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1

Modelling the shock response of a damageable anisotropic composite material  

NASA Astrophysics Data System (ADS)

The purpose of this paper is the investigation of the effect of fibre orientation on the shock response of a damageable carbon fibre-epoxy composite (CFEC). A carbon fibre-epoxy composite (CFEC) shock response in the through-thickness orientation and in one of the fibre directions is significantly different. Modelling the effect of fibre orientation on the shock response of a CFEC has been performed using a generalised decomposition of the stress tensor [A.A. Lukyanov, Int. J. Plasticity 24, 140 (2008)] and an accurate extrapolation of high-pressure shock Hugoniot states to other thermodynamics states for shocked CFEC materials. The analysis of the experimental data subject to the linear relation between shock velocities and particle velocities has shown that damage softening process produces discontinuities both in value and slope in the generalized bulk shock velocity and particle velocity relation [A.A. Lukyanov, Eur Phys J B 74, 35 (2010)]. Therefore, in order to remove these discontinuities, the three-wave structure (non-linear anisotropic, fracture and isotropic elastic waves) that accompanies damage softening process is proposed in this work for describing CFEC behavior under shock loading. A numerical calculation shows that Hugoniot Stress Levels (HELs) agree with the experimental data for selected CFEC material in different directions at low and at high intensities. In the through-thickness orientation, the material behaves similar to a simple polymer. In the fibre direction, the proposed model explains a pronounced ramp, before at sufficiently high stresses, and a much faster rising shock above it. The results are presented and discussed, and future studies are outlined.

Lukyanov, Alexander A.

2012-09-01

2

Defect imaging with elastic waves in inhomogeneous-anisotropic materials with composite geometries.  

PubMed

Imaging of defects in composite structures plays an important role in non-destructive testing (NDT) with elastic waves, i.e., ultrasound. Traditionally the imaging of such defects is performed using the synthetic aperture focusing technique (SAFT) algorithm assuming homogeneous isotropic materials. However, if parts of the structure are inhomogeneous and/or anisotropic, this algorithm fail to produce correct results that are needed in order to asses the lifetime of the part under test. Here we present a modification of this algorithm which enables a correct imaging of defects in inhomogeneous and/or anisotropic composite structures, whence it is termed InASAFT. The InASAFT is based on the exact modelling of the structure in order to account for the true nature of the elastic wave propagation using travel time ray tracing techniques. The algorithm is validated upon several numerical and real life examples yielding satisfactory results for imaging of cracks. The modified algorithm suffers, though, from the same difficulties encountered in the SAFT algorithm, namely "ghost" images and eventual lack of clear focused images. However, these artifacts can be identified using a forward wave propagation analysis of the structure. PMID:17258256

Shlivinski, A; Langenberg, K J

2007-03-01

3

Modeling the anisotropic finite-deformation viscoelastic behavior of soft fiber-reinforced composite materials.  

SciTech Connect

This paper presents constitutive models for the anisotropic, finite-deformation viscoelastic behavior of soft fiber-reinforced composites. An essential assumption of the models is that both the fiber reinforcements and matrix can exhibit distinct time-dependent behavior. As such, the constitutive formulation attributes a different viscous stretch measure and free energy density to the matrix and fiber phases. Separate flow rules are specified for the matrix and the individual fiber families. The flow rules for the fiber families then are combined to give an anisotropic flow rule for the fiber phase. This is in contrast to many current inelastic models for soft fiber-reinforced composites which specify evolution equations directly at the composite level. The approach presented here allows key model parameters of the composite to be related to the properties of the matrix and fiber constituents and to the fiber arrangement. An efficient algorithm is developed for the implementation of the constitutive models in a finite-element framework, and examples are presented examining the effects of the viscoelastic behavior of the matrix and fiber phases on the time-dependent response of the composite.

Nguyen, Tai D.; Boyce, Brad Lee (Sandia National Laboratories, Albuquerque, NM); Jones, Reese E.

2007-02-01

4

The anisotropic heat-affected zone in the laser grooving of fiber-reinforced composite material  

Microsoft Academic Search

A heat-affected zone is frequently associated with the laser processing of materials. In the shaping of composite material after curing, thermal damage is found, such as matrix recession, matrix decomposition, and delamination, which lead to poor assembly tolerance and long-term performance deterioration. The current study analyzes the peculiar growth of the heat-affected zone due to laser energy and the anisotropy

C. T. Pan; H. Hocheng

1996-01-01

5

Fluid-structure interaction in water-filled thin pipes of anisotropic composite materials  

NASA Astrophysics Data System (ADS)

The effects of elastic anisotropy in piping materials on fluid-structure interaction are studied for water-filled carbon-fiber reinforced thin plastic pipes. When an impact is introduced to water in a pipe, there are two waves traveling at different speeds. A primary wave corresponding to a breathing mode of pipe travels slowly and a precursor wave corresponding to a longitudinal mode of pipe travels fast. An anisotropic stress-strain relationship of piping materials has been taken into account to describe the propagation of primary and precursor waves in the carbon-fiber reinforced thin plastic pipes. The wave speeds and strains in the axial and hoop directions are calculated as a function of carbon-fiber winding angles and compared with the experimental data. As the winding angle increases, the primary wave speed increases due to the increased stiffness in the hoop direction, while the precursor wave speed decreases. The magnitudes of precursor waves are much smaller than those of primary waves so that the effect of precursor waves on the deformation of pipe is not significant. The primary wave generates the hoop strain accompanying the opposite-signed axial strain through the coupling compliance of pipe. The magnitude of hoop strain induced by the primary waves decreases with increasing the winding angle due to the increased hoop stiffness of pipe. The magnitude of axial strain is small at low and high winding angles where the coupling compliance is small.

You, Jeong Ho; Inaba, K.

2013-01-01

6

Laboratory experimental data is often erroneous. This error is more apparent in data obtained from testing of anisotropic composite materials such as masonry wall  

E-print Network

obtained from testing of anisotropic composite materials such as masonry wall panels. In this paper data colleted from the laboratory tests of masonry panels is presented. Methodologies for reducing (correcting the variation in masonry properties in laterally loaded masonry panels was introduced by Zhou [1] and Rafiq et

Bugmann, Guido

7

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

8

Enhancement of non-resonant dielectric cloaks using anisotropic composites  

SciTech Connect

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

Takezawa, Akihiro, E-mail: akihiro@hiroshima-u.ac.jp; Kitamura, Mitsuru [Division of Mechanical Systems and Applied Mechanics, Institute of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima (Japan)] [Division of Mechanical Systems and Applied Mechanics, Institute of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima (Japan)

2014-01-15

9

Anisotropic fiber alignment in composite structures  

DOEpatents

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

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

1993-01-01

10

Anisotropic fiber alignment in composite structures  

DOEpatents

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

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

1993-11-16

11

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

12

ULTRASONIC CHARACTERIZATION OF ADVANCED COMPOSITE MATERIALS  

Microsoft Academic Search

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

B. Boro Djordjevic

13

Anisotropic linear elastic properties of fractal-like composites  

NASA Astrophysics Data System (ADS)

In this work, the anisotropic linear elastic properties of two-phase composite materials, made up of square inclusions embedded in a matrix, are investigated. The inclusions present a fractal hierarchical distribution and are supposed to have the same Poisson’s ratio as the matrix but a different Young’s modulus. The effective elastic moduli of the medium are computed at each fractal iteration by coupling a position-space renormalization-group technique with a finite element analysis. The study allows to obtain and generalize some fundamental properties of fractal composite materials.

Carpinteri, Alberto; Cornetti, Pietro; Pugno, Nicola; Sapora, Alberto

2010-11-01

14

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

15

Anisotropic magnetostrictive metal-polymer composites for functional devices  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

16

Optimal anisotropic three-phase conducting composites: Plane problem  

E-print Network

The paper establishes tight lower bound for effective conductivity tensor $K_*$ of two-dimensional three-phase conducting anisotropic composites and defines optimal microstructures. It is assumed that three materials are mixed with fixed volume fractions and that the conductivity of one of the materials is infinite. The bound expands the Hashin-Shtrikman and Translation bounds to multiphase structures, it is derived using the technique of {\\em localized polyconvexity} that is a combination of Translation method and additional inequalities on the fields in the materials; similar technique was used by Nesi (1995) and Cherkaev (2009) for isotropic multiphase composites. This paper expands the bounds to the anisotropic composites. The lower bound of conductivity (G-closure) is a piece-wise analytic function of eigenvalues of $K_*$, that depends only on conductivities of components and their volume fractions. Also, we find optimal microstructures that realize the bounds, developing the technique suggested earlier by Albin Cherkaev and Nesi (2007) and Cherkaev (2009). The optimal microstructures are laminates of some rank for all regions. The found structures match the bounds in all but one region of parameters; we discuss the reason for the gap and numerically estimate it.

Andrej Cherkaev; and Yuan Zhang

2010-09-15

17

Aeroelastic tailoring of composite materials  

E-print Network

LIST OF FIGURES IiiTRODUCTI ON ST!!UCTURAL RESPONSE Deformation of Uniformly Stressed Isotropic and Anisotropic Plates Characterization of Composite Laminates . Effect of Material Parameters APPLICATIONS Aircraft Propellers Ship Propell rs... Aircraft Wings and Stabilizers Static Aeroelasticity Dynamic Aeroelasticity . Aeroelastic Tailoring SPECIAL TOPICS The Effects of Time, Tc?. perature, iio'. sture and Fa!:ic!ue Time Dependent Behavior Fatigue Residual Stresses Due to the Cure Cycle...

Rogers, Jesse Byron

2012-06-07

18

Ultrasonic assembly of anisotropic short fibre reinforced composites.  

PubMed

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

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

2014-04-01

19

Constitutive modeling of inelastic anisotropic material response  

NASA Technical Reports Server (NTRS)

A constitutive equation was developed to predict the inelastic thermomechanical response of single crystal turbine blades. These equations are essential for developing accurate finite element models of hot section components and contribute significantly to the understanding and prediction of crack initiation and propagation. The method used was limited to unified state variable constitutive equations. Two approaches to developing an anisotropic constitutive equation were reviewed. One approach was to apply the Stouffer-Bodner representation for deformation induced anisotropy to materials with an initial anisotropy such as single crystals. The second approach was to determine the global inelastic strain rate from the contribution of the slip in each of the possible crystallographic slip systems. A three dimensional finite element is being developed with a variable constitutive equation link that can be used for constitutive equation development and to predict the response of an experiment using the actual specimen geometry and loading conditions.

Stouffer, D. C.

1984-01-01

20

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

21

Composite structural materials  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

22

Anisotropic microporous supports impregnated with polymeric ion-exchange materials  

DOEpatents

Novel ion-exchange media are disclosed, the media comprising polymeric anisotropic microporous supports containing polymeric ion-exchange or ion-complexing materials. The supports are anisotropic, having small exterior pores and larger interior pores, and are preferably in the form of beads, fibers and sheets.

Friesen, Dwayne (Bend, OR); Babcock, Walter C. (Bend, OR); Tuttle, Mark (Bend, OR)

1985-05-07

23

Anisotropic microporous supports impregnated with polymeric ion-exchange materials  

DOEpatents

Novel ion-exchange media are disclosed, the media comprising polymeric anisotropic microporous supports containing polymeric ion-exchange or ion-complexing materials. The supports are anisotropic, having small exterior pores and larger interior pores, and are preferably in the form of beads, fibers and sheets. 5 figs.

Friesen, D.; Babcock, W.C.; Tuttle, M.

1985-05-07

24

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

25

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

26

Modeling failure of soft anisotropic materials with application to arteries.  

PubMed

The arterial wall is a composite where the preferred orientation of collagen fibers induces anisotropy. Though the hyperelastic theories of fiber-reinforced composites reached a high level of sophistication and showed a reasonable correspondence with the available experimental data they are short of the failure description. Following the tradition of strength of materials the failure criteria are usually separated from stress analysis. In the present work we incorporate a failure description in the hyperelastic models of soft anisotropic materials by introducing energy limiters in the strain energy functions. The limiters provide the saturation value for the strain energy which indicates the maximum energy that can be stored and dissipated by an infinitesimal material volume. By using some popular constitutive models enhanced with the energy limiters we analyze rupture of a sheet of arterial material under the plane stress state varying from the uniaxial to equal biaxial tension. We calculate the local failure criteria including the maximum principal stress, the maximum principal stretch, the von Mises stress, and the strain energy at the moment of the sheet rupture. We find that the local failure criterion in the form of the critical strain energy is the most robust among the considered ones. We also find that the tensile strength-the maximum principal stress-that is usually obtained in uniaxial tension tests might not be appropriate as a failure indicator in the cases of the developed biaxiality of the stress-strain state. PMID:22098860

Volokh, K Y

2011-11-01

27

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

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 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

29

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

30

Electrically conductive composite material  

DOEpatents

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

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

1988-06-20

31

Investigation of Porosity Evolution and Orthotropic Axes on Anisotropic Materials  

NASA Astrophysics Data System (ADS)

Advancement of porosities that happens in shear deformation of anisotropic materials is investigated by Dr. Kweon. As the hydrostatic stress in shear deformation is zero, in the solid mechanics' researches it is proved several times that porosity will not be expanded in shear deformation. Dr. Kweon showed that this statement can be wrong in large deformation of simple shear. He proposed anisotropic ductile fracture model to show that hydrostatic stress becomes nonzero and porosities are increased in the simple shear deformation of anisotropic materials. This study investigates the effect of the evolution of anisotropy which means the rotation of the orthotropic axes onto the porosity changes. Hill coefficient shows that how orthotropic materials indicate different ductile fracture manners in shear deformation. Also the effect of void aspect ratio on change of porosity is investigated. It has been found that the interaction among porosity, the matrix anisotropy and void aspect ratio play a crucial role in the ductile damage of porous materials.

Rahimi, Raheleh Mohammad

32

MATERIAL VOIDS IN ELASTIC SOLIDS WITH ANISOTROPIC SURFACE ENERGIES  

E-print Network

MATERIAL VOIDS IN ELASTIC SOLIDS WITH ANISOTROPIC SURFACE ENERGIES Irene Fonseca, Nicola Fusco energy for problems involving a material void in a linearly elastic solid. Using the calculus of variations it is shown that the qualitative features of the equilibrium shape of the void demonstrate

33

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

34

Group velocity of cylindrical guided waves in anisotropic laminate composites.  

PubMed

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

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

2014-01-01

35

Direct composite restorative materials.  

PubMed

Composite dental restorative materials have advanced considerably over the past 10 years. Although composites have not totally replaced amalgam, they have become a viable substitute in many situations. Problems still exist with polymerization contraction stress, large differences in the coefficient of thermal expansion (CTE) of composites compared with tooth structure, and with some technique sensitivity; however, new expanding resins, nanofiller technology, and improved bonding systems have the potential to reduce these problems. With increased patient demands for esthetic restorations, the use of direct filling composite materials will continue to grow. The one major caveat to this prediction is that clinicians must continue to use sound judgment on when, where, and how to use composite restoratives in their practices. PMID:17586149

Puckett, Aaron D; Fitchie, James G; Kirk, Pia Chaterjee; Gamblin, Jefferson

2007-07-01

36

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

37

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

38

Material Transfer of Composite Contact Materials  

Microsoft Academic Search

Composite technology provides very promising possibilities of improving one property of a given material without changing the other for the worse. The material transfer behavior of some fiber composite materials like AgNi and CuPd has been studied. Fiber composite contact materials can be fabricated in a simple and thus inexpensive way by bundling and simultaneous deformation of clad wires. It

HANS H. KOCHER; D. Stockel

1979-01-01

39

ANISOTROPIC MESH ADAPTATION FOR CRACK DETECTION IN BRITTLE MATERIALS  

E-print Network

FORNASIER STEFANO MICHELETTI , AND SIMONA PEROTTO Abstract. The quasistatic brittle fracture model proposed of the most advocated models for quasistatic brittle fracture evolution was first presented by G. FrancfortANISOTROPIC MESH ADAPTATION FOR CRACK DETECTION IN BRITTLE MATERIALS MARCO ARTINA , MASSIMO

Cremers, Daniel

40

Composite materials: Testing and design  

NASA Technical Reports Server (NTRS)

The present conference discusses topics in the analysis of composite structures, composite materials' impact and compression behavior, composite materials characterization methods, composite failure mechanisms, NDE methods for composites, and filament-wound and woven composite materials' fabrication. Attention is given to the automated design of a composite plate for damage tolerance, the effects of adhesive layers on composite laminate impact damage, instability-related delamination growth in thermoset and thermoplastic composites, a simple shear fatigue test for unidirectional E-glass epoxy, the growth of elliptic delaminations in laminates under cyclic transverse shear, and the mechanical behavior of braided composite materials.

Whitcomb, John D. (editor)

1988-01-01

41

Tough composite materials: Recent developments  

SciTech Connect

A series of studies on tough composite materials is presented in this book. These composite materials are strong, but lightweight; and they are being used as metal replacements in applications where weight reduction is important. The material covered here provides an overview of NASA and other research aimed at improving composite material performance and increasing the understanding of composite material behavior. The book covers composite fracture toughness and impact characterization, constituent properties and interrelationships, matrix synthesis and characterization, and selected additional subjects.

Not Available

1985-01-01

42

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

43

Composite electric contact materials  

NASA Astrophysics Data System (ADS)

Two-phase composite materials, i.e., a high-melting component combined with a material exhibiting good electrical and thermal properties find a wide range of application for the manufacture of small- and medium-load relays and switches. Composite contacts can be used in air circuit-breakers (W-Ag, Ag-Ni), oil circuit-breakers (W-Cu, Mo-Cn), vacuum-type switches (W-CuSb, CuCr), and also switches operating in an atmosphere of SF sub 6 (W-Cu). Present-day trends aimed at increasing operating reliability and extending the service life of electrical equipment are finding their expression in efforts being made to modify the classical composites with a veiw to imparting new properties to them by suitably changing their composition and structure. These trends are also aimed at reducing the consumption of noble metals and of strategically important ones. Modern materials engineering and metallurgical technologies are being used, including isostatic sintering or explosive forming. Owing to the high activity of the constituents, all processes are conducted under high vacuum or in pure reducing atmospheres.

Senkara, J.; Kowalczyk, J.

1985-12-01

44

Advanced composite materials and processes  

NASA Technical Reports Server (NTRS)

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

Baucom, Robert M.

1991-01-01

45

Models of two level systems for anisotropic glassy materials  

NASA Astrophysics Data System (ADS)

We use an extended version of the standard tunneling model to explain the sound absorption in anisotropic glassy materials and heat transport in mesoscopic slabs and bridges. The glassy properties are determined by an ensemble of two level systems (TLS). In our model a TLS is characterized by a 3x3 symmetric tensor, [T], which couples to the strain field, [S], through a 3x3x3x3 tensor of coupling constants, [[R

Anghel, Dragos-Victor; Dumitru, Irina Mihaela; Nemnes, Alexandru George; Churochkin, Dmitrii

2013-03-01

46

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

PubMed

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

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

2014-10-21

47

Short courses in Composite Materials  

E-print Network

manufacturing techniques will continue to advance mechanical design. The influence of these technologies such advanced materials is the change in process and behaviours required to design and manufacture composites to composite materials technology, or indeed individuals who would like to understand how composite materials

Davies, John N.

48

Rectangular waveguide material characterization: anisotropic property extraction and measurement validation  

NASA Astrophysics Data System (ADS)

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

Crowgey, Benjamin Reid

49

Forced wave propagation and energy distribution in anisotropic laminate composites.  

PubMed

Elastodynamic response of anisotropic laminate composite structures subjected to a force loading is evaluated based on the integral representations in terms of Green's matrices. Explicit and asymptotic expressions for guided waves generated by a given source are then obtained from those integrals by means of series expansions and the residue technique. Unlike to conventional modal expansions, such representations keep information about the source, giving an opportunity for a quantitative near- and far-field analysis of generated waves. An effective computer implementation is achieved by the use of fast and stable algorithms for the Green matrix, pole, and residue calculations. The potential of the model is demonstrated by examples of anisotropy manifestation in the directivity of radiated waves. The effect of main energy outflow in the direction of either upper- or inner-ply orientation depending on the source size and frequency is discussed. PMID:21568395

Glushkov, Evgeny; Glushkova, Natalia; Eremin, Artem

2011-05-01

50

Processing composite materials  

NASA Technical Reports Server (NTRS)

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

Baucom, R. M.

1982-01-01

51

Analysis and interpretation of diffraction data from complex, anisotropic materials  

NASA Astrophysics Data System (ADS)

Most materials are elastically anisotropic and exhibit additional anisotropy beyond elastic deformation. For instance, in ferroelectric materials the main inelastic deformation mode is via domains, which are highly anisotropic crystallographic features. To quantify this anisotropy of ferroelectrics, advanced X-ray and neutron diffraction methods were employed. Extensive sets of data were collected from tetragonal BaTiO3, PZT and other ferroelectric ceramics. Data analysis was challenging due to the complex constitutive behavior of these materials. To quantify the elastic strain and texture evolution in ferroelectrics under loading, a number of data analysis techniques such as the single peak and Rietveld methods were used and their advantages and disadvantages compared. It was observed that the single peak analysis fails at low peak intensities especially after domain switching while the Rietveld method does not account for lattice strain anisotropy although it overcomes the low intensity problem via whole pattern analysis. To better account for strain anisotropy the constant stress (Reuss) approximation was employed within the Rietveld method and new formulations to estimate lattice strain were proposed. Along the way, new approaches for handling highly anisotropic lattice strain data were also developed and applied. All of the ceramics studied exhibited significant changes in their crystallographic texture after loading indicating non-180° domain switching. For a full interpretation of domain switching the spherical harmonics method was employed in Rietveld. A procedure for simultaneous refinement of multiple data sets was established for a complete texture analysis. To further interpret diffraction data, a solid mechanics model based on the self-consistent approach was used in calculating lattice strain and texture evolution during the loading of a polycrystalline ferroelectric. The model estimates both the macroscopic average response of a specimen and its hkl-dependent lattice strains for different reflections. It also tracks the number of grains (or domains) contributing to each reflection and allows for domain switching. The agreement between the model and experimental data was found to be satisfactory.

Tutuncu, Goknur

52

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

53

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.

54

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

Microsoft Academic Search

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

Bulent Yesilata; Paki Turgut

2007-01-01

55

Reactive liquid crystal materials for optically anisotropic patterned retarders  

NASA Astrophysics Data System (ADS)

Merck has developed a range of reactive liquid crystal materials (Reactive Mesogens) that are designed to form thin, birefringent, coatable films for optical applications. Reactive Mesogen (RM) films are typically coated from solution and polymerized in-situ to form thin, optics-grade coatings. Merck RM materials are customized formulations including reactive liquid crystals, surfactants, photoinitiators and other proprietary additives. Merck have optimized the materials to achieve the optimum physical performance in each application. In this paper we focus on the optimization of RM materials to achieve the finest patterning resolution and defined feature shape whilst maintaining good physical properties of the films. Several conventional trade-offs are investigated and circumvented using novel material concepts. Different methods of patterning RM materials are discussed and the merits of each considered. Thermal annealing of non-polymerized regions can create isotropic islands within the polymerized anisotropic matrix. Alternatively, the non polymerized material can be re-dissolved in the coating solvent and rinsed away. Each of these techniques has benefits depending on the processing conditions and these are discussed in depth.

Harding, Richard; Gardiner, Iain; Yoon, Hyun-Jin; Perrett, Tara; Parri, Owain; Skjonnemand, Karl

2008-11-01

56

Wave Motion 33 (2001) 97107 Elastic waves in inhomogeneously oriented anisotropic materials  

E-print Network

Wave Motion 33 (2001) 97­107 Elastic waves in inhomogeneously oriented anisotropic materials A for elastic waves propagating in inhomogeneously oriented anisotropic solids. These are materials of uniform and wave velocity directions. The general theory is demonstrated for the case of SH waves in a transversely

Norris, Andrew

57

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

58

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

59

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

60

Soft magnetic composite materials (SMCs)  

Microsoft Academic Search

Soft magnetic composites (SMCs), which are used in electromagnetic applications, can be described as ferromagnetic powder particles surrounded by an electrical insulating film. SMC components are normally manufactured by conventional PM compaction combined with new techniques, such as two step compaction, warm compaction, multi-step and magnetic annealing followed by a heat treatment at relatively low temperature. These composite materials offer

H. Shokrollahi; K. Janghorban

2007-01-01

61

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.

62

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

63

Dynamic response of anisotropic composite panels to time-dependent external excitations  

NASA Technical Reports Server (NTRS)

This paper deals with the dynamic response of anisotropic laminated composite flat panels exposed to sonic boom and explosive blast-type loadings. The pertinent governing equations incorporating transverse shear deformation, transverse normal stress, the higher order effects as well as the viscous structural damping are solved by using the integral-transform technique. The obtained results are compared with their counterparts obtained within the framework of the first order transverse shear deformation and the classical plate theories and some conclusions concerning their range of applicability are outlined. The paper also contains a detailed analysis of the influence played by the various parameters characterizing the considered pressure pulses as well as the material and geometry of the plate.

Librescu, L.; Nosier, A.

1990-01-01

64

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

65

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

NASA Astrophysics Data System (ADS)

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.

Frénet, D.; Calmon, P.; Paradis, L.; Ouaftouh, M.

