The work reported covers three simultaneous projects. The first project was concerned with: (1) establishing the sensitivity of the acousto-ultrasonic method for evaluating subtle forms of damage development in cyclically loaded composite materials, (2) establishing the ability of the acousto-ultrasonic method for detecting initial material imperfections that lead to localized damage growth and final specimen failure, and (3) characteristics of the NBS/Proctor sensor/receiver for acousto-ultrasonic evaluation of laminated composite materials. The second project was concerned with examining the nature of the wave propagation that occurs during acoustic-ultrasonic evaluation of composite laminates and demonstrating the role of Lamb or plate wave modes and their utilization for characterizing composite laminates. The third project was concerned with the replacement of contact-type receiving piezotransducers with noncontacting laser-optical sensors for acousto-ultrasonic signal acquisition.

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

1986-01-01

175

Observation of anisotropic diffusion of light in compacted granular porous materials  

E-print Network

Employing spatially resolved photon time-of-flight spectroscopy, we reveal anisotropic diffusion of light in compressed granular media. Findings correlate well with recent reports of pore structural anisotropy and its pressure dependence, and significantly reshape our understanding of the optics of compacted granular matter. New routes to material characterization and investigations of compression-induced anisotropy are opened, and an urgent need for better understanding of the relation between compression, microstructure and light scattering is disclosed. Important implications for quantitative spectroscopy of powder compacts in general, and pharmaceutical tablets in particular, are also discussed.

Alerstam, Erik

2011-01-01

176

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.

2014-09-01

177

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

178

Electrical conductivity of a two-dimensional model for a structurally anisotropic composite  

NASA Astrophysics Data System (ADS)

The electrical conductivity of a two-dimensional structurally anisotropic model for a composite is considered. The model represents an isotropic matrix with a system of nonconducting inclusions in the form of infinitely thin straight line segments (scratches). The scratches make an angle ? or -? with a preferred axis (for definiteness, axis y) at the same probability, and their centers are chaotically distributed. An approximate effective medium method is used to obtain a general expression for the effective conductivity tensor hat ? _e of this model that is valid over a wide concentration range. In this approximation, both components of tensor are hat ? _e shown to vanish at the same percolation threshold, which is expressed explicitly. The conductivity of the model in a critical region is considered in terms of the similarity hypothesis.

Balagurov, B. Ya.

2010-02-01

179

Failure and fatigue mechanisms in composite materials  

NASA Technical Reports Server (NTRS)

A phenomenological description of microfailure under monotonic and cyclic loading is presented, emphasizing the significance of material inhomogeneity for the analysis. Failure in unnotched unidirectional laminates is reviewed for the cases of tension, compression, shear, transverse normal, and combined loads. The failure of notched composite laminates is then studied, with particular attention paid to the effect of material heterogeneity on load concentration factors in circular holes in such laminates, and a 'materials engineering' shear-lay type model is presented. The fatigue of notched composites is discussed with the application of 'mechanistic wearout' model for determining crack propagation as a function of the number of fatigue cycles.-

Rosen, B. W.; Kulkarni, S. V.; Mclaughlin, P. V., Jr.

1975-01-01

180

Energy absorption of composite material and structure  

NASA Technical Reports Server (NTRS)

Results are presented from a joint research program on helicopter crashworthiness conducted by the U.S. Army Aerostructures Directorate and NASA Langley. Through the ongoing research program an in-depth understanding has been developed on the cause/effect relationships between material and architectural variables and the energy-absorption capability of composite material and structure. Composite materials were found to be efficient energy absorbers. Graphite/epoxy subfloor structures were more efficient energy absorbers than comparable structures fabricated from Kevlar or aluminum. An accurate method of predicting the energy-absorption capability of beams was developed.

Farley, Gary L.

1987-01-01

181

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

182

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

PubMed

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. PMID:24985837

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

2014-06-01

183

Nonlinear optical properties of composite materials  

NASA Technical Reports Server (NTRS)

The optical properties of a new class of composite nonlinear materials composed of coated grains, such as cadmium sulfide with a silver coating, are examined. These materials exhibit intrinsic optical bistability and resonantly enhanced conjugate reflectivity. The threshold for intrinsic optical bistability is low enough for practical applications in optical communications and optical computing. Some problems associated with the fabrication of these materials are addressed. Based on preliminary results, switching times are expected to be in the subpicosecond range.

Haus, Joseph W.; Inguva, Ramarao

1991-01-01

184

Control of the Anisotropic Phase Separation and the Electro-Optical Stability of Ferroelectric Liquid Crystal-Photopolymer Composites  

NASA Astrophysics Data System (ADS)

The criteria for controlling the anisotropic phase separation process in ferroelectric liquid crystal (FLC)-photopolymer mixtures are presented. Depending on the FLC composition and the irradiated intensity of the ultraviolet light, one of the polymer-dispersed, anisotropic phase separated (PS), and polymer-network structures is found to be energetically favored to form it from the FLC-photopolymer mixture. In contrast to a surface-stabilized FLC cell, no broken layers and defects are observed under an external mechanical or a thermal shock exerted on the PSFLC cell and thus the electro-optical stability is obtained.

Park, Jae-Hong; Lee, Won-Je; Kim, Jae-Hoon; Lee, Sin-Doo

2003-10-01

185

Advanced composite materials for optomechanical systems  

NASA Astrophysics Data System (ADS)

Polymer matrix composites (PMCs) have been well established in optomechanical systems for several decades. The other three classes of composites; metal matrix composites (MMCs), ceramic matrix composites (CMCs), and carbon matrix composites (CAMCs) are making significant inroads. The latter include carbon/carbon (C/C) composites (CCCs). The success of composites has resulted in increasing use in consumer, industrial, scientific, and aerospace/defense optomechanical applications. Composites offer significant advantages over traditional materials, including high stiffnesses and strengths, near-zero and tailorable coefficients of thermal expansion (CTEs), tailorable thermal conductivities (from very low to over twice that of copper), and low densities. In addition, they lack beryllium's toxicity problems. Some manufacturing processes allow parts consolidation, reducing machining and joining operations. At present, PMCs are the most widely used composites. Optomechanical applications date from the 1970s. The second High Energy Astrophysical Observatory spacecraft, placed in orbit in 1978, had an ultrahigh-modulus carbon fiber-reinforced epoxy (carbon/epoxy) optical bench metering structure. Since then, fibers and matrix materials have advanced significantly, and use of carbon fiber-reinforced polymers (CFRPs) has increased steadily. Space system examples include the Hubble Space Telescope metering truss and instrument benches, Upper Atmosphere Research Satellite (UARS), James Webb Space Telescope and many others. Use has spread to airborne applications, such as SOFIA. Perhaps the most impressive CFRP applications are the fifty-four 12m and twelve 7m moveable ground-based ALMA antennas. The other three classes of composites have a number of significant advantages over PMCs, including no moisture absorption or outgassing of organic compounds. CCC and CMC components have flown on a variety of spacecraft. MMCs have been used in space, aircraft, military and industrial applications. In this paper, we review key PMC, MMC, CCC, and CMC optomechanical system materials, including properties, advantages, disadvantages, applications and future developments. These topics are covered in more detail in SPIE short courses SC218 and SC1078.

Zweben, Carl

2013-09-01

186

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

187

Describing isotropic and anisotropic out-of-plane deformations in thin cubic materials by use of Zernike polynomials  

SciTech Connect

Isotropic and anisotropic out-of-plane deformations induced by thin-film residual stress on thin cubic materials are studied. By transforming the compliance tensor, an analytical expression can be derived for the biaxial stiffness modulus for all directions in any given cubic crystal plane. A modified Stoney's equation, including both isotropic and anisotropic terms, can be formulated to predict the anisotropic out-of-plane deformation. The isotropic and anisotropic deformations are then described using the Zernike polynomials U21 and U22, respectively. Experimental results from (100) and (110) silicon wafers confirm the model by quantitatively comparing the changes in Z21 and Z22 coefficients due to thin-film stress.

Chang, C.-H.; Akilian, Mireille; Schattenburg, Mark L

2006-01-20

188

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

PubMed

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 cm(2)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 10(5), a field-effect mobility of 205 cm(2)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. PMID:25041752

Xia, Fengnian; Wang, Han; Jia, Yichen

2014-01-01

189

Ceramic Aerogel Composite Materials and Characterization  

NASA Technical Reports Server (NTRS)

Aerogels a.k.a "Solid Smoke" are gels with the liquid phase replaced by gas, leaving behind a highly porous material with a nanoscale framework. Due to the porous, nanoscale structure, aerogels have the lowest known density and conductivity of solids. Aerogels have the potential for being a breakthrough material because of their extremely light weight and unique properties. In this paper, we address overcoming their most profound weaknesses: mechanical fragility and very high surface activity, which leads to a lowered sintering temperature. A matrix of ceramic aerogel composite materials was produced to investigate their properties and functionality. Mechanical property measurements and Scanning Electron Micrographs are used to identify trends and structure of these ceramic composite materials. Thermal cycling was used to identify the sintering points of the materials.

White, Susan; Hrubesh, Lawrence W.; Rasky, Daniel J. (Technical Monitor)

1997-01-01

190

Tensile failure criteria for fiber composite materials  

NASA Technical Reports Server (NTRS)

The analysis provides insight into the failure mechanics of these materials and defines criteria which serve as tools for preliminary design material selection and for material reliability assessment. The model incorporates both dispersed and propagation type failures and includes the influence of material heterogeneity. The important effects of localized matrix damage and post-failure matrix shear stress transfer are included in the treatment. The model is used to evaluate the influence of key parameters on the failure of several commonly used fiber-matrix systems. Analyses of three possible failure modes were developed. These modes are the fiber break propagation mode, the cumulative group fracture mode, and the weakest link mode. Application of the new model to composite material systems has indicated several results which require attention in the development of reliable structural composites. Prominent among these are the size effect and the influence of fiber strength variability.

Rosen, B. W.; Zweben, C. H.

1972-01-01

191

Properties of five toughened matrix composite materials  

NASA Technical Reports Server (NTRS)

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

Cano, Roberto J.; Dow, Marvin B.

1992-01-01

192

Critical evaluation of known bone material properties to realize anisotropic FE-simulation of the proximal femur  

Microsoft Academic Search

Purpose: In a meta-analysis of the literature we evaluated the present knowledge of the material properties of cortical and cancellous bone to answer the question whether the available data are sufficient to realize anisotropic finite element (FE)-models of the proximal femur. Material and method: All studies that met the following criteria were analyzed: Young's modulus, tensile, compressive and torsional strengths,

Dieter Christian Wirtz; Norbert Schiffers; Thomas Pandorf; Klaus Radermacher; Dieter Weichert; Raimund Forst

2000-01-01

193

Strength of anisotropic wood and synthetic materials. [plywood, laminated wood plastics, glass fiber reinforced plastics, polymeric film, and natural wood  

NASA Technical Reports Server (NTRS)

The possibility of using general formulas for determining the strength of different anisotropic materials is considered, and theoretical formulas are applied and confirmed by results of tests on various nonmetallic materials. Data are cited on the strength of wood, plywood, laminated wood plastics, fiber glass-reinforced plastics and directed polymer films.

Ashkenazi, Y. K.

1981-01-01

194

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

195

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

196

Health monitoring method for composite materials  

DOEpatents

An in-situ method for monitoring the health of a composite component utilizes a condition sensor made of electrically conductive particles dispersed in a polymeric matrix. The sensor is bonded or otherwise formed on the matrix surface of the composite material. Age-related shrinkage of the sensor matrix results in a decrease in the resistivity of the condition sensor. Correlation of measured sensor resistivity with data from aged specimens allows indirect determination of mechanical damage and remaining age of the composite component.

Watkins, Jr., Kenneth S. (Dahlonega, GA); Morris, Shelby J. (Hampton, VA)

2011-04-12

197

Hybrid titanium composite material improving composite structure coupling  

Microsoft Academic Search

One method of increasing mechanical joint e-ciency entails the reinforcement of the joining area with thin metal laminates. The suitability and e-ciency of ti- tanium as a reinforcing material was researched and proven at the Institute of Composite Structures and Adaptive Systems of the German Aerospace Cen- ter in Germany (DLR). Experimental results show a signiflcant gain of bearing strength

Axel Fink; Boris Kolesnikov

2005-01-01

198

Thermal expansion properties of composite materials  

NASA Technical Reports Server (NTRS)

Thermal expansion data for several composite materials, including generic epoxy resins, various graphite, boron, and glass fibers, and unidirectional and woven fabric composites in an epoxy matrix, were compiled. A discussion of the design, material, environmental, and fabrication properties affecting thermal expansion behavior is presented. Test methods and their accuracy are discussed. Analytical approaches to predict laminate coefficients of thermal expansion (CTE) based on lamination theory and micromechanics are also included. A discussion is included of methods of tuning a laminate to obtain a near-zero CTE for space applications.

Johnson, R. R.; Kural, M. H.; Mackey, G. B.

1981-01-01

199

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

200

Frictional Ignition Testing of Composite Materials  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

201

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

202

Method of making carbon nanotube composite materials  

DOEpatents

The present invention is a method of making a composite polymeric material by dissolving a vinyl thermoplastic polymer, un-functionalized carbon nanotubes and hydroxylated carbon nanotubes and optionally additives in a solvent to make a solution and removing at least a portion of the solvent after casting onto a substrate to make thin films. The material has enhanced conductivity properties due to the blending of the un-functionalized and hydroxylated carbon nanotubes.

O'Bryan, Gregory; Skinner, Jack L; Vance, Andrew; Yang, Elaine Lai; Zifer, Thomas

2014-05-20

203

Passive vibration damping with magnetostrictive composite material  

NASA Astrophysics Data System (ADS)

This paper describes evaluation of an autonomous-material system tailored for free-layer vibration damping of structural elements. The magnetostrictive particulate composite (MPC) material described has moderate stiffness and minimal temperature and frequency dependence. The composite is created by curing Terfenol particles {Tb (1-x)Dy (x)Fe (2),0.2material is subjected to a constant magnetic field. The cured MPC, under vibratory loading, dissipates energy through hysteresis due to domain-wall motion within the particles. The material has an uncommon combination of stiffness and damping, with modulus near that of fiberglass and loss factor similar to many rubber formulations, and the material exhibits vibration damping capability over wide temperature and frequency ranges. Challenges for design are the material's load-dependent damping capacity and its low ultimate strength. The MPC damping mechanism is predictable, and a finite element modeling approach was validated by test. Material evaluation was performed with direct measurements of modulus and loss factor. Both composite and monolithic Terfenol samples were built and tested. Measurements of the MPC formulations showed loss factors of up to 0.1 are achievable. Off-stoichiometric samples, with higher levels of Terbium (Tb) content compared to the standard Terfenol composition, were found to have even higher damping, with peak damping observed at Tb 0.5. Loss factors approaching 0.3 were measured in monolithic, off-stoichiometric material samples. The damping is load-dependent, moderately dependent on temperature, and relatively insensitive to loading frequency. A prototype flexure with MPC damping, based on the patented SoftRide design used for whole-spacecraft vibration isolation, was built and tested. Damping and stiffness matched predictions with a finite element model of the MPC-damped SoftRide isolator.

Maly, Joseph R.; Carmen, Gregory P.; Goodding, James C.; Kerrigan, Catherine A.; Ho, Ken K.

2007-04-01

204

Composite materials for the extravehicular mobility unit  

NASA Technical Reports Server (NTRS)

The extravehicular mobility unit (EMU), commonly known as the astronaut space suit assembly (SSA) and primary life support system (PLSS), has evolved through the years to incorporate new and innovative materials in order to meet the demands of the space environment. The space shuttle program which is seeing an increasing level of extravehicular activity (EVA), also called space walks, along with interest in an EMU for Lunar-Mars missions means even more demanding conditions are being placed on the suit and PLSS. The project for this NASA-ASEE Summer Program was to investigate new materials for these applications. The focus was to emphasize the use of composite materials for every component of the EMU to enhance the properties while reducing the total weight of the EMU. To accomplish this, development of new materials called fullerene reinforced materials (FRM's) was initiated. Fullerenes are carbon molecules which when added to a material significantly reduce the weight of that material. The Faculty Fellow worked directly on the development of the fullerene reinforced materials. A chamber for fullerene production was designed and assembled and first generation samples were processed. He also supervised with the JSC Colleague, a study of composite materials for the EMU conducted by the student participant in the NASA-ASEE Program, Hector Tello a Rice University graduate student, and by a NASA Aerospace Technologist (Materials Engineer) Evelyne Orndoff, in the Systems Engineering Analysis Office (EC7), also a Rice University graduate student. Hector Tello conducted a study on beryllium and Be alloys and initiated a study of carbon and glass reinforced composites for space applications. Evelyne Orndoff compiled an inventory of the materials on the SSA. Ms. Orndoff also reviewed SSA material requirements and cited aspects of the SSA design where composite materials might be further considered. Hector Tello spent part of his time investigating the solar radiation sensitivity of anodic coatings. This project was directed toward the effects of ultra-violet radiation on high emissivity anodic coatings. The work of both Evelyne Orndoff and Hector Tello is of interest to the Engineering Directorate at NASA/JSC and is also directed toward their research as Rice University graduate students.

Barrera, Enrique V.; Tello, Hector M.

1992-01-01

205

Moisture Absorption and Desorption of Composite Materials  

Microsoft Academic Search

Expressions are presented for the moisture distribution and the mois ture content as a function of time of one dimensional homogeneous and composite materials exposed either on one side or on both sides to humid air or to water. The results apply during both moisture absorption and desorption when the moisture content and the temperature of the environ ment are

Chi-Hung Shen; George S. Springer

1976-01-01

206

http://jtc.sagepub.com Composite Materials  

E-print Network

http://jtc.sagepub.com Composite Materials Journal of Thermoplastic DOI: 10 Thermal and Mechanical Properties of Wood Flour/Talc-filled Polylactic http://jtc.sagepub.com/cgi/content/abstract/21/3/209 The online version of this article can be found at: Published by: http

207

Characterization of self-healing composite materials  

Microsoft Academic Search

Damage occurs in almost every composite material in the form of microcracks that develop in the epoxy matrix that binds the fibers together. Researchers at the University of Illinois Urbana Champaign have recently developed a method to reverse the effects of, or heal, damage in the epoxy matrix. Their in-situ self-healing system uses embedded microcapsules and a catalyst that trigger

Kevin John Ford

2006-01-01

208

EFFECTIVE PROPERTIES OF POROUS AND COMPOSITE MATERIALS  

Microsoft Academic Search

Based on a previously modified version of Bruggerman's method, a dependence of the effective diffusion coefficient in porous media on the porosity is deduced and compared with available experimental data. Based on the same method, a dependency of the effective elastic coefficients of composite materials on the volume fraction of inclusions is deduced in the case of different types of

V. M. Starov; A. G. F. Stapley; V. G. Zhdanov

2004-01-01

209

Crashworthy capability of composite material structures  

Microsoft Academic Search

Considerable research interest has been directed towards the use of composite materials for crashworthiness applications, because they can be designed to provide impact energy absorption capabilities which are superior to those of metals when compared on a weight basis. This review draws together information from a variety of sources to compare the findings of researchers in this field.The anisotropy of

A. G Mamalis; M. Robinson; D. E. Manolakos; G. A. Demosthenous; M. B. Ioannidis; J. Carruthers

1997-01-01

210

Seismic evidence for stratification in composition and anisotropic fabric within the thick lithosphere of Kalahari Craton  

NASA Astrophysics Data System (ADS)

S receiver functions obtained from the data of 97 seismic stations present evidence for the existence of a layered and thick lithosphere beneath the Kalahari Craton. We identified three negative discontinuities within the lithosphere of the Archean cratons and Proterozoic mobile belts of southern Africa. We also employed a novel combination of SRFs and surface-wave analysis to constrain the anisotropic properties of the lithosphere and its internal layering. Our results show that frozen-in anisotropy and compositional changes can generate sharp Mid-Lithospheric Discontinuities (MLD) at depths of 85 and 150-200 km, respectively. We found that a 50 km thick anisotropic layer containing 3% S wave anisotropy and with a fast-velocity axis different from that in the layer beneath can account for the first MLD at about 85 km depth. This depth is largely consistent with that of 8° discontinuity suggested as a global characteristic of cratonic lithosphere. Significant correlation between the depths of an apparent boundary separating the depleted and metasomatic refertilized lithosphere, as inferred from chemical tomography, and those of our second MLD (at 150-200 km depth) led us to characterize this negative discontinuity as a compositional boundary, most likely due to the modification of the cratonic mantle lithosphere by magma infiltration. We detected this MLD at a depth of about 150 km beneath the Zimbabwe Craton and Limpopo belt with a steep deepening to about 200 km underneath the Kaapvaal Craton and its passive margin. The deepening of this boundary is spatially correlated with the surficial expression of the ancient Thabazimbi-Murchison Lineament (TML). This may imply that the translithospheric TML isolates the lithospheric block of the relatively younger Limpopo terrane from that of the ancient Kaapvaal terrane. Finally, the largest velocity contrast (3.6-4.7%) is observed at a boundary located at depths of 260-280 km beneath the Archean domains and the older Proterozoic belt. This boundary may, most likely, represent the LAB, which lies relatively deep beneath the Kaapvaal and Zimbabwe cratons and Limpopo and Kheiss belts (260-280 km). Beneath the younger Proterozoic Namaqua-Natal belt, the LAB shallows to depth of about 200 km. Thus, the Kalahari lithosphere may have survived occurrences of intense magmatism and collisional rifting during the billions of years of its history. However, processes related to the creation of the Kalahari Craton as well as the subsequent alteration of the mantle lithosphere have resulted in an internal layering of its lithosphere.

