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1

Anisotropic thermal property measurement of carbon-fiber/epoxy composite materials  

NASA Astrophysics Data System (ADS)

This work originated from a need for understanding heat transfer in carbon-fiber/epoxy natural-gas tanks undergoing rapid heating during refilling. The dissertation is focused on the determination of the anisotropic thermal properties of carbon-fiber/epoxy composite materials for in-plane and through-thickness directions. An effective anisotropic parameter estimation system consisting of the 3? experimental technique and an anisotropic two-dimensional heat transfer model is developed. In the present work, the 3? method, an experimental technique that has been well established to evaluate the thermal properties of isotropic materials, especially thin film materials, is extended to treat the thermal properties of bulk anisotropic materials. A platinum film deposited on the sample surface is periodically heated by a sinusoidally oscillating current at frequency ?, and thereby causes a time-harmonic electrical resistance variation at frequency 2?. The heat-induced resistance variation at frequency 2? coupled with the current at frequency ? produces a voltage variation component at frequency 3?. The phase and amplitude data of the voltage signal at frequency 3? are collected from the experiment. An impedance analysis model is employed to convert the voltage data to temperature data. The anisotropic thermal properties are deduced from an inverse parameter estimation model, which is a least-square systematic comparison between experimental data and the theoretical model. The anisotropic theoretical model is based on the Green's function approach. A careful sensitivity analysis is used to demonstrate the feasibility of simultaneous estimation of the in-plane and through-thickness thermal conductivities. Poly methyl methacrylate (PMMA) samples were applied as reference samples to verify the measurement system. The parameter estimation result for experimental data from PMMA samples agree very well with handbook values. Experimental results from carbon-fiber/epoxy samples are presented.

Tian, Tian

2

Anisotropic Curie temperature materials  

NASA Astrophysics Data System (ADS)

Existence of anisotropic Curie temperature materials [E. R. Callen, Phys. Rev. 124, 1373 (1961)] is a longstanding prediction - materials that become paramagnetic along certain crystal directions at a lower temperature while remaining magnetically ordered in other directions up to a higher temperature. Validating Callen's theory, we show that all directions within the basal plane of monoclinic Fe7S8 single crystals remain ordered up to 603 K while the hard c-axis becomes paramagnetic at 225 K. Materials with such a large directional dependence of Curie temperature opens the possibility of uniquely new devices and phenomena.

Armstrong, Jason N.; Hua, Susan Z.; Chopra, Harsh Deep

2013-02-01

3

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

4

Propagation of Plane Waves in Anisotropic Micropolar Elastic Media With Applications to Composite Materials.  

National Technical Information Service (NTIS)

In the present work, the propagation of plane harmonic waves in an anisotropic, micropolar elastic media is studied. The special cases of plane harmonic waves in unbounded orthotropic micropolar and tetragonal micropolar elastic media are studied in detai...

D. Ozgur T. R. Tauchert

1971-01-01

5

Negative refraction in anisotropic composites  

NASA Astrophysics Data System (ADS)

Left-handed materials (LHM) are materials in which the direction of wave propagation S is opposite to the wave vector k . S <0 .[1,2,3] LHM exhibit nagative refraction. Experiments have been carried out on a medium consisting of arrays of metallic rings and wrires.[3] An example of a different class of anisotropic left-handed materials are metallic magnetic granular composites. Based on the effective medium approximation, we show that by incorporating metallic magnetic nanoparticles into an appropriate insulating matrix, it may be possible to prepare a composite medium of low eddy current loss which is left-handed for electromagnetic waves propagating in some special direction and polarization in a frequency region near the ferromagnetic resonance frequency.[4,5] This composite may be easier to make on an industrial scale. In addition, its physical properties may be easily tuned by rotating the magnetization locally. The physics involved seems to be different from the original argument.[1,2] In our argument[5], the imaginary part of the dielectric constant of the metal is much larger than the real part, opposite to the original argument. In anisotropic materials so that some of the susceptibilities are negative, the criterion for LHM may not be the same as that for negative refraction.[6] Ansiotropic materials exhibit a richer manifold of anomlous behaviour[6,7,8] and offers more flexibility in apllications.[8] More recently it was found that negative refraction can occur in anisotropic materials where all the susceptibilities are positive.[9] We found that the range of applicability of this effect is much larger than originally thought.[10] S. T. Chui was supported in part by the Office of Naval Research, by the Army Research Laboratory through the Center of Composite Materials at the University of Delaware, by DARPA and by the NSF. [1] J.B.Pendry, A.J.Holden, W.J.Stewart, and I.Youngs, Phys. Rev. Lett 76, 4773 (1996). [2] V.G.Veselago, Sov. Phys. Usp. 10, 509 (1968). [3] D.R.Smith, W.J.Padilla, D.C.Vier, S.C.Nemet-Nasser, S.Schultz, Phys. Rev. Lett. 67, 3578 (2000). [4] S. T. Chui and L. B. Hu, Phys. Rev. B 65, 144407 (2002), [5] S. T. Chui, L. B. Hu and Z. F. Lin, Phys. Lett. A319, 85 (2003). [6] L. B. Hu, S. T. Chui and Z. F. Lin, Phys. Rev. B66, 085108 (2002). [7] V. Lindell and coworkers, Microwave and Opt. Tech Lett. 31, 129 (2001). [8] D. R. Smith and D. Schurig, Phys. Rev. Lett. 90, 077405-1 (2003); D. Schurig and D. R. Smith, Appl. Phys. Lett. 82, 2215 (2003). [9] Y. Zhang, B. Fluegel and A. Mascarenhas, Phys. Rev. Lett. 97, 157404, (2003). [10] Z. F. Lin and S. T. Chui, unpublished.