1999-12-01

66

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

67

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

68

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

69

On the theory of conductivity of anisotropic composites: Lattice model  

NASA Astrophysics Data System (ADS)

The electrical conductivity in a disordered anisotropic lattice model is considered using analytic methods. The effective conductivity of a weakly heterogeneous lattice in an approximation quadratic in the deviation of the local conductivity tensor ( r) from its mean value <> is determined. In the case of a low concentration ( c ? 1) of "defective" bonds, the conductivity in the binary lattice model is calculated in an approximation linear in c. The equations of the effective medium method are derived for an anisotropic lattice. The results are compared with the relevant results for the continuum model.

Balagurov, B. Ya.

2014-10-01

70

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

71

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

72

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

73

Predicting Properties Of Composite Materials  

NASA Technical Reports Server (NTRS)

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

Naik, Rajiv A.

1994-01-01

74

Isotropic behavior of an anisotropic material: single crystal silicon  

NASA Astrophysics Data System (ADS)

Zero defect single crystal silicon (Single-Crystal Si), with its diamond cubic crystal structure, is completely isotropic in most properties important for advanced aerospace systems. This paper will identify behavior of the three most dominant planes of the Single-Crystal Si cube (110), (100) and (111). For example, thermal and optical properties are completely isotropic for any given plane. The elastic and mechanical properties however are direction dependent. But we show through finite element analysis that in spite of this, near-isotropic behavior can be achieved with component designs that utilize the optimum elastic modulus in directions with the highest loads. Using glass frit bonding to assemble these planes is the only bonding agent that doesn't degrade the performance of Single-Crystal Si. The most significant anisotropic property of Single-Crystal Si is the Young's modulus of elasticity. Literature values vary substantially around a value of 145 GPa. The truth is that while the maximum modulus is 185 GPa, the most useful <110< crystallographic direction has a high 169 GPa, still higher than that of many materials such as aluminum and invar. And since Poisson's ratio in this direction is an extremely low 0.064, distortion in the plane normal to the load is insignificant. While the minimum modulus is 130 GPa, a calculated average value is close to the optimum at approximately 160 GPa. The minimum modulus is therefore almost irrelevant. The (111) plane, referred to as the natural cleave plane survives impact that would overload the (110) and/or (100) plane due to its superior density. While mechanical properties vary from plane to plane each plane is uniform and response is predictable. Understanding the Single-Crystal Si diamond cube provides a design and manufacture path for building lightweight Single-Crystal Si systems with near-isotropic response to loads. It is clear then that near-isotropic elastic behavior is achievable in Single-Crystal Si components and will provide subsecond thermal equilibrium and sub-micron creep.

McCarter, Douglas R.; Paquin, Roger A.

2013-09-01

75

Manufacture of colloidal polymer ellipsoids for anisotropic conducting nano-composites  

Microsoft Academic Search

This project aimed to make anisotropic conducting nano-composites based on a segregated system of 20 nm gold particles and deformed polyethylene spheres of colloidal size. Two methods for achieving the deformation of the colloidal polyethylene spheres were attempted, namely to exploit the elongational flow field at the entrance to a capillary and alternatively to make cast films of a water

L. Gabrielson; M. J. Folkes

2001-01-01

76

Selective modal control of composite piezolaminated anisotropic shells  

NASA Astrophysics Data System (ADS)

A general Selective Modal Control (SMC) design methodology is presented for piezolaminated anisotropic shell systems which utilizes Selective Modal Transducers (SMT's) recently developed by the authors for piezo-shells in order to realize any number of possible modal control strategies. An SMC design procedure is specified which defines a step-by- step framework through which structural and control sub- design processes are effectively integrated. Several conditions which sufficiently ensure asymptotic stability are derived and then discussed in the context of deriving SMC methods which are stability robust to modeling and implementation errors. Several SMC examples are then given in which SMT's are designed and control laws chosen so as to allow for (1) the contributions of any given mode to the active energy extraction rate to be directly specified, (2) pole locations to be selectively and dynamically varied, or else (3) both pole locations and SMT design constants to be optimally determined. A numerical example is presented in which a stability-robust optimal SMC method is developed for a cantilevered anisotropic cylindrical shell panel. Maintaining a linear feedback law, a single self-sensing SMT is employed whose design parameters were chosen so as to optimize the system response to a given initial excitation. Frequency and transient response analyses show a dramatic enhancement in system performance and accurately concur with theoretical predictions. The example serves both to illustrate the design process and to independently validate SMT and SMC theoretical results as applied to shell systems characterized by zero-Gaussian curvatures.

Miller, Scott E.; Oshman, Yaakov; Abramovich, Haim

1998-07-01

77

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

E-print Network

Bulk anisotropic composite rare earth magnets D. Lee,a S. Bauser, A. Higgins, C. Chen,b and S. Liuc.5Ga0.5B6/Fe­Co magnets show microstructures consisting of a very large soft phase up to 50 m, which is present in a composite Nd2Fe14B/ -Fe magnet alloy. Rather, a free -Fe phase is present. Repeated

Laughlin, David E.

78

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

79

Anisotropic Effective Thermal Conductivity Measurement of Various Kinds of Metal Fiber Materials  

NASA Astrophysics Data System (ADS)

Recently, metal fiber materials were made by laminating metal fibers with a diameter of about 30 ?m to 300 ?m. Since the almost metal fibers were oriented in the horizontal direction (the major axis of the fiber), these metal fiber materials are estimated to be anisotropic with an effective thermal conductivity. However, there is little quantitative data on the anisotropic effective thermal conductivity of the various kinds of metal fiber materials. The purpose of this study is to investigate the anisotropic effective thermal conductivity of various metal fiber materials experimentally and theoretically. In order to measure the horizontal and vertical effective thermal conductivities of these metal fiber materials, new measurement devices were developed. As a result, it is found that the anisotropic effective thermal conductivity of the various metal fiber materials was confirmed, and the horizontal and vertical effective thermal conductivities of these metal fiber materials depend on the bulk density or porosity, Young's modulus, the fiber length, and fiber diameter. And a dimensionless correlation equation for predicting the vertical and horizontal effective thermal conductivities of the various kinds of metal fiber materials was derived in terms of various dimensionless parameters.

Haruki, Naoto; Horibe, Akihiko; Nakashima, Keigo

2013-12-01

80

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

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

81

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

82

Integral kernels in the 2D Somigliana displacement and stress identities for anisotropic materials  

NASA Astrophysics Data System (ADS)

The theory of the direct and indirect formulations of the Somigliana displacement and stress identities for anisotropic materials subjected to generalized plane strain deformations is revised and rounded off. By making use of the powerful Stroh formalism of anisotropic elasticity, explicit and compact formulae of all integral kernels appearing in these identities are derived and relations between these kernels are analysed. Somigliana stress identity is derived directly from the Betti theorem of reciprocity of work using the singularity source of a dislocation dipole (i.e. a kind of eigenstrain nucleus or concentrated initial strain). Explicit formula of the hypersingular integral kernel in the Somigliana stress identity reveals that this kernel is fully symmetrical with respect to index permutation when only in-plane components are considered. Finally, some comments on the applications of the results presented in the stress analysis of anisotropic materials by collocation BEM and Symmetric Galerkin BEM are presented.

Manti?, V.; París, F.

83

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

84

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

Microsoft Academic Search

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

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

2005-01-01

85

Electrical stress and inception voltage of discharges in gaseous cavities in an anisotropic dielectric material  

Microsoft Academic Search

The electric field stress and the inception voltage of discharges in a gaseous void present in an anisotropic dielectric material is developed from the solution of the Laplace equation. The relevant equations for the determination of the electric field and the inception voltage of discharges in voids are presented in a format that can be readily used. The electric field

M. M. A. Salama; M. S. Rizk; R. Hackam

1986-01-01

86

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

87

Composite materials for space structures  

NASA Technical Reports Server (NTRS)

The use of advanced composites for space structures is reviewed. Barriers likely to limit further applications of composites are discussed and highlights of research to improve composites are presented. Developments in composites technology which could impact spacecraft systems are reviewed to identify technology needs and opportunities.

Tenney, D. R.; Sykes, G. F.; Bowles, D. E.

1985-01-01

88

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

89

Recent advances in modeling discontinuities in anisotropic and heterogeneous materials in eddy current NDE  

SciTech Connect

Recent advances are presented to model discontinuities in random anisotropies that arise in certain materials, such as titanium alloys. A numerical model is developed to provide a full anisotropic representation of each crystalline in a gridded region of the material. Several simulated and experimental demonstrations are presented highlighting the effect of grain noise on eddy current measurements. Agreement between VIC-3D(c) model calculations and experimental data in titanium alloy specimens with known flaws is demonstrated.

Aldrin, John C. [Computational Tools, Gurnee, IL 60031 (United States); Sabbagh, Harold A.; Murphy, R. Kim; Sabbagh, Elias H. [Victor Technologies LLC, Bloomington, IN 47401 (United States)

2011-06-23

90

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

91

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

92

Composite materials in dynamic shipboard structural mounts  

E-print Network

The purpose of this thesis is to investigate the viability of replacing traditional metal structural and machinery mounts with padding made of composite material. The two types of padding or isolation materials are represented ...

Faulk, Joanna (Joanna E.)

2011-01-01

93

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

NASA Technical Reports Server (NTRS)

The purpose is to develop life prediction models for coated anisotropic materials used in gas temperature airfoils. Two single crystal alloys and two coatings are now being tested. These include PWA 1480; Alloy 185; overlay coating, PWA 286; and aluminide coating, PWA 273. Constitutive models are also being developed for these materials to predict the plastic and creep strain histories of the materials in the lab tests and for actual design conditions. This nonlinear material behavior is particularily important for high temperature gas turbine applications and is basic to any life prediction system.

Swanson, G. A.

1985-01-01

94

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

95

Damage and fracture mechanics of composite materials  

Microsoft Academic Search

The design of structural systems in the aerospace industry has been characterized by a continuing search for strong, yet lightweight, materials to achieve maximum payload capability for minimum weight. In recent years, this search has led to a wide use of fiber reinforced composites, such as carbon, glass and kevelar based composites. Comparison of these new materials with the traditional

Saleh Ramadan Abdussalam

1999-01-01

96

Hysteresis losses in soft magnetic composite materials  

Microsoft Academic Search

Purpose – To analyze the Jiles and Atherton hysteresis model used for hysteresis losses estimation in soft magnetic composite (SMC) material. Design\\/methodology\\/approach – The Jiles and Atherton hysteresis model parameters are optimized with genetic algorithms (GAs) according to measured symmetric hysteresis loop of soft magnetic composite material. To overcome the uncertainty, finding the best-optimized parameters in a wide predefined searching

Bogomir Zidari?; Mykhaylo Zagirnyak; Konrad Lenasi; Damijan Miljavec

2006-01-01

97

Composite materials and method of making  

DOEpatents

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

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

2011-05-17

98

Ultrasonic Inspection Of Composite-Material Paraboloid  

NASA Technical Reports Server (NTRS)

Ultrasonic imaging system scanning three-dimensional curved surfaces developed. In original application, system used to determine integrity of composite-material paraboloidal reflector and its supporting structure. System also used to inspect composite-material structures with curved surfaces other than paraboloids, provided surfaces describable by mathematical functions. Position and orientation of transducer adjusted continuously to maintain normal incidence.

Chern, E. James

1994-01-01

99

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

100

Electric-field distribution near current contacts of anisotropic materials  

NASA Astrophysics Data System (ADS)

We have measured the nonuniformity of the electric field near lateral current contacts of the charge-density-wave materials NbSe3 and o-TaS3. In this contact geometry, the electric field increases considerably near a current contact. Fitting our data to an existing model yields values for the conduction anisotropy and a characteristic longitudinal length scale. This length scale is on the same order as the mesoscopic phenomena in charge-density-wave devices.

Slot, E.; van der Zant, H. S.; Thorne, R. E.

2002-01-01

101

Composite materials for biomedical applications: a review.  

PubMed

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

Salernitano, E; Migliaresi, C

2003-01-01

102

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

103

A new method for calculation of elastic properties of anisotropic material by constant pressure molecular dynamics  

Microsoft Academic Search

A new method based on constant pressure molecular dynamics (MD) with the software package Materials Studio (MS) was developed to calculate the anisotropic elastic properties of 1,3,5-tri-amino-2,4,6-tri-nitrobenzene (TATB) which is a typical and widely studied explosive molecular and its single crystal is a typical triclinic lattice. Key points of the method are introduced. Firstly, a P1 periodic super cell of

Kailiang Yin; Dinghui Zou; Jing Zhong; Duanjun Xu

2007-01-01

104

Flame-retardant composite materials  

NASA Technical Reports Server (NTRS)

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

Kourtides, Demetrius A.

1991-01-01

105

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

106

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

107

Ceramic composites: Enabling aerospace materials  

NASA Technical Reports Server (NTRS)

Ceramics and ceramic matrix composites (CMC) have the potential for significant impact on the performance of aerospace propulsion and power systems. In this paper, the potential benefits are discussed in broad qualitative terms and are illustrated by some specific application case studies. The key issues in need of resolution for the potential of ceramics to be realized are discussed.

Levine, S. R.

1992-01-01

108

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

109

Manufacturing technology of the composite materials: nanocrystalline material - polymer type  

Microsoft Academic Search

Purpose: This paper presents the material and technological solution which makes it possible to obtain the nanocrystalline, ferromagnetic powder material of Fe73.5Cu1Nb3Si13.5B9 alloy after its thermal nanocrystallization with the succeeding high-energy milling. Another aspect was to develop the technology to obtain the nanocrystalline composite materials made by binding the obtained powder material with the high density low- pressures polyethylene (PEHD)

B. Zi?bowicz; D. Szewieczek; L. A. Dobrza?ski

110

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

111

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

112

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

113

Acoustic emission monitoring of polymer composite materials  

NASA Technical Reports Server (NTRS)

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

Bardenheier, R.

1981-01-01

114

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

115

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

116

Method to fabricate layered material compositions  

DOEpatents

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

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

2002-01-01

117

Development and characterization of renewable resource- structural composite materials  

E-print Network

Cannabis sativa as reinforcement/filler of thermoplastic composite materials." Composites Part A: Applied ScienceCannabis sativa as reinforcement/filler of thermoplastic composite materials." Composites Part A: Applied Science

Cutter, Andrea Gillian

2008-01-01

118

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

119

Measurement of anisotropic fracture energies in periodic templated silica/polymer composite coatings  

NASA Astrophysics Data System (ADS)

We report measurements of the fracture energies of hexagonal honeycomb structured silica/polymer composite films that were produced through an evaporation induced self-assembly process. These films exhibit large anisotropy with their hexagonal pore axes aligned with the dip-coating direction. The experimental strategy included depositing films onto a flexible Kapton substrate and then straining them, in situ, under a microscope. To study the effect of the anisotropic microstructure on the fracture energy, cracks were propagated both parallel and perpendicular to the cylindrical pore axis directions. For both cases, the geometries of the evolving crack patterns with loading were micrographically recorded and the desired energy release rates were calculated using a two-dimensional steady-state channeling crack model. The model was implemented using the ANSYS finite element program. The experimental observations showed significant inelastic film deformation prior to crack propagation. These deformations were fully captured in the model, with properties obtained directly from the experiments. The calculated energy release rates were 12.3±0.5 J/m2 for the parallel direction and 6.7±0.5 J/m2 for the perpendicular direction. These numbers are significantly larger than the bulk silica value of roughly 4 J/m2, indicating the role of the local nanostructure in blunting and deflecting the crack tips. Experimental validation of the highly anisotropic energy release rates was obtained through transmission electron microscopy images of fractured films.

Chen, X.; Richman, E. K.; Kirsch, B. L.; Senter, R.; Tolbert, S. H.; Gupta, V.

2008-10-01

120

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

121

ENG 4793: Composite Materials and Processes 1 Compression Molding  

E-print Network

1 ENG 4793: Composite Materials and Processes 1 Compression Molding ver 2 ENG 4793: Composite and Processes 4 Schematic of a Compression Molding Press ENG 4793: Composite Materials and Processes 5 Matched Die Mold ENG 4793: Composite Materials and Processes 6 #12;2 ENG 4793: Composite Materials

Colton, Jonathan S.

122

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

123

Size-dependent effective properties of anisotropic piezoelectric composites with piezoelectric nano-particles  

NASA Astrophysics Data System (ADS)

Based on the electro-elastic surface/interface theory, the size-dependent effective piezoelectric and dielectric coefficients of anisotropic piezoelectric composites that consist of spherically piezoelectric inclusions under a uniform electric field are investigated, and the analytical solutions for the elastic displacement and electric potentials are derived. With consideration of the coupling effects of elasticity, permittivity and piezoelectricity, the effective field method is introduced to derive the effective dielectric and piezoelectric responses in the dilute limit. The numerical examples show that the effective dielectric constant exhibits a significant variation due to the surface/interface effect. The dielectric property of the surface/interface displays greater effect than the piezoelectric property, and the elastic property shows little effect. A comparison with the existing results validates the present approach.

Huang, Ming-Juan; Fang, Xue-Qian; Liu, Jin-Xi; Feng, Wen-Jie; Zhao, Yong-Mao

2015-01-01

124

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

125

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

126

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

127

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

128

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

129

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

130

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

131

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

NASA Astrophysics Data System (ADS)

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

Xia, Fengnian; Wang, Han; Jia, Yichen

2014-07-01

132

On upper and lower limits of elastic coefficients of SMC composite materials  

E-print Network

Abstract:- The aim of the paper is to present an original homogenization method for elliptic equations applied to pre-impregnated composite materials, known as prepregs. In this class of prepregs can be included Sheetand Bulk Molding Compounds. Sheet Molding Compounds (SMC) are characterized, in general, as multiphase heterogeneous and anisotropic composite materials with randomly discontinuous reinforcement. The upper and lower limits of the homogenized coefficients for a 27 % fiber volume fraction SMC are computed. It is presented a comparison between the upper and lower limits of the homogenized elastic coefficients of a SMC material and the experimental data. The computing model used as a homogenization method of these heterogeneous composite materials, gave emphasis to a good agreement between this method and experimental data.

Horatiu Teodorescu; Violeta Munteanu; Anca Stanciu; Ramona Purcarea

133

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

134

Grafting in cellulose - polystyrene composite materials  

SciTech Connect

In order to evaluate the effect of the grafting of polystyrene on model cellulosic fibers, several composite materials were processed, (1) by simply dispersing microfibrils into a polystyrene matrix, (2) by dispersing the same fibers but modified by phenyl groups, (3) by grafting a functionalized polystyrene on the fibers surface and mixing with the matrix. The characterization of the coupling agent used has been performed by several techniques: FTIR, NMR, DSC and elemental analysis. Evidence of grafting onto the fibers surface was displayed by FTIR measurements and elemental analysis. All the composite materials were characterized by DSC, tensile tests and mechanical spectroscopy.

Trejo O`Reilly, J.A.; Cavaille, J.Y.; Dufresne, A. [CERMAV-CNRS, Grenoble (France)] [and others

1995-12-01

135

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

136

Composite material characterization for large space structures.  

NASA Technical Reports Server (NTRS)

A program phase to characterize advanced composite materials for a large reflector support truss on the ATS F & G spacecraft is described. The selection of a Hercules Incorporated, 2002M graphite fiber reinforced epoxy material was based on criteria of spacecraft system requirements and the potential of this material to meet these requirements. The objective of this phase was to develop materials data required for development, design, fabrication, test, and flight of a graphite-fiber, reinforced-plastic spacecraft structure. Testing within a temperature range from -300 F to +200 F covered the generation of data for physical, mechanical, thermophysical, and space environmental properties for the selected material. Additional testing covered adhesive bonded joint materials within the temperature ranges of the spacecraft environment. Descriptions of the spacecraft, reflector support truss, design, requirements, materials, tests, and developed data are presented.

Macneill, C. E.

1972-01-01

137

Ground exposure of composite materials for helicopters  

NASA Technical Reports Server (NTRS)

Residual strength results are presented on four composite material systems that were exposed for three years at locations on the North American Continent. The exposure locations are near the areas where Bell Model 206L Helicopters, that are in a NSA/U.S. Army sponsored flight service program, are flying in daily commercial service. The composite systems are: (1) Kevlar-49 fabric/F-185 epoxy; (2) Kevlar-49 fabric/LRF-277 epoxy; (3) Kevlar-49 fabric/CE-306 epoxy; and (4) T-300 Graphite/E-788 epoxy. All material systems exhibited good strength retention in compression and short beam shear. The Kevlar-49/LRF-277 epoxy retained 88 to 93 percent of the baseline strength while the other material systems exceeded 95 percent of baseline strength. Residual tensile strength of all materials did not show a significant reduction. The available moisture absorption data is also presented.

Baker, D. J.

1984-01-01

138

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

139

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

140

Synthesizing Smart Polymeric and Composite Materials  

NASA Astrophysics Data System (ADS)

Smart materials have been widely investigated to explore new functionalities unavailable to traditional materials or to mimic the multifunctionality of biological systems. Synthetic polymers are particularly attractive as they already possess some of the attributes required for smart materials, and there are vast room to further enhance the existing properties or impart new properties by polymer synthesis or composite formulation. In this work, three types of smart polymer and composites have been investigated with important new applications: (1) healable polymer composites for structural application and healable composite conductor for electronic device application; (2) conducting polymer polypyrrole actuator for implantable medical device application; and (3) ferroelectric polymer and ceramic nanoparticles composites for electrocaloric effect based solid state refrigeration application. These application entail highly challenging materials innovation, and my work has led to significant progress in all three areas. For the healable polymer composites, well known intrinsically healable polymer 2MEP4F (a Diels-Alder crosslinked polymer formed from a monomer with four furan groups and another monomer with two maleimide groups) was first chosen as the matrix reinforced with fiber. Glass fibers were successfully functionalized with maleimide functional groups on their surface. Composites from functionalized glass fibers and 2MEP4F healable polymer were made to compare with composites made from commercial carbon fibers and 2MEP4F polymer. Dramatically improved short beam shear strength was obtained from composite of functionalized glass fibers and 2MEP4F polymer. The high cost of 2MEP4F polymer can potentially limit the large-scale application of the developed healable composite, we further developed a new healable polymer with much lower cost. This new polymer was formed through the Diels-Alder crosslinking of poly(furfuryl alcohol) (PFA) and 1,1'-(Methylenedi-4,1-phenylene)bismaleimide (MDPB). It showed the same healing ability as 2MEP4F while all starting materials are cheaper and commercially available. To further improve the mechanical strength of the PFA-MDPB healable polymer, epoxy as a strengthening component was mixed with PFA-MDPB healable polymer. The PFA, MDPB and epoxy composite polymers were further reinforced by carbon fiber as done with 2MEP4F matrix and the final composites were proved to have higher short beam shear strength than 2MEP4F while exhibiting a similar healing efficiency. Healable polymer MDPB (a two maleimide groups monomer) -- FGEEDR (a four furan groups monomer) was also designed and synthesized for transparent healable polymer. The MDPB-FGEEDR healable polymer was composited with silver nanowires (AgNWs) to afford healable transparent composite conductor. Razer blade cuts in the composite conductor could heal upon heating to recover the mechanical strength and electrical conductivity of the composite. The healing could be repeated for multiple times on the same cut location. The healing process was as fast as 3 minutes for conductivity to recover 97% of the original value. For electroactive polymer polypyrrole, the fast volume change upon electrical field change due to electrochemical oxidization or reduction was studied for actuation targeting toward a robotic application. The flexibility of polypyrrole was improved via copolymerization with pyrrole derivatives. Actuator devices are fabricated that more suitable for implantable medical device application than pyrrole homopolymer. The change of dipole re-orientation and thus dielectric constant of ferroelectric polymers and ceramics upon electrical field may be exploited for electrocaloric effect (ECE) and solid state refrigeration. For ferroelectric ceramics, we synthesized a series of Ba1-xSrxTiO3 nanoparticles with diameter ranging from 8-12 nm and characterized their dielectric and ferroelectric properties through hysteresis measurement. It was found that 8 nm BaTiO3 nanocrystals are stable at cubic crystal structure without ferroelectric

Gong, Chaokun

141

Composite materials microstructure for radiation shielding  

NASA Technical Reports Server (NTRS)

Shielding against radiation is a concern for applications on earth, in space, and on extraterrestrial surfaces. On earth EMI is an important factor, while in space and on extraterrestrial surfaces particle (high charge-Z and high energy-E) radiation is a critical issue. Conventional metallic materials currently used for EMI shielding incur large weight penalties. To overcome this weight penalty, ultra-lightweight composite materials utilizing fillers ranging from carbon microballoons to silver coated ceramic microballoons are proposed. The crucial shielding requirement is conductivity of the constituent materials, while the hollow microballoon geometry is utilized to yield low weight. Methods of processing and composition effects are examined and these results are compared to the effectiveness of varying the conductive microballoon material. The resulting ultralightweight materials, developed for EMI shielding, can be tailored through the application of the understanding of the relative effects of variables such as those tested. Initial experimental results reveal that these tailored ultralightweight composite materials are superior to traditional aluminum shielding at only a small fraction of the weight.

Radford, Donald W.; Sadeh, Willy Z.; Cheng, Boyle C.

1992-01-01

142

Composite materials for rail transit systems  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

143

Composite materials for precision space reflector panels  

NASA Astrophysics Data System (ADS)

One of the critical technology needs of large precision reflectors for future astrophysical and optical communications satellites lies in the area of structural materials. Results from a materials research and development program at NASA Langley Research Center to provide materials for these reflector applications are discussed. Advanced materials that meet the reflector panel requirements are identified and thermal, mechanical and durability properties of candidate materials after exposure to simulated space environments are compared. Results from analytical studies to define material properties that control laminate properties and reflector deformation are discussed. A parabolic, graphite-phenolic honeycomb composite panel having a surface accuracy of 70.8 microinches RMS and an areal weight of 1.17 lbm/ft2 was fabricated with T50/ERL1962 facesheets, a PAEI thermoplastic surface film, and Al and SiOx coatings.