Sodoudi, F.; Yuan, X.; Kind, R.; Lebedev, S.; Tilmann, F. J.

2013-12-01

211

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.

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

1999-03-01

212

Implementation of an Evolving non Quadratic Anisotropic Behaviour for the Closed Packed Materials  

SciTech Connect

In this paper, the mechanical behaviour of alpha-titanium alloys is modelised for the cold forming processes. The elasto-plastic constitutive law is decomposed in an anisotropic plastic criterion, an isotropic hardening and a kinematic hardening. Non quadratic criteria have been developed by Cazacu et al.[1], to model the plasticity of hexagonal closed packed materials. The implementation of this model in a finite element software switch between two bases, the equilibrium is calculated in a reference basis and the anisotropy axes define a local basis, updated by the deformation gradient. An identification procedure, based on tensile tests, allows defining all the parameters needed to model the elasto-plastic behaviour. Simulations of cold forming processes (bulging and deep drawing) have been done to validate this model. Numerical results are compared with experimental data, obtained from speckles analysis.

Revil-Baudard, Benoit; Massoni, Elisabeth [CEMEF Mines ParisTech, B.P. 207, F-06904 Sophia-Antipolis (France)

2010-06-15

213

Effects of fiber motion on the acoustic behavior of an anisotropic, flexible fibrous material  

NASA Technical Reports Server (NTRS)

The acoustic behavior of a flexible fibrous material was studied experimentally. The material consisted of cylindrically shaped fibers arranged in a batting with the fibers primarily aligned parallel to the face of the batting. This type of material was considered anisotropic, with the acoustic propagation constant depending on whether the dirction of sound propagation was parallel or normal to the fiber arrangement. Normal incidence sound absorption measurements were taken for both fiber orientations over the frequency range 140 to 1500 Hz and with bulk densities ranging from 4.6 to 67 kg/cu m. When the sound propagated in a direction normal to the fiber alignment, the measured sound absorption showed the occurrence of a strong resonance, which increased absorption above that attributed to viscous and thermal effects. When the sound propagated in a direction parallel to the fiber alignment, indications of strong resonances in the data were not present. The resonance in the data for fibers normal to the direction of sound propagation is attributed to fiber motion. An analytical model was developed for the acoustic behavior of the material displaying the same fiber motion characteristics shown in the measurements.

Dahl, Milo D.; Rice, Edward J.; Groesbeck, Donald E.

1987-01-01

214

Conductor-polymer composite electrode materials  

DOEpatents

A conductive composite material useful as an electrode, comprises a conductor and an organic polymer which is reversibly electrochemically dopable to change its electrical conductivity. Said polymer continuously surrounds the conductor in intimate electrical contact therewith and is prepared by electrochemical growth on said conductor or by reaction of its corresponding monomer(s) on said conductor which has been pre-impregnated or pre-coated with an activator for said polymerization. Amount of the conductor is sufficient to render the resultant composite electrically conductive even when the polymer is in an undoped insulating state.

Ginley, D.S.; Kurtz, S.R.; Smyrl, W.H.; Zeigler, J.M.

1984-06-13

215

Mechanical Spectroscopy of Nanostructured Composite Materials  

NASA Astrophysics Data System (ADS)

The thermo-mechanical behavior of different nano-structured composite materials, which were processed within the SAPHIR European Integrated Project, has been characterized by mechanical spectroscopy. The obtained results show clearly that creep resistance of fine grain ceramics such as zirconia can be improved by carbon nano-tube (CNT) reinforcements. On the other hand the elastic modulus and the damping capacity of aluminum matrix composites were increased by SiC nano-particle additions. It has also been observed that CNT additions are responsible for a better thermal stability of polymer such as ABS (Acrylonitrile-Butadiene-Styrene) used in automotive industry.

Mari, Daniele; Schaller, Robert; Mazaheri, Mehdi

2011-07-01

216

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

217

Material properties of anisotropic conductive films (ACFs) and their flip chip assembly reliability in NAND flash memory applications  

Microsoft Academic Search

In this paper, the material properties of anisotropic conductive films (ACFs) and ACF flip chip assembly reliability for a NAND flash memory application were investigated. Measurements were taken on the cur- ing behaviors, the coefficient of thermal expansion (CTE), the modulus, the glass transition temperature (Tg), and the die adhesion strength of six types of ACF. Furthermore, the bonding processes

Kyung-Woon Jang; Chang-Kyu Chung; Woong-Sun Lee; Kyung-Wook Paik

2008-01-01

218

Fracture path in an anisotropic material in the light of a friction experiment. D. Chateau and J.-C. Geminard  

E-print Network

Fracture path in an anisotropic material in the light of a friction experiment. D. Chateau and J is generally used to predict the path of a fracture even if the validity of the principle is difficult. INTRODUCTION Fractures are ubiquitous in everyday life. Examples range, from the harmless, annoying but maybe

Paris-Sud XI, Université de

219

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

220

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

221

Filament-wound composite vessels material technology  

NASA Technical Reports Server (NTRS)

Programs are reviewed that were conducted to establish a technology base for applying advanced fibers or resins to high performance filament-wound pressure vessels for containment of cryogens and high pressure gases. Materials evaluated included boron, graphite, PRD 49-1 and 3/epoxy and S-glass/polyimide composites. Closed-end cylindrical, and oblate spheroid-shaped vessels were fabricated in 4- and 8-inch diameter sizes. Vessels were subjected to single-cycle burst, low-cycle fatigue, and sustained loading tests over a -423 F to room temperature range for epoxy composites and a -423 to 500 F temperature range for the polyimide composites. Vessels tested at cryogenic and/or 500 F had thin (3 to 20 mils) metallic liners whereas vessels tested at room temperature had elastomeric liners. Correlations between acoustic emissions and burst and cyclic properties of PRD 49-1 filament-wound vessels are discussed.

Lark, R. F.

1973-01-01

222

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

223

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

224

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

225

Mechanics Methodology for Textile Preform Composite Materials  

NASA Technical Reports Server (NTRS)

NASA and its contractors have completed a program to develop a basic mechanics underpinning for textile composites. Three major deliverables were produced by the program: 1. A set of test methods for measuring material properties and design allowables; 2. Mechanics models to predict the effects of the fiber preform architecture and constituent properties on engineering moduli, strength, damage resistance, and fatigue life; and 3. An electronic data base of coupon type test data. This report describes these three deliverables.

Poe, Clarence C., Jr.

1996-01-01

226

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

227

Quantitative evaluation of ultrasonic C-scan image in acoustically homogeneous and layered anisotropic materials using three dimensional ray tracing method.  

PubMed

Quantitative evaluation of ultrasonic C-scan images in homogeneous and layered anisotropic austenitic materials is of general importance for understanding the influence of anisotropy on wave fields during ultrasonic non-destructive testing and evaluation of these materials. In this contribution, a three dimensional ray tracing method is presented for evaluating ultrasonic C-scan images quantitatively in general homogeneous and layered anisotropic austenitic materials. The directivity of the ultrasonic ray source in general homogeneous columnar grained anisotropic austenitic steel material (including layback orientation) is obtained in three dimensions based on Lamb's reciprocity theorem. As a prerequisite for ray tracing model, the problem of ultrasonic ray energy reflection and transmission coefficients at an interface between (a) isotropic base material and anisotropic austenitic weld material (including layback orientation), (b) two adjacent anisotropic weld metals and (c) anisotropic weld metal and isotropic base material is solved in three dimensions. The influence of columnar grain orientation and layback orientation on ultrasonic C-scan image is quantitatively analyzed in the context of ultrasonic testing of homogeneous and layered austenitic steel materials. The presented quantitative results provide valuable information during ultrasonic characterization of homogeneous and layered anisotropic austenitic steel materials. PMID:24008174

Kolkoori, Sanjeevareddy; Hoehne, Christian; Prager, Jens; Rethmeier, Michael; Kreutzbruck, Marc

2014-02-01

228

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

229

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

230

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

231

Modeling and characterizing anisotropic inclusion orientation in heterogeneous material via directional cluster functions and stochastic microstructure reconstruction  

SciTech Connect

We present a framework to model and characterize the microstructure of heterogeneous materials with anisotropic inclusions of secondary phases based on the directional correlation functions of the inclusions. Specifically, we have devised an efficient method to incorporate both directional two-point correlation functions S{sub 2} and directional two-point cluster functions C{sub 2} that contain non-trivial topological connectedness information into the simulated annealing microstructure reconstruction procedure. Our framework is applied to model an anisotropic aluminum alloy and the accuracy of the reconstructed structural models is assessed by quantitative comparison with the actual microstructure obtained via x-ray tomography. We show that incorporation of directional clustering information via C{sub 2} significantly improves the accuracy of the reconstruction. In addition, a set of analytical “basis” correlation functions are introduced to approximate the actual S{sub 2} and C{sub 2} of the material. With the proper choice of basis functions, the anisotropic microstructure can be represented by a handful of parameters including the effective linear sizes of the iron-rich and silicon-rich inclusions along three orthogonal directions. This provides a general and efficient means for heterogeneous material modeling that enables one to significantly reduce the data set required to characterize the anisotropic microstructure.

Jiao, Yang, E-mail: yang.jiao.2@asu.edu; Chawla, Nikhilesh [Materials Science and Engineering, Arizona State University, Arizona 85287-6206 (United States)

2014-03-07

232

Spectroscopy of MPS(3):DAMS(+) composite materials  

NASA Astrophysics Data System (ADS)

Composite materials are comprised of two separate components that are brought together to form a new material that exhibits unique properties not found in the individual components. The composite material studied in this work is a guest dye cation, (4-[4-(dimethylamino)-alpha-styrl]-1-methylpyridinium) or DAMS+, intercalated into an inorganic host lattice (MPS 3, where M = Cd2+ or Mn2+). MPS3 :DAMS+ exhibits high-efficiency second-harmonic generation (SHG), which is only observed when a material lacks a center of symmetry. There must be an organization of dye molecules upon intercalation to induce the noncentrosymmetry necessary for SHG. The formation of dye aggregates will be studied as a possible noncentrosymmetric arrangement. The intercalated materials (MPS3:DAMS+) exhibited spectral features of J-aggregates. These features included a sharp aggregate absorption and emission band, known as the J-band. There was a small Stokes shift (250 cm-1) between aggregate absorption and emission bands, and a red-shift between the J-band and isolated dye absorption band (3,700 cm-1). The low-energy tail of the emission J-band was theoretically modeled using the Urbach-Martienssen equation, while the high-energy states were fit to a Gaussian to determine aggregate disorder. Disorder was also modeled using a Monte-Carlo lineshape analysis program. From these theoretical models, the aggregate was found to be two-dimensional and weakly coupled. A variety of sample types were studied including intercalated powders and single crystals using absorbance, reflectance and emission spectroscopy. Reflectance spectra were directly compared with absorbance spectra using the Kramers-Kronig Transformation2 to determine that the surface aggregates and the interior aggregates were structurally similar. A new imaging microspectrophotometer was developed to investigate the topology of the composite materials. Kinetics of the intercalation front were studied and a layer-by-layer intercalation mechanism was developed. Surface studies using other materials indicated the polyanion nature of MPS3 :DAMS+ was essential for aggregation. Infrared microspectroscopy was used to determine the orientation of dye molecules on the surface of the large composite crystals. The DAMS+ in MPS 3:DAMS+ was shown to form two-dimensional brickwork aggregates with the molecules aligned "edge-on" on the surface and interior of the host lattice.

Holt, Jennifer Suzanne

233

Exact solution of the equation of molecular optics for refraction and reflection 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. We derive the propagation characteristics of wave consistent with Maxwell theory and find a new expression of extinction theorem. Using these results we can easily explain the physical origin of total transmission in the external reflection and that of total reflection in internal reflection associated with an anisotropic material. Our results extend the molecular optics to the propagation of electromagnetic wave between two arbitrary anisotropic magnetoelectric materials. And the methods here can be applied to other problems of wave propagation in materials, such as scattering of light.

Shu, W; Luo, H; Ren, Z; Li, Fei; Luo, Hailu; Ren, Zhongzhou; Shu, Weixing

2006-01-01

234

Anisotropic conductive films based on highly aligned polyimide fibers containing hybrid materials of graphene nanoribbons and carbon nanotubes  

NASA Astrophysics Data System (ADS)

Anisotropic electrically conductive films (PI-GNR/CNT) consisting of highly aligned polyimide (PI) composite fibers with graphene nanoribbon (GNR) and carbon nanotube (CNT) (GNR/CNT) hybrids as nanofillers have been prepared by electrospinning. The GNR/CNT hybrids used here were prepared by one-step partial unzipping of multi-walled CNTs, in which, with the residual CNTs bonded on the randomly arranged GNR sheets, not only the aggregation of GNR sheets was greatly prevented but also an electrically conductive pathway with good conductivity was effectively formed with the CNTs acting as linking bridges between different GNRs. Due to the three-dimensional (3D) conductive network structure of the GNR/CNT hybrid and fine dispersion and alignment inside the PI fibers, as well as the good interfacial interaction between the GNR/CNT hybrid and the PI matrix, PI-GNR/CNT composite films exhibit a unique property of anisotropic electrical conductivity of 8.3 × 10-2 S cm-1 in the parallel direction along the fibers and 7.2 × 10-8 S cm-1 in the perpendicular direction, which may open the way for wide potential applications of anisotropic conductive nanomaterials in practical production and scientific research fields.Anisotropic electrically conductive films (PI-GNR/CNT) consisting of highly aligned polyimide (PI) composite fibers with graphene nanoribbon (GNR) and carbon nanotube (CNT) (GNR/CNT) hybrids as nanofillers have been prepared by electrospinning. The GNR/CNT hybrids used here were prepared by one-step partial unzipping of multi-walled CNTs, in which, with the residual CNTs bonded on the randomly arranged GNR sheets, not only the aggregation of GNR sheets was greatly prevented but also an electrically conductive pathway with good conductivity was effectively formed with the CNTs acting as linking bridges between different GNRs. Due to the three-dimensional (3D) conductive network structure of the GNR/CNT hybrid and fine dispersion and alignment inside the PI fibers, as well as the good interfacial interaction between the GNR/CNT hybrid and the PI matrix, PI-GNR/CNT composite films exhibit a unique property of anisotropic electrical conductivity of 8.3 × 10-2 S cm-1 in the parallel direction along the fibers and 7.2 × 10-8 S cm-1 in the perpendicular direction, which may open the way for wide potential applications of anisotropic conductive nanomaterials in practical production and scientific research fields. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06117a

Liu, Mingkai; Du, Yifeng; Miao, Yue-E.; Ding, Qianwei; He, Sixin; Tjiu, Weng Weei; Pan, Jisheng; Liu, Tianxi

2014-12-01

235

Cost minimization through optimized raw material quality composition  

Microsoft Academic Search

Lumber, a heterogeneous, anisotropic material produced from sawing logs, contains a varying number of randomly dispersed, unusable areas (defects) distributed over each boards' surface area. Each board's quality is determined by the frequency and distribution of these defects and the board's dimension. Typically, the industry classifies lumber into five quality classes, ranking board quality in respect to use for the

Urs Buehlmann; R. Edward Thomas; Xiaoqui Zuo

2011-01-01

236

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

2014-11-01

237

The behavior of elastic anisotropic laminated composite flat structures subjected to deterministic and random loadings  

NASA Technical Reports Server (NTRS)

Within this research project, the following topics were studied: (1) foundation of the refined theory of flat cross-ply laminated composite flat and curved panels as well as their static and dynamic response analysis; (2) foundation of a geometrically-nonlinear shear-deformable theory of composite laminated flat panels including the effect of initial geometric imperfections and its application in the postbuckling analysis; (3) the study of the dynamic response of shear deformable elastic laminated composite panels to deterministic time-dependent external excitations as the sonic boom and explosive blast type-loadings; (4) the study of the dynamic response of shear deformable elastic laminated composite panels to random excitation as e.g. the one produced by a jet noise or by any time-dependent external excitation whose characteristics are expressed in a statistical sense; and (5) the dynamic stability of fiber-reinforced composite flat panels whose materials (due to e.g. an ambient high temperature field) exhibit a time-dependent physical behavior.

Librescu, Liviu

1990-01-01

238

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

239

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

240

Nondestructive evaluation of advanced ceramic composite materials  

SciTech Connect

Nondestructive evaluation techniques were developed to characterize performance degrading conditions in continuous fiber-reinforced silicon carbide/silicon carbide composites. Porosity, fiber-matrix interface bond strength, and physical damage were among the conditions studied. The material studied is formed by chemical vapor infiltration (CVI) of the matrix material into a preform of woven reinforcing fibers. Acoustic, ultrasonic, and vibration response techniques were studied. Porosity was investigated because of its inherent presence in the CVI process and of the resultant degradation of material strength. Correlations between porosity and ultrasonic attenuation and velocity were clearly demonstrated. The ability of ultrasonic transmission scanning techniques to map variations in porosity in a single sample was also demonstrated. The fiber-matrix interface bond was studied because of its importance in determining the fracture toughness of the material. Correlations between interface bonding and acoustic and ultrasonic properties were observed. These results are presented along with those obtained form acoustic and vibration response measurements on material samples subjected to mechanical impact damage. This is the final report on research sponsored by the US Department of Energy, Fossil Energy Advanced Research and Technology Development Materials Program. 10 refs., 24 figs., 2 tabs.

Lott, L.A.; Kunerth, D.C.; Walter, J.B.