Chui, S. T.

2004-03-01

6

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

Microsoft Academic Search

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

George Z. Voyiadjis; Babur Deliktas

2000-01-01

7

Physical principles pertaining to ultrasonic and mechanical properties of anisotropic media and their application to nondestructive evaluation of fiber-reinforced composite materials  

SciTech Connect

The central theme of this thesis is to contribute to the physics underlying the mechanical properties of highly anisotropic materials. The hypothesis is that a fundamental understanding of the physics involved in the interaction of interrogating ultrasonic waves with anisotropic media will provide useful information applicable to quantitative ultrasonic measurement techniques employed for the determination of material properties. The desired characteristics of practical fiber-reinforced composites depend on average mechanical properties achieved by placing fibers at specific angles relative to the external surfaces of the finished part. The author examines the physics underlying the use of ultrasound as an interrogation probe for determination of ultrasonic and mechanical properties of anisotropic materials such as fiber-reinforced composites. Fundamental constituent parameters, such as elastic stiffness coefficients, are experimentally determined from ultrasonic time-of-flight measurements. Mechanical moduli descriptive of the anisotropic mechanical properties of unidirectional graphite/epoxy composites are obtained from the ultrasonically determined stiffness coefficients. Three-dimensional visualizations of the anisotropic ultrasonic and mechanical properties of unidirectional graphite/epoxy composites are generated. A goal of the research is to strengthen the connection between practical ultrasonic nondestructive evaluation methods and the physics underlying quantitative ultrasonic measurements for the assessment of manufactured fiber-reinforced composites. Production defects have proven to be of substantial concern in the manufacturing of composites. The author investigates the applicability of ultrasonic interrogation techniques for the detection and characterization of porosity in graphite/epoxy laminates. Complementary ultrasonic parameters based on the frequency dependence of ultrasonic attenuation and integrated polar backscatter are investigated.

Handley, S.M.

1992-01-01

8

Alternative FDTD Updating Schemes for Anisotropic Materials  

Microsoft Academic Search

A novel way of looking at the anisotropic finite difference time domain(FDTD) method is proposed based on the finite element point of view, which allows for a systematic approach of deriving anisotropic FDTD stencils without resorting to interpolation. A new stencil for anisotropic material media that properly accounts for material interfaces and perfect electric conductor boundaries is derived. This new

Christopher Kung; Robert Lee

2009-01-01

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 Magnetism in Field-Structured Composites  

SciTech Connect

Magnetic field-structured-composites (FSCs) are made by structuring magnetic particle suspensions in uniaxial or biaxial (e.g. rotating) magnetic fields, while polymerizing the suspending resin. A uniaxial field produces chain-like particle structures, and a biaxial field produces sheet-like particle structures. In either case, these anisotropic structures affect the measured magnetic hysteresis loops, with the magnetic remanence and susceptibility increased significantly along the axis of the structuring field, and decreased slightly orthogonal to the structuring field, relative to the unstructured particle composite. The coercivity is essentially unaffected by structuring. We present data for FSCs of magnetically soft particles, and demonstrate that the altered magnetism can be accounted for by considering the large local fields that occur in FSCs. FSCS of magnetically hard particles show unexpectedly large anisotropies in the remanence, and this is due to the local field effects in combination with the large crystalline anisotropy of this material.

Anderson, Robert A.; Martin, James E.; Odinek, Judy; Venturini, Eugene

1999-06-24

11

Eddy Current NDT for Anisotropic Composites  

Microsoft Academic Search

3D FEM shell elements are used to determine the sensor impedance variation due to ferromagnetic anisotropic metal fibre composites (FAMFC). The homogenization of the FAMFC is realized by the inverse method. The impedance variation gives the information about the lift-off and\\/or the FAMFC integrity

V. Doirat; J. Fouladgar; G. Berthiau; S. Bensaid

2006-01-01

12

Review of Anisotropic Terahertz Material Response  

NASA Astrophysics Data System (ADS)

Anisotropy is ubiquitous in solids and enhanced in low-dimensional materials. In response to an electromagnetic wave, anisotropic absorptive and refractive properties result in dichroic and birefringent optical phenomena both in the linear and nonlinear optics regimes. Such material properties have led to a diverse array of useful polarization components in the visible and near-infrared, but mature technology is non-existent in the terahertz (THz). Here, we review several novel types of anisotropic material responses observed in the THz frequency range, including both linear and circular anisotropy, which have long-term implications for the development of THz polarization optics. We start with the extreme linear anisotropy of macroscopically aligned carbon nanotubes, arising from their intrinsically anisotropic dynamic conductivity. Magnetically induced anisotropy will then be reviewed, including the giant Faraday effects observed in semiconductors, semimetals, and two-dimensional electron systems.