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

1992-09-01

144

Thermoplastic Composite Materials for Aerospace Applications  

NASA Astrophysics Data System (ADS)

Mechanical and thermo-physical properties of composites materials with thermoplastic matrix (PEEK/IM7, TPI/IM7 and PPS/IM7) used for aerospace applications have been analyzed as function of two different process techniques: compression molding and fiber placement process "hot gas assisted."

Casula, G.; Lenzi, F.; Vitiello, C.

2008-08-01

145

Soft magnetic composites-materials and applications  

Microsoft Academic Search

The group of soft magnetic composites (SMCs) have expanded by the introduction of new materials with significantly improved low-medium frequency properties, which has made SMCs a viable alternative to steel laminations in a range of new applications, such as rotating machinery, sensors and fast switching solenoids. SMC components are successfully manufactured using the powder metallurgy compaction process. The isotropic nature

L. O. Hultman; A. G. Jack

2003-01-01

146

Silicon nitride reinforced nickel alloy composite materials  

Microsoft Academic Search

An erosion resistant composite material is described comprising silicon nitride rod reinforced nickel alloy, where the silicon nitride is cold pressed and sintered and substantially nonreactive with the alloy at high temperatures. The silicon nitride can either be polycrystalline or amorphous containing alumina, 15% yttria and about 2% to about 5% silica. Three to 8% alumina is used in the

F. S. Galasso; R. D. Veltri

1985-01-01

147

Satellite surface material composition from synthetic spectra  

NASA Astrophysics Data System (ADS)

The objective of this research was to determine if measurements from a Sagnac interferometer could provide reliable estimates of satellite material composition. The Sagnac interferometer yields a spatial interferogram that can be sampled by a linear detector array. The interferogram is related to the spectrum of the source through a Fourier transform. Here, spectral reflectivities of nine common satellite materials were used to simulate the spectrum on obtains from an ideal Sagnac interferometer in the beam-train of a ground-based telescope whose mission is to view satellites. The signal-to-noise ratio of the spectrum was varied to simulate the effect of range variation between the sensor and the satellite. The simulated spectra consisted of a linear mixture of spectra from two of the nine materials. Three different architectures were developed and their performances compared. One of the three architectures consisted of nine artificial neural networks (ANN's), one for each material, and a linear estimator that estimated the satellite surface area attributable to each material. This method estimates the material composition by using a classifier to identify the materials contributing to the mixture, then eliminating unlikely contributors to the mixture before performing a constrained linear estimate. It is shown that due to high classification errors, the system using solely a linear estimator provides the estimate with the lowest errors.

Caudill, Eugene L.

1994-12-01

148

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

149

Composite materials for precision space reflector panels  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

150

Material Model Evaluation of a Composite Honeycomb Energy Absorber  

NASA Technical Reports Server (NTRS)

A study was conducted to evaluate four different material models in predicting the dynamic crushing response of solid-element-based models of a composite honeycomb energy absorber, designated the Deployable Energy Absorber (DEA). Dynamic crush tests of three DEA components were simulated using the nonlinear, explicit transient dynamic code, LS-DYNA . In addition, a full-scale crash test of an MD-500 helicopter, retrofitted with DEA blocks, was simulated. The four material models used to represent the DEA included: *MAT_CRUSHABLE_FOAM (Mat 63), *MAT_HONEYCOMB (Mat 26), *MAT_SIMPLIFIED_RUBBER/FOAM (Mat 181), and *MAT_TRANSVERSELY_ANISOTROPIC_CRUSHABLE_FOAM (Mat 142). Test-analysis calibration metrics included simple percentage error comparisons of initial peak acceleration, sustained crush stress, and peak compaction acceleration of the DEA components. In addition, the Roadside Safety Verification and Validation Program (RSVVP) was used to assess similarities and differences between the experimental and analytical curves for the full-scale crash test.

Jackson, Karen E.; Annett, Martin S.; Fasanella, Edwin L.; Polanco, Michael A.

2012-01-01

151

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

152

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

153

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 · Ejection force · Design rules ENG 4793: Composite Materials and Processes 3 Equipment Clamp Mold Hopper screw nozzle clamp mold cavity pellets motor / drive throat #12;2 ENG 4793: Composite Materials

Colton, Jonathan S.

154

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

155

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

156

Multiaxial analysis of dental composite materials.  

PubMed

Dental composites are subjected to extreme chemical and mechanical conditions in the oral environment, contributing to the degradation and ultimate failure of the material in vivo. The objective of this study is to validate an alternative method of mechanically loading dental composite materials. Confined compression testing more closely represents the complex loading that dental restorations experience in the oral cavity. Dental composites, a nanofilled and a hybrid microfilled, were prepared as cylindrical specimens, light-cured in ring molds of 6061 aluminum, with the ends polished to ensure parallel surfaces. The samples were subjected to confined compression loading to 3, 6, 9, 12, and 15% axial strain. Upon loading, the ring constrains radial expansion of the specimen, generating confinement stresses. A strain gage placed on the outer wall of the aluminum confining ring records hoop strain. Assuming plane stress conditions, the confining stress (sigma(c)) can be calculated at the sample/ring interface. Following mechanical loading, tomographic data was generated using a high-resolution microtomography system developed at beamline 2-BM of the Advanced Photon Source at Argonne National Laboratory. Extraction of the crack and void surfaces present in the material bulk is numerically represented as crack edge/volume (CE/V), and calculated as a fraction of total specimen volume. Initial results indicate that as the strain level increases the CE/V increases. Analysis of the composite specimens under different mechanical loads suggests that microtomography is a useful tool for three-dimensional evaluation of dental composite fracture surfaces. PMID:18506811

Kotche, Miiri; Drummond, James L; Sun, Kang; Vural, Murat; DeCarlo, Francesco

2009-02-01

157

Aromatic acetylenes for carbon matrix composite material  

SciTech Connect

Carbon composite materials are being used increasingly in aerospace structures because of the high strength to weight ratio of such materials. Acetylenic substituted aromatic compounds, which have low melting points, can be easily processed, lose little weight during their curing, and do not need multiple impregnations to achieve high density, are good candidates as carbon precursor materials. In this laboratory, the compound 1,2,4,5-tetrakis(phenylethynyl)benzene 1 was prepared by the palladium catalyzed reaction of phenylacetylene with 1,2,4,5-tetrabromobenzene in the presence of excess amine base. Laboratory studies have shown that 1 melts at 195{degrees}C and forms a thermosetting material with high thermal and oxidative stability and a high char yield upon pyrolysis under nitrogen. Changes which occurred upon pyrolysis in air were studied by infrared spectroscopy. The monomer 1 is a crystalline solid that is stable indefinitely at room temperature.

Jones, K.M.; Keller, T.M. [Naval Research Lab., Washington, DC (United States)

1993-12-31

158

NDE of polymeric composite material bridge components  

NASA Astrophysics Data System (ADS)

Rapid advancements with respect to utilization of polymeric composite materials for bridge components is occurring. This situation is driven primarily by the potential improvements offered by these materials with respect to long term durability. However, because of the developmental nature of these materials much of the materials characterization has involved short term testing without the synergistic effects of environmental exposure. Efforts to develop nondestructive evaluation procedures, essential for any wide spread use in critical structural applications, have been consequently limited. This paper discuses the effort to develop NDE methods for field inspection of hybrid glass and carbon fiber reinforced vinyl ester pultruded 'double box' I beams that are installed in a small bridge over Tom's Creek, in Blacksburg, Virginia. Integrated structural element sensors, dormant infrared devices, as well as acousto-ultrasonic methods are under development for detecting and monitoring the occurrence and progression of life limiting deterioration mechanisms.

Duke, John C., Jr.; Horne, Michael R.

1998-03-01

159

Using Composite Materials in a Cryogenic Pump  

NASA Technical Reports Server (NTRS)

Several modifications have been made to the design and operation of an extended-shaft cryogenic pump to increase the efficiency of pumping. In general, the efficiency of pumping a cryogenic fluid is limited by thermal losses which is itself caused by pump inefficiency and leakage of heat through the pump structure. A typical cryogenic pump includes a drive shaft and two main concentric static components (an outer pressure containment tube and an intermediate static support tube) made from stainless steel. The modifications made include replacement of the stainless-steel drive shaft and the concentric static stainless-steel components with components made of a glass/epoxy composite. The leakage of heat is thus reduced because the thermal conductivity of the composite is an order of magnitude below that of stainless steel. Taking advantage of the margin afforded by the decrease in thermal conductivity, the drive shaft could be shortened to increase its effective stiffness, thereby increasing the rotordynamic critical speeds, thereby further making it possible to operate the pump at a higher speed to increase pumping efficiency. During the modification effort, an analysis revealed that substitution of the shorter glass/epoxy shaft for the longer stainless-steel shaft was not, by itself, sufficient to satisfy the rotordynamic requirements at the desired increased speed. Hence, it became necessary to increase the stiffness of the composite shaft. This stiffening was accomplished by means of a carbon-fiber-composite overwrap along most of the length of the shaft. Concomitantly with the modifications described thus far, it was necessary to provide for joining the composite-material components with metallic components required by different aspects of the pump design. An adhesive material formulated specially to bond the composite and metal components was chosen as a means to satisfy these requirements.

Batton, William D.; Dillard, James E.; Rottmund, Matthew E.; Tupper, Michael L.; Mallick, Kaushik; Francis, William H.

2008-01-01

160

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

NASA Astrophysics Data System (ADS)

Based on joint consideration of S receiver functions and surface-wave anisotropy we present evidence for the existence of a thick and layered lithosphere beneath the Kalahari Craton. 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. Significant correlation between the depths of an apparent boundary separating the depleted and metasomatised lithosphere, as inferred from chemical tomography, and those of our second MLD led us to characterize it as a compositional boundary, most likely due to the modification of the cratonic mantle lithosphere by magma infiltration. The deepening of this boundary from 150 to 200 km is spatially correlated with the surficial expression of the Thabazimbi-Murchison Lineament (TML), implying that the TML isolates the lithosphere of the Limpopo terrane from that of the ancient Kaapvaal terrane. 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 most likely represents the lithosphere-asthenosphere boundary, which shallows to about 200 km beneath the younger Proterozoic belt. Thus, the Kalahari lithosphere may have survived multiple episodes of intense magmatism and collisional rifting during the billions of years of its history, which left their imprint in its internal layering.

Sodoudi, Forough; Yuan, Xiaohui; Kind, Rainer; Lebedev, Sergei; Adam, Joanne M.-C.; Kästle, Emanuel; Tilmann, Frederik

2013-12-01

161

Metal Matrix Composite Materials for Aerospace Applications  

NASA Technical Reports Server (NTRS)

Metal matrix composites (MMC) are attractive materials for aerospace applications because of their high specific strength, high specific stiffness, and lower thermal expansion coefficient. They are affordable since complex parts can be produced by low cost casting process. As a result there are many commercial and Department of Defense applications of MMCs today. This seminar will give an overview of MMCs and their state-of-the-art technology assessment. Topics to be covered are types of MMCs, fabrication methods, product forms, applications, and material selection issues for design and manufacture. Some examples of current and future aerospace applications will also be presented and discussed.

Bhat, Biliyar N.; Jones, C. S. (Technical Monitor)

2001-01-01

162

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

163

A new approach for modeling composite materials  

NASA Astrophysics Data System (ADS)

The increasing use of composite materials is due to their ability to tailor materials for special purposes, with applications evolving day by day. This is why predicting the properties of these systems from their constituents, or phases, has become so important. However, assigning macroscopical optical properties for these materials from the bulk properties of their constituents is not a straightforward task. In this research, we present a spectral analysis of three-dimensional random composite typical nanostructures using an Extension of the Discrete Dipole Approximation (E-DDA code), comparing different approaches and emphasizing the influences of optical properties of constituents and their concentration. In particular, we hypothesize a new approach that preserves the individual nature of the constituents introducing at the same time a variation in the optical properties of each discrete element that is driven by the surrounding medium. The results obtained with this new approach compare more favorably with the experiment than previous ones. We have also applied it to a non-conventional material composed of a metamaterial embedded in a dielectric matrix. Our version of the Discrete Dipole Approximation code, the EDDA code, has been formulated specifically to tackle this kind of problem, including materials with either magnetic and tensor properties.

Alcaraz de la Osa, R.; Moreno, F.; Saiz, J. M.

2013-03-01

164

Test Plan for Composite Hydrogen Getter Materials  

Microsoft Academic Search

The intent of this test plan is to provide details of the Savannah River Technology Center (SRTC) effort to evaluate composite getter materials for eventual use in expanding the wattage limits for transportation of contact-handled transuranic waste (CH-TRU). This effort is funded by the Mixed Waste Focus Area (MWFA) under Technical Task Plan (TTP) SR-1-9-MW-45 and is the result of

2000-01-01

165

Machine augmented composite materials for damping purposes  

E-print Network

???????........??...27 4. INVESTIGATION OF FLUID FLOW IN AND INTERACTION WITH TUBES EMBEDDED IN A MATRIX............................................................38 4.1 Modeling of Sealed Tubes Embedded in an Elastomer Matrix??....??..38.... On the other hand, common elastomers possess good damping characteristics and low density, but they have relatively low stiffness and strength. Conventional composite materials have large stiffness to density ratios, but many lack good damping properties...

McCutcheon, David Matthew

2005-02-17

166

Silicon nitride reinforced nickel alloy composite materials  

SciTech Connect

An erosion resistant composite material is described comprising silicon nitride rod reinforced nickel alloy, where the silicon nitride is cold pressed and sintered and substantially nonreactive with the alloy at high temperatures. The silicon nitride can either be polycrystalline or amorphous containing alumina, 15% yttria and about 2% to about 5% silica. Three to 8% alumina is used in the case of polycrystalline silicon nitride and 2% to 6% alumina is used in the case of amorphous silicon nitride.

Galasso, F. S.; Veltri, R. D.

1985-10-29

167

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

168

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

169

Local buckling of wide-flange thin-walled anisotropic composite beams  

Microsoft Academic Search

The present contribution deals with the onset of local buckling of compressively loaded thin-walled beams with open I, C,\\u000a Z, T and L-cross-sections made of laminated composite materials. The method employs a discrete plate analysis approach in\\u000a the course of which each structural subelement of interest—which presently is the flange—of the thin-walled cross-section\\u000a is considered as a separate composite plate

Christian Mittelstedt

2007-01-01

170

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

171

A Generalized Anisotropic Hardening Rule Based on the Mroz Multi-Yield-Surface Model for Pressure Insensitive and Sensitive Materials  

SciTech Connect

In this paper, a generalized anisotropic hardening rule based on the Mroz multi-yield-surface model is derived. The evolution equation for the active yield surface is obtained by considering the continuous expansion of the active yield surface during the unloading/reloading process. The incremental constitutive relation based on the associated flow rule is then derived for a general yield function. As a special case, detailed incremental constitutive relations are derived for the Mises yield function. The closed-form solutions for one-dimensional stress-plastic strain curves are also derived and plotted for the Mises materials under cyclic loading conditions. The stress-plastic strain curves show closed hysteresis loops under uniaxial cyclic loading conditions and the Masing hypothesis is applicable. A user material subroutine based on the Mises yield function, the anisotropic hardening rule and the constitutive relations was then written and implemented into ABAQUS. Computations were conducted for a simple plane strain finite element model under uniaxial monotonic and cyclic loading conditions based on the anisotropic hardening rule and the isotropic and nonlinear kinematic hardening rules of ABAQUS. The results indicate that the plastic response of the material follows the intended input stress-strain data for the anisotropic hardening rule whereas the plastic response depends upon the input strain ranges of the stress-strain data for the nonlinear kinematic hardening rule.

Choi, Kyoo Sil; Pan, Jwo

2009-07-27

172

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

173

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

174

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

175

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

176

Active composite materials as sensing elements for fiber-reinforced smart composite structures  

Microsoft Academic Search

Polymer based piezoelectric composite materials can be readily integrated within laminated composite structures to provide sensing and actuating capabilities. In this study composite films of ferroelectric ceramic\\/polymer materials have been developed and characterized as in-situ multi purpose sensing elements for the nondestructive monitoring of fiber reinforced composites. In this paper the response of embedded composite films to simulated acoustic emission

Panagiotis Blanas; Matthew P. Wenger; Elias J. Rigas; Dilip K. Das-Gupta

1998-01-01

177

Glasses, ceramics, and composites from lunar materials  

NASA Technical Reports Server (NTRS)

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.

1992-01-01

178

Recycling technologies for thermoset composite materials—current status  

Microsoft Academic Search

The technologies for recycling thermoset composite materials are reviewed. Mechanical recycling techniques involve the use of grinding techniques to comminute the scrap material and produce recyclate products in different size ranges suitable for reuse as fillers or partial reinforcement in new composite material. Thermal recycling processes involve the use of heat to break the scrap composite down and a range

S. J. Pickering

2006-01-01

179

Composite materials for thermal energy storage  

DOEpatents

A 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 PCM's 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, D.K.; Burrows, R.W.; Shinton, Y.D.

1985-01-04

180

Estimating Weibull parameters for composite materials.  

NASA Technical Reports Server (NTRS)

This paper deals with the statistical analysis of strength and fracture of materials in general, with application to fiber composites. The 'weakest link' model is considered in a fairly general form, and the resulting equations are demonstrated by using a Weibull distribution for flaws. This distribution appears naturally in a variety of problems, and therefore additional attention is devoted to analysis and statistical estimation connected with this distribution. Special working charts are included to facilitate interpretation of observed data and estimation of parameters. Implications of the size effect are considered for various kinds of flaw distributions. The paper describes failure and damage in a fiber-reinforced systems.

Robinson, E. Y.

1972-01-01

181

Composite materials flown on the Long Duration Exposure Facility  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

182

Composite and diamond cold cathode materials  

SciTech Connect

Cold-cathode technology for Crossed-Field Amplifiers (CFAs) has not changed significantly over the last thirty years. The material typically used for cold cathode CFAs is either platinum (Pt) or beryllium (Be), although numerous other materials with higher secondary electron emission ratios have been tested. Beryllium cathodes display higher secondary emission ratios, {approximately} 3.4, than Pt, but require a partial pressure of oxygen to maintain a beryllium oxide (BeO) surface layer. These dispensers limit the life of the CFA, both directly, due to oxygen-source filament burnout, and indirectly, by the production of undesirable gases which adversely affect the performance of the CFA. In an attempt to reduce or eliminate the required oxygen dispenser output level, cathodes were constructed from three varieties of Be/BeO composite material and tested in L-4808s, standard forward-wave AEGIS CFAs. Diamond and diamond-like carbons are desirable as cathode materials because of their extremely high secondary electron emission ratio, greater than 20, but their use has previously been prohibitive because of cost, available, and physical characteristics. Because of recent advances in diamond growth technology it is now possible to deposit thin layers of diamond on a variety of geometric objects. In coordination with Penn State University four annular diamond emitters have been fabricated. The diamond emitters will be tested in a standard AEGIS CFA, both under vacuum and with a partial pressure of hydrogen.

Worthington, M.S.; Wheeland, C.L.; Ramacher, K.; Doyle, E. [Litton Systems Inc., Williamsport, PA (United States). Electron Devices Div.

1996-12-31

183

Anisotropic composite human skull model and skull fracture validation against temporo-parietal skull fracture.  

PubMed

A composite material model for skull, taking into account damage is implemented in the Strasbourg University finite element head model (SUFEHM) in order to enhance the existing skull mechanical constitutive law. The skull behavior is validated in terms of fracture patterns and contact forces by reconstructing 15 experimental cases. The new SUFEHM skull model is capable of reproducing skull fracture precisely. The composite skull model is validated not only for maximum forces, but also for lateral impact against actual force time curves from PMHS for the first time. Skull strain energy is found to be a pertinent parameter to predict the skull fracture and based on statistical (binary logistical regression) analysis it is observed that 50% risk of skull fracture occurred at skull strain energy of 544.0mJ. PMID:24055886

Sahoo, Debasis; Deck, Caroline; Yoganandan, Narayan; Willinger, Rémy

2013-12-01

184

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

185

Paramagnetic relaxation in anisotropic materials in zero and weak constant fields  

NASA Astrophysics Data System (ADS)

Paramagnetic relaxation in strongly anisotropic materials is analytically investigated in zero and weak constant magnetic fields. The objectives of the microscopic analytical investigation are (i) the weak-field electron paramagnetic resonance (EPR) linewidth and (ii) the electron spin relaxation rates given by a calorimetric Gorter type experiment in the zero constant field at the arbitrary low-frequency field directions, respectively, to the sample crystallographic axes. The EPR linewidth is calculated under the suggestion of its spin-phonon nature at the one-phonon mechanism of the spin-lattice relaxation in the case of the strong isotropic exchange interaction for the arbitrary direction Z of the constant magnetic field. The EPR linewidth is presented as the half sum of the zero-field relaxation rates, measured by the Gorter experiment with the low-frequency field oriented along the X, Y axes. With the help of the macroscopic consideration, it is shown that the zero-field relaxation rates describe the relaxation of the X and Y magnetization components in a zero or weak constant magnetic field. The relaxation rates of the magnetizations created along a,b,c crystallographic axes by a low-frequency field in a Gorter type experiment follow the obtained expressions in the particular cases and are in the experimentally confirmed relations with the EPR linewidth.

Fokina, N. P.; Khalvashi, E. Kh.; Khutsishvili, K. O.

2014-12-01

186

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

2014-12-18

187

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

SciTech Connect

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

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

2013-09-15

188

Modeling of Anisotropic Damage for Ductile Materials in Metal Forming Processes  

Microsoft Academic Search

The primary goal of this study is to model the anisotropic effect of ductile damage in metal forming processes. To represent the ductile metals, an anisotropic ductile plasticity\\/damage formulation is considered within the framework of continuum mechanics. The formulation is motivated from fracture mechanisms and physical observations in Al–Si–Mg aluminum alloys with second phases. The ductile damage mechanisms are represented

Y. Hammi; D. J. Bammann; M. F. Horstemeyer

2004-01-01

189

Isotopic Compositions of Uranium Reference Materials  

NASA Astrophysics Data System (ADS)

Uranium isotopic compositions of a variety of U standard materials were measured at Lawrence Livermore National Laboratory and are reported here. Both thermal ionization mass spectrometry (TIMS) and multi-collector inductively couple plasma mass spectrometry (MC-ICPMS) were used to determine ratios of the naturally occurring isotopes of U. Establishing an internally coherent set of isotopic values for a range of U standards is essential for inter-laboratory comparison of small differences in 238U/235U, as well as the minor isotopes of U. Differences of ~1.3‰ are now being observed in 238U/235U in natural samples, and may play an important role in understanding U geochemistry where tracing the origin of U is aided by U isotopic compositions. The 238U/235U ratios were measured with a TRITON TIMS using a mixed 233U-236U isotopic tracer to correct for instrument fractionation. This tracer was extremely pure and resulted in only very minor corrections on the measured 238U/235U ratios of ~0.03. The values obtained for 238U/235U are: IRMM184 = 137.698 ± 0.020 (n=15), SRM950a = 137.870 ± 0.018 (n=8), and CRM112a = 137.866 ± 0.030 (n=16). Uncertainties represent 2 s.d. of the population. Our measured value for IRMM184 is in near-perfect agreement with the certified value of 137.697 ± 0.042. However, the U isotopic compositions of SRM950a and CRM112a are not certified. Minor isotopes of U were determined with a Nu Plasma HR MC-ICPMS and mass bias was corrected by sample/standard bracketing to IRMM184, using its certified 238U/235U ratio. Thus, the isotopic compositions determined using both instruments are compatible. The values obtained for 234U/235U are: SRM950a = (7.437 ± 0.043)x10-3 (n=18), and CRM112a = (7.281 ± 0.050)x10-3 (n=16), both of which are in good agreement with published values. The value for 236U/235U in SRM950a was determined to be (8.48 ± 2.63)x10-6, whereas 236U was not detected in CRM112a. We are currently obtaining the U isotopic composition of CRM129a. Preliminary results suggest that the 238U/235U ratio is within error, but slightly lower than the certified value of 137.71.

Jacobsen, B.; Borg, L. E.; Williams, R. W.; Brennecka, G.; Hutcheon, I. D.

2009-12-01

190

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

PubMed Central

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

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

2013-01-01

191

APPLICATION OF ELECTROLESS METAL DEPOSITION FOR ADVANCED COMPOSITE SHIELDING MATERIALS  

Microsoft Academic Search

This paper presents the principles of formation and properties of new fibre composite materials for electromagnetic shields. Composite fibres consist of organic basis and metallic particles formed on surface and in the volume of fibre using electroless deposition technology. Polyacrylonitrile was the main type of fibres material that employed for modification and creation of composite structure. Polymer-like transformation of polyacrylonitrile

V. Bogush

192

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

193

Review on advanced composite materials boring mechanism and tools  

Microsoft Academic Search

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

Runping Shi; Chengyong Wang

2010-01-01

194

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

195

High strain rate effects for composite materials  

SciTech Connect

We have been developing the capability to characterize the high strain rate response of continuous fiber polymer composites. The data presented covers strain rates from 0/sec to 3000/sec. A combination of test machines and specimen geometries was investigated. Strain rates from 0--100/sec were generated using conventional and high speed hydraulic test machines. Strain rates from 10--1000/sec were generated using a high energy drop tower, and rates from 1000--3000/sec were generated using a split Hopkinson bar. Strain rates above 100/sec have only been generated for uniaxial compression. Our efforts have primarily focused on developing the high energy drop tower for these purposes. Specimen geometries for compression include tapered cubes, one inch tubes, and solid rods. For tension a smaller 0.5 in. diameter version of our 2.0 in. diameter multiaxial test specimen was developed and has been successfully used at strain rates up to 100 per second. Fixtures were also developed for performing high strain rate shear testing and through thickness penetration studies of composite plates. The objective of these experiments is to develop dynamic material models for use in finite element design tools. This presentation will focus on the methods and results obtained from this study.