1991-09-01

241

A numerical thermal model for the cure cycle of an advanced composite material  

SciTech Connect

The cure-cycle temperatures and degree of cure response of an advanced composite material are examined. The governing equations and boundary conditions are transformed from the physical domain to a computational domain. The transformation employs a body fitted coordinate system which facilitates the numerical solution technique. These materials are assumed to be anisotropic. Chemical reactions of the resin during cure produces temperature and hence spatially dependent variations in the generation of energy. In general, the parts which are made from advanced composite materials have complex shapes. These attributes produce problems for the heat transfer analyst. Body-fitted coordinate systems help alleviate these problems by transformation of the complex shape to a simple one. The transformation is accomplished via a system of elliptic partial differential equations. These equations are solved using finite differences and Gaussian elimination.

Kinsey, S.P.

1991-01-01

242

Polymer-composite materials for radiation protection.  

PubMed

Unwanted exposures to high-energy or ionizing radiation can be hazardous to health. Prolonged or accumulated radiation dosage from either particle-emissions such as alpha/beta, proton, electron, neutron emissions, or high-energy electromagnetic waves such as X-rays/? rays, may result in carcinogenesis, cell mutations, organ failure, etc. To avoid occupational hazards from these kinds of exposures, researchers have traditionally used heavy metals or their composites to attenuate the radiation. However, protective gear made of heavy metals are not only cumbersome but also are capable of producing more penetrative secondary radiations which requires additional shielding, increasing the cost and the weight factor. Consequently, significant research efforts have been focused toward designing efficient, lightweight, cost-effective, and flexible shielding materials for protection against radiation encountered in various industries (aerospace, hospitals, and nuclear reactors). In this regard, polymer composites have become attractive candidates for developing materials that can be designed to effectively attenuate photon or particle radiation. In this paper, we review the state-of-the-art of polymer composites reinforced with micro/nanomaterials, for their use as radiation shields. PMID:23009182

Nambiar, Shruti; Yeow, John T W

2012-11-01

243

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

244

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

245

Glasses, ceramics, and composites from lunar materials  

NASA Astrophysics Data System (ADS)

A variety of useful silicate materials can be synthesized from lunar rocks and soils. The simplest to manufacture are glasses and glass-ceramics. Glass fibers can be drawn from a variety of basaltic glasses. Glass articles formed from titania-rich basalts are capable of fine-grained internal crystallization, with resulting strength and abrasion resistance allowing their wide application in construction. Specialty glass-ceramics and fiber-reinforced composites would rely on chemical separation of magnesium silicates and aluminosilicates as well as oxides titania and alumina. Polycrystalline enstatite with induced lamellar twinning has high fracture toughness, while cordierite glass-ceramics combine excellent thermal shock resistance with high flexural strengths. If sapphire or rutile whiskers can be made, composites of even better mechanical properties are envisioned.

Beall, George H.

1992-02-01

246

Ceramic Matrix Composite (CMC) Materials Characterization  

NASA Technical Reports Server (NTRS)

Under the former NASA EPM Program, much initial progress was made in identifying constituent materials and processes for SiC/SiC ceramic composite hot-section components. This presentation discusses the performance benefits of these approaches and elaborates on further constituent and property improvements made under NASA UEET. These include specific treatments at NASA that significantly improve the creep and environmental resistance of the Sylramic(TM) SiC fiber as well as the thermal conductivity and creep resistance of the CVI Sic matrix. Also discussed are recent findings concerning the beneficial effects of certain 2D-fabric architectures and carbon between the BN interphase coating and Sic matrix.

Calomino, Anthony

2001-01-01

247

Ceramic Matrix Composite (CMC) Materials Development  

NASA Technical Reports Server (NTRS)

Under the former NASA EPM Program, much initial progress was made in identifying constituent materials and processes for SiC/SiC ceramic composite hot-section components. This presentation discusses the performance benefits of these approaches and elaborates on further constituent and property improvements made under NASA UEET. These include specific treatments at NASA that significantly improve the creep and environmental resistance of the Sylramic(TM) Sic fiber as well as the thermal conductivity and creep resistance of the CVI Sic matrix. Also discussed are recent findings concerning the beneficial effects of certain 2D-fabric architectures and carbon between the BN interphase coating and Sic matrix.

DiCarlo, James

2001-01-01

248

Electrical conductivity of a two-dimensional model for a composite material with structural anisotropy  

NASA Astrophysics Data System (ADS)

The electrical conductivity of a structurally anisotropic two-dimensional model for a composite material is considered. The model represents an isotropic matrix with a system of nonconducting inclusions in the form of mutually perpendicular scratches of various lengths. The centers of the scratches are chaotically distributed in plane ( x, y). The approximate effective medium method is used to derive an expression for effective conductivity tensor that satisfactorily describes the electrical conductivity of this model over a wide concentration range. The model conductivity in the critical region is considered in terms of the similarity hypothesis.

Balagurov, B. Ya.

2013-08-01

249

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

PubMed Central

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

250

Anisotropic material model and wave propagation simulations for shocked pentaerythritol tetranitrate single crystals  

NASA Astrophysics Data System (ADS)

An anisotropic continuum material model was developed to describe the thermomechanical response of unreacted pentaerythritol tetranitrate (PETN) single crystals to shock wave loading. Using this model, which incorporates nonlinear elasticity and crystal plasticity in a thermodynamically consistent tensor formulation, wave propagation simulations were performed to compare to experimental wave profiles [J. J. Dick and J. P. Ritchie, J. Appl. Phys. 76, 2726 (1994)] for PETN crystals under plate impact loading to 1.2 GPa. Our simulations show that for shock propagation along the [100] orientation where deformation across shear planes is sterically unhindered, a dislocation-based model provides a good match to the wave profile data. For shock propagation along the [110] direction, where deformation across shear planes is sterically hindered, a dislocation-based model cannot account for the observed strain-softening behavior. Instead, a shear cracking model was developed, providing good agreement with the data for [110] and [001] shock orientations. These results show that inelastic deformation due to hindered and unhindered shear in PETN occurs through mechanisms that are physically different. In addition, results for shock propagation normal to the (101) crystal plane suggest that the primary slip system identified from quasistatic indentation tests is not activated under shock wave loading. Overall, results from our continuum simulations are consistent with a previously proposed molecular mechanism for shock-induced chemical reaction in PETN in which the formation of polar conformers, due to hindered shear, facilitates the development of ionic reaction pathways.

Winey, J. M.; Gupta, Y. M.

2010-05-01

251

Anisotropic conductive films based on highly aligned polyimide fibers containing hybrid materials of graphene nanoribbons and carbon nanotubes.  

PubMed

Anisotropic electrically conductive films (PI-GNR/CNT) consisting of highly aligned polyimide (PI) composite fibers with graphene nanoribbon (GNR) and carbon nanotube (CNT) (GNR/CNT) hybrids as nanofillers have been prepared by electrospinning. The GNR/CNT hybrids used here were prepared by one-step partial unzipping of multi-walled CNTs, in which, with the residual CNTs bonded on the randomly arranged GNR sheets, not only the aggregation of GNR sheets was greatly prevented but also an electrically conductive pathway with good conductivity was effectively formed with the CNTs acting as linking bridges between different GNRs. Due to the three-dimensional (3D) conductive network structure of the GNR/CNT hybrid and fine dispersion and alignment inside the PI fibers, as well as the good interfacial interaction between the GNR/CNT hybrid and the PI matrix, PI-GNR/CNT composite films exhibit a unique property of anisotropic electrical conductivity of 8.3 × 10(-2) S cm(-1) in the parallel direction along the fibers and 7.2 × 10(-8) S cm(-1) in the perpendicular direction, which may open the way for wide potential applications of anisotropic conductive nanomaterials in practical production and scientific research fields. PMID:25474256

Liu, Mingkai; Du, Yifeng; Miao, Yue-E; Ding, Qianwei; He, Sixin; Tjiu, Weng Weei; Pan, Jisheng; Liu, Tianxi

2015-01-21

252

Radiation Facilities for Composite Materials Formation  

NASA Astrophysics Data System (ADS)

The radiation facilities on the base of linac for polymer composite materials (PCM) formation was designed. The general technological scheme of PCM production consists in impregnations by synthetic monomers or oligomers of wares made of capillaryporous materials such as wood, qypsum, concrete, ceramic, paper, waste of papermaking, textile and woodworking production which are further treated by relativistic electron or breamsstruhglung beams. The facilities encorporates a linac with scanning electron beams, microwave chamber for drying of materials, a system for vacuum impregnating of materials with synthetic origomers, test bench for irradiations of samples, precise monitoring system for measuring of three-dimentional dose distribution in irradiated samples, and control processing system. The main beam parameters of linac are: electron energy 5--8 MeV; mean beam power up to 5 kW, pulse duration 1--4 mcs; scanning frequency of electromagnetic scanner 1--8 Hz; the irradiation is possible both with electron and with breamsstrahglung beams. The facilities were used for radiation processing investigation and production of new high-strength and corrosian-resistant PCM.

Popov, G. F.; Zalubovsky, I. I.; Avilov, A. M.; Rudychev, V. G.

1997-05-01

253

Dielectric composite materials and method for preparing  

DOEpatents

The invention allows the fabrication of small, dense beads of dielectric materials with selected compositions, which are incorporated into a polymeric matrix for use in capacitors, filters, and the like. A porous, generally spherical bead of hydrous metal oxide containing titanium or zirconium is made by a sol-gel process to form a substantially rigid bead having a generally fine crystallite size and correspondingly finely distributed internal porosity. The resulting gel bead may be washed and hydrothermally reacted with a soluble alkaline earth salt (typically Ba or Sr) at elevated temperature and pressure to convert the bead into a mixed hydrous titanium- or zirconium-alkaline earth oxide while retaining the generally spherical shape. Alternatively, the gel bead may be made by coprecipitation. This mixed oxide bead is then washed, dried and calcined to produce the desired (BaTiO.sub.3, PbTiO.sub.3, SrZrO.sub.3) structure. The sintered beads are incorporated into a selected polymer matrix. The resulting dielectric composite material may be electrically "poled" if desired.

Lauf, Robert J.; Anderson, Kimberly K.; Montgomery, Frederick C.; Collins, Jack L.; Felten, John J.

2003-07-29

254

Method for preparing dielectric composite materials  

DOEpatents

The invention allows the fabrication of small, dense beads of dielectric materials with selected compositions, which are incorporated into a polymeric matrix for use in capacitors, filters, and the like. A porous, generally spherical bead of hydrous metal oxide containing titanium or zirconium is made by a sol-gel process to form a substantially rigid bead having a generally fine crystallite size and correspondingly finely distributed internal porosity. The resulting gel bead may be washed and hydrothermally reacted with a soluble alkaline earth salt (typically Ba or Sr) at elevated temperature and pressure to convert the bead into a mixed hydrous titanium- or zirconium-alkaline earth oxide while retaining the generally spherical shape. Alternatively, the gel bead may be made by coprecipitation. This mixed oxide bead is then washed, dried and calcined to produce the desired (BaTiO.sub.3, PbTiO.sub.3, SrZrO.sub.3) structure. The sintered beads are incorporated into a selected polymer matrix. The resulting dielectric composite material may be electrically "poled" if desired.

Lauf, Robert J.; Anderson, Kimberly K.; Montgomery, Frederick C.; Collins, Jack L.; Felten, John J.

2004-11-23

255

On-top ?-stacking of quasiplanar molecules in hole-transporting materials: inducing anisotropic carrier mobility in amorphous films.  

PubMed

Dimers of partially oxygen-bridged triarylamines were designed and synthesized as hole-transporting materials. X-ray structural analyses revealed that these compounds form on-top ?-stacking aggregates in the crystalline state. TRMC measurements showed that high levels of anisotropic charge transport were induced in the direction of the ?-stacking. Surprisingly, even in vacuum-deposited amorphous films, these compounds retained some of the face-on ?-stacking, thus facilitating an out-of-plane carrier mobility. PMID:24764307

Wakamiya, Atsushi; Nishimura, Hidetaka; Fukushima, Tatsuya; Suzuki, Furitsu; Saeki, Akinori; Seki, Shu; Osaka, Itaru; Sasamori, Takahiro; Murata, Michihisa; Murata, Yasujiro; Kaji, Hironori

2014-06-01

256

Supramolecular assembly of bis(benzimidazole)pyridine: an extended anisotropic ligand for highly birefringent materials.  

PubMed

Four new bis(benzimidazole)pyridine (BBP)-containing compounds Zn(BBP)Cl[Au(CN)2], Mn(BBP)[Au(CN)2]2·H2O, Mn(BBP)Br2(MeOH) and Mn(BBP)Cl2(MeOH)·MeOH have been synthesized and structurally characterized and their birefringence values (?n) determined. The structure of Zn(BBP)Cl[Au(CN)2] contains a hydrogen-bonded dimer of Zn(BBP)Cl[Au(CN)2] units which propagate into a 1D chain through Au-Au interactions, although the crystals are of poor optical quality. The supramolecular structure of Mn(BBP)[Au(CN)2]2·H2 O forms a 1D coordination polymer through chains of Mn(BBP)[Au(CN)2]2 units, each containing one bridging Au(CN)2 and one forming a 2D sheet through Au-Au interactions. The supramolecular structures of Mn(BBP)Br2(MeOH) and Mn(BBP)Cl2(MeOH)·MeOH are very similar, consisting of a complex hydrogen-bonded network between NH imidazole, methanol and halide groups to align BBP building blocks. In the plane of the primary crystal growth direction, the birefringence values of the three Mn-containing materials were ?n=0.08(1), 0.538(3) and 0.69(3), respectively. The latter two birefringence values are larger than in the related 2,2';6'2''-terpyridine systems, placing them among the most birefringent solids reported. These compounds illustrate the utility of extending the ?-system of the building block and incorporating hydrogen-bonding sites as design elements for highly birefringent materials and also illustrates the effect on the measurable birefringence of the crystal quality, growth direction and structural alignment of the anisotropic BBP building blocks. PMID:24281807

Thompson, John R; Ovens, Jeffrey S; Williams, Vance E; Leznoff, Daniel B

2013-12-01

257

Non-destructive evaluation of composite materials with ultrasonic waves generated and detected by lasers.  

PubMed

Measurement of the stiffness properties of composite materials with laser generated and detected ultrasound requires proper understanding of waves emanating from a line or point source in anisotropic and viscoelastic media. The paper briefly presents calculation results of waves radiated by such a source through or at the surface of a composite plate. Dispersion is represented as well as the multiple wave arrivals connected with the folded shape of the quasi-shear ray surface. Moreover, internal diffraction at the cusp edges is properly depicted. An identification method with specific signal processing have been used to measure the stiffness coefficients of composite materials. From group velocity data, the stiffness tensor of materials showing an orthorhombic symmetry can be identified. The stiffness tensor changes induced by elevated temperatures in a composite material were then measured. An alternative approach was developed which allows to measure the phase velocities of waves generated with laser line sources. The material characterisation reliability is then improved. Moreover, the method can be used in practical cases where the front side of the structure only is accessible with the experimental devices. Despite reflection at the rear interface of transient divergent waves which ray surfaces may contain caustics, this inverse problem can be solved in a simple and efficient manner. PMID:12160036

Audoin, B

2002-05-01

258

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

259

High velocity impact resistance of composite materials  

NASA Astrophysics Data System (ADS)

Composite materials are used in applications that require protection against high velocity impacts by fragment simulating projectiles. In this work, the ballistic performance of two commercially available materials against a fragments simulating projectile (FSP) is studied. The materials used were an aramid fiber with a phenolic matrix and a polyethylene fiber with a thermoplastic film. Impact tests have been carried out, with velocities ranging from 300 m/s to 1260m/s. The projectile used is a 1.1g NATO FSP. Impact velocity and exit velocity are measured, to determine the V{50} and the energy absorbed in cases where perforation occurs. Assessment of the impact damaged area is done using ultrasonic C-scan inspection. Types of damage and damage mechanisms have been identified. Several mechanical tests have been carried out to determine the mechanical properties, at different strain rates. Future work in numerical simulation of impact will be done using commercial code AutodyntinycircledR ftom Century Dynamics.

Justo, Jo; Marquer, A. T.

2003-09-01

260

Composition of estuarine colloidal material: organic components  

USGS Publications Warehouse

Colloidal material in the size range 1.2 nm to 0.4 ??m was isolated by ultrafiltration from Chesapeake Bay and Patuxent River waters (U.S.A.). Temperature controlled, stepwise pyrolysis of the freeze-dried material, followed by gas chromatographic-mass spectrometric analyses of the volatile products indicates that the primary organic components of this polymer are carbohydrates and peptides. The major pyrolysis products at the 450??C step are acetic acid, furaldehydes, furoic acid, furanmethanol, diones and lactones characteristic of carbohydrate thermal decomposition. Pyrroles, pyridines, amides and indole (protein derivatives) become more prevalent and dominate the product yield at the 600??C pyrolysis step. Olefins and saturated hydrocarbons, originating from fatty acids, are present only in minor amounts. These results are consistent with the composition of Chesapeake phytoplankton (approximately 50% protein, 30% carbohydrate, 10% lipid and 10% nucleotides by dry weight). The pyrolysis of a cultured phytoplankton and natural particulate samples produced similar oxygen and nitrogencontaining compounds, although the proportions of some components differ relative to the colloidal fraction. There were no lignin derivatives indicative of terrestrial plant detritus in any of these samples. The data suggest that aquatic microorganisms, rather than terrestrial plants, are the dominant source of colloidal organic material in these river and estuarine surface waters. ?? 1982.

Sigleo, A.C.; Hoering, T.C.; Helz, G.R.

1982-01-01

261

Polymer and Composite Materials Used in Hydrogen Service  

E-print Network

1 Polymer and Composite Materials Used in Hydrogen Service MEETING PROCEEDINGS Polymer This report1 describes the results from an information-sharing meeting on the use of polymer and composite knowledge gaps and data needs for using polymers and composite material systems in hydrogen service

262

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

263

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

264

Method of preparing corrosion resistant composite materials  

DOEpatents

Method of manufacture of ceramic materials which require stability in severely-corrosive environment having high alkali-metal activity, high sulfur/sulfide activity and/or molten halides at temperatures of 200.degree.-550.degree. C. or organic salt (including SO.sub.2 and SO.sub.2 Cl.sub.2) at temperatures of 25.degree.-200.degree. C. These surfide ceramics form stoichiometric (single-phase) compounds with sulfides of Ca, Li, Na, K, Al, Mg, Si, Y, La, Ce, Ga, Ba, Zr and Sr and show melting-points that are sufficiently low and have excellent wettability with many metals (Fe, Ni, Mo) to easily form metal/ceramic seals. Ceramic compositions are also formulated to adequately match thermal expansion coefficient of adjacent metal components.

Kaun, Thomas D. (320 Willow St., New Lenox, IL 60451)

1993-01-01

265

Method for preparing 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. 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)

1990-01-01

266

Application of IDT sensors for structural health monitoring of windmill turbine blades made of composite material  

SciTech Connect

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. [University of Dayton Research Institute, 300 College Park, Dayton, OH 45469 (United States); Druffner, C. [Mound Laser and Photonics Center Inc., 965 Capstone Dr, Suite 308 Miamisburg, OH 45432 (United States)

2011-06-23

267

Millimeter-wave imaging of composite materials  

SciTech Connect

This work addresses the application and evaluates the potential of mm-wave imaging in the W-band (75-110 GHz) using samples of low-loss dielectric and composite materials with artificial defects. The initial focus is on the measurement of amplitude changes in the back scattered and forward-scattered fields. The c-scan system employs a focused beam antenna to provide spatial resolution of about one wavelength. A plane-wave model is used to calculate the effective reflection (or transmission) coefficient of multilayer test sample geometry. Theoretical analysis is used to optimize the measurement frequency for higher image contrast and to interpret the experimental results. Both reflection and transmission images, based on back scattered and forward-scattered powers, were made with Plexiglas and Kevlar/epoxy samples containing artificially introduced defects such as subsurface voids and disbonds. The results clearly indicate that mm-wave imaging has high potential for non-contact interrogation of low-loss materials.

Gopalsami, N.; Bakhtiari, S.; Dieckman, S.L.; Raptis, A.C.; Lepper, M.J.

1993-09-01

268

Laminated thermoplastic composite material from recycled high density polyethylene  

NASA Technical Reports Server (NTRS)

The design of a materials-science, educational experiment is presented. The student should understand the fundamentals of polymer processing and mechanical property testing of materials. The ability to use American Society for Testing and Materials (ASTM) standards is also necessary for designing material test specimens and testing procedures. The objectives of the experiment are (1) to understand the concept of laminated composite materials, processing, testing, and quality assurance of thermoplastic composites and (2) to observe an application example of recycled plastics.

Liu, Ping; Waskom, Tommy L.

1994-01-01

269

An in situ grown eutectic magnetoelectric composite material  

Microsoft Academic Search

The phase diagram of the quinary system Fe-Co-Ti-Ba-O contains a region of compositions with the property that unidirectional solidification of liquids with these compositions results in an aligned two phase composite material. One of the phases is a piezomagnetic spinel and the other one a piezoelectric perovskite. The resulting composite is a magnetoelectric material, which can convert magnetic fields into

J. VAN DEN BOOMGAARD; D. R. Terrell; R. A. J. Born; H. F. J. I. Giller

1974-01-01

270

Behaviour of ultrasonic waves in porous rigid materials: an anisotropic Biot-Attenborough model  

NASA Astrophysics Data System (ADS)

The anisotropic pore structure and elasticity of cancellous bone cause wave speeds and attenuation in cancellous bone to vary with angle. Anisotropy has been introduced into Biot theory by using an empirical expression for the angle-and porosity-dependence of tortuosity. Predictions of a modified anisotropic Biot-Attenborough theory are compared with measurements of pulses centred on 100 kHz and 1 MHz transmitted through water-saturated porous samples. The samples are 13 times larger than the original bone samples. Despite the expected effects of scattering, which is neglected in the theory, at 100 kHz the predicted and measured transmitted waveforms are similar.

Aygün, H.; Barlow, C.

2015-01-01

271

Quantum transport in Dirac materials: Signatures of tilted and anisotropic Dirac and Weyl cones  

NASA Astrophysics Data System (ADS)

We calculate conductance and noise for quantum transport at the nodal point for arbitrarily tilted and anisotropic Dirac or Weyl cones. Tilted and anisotropic dispersions are generic in the absence of certain discrete symmetries, such as particle-hole and lattice point group symmetries. Whereas anisotropy affects the conductance g , but leaves the Fano factor F (the ratio of shot noise power and current) unchanged, a tilt affects both g and F . Since F is a universal number in many other situations, this finding is remarkable. We apply our general considerations to specific lattice models of strained graphene and a pyrochlore Weyl semimetal.

Trescher, Maximilian; Sbierski, Björn; Brouwer, Piet W.; Bergholtz, Emil J.

2015-03-01

272

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

273

New silicate bonding technique for composite laser materials  

NASA Astrophysics Data System (ADS)

We report a new low loss silicate bonding method for the assembly of laser materials. Original heterogeneous composite laser crystals have been obtained thanks to this sol-gel method: Er/Yb phosphate glass||sapphire and Nd:YVO 4||sapphire. Sol composition containing additives enables to bond chemically and thermo-mechanically different materials. Composite materials made with KH 2PO 4 rich sol-gel demonstrated the best temperature resistance. Potassium and phosphate ions add extra flexibility and chemical affinity. The bond is resistant to temperatures higher than 200 °C and laser actions have been demonstrated in both composite materials for the first time.

Petit, P. O.; Goldner, P.; Boissière, C.; Sanchez, C.; Viana, B.

2010-08-01

274

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  

SciTech Connect

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, E-mail: hanlor@163.com, E-mail: lsb@nuaa.edu.cn [Key Laboratory of Radar Imaging and Microwave Photonics (Nanjing Univ. Aeronaut. Astronaut.), Ministry of Education, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China) [Key Laboratory of Radar Imaging and Microwave Photonics (Nanjing Univ. Aeronaut. Astronaut.), Ministry of Education, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Nanjing Artillery Academy, Nanjing 211132 (China)] [China; Liu, Shao-Bin, E-mail: hanlor@163.com, E-mail: lsb@nuaa.edu.cn; Tang, Yi-Jun [Key Laboratory of Radar Imaging and Microwave Photonics (Nanjing Univ. Aeronaut. Astronaut.), Ministry of Education, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)] [Key Laboratory of Radar Imaging and Microwave Photonics (Nanjing Univ. Aeronaut. Astronaut.), Ministry of Education, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Zhen, Jian-Ping [Nanjing Artillery Academy, Nanjing 211132 (China)] [Nanjing Artillery Academy, Nanjing 211132 (China)

2014-03-15

275

The isotropic and anisotropic interactions in metal-organic framework materials (MOFs) were investigated by magnetic  

E-print Network

-metal interactions. This may have implications in the field of single-molecular magnets. Unusually Strong Anisotropic investigated by magnetic methods and High-Field Electron Paramagnetic Resonance, respectively. The systems studied were a series of binuclear Cu(II) complexes with bifunctional ligands containing carboxylate and 1

276

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

277

Surface composites: A new class of engineered materials  

SciTech Connect

To integrate irreconcilable material properties into a single component, a new class of engineered materials termed {open_quotes}surface composites{close_quotes} has been developed. In this engineered material, the second phase is spatially distributed in the near surface regions, such that the phase composition is linearly graded as a function of distance from the surface. Surface composites are different from existing engineered materials such as {open_quotes}bulk composites{close_quotes} and {open_quotes}functionally graded materials{close_quotes} (FGM). Unlike bulk composites, the surface phase in surface composites is present only at the near surface regions. In contrast to FGM, the graded properties of surface composites are achieved by unique morphological surface modification of the bulk phase. To fabricate surface composites, the initial surface of the bulk material is transformed using a novel multiple pulse irradiation technique into truncated cone-like structures. The laser induced micro-rough structures (LIMS) possess surface areas which are up to an order of magnitude higher than the original surface. The second phase is deposited on the surface using thin or thick film deposition methods. A key characteristic of surface composites is the formation of a three dimensional, compositionally and thermally graded interface, which gives rise to improved adhesion of the surface phase. Examples of various types of surface composites such as W/Mo, silica/SiC and diamond/steel, etc. are presented in this paper. The unique properties of surface composites make them ideal engineered materials for applications involving adherent thick film coatings of thermally mismatched materials, compositional surface modification for controlled catalytic activity, and creating adherent metal-ceramic and ceramic-polymeric joints. {copyright} {ital 1997 Materials Research Society.}

Singh, R.; Fitz-Gerald, J. [Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States)

1997-03-01

278

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

279

Effect of the porosity on the fracture surface roughness of sintered materials: From anisotropic to isotropic self-affine scaling  

NASA Astrophysics Data System (ADS)

To unravel how the microstructure affects the fracture surface roughness in heterogeneous brittle solids like rocks or ceramics, we characterized the roughness statistics of postmortem fracture surfaces in homemade materials of adjustable microstructure length scale and porosity, obtained by sintering monodisperse polystyrene beads. Beyond the characteristic size of disorder, the roughness profiles are found to exhibit self-affine scaling features evolving with porosity. Starting from a null value and increasing the porosity, we quantitatively modify the self-affine scaling properties from anisotropic (at low porosity) to isotropic (for porosity >10%).

Cambonie, T.; Bares, J.; Hattali, M. L.; Bonamy, D.; Lazarus, V.; Auradou, H.

2015-01-01

280

Effect of the porosity on the fracture surface roughness of sintered materials: from anisotropic to isotropic self-affine scaling.  

PubMed

To unravel how the microstructure affects the fracture surface roughness in heterogeneous brittle solids like rocks or ceramics, we characterized the roughness statistics of postmortem fracture surfaces in homemade materials of adjustable microstructure length scale and porosity, obtained by sintering monodisperse polystyrene beads. Beyond the characteristic size of disorder, the roughness profiles are found to exhibit self-affine scaling features evolving with porosity. Starting from a null value and increasing the porosity, we quantitatively modify the self-affine scaling properties from anisotropic (at low porosity) to isotropic (for porosity >10%). PMID:25679627

Cambonie, T; Bares, J; Hattali, M L; Bonamy, D; Lazarus, V; Auradou, H

2015-01-01

281

Effect of the porosity on the fracture surface roughness of sintered materials: From anisotropic to isotropic self-affine scaling  

E-print Network

To unravel how the microstructure affects the fracture surface roughness in heterogeneous brittle solids like rocks or ceramics, we characterized the roughness statistics of post-mortem fracture surfaces in home-made materials of adjustable microstructure length-scale and porosity, obtained by sintering monodisperse polystyrene beads. Beyond the characteristic size of disorder, the roughness profiles are found to exhibit self-affine scaling features evolving with porosity. Starting from a null value and increasing the porosity, we quantitatively modify the self-affine scaling properties from anisotropic (at low porosity) to isotropic (for porosity larger than 10 %).

Tristan Cambonie; Jonathan Bares; Lamine Hattali; Daniel Bonamy; Véronique Lazarus; Harold Auradou

2015-01-16

282

Improved Damage Resistant Composite Materials Incorporating Shape Memory Alloys  

NASA Technical Reports Server (NTRS)

Metallic shape memory alloys (SMA) such as nitinol have unique shape recovery behavior and mechanical properties associated with a material phase change that have been used in a variety of sensing and actuation applications. Recent studies have shown that integrating nitinol-SMA actuators into composite materials increases the composite material's functionality. Hybrid composites of conventional graphite/epoxy or glass/epoxy and nitinol-SMA elements can perform functions in applications where monolithic composites perform inadequately. One such application is the use of hybrid composites to function both in load bearing and armor capacities. While monolithic composites with high strength-to-weight ratios function efficiently as loadbearing structures, because of their brittle nature, impact loading can cause significant catastrophic damage. Initial composite failure modes such as delamination and matrix cracking dissipate some impact energy, but when stress exceeds the composite's ultimate strength, fiber fracture and material perforation become dominant. One of the few methods that has been developed to reduce material perforation is hybridizing polymer matrix composites with tough kevlar or high modulus polyethynylene plies. The tough fibers increase the impact resistance and the stiffer and stronger graphite fibers carry the majority of the load. Similarly, by adding nitinol-SMA elements that absorb impact energy through the stress-induced martensitic phase transformation, the composites' impact perforation resistance can be greatly enhanced. The results of drop-weight and high velocity gas-gun impact testing of various composite materials will be presented. The results demonstrate that hybridizing composites with nitinol-SMA elements significantly increases perforation resistance compared to other traditional toughening elements. Inspection of the composite specimens at various stages of perforation by optical microscope illustrates the mechanisms by which perforation is initiated. Results suggest that the out-of-plane transverse shear properties of the composite and nitinol elements have a significant effect on the perforation resistance. Applications that can utilize the hybrid composites effectively will also be presented with the experimental studies.

Paine, Jeffrey S. N.; Rogers, Craig A.

1996-01-01

283

Anisotropic hardening model based on non-associated flow rule and combined nonlinear kinematic hardening for sheet materials  

NASA Astrophysics Data System (ADS)

A material model for more effective analysis of plastic deformation of sheet materials is presented in this paper. The model is capable of considering the following aspects of plastic deformation behavior of sheet materials: the anisotropy in yielding stresses in different directions by using a quadratic yield function (based on Hill's 1948 model and stress ratios), the anisotropy in work hardening by introducing non-constant flow stress hardening in different directions, the anisotropy in plastic strains in different directions by using a quadratic plastic potential function and non-associated flow rule (based on Hill's 1948 model and plastic strain ratios, r-values), and finally some of the cyclic hardening phenomena such as Bauschinger's effect and transient behavior for reverse loading by using a coupled nonlinear kinematic hardening (so-called Armstrong-Frederick-Chaboche model). Basic fundamentals of the plasticity of the model are presented in a general framework. Then, the model adjustment procedure is derived for the plasticity formulations. Also, a generic numerical stress integration procedure is developed based on backward-Euler method (so-called multi-stage return mapping algorithm). Different aspects of the model are verified for DP600 steel sheet. Results show that the new model is able to predict the sheet material behavior in both anisotropic hardening and cyclic hardening regimes more accurately. By featuring the above-mentioned facts in the presented constitutive model, it is expected that more accurate results can be obtained by implementing this model in computational simulations of sheet material forming processes. For instance, more precise results of springback prediction of the parts formed from highly anisotropic hardened materials or that of determining the forming limit diagrams is highly expected by using the developed material model.

Taherizadeh, Aboozar; Green, Daniel E.; Yoon, Jeong W.

2013-12-01

284

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

285

ENG 4793: Composite Materials and Processes 1 Injection Molding  

E-print Network

1 ENG 4793: Composite Materials and Processes 1 Injection Molding ver 1 ENG 4793: Composite to inject plastic into mold cavity · Part cools and solidifies ­ next shot is made ENG 4793: Composite mold Injection Part cooling Open and eject part Pack and hold Process time 1 5 15 33 35 ENG 4793

Colton, Jonathan S.

286

Worldwide flight and ground-based exposure of composite materials  

NASA Technical Reports Server (NTRS)

The long-term durability of those advanced composite materials which are applicable to aircraft structures was discussed. The composite components of various military and commercial aircraft and helicopters were reviewed. Both ground exposure and flight service were assessed in terms of their impact upon composite structure durability. The ACEE Program is mentioned briefly.

Dexter, H. B.; Baker, D. J.

1984-01-01

287

Elastoplastic analysis of thermal cycling: layered materials with compositional gradients  

Microsoft Academic Search

Elastopllastic 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,

A. E. Giannakopoulos; S. Suresh; M. Finot; M. Olsson

1995-01-01

288

Microstructural design of composite materials for crashworthy structural applications  

Microsoft Academic Search

Traditionally, metals are used for crashworthy structural applications, mainly due to their plastic deformation characteristics that enable them to absorb impact energy in a controlled manner. Unlike the metals, polymer composite materials display little plastic deformation characteristics. The use of polymer composites for crashworthy structural applications is a major challenge for the composite community. Current research work clearly suggests that

S Ramakrishna

1997-01-01

289

Selected NASA research in composite Materials and structures  

NASA Technical Reports Server (NTRS)

Various aspects of the application of composite materials to aircraft structures are considered. Failure prediction techniques, buckling and postbuckling research, laminate fatigue analysis, damage tolerance, high temperature resin matrix composites and electrical hazards of carbon fiber composites are among the topics discussed.

1980-01-01

290

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

291

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

292

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

293

Dielectric breakdown model for composite materials F. Peruani,1  

E-print Network

Dielectric breakdown model for composite materials F. Peruani,1 G. Solovey,1 I. M. Irurzun,1,2 E. E. The dielectric breakdown model was generalized to describe dielectric breakdown patterns in conductor 30 June 2003 This paper addresses the problem of dielectric breakdown in composite materials

Peruani, Fernando

294

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

295

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

296

An embedded polarimetric sensor for strain monitoring in composite material  

Microsoft Academic Search

Composite materials are being used in increasingly critical applications such as structural members in airplane wings. As demand for these materials pushes design limits, the ability to monitor their internal strain state takes on increasing importance. This paper details one concept for strain monitoring in graphite\\/epoxy composites. In this technique, strain along an embedded optical fiber is monitored by observing

Brian W. Brennan

1986-01-01

297

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

298

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

299

Thermophysical Analysis of High Modulus Composite Materials for Space Vehicles  

Microsoft Academic Search

High modulus composite materials are used extensively in aerospace vehicles mainly for the purpose of increasing strength and reducing weight. However, thermal properties have become essential design information with the use of composite materials in the thermal design of spacecraft and spacecraft electronics packages. This is because the localized heat from closely packed devices can lead to functional failure of

Ho-Sung Lee

2009-01-01

300

Cured composite materials for reactive metal battery electrolytes  

DOEpatents

A solid molecular composite polymer-based electrolyte is made for batteries, wherein silicate compositing produces a electrolytic polymer with a semi-rigid silicate condensate framework, and then mechanical-stabilization by radiation of the outer surface of the composited material is done to form a durable and non-tacky texture on the electrolyte. The preferred ultraviolet radiation produces this desirable outer surface by creating a thin, shallow skin of crosslinked polymer on the composite material. Preferably, a short-duration of low-medium range ultraviolet radiation is used to crosslink the polymers only a short distance into the polymer, so that the properties of the bulk of the polymer and the bulk of the molecular composite material remain unchanged, but the tough and stable skin formed on the outer surface lends durability and processability to the entire composite material product.

Harrup, Mason K.; Stewart, Frederick F.; Peterson, Eric S.

2006-03-07

301

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

302

Environmental effects on composite materials. Volume 3  

SciTech Connect

The present collection of papers, each of which has previously been abstracted in International Aerospace Abstracts, discusses the accelerated environmental testing of composites, moisture solubility and diffusion in epoxy and epoxy-glass composites, the influence of internal and external factors affecting moisture absorption in polymer composites, long-tern moisture absorption in graphite/epoxy angle-ply laminates, the effect of UV light on Kevlar 49-reinforced composites, and temperature and moisture induced deformation in composite sandwich panels. Also discussed are the orthotropic thermoelastic problem of uniform heat flow distributed by a central crack, the effect of microcracks on composite laminate thermal expansion, the stress analysis of wooden structures exposed to elevated temperatures, and the deflection of plastic beams at elevated temperatures.

Springer, G.S.

1988-01-01

303

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

304

Orthotic devices using lightweight composite materials  

NASA Technical Reports Server (NTRS)

Potential applications of high strength, lightweight composite technology in the orthotic field were studied. Several devices were designed and fabricated using graphite-epoxy composite technology. Devices included shoe plates, assistive walker devices, and a Simes prosthesis reinforcement. Several other projects having medical application were investigated and evaluations were made of the potential for use of composite technology. A seat assembly was fabricated using sandwich construction techniques for the Total Wheelchair Project.

Harrison, E., Jr.

1983-01-01

305

The Materials Chemistry of Atomic Oxygen with Applications to Anisotropic Etching of Submicron Structures in Microelectronics and the Surface Chemistry Engineering of Porous Solids  

NASA Technical Reports Server (NTRS)

Neutral atomic oxygen is the most abundant component of the ionospheric plasma in the low Earth orbit environment (LEO; 200 to 700 kilometers altitude) and can produce significant degradation of some spacecraft materials. In order to produce a more complete understanding of the materials chemistry of atomic oxygen, the chemistry and physics of O-atom interactions with materials were determined in three radically different environments: (1) The Space Shuttle cargo bay in low Earth orbit (the EOIM-3 space flight experiment), (2) a high-velocity neutral atom beam system (HVAB) at Los Alamos National Laboratory (LANL), and (3) a microwave-plasma flowing-discharge system at JSC. The Space Shuttle and the high velocity atom beam systems produce atom-surface collision energies ranging from 0.1 to 7 eV (hyperthermal atoms) under high-vacuum conditions, while the flowing discharge system produces a 0.065 eV surface collision energy at a total pressure of 2 Torr. Data obtained in the three different O-atom environments referred to above show that the rate of O-atom reaction with polymeric materials is strongly dependent on atom kinetic energy, obeying a reactive scattering law which suggests that atom kinetic energy is directly available for overcoming activation barriers in the reaction. General relationships between polymer reactivity with O atoms and polymer composition and molecular structure have been determined. In addition, vacuum ultraviolet photochemical effects have been shown to dominate the reaction of O atoms with fluorocarbon polymers. Finally, studies of the materials chemistry of O atoms have produced results which may be of interest to technologists outside the aerospace industry. Atomic oxygen 'spin-off' or 'dual use' technologies in the areas of anisotropic etching in microelectronic materials and device processing, as well as surface chemistry engineering of porous solid materials are described.