Groves, S.E.; Sanchez, R.J.; Lyon, R.E.; Brown, A.E.

1992-04-16

196

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

197

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

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

198

ISOTOPIC COMPOSITIONS OF URANIUM REFERENCE MATERIALS  

SciTech Connect

Uranium isotopic compositions of a variety of U standard materials were measured at Lawrence Livermore National Laboratory and are reported here. Both thermal ionization mass spectrometry (TIMS) and multi-collector inductively couple plasma mass spectrometry (MC-ICPMS) were used to determine ratios of the naturally occurring isotopes of U. Establishing an internally coherent set of isotopic values for a range of U standards is essential for inter-laboratory comparison of small differences in {sup 238}U/{sup 235}U, as well as the minor isotopes of U. Differences of {approx} 1.3{per_thousand} are now being observed in {sup 238}U/{sup 235}U in natural samples, and may play an important role in understanding U geochemistry where tracing the origin of U is aided by U isotopic compositions. The {sup 238}U/{sup 235}U ratios were measured with a TRITON TIMS using a mixed {sup 233}U-{sup 236}U isotopic tracer to correct for instrument fractionation. this tracer was extremely pure and resulted in only very minor corrections on the measured {sup 238}U/{sup 235}U ratios of {approx} 0.03. The values obtained for {sup 238}U/{sup 235}U are: IRMM184 = 137.698 {+-} 0.020 (n = 15), SRM950a = 137.870 {+-} 0.018 (n = 8), and CRM112a = 137.866 {+-} 0.030 (n = 16). Uncertainties represent 2 s.d. of the population. The measured value for IRMM184 is in near-perfect agreement with the certified value of 137.697 {+-} 0.042. However, the U isotopic compositions of SRM950a and CRM112a are not certified. Minor isotopes of U were determined with a Nu Plasma HR MC-ICPMS and mass bias was corrected by sample/standard bracketing to IRMM184, using its certified {sup 238}U/{sup 235}U ratio. Thus, the isotopic compositions determined using both instruments are compatible. The values obtained for {sup 234}U/{sup 235}U are: SRM950a = (7.437 {+-} 0.043) x 10{sup -3} (n = 18), and CRM112a = (7.281 {+-} 0.050) x 10{sup -3} (n = 16), both of which are in good agreement with published values. The value for {sup 236}U/{sup 235}U in SRM950a was determined to be (8.48 {+-} 2.63) x 10{sup -6}, whereas {sup 236}U was not detected in CRM112a. They are currently obtaining the U isotopic composition of CRM129a. Preliminary results suggest that the {sup 238}U/{sup 235}U ratio is within error, but slightly lower than the certified value of 137.71.

Jacobsen, B; Borg, L; Williams, R; Brennecka, G; Hutcheon, I

2009-09-03

199

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

200

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

201

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

202

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

203

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

204

Controlled intermittent interfacial bond concept for composite materials  

NASA Technical Reports Server (NTRS)

Concept will enhance fracture resistance of high-strength filamentary composite without degrading its tensile strength or elastic modulus. Concept provides more economical composite systems, tailored for specific applications, and composite materials with mechanical properties, such as tensile strength, fracture strain, and fracture toughness, that can be optimized.

Marston, T. U.; Atkins, A. G.

1975-01-01

205

Cytotoxic and mutagenic effects of dental composite materials  

Microsoft Academic Search

Mutagenicity of single compounds of dental resinous materials has been investigated on many occasions before, but the induction of mutagenic effects by extracts of clinically used composites is still unknown. Here, cytotoxic effects and the formation of micronuclei were determined in V79 fibroblasts after exposure to extracts of modern composite filling materials (Solitaire, Solitaire 2, Tetric Ceram, Dyract AP, Definite).

Helmut Schweikl; Karl-Anton Hiller; Carola Bolay; Marion Kreissl; Wetscheslaw Kreismann; Agathe Nusser; Stefanie Steinhauser; Janusz Wieczorek; Rudolf Vasold; Gottfried Schmalz

2005-01-01

206

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

207

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

208

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

209

Characterization of a High Strain Composite Material I. Maqueda  

E-print Network

Characterization of a High Strain Composite Material I. Maqueda and S. Pellegrino California and developed a high-strain composite material consisting of car- bon fibers embedded in a silicone matrix that localize the high-strain capability in narrow regions of a structure, so that elastic fold lines are formed

Pellegrino, Sergio

210

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

211

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

212

Material, process, and product design of thermoplastic composite materials  

NASA Astrophysics Data System (ADS)

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

Dai, Heming

213

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

214

Local Debonding and Fiber Breakage in Composite Materials Modeled Accurately  

NASA Technical Reports Server (NTRS)

A prerequisite for full utilization of composite materials in aerospace components is accurate design and life prediction tools that enable the assessment of component performance and reliability. Such tools assist both structural analysts, who design and optimize structures composed of composite materials, and materials scientists who design and optimize the composite materials themselves. NASA Glenn Research Center's Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC) software package (http://www.grc.nasa.gov/WWW/LPB/mac) addresses this need for composite design and life prediction tools by providing a widely applicable and accurate approach to modeling composite materials. Furthermore, MAC/GMC serves as a platform for incorporating new local models and capabilities that are under development at NASA, thus enabling these new capabilities to progress rapidly to a stage in which they can be employed by the code's end users.

Bednarcyk, Brett A.; Arnold, Steven M.

2001-01-01

215

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

216

Flexible hydrogel-based functional composite materials  

DOEpatents

A composite having a flexible hydrogel polymer formed by mixing an organic phase with an inorganic composition, the organic phase selected from the group consisting of a hydrogel monomer, a crosslinker, a radical initiator, and/or a solvent. A polymerization mixture is formed and polymerized into a desired shape and size.

2013-10-08

217

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

218

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

219

Active composite materials as sensing elements for fiber-reinforced smart composite structures  

NASA Astrophysics Data System (ADS)

Polymer based piezoelectric composite materials can be readily integrated within laminated composite structures to provide sensing and actuating capabilities. In this study composite films of ferroelectric ceramic/polymer materials have been developed and characterized as in-situ multi purpose sensing elements for the nondestructive monitoring of fiber reinforced composites. In this paper the response of embedded composite films to simulated acoustic emission signals will be presented and discussed. Results show the ability of the composite sensors to detect signals from acoustic emission sources over a wide bandwidth.

Blanas, Panagiotis; Wenger, Matthew P.; Rigas, Elias J.; Das-Gupta, Dilip K.

1998-07-01

220

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

221

About composite materials and their use in bone surgery.  

PubMed

Composite materials consist of two or even more different material components or phases, which are combined with the aim to improve physical, mechanical and/or biological properties. Such structures are designed to fulfil very specific requirements with respect to a selected device application making full use of their higher weight-specific strength and/or stiffness. Furthermore, these materials offer an opportunity for constructing radiolucent devices. In medical technology, composite materials mainly consist of a polymer matrix and fibres as a reinforcement phase. Composites similar to those known from technical applications reveal a number of specific biological problems. This is due to the materials and manufacturing processes available for the construction of such composites preventing their unrestricted use in direct bone contact. Nevertheless, an application potential for these materials in bone surgery exists and justifies further research and development efforts. PMID:11270081

Gasser, B

2000-12-01

222

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

223

School of Mechanical and Materials Engineering Composites Materials and Engineering Center  

E-print Network

and manufacturing technologies from a range of recycled and renewable resources. In 2015, CMEC will join other WSU and bio-based composite materials and sustainable manufacturing processes and design; ability to seekSchool of Mechanical and Materials Engineering and Composites Materials and Engineering Center

Collins, Gary S.

224

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

225

Reflection and transmission for layered composite materials  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

226

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

227

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

228

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...

229

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

230

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

231

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

232

LDEF fiber-composite materials characterization  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

233

Processing of materials—monolithic to composites  

Microsoft Academic Search

A multimillion rupee 500-ton hydraulic extrusion\\/forging facility established at NPL, New Delhi, has been used to undertake\\u000a extensive studies in forming, the process of plastically deforming, which is the most important way of shaping materials.\\u000a Wrought materials are used extensively for making useful products employing extrusion and forging, the two important secondary\\u000a processing techniques used to convert materials into useful

Anil K Gupta

1995-01-01

234

Embedded electrode electro-optic composite materials  

NASA Astrophysics Data System (ADS)

We explore new concepts for electro-optic (EO) modulator designs based on local-field enhancement and electrodes in close proximity for improving the performance of nonlinear materials. Using nanopatterned metals or conductive materials for electrodes and plasmonic elements we show that the effective nonlinearity can be enhanced and concurrently the driving voltage reduced for electro-optic active materials. We especially devote our attention on EO modulator applications using polymers doped with active chromophores. Our substrate materials are mesoscopically patterned using focused ion beam milling. The critical dimensions of the features are smaller than a wavelength. The effective medium theory is used to analyze the results.

Nelson, Robert L.; Grote, James G.; Haus, Joseph W.; Birchfield, Brad

2006-08-01

235

Mechanical behaviour of composite materials made by resin film infusion  

NASA Astrophysics Data System (ADS)

Innovative composite materials are frequently used in designing aerospace, naval and automotive components. In the typical structure of composites, multiple layers are stacked together with a particular sequence in order to give specific mechanical properties. Layers are organized with different angles, different sequences and different technological process to obtain a new and innovative material. From the standpoint of engineering designer it is useful to consider the single layer of composite as macroscopically homogeneous material. However, composites are non homogeneous bodies. Moreover, layers are not often perfectly bonded together and delamination often occurs. Other violations of lamination theory hypotheses, such as plane stress and thin material, are not unusual and in many cases the transverse shear flexibility and the thickness-normal stiffness should be considered. Therefore the real behaviour of composite materials is quite different from the predictions coming from the traditional lamination theory. Due to the increasing structural performance required to innovative composites, the knowledge of the mechanical properties for different loading cases is a fundamental source of concern. Experimental characterization of materials and structures in different environmental conditions is extremely important to understand the mechanical behaviour of these new materials. The purpose of the present work is to characterize a composite material developed for aerospace applications and produced by means of the resin film infusion process (RFI). Different tests have been carried out: tensile, open-hole and filled-hole tensile, compressive, openhole and filled-hole compressive. The experimental campaign has the aim to define mechanical characteristics of this RFI composite material in different conditions: environmental temperature, Hot/Wet and Cold.

Barile, C.; Casavola, C.; Pappalettere, C.; Tursi, F.

2010-06-01

236

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

237

Effective pyroelectric response of compositionally graded ferroelectric materials  

E-print Network

in this range often must rely upon expensive cryogenically cooled semiconductor-based technology or utilize high--those materials being compositionally graded ferroelectric thin films formed from either potassium tantalum

Alpay, S. Pamir

238

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

239

Space radiation effects on composite matrix materials - Analytical approaches  

NASA Technical Reports Server (NTRS)

In-vacuo ultraviolet and gamma radiation exposure tests are utilized in a study aimed at the identification of radiation damage mechanisms in composite materials, with the objective of predicting the long-term behavior of composite structures in a space environment at geosynchronous orbit. Physical and chemical methods of polymer characterization are utilized for the study of composite matrix degradation, in conjunction with GC/MS techniques for the analysis of volatile by-products.

Giori, C.

1979-01-01

240

Natural frequency and damping behavior of composite materials  

E-print Network

to gain a data base for static and dynamic response of composite components. This project focuses on the vibration and damping characterization of composites in the presence of damage. The effects of selection of material system, size, stacking... and progressive damage accumulation, may make composites an unattractive choice as an alternative to metals, whereas other characteristics such as vibration behavior provide opportunities to tailor structures effectively. Wave propagation and vibration...

Duggan, Matthew Brace

2012-06-07

241

The Effective Kerr Constant of an Electrooptical Composite Material  

Microsoft Academic Search

A general relationship is derived for the effective Kerr constant of an electrooptical composite material containing nonlinear centrosymmetric dielectric microcrystals; anisotropy of the inclusions and their nonsphericity were taken into account. It is shown that nonsphericity of the particles makes it possible to substantially enhance the Kerr constant of the composite in the case when the glass-matrix permittivity is much

A. A. Berezhnoi; M. I. Vasil'Ev; A. O. Volchek; A. V. Dotsenko; V. A. Tsekhomskii

2002-01-01

242

Joining and fabrication of metal-matrix composite materials  

NASA Technical Reports Server (NTRS)

Manufacturing technology associated with developing fabrication processes to incorporate metal-matrix composites into flight hardware is studied. The joining of composite to itself and to titanium by innovative brazing, diffusion bonding, and adhesive bonding is examined. The effects of the fabrication processes on the material properties and their influence on the design of YF-12 wing panels are discussed.

Royster, D. M.; Wiant, H. R.; Bales, T. T.

1975-01-01

243

Drilling carbon fiber-reinforced composite material at high speed  

Microsoft Academic Search

Increasing cutting speed will reduce machining time and hence improve productivity. Drilling is one of the most important cutting operations which are currently carried out on fiber-reinforced composites. Therefore, it is of interest to study the effects of increasing cutting speed on drilling characteristics of carbon fiber-reinforced composite materials. In this paper, the effects of increasing cutting speed ranging from

S. C. Lin; I. K. Chen

1996-01-01

244

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

245

Semiempirical analysis of materials' elemental composition to formulate tissue-equivalent materials: a preliminary study  

NASA Astrophysics Data System (ADS)

Tissue-equivalent materials are used for simplifying quality control and quality assurance procedures, both in diagnostic and therapeutic radiology. Important information to formulate a tissue-equivalent material is elemental composition of its base materials. However, this information is not easily obtained. Therefore we propose a stoichiometric analysis method to investigate the elemental composition of the base materials that can potentially be used for manufacturing tissue-equivalent materials. In this technique, we combined the stoichiometric calibration and the basic data method to obtain the elemental composition of materials from measured computer tomography (CT) numbers. The elemental composition, with the maximum number of the elements of the material in question up to the available number of different tube voltages at the CT scanner, was analysed using the proposed approach. We tested eight different cylinders in this study. The estimated elemental compositions of unspecified materials in the cylinders were evaluated by comparing the calculated and the simulated CT numbers to the measured ones; the results showed good correlation with maximum absolute differences of 1.9 and 3.7 HU, respectively. The accuracy of the stoichiometric analysis method to estimate the elemental composition was influenced by the accuracy of the measured CT numbers. The method proposed allows for determining the elemental composition of the base materials which can then be applied further to formulate tissue-equivalent materials.

Yohannes, Indra; Kolditz, Daniel; Kalender, Willi A.

2011-05-01

246

Advanced Surface Laminar Circuit using new composite materials  

Microsoft Academic Search

This paper introduces a newly developed Advanced Surface Laminar Circuit (Adv-SLC) packaging technology, which utilizes new composite materials. Adv-SLC is a buildup substrate technology designed to satisfy the requirements of the most advanced semiconductor chips. We have developed a new dielectric material that is a build-up layer composed of two different materials. We also used a new material for the

Katsura Hayashi; Kimihiro Yamanaka; Kaoru Kobayashi; Yoshihiro Hosoi; Masahiro Fukui

2010-01-01

247

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

248

Composite Materials for Radiation Shielding During Deep Space Missions  

NASA Technical Reports Server (NTRS)

Minimizing radiation exposure from the galactic cosmic ray (GCR) environment during deep space missions is essential to human health and sensitive instrument survivability. Given the fabrication constraints of space transportation vehicles protective shielding is, consequently, a complicated materials issue. These concerns are presented and considered in view of some novel composite materials being developed/suggested for GCR shielding applications. Advantages and disadvantages of the composites will be discussed as well as the need for coordinated testing/evaluation and modeling efforts.

Grugel, R. N.; Watts, J.; Adams, J. H.; Rose, M. Franklin (Technical Monitor)

2001-01-01

249

Finite element analysis of composites materials for aerospace applications  

Microsoft Academic Search

Composites materials are intended to be used more extensively as an alternative of aluminum structure in aircraft and aerospace applications. This is due to their attractive properties as high strength-to-weight ratio and stiffness-to-weight ratio. Besides that it clarifies the growing interest for composites materials due to advantages of lightweight, high strength, high stiffness, superior fatigue life, tremendous corrosion resistance and

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

2010-01-01

250

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

251

Statistical analysis and interpolation of compositional data in materials science.  

PubMed

Compositional data are ubiquitous in chemistry and materials science: analysis of elements in multicomponent systems, combinatorial problems, etc., lead to data that are non-negative and sum to a constant (for example, atomic concentrations). The constant sum constraint restricts the sampling space to a simplex instead of the usual Euclidean space. Since statistical measures such as mean and standard deviation are defined for the Euclidean space, traditional correlation studies, multivariate analysis, and hypothesis testing may lead to erroneous dependencies and incorrect inferences when applied to compositional data. Furthermore, composition measurements that are used for data analytics may not include all of the elements contained in the material; that is, the measurements may be subcompositions of a higher-dimensional parent composition. Physically meaningful statistical analysis must yield results that are invariant under the number of composition elements, requiring the application of specialized statistical tools. We present specifics and subtleties of compositional data processing through discussion of illustrative examples. We introduce basic concepts, terminology, and methods required for the analysis of compositional data and utilize them for the spatial interpolation of composition in a sputtered thin film. The results demonstrate the importance of this mathematical framework for compositional data analysis (CDA) in the fields of materials science and chemistry. PMID:25547365

Pesenson, Misha Z; Suram, Santosh K; Gregoire, John M

2015-02-01

252

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

253

High strain rate effects for composite materials  

Microsoft Academic Search

We have been developing the capability to characterize the high strain rate response of continuous fiber polymer composites. The data presented covers strain rates from 0\\/sec to 3000\\/sec. A combination of test machines and specimen geometries was investigated. Strain rates from 0--100\\/sec were generated using conventional and high speed hydraulic test machines. Strain rates from 10--1000\\/sec were generated using a

S. E. Groves; R. J. Sanchez; R. E. Lyon; A. E. Brown

1992-01-01

254

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

255

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

256

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

PubMed Central

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

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

2010-01-01

257

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

258

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

259

Geometry of compressible and incompressible quantum Hall states: Application to anisotropic composite-fermion liquids  

NASA Astrophysics Data System (ADS)

Haldane's geometrical description of fractional quantum Hall states is generalized to compressible states. It is shown that anisotropy in the composite fermion Fermi surface is a direct reflection of this intrinsic geometry. A simple model is introduced in which the geometric parameter can be obtained exactly from other parameters including electron mass anisotropy. Our results compare favorably with recent measurements of anisotropy in composite fermion Fermi surface [Kamburov, Liu, Shayegan, Pfeiffer, West, and Baldwin, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.110.206801 110, 206801 (2013)]. Broader implications of our results are discussed.

Yang, Kun

2013-12-01

260

The development of composite materials for spacecraft precision reflector panels  

NASA Technical Reports Server (NTRS)

One of the critical technology needs for large precision reflectors required for future astrophysics and optical communications is in the area of structural materials. Therefore, a major area of the Precision Segmented Reflector Program at NASA is to develop lightweight composite reflector panels with durable, space environmentally stable materials which maintain both surface figure and required surface accuracy necessary for space telescope applications. Results from the materials research and development program at NASA Langley Research Center are discussed. Advanced materials that meet the reflector panel requirements are identified. Thermal, mechanical and durability properties of candidate materials after exposure to simulated space environments are compared to the baseline material.

Tompkins, Stephen S.; Bowles, David E.; Funk, Joan G.; Towell, Timothy W.; Lavoie, J. A.

1990-01-01

261

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

262

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

263

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

264

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

265

Investigation of Lamb elastic waves in anisotropic multilayered composites applying the Green's matrix.  

PubMed

This article presents a numerical study of dispersion characteristics of some symmetric and antisymmetric composites modelled as multilayered packets of layers with arbitrary anisotropy of each layer. The authors introduce a subsidiary boundary problem of three-dimensional elasticity theory for the system of partial differential equations describing the harmonic oscillations of the composite caused by a surface load. The problem reduces to a boundary problem for ordinary differential equations by employing the Fourier transform. An algorithm of constructing the Fourier transform of the Green's matrix of the given boundary problem is presented. The wave numbers of Lamb waves propagating in composites, their phase velocity surfaces and group wave surfaces are presented through the poles of the transform of the Green's matrix. The authors obtain the dispersion curves for different directions and frequencies and investigate the dispersion curves and surfaces of wave numbers, phase velocities and group wave surfaces for various composites. The numerical results are then compared with the results obtained by applying other methods. PMID:20580389

Karmazin, Alexander; Kirillova, Evgenia; Seemann, Wolfgang; Syromyatnikov, Pavel

2011-01-01

266

Composite resins. A review of the materials and clinical indications.  

PubMed

The aim of this work is to present the different components of the composites currently used in dentistry and furnish dentists with a basis that can provide criteria for choosing one or another to suit their therapeutic requirements. Most composites used in dentistry are hybrid materials, so-called because they are composed of polymer groups reinforced by an inorganic phase of glass fillers with different compositions, particle sizes and fill percentages. Flowable or condensable composites have attempted to provide an answer to certain functional requirements, although they have not been too successful at improving properties. Turning to polymerisation initiators, both halogen lamps, whether conventional or high intensity, and LED curing lights which provide a gradual increase in light intensity are very useful for reducing shrinkage of the composite material. The clinical choice of a composite must consider whether priority should be given to mechanical or aesthetic requirements: if mechanical considerations are paramount the material with the greatest volume of filler will be chosen; if aesthetic considerations predominate, particle size will be the most important factor. Additional components such as opaques and tints make it possible to improve the aesthetic results. Equally, the spread of other therapeutic procedures, such as tooth bleaching, has made it necessary to design composite materials in shades that are suitable for the special colour situations found in teeth treated by these methods. PMID:16505805

Hervás-García, Adela; Martínez-Lozano, Miguel Angel; Cabanes-Vila, Jose; Barjau-Escribano, Amaya; Fos-Galve, Pablo

2006-03-01

267

Electrospun Nanofiber Coating of Fiber Materials: A Composite Toughening Approach  

NASA Technical Reports Server (NTRS)

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

Kohlman, Lee W.; Roberts, Gary D.

2012-01-01

268

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

269

Cell attachment to hydrogel-electrospun fiber mat composite materials.  

PubMed

Hydrogels, electrospun fiber mats (EFMs), and their composites have been extensively studied for tissue engineering because of their physical and chemical similarity to native biological systems. However, while chemically similar, hydrogels and electrospun fiber mats display very different topographical features. Here, we examine the influence of surface topography and composition of hydrogels, EFMs, and hydrogel-EFM composites on cell behavior. Materials studied were composed of synthetic poly(ethylene glycol) (PEG) and poly(ethylene glycol)-poly(?-caprolactone) (PEGPCL) hydrogels and electrospun poly(caprolactone) (PCL) and core/shell PCL/PEGPCL constituent materials. The number of adherent cells and cell circularity were most strongly influenced by the fibrous nature of materials (e.g., topography), whereas cell spreading was more strongly influenced by material composition (e.g., chemistry). These results suggest that cell attachment and proliferation to hydrogel-EFM composites can be tuned by varying these properties to provide important insights for the future design of such composite materials. PMID:24955629

Han, Ning; Johnson, Jed K; Bradley, Patrick A; Parikh, Kunal S; Lannutti, John J; Winter, Jessica O

2012-01-01

270

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

271

3D Magnetic Reluctivity Tensor of Soft Magnetic Composite Material  

Microsoft Academic Search

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

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

2006-01-01

272

Composite Material Property Nondestructive Characterization Using Obliquely Insonified Ultrasonic Waves  

NASA Technical Reports Server (NTRS)

The analysis of reflected ultrasonic waves induced by oblique insonification of composite materials is a powerful tool for providing informations about defects and material properties. A device was developed to manipulate a pair of transmitting and receiving transducers at vrious angles of wave incidence and propagation with the fiber orientation.

Bar-Cohen, Y.; Mal, A. K.; Lih, S.

1994-01-01

273

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

274

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

275

Workshop on Scaling Effects in Composite Materials and Structures  

NASA Technical Reports Server (NTRS)

This document contains presentations and abstracts from the Workshop on Scaling Effects in Composite Materials and Structures jointly sponsored by NASA Langley Research Center, Virginia Tech, and the Institute for Mechanics and Materials at the University of California, San Diego, and held at NASA Langley on November 15-16, 1993. Workshop attendees represented NASA, other government research labs, the aircraft/rotorcraft industry, and academia. The workshop objectives were to assess the state-of-technology in scaling effects in composite materials and to provide guidelines for future research.

Jackson, Karen E. (compiler)

1994-01-01

276

Materials Science and Technology Teacher's Handbook: Experiments/Demonstrations: Composites  

NSDL National Science Digital Library

This chapter from the Materials Science and Technology Teacher's Handbook provides experiments and demonstrations involving composites that can be used in a materials science and technology curriculum. These experiments are "designed to grab studentsâ attention, pull their minds from predictable everyday classroom activities, give them something to look forward to, and teach them some simple principles and properties used by materials scientists." Experiments include Making Concrete, Simple Stressed-Skin Composite, Airfoils, and Making Paper. Drawings and diagrams help illustrate the concepts. This document will serve as a framework for instructors and may be downloaded in PDF format.