Koontz, Steve L.; Leger, Lubert J.; Wu, Corina; Cross, Jon B.; Jurgensen, Charles W.

1994-01-01

306

NASA's Reusable Launch Vehicle Technologies: A Composite Materials Overview  

NASA Technical Reports Server (NTRS)

A materials overview of the NASA's Earth-to-Orbit Space Transportation Program is presented. The topics discussed are: Earth-to-Orbit Goals and Challenges; Space Transportation Program Structure; Generations of Reusable Launch Vehicles; Space Transportation Derived Requirements; X 34 Demonstrator; Fastrac Engine System; Airframe Systems; Propulsion Systems; Cryotank Structures; Advanced Materials, Fabrication, Manufacturing, & Assembly; Hot and Cooled Airframe Structures; Ceramic Matrix Composites; Ultra-High Temp Polymer Matrix Composites; Metal Matrix Composites; and PMC Lines Ducts and Valves.

Clinton, R. G., Jr.; Cook, Steve; Effinger, Mike; Smith, Dennis; Swint, Shayne

1999-01-01

307

Thermoelastic stress analysis techniques for mixed mode fracture and stochastic fatigue of composite materials  

NASA Astrophysics Data System (ADS)

This study develops new quantitative thermoelastic stress analysis (TSA) techniques for fracture and fatigue damage analysis of composite materials. The first part deals with the thermo-mechanical derivation of two quantitative TSA techniques applied to orthotropic composites with and without a transversely-isotropic surface coating layer. The new TSA test procedures are derived in order to relate the thermal infrared (IR) images with the sum of in-plane strains multiplied by two newly defined material constants that can be experimentally pre-calibrated. Experiments are performed to verify the TSA methods with finite element (FE) numerical results along with available anisotropic elasticity solution. The second part of this study applies the quantitative TSA techniques together with the Lekhnitskii's general anisotropic elasticity solution to calculate mixed-mode stress intensity factors (SIFs) in cracked composite materials. The cracked composite coupons are subjected to off-axis loadings with respect to four different material angles in order to generate mixed-mode SIFs. A least-squares method is used to correlate the sum of in-plane strains from the elasticity solution with the measured TSA test results. The mode-I and mode-II SIFs are determined from eccentrically loaded single-edge-notch tension (ESE(T)) composite specimens. The FE models and virtual crack closure technique (VCCT) are utilized for comparisons. In the third part, a new stochastic model is proposed to generate S-N curves accounting for the variability of the fatigue process. This cumulative damage Markov chain model (MCM) requires a limited number of fatigue tests for calibrating the probability transition matrix (PTM) in the Markov chain model and mean fatigue cycles to failure from experiments. In order to construct the MCM stochastic S-N curve, an iterative procedure is required to predict the mean cycles to failure. Fatigue tests are conducted in this study to demonstrate the MCM method. Twenty-one open-hole S2-glass laminates are fatigue-cycled at two different stress levels. The coupon overall stiffness and surface-ply TSA damage area have been used as two damage metrics. The MCM can satisfactorily describe the overall fatigue damage evolution for a limited number of coupons (less than 6) subjected to a given specific stress level. The stochastic S-N curve can be constructed using at least two sets of fatigue tests under different stress levels. Three available fatigue tests for different E-glass laminates from the literature are also investigated using the proposed MCM approach. The results show the MCM method can provide the stochastic S-N curves for different composite systems and a wide range of fatigue cycles.

Wei, Bo-Siou

308

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

309

Study of composites as substrate materials in large space telescopes  

NASA Technical Reports Server (NTRS)

Nonmetallic composites such as the graphite/epoxy system were investigated as possible substrates for the primary mirror of the large space telescope. The possible use of fiber reinforced metal matrix composites was reviewed in the literature. Problems arising out of the use of composites as substrate materials such as grinding, polishing, adherence of reflective coatings, rigidity of substrate, hygrospcopici tendency of the composites, thermal and temporal stability and other related problems were examined.

Sharma, A. V.

1979-01-01

310

Modeling and simulation of manufacturing processes of advanced composite materials  

NASA Astrophysics Data System (ADS)

Models for autoclave curing of thermosetting matrix composites are briefly described along with models of manufacturing process models for thermoplastic matrix composites. These models can be used to obtain optimum cure cycles of composite materials. They are particularly useful since the cure cycle must be modified to account for the effect of internal heat generation at the thickness of composite laminate changes. They can be indispensable tools in finding appropriate rules for optimum cure cycles via expert systems.

Lee, Woo I.; Springer, George S.

311

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

312

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, wherein 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 -C.sub.15 alkylpyridinium halide or mixtures thereof. 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, Judithann Ruth (Columbia, MD)

1998-04-21

313

Hydroxyapatite-calcium carbonate ceramic composite materials  

Microsoft Academic Search

Hydroxyapatite\\/calcium carbonate (CC) composite powders containing up to 50 wt % CO32?, have been prepared via precipitation from aqueous solutions. According to chemical analysis data, the CO32? content of the powders coincides with the intended one over the entire composition range studied. With increasing CO32? content, the specific surface area of the powders decreases because of the formation and growth

M. A. Gol’dberg; V. V. Smirnov; S. V. Kutsev; T. V. Shibaeva; L. I. Shvorneva; N. S. Sergeeva; I. K. Sviridova; S. M. Barinov

2010-01-01

314

Computer modelling of woven composite materials  

Microsoft Academic Search

In this paper the reasons for choosing woven fabric reinforcements for composite components are given and the alternatives to woven structures are examined. The philosophy behind the development of the computer-generated model of a woven composite fabric reinforcement is discussed. The model described here is a general one, capable of producing a 3-D representation of any single layer fabric, and

J. A. Hewitt; D. Brown; R. B. Clarke

1995-01-01

315

Modeling of self-healing composite materials  

Microsoft Academic Search

In this thesis modeling approaches have been considered to describe healing process in self-healing materials. These materials can partially restore their mechanical properties as microcracks develop inside the material. The interest in modeling of self-healing materials comes from recent experiments [1] that show possible perspective applications in many fields of industry. Following the idea of bio-materials that can heal its

Alexander Dementsov

2008-01-01

316

Numerical testing of homogenization formulas efficiency for magnetic composite materials  

NASA Astrophysics Data System (ADS)

Magnetic composite materials are used for multiple applications. The macroscopic behavior of the material is influenced by its microscopic properties. Sometimes it is difficult to model the complex structure of the composite because the properties differ at the microscopic scale. Some simplifying assumptions are often needed, one of them being the homogenization of the material. In this paper two different composite materials were analyzed using a finite element software (COMSOL Multiphysics©). Both materials have a non-magnetic matrix with inclusions made of paramagnetic material for one of them, and ferromagnetic material for the other. The 3D numerical simulations were made for different particle concentrations and for different applied fields. The homogenization was implemented using two different formulas: Maxwell Garnett and Bruggeman. Numerical comparison was made between the magnetic properties of non-homogeneous materials and homogeneous ones showing each formula's efficiency for different cases.

Bordianu, Adelina; Petrescu, Lucian; Ionita, Valentin

2015-02-01

317

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

318

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

2015-04-01

319

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

320

Extremely anisotropic boundary conditions and their optical applications  

Microsoft Academic Search

We discuss here the design of artificial nanoparticles, surfaces and composite materials that may realize extremely anisotropic boundary conditions, with values not easily attainable in natural optical materials. We apply the closed-form analytical solution available in the case of an individual nanosphere composed of two conjoined hemispheres with opposite permittivity in order to show that it may be possible to

Andrea Alù; Nader Engheta

2010-01-01

321

Composite material application for liquid rocket engines  

NASA Technical Reports Server (NTRS)

With increasing emphasis on improving engine thrust-to-weight ratios to provide improved payload capabilities, weight reductions achievable by the use of composites have become attractive. Of primary significance is the weight reduction offered by composites, although high temperature properties and cost reduction were also considered. The potential for application of composites to components of Earth-to-orbit hydrocarbon engines and orbit-to-orbit LOX/H2 engines was assessed. The components most likely to benefit from the application of composites were identified, as were the critical technology areas where developed would be required. Recommendations were made and a program outlined for the design, fabrication, and demonstration of specific engine components.

Heubner, S. W.

1982-01-01

322

Formation of Lanxide ceramic composite materials  

Microsoft Academic Search

A process for the production of ceramic\\/metal composites is described which involves rapid outward growth of an oxidation reaction product from the surface of a molten metal in contact with a gaseous oxidant. The process is illustrated with the example of the formation of AlâOâ\\/Al composites from Al, and Mg and one or more of the Group IV elements Si,

M. S. Newkirk; A. W. Urquhart; H. R. Zwicker; E. Breval

1986-01-01

323

Modeling of physical properties of composite materials  

Microsoft Academic Search

Recent progress in three different areas involving the modeling of the physical properties of composites is reviewed. These include: (i) theoretical approaches to microstructure\\/property relations; (ii) X-ray microtomography, an imaging technique that enables one to obtain high-resolution three-dimensional microstructural phase information of a composite sample in a non-intrusive manner; and (ii) topology optimization, a promising numerical technique that enables one

S. Torquato

2000-01-01

324

Unfolding of plasmon-polariton modes in one-dimensional layered systems containing anisotropic left-handed materials  

NASA Astrophysics Data System (ADS)

The propagation of electromagnetic waves through a 1-dimensional layered system containing alternate layers of air and a uniaxial, anisotropic, left-handed material is investigated. The optical axis of this material is along the stacking direction and the components of the electric permittivity and magnetic permeability tensors that characterize the metamaterial are described by Drude-type responses. Different plasmon frequencies are considered for directions parallel and perpendicular to the optical axis. As in the isotropic case, plasmon polariton modes are found in the neighborhood of the plasmon frequency corresponding to the optical axis. Moreover, it is shown that, depending on the relation between the two plasmon frequencies of the metamaterial, anisotropy leads to the unfolding of an infinite number of nearly dispersionless plasmon-polariton bands either above or below the parallel plasmon frequency.

Bruno-Alfonso, A.; Reyes-Gómez, E.; Cavalcanti, S. B.; Oliveira, L. E.

2011-09-01

325

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

326

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

327

Preparation of composite materials in space. Volume 1: Executive summary  

NASA Technical Reports Server (NTRS)

The reported objectives were to define promising materials, to obtain significant processing criteria and the related processing techniques and apparatus for the preparation of composites in space, and to establish a program for zero-g experiments and the required developmental efforts. Preparation was studied of the following composite types: (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. The zero-g environment of orbital operations offers the capability to produce metal-base composite materials and castings which exhibit properties and, particularly, unique combinations of properties that cannot be achieved in terrestrial production.

Steurer, W. H.; Kaye, S.

1973-01-01

328

Co-continuous composite materials for friction and braking applications  

NASA Astrophysics Data System (ADS)

Reactive infiltration of precursor ceramics (e.g., the formation of an alumina-aluminum composite by reaction of silica in liquid aluminum) is a low-cost and versatile method of creating materials with interpenetrating co-continuous ceramic and metal phases. By controlling the composition and microstructure of the precursor and the composition of the reaction bath, one can control the structure and properties of the resulting material. This paper summarizes preliminary attempts to use these routes to create next-generation materials for automotive brake rotors. Two types of materials were tested. The first is a two-level composite of a co-continuous alumina-aluminum structure that surrounds SiC particles that provide thermal conductivity. For higher-temperature use, the aluminum alloy is replaced with aluminum-bronze. Both materials show friction and wear properties similar to cast iron, but with half the density and better thermal conductivity.

Daehn, Glenn S.; Breslin, Michael C.

2006-11-01

329

Production of composites by using gliadin as a bonding material  

Technology Transfer Automated Retrieval System (TEKTRAN)

In our previous papers, a new technology that produces biopolymer composites by particle-bonding was introduced. During the manufacturing process, micrometer-scale raw material was coated with a corn protein, zein, which is then processed to form a rigid material. The coating of raw-material particl...

330

Nonmetallic materials and composites at low temperatures 3  

Microsoft Academic Search

Developments in theoretical and experimental research into the use of nonmetallic materials in low temperature applications are surveyed. Studies of the thermal expansion properties of nonmetallic materials and the thermal conductivity of polymers below 1 K are reported. A method is presented for the fracture toughness of composite materials exposed to impact loading and a mini-cryostat is described for high-velocity

G. Hartwig; D. Evans

1986-01-01

331

Magnetoelectric Effect in Composites of Magnetostrictive and Piezoelectric Materials  

Microsoft Academic Search

In the past few decades, extensive research has been conducted on the magnetoelectric (ME) effect in single phase and composite materials. Dielectric polarization of a material under a magnetic field or an induced magnetization under an electric field requires the simultaneous presence of long-range ordering of magnetic moments and electric dipoles. Single phase materials suffer from the drawback that the

JUNGHO RYU; SHASHANK PRIYA; KENJI UCHINO; HYOUN-EE KIM

2002-01-01

332

LIGHTNING EFFECTS IN AIRCRAFT OF THE COMPOSITE MATERIAL  

Microsoft Academic Search

While a gradual increase is looked for in the use of composite material (CFC, Fiberglass, etc.) in aircraft, aiming to a significant reduction in weight, the use of this material cause a decrease in the protection against the adverse effects generate by lightning (high intensity atmospheric discharge), for treating of a bad conductive electric current material. The lightning current when

S. A. Baldacim; N. Cristofani; J. L. F. Junior; J. R. Lautenschlager

333

POLYDIMETHYLSILOXANE-BASED SELF-HEALING COMPOSITE AND COATING MATERIALS  

E-print Network

POLYDIMETHYLSILOXANE-BASED SELF-HEALING COMPOSITE AND COATING MATERIALS BY SOO HYOUN CHO B and bulk materials. The new self-healing system we developed greatly extends the capability of self-healing. This self-healing coating solution can be easily applied to most substrate materials, and is compatible

Braun, Paul

334

Networks of channels for self-healing composite materials  

Microsoft Academic Search

This is a fundamental study of how to vascularize a self-healing composite material so that healing fluid reaches all the crack sites that may occur randomly through the material. The network of channels is built into the material and is filled with pressurized healing fluid. When a crack forms, the pressure drops at the crack site and fluid flows from

A. Bejan; S. Lorente; K.-M. Wang

2006-01-01

335

Characterization and performance of a self-healing composite material  

Microsoft Academic Search

The development of a self-healing polymer-matrix composite material that possesses the ability to heal cracks autonomically is described. The system uses a monomer repair agent, dicyclopentadiene (DCPD), which is stored in an epoxy matrix by dispersing microcapsules containing the liquid repair agent throughout the matrix. When the material is damaged, cracks propagate through the material and break open the microcapsules,

Michael Richard Kessler

2002-01-01

336

Optimisation of a multiphase intermetallic metal metal composite material  

E-print Network

Optimisation of a multiphase intermetallic metal ± metal composite material J. D. Robson, N; accepted 7 August 2000. # 2001 IoM Communications Ltd. Introduction Single phase intermetallic materials strength. Many efforts have therefore focused on the development of multiphase intermetallic materials

Cambridge, University of

337

Mechanical performance of woodfibre–waste plastic composite materials  

Microsoft Academic Search

Plastic products used for packaging are often discarded after a single use resulting in an inexhaustible supply of waste polymeric materials. The stiffness and strength of polymeric materials have been known to improve with the addition of lignocellulosic fibres available in abundance in nature. Hence, composite materials containing natural fibres and waste plastics would result in the reduction of solid

Krishnan Jayaraman; Debes Bhattacharyya

2004-01-01

338

Microthermodynamics analysis of the shape memory effect in composite materials  

SciTech Connect

The shape memory effect and pseudoelasticity due to phase transformation in shape memory alloy (SMA) composites is modeled using a two part procedure. First, phenomenological constitutive equations are proposed for the monolithic polycrystalline SMA material. The equations are of the generalized standard material type, in which the response is given by a convex free energy function and a dissipation potential. Second, a micromechanics analysis of a SMA composite material is performed to derive its free energy, transformation strain rate, and Clausius-Clapeyron equation. Specific results are given for a Nitinol SMA fiber/elastomer matrix composite.

Boyd, J.G.; Lagoudas, D.C. [Texas A and M Univ., College Station, TX (United States)

1994-12-31

339

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

340

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

341

Size-dependent Eshelby tensor fields and effective conductivity of composites made of anisotropic phases with highly conducting imperfect interfaces  

NASA Astrophysics Data System (ADS)

In this work, Eshelby’s results and formalism for an elastic inhomogeneity embedded in an elastic infinite matrix are extended to the thermal-conduction phenomenon in composites consisting of anisotropic phases with highly conducting imperfect interfaces. The generalized Eshelby’s interior and exterior conduction tensor fields and localization tensor fields in the important cases of circular and spherical inhomogeneities are obtained in an explicit analytical way. Quite different from the relevant results of elasticity, the generalized Eshelby’s conduction tensor field and localization tensor field inside circular and spherical inhomogeneities are shown to remain uniform even in the presence of highly conducting imperfect interface. With the help of the obtained expressions for Eshelby’s tensor fields and localization tensor fields, the size-dependent overall thermal-conduction properties of composites are estimated by using the dilute, Mori-Tanaka, self-consistent, and generalized self-consistent models. The analytical results are finally compared with numerical results delivered by the finite element method. The approach elaborated and results provided by the present work are directly applicable to other physically analogous transport phenomena, such as electric conduction, dielectrics, magnetism, diffusion, and flow in porous media and to the mathematically identical phenomenon of antiplane elasticity.

Le-Quang, H.; Bonnet, G.; He, Q.-C.

2010-02-01

342

Optical responses of planar composites consisting of monolayer graphene sheets and axially helicoidal (bi)anisotropic films  

NASA Astrophysics Data System (ADS)

Optical responses of planar composites made of monolayer graphene sheets and axially helicoidal (bi)anisotropic films (HBFs) are studied using our developed algorithm based on spectral-domain exponential matrix (SDEM) technique. Such HBF-based structures possessing z-axis inhomogeneity, in particular, include locally uniaxial chiral nematic and biaxially smectic liquid crystals (CNLC and CSLC) with double or a few layered graphene sheets inserted. In our mathematical treatment, they are artificially divided into many very thin sub-layers, where each one can be described by a set of z-coordinate independent constitutive tensors. The effects of wavelength and angle of the incident light, chemical potential of monolayer graphene, period of the z-axis inhomogeneity and angle of rise of the composites on their reflectance and transmittance are investigated numerically for different constitutive features and geometries. It is shown that the first- and second-order Bragg reflection or transmission zones at optical bands do exist in the presence of double or a few layered dispersive graphene sheets with slight loss but more freedom introduced.