2012-10-05

277

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

278

Probing disease-related proteins with fluorogenic composite materials.  

PubMed

Construction of composite materials based on the self-assembly of fluorescently labeled biomolecules with a variety of micro- or nano-quenching materials (by the Förster Resonance Energy Transfer mechanism) for the fluorogenic recognition of disease-related proteins has become a dynamic research topic in the field of fluorescence recognition. Here we summarize the recent progress on the composition of fluorescence dye-labeled biomolecules including sugars, peptides and nucleotides with organic (graphene and carbon nanotubes) and inorganic (gold nanoparticles) materials. Their application in the fluorescence detection of proteins and enzymes on both the molecular and cellular levels is discussed. Perspectives are proposed with respect to the future directions of employing these composite materials in the recognition of pathological proteins. PMID:25474366

He, Xiao-Peng; Zang, Yi; James, Tony D; Li, Jia; Chen, Guo-Rong

2014-12-01

279

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

280

Measurement of Damping of Composite Materials for Turbomachinery Applications  

NASA Technical Reports Server (NTRS)

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

Harris, D. L.

1998-01-01

281

Molecular interactions in inorganic-organic composite materials  

NASA Astrophysics Data System (ADS)

Inorganic-organic interactions play a key role in determining the molecular and macroscopic properties of resulting composites. These materials have a wide variety of applications including use as catalysts, hosts for optical and electronic applications, and as adsorbents. Tailoring composites for each unique application is accomplished using local interactions between inorganic and organic species to control both local and mesoscopic ordering. For many inorganic-organic composites, no local order exists thereby inhibiting local characterization of these materials using diffraction techniques. However, using NMR methods that are not dependent upon periodicity, unique insight about inorganic-organic interactions in locally amorphous materials can be achieved. Using solid-state NMR methods, inorganic-organic interactions have been utilized to unambiguously establish the local organization of a variety of mesoporous materials as well as provide insight into the biological processes controlling biomineralization. For example, such experiments have revealed the location and coordination of aluminum species in the aluminosilicate framework of mesoporous materials. Such findings are crucial for the preparation of advanced catalytically active materials. These techniques have also provided increase understanding of the formation process of the inorganic network and have lead to the synthesis of the first mesophase material with a 2D crystalline architecture. This discovery is promising for enhancing the thermal and mechanical strength of mesoporous catalysts that had previously been locally disordered and thermally unstable. These investigations provide a wealth of knowledge for understanding the influence organic molecules exert upon silica structures and can be utilized to provide advanced, tailored composites.

Christiansen, Sean Condon

282

Anisotropic elasticity and abnormal Poisson's ratios in super-hard materials  

NASA Astrophysics Data System (ADS)

We theoretically investigated the variable mechanical properties such as Young's modulus, Poisson's ratios and compressibility in super-hard materials. Our tensorial analysis reveals that the mechanical properties of super-hard materials are strongly sensitive to the anisotropy index of materials. In sharp contrast to the traditional positive constant as thought before, the Poisson's ratio of super-hard materials could be unexpectedly negative, zero, or even positive with a value much larger than the isotropic upper limit of 0.5 along definite directions. Our results uncover a correlation between compressibility and hardness, which offer insights on the prediction of new super-hard materials.

Huang, Chuanwei; Li, Rongpeng; Chen, Lang

2014-12-01

283

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

284

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

285

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

286

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

287

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

PubMed

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

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

2012-08-01

288

Mesoporous MFI zeolite material from silica–alumina\\/epoxy-resin composite material and its catalytic activity  

Microsoft Academic Search

Although the versatilities of zeolitic materials are widely known to chemists and materials scientists, their exclusive microporosity sometimes causes various defections especially in the diffusion of reactant and product molecules in catalytic reactions. Silica–alumina\\/epoxy-resin composite materials were obtained from TMOS (tetramethoxysilane), aluminum acetylacetonate and bisphenol A diglycidyl ether with a cyclic acid anhydride as both condensation and curing reagents. Hydrothermal

Masahiro Fujiwara; Akinori Sakamoto; Kumi Shiokawa; Astam K. Patra; Asim Bhaumik

2011-01-01

289

Stiffness matrix determination of composite materials using lamb wave group velocity measurements  

NASA Astrophysics Data System (ADS)

The use of Lamb waves in Non-Destructive Evaluation (NDE) and Structural Health Monitoring (SHM) is gaining popularity due to their ability to travel long distances without significant attenuation, therefore offering large area inspections with a small number of sensors. The design of a Lamb-wave-based NDE/SHM system for composite materials is more complicated than for metallic materials due to the directional dependence of Lamb wave propagation characteristics such as dispersion and group velocity. Propagation parameters can be theoretically predicted from known material properties, specifically the stiffness matrix and density. However, in practice it is difficult to obtain the stiffness matrix of a particular material or structure with high accuracy, hence introducing errors in theoretical predictions and inaccuracies in the resulting propagation parameters. Measured Lamb wave phase velocities can be used to infer the stiffness matrix, but the measurements are limited to the principal directions due to the steering effect (different propagation directions of phase and corresponding group velocities). This paper proposes determination of the stiffness matrix from the measured group velocities, which can be unambiguously measured in any direction. A highly anisotropic carbon-fibre-reinforced polymer plate is chosen for the study. The influence of different stiffness matrix elements on the directional group velocity profile is investigated. Thermodynamic Simulated Annealing (TSA) is used as a tool for inverse, multi variable inference of the stiffness matrix. A good estimation is achieved for particular matrix elements.

Putkis, O.; Croxford, A. J.

2013-04-01

290

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

291

A new ferromagnetic hysteresis model for soft magnetic composite materials  

NASA Astrophysics Data System (ADS)

A new ferromagnetic hysteresis model for soft magnetic composite materials based on their specific properties is presented. The model relies on definition of new anhysteretic magnetization based on the Cauchy-Lorentz distribution describing the maximum energy state of magnetic moments in material. Specific properties of soft magnetic composite materials (SMC) such as the presence of the bonding material, different sizes and shapes of the Fe particles, level of homogeneity of the Fe particles at the end of the SMC product treatment, and achieved overall material density during compression, are incorporated in both the anhysteretic differential magnetization susceptibility and the irreversible differential magnetization susceptibility. Together they form the total differential magnetization susceptibility that defines the new ferromagnetic hysteresis model. Genetic algorithms are used to determine the optimal values of the proposed model parameters. The simulated results show good agreement with the measured results.

Zidari?, Bogomir; Miljavec, Damijan

2011-01-01

292

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

293

Simulation of composite material response under dynamic compressive loading  

SciTech Connect

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

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

1993-12-31

294

Experimental Investigation of Textile Composite Materials Using Moire Interferometry  

NASA Technical Reports Server (NTRS)

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

Ifju, Peter G.

1995-01-01

295

The effective Kerr constant of an electrooptical composite material  

Microsoft Academic Search

A general relationship is derived for the effective Kerr constant of an electrooptical composite material containing nonlinear\\u000a centrosymmetric dielectric microcrystals; anisotropy of the inclusions and their nonsphericity were taken into account. It\\u000a is shown that nonsphericity of the particles makes it possible to substantially enhance the Kerr constant of the composite\\u000a in the case when the glass-matrix permittivity is much

A. A. Berezhno?; M. I. Vasil’ev; A. O. Volchek; A. V. Dotsenko; V. A. Tsekhomskii

2002-01-01

296

Pin bearing evaluation of LTM25 composite materials  

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

297

Antibacterial activity of resin composites with silver-containing materials.  

PubMed

Resin composites with antibacterial activity may be useful to decrease the frequency of secondary caries around restorations. The purposes of this study were to investigate the antibacterial activity of light-activated resin composites incorporating one of three silver-containing materials and to evaluate their long-term inhibitory effect against Streptococcus mutans The three types of silver-containing materials, Novaron (N), Amenitop (AM), and AIS, were incorporated into TEGDMA-UDMA-based light-activated resin composites, and the antibacterial activities, mechanical properties and release of silver ions were examined. Minimum inhibitory concentrations in suspensions of N, AM, and AIS against S. mutans were 1.1, 1.2, and 23.0 mg/ml, respectively. Resin composites incorporating 5 wt% of Novaron (N-5) and 7 wt% of Amenitop (AM-7) inhibited the growth of S. mutans after immersion in water for 3 months, whereas the resin composite incorporating 10 wt% of AIS did not. No significant difference in either compressive or flexural strength was observed between the control and N-5 composites after 1 d and 3 months storage in water. However, for AM-5 composite, there was a significant difference in both strength parameters between the two immersion periods. There was no or extremely little release of silver ions from the N-5 and AM-5 composites after 1 d or 3 months immersion in water. These results indicated that a light-activated resin composite incorporating silver-containing materials such as Novaron may be clinically useful due to its long-term inhibitory effect against S. mutans and favorable mechanical properties. PMID:10467945

Yoshida, K; Tanagawa, M; Matsumoto, S; Yamada, T; Atsuta, M

1999-08-01

298

Materials Science and Engineering A 422 (2006) 8591 Influence of additives on anisotropic grain growth  

E-print Network

, S.J. Pennycookd a Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN, United States b Institute for Engineering Innovation, University of Tokyo, Tokyo, Japan c Institute for Ceramics 14 November 2005 Abstract Tailoring microstructure and composition are critical components

Pennycook, Steve

299

Effective thermal conductivity of a thin composite material  

SciTech Connect

The thermal conductivity of a randomly oriented composite material is modeled using a probabilistic approach in order to determine if a size effect exists for the thermal conductivity at small composite thickness. The numerical scheme employs a random number generator to position the filler elements, which have a relatively high thermal conductivity, within a matrix having a relatively low thermal conductivity. Results indicate that, below some threshold thickness, the composite thermal conductivity increases with decreasing thickness, while above the threshold the thermal conductivity is independent of thickness. The threshold thickness increases for increasing filler fraction and increasing k{sub f}/k{sub m}, the ratio between filler and matrix thermal conductivities.

Phelan, P.E. [Arizona State Univ., Tempe, AZ (United States). Dept. of Mechanical and Aerospace Engineering; Niemann, R.C. [Argonne National Lab., IL (United States)

1996-12-31

300

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

301

An isoelastic prosthesis using a new composite material.  

PubMed

A new particulate composite material has been assessed with regard to the design of an 'isoelastic' or 'modulus matched' hip prosthesis. Three different prototype designs were assessed, each of which consisted of a femoral component made from the composite material, attached to a metal ball via a metal 'spike' insert. The prototypes varied in terms of the detailed shape of the spike, which was modified in the light of photoelastic stress analysis, so as to produce a more acceptable stress distribution to the composite material in the proximal region. Prototypes were made by hand moulding and by transfer moulding; both methods produced defects of various kinds. Simulation tests were conducted using a model of the proximal femur constructed from glass fibre composite, cyclically loaded in a servo-hydraulic testing machine. Though some difficulties were experienced with defective mouldings, especially for the transfer moulding process, a clear improvement was demonstrated for the final (Mark III) design. The fatigue endurance of this prototype was similar to that of conventional metal prostheses tested under similar conditions. Fatigue crack propagation tests were carried out on samples of the composite material to establish its propagation threshold. These results were combined with a finite element stress analysis and fracture mechanics theory to estimate the critical crack length for fatigue in this prosthesis. It was thus possible to specify the maximum safe size of defect that could be tolerated in use. PMID:8280313

Taylor, D; Martin, C; Cornelis, B; Jones, M E

1993-01-01

302

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

303

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

304

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.

305

CI2 Composite materials for lithium battery application: influence of processing and composition on electrochemical performance  

Microsoft Academic Search

In the field of electrodes for lithium batteries, the most important present advances deal with new families of active materials and new principles of energy storage in these materials. Very scarce research is devoted to the composite electrode as a whole however. The electrode is in fact a very complex medium that needs to bring efficiently the ionic reactants (Li+

D. Guy; E. Ligneel; V. Gaudefroy; B. Lestriez; R. Bouchet; D. Guyomartd

306

Mechanical and Material Properties of Metal Matrix Composite Conducting Alloys  

Microsoft Academic Search

The contact resistance and wear behavior of conducting contact surfaces is a function of hardness, applied load and material constituents. This paper presents mechanical and material properties of conducting alloys fabricated as functionally graded metal matrix composites (MMCs); in particular copper\\/tungsten, copper\\/tungsten carbide, and bronze\\/tungsten-carbide. Tungsten and in particular tungsten-carbide reinforcing particles are attractive in this application for their high

Lloyd Brown; Peter Joyce; Andrea Lazzarro

2010-01-01

307

Modeling the Mechanical Behavior of Ceramic Matrix Composite Materials  

NASA Technical Reports Server (NTRS)

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

Jordan, William

1998-01-01

308

Compendium of Material Composition Data for Radiation Transport Modeling  

SciTech Connect

Computational modeling of radiation transport problems including homeland security, radiation shielding and protection, and criticality safety all depend upon material definitions. This document has been created to serve two purposes: 1) to provide a quick reference of material compositions for analysts and 2) a standardized reference to reduce the differences between results from two independent analysts. Analysts are always encountering a variety of materials for which elemental definitions are not readily available or densities are not defined. This document provides a location where unique or hard to define materials will be located to reduce duplication in research for modeling purposes. Additionally, having a common set of material definitions helps to standardize modeling across PNNL and provide two separate researchers the ability to compare different modeling results from a common materials basis.

Williams, Ralph G.; Gesh, Christopher J.; Pagh, Richard T.

2006-10-31

309

Zirconia–hydroxyapatite composite material with micro porous structure  

Microsoft Academic Search

ObjectivesTitanium plates and apatite blocks are commonly used for restoring large osseous defects in dental and orthopedic surgery. However, several cases of allergies against titanium have been recently reported. Also, sintered apatite block does not possess sufficient mechanical strength. In this study, we attempted to fabricate a composite material that has mechanical properties similar to biocortical bone and high bioaffinity

Takuya Junior Matsumoto; Sang-Hyun An; Takuya Ishimoto; Takayoshi Nakano; Satoshi Imazato

2011-01-01

310

Biomimicry of bamboo bast fiber with engineering composite materials  

Microsoft Academic Search

Bamboo, one of the strongest natural structural composite materials, has many distinguishing features. It has been found that its reinforcement unit, hollow, multilayered and spirally-wound bast fiber, plays an extremely important role in its mechanical behavior. In the present work, on the basis of the study on bamboo bast fiber and wood tracheid, a biomimetic model of the reinforcing element,

S. H. Li; Q. Y. Zeng; Y. L. Xiao; S. Y. Fu; B. L. Zhou

1995-01-01

311

Characteristics of soft magnetic composite material under rotating magnetic fluxes  

Microsoft Academic Search

This paper reports the measurement of magnetic properties of the soft magnetic composite material SOMALOYTM 500 in a square sample under different patterns of flux density with 2D magnetic excitations. The test system, principle of measurement, magnetic power loss calculation, and methods of correction for misalignment of H surface sensing coils are presented. The experimental results show that although nominally

J. J. Zhong; Y. G. Guo; J. G. Zhu; Z. W. Lin

2006-01-01

312

Manufacture of composite electrochemical materials from suspended electrolytes  

NASA Astrophysics Data System (ADS)

New composite electrochemical materials on a metallic substrate synthesized from suspended electrolytes with additives of kaolin and bentonite powders of the nanosized fraction are studied. The limiting concentrations of the additives in the electrolyte that warrant the retention of the decorative and special properties of the microchromium coating are determined.

Plotnikova, O. G.; Mal'kova, M. Yu.; Gruzd, N. S.; Zadiranov, A. N.; Paretskii, V. M.

2013-12-01

313

Studies of heterogeneous samples and material composition by fluorescence XAFS  

Microsoft Academic Search

X-ray Absorption Fine Structure (XAFS) Spectroscopy has proven to be an important tool for studying the composition and structure of materials. One benefit of XAFS is that it can be applied to a wide variety of systems, including complex real-world samples such as those found in biology and the environment. Determination of the chemical speciation of toxic elements in the

Firouzeh Tannazi

2004-01-01

314

MALE MOLDING FABRICATION PROCESS DEVELOPMENT WITH COMPOSITE MATERIALS  

E-print Network

PENNSTATE _ MALE MOLDING FABRICATION PROCESS DEVELOPMENT WITH COMPOSITE MATERIALS Yooku Tachie. The advantage of female molding, which is typically used, is that it provides a smooth outer molded surface operation. Male molding is generally less labor intensive, and allows the beam to be fabricated as a single

Yener, Aylin

315

Aluminum-matrix composite materials with shungite rock fillers  

NASA Astrophysics Data System (ADS)

A method is proposed for the introduction of shungite rocks into aluminum melts by mechanical mixing with carriers, namely, aluminum granules and reactive titanium powders taking part in exothermic in situ reactions. The structures of composite materials with shungite rock additions are studied, and a stabilizing effect of these additions on dry sliding friction is revealed.

Kalashnikov, I. E.; Kovalevski, V. V.; Chernyshova, T. A.; Bolotova, L. K.

2010-11-01

316

A three dimensional calculation of elastic equilibrium for composite materials  

NASA Technical Reports Server (NTRS)

A compact scheme is applied to three-dimensional elasticity problems for composite materials, involving simple geometries. The mathematical aspects of this approach are discussed, in particular the iteration method. A vector processor code implementing the compact scheme is presented, and several numerical experiments are summarized.

Lustman, Liviu R.; Rose, Milton E.

1986-01-01

317

Numerical Simulation of Delamination Growth in Composite Materials  

Microsoft Academic Search

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

P. P. Camanho; D. R. Ambur

2001-01-01

318

Damping Experiment of Spinning Composite Plates With Embedded Viscoelastic Material  

NASA Technical Reports Server (NTRS)

One way to increase gas turbine engine blade reliability and durability is to reduce blade vibration. It is well known that vibration can be reduced by adding damping to metal and composite blade-disk systems. As part of a joint research effort of the NASA Lewis Research Center and the University of California, San Diego, the use of integral viscoelastic damping treatment to reduce the vibration of rotating composite fan blades was investigated. The objectives of this experiment were to verify the structural integrity of composite plates with viscoelastic material patches embedded between composite layers while under large steady forces from spinning, and to measure the damping and natural frequency variation with rotational speed.

Mehmed, Oral

1998-01-01

319

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

Microsoft Academic Search

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

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

2009-01-01

320

Assessment of space environment induced microdamage in toughened composite materials  

NASA Technical Reports Server (NTRS)

The effects of simulated space environments on the microdamage in a series of commercially available toughened matrix composite systems was determined. Low-earth orbit (LEO) exposures were simulated by thermal cycling; geosynchronous orbit (GEO) exposures were simulated by electron irradiation plus thermal cycling. Material response was characterized by assessing the induced microcracking and its influence on chemical and mechanical property changes. All materials, including several advanced, tough thermoplastics microcracked when exposed to the simulated LEO environment except a 177 C cured single phase toughened epoxy composite. The GEO simulated environment produced microdamage in all materials. The results suggest that increased matrix toughness may not be the overriding factor leading to improved durability in the space environment.

Sykes, George F.; Funk, Joan G.; Slemp, Wayne S.

1986-01-01

321

Recent Advances and Developments in Composite Dental Restorative Materials  

PubMed Central

Composite dental restorations represent a unique class of biomaterials with severe restrictions on biocompatibility, curing behavior, esthetics, and ultimate material properties. These materials are presently limited by shrinkage and polymerization-induced shrinkage stress, limited toughness, the presence of unreacted monomer that remains following the polymerization, and several other factors. Fortunately, these materials have been the focus of a great deal of research in recent years with the goal of improving restoration performance by changing the initiation system, monomers, and fillers and their coupling agents, and by developing novel polymerization strategies. Here, we review the general characteristics of the polymerization reaction and recent approaches that have been taken to improve composite restorative performance. PMID:20924063

Cramer, N.B.; Stansbury, J.W.; Bowman, C.N.

2011-01-01

322

Application of Raman Spectroscopy for Nondestructive Evaluation of Composite Materials  

NASA Technical Reports Server (NTRS)

This paper will present an overview of efforts to investigate the application of Raman spectroscopy for the characterization of Kevlar materials. Raman spectroscopy is a laser technique that is sensitive to molecular interactions in materials such as Kevlar, graphite and carbon used in composite materials. The overall goal of this research reported here is to evaluate Raman spectroscopy as a potential nondestructive evaluation (NDE) tool for the detection of stress rupture in Kevlar composite over-wrapped pressure vessels (COPVs). Characterization of the Raman spectra of Kevlar yarn and strands will be presented and compared with analytical models provided in the literature. Results of testing to investigate the effects of creep and high-temperature aging on the Raman spectra will be presented.

Washer, Glenn A.; Brooks, Thomas M. B.; Saulsberry, Regor

2007-01-01

323

Separating anisotropic material effects in the control signals of inverter-fed AC machines  

Microsoft Academic Search

In the non-model-based mechanical sensorless control of AC machines the flux\\/rotor position can be estimated by evaluating the current response to voltage pulses. This current slope is modulated by all spatial saliencies in the machine. Sources of these saliencies can be various, for instance the saturation of the machine by the main flux, the slotting, lamination material anisotropy as well

Thomas M. Wolbank; Juergen L. Machl; Hans Hauser

2004-01-01

324

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

NASA Astrophysics Data System (ADS)

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

Yoon, Joonsung

325

A Study of Failure Criteria of Fibrous Composite Materials  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

326

Percolation modeling of self-damaging of composite materials  

NASA Astrophysics Data System (ADS)

We propose the concept of autonomous self-damaging in “smart” composite materials, controlled by activation of added nanosize “damaging” capsules. Percolation-type modeling approach earlier applied to the related concept of self-healing materials, is used to investigate the behavior of the initial material's fatigue. We aim at achieving a relatively sharp drop in the material's integrity after some initial limited fatigue develops in the course of the sample's usage. Our theoretical study considers a two-dimensional lattice model and involves Monte Carlo simulations of the connectivity and conductance in the high-connectivity regime of percolation. We give several examples of local capsule-lattice and capsule-capsule activation rules and show that the desired self-damaging property can only be obtained with rather sophisticated “smart” material's response involving not just damaging but also healing capsules.

Domanskyi, Sergii; Privman, Vladimir

2014-07-01

327

Development of a novel regenerated cellulose composite material.  

PubMed

We report for the first time on a new natural composite material achieved by blending cotton and duck feather using an ionic liquid. The addition of duck feather was found to improve the elasticity, strain at break, by 50% when compared to regenerated cellulose alone. This is a significant finding since regenerated cotton using ionic liquids often suffers from poor elasticity. The improved elasticity is likely due to the regenerated duck feather maintaining its helical structure. The new regenerated cellulose composites were characterized using a combination of dynamic mechanical analysis, Fourier transform infrared spectroscopy, thermal gravimetric analysis, contact angle measurements and scanning electron microscopy. PMID:25659713

De Silva, Rasike; Vongsanga, Kylie; Wang, Xungai; Byrne, Nolene

2015-05-01

328

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

NASA Technical Reports Server (NTRS)

This report presents a summary of results from a 7 year program designed to develop generic constitutive and life prediction approaches and models for nickel-based single crystal gas turbine airfoils. The program was composed of a base program and an optional program. The base program addressed the high temperature coated single crystal regime above the airfoil root platform. The optional program investigated the low temperature uncoated single crystal regime below the airfoil root platform including the notched conditions of the airfoil attachment. Both base and option programs involved experimental and analytical efforts. Results from uniaxial constitutive and fatigue life experiments of coated and uncoated PWA 1480 single crystal material formed the basis for the analytical modeling effort. Four single crystal primary orientations were used in the experiments: group of zone axes (001), group of zone axes (011), group of zone axes (111), and group of zone axes (213). Specific secondary orientations were also selected for the notched experiments in the optional program. Constitutive models for an overlay coating and PWA 1480 single crystal materials were developed based on isothermal hysteresis loop data and verified using thermomechanical (TMF) hysteresis loop data. A fatigue life approach and life models were developed for TMF crack initiation of coated PWA 1480. A life model was developed for smooth and notched fatigue in the option program. Finally, computer software incorporating the overlay coating and PWA 1480 constitutive and life models was developed.

Nissley, D. M.; Meyer, T. G.; Walker, K. P.

1992-01-01

329

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

NASA Technical Reports Server (NTRS)

This report presents the results from a 35 month period of a program designed to develop generic constitutive and life prediction approaches and models for nickel-based single crystal gas turbine airfoils. The program is composed of a base program and an optional program. The base program addresses the high temperature coated single crystal regime above the airfoil root platform. The optional program investigates the low temperature uncoated single crystal regime below the airfoil root platform including the notched conditions of the airfoil attachment. Both base and option programs involve experimental and analytical efforts. Results from uniaxial constitutive and fatigue life experiments of coated and uncoated PWA 1480 single crystal material form the basis for the analytical modeling effort. Four single crystal primary orientations were used in the experiments: (001), (011), (111), and (213). Specific secondary orientations were also selected for the notched experiments in the optional program. Constitutive models for an overlay coating and PWA 1480 single crystal material were developed based on isothermal hysteresis loop data and verified using thermomechanical (TMF) hysteresis loop data. A fatigue life approach and life models were selected for TMF crack initiation of coated PWA 1480. An initial life model used to correlate smooth and notched fatigue data obtained in the option program shows promise. Computer software incorporating the overlay coating and PWA 1480 constitutive models was developed.

Nissley, D. M.; Meyer, T. G.

1992-01-01

330

The aqueous corrosion behavior of technetium - Alloy and composite materials  

SciTech Connect

Metal waste forms are under study as possible disposal forms for technetium and other fission products. The alloying of Tc is desirable to reduce the melting point of the Tc-containing metal waste form and potentially improve its corrosion resistance. Technetium-nickel composites were made by mixing the two metal powders and pressing the mixture to make a pellet. The as-pressed composite materials were compared to sintered composites and alloys of identical composition in electrochemical corrosion tests. As-pressed samples were not robust enough for fine polishing and only a limited number of corrosion tests were performed. Alloys and composites with 10 wt% Tc appear to be more corrosion resistant at open circuit than the individual components based on linear polarization resistance and polarization data. The addition of 10 wt% Tc to Ni appears beneficial at open circuit, but detrimental upon anodic polarization. Qualitatively, the polarizations of 10 wt% Tc alloys and composites appear like crude addition of Tc plus Ni. The 1 wt% Tc alloys behave like pure Ni, but some effect of Tc is seen upon polarization. Cathodic polarization of Tc by Ni appears feasible based on open circuit potential measurements, however, zero resistance ammetry and solution measurements are necessary to confirm cathodic protection.

Jarvinen, G.; Kolman, D.; Taylor, C.; Goff, G.; Cisneros, M. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Mausolf, E.; Poineau, F.; Koury, D.; Czerwinski, K. [Department of Chemistry, University of Nevada, Las Vegas, Las Vegas, NV 89154 (United States)

2013-07-01

331

Elastoplastic analysis of thermal cycling: Layered materials with compositional gradients  

SciTech Connect

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

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

1995-04-01

332

Composite smart materials using high-volume microelectronics fabrication techniques  

NASA Astrophysics Data System (ADS)

Smart materials, containing sensors, actuators and processing electronics, are of great potential use in defense and commercial applications from acoustic stealth to medial imaging. While 1:3 composites using PZT rods are now available commercially in limited quantities, composites with individually addressable actuator and sensor arrays are not, nor have conditioning and processing electronics been embedded in the same material. There are several technical and cost reasons for this, including the complexity of interconnections, capacitance of individual elements, thermal dissipation, and the expense of fabricating the material. We have been developing composite materials comprising arrays of miniature actuators fabricated using surface mount capacitor technology, and amenable to automated fabrication using `pick and place' techniques. Miniature actuators with up to 0.1% strain, and operating at 30 V bias and ac swing of +/- 30 V have been fabricated, and placed in 10-by- 10 actuator arrays on Kapton sheets on which circuits have been printed. The arrays were then `potted' in RTV liquid rubbers. Individual actuator motion and multiple actuator influence functions were measured as a function of applied voltage and adjacent actuator motion. These results, along with in-water performance (source level and directivity), are presented.

Winzer, Stephen R.; Shankar, Natarajan; Caldwell, Paul J.; May, Russell G.

1995-05-01

333

Single-walled carbon nanotube networks in conductive composite materials.  

PubMed

Electrically conductive composite materials can be used for a wide range of applications because they combine the advantages of a specific polymeric material (e.g., thermal and mechanical properties) with the electrical properties of conductive filler particles. However, the overall electrical behaviour of these composite materials is usually much below the potential of the conductive fillers, mainly because by mixing two different components, new interfaces and interphases are created, changing the properties and behaviours of both. Our goal is to characterize and understand the nature and influence of these interfaces on the electrical properties of composite materials. We have improved a technique based on the use of sodium carboxymethyl cellulose (CMC) to disperse single-walled carbon nanotubes (SWCNTs) in water, followed by coating glass substrates, and drying and removing the CMC with a nitric acid treatment. We used electron microscopy and atomic force microscopy techniques to characterize the SWCNT films, and developed an in situ resistance measurement technique to analyse the influence of both the individual components and the mixture of an epoxy/amine system on the electrical behaviour of the SWCNTs. The results showed that impregnating a SWCNT network with a polymer is not the only factor that affects the film resistance; air exposure, temperature, physical and chemical properties of the individual polymer components, and also the formation of a polymeric network, can all have an influence on the macroscopic electrical properties of the initial SWCNT network. These results emphasize the importance of understanding the effects that each of the components can have on each other before trying to prepare an efficient polymer composite material. PMID:25430670

Bârsan, Oana A; Hoffmann, Günter G; van der Ven, Leo G J; de With, G Bert

2014-01-01

334

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

NASA Astrophysics Data System (ADS)

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

You, Zhongqing; Lusk, M.; Ludwig, Reinhold; Lord, William

1991-09-01

335

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

336

Dropping the Ball: The effect of anisotropic granular materials on ejecta and impact crater shape  

E-print Network

In this fluid dynamics video, we present an experimental investigation of the shape of impact craters in granular materials. Complex crater shapes, including polygons, have been observed in many terrestrial planets as well as moons and asteroids. We release spherical projectiles from different heights above a granular bed (sand). The experiments demonstrate two different techniques to create non-circular impact craters, which we measure by digitizing the final crater topography. In the first method, we create trenches in the sand to mimic fault lines or valleys on a planetary target. During impact, ejecta move faster in the direction of the trenches, creating nearly elliptical craters with the major axis running parallel to the trench. Larger trenches lead to more oblong craters. In the second method, a hose beneath the surface of the sand injects nitrogen gas. The pressure of the gas counters the hydrostatic pressure of the sand, greatly reducing static friction between grains above the injection point, with...

Drexler, Philip; Arratia, Paulo

2013-01-01

337

Compendium of Material Composition Data for Radiation Transport Modeling  

SciTech Connect

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

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

2011-03-04

338

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

SciTech Connect

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

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

1997-12-01

339

Wetting, superhydrophobicity, and icephobicity in biomimetic composite materials  

NASA Astrophysics Data System (ADS)

Recent developments in nano- and bio-technology require new materials. Among these new classes of materials which have emerged in the recent years are biomimetic materials, which mimic structure and properties of materials found in living nature. There are a large number of biological objects including bacteria, animals and plants with properties of interest for engineers. Among these properties is the ability of the lotus leaf and other natural materials to repel water, which has inspired researchers to prepare similar surfaces. The Lotus effect involving roughness-induced superhydrophobicity is a way to design nonwetting, self-cleaning, omniphobic, icephobic, and antifouling surfaces. The range of actual and potential applications of superhydrophobic surfaces is diverse including optical, building and architecture, textiles, solar panels, lab-on-a-chip, microfluidic devices, and applications requiring antifouling from biological and organic contaminants. In this thesis, in chapter one, we introduce the general concepts and definitions regarding the wetting properties of the surfaces. In chapter two, we develop novel models and conduct experiments on wetting of composite materials. To design sustainable superhydrophobic metal matrix composite (MMC) surfaces, we suggest using hydrophobic reinforcement in the bulk of the material, rather than only at its surface. We experimentally study the wetting properties of graphite-reinforced Al- and Cu-based composites and conclude that the Cu-based MMCs have the potential to be used in the future for the applications where the wear-resistant superhydrophobicity is required. In chapter three, we introduce hydrophobic coating at the surface of concrete materials making them waterproof to prevent material failure, because concretes and ceramics cannot stop water from seeping through them and forming cracks. We create water-repellant concretes with CA close to 160o using superhydrophobic coating. In chapter four, experimental data are collected in terms of oleophobicity especially when underwater applications are of interest. We develop models for four-phase rough interface of underwater oleophobicity and develop a novel approach to predict the CA of organic liquid on the rough surfaces immersed in water. We investigate wetting transition on a patterned surface in underwater systems, using a phase field model. We demonstrated that roughening on an immersed solid surface can drive the transition from Wenzel to Cassie-Baxter state. This discovery improves our understanding of underwater systems and their surface interactions during the wetting phenomenon and can be applied for the development of underwater oil-repellent materials which are of interest for various applications in the water industry, and marine devices. In chapter five, we experimentally and theoretically investigate the icephobicity of composite materials. A novel comprehensive definition of icephobicity, broad enough to cover a variety of situations including low adhesion strength, delayed ice crystallization, and bouncing is determined. Wetting behavior and ice adhesion properties of various samples are theoretically and experimentally compared. We conclude superhydrophobic surfaces are not necessarily icephobic. The models are tested against the experimental data to verify the good agreement between them. The models can be used for the design of novel superhydrophobic, oleophobic, omniphobic and icephobic composite materials. Finally we conclude that creating surface micro/nanostructures using mechanical abrasion or chemical etching as well as applying low energy materials are the most simple, inexpensive, and durable techniques to create superhydrophobic, oleophobic, and icephobic materials.

Hejazi, Vahid

340

New toughening concepts for ceramic composites from rigid natural materials.  

PubMed

The mechanisms underlying the toughening in rigid natural composites exhibited by the concentric cylindrical composites of spicules of hexactinellid sponges, and by the nacre (brick-and-mortar) structure of mollusks such as Haliotis rufescens (red abalone), as well as the crossed-lamellar structure of Strombus gigas (queen conch) show commonalities in the manner in which toughening takes place. It is proposed that crack diversion, a new kind of crack bridging, resulting in retardation of delamination, creation of new surface areas, and other energy-dissipating mechanisms occur in both natural systems. However, these are generally different from the toughening mechanisms that are utilized for other classes of structural materials. Complementary to those mechanisms found in rigid natural ceramic/organic composites, special architectures and thin viscoelastic organic layers have been found to play controlling roles in energy dissipation in these structures. PMID:21565715

Mayer, George

2011-07-01

341

Power loss separation in Fe-based composite materials  

NASA Astrophysics Data System (ADS)

The frequency dependence of total losses measured in the frequency range from dc to 1 kHz of two Fe-based soft magnetic composites (prepared by compaction of an ASC 100.29 iron powder mixture with 10 vol% of commercial thermoset resin and of a Somaloy® 700 powder) was analyzed. We found out that hysteresis losses (per volume unit) are higher for the composite with lower volume concentration of iron particles (i.e. mixture of iron with resin) and consequently weaker magnetic interaction between particles. On the other hand, higher specific resistivity of the sample with lower magnetic fraction causes lower contribution of eddy current losses to the total losses. A linear dependence of the total energy losses on frequency was observed and from them the contribution of excess losses was obtained. The detailed study of the excess losses resulted in an explanation of the frequency dependence of these losses in composite materials.

Kollár, Peter; Bir?áková, Zuzana; Füzer, Ján; Bureš, Radovan; Fáberová, Mária

2013-02-01

342

Effective thermal conductivity of a thin, randomly oriented composite material  

SciTech Connect

The thermal conductivity of a randomly oriented composite material is modeled using a probabilistic approach in order to determine if a size effect exists for the thermal conductivity at small composite thicknesses. The numerical scheme employs a random number generator to position the filler elements, which have a relatively high thermal conductivity, within a matrix having a relatively low thermal conductivity. The results indicate that, below some threshold thickness, the composite thermal conductivity increases with decreasing thickness, while above the threshold the thermal conductivity is independent of thickness. The threshold thickness increases for increasing filler fraction and increasing k{sub f}/k{sub m}, the ratio between the filler and matrix thermal conductivities.

Phelan, P.E.; Niemann, R.C.

1997-07-01

343

Mechanical properties of Al-mica particulate composite material  

NASA Technical Reports Server (NTRS)

Cast aluminum alloy mica particle composites of varying mica content were tested in tension, compression, and impact. With 2.2 percent mica (size range 40-120 microns) the tensile and compression strengths of aluminum alloy decreased by 56 and 22 percent, respectively. The corresponding decreases in percent elongation and percent reduction are 49 and 39 percent. Previous work shows that despite this decrease in strength the composite with 2.5 percent mica and having an UTS of 15 kg/sq mm and compression strength of 28 kg/sq mm performs well as a bearing material under severe running conditions. The differences in strength characteristics of cast aluminum-mica particle composites between tension and compression suggests that, as in cast iron, expansion of voids at the matrix particle interface may be the guiding mechanism of the deformation. SEM studies show that on the tensile fractured specimen surface, there are large voids at the particle matrix interface.

Nath, D.; Bhatt, R. T.; Rohatgi, P. K.; Biswas, S. K.

1980-01-01

344

27 CFR 555.221 - Requirements for display fireworks, pyrotechnic compositions, and explosive materials used in...  

Code of Federal Regulations, 2013 CFR

...false Requirements for display fireworks, pyrotechnic compositions, and explosive materials used in assembling fireworks or articles pyrotechnic. 555...221 Requirements for display fireworks, pyrotechnic compositions,...

2013-04-01

345

27 CFR 555.221 - Requirements for display fireworks, pyrotechnic compositions, and explosive materials used in...  

...false Requirements for display fireworks, pyrotechnic compositions, and explosive materials used in assembling fireworks or articles pyrotechnic. 555...221 Requirements for display fireworks, pyrotechnic compositions,...

2014-04-01

346

27 CFR 555.221 - Requirements for display fireworks, pyrotechnic compositions, and explosive materials used in...  

Code of Federal Regulations, 2012 CFR

... true Requirements for display fireworks, pyrotechnic compositions, and explosive materials used in assembling fireworks or articles pyrotechnic. 555...221 Requirements for display fireworks, pyrotechnic compositions,...

2012-04-01

347

Material properties and fractography of an indirect dental resin composite  

PubMed Central

Objectives Determination of material and fractographic properties of a dental indirect resin composite material. Methods A resin composite (Paradigm, 3M-ESPE, MN) was characterized by strength, static elastic modulus, Knoop hardness, fracture toughness and edge toughness. Fractographic analyses of the broken bar surfaces was accomplished with a combination of optical and SEM techniques, and included determination of the type and size of the failure origins, and fracture mirror and branching constants. Results The flexure test mean strength ± standard deviation was 145 MPA ± 17 MPa, and edge toughness, Te, was 172 N/mm ±12 N/mm. Knoop hardness was load dependent, with a plateau at 0.99 GPa ± .02 GPa. Mirrors in the bar specimens were measured with difficulty, resulting in a mirror constant of approximately 2.6 MPa·m1/2. Fracture in the bar specimens initiated at equiaxed material flaws that had different filler concentrations that sometimes were accompanied by partial microcracks. Using the measured flaw sizes, which ranged from 35 µm to 100 µm in size, and estimates of the stress intensity shape factors, fracture toughness was estimated to be 1.1 MPa·m1/2 ± 0.2 MPa·m1/2. Significance Coupling the flexure tests with fractographic examination enabled identification of the intrinsic strength limiting flaws. The same techniques could be useful in determining if clinical restorations of similar materials fail from the same causes. The existence of a strong load-dependence of the Knoop hardness of the resin composite is not generally mentioned in the literature, and is important for material comparisons and wear evaluation studies. Finally, the edge toughness test was found promising as a quantitative measure of resistance to edge chipping, an important failure mode in this class of materials. PMID:20304478

Quinn, Janet B.; Quinn, George D.

2011-01-01

348

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

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

349

A fast multipole hybrid boundary node method for composite materials  

NASA Astrophysics Data System (ADS)

This article presents a multi-domain fast multipole hybrid boundary node method for composite materials in 3D elasticity. The hybrid boundary node method (hybrid BNM) is a meshless method which only requires nodes constructed on the surface of a domain. The method is applied to 3D simulation of composite materials by a multi-domain solver and accelerated by the fast multipole method (FMM) in this paper. The preconditioned GMRES is employed to solve the final system equation and precondition techniques are discussed. The matrix-vector multiplication in each iteration is divided into smaller scale ones at the sub-domain level and then accelerated by FMM within individual sub-domains. The computed matrix-vector products at the sub-domain level are then combined according to the continuity conditions on the interfaces. The algorithm is implemented on a computer code written in C + +. Numerical results show that the technique is accurate and efficient.

Wang, Qiao; Miao, Yu; Zhu, Hongping

2013-06-01

350

Degradation, fatigue and failure of resin dental composite materials  

PubMed Central

The intent of this article is to review the numerous factors that affect the mechanical properties of particle or fiber filler containing, indirect dental resin composite materials. The focus will be on degradation due to aging in different media, mainly water and water and ethanol, cyclic loading, and mixed mode loading on the flexure strength and fracture toughness. Next several selected papers will be examined in detail with respect to mixed and cyclic loading and then an examination of 3D tomography using multiaxial compression specimens. The main cause of failure, for most dental resin composites, is the breakdown of the resin matrix and or the interface between the filler and the resin matrix. In clinical studies, it appears that failure in the first 5 years is a restoration issue (technique or material selection) and after that time period from secondary decay. PMID:18650540

Drummond, James L.

2008-01-01

351

Characterization of carbon fiber composite materials for RF applications  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

352

Ultrasonic and radiographic evaluation of advanced aerospace materials: Ceramic composites  

NASA Technical Reports Server (NTRS)

Two conventional nondestructive evaluation techniques were used to evaluate advanced ceramic composite materials. It was shown that neither ultrasonic C-scan nor radiographic imaging can individually provide sufficient data for an accurate nondestructive evaluation. Both ultrasonic C-scan and conventional radiographic imaging are required for preliminary evaluation of these complex systems. The material variations that were identified by these two techniques are porosity, delaminations, bond quality between laminae, fiber alignment, fiber registration, fiber parallelism, and processing density flaws. The degree of bonding between fiber and matrix cannot be determined by either of these methods. An alternative ultrasonic technique, angular power spectrum scanning (APSS) is recommended for quantification of this interfacial bond.

Generazio, Edward R.

1990-01-01

353

Composite material from recycled polyester for recyclable automobile structures  

SciTech Connect

DuPont has developed a compression-moldable composite made from the thermoplastic polyester PET and long glass fibers. This material, XTC{trademark}, is part of the class of materials known as GMT`s, or glass-mat thermoplastics. The PET content in XTC{trademark} allows the use of a wide variety of recycled material that might otherwise end up in landfills and incinerators. DuPont has succeeded in using 100% post-consumer polyester, from bottles, film, or fibers, in the composite. Since processing involves heating the material to the melt in air, the main technical issues are hydrolysis and oxidative degradation. Impurities in the recycled material must be carefully monitored, as they often increase the extent of degradation. The product itself, used to mold shaped structures and body panels for automobiles, may be recycled after its useful life. Depending on the needed purity level, processes ranging from injection molding to methanolysis can turn ground XTC{trademark} parts back into new, useful products.

Lertola, J.G. [DuPont Company, Newark, DE (United States)

1995-12-31

354

Modeling Lightning Impact Thermo-Mechanical Damage on Composite Materials  

NASA Astrophysics Data System (ADS)

Carbon fiber-reinforced polymers, used in primary structures for aircraft due to an excellent strength-to-weight ratio when compared with conventional aluminium alloy counterparts, may nowadays be considered as mature structural materials. Their use has been extended in recent decades, with several aircraft manufacturers delivering fuselages entirely manufactured with carbon composites and using advanced processing technologies. However, one of the main drawbacks of using such composites entails their poor electrical conductivity when compared with aluminium alloy competitors that leads to lightning strikes being considered a significant threat during the service life of the aircraft. Traditionally, this problem was overcome with the use of a protective copper/bronze mesh that added additional weight and reduced the effectiveness of use of the material. Moreover, this traditional sizing method is based on vast experimental campaigns carried out by subjecting composite panels to simulated lightning strike events. While this method has proven its validity, and is necessary for certification of the structure, it may be optimized with the aid provided by physically based numerical models. This paper presents a model based on the finite element method that includes the sources of damage observed in a lightning strike, such as thermal damage caused by Joule overheating and electromagnetic/acoustic pressures induced by the arc around the attachment points. The results of the model are compared with lightning strike experiments carried out in a carbon woven composite.

Muñoz, Raúl; Delgado, Sofía; González, Carlos; López-Romano, Bernardo; Wang, De-Yi; LLorca, Javier

2014-02-01

355

Probability techniques for reliability analysis of composite materials  

NASA Technical Reports Server (NTRS)

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

Wetherhold, Robert C.; Ucci, Anthony M.

1994-01-01

356

Composite slip table of dissimilar materials for damping longitudinal modes  

DOEpatents

A vibration slip table for use in a vibration testing apparatus. The table s comprised of at least three composite layers of material; a first metal layer, a second damping layer, and a third layer having a high acoustic velocity relative to the first layer. The different acoustic velocities between the first and third layers cause relative shear displacements between the layers with the second layer damping the displacements between the first and third layers to reduce the table longitudinal vibration modes.

Gregory, Danny L. (Albuquerque, NM); Priddy, Tommy G. (Albuquerque, NM); Smallwood, David O. (Albuquerque, NM); Woodall, Tommy D. (Albuquerque, NM)

1991-01-01

357

Nanocrystal-Based Polymer Composites as Novel Functional Materials  

Microsoft Academic Search

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

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

358

Manganese oxide–carbon composite as supercapacitor electrode materials  

Microsoft Academic Search

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

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

2009-01-01

359

3D vector magnetic properties of soft magnetic composite material  

Microsoft Academic Search

Even under one-dimensional (1D) alternating or 2D rotating magnetic excitation, a magnetic material shows 3D magnetic property due to the rotation of magnetic domains. Only when the 3D properties are properly considered the understanding and modelling of the magnetisation process can be complete. This paper summarises our work about the investigation on the magnetic properties of soft magnetic composite (SMC)

Y. G. Guo; J. G. Zhu; Z. W. Lin; J. J. Zhong

2006-01-01

360

Aluminum Foam-Phase Change Material Composites as Heat Exchangers  

Microsoft Academic Search

The effects of geometric parameters of open-cell aluminum foams on the performance of aluminum foam-phase change material (PCM) composites as heat sinks are investigated by experiments. Three types of open-cell aluminum 6061 foams with similar relative densities and different cell sizes are used. Paraffin is selected as the PCM due to its excellent thermal stability and ease of handling. The

Sung-tae Hong; Darrell R. Herling

2007-01-01

361

Composite Materials for Marine Applications: Key Challenges for the Future  

Microsoft Academic Search

\\u000a This chapter presents the key challenges for the future use of composite materials for marine applications. Five technical\\u000a challenges have been identified: load transfer mechanisms, safety, life cycle assessment, concurrent engineering and structural\\u000a health monitoring. These are discussed in the following sections of the chapter. The mechanical behaviour of layered orthotropic\\u000a structures is considered for both adhesively bonded and hybrid

R. A. Shenoi; J. M. Dulieu-Barton; S. Quinn; J. I. R. Blake; S. W. Boyd

362

SRM nozzle design breakthroughs with advanced composite materials  

NASA Astrophysics Data System (ADS)

The weight reduction-related performance and cost of the Space Shuttle's Solid Rocket Motor (SRM) units' critical nozzle components are undergoing revolutionary improvements through the use of 3D-woven carbon/carbon and carbon/alumina composite materials. These can be used to fabricate the SRM's nozzle throat nondegradable insulators, thermostructural insulator, and exit cones. Additional developments are noted among nozzle-related structural components for additional rocket propulsion systems, including a three-piece extendible nozzle.

Berdoyes, Michel

1993-06-01

363

Optimized material composition to improve the physical and mechanical properties of extruded wood–plastic composites (WPCs)  

Microsoft Academic Search

Wood–plastic composite (WPC) is an environmentally progress way of combining recycled plastics and wood flour. The composite typically consists of four major elements: wood flour, thermoplastic plastics, coupling agent, and lubricant. The physical and mechanical properties of WPCs highly depend on the material formulation, and the optimal material composition is an essential topic of current research. This study investigated the

Shao-Yuan Leu; Tsu-Hsien Yang; Sheng-Fong Lo; Te-Hsin Yang

364

The Abundance and Isotopic Composition of Hg in Extraterrestrial Materials  

NASA Technical Reports Server (NTRS)

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

Lauretta, D. S.

2004-01-01

365

Autonomic composite hydrogels by reactive printing: materials and oscillatory response.  

PubMed

Autonomic materials are those that automatically respond to a change in environmental conditions, such as temperature or chemical composition. While such materials hold incredible potential for a wide range of uses, their implementation is limited by the small number of fully-developed material systems. To broaden the number of available systems, we have developed a post-functionalization technique where a reactive Ru catalyst ink is printed onto a non-responsive polymer substrate. Using a succinimide-amine coupling reaction, patterns are printed onto co-polymer or biomacromolecular films containing primary amine functionality, such as polyacrylamide (PAAm) or poly-N-isopropyl acrylamide (PNIPAAm) copolymerized with poly-N-(3-Aminopropyl)methacrylamide (PAPMAAm). When the films are placed in the Belousov-Zhabotinsky (BZ) solution medium, the reaction takes place only inside the printed nodes. In comparison to alternative BZ systems, where Ru-containing monomers are copolymerized with base monomers, reactive printing provides facile tuning of a range of hydrogel compositions, as well as enabling the formation of mechanically robust composite monoliths. The autonomic response of the printed nodes is similar for all matrices in the BZ solution concentrations examined, where the period of oscillation decreases in response to increasing sodium bromate or nitric acid concentration. A temperature increase reduces the period of oscillations and temperature gradients are shown to function as pace-makers, dictating the direction of the autonomic response (chemical waves). PMID:24651297

Kramb, R C; Buskohl, P R; Slone, C; Smith, M L; Vaia, R A

2014-03-01

366

Sub-diffraction light propagation in fibers with anisotropic dielectric cores  

E-print Network

We present a detailed study of light propagation in waveguides with anisotropic metamaterial cores. We demonstrate that in contrast to conventional optical fibers, our structures support free-space-like propagating modes even when the waveguide radius is much smaller than the wavelength. We develop analytical formalism to describe mode structure and propagation in strongly anisotropic systems and study the effects related to waveguide boundaries and material composition.