Gu, Xiao-Qiang; Wang, Si-Yi; Yin, Wen-Yan

2014-02-01

343

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

344

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

345

Stress concentration around circular hole in a composite material specimen representative of the X-29A forward-swept wing aircraft  

NASA Technical Reports Server (NTRS)

The theory of anisotropic elasticity was used to evaluate the anisotropic stress concentration factors of a composite laminated plate containing a small circular hole. This advanced composite material was used to manufacture the X-29A forward swept wing. Observe that the usual isotropic material stress concentration factor is three. However, for composite material, it was found that the anisotropic stress concentration factor is no longer constant, and that the locations of maximum tangential stress points could shift by changing the fiber orientation with respect to the loading axis. The analysis showed that through the lamination process, the stress concentration factor could be drastically reduced, and therefore the structural performance could be improved. Both the mixture rule approach and the constant strain approach were used to calculate the stress concentration factor. The results predicted by the mixture rule approach were about 20 percent deviate from the experimental data. However, the results predicted by the constant strain approach matched the testing data very well. This showed the importance of the inplane shear effect on the evaluation of stress concentration factor for the X-29A composite plate.

Yeh, Hsien-Yang

1988-01-01

346

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

347

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. 11 figs.

Webb, B.J.; Antoniak, Z.I.; Prater, J.T.; DeSteese, J.G.

1992-03-24

348

Micromechanical models for graded composite materials  

Microsoft Academic Search

Elastic response of selected plane-array models of graded composite microstructures is examined under both uniform and linearly varying boundary tractions and displacements, by means of detailed finite element studies of large domains containing up to several thousand inclusions. Models consisting of piecewise homogeneous layers with equivalent elastic properties estimated by Mori-Tanaka and selfconsistent methods are also analysed under similar boundary

Viggo Tvergaard

1997-01-01

349

Filament-wound composite vessel materials technology  

NASA Technical Reports Server (NTRS)

Review of recent developments in advanced filament-wound fiber/resin composite vessel technology for cryogen and high-pressure gas containment applications. Design and fabrication procedures have been developed for small-diameter closed-end vessels equipped with thin elastomeric or thin metallic liners. Specific results are discussed.

Lark, R. F.

1973-01-01

350

New understanding of fiber composite materials  

NASA Technical Reports Server (NTRS)

Statistical bounding approach to study of filamentary composites provides understanding of their fracture mechanics. Comparison shows that bounds are in good agreement with data from several fiber-matrix systems, and that they can be used to interpret strength data and provide fracture behavior information leading to improved strength.

Zweben, C.

1971-01-01

351

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

352

Composite Materials for Thermal Energy Storage: Enhancing Performance through Microstructures  

PubMed Central

Chemical incompatibility and low thermal conductivity issues of molten-salt-based thermal energy storage materials can be addressed by using microstructured composites. Using a eutectic mixture of lithium and sodium carbonates as molten salt, magnesium oxide as supporting material, and graphite as thermal conductivity enhancer, the microstructural development, chemical compatibility, thermal stability, thermal conductivity, and thermal energy storage performance of composite materials are investigated. The ceramic supporting material is essential for preventing salt leakage and hence provides a solution to the chemical incompatibility issue. The use of graphite gives a significant enhancement on the thermal conductivity of the composite. Analyses suggest that the experimentally observed microstructural development of the composite is associated with the wettability of the salt on the ceramic substrate and that on the thermal conduction enhancer. PMID:24591286

Ge, Zhiwei; Ye, Feng; Ding, Yulong

2014-01-01

353

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

354

Composite materials with self-contained wireless sensing networks  

NASA Astrophysics Data System (ADS)

The increasing demand for in-service structural health monitoring, particularly in the aircraft industry, has stimulated efforts to integrate self sensing capabilities into materials and structures. This work presents efforts to develop structural composite materials which include networks of sensors with decision-making capabilities that extend the functionality of the composite materials to be information-aware. Composite panels are outfitted with networks of self-contained wireless sensor modules which can detect damage in composite materials via active nondestructive testing techniques. The wireless sensor modules will communicate with one another and with a central processing unit to convey the sensor data while also maintaining robustness and the ability to self-reconfigure in the event that a module fails. Ultimately, this research seeks to create an idealized network that is compact in size, cost efficient, and optimized for low power consumption while providing a sufficient data transfer rate to a local host.

Schaaf, Kristin; Kim, Robert; Nemat-Nasser, Sia

2010-04-01

355

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

356

Microstructural Characterization of Material Properties and Damage in Asphalt Composites  

E-print Network

composite material and X-ray Computed Tomography nondestructive imaging of damage in the microstructure. These experimental measurements were performed on specimens that are first damaged in the Dynamic Mechanical Analyzer (DMA). The DMA is a tool commonly...

Mohammad Khorasani, Sara

2013-05-03

357

Composite materials for thermal energy storage: enhancing performance through microstructures.  

PubMed

Chemical incompatibility and low thermal conductivity issues of molten-salt-based thermal energy storage materials can be addressed by using microstructured composites. Using a eutectic mixture of lithium and sodium carbonates as molten salt, magnesium oxide as supporting material, and graphite as thermal conductivity enhancer, the microstructural development, chemical compatibility, thermal stability, thermal conductivity, and thermal energy storage performance of composite materials are investigated. The ceramic supporting material is essential for preventing salt leakage and hence provides a solution to the chemical incompatibility issue. The use of graphite gives a significant enhancement on the thermal conductivity of the composite. Analyses suggest that the experimentally observed microstructural development of the composite is associated with the wettability of the salt on the ceramic substrate and that on the thermal conduction enhancer. PMID:24591286

Ge, Zhiwei; Ye, Feng; Ding, Yulong

2014-05-01

358

Data-driven imaging in anisotropic media  

SciTech Connect

Anisotropic materials are being used increasingly in high performance industrial applications, particularly in the aeronautical and nuclear industries. Some important examples of these materials are composites, single-crystal and heavy-grained metals. Ultrasonic array imaging in these materials requires exact knowledge of the anisotropic material properties. Without this information, the images can be adversely affected, causing a reduction in defect detection and characterization performance. The imaging operation can be formulated in two consecutive and reciprocal focusing steps, i.e., focusing the sources and then focusing the receivers. Applying just one of these focusing steps yields an interesting intermediate domain. The resulting common focus point gather (CFP-gather) can be interpreted to determine the propagation operator. After focusing the sources, the observed travel-time in the CFP-gather describes the propagation from the focus point to the receivers. If the correct propagation operator is used, the measured travel-times should be the same as the time-reversed focusing operator due to reciprocity. This makes it possible to iteratively update the focusing operator using the data only and allows the material to be imaged without explicit knowledge of the anisotropic material parameters. Furthermore, the determined propagation operator can also be used to invert for the anisotropic medium parameters. This paper details the proposed technique and demonstrates its use on simulated array data from a specimen of Inconel single-crystal alloy commonly used in the aeronautical and nuclear industries.

Volker, Arno; Hunter, Alan [TNO Stieltjes weg 1, 2600 AD, Delft (Netherlands)

2012-05-17

359

CCMR: “ Green ” Composites: An alternative to petroleum-based materials  

NSDL National Science Digital Library

Composites made from natural fibers and resins offer a potential alternative to the petroleum-based materials that are currently used in in many applications such as packaging. These composites have the advantage of being biodegradable, renewable and environmentally friendly. In this work, different additives, including glycerol and polycarboxylic acid (PCA), are introduced to these composites in an attempt to increase properties such as strength and flexibility.

Cooley, LaDean M.

2007-08-29

360

Low-Cost Composite Materials and Structures for Aircraft Applications  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

361

Three-dimensional electromagnetic modeling of composite dielectric materials  

Microsoft Academic Search

When manufacturing composite dielectric materials with various shapes, sizes, dielectric properties, and amounts of each constituent element, it is beneficial to predict the effective dielectric constant and the distribution of electric fields within the composite. A three-dimensional electromagnetic model has recently been developed at the University of Missouri to aid in this analysis. CST EM Studio, which specializes in three-dimensional

K. A. O'Connor; R. D. Curry

2011-01-01

362

Material properties of piezoelectric composites by BEM and homogenization method  

E-print Network

Material properties of piezoelectric composites by BEM and homogenization method Qing-Hua Qin method (BEM) to piezoelectric composites in conjunction with homogenization approach for determining average stress and strain are calculated by the boundary tractions and displacements of the RVE. Thus BEM

Qin, Qinghua

363

Generating Finite-Element Models Of Composite Materials  

NASA Technical Reports Server (NTRS)

Program starts at micromechanical level, from simple inputs supplied by user. COMGEN, COmposite Model GENerator, is interactive FORTRAN program used to create wide variety of finite-element models of continuous-fiber composite materials at micromechanical level. Quickly generates batch or "session files" to be submitted to finite-element preprocessor and postprocessor program, PATRAN. COMGEN requires PATRAN to complete model.

Melis, M. E.

1993-01-01

364

Composite Materials for Hazard Mitigation of Reactive Metal Hydrides.  

SciTech Connect

In an attempt to mitigate the hazards associated with storing large quantities of reactive metal hydrides, polymer composite materials were synthesized and tested under simulated usage and accident conditions. The composites were made by polymerizing vinyl monomers using free-radical polymerization chemistry, in the presence of the metal hydride. Composites with vinyl-containing siloxane oligomers were also polymerized with and without added styrene and divinyl benzene. Hydrogen capacity measurements revealed that addition of the polymer to the metal hydride reduced the inherent hydrogen storage capacity of the material. The composites were found to be initially effective at reducing the amount of heat released during oxidation. However, upon cycling the composites, the mitigating behavior was lost. While the polymer composites we investigated have mitigating potential and are physically robust, they undergo a chemical change upon cycling that makes them subsequently ineffective at mitigating heat release upon oxidation of the metal hydride. Acknowledgements The authors would like to thank the following people who participated in this project: Ned Stetson (U.S. Department of Energy) for sponsorship and support of the project. Ken Stewart (Sandia) for building the flow-through calorimeter and cycling test stations. Isidro Ruvalcaba, Jr. (Sandia) for qualitative experiments on the interaction of sodium alanate with water. Terry Johnson (Sandia) for sharing his expertise and knowledge of metal hydrides, and sodium alanate in particular. Marcina Moreno (Sandia) for programmatic assistance. John Khalil (United Technologies Research Corp) for insight into the hazards of reactive metal hydrides and real-world accident scenario experiments. Summary In an attempt to mitigate and/or manage hazards associated with storing bulk quantities of reactive metal hydrides, polymer composite materials (a mixture of a mitigating polymer and a metal hydride) were synthesized and tested under simulated usage and accident conditions. Mitigating the hazards associated with reactive metal hydrides during an accident while finding a way to keep the original capability of the active material intact during normal use has been the focus of this work. These composites were made by polymerizing vinyl monomers using free-radical polymerization chemistry, in the presence of the metal hydride, in this case a prepared sodium alanate (chosen as a representative reactive metal hydride). It was found that the polymerization of styrene and divinyl benzene could be initiated using AIBN in toluene at 70 degC. The resulting composite materials can be either hard or brittle solids depending on the cross-linking density. Thermal decomposition of these styrene-based composite materials is lower than neat polystyrene indicating that the chemical nature of the polymer is affected by the formation of the composite. The char-forming nature of cross-linked polystyrene is low and therefore, not an ideal polymer for hazard mitigation. To obtain composite materials containing a polymer with higher char-forming potential, siloxane-based monomers were investigated. Four vinyl-containing siloxane oligomers were polymerized with and without added styrene and divinyl benzene. Like the styrene materials, these composite materials exhibited thermal decomposition behavior significantly different than the neat polymers. Specifically, the thermal decomposition temperature was shifted approximately 100 degC lower than the neat polymer signifying a major chemical change to the polymer network. Thermal analysis of the cycled samples was performed on the siloxane-based composite materials. It was found that after 30 cycles the siloxane-containing polymer composite material has similar TGA/DSC-MS traces as the virgin composite material indicating that the polymer is physically intact upon cycling. Hydrogen capacity measurements revealed that addition of the polymer to the metal hydride in the form of a composite material reduced the inherent hydrogen storage capacity of the material. This

Pratt, Joseph William; Cordaro, Joseph Gabriel; Sartor, George B.; Dedrick, Daniel E.; Reeder, Craig L.

2012-02-01

365

Resistance fail strain gage technology as applied to composite materials  

NASA Technical Reports Server (NTRS)

Existing strain gage technologies as applied to orthotropic composite materials are reviewed. The bonding procedures, transverse sensitivity effects, errors due to gage misalignment, and temperature compensation methods are addressed. Numerical examples are included where appropriate. It is shown that the orthotropic behavior of composites can result in experimental error which would not be expected based on practical experience with isotropic materials. In certain cases, the transverse sensitivity of strain gages and/or slight gage misalignment can result in strain measurement errors.

Tuttle, M. E.; Brinson, H. F.

1985-01-01

366

Microstructure of composite material with powders of barium ferrite  

Microsoft Academic Search

Purpose: The aim of the present work is the microstructure characterization of commercial powder BaFe12O19 (as-prepared) and composite material with BaFe12O19 powders and polymer matrix, using XRD (X-Ray Diffraction) and SEM (Scanning Electron Microscopy) methods. Design\\/methodology\\/approach: The morphology of barium ferrite powders and a fracture surface of the examined composite material was realized by using the scanning electron microscope. The

R. Nowosielski; R. Babilas; G. Dercz; L. Paj?k b

367

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

368

Electrode material comprising graphene-composite materials in a graphite network  

DOEpatents

A durable electrode material suitable for use in Li ion batteries is provided. The material is comprised of a continuous network of graphite regions integrated with, and in good electrical contact with a composite comprising graphene sheets and an electrically active material, such as silicon, wherein the electrically active material is dispersed between, and supported by, the graphene sheets.

Kung, Harold H.; Lee, Jung K.

2014-07-15

369

Soft network composite materials with deterministic and bio-inspired designs.  

PubMed

Hard and soft structural composites found in biology provide inspiration for the design of advanced synthetic materials. Many examples of bio-inspired hard materials can be found in the literature; far less attention has been devoted to soft systems. Here we introduce deterministic routes to low-modulus thin film materials with stress/strain responses that can be tailored precisely to match the non-linear properties of biological tissues, with application opportunities that range from soft biomedical devices to constructs for tissue engineering. The approach combines a low-modulus matrix with an open, stretchable network as a structural reinforcement that can yield classes of composites with a wide range of desired mechanical responses, including anisotropic, spatially heterogeneous, hierarchical and self-similar designs. Demonstrative application examples in thin, skin-mounted electrophysiological sensors with mechanics precisely matched to the human epidermis and in soft, hydrogel-based vehicles for triggered drug release suggest their broad potential uses in biomedical devices. PMID:25782446

Jang, Kyung-In; Chung, Ha Uk; Xu, Sheng; Lee, Chi Hwan; Luan, Haiwen; Jeong, Jaewoong; Cheng, Huanyu; Kim, Gwang-Tae; Han, Sang Youn; Lee, Jung Woo; Kim, Jeonghyun; Cho, Moongee; Miao, Fuxing; Yang, Yiyuan; Jung, Han Na; Flavin, Matthew; Liu, Howard; Kong, Gil Woo; Yu, Ki Jun; Rhee, Sang Il; Chung, Jeahoon; Kim, Byunggik; Kwak, Jean Won; Yun, Myoung Hee; Kim, Jin Young; Song, Young Min; Paik, Ungyu; Zhang, Yihui; Huang, Yonggang; Rogers, John A

2015-01-01

370

Soft network composite materials with deterministic and bio-inspired designs  

PubMed Central

Hard and soft structural composites found in biology provide inspiration for the design of advanced synthetic materials. Many examples of bio-inspired hard materials can be found in the literature; far less attention has been devoted to soft systems. Here we introduce deterministic routes to low-modulus thin film materials with stress/strain responses that can be tailored precisely to match the non-linear properties of biological tissues, with application opportunities that range from soft biomedical devices to constructs for tissue engineering. The approach combines a low-modulus matrix with an open, stretchable network as a structural reinforcement that can yield classes of composites with a wide range of desired mechanical responses, including anisotropic, spatially heterogeneous, hierarchical and self-similar designs. Demonstrative application examples in thin, skin-mounted electrophysiological sensors with mechanics precisely matched to the human epidermis and in soft, hydrogel-based vehicles for triggered drug release suggest their broad potential uses in biomedical devices. PMID:25782446

Jang, Kyung-In; Chung, Ha Uk; Xu, Sheng; Lee, Chi Hwan; Luan, Haiwen; Jeong, Jaewoong; Cheng, Huanyu; Kim, Gwang-Tae; Han, Sang Youn; Lee, Jung Woo; Kim, Jeonghyun; Cho, Moongee; Miao, Fuxing; Yang, Yiyuan; Jung, Han Na; Flavin, Matthew; Liu, Howard; Kong, Gil Woo; Yu, Ki Jun; Rhee, Sang Il; Chung, Jeahoon; Kim, Byunggik; Kwak, Jean Won; Yun, Myoung Hee; Kim, Jin Young; Song, Young Min; Paik, Ungyu; Zhang, Yihui; Huang, Yonggang; Rogers, John A.

2015-01-01

371

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

372

Method of tissue repair using a composite material  

DOEpatents

A composite biocompatible hydrogel material includes a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa. A calcium comprising salt is disposed in at least some of the pores. The porous polymer matrix can comprise cellulose, including bacterial cellulose. The composite can be used as a bone graft material. A method of tissue repair within the body of animals includes the steps of providing a composite biocompatible hydrogel material including a porous polymer matrix, the polymer matrix including a plurality of pores and providing a Young's modulus of at least 10 GPa, and inserting the hydrogel material into cartilage or bone tissue of an animal, wherein the hydrogel material supports cell colonization in vitro for autologous cell seeding.

Hutchens, Stacy A; Woodward, Jonathan; Evans, Barbara R; O'Neill, Hugh M

2014-03-18

373

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

374

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

375

Bearing material. [composite material with low friction surface for rolling or sliding contact  

NASA Technical Reports Server (NTRS)

A composite material is described which will provide low friction surfaces for materials in rolling or sliding contact and is self-lubricating and oxidation resistant up to and in excess of about 930 C. The composite is comprised of a metal component which lends strength and elasticity to the structure, a fluoride salt component which provides lubrication and, lastly, a glass component which not only provides oxidation protection to the metal but may also enhance the lubrication qualities of the composite.

Sliney, H. E. (inventor)

1976-01-01

376

Preparation of Al8B4C7 composite materials by using oxide raw materials  

NASA Astrophysics Data System (ADS)

Al8B4C7 composites materials were prepared by using Al, B2O3 and C as raw materials. The effect of sintering temperature and different additives (Al and C) on Al8B4C7 composites materials were investigated. The Al8B4C7 composites materials were characterized from microstructure, apparent porosity, bulk density and compressive strength. The results demonstrated that the increasing of sintering temperatures could make the samples denser and improve compressive strength. The optimal sintering temperature was 1700 °C, and the main phase composition of Al8B4C7 composites materials were Al8B4C7 and Al2O3. Al additive could improve the properties while C additive played an harmful role. The Al8B4C7 grains were irregular flake and the size was 2~4 ?m.

Zhu, H. X.; Pan, C.; Deng, C. J.; Yuan, W. J.

2011-10-01

377

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

378

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

379

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

380

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

381

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

382

Advanced composites: Environmental effects on selected resin matrix materials  

NASA Technical Reports Server (NTRS)

The effects that expected space flight environment has upon the mechanical properties of epoxy and polyimide matrix composites were analyzed. Environmental phenomena covered water immersion, high temperature aging, humidity, lightning strike, galvanic action, electromagnetic interference, thermal shock, rain and sand erosion, and thermal/vacuum outgassing. The technology state-of-the-art for graphite and boron reinforced epoxy and polyimide matrix materials is summarized to determine the relative merit of using composites in the space shuttle program. Resin matrix composites generally are affected to some degree by natural environmental phenomena with polyimide resin matrix materials less affected than epoxies.

Welhart, E. K.

1976-01-01

383

Multilayer Electroactive Polymer Composite Material Comprising Carbon Nanotubes  

NASA Technical Reports Server (NTRS)

An electroactive material comprises multiple layers of electroactive composite with each layer having unique dielectric, electrical and mechanical properties that define an electromechanical operation thereof when affected by an external stimulus. For example, each layer can be (i) a 2-phase composite made from a polymer with polarizable moieties and an effective amount of carbon nanotubes incorporated in the polymer for a predetermined electromechanical operation, or (ii) a 3-phase composite having the elements of the 2-phase composite and further including a third component of micro-sized to nano-sized particles of an electroactive ceramic incorporated in the polymer matrix.

Ounaies, Zoubeida (Inventor); Park, Cheol (Inventor); Harrison, Joycelyn S. (Inventor); Holloway, Nancy M. (Inventor); Draughon, Gregory K. (Inventor)

2009-01-01

384

Surface characteristics of resin composite materials after finishing and polishing.  

PubMed

This in vitro study determined the surface roughness (Ra) and absolute gloss (AG) values for 2 resin composites: a microhybrid and a microfill. Eight groups (n = 4) of each resin composite were prepared, along with 4 controls (Mylar strip) for the 2 resin composites. After finishing with a medium polishing disc, the specimens from each resin composite material were subjected to 7 polishing procedures, and Ra measurements and AG values were determined. Two-way ANOVA and Fisher's LSD multiple comparisons revealed significant differences (P ? 0.05). For both materials, the control group produced the lowest Ra values and highest AG values, and the medium polishing disc produced the highest Ra values and lowest AG values. Of the 2 resin composites, the microhybrid had lower mean Ra and higher mean AG than the microfill for the majority of the polishing procedures. Pearson's r correlation coefficient (P ? 0.001) indicated an inverse linear relationship between Ra and AG. PMID:25734283

St Germain, Henry; Samuelson, Bart A

2015-01-01

385

Functional composite materials based on chemically converted graphene.  

PubMed

Graphene, a one-atom layer of graphite, possesses a unique two-dimensional structure and excellent mechanical, thermal, and electrical properties. Thus, it has been regarded as an important component for making various functional composite materials. Graphene can be prepared through physical, chemical and electrochemical approaches. Among them, chemical methods were tested to be effective for producing chemically converted graphene (CCG) from various precursors (such as graphite, carbon nanotubes, and polymers) in large scale and at low costs. Therefore, CCG is more suitable for synthesizing high-performance graphene based composites. In this progress report, we review the recent advancements in the studies of the composites of CCG and small molecules, polymers, inorganic nanoparticles or other carbon nanomaterials. The methodology for preparing CCG and its composites has been summarized. The applications of CCG-based functional composite materials are also discussed. PMID:21360763

Bai, Hua; Li, Chun; Shi, Gaoquan

2011-03-01

386

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

387

Structurally integrated fiber optic damage assessment system for composite materials.  

PubMed

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 the threshold of damage for various impacted Kevlar/epoxy panels. The technique has been extended to measure the growth of a damage region which could arise from either impact, manufacturing flaws, or static overloading. The mechanism of optical fiber fracture has also been investigated. In addition, the influence of embedded optical fibers on the tensile and compressive strength of the composite material has been studied. Image enhanced backlighting has been shown to be a powerful and convenient method of assessing internal damage to translucent composite materials. PMID:20555570

Measures, R M; Glossop, N D; Lymer, J; Leblanc, M; West, J; Dubois, S; Tsaw, W; Tennyson, R C

1989-07-01

388

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

389

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.

390

Highly explosive nanosilicon-based composite materials  

Microsoft Academic Search

We present a highly explosive binary system based on porous silicon layers with their pores filled with solid oxidizers. The porous layers are produced by a standard electrochemical etching process and exhibit properties that are different from other energetic materials. Its production is completely compatible with the standard silicon technology and full bulk silicon wafers can be processed and therefore

D. Clément; J. Diener; E. Gross; N. Künzner; V. Yu. Timoshenko; D. Kovalev

2005-01-01

391

Light weight polymer matrix composite material  

NASA Technical Reports Server (NTRS)

A graphite fiber reinforced polymer matrix is layed up, cured, and thermally aged at about 750.degree. F. in the presence of an inert gas. The heat treatment improves the structural integrity and alters the electrical conductivity of the materials. In the preferred embodiment PMR-15 polyimides and Celion-6000 graphite fibers are used.

Bowles, Kenneth J. (Inventor); Lowell, Carl E. (Inventor)

1991-01-01

392

Characterization of ceramic composite materials for gas turbine applications  

Microsoft Academic Search

Ceramic composite materials have the capability to sustain high stress in the presence of high temperatures and aggressive atmospheres. Such materials are being considered for application as cumbustors, burner cubes, heat exchangers, headers. hot-gas filters, and even rotors of stationary gas turbine engines. In the present program, Nicalon preforms of tubular geometry were fabricated with different fiber architectures (filament winding,

K. Reifsnider; W. Stinchcomb; K. Liao; L. Oleksuk; D. Stinton

1993-01-01

393

Composite Materials with Viscoelastic Stiffness Greater Than Diamond  

E-print Network

. Stone,3 R. S. Lakes4 * We show that composite materials can exhibit a viscoelastic modulus (Young of single foam cells (3). The elastic modulus, a stress/strain ratio, is a measure of material stiffness compressibility has been observed in small-cell foams (10). Negative compressibility differs from negative thermal

Lakes, Roderic

394

Finite Element Modeling of the Thermographic Inspection for Composite Materials  

NASA Technical Reports Server (NTRS)

The performance of composite materials is dependent on the constituent materials selected, material structural geometry, and the fabrication process. Flaws can form in composite materials as a result of the fabrication process, handling in the manufacturing environment, and exposure in the service environment to anomalous activity. Often these flaws show no indication on the surface of the material while having the potential of substantially degrading the integrity of the composite structure. For this reason it is important to have available inspection techniques that can reliably detect sub-surface defects such as inter-ply disbonds, inter-ply cracks, porosity, and density changes caused by variations in fiber volume content. Many non-destructive evaluation techniques (NDE) are capable of detecting sub-surface flaws in composite materials. These include shearography, video image correlation, ultrasonic, acoustic emissions, and X-ray. The difficulty with most of these techniques is that they are time consuming and often difficult to apply to full scale structures. An NDE technique that appears to have the capability to quickly and easily detect flaws in composite structure is thermography. This technique uses heat to detect flaws. Heat is applied to the surface of a structure with the use of a heat lamp or heat gun. A thermographic camera is then pointed at the surface and records the surface temperature as the composite structure cools. Flaws in the material will cause the thermal-mechanical material response to change. Thus, the surface over an area where a flaw is present will cool differently than regions where flaws do not exist. This paper discusses the effort made to thermo-mechanically model the thermography process. First the material properties and physical parameters used in the model will be explained. This will be followed by a detailed discussion of the finite element model used. Finally, the result of the model will be summarized along with recommendations for future work.

Bucinell, Ronald B.

1996-01-01

395

Emissivity Results on High Temperature Coatings for Refractory Composite Materials  

NASA Technical Reports Server (NTRS)

The directional emissivity of various refractory composite materials considered for application for reentry and hypersonic vehicles was investigated. The directional emissivity was measured at elevated temperatures of up to 3400 F using a directional spectral radiometric technique during arc-jet test runs. A laboratory-based relative total radiance method was also used to measure total normal emissivity of some of the refractory composite materials. The data from the two techniques are compared. The paper will also compare the historical database of Reinforced Carbon-Carbon emissivity measurements with emissivity values generated recently on the material using the two techniques described in the paper.

Ohlhorst, Craig W.; Vaughn, Wallace L.; Daryabeigi, Kamran; Lewis, Ronald K.; Rodriguez, Alvaro C.; Milhoan, James D.; Koenig, John R.

2007-01-01

396

DOE Automotive Composite Materials Research: Present and Future Efforts  

SciTech Connect

One method of increasing automotive energy efficiency is through mass reduction of structural components by the incorporation of composite materials. Significant use of glass reinforced polymers as structural components could yield a 20--30% reduction in vehicle weight while the use of carbon fiber reinforced materials could yield a 40--60% reduction in mass. Specific areas of research for lightweighting automotive components are listed, along with research needs for each of these categories: (1) low mass metals; (2) polymer composites; and (3) ceramic materials.

Warren, C.D.

1999-08-10

397

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

398

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

399

Acoustic emission from composite materials. [nondestructive tests  

NASA Technical Reports Server (NTRS)

The two basic areas where the acoustic emission (AE) technique can be applied are materials research and the evaluation of structural reliability. This experimental method leads to a better understanding of fracture mechanisms and is an NDT technique particularly well suited for the study of propagating cracks. Experiments are described in which acoustic emissions were unambiguously correlated with microstructural fracture mechanisms. The advantages and limitations of the AE technique are noted.

Visconti, I. C.; Teti, R.

1979-01-01

400

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

401

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

402

A novel hybrid finite element model for modeling anisotropic composites Changyong Cao a  

E-print Network

materials which can be joined together to provide required engineering properties, such as specified in-plane conditions between elements, is proposed to derive the element stiffness equation. In this work stiffness, bending stiffness, strength, and coef- ficient of thermal expansion (see Fig. 1) [1]. Individual

Qin, Qinghua

403

Thermal pretreatment of silica composite filler materials.  

PubMed

Three different silica filler materials were thermally treated in order to effect dehydration, dehydroxylation, and rehydroxylation. Samples were characterized by thermogravimetry (TG), pycnometry, elemental analysis, and scanning electron microscopy (SEM). For all fillers, our results indicate incremental removal of silanol groups at higher heating temperatures and irreversible dehydroxylation at over 673 K. To remove the organic content and maintain adequate silanol density for subsequent silanization on Stöber-type silica, we suggest heating at 673 K followed by overnight boiling in water. PMID:20445821

Wan, Quan; Ramsey, Christopher; Baran, George

2010-01-01

404

Thermal, mechanical, and electroelastic behavior of composite materials  

SciTech Connect

A unified analytical approach is developed to predict the effective behavior of composite materials for electronic applications. The target applications are materials for electronic packaging and electromechanical transducers where the material properties of interest are the effective thermal expansion coefficients, thermal conductivity, dielectric constant, and the couples electroelastic behavior. The analytical approach that is forwarded is based on the equivalent inclusion method of Eshelby (1957) extended to finite reinforcement concentrations through the Mori-Tanaka (1973) mean field approach. In addition to the effects of the material properties of the constituents, the effects of the volume fraction, shape, and orientation distribution of the reinforcing phase are considered. Through this approach, internal stresses generated due to the mismatch in thermal expansion coefficients of the constituents of a composite material are studied. Thermal expansion coefficients and time dependent creep deformations under a constant applied stress are analyzed. Analytical predictions of the proposed model are seen to be in good agreement with measured results of a multiphase Al2O3/Si3N4/Kerimid composite. The Mori-Tanaka mean field approach is also utilized to study the effective physical properties, modeled by Laplace's equation, of composite materials. Particular attention is devoted to microdamaged composites containing porosity or microcracks in the matrix and composites with coated reinforcement. Analytical predictions are shown to be in good agreement with measured results of the effective thermal conductivity for a multiphase Al2O3/Si3N4/Kerimid composite. Finally, the rigorous analytical solution for the couples electroelastic behavior of piezoelectric inclusions (Deeg, 1980) is utilized to derive the constraint tensors for an ellipsoidal piezoelectric inclusion in a infinite matrix.

Dunn, M.L.

1992-01-01

405

Review on advanced composite materials boring mechanism and tools  

NASA Astrophysics Data System (ADS)

With the rapid development of aviation and aerospace manufacturing technology, advanced composite materials represented by carbon fibre reinforced plastics (CFRP) and super hybrid composites (fibre/metal plates) are more and more widely applied. The fibres are mainly carbon fibre, boron fibre, Aramid fiber and Sic fibre. The matrixes are resin matrix, metal matrix and ceramic matrix. Advanced composite materials have higher specific strength and higher specific modulus than glass fibre reinforced resin composites of the 1st generation. They are widely used in aviation and aerospace industry due to their high specific strength, high specific modulus, excellent ductility, anticorrosion, heat-insulation, sound-insulation, shock absorption and high&low temperature resistance. They are used for radomes, inlets, airfoils(fuel tank included), flap, aileron, vertical tail, horizontal tail, air brake, skin, baseboards and tails, etc. Its hardness is up to 62~65HRC. The holes are greatly affected by the fibre laminates direction of carbon fibre reinforced composite material due to its anisotropy when drilling in unidirectional laminates. There are burrs, splits at the exit because of stress concentration. Besides there is delamination and the hole is prone to be smaller. Burrs are caused by poor sharpness of cutting edge, delamination, tearing, splitting are caused by the great stress caused by high thrust force. Poorer sharpness of cutting edge leads to lower cutting performance and higher drilling force at the same time. The present research focuses on the interrelation between rotation speed, feed, drill's geometry, drill life, cutting mode, tools material etc. and thrust force. At the same time, holes quantity and holes making difficulty of composites have also increased. It requires high performance drills which won't bring out defects and have long tool life. It has become a trend to develop super hard material tools and tools with special geometry for drilling composite materials.

Shi, Runping; Wang, Chengyong

2010-12-01

406

Review on advanced composite materials boring mechanism and tools  

NASA Astrophysics Data System (ADS)

With the rapid development of aviation and aerospace manufacturing technology, advanced composite materials represented by carbon fibre reinforced plastics (CFRP) and super hybrid composites (fibre/metal plates) are more and more widely applied. The fibres are mainly carbon fibre, boron fibre, Aramid fiber and Sic fibre. The matrixes are resin matrix, metal matrix and ceramic matrix. Advanced composite materials have higher specific strength and higher specific modulus than glass fibre reinforced resin composites of the 1st generation. They are widely used in aviation and aerospace industry due to their high specific strength, high specific modulus, excellent ductility, anticorrosion, heat-insulation, sound-insulation, shock absorption and high&low temperature resistance. They are used for radomes, inlets, airfoils(fuel tank included), flap, aileron, vertical tail, horizontal tail, air brake, skin, baseboards and tails, etc. Its hardness is up to 62~65HRC. The holes are greatly affected by the fibre laminates direction of carbon fibre reinforced composite material due to its anisotropy when drilling in unidirectional laminates. There are burrs, splits at the exit because of stress concentration. Besides there is delamination and the hole is prone to be smaller. Burrs are caused by poor sharpness of cutting edge, delamination, tearing, splitting are caused by the great stress caused by high thrust force. Poorer sharpness of cutting edge leads to lower cutting performance and higher drilling force at the same time. The present research focuses on the interrelation between rotation speed, feed, drill's geometry, drill life, cutting mode, tools material etc. and thrust force. At the same time, holes quantity and holes making difficulty of composites have also increased. It requires high performance drills which won't bring out defects and have long tool life. It has become a trend to develop super hard material tools and tools with special geometry for drilling composite materials.

Shi, Runping; Wang, Chengyong

2011-05-01

407

Cytotoxicity of composite materials polymerized with LED curing units.  

PubMed

The proper intensity and illumination time of a curing light is of great importance for the complete polymerization of resin composites and long-lasting resin composite restorations. Inadequately cured resin composites can have a cytotoxic effect on pulp tissue by releasing unreacted monomers. This study determined whether there is any difference in cytotoxicity between composite materials illuminated with different curing modes of LED curing units. Thin layers of two composite materials were polymerized using three different modes of the Bluephase C8 LED curing unit: a high intensity mode (HIP-800 mW/cm2, 20 seconds), a soft-start mode (SOF-650 mW/cm2 first 5 seconds, 800 mW/cm2 next 25 seconds) and a low intensity mode (LOP-650 mW/cm2, 30 seconds). Lymphocyte cultures were treated with both polymerized and unpolymerized composites using one of the modes stated above. Cells were analyzed using the trypan blue exclusion test, the acridine orange/ethidium bromide dying technique and an alkaline comet assay. Significant cytotoxicity was observed for 120 mg of unpolymerized composites and those polymerized with the HIP polymerization mode. A significant level of DNA damage was detected for 120 mg of unpolymerized composites. However, curing via the LOP program exhibited the lowest genotoxicity. Longer curing time with lower intensity results in less cytotoxicity than shorter curing exposure using a higher intensity of light emitted from the curing light source. PMID:18335729

Knezevic, Alena; Zeljezic, Davor; Kopjar, Nevenka; Tarle, Zrinka

2008-01-01

408

Annual Conference on Composites and Advanced Ceramic Materials  

SciTech Connect

The proceedings examine current status and future prospects for engineering ceramics and discuss topics on the reinforcements and interfaces of ceramic-matrix composites, the oxide-matrix and nonoxide-matrix composites, and the fracture and mechanical behaviors in ceramic matrix composites. Papers are presented on an Air Force high-temperature materials program, a high-temperature continuous sintered SiC fiber for composite applications, silylene-acetylene polymers as precursors to SiC fibers, the material characterization of chemical-vapor-deposited TiB2 fibers, and an investigation of interfacial shear strength in SiC/Si3N4 composites. Attention is also given to an evaluation of SiC platelets as a reinforcement for oxide matrix composites, physical properties of alumina-boron carbide whisker/particle composites, hot isostatic pressing of sintered Si3N4 ceramics, the influence of the Si3N4 microstructure on its R-curve and fatigue behavior, and acoustic emission characterization of the fracture mechanism of a glass-matrix composite.

Not Available

1991-10-01

409

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

410

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

411

Thermal radiation transmission through composite material  

NASA Astrophysics Data System (ADS)

On 10 June 1993, the Defense Nuclear Agency (DNA) Field Command at White Sands Missile Range conducted a Thermal Radiation Simulator (TRS) test for the Naval Surface Warfare Center (NSWC) during project MINOR UNCLE. The NSWC was interested in measuring the radiant thermal energy absorbed by a fiberglass panel during a simulated nuclear weapon event. The resultant thermocouple data showed an unusual initial high-temperature rise and fall, followed by the expected conductive heating. The initial transient was theorized to be the result of thermal radiation transmitted through the panel. To investigate this theory, NSWC prepared several more panels of different thicknesses, preinstrumented with thermocouples and strain gages for testing with a U.S. Army Research Laboratory (ARL) TRS. ARL also provided additional instrumentation to measure thermal radiation on the front surface as well as behind the panel. The results showed that there was direct heating of the rear of the composite panel by thermal radiation. The quantity of heat transmission through the panel and the point of ignition of the front surface of the panel were determined. Smoke and charring of the front surface protected the panel from further heating and possible destruction.

Loucks, Richard B.

1995-06-01

412

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

413

Tunneling conductivity in anisotropic nanofiber composites: a percolation-based model.  