Alexander A Govyadinov; Viktor A Podolskiy

2006-05-04

367

Material Issues in Space Shuttle Composite Overwrapped Pressure Vessels  

NASA Technical Reports Server (NTRS)

Composite Overwrapped Pressure Vessels (COPV) store gases used in four subsystems for NASA's Space Shuttle Fleet. While there are 24 COPV on each Orbiter ranging in size from 19-40", stress rupture failure of a pressurized Orbiter COPV on the ground or in flight is a catastrophic hazard and would likely lead to significant damage/loss of vehicle and/or life and is categorized as a Crit 1 failure. These vessels were manufactured during the late 1970's and into the early 1980's using Titanium liners, Kevlar 49 fiber, epoxy matrix resin, and polyurethane coating. The COPVs are pressurized periodically to 3-5ksi and therefore experience significant strain in the composite overwrap. Similar composite vessels were developed in a variety of DOE Programs (primarily at Lawrence Livermore National Laboratories or LLNL), as well as for NASA Space Shuttle Fleet Leader COPV program. The NASA Engineering Safety Center (NESC) formed an Independent Technical Assessment (ITA) team whose primary focus was to investigate whether or not enough composite life remained in the Shuttle COPV in order to provide a strategic rationale for continued COPV use aboard the Space Shuttle Fleet with the existing 25-year-old vessels. Several material science issues were examined and will be discussed in this presentation including morphological changes to Kevlar 49 fiber under stress, manufacturing changes in Kevlar 49 and their effect on morphology and tensile strength, epoxy resin strain, composite creep, degradation of polyurethane coatings, and Titanium yield characteristics.

Sutter, James K.; Jensen, Brian J.; Gates, Thomas S.; Morgan, Roger J.; Thesken, John C.; Phoenix, S. Leigh

2006-01-01

368

Anisotropic Artificial Impedance Surfaces  

NASA Astrophysics Data System (ADS)

Anisotropic artificial impedance surfaces are a group of planar materials that can be modeled by the tensor impedance boundary condition. This boundary condition relates the electric and magnetic field components on a surface using a 2x2 tensor. The advantage of using the tensor impedance boundary condition, and by extension anisotropic artificial impedance surfaces, is that the method allows large and complex structures to be modeled quickly and accurately using a planar boundary condition. This thesis presents the theory of anisotropic impedance surfaces and multiple applications. Anisotropic impedance surfaces are a generalization of scalar impedance surfaces. Unlike the scalar version, anisotropic impedance surfaces have material properties that are dependent on the polarization and wave vector of electromagnetic radiation that interacts with the surface. This allows anisotropic impedance surfaces to be used for applications that scalar surfaces cannot achieve. Three of these applications are presented in this thesis. The first is an anisotropic surface wave waveguide which allows propagation in one direction, but passes radiation in the orthogonal direction without reflection. The second application is a surface wave beam shifter which splits a surface wave beam in two directions and reduces the scattering from an object placed on the surface. The third application is a patterned surface which can alter the scattered radiation pattern of a rectangular shape. For each application, anisotropic impedance surfaces are constructed using periodic unit cells. These unit cells are designed to give the desired surface impedance characteristics by modifying a patterned metallic patch on a grounded dielectric substrate. Multiple unit cell geometries are analyzed in order to find the setup with the best performance in terms of impedance characteristics and frequency bandwidth.

Quarfoth, Ryan Gordon

369

Determination of Residual Stress in Composite Materials Using Ultrasonic Waves  

NASA Technical Reports Server (NTRS)

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

Rokhlin, S. I.

1997-01-01

370

An enhanced Whipple Bumper system - Impact resistance of composite materials  

NASA Technical Reports Server (NTRS)

For long-duration space flights where human occupation is expected, micrometeroid and debris shields are necessary to prevent puncture of the pressure vessels. Current 'Whipple Bumper' designs range from single thin sheets of aluminum to complicated structures of many energy absorbing layers. This paper details the results of an experimental program tao determine the increased protection afforded by intermediate bumpers made of composite material structures. Various configurations of honeycomb support structures sandwiched between layers of materials such as Kevlar, Spectra, aluminum, and others are inserted between the bumper and pressure shell. The areal densities of each new material structure are maintained constant so that the results compare directly with single-sheet aluminum intermediate bumpers.

Zwiener, J.; Mount, A.; Herren, K.; Nettles, A.; Semmel, C.; Sims, J.

1992-01-01

371

Effective thermal conductivity of polycapillary composite materials. II. The influence of convective heat exchange in the channels on the effective thermal conductivity of polycapillary composite materials  

Microsoft Academic Search

In the preceding article [1], an analytical relationship making it possible to determine the effective transverse thermal conductivity X.y of polycapillary composite materials was obtained. This relationship establishes the relationship between Xy, the volumetric concentration and thermal conductivity of the components of a polycapillary composite material, and the geometric parameters of the structure of the material. In deriving the equation,

L. I. Tuchinskii; E. M. Veksler

1992-01-01

372

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

373

Compositions for enhancing hydroysis of cellulosic material by cellulolytic enzyme compositions  

DOEpatents

The present invention relates to compositions comprising a GH61 polypeptide having cellulolytic enhancing activity and an organic compound comprising a carboxylic acid moiety, a lactone moiety, a phenolic moiety, a flavonoid moiety, or a combination thereof, wherein the combination of the GH61 polypeptide having cellulolytic enhancing activity and the organic compound enhances hydrolysis of a cellulosic material by a cellulolytic enzyme compared to the GH61 polypeptide alone or the organic compound alone. The present invention also relates to methods of using the compositions.

Quinlan, Jason; Xu, Feng; Sweeney, Matthew; Johansen, Katja Salomon

2014-09-30

374

Study of polypyrrole graphite composite as anode material for secondary lithium-ion batteries  

E-print Network

Study of polypyrrole graphite composite as anode material for secondary lithium-ion batteries of the composite. The composite material has been studied for specific discharge capacity, coulombic efficiency, rate capability and cycle life using a variety of electrochemical methods. The composite SFG10 graphite

Popov, Branko N.

375

Composite materials comprising two jonal functions and methods for making the same  

Microsoft Academic Search

The present invention generally relates to mechanisms for preventing undesirable oxidation (i.e., oxidation protection mechanisms) in composite bodies. The oxidation protection mechanisms include getterer materials which are added to the composite body which gather or scavenge undesirable oxidants which may enter the composite body. The getterer materials may be placed into at least a portion of the composite body such

Ali Syed Fareed; John Edward Garnier; Gerhard Hans Schiroky; Christopher Robin Kennedy; Birol Sonuparlak

2001-01-01

376

Composite material shear property measurement using the Iosipescu specimen  

NASA Technical Reports Server (NTRS)

A detailed evaluation of the suitability of the Iosipescu specimen tested in the modified Wyoming fixture is presented. Finite element analysis and moire interferometry are used to assess the uniformity of the shear stress field in the test section of unidirectional and cross-ply graphite-epoxy composites. The nonuniformity of the strain field and the sensitivity of some fiber orientations to the specimen/fixture contact mechanics are discussed. The shear responses obtained for unidirectional and cross-ply graphite-epoxy composites are discussed and problems associated with anomalous behavior are addressed. An experimental determination of the shear response of a range of material systems using strain gage instrumentation and moire interferometry is performed.

Ho, Henjen; Budiman, Haryanto T.; Tsai, Ming-Yi; Morton, John; Farley, Gary L.

1992-01-01

377

Tuneable broadband optical filter based on soft-composite materials  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

378

Lightweight Impact-Resistant Composite Materials: Lessons from Mantis Shrimp  

NASA Astrophysics Data System (ADS)

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

Milliron, Garrett Wayne

379

Recycling By Solvolysis Thermosetting Composite Materials Of Sustainable Surface Transport  

SciTech Connect

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

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

2011-01-17

380

Super-hybrid composites - An emerging structural material  

NASA Technical Reports Server (NTRS)

Specimens of super-hybrids and advanced fiber composites were subjected to extensive tests to determine their mechanical properties, including impact and thermal fatigue. The super-hybrids were fabricated by a procedure similar to that reported by Chamis et al., (1975). Super-hybrids subjected to 1000 cycles of thermal fatigue from -100 to 300 F retained over 90% of their longitudinal flexural strength and over 75% of their transverse flexural strength; their transverse flexural strength may be as high as 8 times that of a commercially supplied boron/1100-Al composite. The thin specimen Izod longitudinal impact resistance of the super-hybrids was twice that of the boron/110-Al material. Super-hybrids subjected to transverse tensile loads exhibited nonlinear stress-strain relationships. The experimentally determined initial membrane (in-plane) and bending elastic properties of super-hybrids were predicted adequately by linear laminate analysis.

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

1975-01-01

381

Recycling By Solvolysis Thermosetting Composite Materials Of Sustainable Surface Transport  

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

382

Finite element analysis of composites materials for aerospace applications  

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

383

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

NASA Astrophysics Data System (ADS)

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

Hagedorn, Eric; Suskavcevic, Milijana

2007-10-01

384

Present and Future Automotive Composite Materials Research Efforts at DOE  

SciTech Connect

Automobiles of the future will be forced to travel fi.uther on a tank of fuel while discharging lower levels of pollutants. Currently, the United States uses in excess of 16.4 million barrels of petroleum per day. Sixty-six percent of that petroleum is used in the transportation of people and goods. Automobiles currently account for just under two-thirds of the nation's gasoline consumptio~ and about one-third of the total United States energy usage. [1] By improving transportation related fiel efficiency, the United States can lessen the impact that emissions have on our environment and provide a cleaner environment for fiture generations. In 1992, The Department of Energy's (DOE) Office of Transportation Materials completed a comprehensive program plan entitled, The Lightweight MateriaIs (LWko Multi-Year Program Plan, for the development of technologies aimed at reducing vehicle mass [2]. This plan was followed in 1997 by the more comprehensive Office of Advanced Automotive Technologies research and development plan titled, Energy Eficient Vehicles for a Cleaner Environment [3] which outlines the department's plans for developing more efficient vehicles during the next ~een years. Both plans identi~ potential applications, technology needs, and R&D priorities. The goal of the Lightweight Materials Program is to develop materials and primary processing methods for the fabrication of lighter weight components which can be incorporated into automotive systems. These technologies are intended to reduce vehicle weight, increase fuel efficiency and decrease emissions. The Lightweight Materials program is jointly managed by the Department of Energy(DOE) and the United States Automotive Materials Partnership (USAMP). Composite materiak program work is coordinated by cooperative research efforts between the DOE and the Automotive Composites Consortium (ACC).

Warren, C.D.

1999-07-03

385

Dynamic permeability in soft magnetic composite materials A. Chevalier and M. Le Floc'ha)  

E-print Network

Dynamic permeability in soft magnetic composite materials A. Chevalier and M. Le Floc on microwave ap- plications of composite materials consisting of soft magnetic particles embedded in insulating, the ability of the model to predict the dynamic properties of many composite magnetic materials

Paris-Sud XI, Université de

386

Compressive strength after blast of sandwich composite materials.  

PubMed

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

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

2014-05-13

387

Composite slip table of dissimilar materials for damping longitudinal modes  

DOEpatents

A vibration slip table for use in a vibration testing apparatus is disclosed. The tables comprised of at least three composite layers of material; a first metal layer, a second damping layer, and a third layer having a high acoustic velocity relative to the first layer. The different acoustic velocities between the first and third layers cause relative shear displacements between the layers with the second layer damping the displacements between the first and third layers to reduce the table longitudinal vibration modes. 6 figures.

Gregory, D.L.; Priddy, T.G.; Smallwood, D.O.; Woodall, T.D.

1991-06-18

388

Collagen hydrolysate based collagen/hydroxyapatite composite materials  

NASA Astrophysics Data System (ADS)

The aim of this study was to study the influence of collagen hydrolysate (HAS) on the formation of ternary collagen-hydrolysate/hydroxyapatite composite materials (COLL-HAS/HA). During the precipitation process of HA, a large amount of brushite is resulted at pH = 7 but, practically pure HA is obtained at pH ? 8. The FTIR data reveal the duplication of the most important collagen absorption bands due to the presence of the collagen hydrolysate. The presence of collagen hydrolysate is beneficial for the management of bone and joint disorders such as osteoarthritis and osteoporosis.

Ficai, Anton; Albu, Madalina Georgiana; Birsan, Mihaela; Sonmez, Maria; Ficai, Denisa; Trandafir, Viorica; Andronescu, Ecaterina

2013-04-01

389

Pressure-reaction synthesis of titanium composite materials  

DOEpatents

A pressure-reaction synthesis process for producing increased stiffness and improved strength-to-weight ratio titanium metal matrix composite materials comprising exothermically reacting a titanium powder or titanium powder alloys with non-metal powders or gas selected from the group consisting of C, B, N, BN, B.sub.4 C, SiC and Si.sub.3 N.sub.4 at temperatures from about 900.degree. to about 1300.degree. C., for about 5 to about 30 minutes in a forming die under pressures of from about 1000 to 5000 psi.

Oden, Laurance L. (Albany, OR); Ochs, Thomas L. (Albany, OR); Turner, Paul C. (Albany, OR)

1993-01-01

390

Numerical analysis of the Iosipescu specimen for composite materials  

NASA Technical Reports Server (NTRS)

A finite element analysis of the Iosipescu shear tests for unidirectional and cross-ply composites is presented. It is shown that an iterative analysis procedure must be used to model the fixture-specimen kinematics. The correction factors which are needed to compensate for the nonuniformity of stress distribution in calculating shear modulus are shown to be dependent on the material orthotropic ratio and the finite element loading models. Test section strain distributions representative of typical graphite-epoxy specimens are also presented.

Ho, H.; Tsai, M. Y.; Morton, J.; Farley, G. L.

1993-01-01

391

Numerical analysis of the Iosipescu specimen for composite materials  

NASA Technical Reports Server (NTRS)

A finite element analysis of the Iosipescu shear tests for unidirectional and cross-ply composites is presented. It is shown that an iterative analysis procedure must be used to model the fixture-specimen kinematics. The correction factors which are needed to compensate for the nonuniformity of stress distribution in calculating shear modulus are shown to be dependent on the material orthotropic ratio and the finite element loading models. Test section strain distributions representative of typical graphite-epoxy specimens are also presented.

Ho, H.; Tsai, M. Y.; Morton, J.; Farley, G. L.

1992-01-01

392

Composite material including nanocrystals and methods of making  

SciTech Connect

Temperature-sensing compositions can include an inorganic material, such as a semiconductor nanocrystal. The nanocrystal can be a dependable and accurate indicator of temperature. The intensity of emission of the nanocrystal varies with temperature and can be highly sensitive to surface temperature. The nanocrystals can be processed with a binder to form a matrix, which can be varied by altering the chemical nature of the surface of the nanocrystal. A nanocrystal with a compatibilizing outer layer can be incorporated into a coating formulation and retain its temperature sensitive emissive properties

Bawendi, Moungi G. (Boston, MA); Sundar, Vikram C. (New York, NY)

2008-02-05

393

Nonequilibrium material effects on the behavior of polymeric composite matrices and their related composites  

NASA Technical Reports Server (NTRS)

The effects of physical aging on the material properties of some linear and network macromolecular glasses are discussed. The free volume concept is used to describe this behavior. The effect of physical aging on properties of some uniaxial graphite/fiber epoxy resin composites is investigated using stress relaxation in both tensile and flexural modes. The matrix polymers used were resins both of which are based on a 4,4-methylenedianiline derivative of epichlorohydrin with diamino diphenyl sulfone (DDS) as the curing agent. The matrix resin, as used in the practical application in composites, not fully cured and the glass transition of the network was dependent on the curing schedule. The physical aging of the bulk crosslinked epoxy was found to depend on the annealing temperature, and the T sub g of the resin. The physical aging of the composite, monitored by the stress relaxation method, was found to be dependent on the testing direction.

Wilkes, G. L.

1982-01-01

394

Investigation of composite materials property requirements for sonic fatigue research  

NASA Technical Reports Server (NTRS)

Experimental techniques for determining the extensional and bending stiffness characteristics for symmetric laminates are presented. Vibrational test techniques for determining the dynamic modulus and material damping are also discussed. Partial extensional stiffness results intially indicate that the laminate theory used for predicting stiffness is accurate. It is clearly shown that the laminate theory can only be as accurate as the physical characteristics describing the lamina, which may vary significantly. It is recommended that all of the stiffness characteristics in both extension and bending be experimentally determined to fully verify the laminate theory. Dynamic modulus should be experimentally evaluated to determine if static data adequately predicts dynamic behavior. Material damping should also be ascertained because laminate damping is an order of magnitude greater than found in common metals and can significantly effect the displacement response of composite panels.

Patrick, H. V. L.

1985-01-01

395

Mixed composition materials suitable for vacuum web sputter coating  

NASA Technical Reports Server (NTRS)

Ion beam sputter deposition techniques were used to investigate simultaneous sputter etching of two component targets so as to produce mixed composition films. Although sputter deposition has been largely confined to metals and metal oxides, at least one polymeric material, poly-tetra-fluorethylene, has been demonstrated to produce sputtered fragments which repolymerize upon deposition to produce a highly cross-linked fluoropolymer resembling that of the parent target Fluoropolymer-filled silicon dioxide and fluoropolymer-filled aluminum oxide coatings have been deposited by means of ion beam sputter coat deposition resulting in films having material properties suitable for aerospace and commercial applications. The addition of fluoropolymer to silicon dioxide films was found to increase the hydrophobicity of the resulting mixed films; however, adding fluoropolymer to aluminum oxide films resulted in a reduction in hydrophobicity, thought to be caused by aluminum fluoride formation.

Banks, Bruce A.; Rutledge, Sharon K.; Dever, Joyce A.; Bruckner, Eric J.; Walters, Patricia; Hambourger, Paul D.

1996-01-01

396

Environmental exposure effects on composite materials for commercial aircraft  

NASA Technical Reports Server (NTRS)

The effects of environmental exposure on composite materials are determined. The environments considered are representative of those experienced by commercial jet aircraft. Initial results have been compiled for the following material systems: T300/5208, T300/5209, and T300/934. Future results will include AS-1/3501-6 and Kevlar 49/F161-188. Specimens are exposed on the exterior and interior of 737 airplanes of three airlines, and to continuous ground-level exposure at four locations. In addition, specimens are exposed in the laboratory to conditions such as: simulated ground-air-ground, weatherometer, and moisture. Residual strength results are presented for specimens exposed for up to five years at five ground-level exposure locations and on airplanes from one airline.

Coggeshall, R. L.

1985-01-01

397

Selection of optimal composition-control parameters for friable materials  

SciTech Connect

A method for composition analysis of coal and minerals is proposed which uses scattered gamma radiation and does away with preliminary sample preparation to ensure homogeneous particle density, surface area, and size. Reduction of the error induced by material heterogeneity has previously been achieved by rotation of the control object during analysis. A further refinement is proposed which addresses the necessity that the contribution of the radiation scattered from each individual surface to the total intensity be the same. This is achieved by providing a constant linear rate of travel for the irradiated spot through back-and-forth motion of the sensor. An analytical expression is given for the laws of motion for the sensor and test tube which provides for uniform irradiated area movement along a path analogous to the Archimedes spiral. The relationships obtained permit optimization of measurement parameters in analyzing friable materials which are not uniform in grain size.

Pak, Yu.N.; Vdovkin, A.V.

1988-05-01

398

Composites  

NSDL National Science Digital Library

In this activity, learners explore how composites work by creating and testing their own composite for an imaginary company. This activity shows learners that composites are simply materials that are made up of two or more visibly distinct substances. Use this activity to talk about how composites are everywhere in our lives.

Research, Cornell C.

2003-01-01

399

Smart composite materials for non-invasive structural health monitoring and composites manufacturing process monitoring  

NASA Astrophysics Data System (ADS)

Self-sensing composite materials with nanoscale sensor networks can provide feedback about quality evolution during composites manufacturing as well as long-term structural health. Multi-scale composites spanning nano to macro scales involve the interaction between components of varying length scales. An example of such an interaction is the influence of hollow glass microspheres on the electrical conductivity and strain sensitivity of novel carbon nanotube-based syntactic foams. In addition to uniformly dispersed carbon nanotube networks, selective integration of carbon nanotubes has been studied in form of carbon nanotube sheets and carbon nanotube sizing agents. Both techniques enable one-step carbon nanotube integration. Carbon nanotube sheets have been found to be especially useful for prepreg composites. In addition to piezoresistive-based sensing, time domain reflectometry has been studied and the strain response of time domain reflectometry sensors has been modeled and validated. Carbon nanotubes have been found to increase the strain response and damage sensitivity of time domain reflectometry sensors due to breakage of carbon nanotube networks. Two-dimensional deformation mapping and damage sensing has been implemented on composite panels using both piezoresistivity and time domain reflectometry. For the first time, high accuracy cure monitoring has been achieved using non-invasive time domain reflectometry sensors.

Pandey, Gaurav

400

Impact damage analysis of balsawood sandwich composite materials  

NASA Astrophysics Data System (ADS)

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

Abdalslam, Suof Omran

401

Thermophysical characterization of composite materials under transient heating conditions  

NASA Technical Reports Server (NTRS)

Thermophysical property measurements were made under transient heating conditions on several materials being considered for use in SCOUT rocket motors. The materials included were ATJ graphite, MX 2600 silica phenolic, FM 5272 cellulose phenolic, and two carbon-carbon composites: CARBITEX 700 and RPP-4. The ATJ was included as a reference or base line material to check performance of the transient tests as it was not expected to be sensitive to heating rate. Measurements included in the program were thermal conductivity, strength, compressive stress-strain (carbon-carbon only), thermal expansion and the effective thermal expansion under partially restrained conditions. Development of this latter measurement was a major part of the program. It consisted of partially restraining the expansion of a specimen as it was heated, measuring the load and strain which occurred (together with a simultaneous modulus determination by superimposing a small cyclic load) and using these quantities to calculate what the effective thermal expansion would have to be to produce the observed stress and deformation. For materials which are sensitive to heating rate, such as reinforced phenolics, it was believed that this would provide a more realistic determination of the thermal expansion as it more nearly simulates the conditions experienced in end use.

Roetling, J.; Hanson, J.

1972-01-01

402

Application of advanced material systems to composite frame elements  

NASA Technical Reports Server (NTRS)

A three phase program has been conducted to investigate DuPont's Long Discontinuous Fiber (LDF) composites. Additional tests were conducted to compare LDF composites against toughened thermosets and a baseline thermoset system. Results have shown that the LDF AS4/PEKK offers improved interlaminar (flange bending) strength with little reduction in mechanical properties due to the discontinuous nature of the fibers. In the third phase, a series of AS4/PEKK LDF C-section curved frames (representing a typical rotorcraft light frame) were designed, manufactured and tested. Specimen reconsolidation after 'stretch forming' and frame thickness were found to be key factors in this light frame's performance. A finite element model was constructed to correlate frame test results with expected strain levels determined from material property tests. Adequately reconsolidated frames performed well and failed at strain levels at or above baseline thermoset material test strains. Finally a cost study was conducted which has shown that the use of LDF for this frame would result in a significant cost savings, for moderate to large lot sizes compared with the hand lay-up of a thermoset frame.

Llorente, Steven; Minguet, Pierre; Fay, Russell; Medwin, Steven

1992-01-01

403

Dynamic fracture of functionally graded magnetoelectroelastic composite materials  

NASA Astrophysics Data System (ADS)

The stress, magnetic and electric field analysis of multifunctional composites, weakened by impermeable cracks, is of fundamental importance for their structural integrity and reliable service performance. The aim is to study dynamic behavior of a plane of functionally graded magnetoelectroelastic composite with more than one crack. The coupled material properties vary exponentially in an arbitrary direction. The plane is subjected to anti-plane mechanical and in-plane electric and magnetic load. The boundary value problem described by the partial differential equations with variable coefficients is reduced to a non-hypersingular traction boundary integral equation based on the appropriate functional transform and frequency-dependent fundamental solution derived in a closed form by Radon transform. Software code based on the boundary integral equation method (BIEM) is developed, validated and inserted in numerical simulations. The obtained results show the sensitivity of the dynamic stress, magnetic and electric field concentration in the cracked plane to the type and characteristics of the dynamic load, to the location and cracks disposition, to the wave-crack-crack interactions and to the magnitude and direction of the material gradient.

Stoynov, Y.; Dineva, P.

2014-11-01

404

Fabricating Composite-Material Structures Containing SMA Ribbons  

NASA Technical Reports Server (NTRS)

An improved method of designing and fabricating laminated composite-material (matrix/fiber) structures containing embedded shape-memory-alloy (SMA) actuators has been devised. Structures made by this method have repeatable, predictable properties, and fabrication processes can readily be automated. Such structures, denoted as shape-memory-alloy hybrid composite (SMAHC) structures, have been investigated for their potential to satisfy requirements to control the shapes or thermoelastic responses of themselves or of other structures into which they might be incorporated, or to control noise and vibrations. Much of the prior work on SMAHC structures has involved the use SMA wires embedded within matrices or within sleeves through parent structures. The disadvantages of using SMA wires as the embedded actuators include (1) complexity of fabrication procedures because of the relatively large numbers of actuators usually needed; (2) sensitivity to actuator/ matrix interface flaws because voids can be of significant size, relative to wires; (3) relatively high rates of breakage of actuators during curing of matrix materials because of sensitivity to stress concentrations at mechanical restraints; and (4) difficulty of achieving desirable overall volume fractions of SMA wires when trying to optimize the integration of the wires by placing them in selected layers only.

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

2003-01-01

405

Effect of fiber and matrix maximum strain on the energy absorption of composite materials  

NASA Technical Reports Server (NTRS)

Static crushing tests were conducted on graphite composite tubes to examine the influence of fiber and matrix maximum strain at failure on the energy absorption capability of graphite reinforced composite material. Fiber and matrix maximum strain at failure were determined to significantly effect energy absorption. The higher strain at failure composite material system, AS-4/5245, exhibited superior energy absorption capability compared to AS-4/934, T300/5245 or T300/934 composite material. Results of this investigation suggest that to achieve maximum energy absorption from a composite material a matrix material that has a higher strain at failure than the fiber reinforcement should be used.