PubMed

The critical path approximation ('CPA') is integrated with a lattice-based approach to percolation to provide a model for conductivity in nanofiber-based composites. Our treatment incorporates a recent estimate for the anisotropy in tunneling-based conductance as a function of the relative angle between the axes of elongated nanoparticles. The conductivity is examined as a function of the volume fraction, degree of clustering, and of the mean value and standard deviation of the orientational order parameter. Results from our calculations suggest that the conductivity can depend strongly upon the standard deviation in the orientational order parameter even when all the other variables (including the mean value of the order parameter ?S?) are held invariant. PMID:25788468

Chatterjee, Avik P; Grimaldi, Claudio

2015-04-15

414

Tunneling conductivity in anisotropic nanofiber composites: a percolation-based model  

NASA Astrophysics Data System (ADS)

The critical path approximation (‘CPA’) is integrated with a lattice-based approach to percolation to provide a model for conductivity in nanofiber-based composites. Our treatment incorporates a recent estimate for the anisotropy in tunneling-based conductance as a function of the relative angle between the axes of elongated nanoparticles. The conductivity is examined as a function of the volume fraction, degree of clustering, and of the mean value and standard deviation of the orientational order parameter. Results from our calculations suggest that the conductivity can depend strongly upon the standard deviation in the orientational order parameter even when all the other variables (including the mean value of the order parameter ) are held invariant.

Chatterjee, Avik P.; Grimaldi, Claudio

2015-04-01

415

Highly explosive nanosilicon-based composite materials  

NASA Astrophysics Data System (ADS)

We present a highly explosive binary system based on porous silicon layers with their pores filled with solid oxidizers. The porous layers are produced by a standard electrochemical etching process and exhibit properties that are different from other energetic materials. Its production is completely compatible with the standard silicon technology and full bulk silicon wafers can be processed and therefore a large number of explosive elements can be produced simultaneously. The application-relevant parameters: the efficiency and the long-term stability of various porous silicon/oxidizer systems have been studied in details. Structural properties of porous silicon, its surface termination, the atomic ratio of silicon to oxygen and the chosen oxidizers were optimized to achieve the highest efficiency of the explosive reaction. This explosive system reveals various possible applications in different industrial fields, e.g. as a novel, very fast airbag igniter.

Clément, D.; Diener, J.; Gross, E.; Künzner, N.; Timoshenko, V. Yu.; Kovalev, D.

2005-06-01

416

A new technique for simulating composite material  

NASA Technical Reports Server (NTRS)

This project dealt with the development on new methodologies and algorithms for the multi-spectrum electromagnetic characterization of large scale nonmetallic airborne vehicles and structures. A robust, low memory, and accurate methodology was developed which is particularly suited for modern machine architectures. This is a hybrid finite element method that combines two well known numerical solution approaches. That of the finite element method for modeling volumes and the boundary integral method which yields exact boundary conditions for terminating the finite element mesh. In addition, a variety of high frequency results were generated (such as diffraction coefficients for impedance surfaces and material layers) and a class of boundary conditions were developed which hold promise for more efficient simulations. During the course of this project, nearly 25 detailed research reports were generated along with an equal number of journal papers. The reports, papers, and journal articles are listed in the appendices along with their abstracts.

Volakis, John L.

1991-01-01

417

Military turbojet component design and validation with thermostructural composite material  

SciTech Connect

Ceramic Matrix Composite (CMC) materials based on a concept providing both high temperature capabilities and high mechanical strength can meet new turbojet requirements. They have the potential to enhance performance and durability of pertinent parts. Lab characterization performed on test samples showed that SEPCARBINOX {reg_sign} C/SiC composites with adequate finishing treatments can sustain temperatures up to 600 - 650{degrees}C for long duration and CERASEP {reg_sign} SiC/SiC composites can sustain temperatures up to 1200{degrees}C. A large amount of R&D activities at SEP on CMC components over the last 10 years have demonstrated a good potential for C/SiC and SiC/SiC composites and brought design experience and methodology for developments. In the future, engines should be able to take advantage of an improved thermostructural material specifically developed for turbojet environment.

Spriet, P.; Boury, D.; Habarou, G. [SEP, Saint-Medard-en-Jalles (France)

1995-12-01

418

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

419

Improved Composites Using Crosslinked, Surface-Modified Carbon Nanotube Materials  

NASA Technical Reports Server (NTRS)

Individual carbon nanotubes (CNTs) exhibit exceptional tensile strength and stiffness; however, these properties have not translated well to the macroscopic scale. Premature failure of bulk CNT materials under tensile loading occurs due to the relatively weak frictional forces between adjacent CNTs, leading to poor load transfer through the material. When used in polymer matrix composites (PMCs), the weak nanotube-matrix interaction leads to the CNTs providing less than optimal reinforcement.Our group is examining the use of covalent crosslinking and surface modification as a means to improve the tensile properties of PMCs containing carbon nanotubes. Sheet material comprised of unaligned multi-walled carbon nanotubes (MWCNT) was used as a drop-in replacement for carbon fiber in the composites. A variety of post-processing methods have been examined for covalently crosslinking the CNTs to overcome the weak inter-nanotube shear interactions, resulting in improved tensile strength and modulus for the bulk sheet material. Residual functional groups from the crosslinking chemistry may have the added benefit of improving the nanotube-matrix interaction. Composites prepared using these crosslinked, surface-modified nanotube sheet materials exhibit superior tensile properties to composites using the as received CNT sheet material.

Baker, James Stewart

2014-01-01

420

Mechanical Properties of Composite Material Using Coal Ash and Clay  

NASA Astrophysics Data System (ADS)

Coal ash is industry waste exhausted lots of amount by electric power plant. The particle sizes of coal ash, especially coal fly ash are very fine, and the chemical component are extremely resemble with Okinawa-Kucha clay. From the point of view that clay is composed of particles of micro meter size in diameter, we should try the application for fabrication of composite material using coal fly ash and clay. The comparison of the mechanical properties of composite material using coal fly ash and clay were performed during electric furnace burning and spark plasma sintering. As a result, the bending strength of composite material containing the coal ash 10% and fired at 1423K using the electric furnace after press forming at 30 MPa showed the highest value of 47 MPa. This phenomenon suggests a reinforcement role of coal ash particles to clay base material. In spark plasma sintering process, the bending strength of the composite material containing the clay 5-10% to fly ash base material fired at 1473K and pressured at 20 MPa showed the highest value of 88 MPa. This result indicates a binder effect of clay according to the liquid phase sintering of melted clay surrounding around coal fly ash particles surface.

Fukumoto, Isao; Kanda, Yasuyuki

421

Grained composite materials prepared by combustion synthesis under mechanical pressure  

DOEpatents

Dense, finely grained composite materials comprising one or more ceramic phase or phase and one or more metallic and/or intermetallic phase or phases are produced by combustion synthesis. Spherical ceramic grains are homogeneously dispersed within the matrix. Methods are provided, which include the step of applying mechanical pressure during or immediately after ignition, by which the microstructures in the resulting composites can be controllably selected.

Dunmead, Stephen D. (Davis, CA); Holt, Joseph B. (San Jose, CA); Kingman, Donald D. (Danville, CA); Munir, Zuhair A. (Davis, CA)

1990-01-01

422

Nondestructive Evaluation of Anisotropy in Composite Materials Via Acoustic Birefringence  

Microsoft Academic Search

A linearly polarized ultrasonic shear wave propagating in fiber-reinforced composites produces an elliptical vibration pattern due to birefringence. The acoustic birefringence of shear waves is analyzed and applied for evaluation of in-plane stiffness anisotropy of uni-axial nonfabric, biaxial, and quadra-axial fabric composite materials. The parameters of the elliptical motion are determined by measurements of the amplitude and phase of the

Igor Solodov; Klaus Pfleiderer; Daniel Doring; Gerd Busse

2008-01-01

423

Effects of thermal cycling on composite materials for space structures  

NASA Technical Reports Server (NTRS)

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

Tompkins, Stephen S.

1989-01-01

424

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

425

Effective mechanical, transport and cross properties for distressed composite materials  

NASA Astrophysics Data System (ADS)

Composite materials and materials that have been subjected to varying level of damage have been the subject of extensive research for several decades especially with regard to prediction of constitutive behavior. Classical homogenization techniques aim at replacing an actual heterogeneous body by a fictitious homogeneous solid, which globally behaves in the same way. In this thesis, we are considering the effect of body forces as an external forcing on the mechanical behavior of a heterogeneous material and the effect of heat source on the thermal constitutive equations, when the heterogeneous material is replaced by a fictitious or equivalent homogeneous material. In order to achieve these objectives, as the first step, we use the theorems of minimum strain and minimum complementary energies to modify the bounds for strain energy in linear elasticity in order to consider the effect of body force. By means of the strain energy bounds and using the canonical form of the elasticity tensor for an isotropic material, bounds for the effective bulk and shear moduli of two- or multi-phase non-homogeneous materials may separately be obtained. With the same method by using defined artificial thermal and heat flux energies available in literatures, the bounds for the artificial or equivalent thermal energy are modified in the case of the existence of a heat source. By means of the bounds for equivalent thermal and heat flux energies, the bounds of the effective thermal conductivity of two- or multi-isotropic phase non-homogeneous materials may be obtained. Then, in the case of the existence of a heat source, the effective conductivity of composite materials comprising of a linear isotropic matrix containing linear isotropic inclusions, is evaluated in the frameworks of a self-consistent model. Next, the differential scheme and Mori-Tanaka method are modified for the case of an existing heat source to evaluate the effective conductivity of the composite materials (linear isotropic matrix containing linear isotropic inclusions). The last part of the thesis is related to the effect of severe environmental conditions on the behavior of a composite material such as concrete. Freezing of liquid solutions in the solid matrix before damage occurs, causes the diffusivity of the concrete to be reduced, and after damage due to tensile stress in the concrete, which itself is due to increasing the volume of the solution during freezing, thus causing the diffusivity to increase. Based on composite mechanics and within the framework of self-consistent models, a theory is introduced to consider these effects on the diffusivity of concrete as a composite material. (Abstract shortened by UMI.)

Eskandari-Ghadi, Morteza

426

Hot extruded carbon nanotube reinforced aluminum matrix composite materials.  

PubMed

Carbon nanotube (CNT) reinforced aluminum (Al) matrix composite materials were successfully fabricated by mechanical ball milling followed by powder hot extrusion processes. Microstructural analysis revealed that the CNTs were well dispersed at the boundaries and were aligned with the extrusion direction in the composites obtained. Although only a small quantity of CNTs were added to the composite (1 vol%), the Vickers hardness and the tensile strength were significantly enhanced, with an up to three-fold increase relative to that of pure Al. From the fractography of the extruded Al-CNT composite, several shapes were observed in the fracture surface, and this unique morphology is discussed based on the strengthening mechanism. The damage in the CNTs was investigated with Raman spectroscopy. However, the Al-CNT composite materials were not only strengthened by the addition of CNTs but also enhanced by several synergistic effects. The nanoindentation stress-strain curve was successfully constructed by setting the effective zero-load and zero-displacement points and was compared with the tensile stress-strain curve. The yield strengths of the Al-CNT composites from the nanoindentation and tensile tests were compared and discussed. We believe that the yield strength can be predicted using a simple nanoindentation stress/strain curve and that this method will be useful for materials that are difficult to machine, such as complex ceramics. PMID:23011263

Kwon, Hansang; Leparoux, Marc

2012-10-19

427

Electrostatic Discharge Sensitivity and Electrical Conductivity of Composite Energetic Materials  

SciTech Connect

Composite energetic material response to electrical stimuli was investigated and a correlation between electrical conductivity and ignition sensitivity was examined. The composites consisted of micrometer particle aluminum combined with another metal, metal oxide, or fluoropolymer. Of the nine tested mixtures, aluminum with copper oxide was the only mixture to ignite by electrostatic discharge with minimum ignition energy (MIE) of 25 mJ and an electrical conductivity of 1246.25 nS; two orders of magnitude higher than the next composite. This study showed a similar trend in MIE for ignition triggered by a discharged spark compared with a thermal hot wire source.

Michael A. Daniels; Daniel J. Prentice; Chelsea Weir; Michelle L. Pantoya; Gautham Ramachandran; Tim Dallas

2013-02-01

428

Composite Overwrapped Pressure Vessels (COPV) Materials Aging Issues  

NASA Technical Reports Server (NTRS)

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

2010-01-01

429

Thermal design of composite material high temperature attachments  

NASA Technical Reports Server (NTRS)

An evaluation has been made of the thermal aspects of utilizing advanced filamentary composite materials as primary structures on the shuttle vehicle. The technical objectives of this study are to: (1) establish and design concepts for maintaining material temperatures within allowable limits at TPS attachments and or penetrations applicable to the space shuttle; and (2) verify the thermal design analysis by testing selected concepts. Specific composite materials being evaluated are boron epoxy, graphite/epoxy, boron polyimide, and boron aluminum; graphite/polyimide has been added to this list for property data identification and preliminary evaluation of thermal design problems. The TPS standoff to composite structure attachment over-temperature problem is directly related to TPS maximum surface temperature. To provide a thermally comprehensive evaluation of attachment temperature characteristics, maximum surface temperatures of 900 F, 1200 F, 1800 F, 2500 F and 3000 F are considered in this study. This range of surface temperatures and the high and low maximum temperature capability of the selected composite materials will result in a wide range of thermal requirements for composite/TPS standoff attachments.

1972-01-01

430

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

431

Optimizing material properties of composite plates for sound transmission problem  

NASA Astrophysics Data System (ADS)

To calculate the specific transmission loss (TL) of a composite plate, the conjugate gradient optimization method is utilized to estimate and optimize material properties of the composite plate in this study. For an n-layer composite plate, a nonlinear dynamic stiffness matrix based on the thick plate theory is formulated. To avoid huge computational efforts due to the combination of different composite material plates, a transfer matrix approach is proposed to restrict the dynamic stiffness matrix of the composite plate to a 4×4 matrix. Moreover, the transfer matrix approach has also been used to simplify the complexity of the objective function gradient for the optimization method. Numerical simulations are performed to validate the present algorithm by comparing the TL of the optimal composite plate with that of the original plate. Small number of iterations required during convergence tests illustrates the efficiency of the optimization method. The results indicate that an excellent estimation for the composite plate can be obtained for the desired sound transmission.

Tsai, Yu-Ting; Pawar, S. J.; Huang, Jin H.

2015-01-01

432

Chatter control in the milling process of composite materials  

NASA Astrophysics Data System (ADS)

In this paper, a model of the milling process of fibre reinforced composite material is shown. This classical one degree of freedom model of the milling process is adjusted for composite materials by variable specific cutting forces, which describe the fibre resistance. The stability lobe diagrams are determined numerically. Additionally, to eliminate the chatter vibration, small relative oscillations between the workpiece and the tool are introduced. Basing on numerical simulations the range of amplitude and the frequency of excitation is found for chatter reduction.

Kecik, K.; Rusinek, R.; Warminski, J.; Weremczuk, A.

2012-08-01

433

Experimental determination of material constants of a hybrid composite laminate  

SciTech Connect

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

Ihekweazu, S.N.; Lari, S.B.; Unanwa, C.O. [South Carolina State Univ., Orangeburg, SC (United States)

1999-07-01

434

Characterization of ceramic composite materials for gas turbine applications  

SciTech Connect

Ceramic composite materials have the capability to sustain high stress in the presence of high temperatures and aggressive atmospheres. Such materials are being considered for application as cumbustors, burner cubes, heat exchangers, headers. hot-gas filters, and even rotors of stationary gas turbine engines. In the present program, Nicalon preforms of tubular geometry were fabricated with different fiber architectures (filament winding, 3D braiding, or cloth winding) to tailor the mechanical properties for specific applications. However, these applications require that candidate materials be carefully characterized. Mechanical characterization must establish the properties and performance that are essential for structural design of the turbine components. For this purpose, a full complement of properties is needed, i.e., the stiffness and strengths of the composite material at a range of temperatures, and the fatigue and creep behavior of the materials under the stress states anticipated by the user. This mechanical characterization requires specialized equipment and methodologies, which are now under development by the authors. This paper will present a description of the methodologies required for ceramic composite characterization, and will describe initial results for ceramic composite tubes, a representative geometry for gas turbine components. Future needs and opportunities will also be discussed.

Reifsnider, K.; Stinchcomb, W.; Liao, K.; Oleksuk, L. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States); Stinton, D. [Oak Ridge National Lab., TN (United States)

1993-05-01

435

Characterization of ceramic composite materials for gas turbine applications  

SciTech Connect

Ceramic composite materials have the capability to sustain high stress in the presence of high temperatures and aggressive atmospheres. Such materials are being considered for application as cumbustors, burner cubes, heat exchangers, headers. hot-gas filters, and even rotors of stationary gas turbine engines. In the present program, Nicalon preforms of tubular geometry were fabricated with different fiber architectures (filament winding, 3D braiding, or cloth winding) to tailor the mechanical properties for specific applications. However, these applications require that candidate materials be carefully characterized. Mechanical characterization must establish the properties and performance that are essential for structural design of the turbine components. For this purpose, a full complement of properties is needed, i.e., the stiffness and strengths of the composite material at a range of temperatures, and the fatigue and creep behavior of the materials under the stress states anticipated by the user. This mechanical characterization requires specialized equipment and methodologies, which are now under development by the authors. This paper will present a description of the methodologies required for ceramic composite characterization, and will describe initial results for ceramic composite tubes, a representative geometry for gas turbine components. Future needs and opportunities will also be discussed.

Reifsnider, K.; Stinchcomb, W.; Liao, K.; Oleksuk, L. (Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States)); Stinton, D. (Oak Ridge National Lab., TN (United States))

1993-01-01

436

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

437

Development and Analysis of Synthetic Composite Materials Emulating Patient AAA Wall Material Properties  

NASA Astrophysics Data System (ADS)

Abdominal Aortic Aneurysm (AAA) rupture accounts for 14,000 deaths a year in the United States. Since the number of ruptures has not decreased significantly in recent years despite improvements in imaging and surgical procedures, there is a need for an accurate, noninvasive technique capable of establishing rupture risk for specific patients and discriminating lesions at high risk. In this project, synthetic composite materials replicating patient-specific wall stiffness and strength were developed and their material properties evaluated. Composites utilizing various fibers were developed to give a range of stiffness from 1825.75 kPa up through 8187.64 kPa with one base material, Sylgard 170. A range of strength from 631.12 kPa to 1083 kPa with the same base material was also found. By evaluating various base materials and various reinforcing fibers, a catalogue of stiffnesses and strengths was started to allow for adaptation to specific patient properties. Three specific patient properties were well-matched with two composites fabricated: silk thread-reinforced Sylgard 170 and silk thread-reinforced Dragon Skin 20. The composites showed similar stiffnesses to the specific patients while reaching target stresses at particular strains. Not all patients were matched with composites as of yet, but recommendations for future matches are able to be determined. These composites will allow for the future evaluation of flow-induced wall stresses in models replicating patient material properties and geometries.

Margossian, Christa M.

438

Temperature effect on stress concentration around circular hole in a composite material specimen representative of X-29A forward-swept wing aircraft  

NASA Technical Reports Server (NTRS)

The theory of anisotropic elasticity was used to evaluate the anisotropic stress concentration factors of a composite laminated plate containing a small circular hole. This advanced composite was used to manufacture the X-29A forward-swept wing. It was found for composite material, that the anisotropic stress concentration is no longer a constant, and that the locations of maximum tangential stress points could shift by changing the fiber orientation with respect to the loading axis. The analysis showed that through the lamination process, the stress concentration factor could be reduced drastically, and therefore the structural performance could be improved. Both the mixture rule approach and the constant strain approach were used to calculate the stress concentration factor of room temperature. The results predicted by the mixture rule approach were about twenty percent deviate from the experimental data. However, the results predicted by the constant strain approach matched the testing data very well. This showed the importance of the inplane shear effect on the evaluation of the stress concentration factor for the X-29A composite plate.

Yeh, Hsien-Yang

1988-01-01