Farley, G. L.

1985-01-01

406

A normalization method for life-time prediction of composite materials  

E-print Network

Introduction Industrials are increasingly using more composite materi- als in various fields particularly in aviation and automobiles fields. Their great advantage is their strength and stiffness associated are given. 2 Materials and test 2.1 Materials The studied materials were manufactured by moulding composite

Paris-Sud XI, Université de

407

2014 Global Conference on Polymer and Composite Materials (PCM 2014)  

NASA Astrophysics Data System (ADS)

The 2014 Global Conference on Polymer and Composite Materials (PCM 2014) sponsored by Ningbo Adhesives and Products Industry Association, Shanghai Bonding Technology Association, Zhejiang Bonding Technology Association, Wuhan Bonding Technology Association, Hebei Bonding and Coatings Association and Polyurethane Industry Association was held from May 27 to May 29 2014 in Ningbo, China. The technical program consisted of 8 international keynote speakers, oral presentations, and a poster session. The conference also included an industrial exhibition where more than 50 companies displayed in their booths their most recent advanced products and services. The present issue of IOP Conference Series: Materials Science and Engineering (MSE) records the proceedings of PCM 2014 and contains 37 specially selected manuscripts submitted to PCM2014 conference. The electronic submission and handling of manuscripts via the conference website, including the selection of reviewers and evaluation of manuscripts, were identical to the procedures applied to manuscripts submitted as regular contributions for publication. The organization of this conference and the preparation of proceedings volumes would have been impossible without the tremendous efforts and dedication of many individuals, especially from Ms. Yin Pan, who oversaw the organization of the conference and the program; and a large team of reviewers with their timely submission of quality reports. We express our sincere thanks to all authors and presenters for their contributions. We also thank very much our sponsors for their generous support. The 2015 Global Conference on Polymer and Composite Materials (PCM2015) will be held in Beijing, China on May 16-18, 2015. Beijing, the capital of the People's Republic of China and one of the most populous cities in the world, will welcome to all participants for a renewed and vibrant conference. Prof. Dr. Esteban Broitman Linköping University, Sweden Editor in Chief — PCM2014

2014-08-01

408

Thermal Diffusivity and Conductivity in Ceramic Matrix Fiber Composite Materials - Literature Study  

SciTech Connect

A technical literature review was conducted to gain an understanding of the state of the art method, problems, results, and future of thermal diffusivity/conductivity of matrix-fiber composites for high temperature applications. This paper summarizes the results of test method development and theory. Results from testing on various sample types are discussed with concentration on the anisotropic characteristics of matrix-fiber composites, barriers to heat flow, and notable microstructure observations. The conclusion presents some observations from the technical literature, drawbacks of current information and discusses potential needs for future testing.

R.G. Quinn

2000-05-02

409

Thermal Energy in Carbon Nanotube and Graphene Composite Materials  

NASA Astrophysics Data System (ADS)

Low-dimensional materials, like carbon nanotubes (CNTs) and graphene, possess extraordinary properties---higher thermal conductivity than any bulk material, mechanical strength 10-100 times greater than steel on a mass basis, and electrical current capacity 1000 times greater than copper. While composites incorporating these low-dimensional materials promise solutions to global sustainability challenges, significant transport barriers exist at the matrix interface that influence the composite properties. My PhD research sought to address this knowledge gap. I've experimentally explored how CNTs and graphene impact thermal conductivity when added in small volume fractions to gases, liquids and solids through the study of CNT aerogels (ultra lightweight, 8 kg/m3, 99.6% void space), and phase change nanocomposites (hexadecane-graphene). I measured the thermal conductivity of the CNT aerogel with various filling gases versus pressure using a novel technique that targeted ultralow thermal conductivity materials, called metal-coated 3o. I observed amplified energy transport length scales resulting from low gas accommodation, which is a general feature of carbon based nanoporous materials. Our evidence also shows that despite the high thermal conductivity of CNTs, thermal conduction through the CNT network is limited by the high thermal boundary resistance at van der Waals bonded CNT junctions. In the second system, I studied thermal and electrical conductivity of hexadecane- multi-layered-graphene (MLG) phase change nanocomposites to understand how morphology of the MLG network impacts transport. By adjusting the freezing rate, the electrical conductivity in the solid phase can be tuned between 1 and 5 orders-of-magnitude and the solid-liquid thermal conductivity ratio can be varied between 2.6 to 3.0. This research has yielded interesting insights into the tunability of nanocomposites and the physics underlying it, including evidence to indicate that the presence of graphene actually enhances the thermal conductivity of the hexadecane itself. Future work here might address how the graphene influences the properties of the hexadecane.

Schiffres, Scott N.

410

Composition and method for removing photoresist materials from electronic components  

DOEpatents

The invention is a combination of at least one dense phase fluid and at least one dense phase fluid modifier which can be used to contact substrates for electronic parts such as semiconductor wafers or chips to remove photoresist materials which are applied to the substrates during manufacture of the electronic parts. The dense phase fluid modifier is one selected from the group of cyclic, aliphatic or alicyclic compounds having the functional group: ##STR1## wherein Y is a carbon, oxygen, nitrogen, phosphorus or sulfur atom or a hydrocarbon group having from 1 to 10 carbon atoms, a halogen or halogenated hydrocarbon group having from 1 to 10 carbon atoms, silicon or a fluorinated silicon group; and wherein R.sub.1 and R.sub.2 can be the same or different substituents; and wherein, as in the case where X is nitrogen, R.sub.1 or R.sub.2 may not be present. The invention compositions generally are applied to the substrates in a pulsed fashion in order to remove the hard baked photoresist material remaining on the surface of the substrate after removal of soft baked photoresist material and etching of the barrier layer.

Davenhall, Leisa B. (Santa Fe, NM); Rubin, James B. (Los Alamos, NM)

2002-01-01

411

Reinforcements: The key to high performance composite materials  

NASA Technical Reports Server (NTRS)

Better high temperature fibers are the key to high performance, light weight composite materials. However, current U.S. and Japanese fibers still have inadequate high temperature strength, creep resistance, oxidation resistance, modulus, stability, and thermal expansion match with some of the high temperature matrices being considered for future aerospace applications. In response to this clear deficiency, both countries have research and development activities underway. Once successful fibers are identified, their production will need to be taken from laboratory scale to pilot plant scale. In such efforts it can be anticipated that the Japanese decisions will be based on longer term criteria than those applied in the U.S. Since the initial markets will be small, short term financial criteria may adversely minimize the number and strength of U.S. aerospace materials suppliers to well into the 21st century. This situation can only be compounded by the Japanese interests in learning to make commercial products with existing materials so that when the required advanced fibers eventually do arrive, their manufacturing skills will be developed.

Grisaffe, Salvatore J.

1990-01-01

412

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

SciTech Connect

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

Cuenca, Jacques, E-mail: jcuenca@kth.se; Van der Kelen, Christophe; Göransson, Peter [Marcus Wallenberg Laboratory for Sound and Vibration Research, Royal Institute of Technology (KTH), Teknikringen 8, SE-10044 Stockholm (Sweden)

2014-02-28

413

Electrochemical performance of sulfur composite cathode materials for rechargeable lithium batteries  

Microsoft Academic Search

The structure and characteristic of carbon materials have a direct influence on the electrochemical performance of sulfur–carbon composite electrode materials for lithium–sulfur battery. In this paper, sulfur composite has been synthesized by heating a mixture of elemental sulfur and activated carbon, which is characterized as high specific surface area and microporous structure. The composite, contained 70% sulfur, as cathode in

Feng Wu; Sheng Xian Wu; Ren Jie Chen; Shi Chen; Guo Qing Wang

2009-01-01

414

On the Use of Composite Charges to Determine Insensitive Explosive Material Properties at the Laboratory Scale  

E-print Network

Full Paper On the Use of Composite Charges to Determine Insensitive Explosive Material Properties explosive charges are presented. The composite charges con- sist of a spherical booster charge surrounded by a concentric, spherical "candidate material" shell charge. By way of composite charge explosive

Settles, Gary S.

415

Preparation, characterization and application of the magadiite based mesoporous composite material of catalytic interest  

Microsoft Academic Search

The synthesis of a new type of mesoporous materials by intercalation of silica between magadiite layers was carried out. For the preparation of the composite material, reactive silica gels with compositions characteristic for the synthesis of MCM-41 were used. Samples synthesized with various compositions were characterized by X-ray diffraction, IR and NMR spectroscopy, thermal analysis, BET measurements as well as

Á. Fudala; Z. Kónya; Y. Kiyozumi; S.-I. Niwa; M. Toba; F. Mizukami; P. B. Lentz; J. Nagy; I. Kiricsi

2000-01-01

416

NUMERICAL EVALUATION OF SINGLE FIBER MOTION FOR SHORT-FIBER-REINFORCED COMPOSITE MATERIALS PROCESSING  

E-print Network

1 NUMERICAL EVALUATION OF SINGLE FIBER MOTION FOR SHORT-FIBER-REINFORCED COMPOSITE MATERIALS fibers are derived in this paper. Keywords: Jeffery's orbit, short-fiber-reinforced composite material Mechanical properties of short-fiber-reinforced composite systems are largely dependent on the fiber

Montgomery-Smith, Stephen

417

Numerical Simulation of Delamination Growth in Composite Materials  

NASA Technical Reports Server (NTRS)

The use of decohesion elements for the simulation of delamination in composite materials is reviewed. The test methods available to measure the interfacial fracture toughness used in the formulation of decohesion elements are described initially. After a brief presentation of the virtual crack closure technique, the technique most widely used to simulate delamination growth, the formulation of interfacial decohesion elements is described. Problems related with decohesion element constitutive equations, mixed-mode crack growth, element numerical integration and solution procedures are discussed. Based on these investigations, it is concluded that the use of interfacial decohesion elements is a promising technique that avoids the need for a pre-existing crack and pre-defined crack paths, and that these elements can be used to simulate both delamination onset and growth.

Camanho, P. P.; Davila, C. G.; Ambur, D. R.

2001-01-01

418

Aluminum Foam-Phase Change Material Composites as Heat Exchangers  

SciTech Connect

The effects of geometric parameters of open-cell aluminum foams on the performance of aluminum foam-phase change material (PCM) composites as heat sinks are investigated by experiments. Three types of open-cell aluminum 6061 foams with similar relative densities and different cell sizes are used. Paraffin is selected as the PCM due to its excellent thermal stability and ease of handling. The experimental results show that the performance of the heat sink is significantly affected by the surface area density of the aluminum foam. In general, as the surface area density of the foam increases, the performance of the heat sink is improved regardless of the current phase of the PCM.

Hong, Sung-tae; Herling, Darrell R.

2007-04-07

419

Study of the influence of hole quality on composite materials  

NASA Technical Reports Server (NTRS)

The influence of hole quality on the structural behavior of composite materials was investigated. From an industry survey it was determined that the most frequent imperfections encountered during hole fabrication are chipout, delamination, and oversize conditions. These hole flaw types were generated in critical areas of static, compression, and fatigue specimens fabricated from T300/5208 graphite/epoxy system. The specimens were tested in static and cyclic pin bearing modes in addition to compression loading. Results of these tests are presented and discussed. The hole chipout defect reduced the static and cyclic endurance characteristics. Oversize holes also lowered the cyclic pin bearing endurance, but had no influence of the static pin bearing characteristics. Delamination had no insignificant influence on the static tension and cyclic pin bearing characteristics. Compression tests demonstrated a deleterious effect for chipout of delamination defects. Hole quality requirements proposed are discussed.

Pengra, J. J.

1980-01-01

420

Nanoengineered thermal materials based on carbon nanotube array composites  

NASA Technical Reports Server (NTRS)

A method for providing for thermal conduction using an array of carbon nanotubes (CNTs). An array of vertically oriented CNTs is grown on a substrate having high thermal conductivity, and interstitial regions between adjacent CNTs in the array are partly or wholly filled with a filler material having a high thermal conductivity so that at least one end of each CNT is exposed. The exposed end of each CNT is pressed against a surface of an object from which heat is to be removed. The CNT-filler composite adjacent to the substrate provides improved mechanical strength to anchor CNTs in place and also serves as a heat spreader to improve diffusion of heat flux from the smaller volume (CNTs) to a larger heat sink.

Li, Jun (Inventor); Meyyappan, Meyya (Inventor)

2007-01-01

421

Nanoengineered thermal materials based on carbon nanotube array composites  

NASA Technical Reports Server (NTRS)

A method for providing for thermal conduction using an array of carbon nanotubes (CNTs). An array of vertically oriented CNTs is grown on a substrate having high thermal conductivity, and interstitial regions between adjacent CNTs in the array are partly or wholly filled with a filler material having a high thermal conductivity so that at least one end of each CNT is exposed. The exposed end of each CNT is pressed against a surface of an object from which heat is to be removed. The CNT-filler composite adjacent to the substrate provides improved mechanical strength to anchor CNTs in place and also serves as a heat spreader to improve diffusion of heat flux from the smaller volume (CNTs) to a larger heat sink.

Li, Jun (Inventor); Meyyappan, Meyya (Inventor); Dangelo, Carlos (Inventor)

2010-01-01

422

Nanoengineered Thermal Materials Based on Carbon Nanotube Array Composites  

NASA Technical Reports Server (NTRS)

A method for providing for thermal conduction using an array of carbon nanotubes (CNTs). An array of vertically oriented CNTs is grown on a substrate having high thermal conductivity, and interstitial regions between adjacent CNTs in the array are partly or wholly filled with a filler material having a high thermal conductivity so that at least one end of each CNT is exposed. The exposed end of each CNT is pressed against a surface of an object from which heat is to be removed. The CNT-filler composite adjacent to the substrate provides improved mechanical strength to anchor CNTs in place and also serves as a heat spreader to improve diffusion of heat flux from the smaller volume (CNTs) to a larger heat sink.

Li, Jun (Inventor); Meyyappan, Meyya (Inventor)

2007-01-01

423

Health Monitoring of Composite Material Structures using a Vibrometry Technique  

NASA Technical Reports Server (NTRS)

Large composite material structures such as aircraft and Reusable Launch Vehicles (RLVS) operate in severe environments comprised of vehicle dynamic loads, aerodynamic loads, engine vibration, foreign object impact, lightning strikes, corrosion, and moisture absorption. These structures are susceptible to damage such as delamination, fiber breaking/pullout, matrix cracking, and hygrothermal strain. To ensure human safety and load-bearing integrity, these structures must be inspected to detect and locate often invisible damage and faults before becoming catastrophic. Moreover, nearly all future structures will need some type of in-service inspection technique to increase their useful life and reduce maintenance and overall costs. Possible techniques for monitoring the health and indicating damage on composite structures include: c-scan, thermography, acoustic emissions using piezoceramic actuators or fiber-optic wires with gratings, laser ultrasound, shearography, holography, x-ray, and others. These techniques have limitations in detecting damage that is beneath the surface of the structure, far away from a sensor location, or during operation of the vehicle. The objective of this project is to develop a more global method for damage detection that is based on structural dynamics principles, and can inspect for damage when the structure is subjected to vibratory loads to expose faults that may not be evident by static inspection. A Transmittance Function Monitoring (TFM) method is being developed in this project for ground-based inspection and operational health monitoring of large composite structures as a RLV. A comparison of the features of existing health monitoring approaches and the proposed TFM method is given.

Schulz, Mark J.

1997-01-01

424

Microstructure characterization of multi-phase composites and utilization of phase change materials and recycled rubbers in cementitious materials  

NASA Astrophysics Data System (ADS)

This research focuses on two important subjects: (1) Characterization of heterogeneous microstructure of multi-phase composites and the effect of microstructural features on effective properties of the material. (2) Utilizations of phase change materials and recycled rubber particles from waste tires to improve thermal properties of insulation materials used in building envelopes. Spatial pattern of multi-phase and multidimensional internal structures of most composite materials are highly random. Quantitative description of the spatial distribution should be developed based on proper statistical models, which characterize the morphological features. For a composite material with multi-phases, the volume fraction of the phases as well as the morphological parameters of the phases have very strong influences on the effective property of the composite. These morphological parameters depend on the microstructure of each phase. This study intends to include the effect of higher order morphological details of the microstructure in the composite models. The higher order statistics, called two-point correlation functions characterize various behaviors of the composite at any two points in a stochastic field. Specifically, correlation functions of mosaic patterns are used in the study for characterizing transport properties of composite materials. One of the most effective methods to improve energy efficiency of buildings is to enhance thermal properties of insulation materials. The idea of using phase change materials and recycled rubber particles such as scrap tires in insulation materials for building envelopes has been studied.

Meshgin, Pania

2011-12-01

425

Ceramic Matrix Composite Cooled Nozzle Material Development Program  

NASA Technical Reports Server (NTRS)

The X-33 program initiated a risk reduction technology project to develop an actively cooled cermic matrix composite (CMC) nozzle ramp for the linear aerospike engine. The objective was to reduce the weight and increase the operating temperature capabilities of the nozzle ramp. A complement to this original project was subsequently supported by NASA's Second Generation Reusable Launch Vehicle Program to develop a high risk high payoff cooled composite nozzle ramp. This project focused on less mature technologies and concepts having the potential to achieve a significant weight reduction beyond those systems which were being considered in the original X-33 project. The aerospike engine was not selected under the initial Space Launch Initiative (SLI) Program research announcement. However, in recognition of the tremendous application opportunities of such technology to other areas and systems in the rocket industry, the effort was continued and is in the process of being transferred to the 3rd Generation Reusable Launch Vehicle (RLV) Program where it will be combined with the current cooled CMC panel project. The objective of the refocused project is to advance the material, design, and analysis work on the ramp concepts to a point that would allow the selection of the most promising candidate(s) for continued development. The concept(s) carried on in the 3rd Generation RLV Program will be modified to address the goals of this program. Originally, four contracts with different design concepts were initiated. Each contractor has performed design and analysis of their concept and submitted a subscale component for testing in the Cell 22 test rig at Glenn Research Center. This paper will discuss the results to date of each design concept and the potential applications to future rocket nozzle systems. The engineering technology challenges for each concept were determined and addressed during this phase of the effort. These challenges and the success in addressing them will also be discussed. High temperature, noneroding nozzle materials have the potential to significantly improve nozzle performance. The work performed under this effort is at the forefront of CMC material development and will give the rocket nozzle community a good view into the status of cooled CMC materials.

Lawrence, Tim; Eckel, Andy; Porter, John; Pichon, T.; Patterson, B.; Paquette, T.

2002-01-01

426

The Abundance and Isotopic Composition of Hg in Extraterrestrial Materials  

NASA Technical Reports Server (NTRS)

During the three year grant period we made excellent progress in our study of the abundances and isotopic compositions of Hg and other volatile trace elements in extraterrestrial materials. At the time the grant started, our collaborating PI, Dante Lauretts, was a postdoctoral research associate working with Peter Buseck at Arizona State University. The work on chondritic Hg was done in collaboration with Dante Lauretta and Peter Buseck and this study was published in Lauretta et a1 (2001a). In July, 2001 Dante Lauretta accepted a position as an Assistant Professor in the Lunar and Planetary Laboratory at the University of Arizona. His funding was transferred and this grant has supported much of his research activities during his first two years at the U of A. Several other papers are in preparation and will be published soon. We presented papers on this topic at Goldschmidt Conferences, the Lunar and Planetary Science Conferences, and the Annual Meetings of the Meteoritical Society. The work done under this grant has spurred several new directions of inquiry, which we are still pursuing. Included in this paper are the studies of bulk abundances and isotopic compositions of metreoritic Mercury, and the development of a thermal analysis ICP-MS technique applied to thermally liable elements.

Blum, J. D.; Klaue, Bjorn

2005-01-01

427

Mechanistic Effects of Porosity on Structural Composite Materials  

NASA Astrophysics Data System (ADS)

As fiber reinforced composites continue to gain popularity as primary structures in aerospace, automotive, and powersports industries, quality control becomes an extremely important aspect of materials and mechanical engineering. The ability to recognize and control manufacturing induced defects can greatly reduce the likelihood of unexpected catastrophic failure. Porosity is the result of trapped volatiles or air bubbles during the layup process and can significantly compromise the strength of fiber reinforced composites. A comprehensive study was performed on an AS4C-UF3352 TCR carbon fiber-epoxy prepreg system to determine the effect of porosity on flexural, shear, low-velocity impact, and damage residual strength properties. Autoclave cure pressure was controlled to induce varying levels of porosity to construct six laminates with porosity concentrations between 0-40%. Porosity concentrations were measured using several destructive and nondestructive techniques including resin burnoff, sectioning and optical analysis, and X-ray computed tomography (CT) scanning. Ultrasonic transmission, thermography, and CT scanning provided nondestructive imaging to evaluate impact damage. A bilinear relationship accurately characterizes the change in mechanical properties with increasing porosity. Strength properties are relatively unaffected when porosity concentrations are below approximately 2.25% and decrease linearly by up to 40% in high porosity specimens.

Siver, Andrew

428

Permeability testing of composite material and adhesive bonds for the DC-XA composite feedline program  

NASA Technical Reports Server (NTRS)

Hercules IM7/8552 carbon/epoxy and Hysol EA 9394 epoxy adhesive bonded between composite/titanium were tested for permeability after various numbers of thermal cycles between 100 C and liquid nitrogen (-196 C). The specimens were quenched from the 100 C temperature into liquid nitrogen to induce thermal shock into the material. Results showed that the carbon/epoxy system was practically impermeable even after 12 thermal cycles. The EA 9394 adhesive bondline was more permeable than the carbon/epoxy, but vacuum mixing minimized the permeability and kept it within allowable limits. Thermal cycling had little effect on the permeability values of the bondline specimens.

Nettles, A. T.

1995-01-01

429

Inhibition of catalytic oxidation of carbon/carbon composite materials  

NASA Astrophysics Data System (ADS)

An investigation coupling experimental efforts with computational chemistry analysis was conducted to study the inhibition effects of phosphorous or boron on the oxidation of carbon/carbon composite materials catalyzed by potassium or calcium acetate (KAC or CaAC). Commercial aircraft brakes were used, which are exposed during use to K- or Ca-containing runway deicing agents. The reactivity of inhibitor-doped carbon materials was determined by temperature programmed oxidation (TPO) and isothermal oxidation in 1 atm O2. The structure and surface chemistry of inhibitor-doped samples were characterized, and the inhibition mechanisms were explored with the help of ab initio molecular orbital calculations. The catalytic effects of KAC or CaAC were found to be dependent on catalyst loading, pretreatment procedure, temperature and O2 partial pressure. Experimental observations showed that K is a more effective catalyst for carbon composite oxidation than Ca as expected from prior studies of catalyzed carbon gasification. This was attributed to its ability to form and maintain good interfacial contact with carbon, as well as to its insensitivity to carbon structure because of its excellent wetting ability and mobility. The experimental results suggested that the interfacial catalyst/carbon contact is the critical factor determining the catalytic effectiveness. Thermally deposited phosphorus, upon heat treatment of P-containing compounds such as CH3OP(OH)2 and POCl3 at around 600°C in the presence of inert gas, exhibited a good inhibition effect in the oxidation of C/C composites used in aircraft brake systems. These P compounds were also effective inhibitors for Ca- or K-catalyzed oxidation. The P loading up to a certain amount (ca. 4.0 wt%) was found to suppress Ca-catalyzed oxidation completely. It also improved the resistance of carbon to K-catalyzed oxidation, but the effect was much less significant than in the case of Ca-catalyzed reaction. The characterization of P-doped carbon samples by XPS, XRD, SEM and TPD and the theoretical explorations by ab initio molecular orbital calculations showed that P doping had no effect on the carbon structure and that oxygen-containing P groups preferentially block the active sites on the carbon surface, thus being responsible for the inhibition effect. Boron doping of the composites at 2500°C was found to have a strong inhibition effect in Ca-catalyzed carbon oxidation and a weak effect in K-catalyzed oxidation. Boron as a dopant was confirmed, by XRD, to enhance the graphitization of the composites. The XPS results supported that the chemical state of doped boron is substitutional, that it is oxidized during carbon oxidation, and that it remains on the carbon surface as boron oxide. The substitutional boron and its oxide appear to have a strong effect on the interfacial contact between the carbon substrate and the catalysts. Accordingly, the catalytic effect of Ca can be almost completely suppressed. (Abstract shortened by UMI.)

Wu, Xianxian

430

Hybrid polymer matrix Terfenol-D composite\\/PMN-PT transducer in mechanical series configuration  

Microsoft Academic Search

Combining smart materials with other materials to form composites has received attention due to the possibility of obtaining improved performance and functionality. One such composite combines Terfenol-D particulates with a soft epoxy, with the particles magnetically aligned in one direction forming an anisotropic structure. In this paper we consider the fabrication of the particle composites and the implementation of the

Anthony P. Mortensen; Marcelo J. Dapino

2005-01-01

431

Research of carbon composite material for nonlinear finite element method  

NASA Astrophysics Data System (ADS)

Works on the absorption of collision energy in the structural members are carried out widely with various material and cross-sections. And, with ever increasing safety concerns, they are presently applied in various fields including railroad trains, air crafts and automobiles. In addition to this, problem of lighting structural members became important subject by control of exhaust gas emission, fuel economy and energy efficiency. CFRP(Carbon Fiber Reinforced Plastics) usually is applying the two primary structural members because of different result each design parameter as like stacking thickness, stacking an