Arikawa, Takashi; Zhang, Qi; Ren, Lei; Belyanin, Alexey A.; Kono, Junichiro

2013-08-01

13

Review of Anisotropic Terahertz Material Response  

NASA Astrophysics Data System (ADS)

Anisotropy is ubiquitous in solids and enhanced in low-dimensional materials. In response to an electromagnetic wave, anisotropic absorptive and refractive properties result in dichroic and birefringent optical phenomena both in the linear and nonlinear optics regimes. Such material properties have led to a diverse array of useful polarization components in the visible and near-infrared, but mature technology is non-existent in the terahertz (THz). Here, we review several novel types of anisotropic material responses observed in the THz frequency range, including both linear and circular anisotropy, which have long-term implications for the development of THz polarization optics. We start with the extreme linear anisotropy of macroscopically aligned carbon nanotubes, arising from their intrinsically anisotropic dynamic conductivity. Magnetically induced anisotropy will then be reviewed, including the giant Faraday effects observed in semiconductors, semimetals, and two-dimensional electron systems.

Arikawa, Takashi; Zhang, Qi; Ren, Lei; Belyanin, Alexey A.; Kono, Junichiro

2013-11-01

14

Charge and spin processes in anisotropic materials  

Microsoft Academic Search

Several materials have been investigated in order to study charge and spin processes in anisotropic materials, particularly in high magnetic fields. The behavior of charge carriers in graphite based materials, such as bulk graphite, mesoscopic graphite and graphite intercalated compounds are studied. In novel spin systems, a dense Kondo system, CeAgSb2 which has ferro- and antiferro-magnetic ordering depending on the

Eric Jobiliong

2006-01-01

15

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

16

Composite material  

SciTech Connect

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

17

Universal Scaling Relations in Strongly Anisotropic Materials  

NASA Astrophysics Data System (ADS)

We consider the critical temperature in strongly anisotropic antiferromagnetic materials, with weak coupling between stacked planes, in order to determine the interplane coupling constant from experimentally measured susceptibilities. We present theoretical arguments for a universal relation between interplane coupling and susceptibility shown numerically by Yasuda et al. [Phys. Rev. Lett. 94, 217201 (2005)PRLTAO0031-900710.1103/PhysRevLett.94.217201]. We predict a more general scaling function if the system is close to a quantum critical point, a similar relation for other susceptibilities than considered in Yasuda et al., and the validity of these relations for more general phase transitions.

Hastings, M. B.; Mudry, C.

2006-01-01

18

A new direct biaxial testing machine for anisotropic materials  

NASA Astrophysics Data System (ADS)

A screw-driven new biaxial testing machine for the realization of experimental investigations on anisotropic sheet materials, such as composite plates or rolled sheet metals, is presented. The described mechanical concept and servocontrol system allow cruciform specimens to be subjected to large strain biaxial tensile and compressive tests without kinematic incompatibilities. Moreover, for the proper implementation of biaxial tensile tests, the specific problems linked to the anisotropic properties of the investigated materials are taken into account; therefore, for the first time, the biaxial machine is supplied with the original 'off-axes testing device,' consisting of hinged fixtures with knife-edges at each arm of the cruciform specimen. A recently developed optimization method for the optimal design of flat tensile cruciform specimens is shortly reviewed. Numerical simulations illustrate the decisive superiority of the optimized specimen compared with specimen designs proposed in the literature, as well as the necessity to use the 'off-axes' testing technique in biaxial tests on anisotropic materials.

Boehler, J. P.; Demmerle, S.; Koss, S.

1994-03-01

19

Anisotropic Cloth Modeling for Material Fabric  

NASA Astrophysics Data System (ADS)

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

Zhang, Mingmin; Pan, Zhigengx; Mi, Qingfeng

20

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

21

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

22

Oblique edge crack in an anisotropic material under antiplane shear  

Microsoft Academic Search

An oblique edge crack in an anisotropic material under antiplane shear loadings is investigated. The antiplane problems are formulated based on a linear transformation method. An anisotropic solid containing an edge crack subjected to concentrated forces is first considered. The stress intensity factor for the edge crack with concentrated forces is obtained from the solution of the transformed edge crack

H. G. Beom; C. B. Cui

2011-01-01

23

Charge Density Wave and Superconductivity in Anisotropic Materials  

Microsoft Academic Search

The interplay between superconductivity and charge density wave state concomitant with the lattice instability is discussed theoretically based on the partial gapping model appropriate for anisotropic materials. The present calculation aims at supplementing the theory by Bilbro and McMillan on the same partical gapping model. Various thermodynamic quantities such as the specific heat jump at the superconducting transition and anisotropic

Kazushige Machida

1984-01-01

24

Charge Density Wave and Superconductivity in Anisotropic Materials  

NASA Astrophysics Data System (ADS)

The interplay between superconductivity and charge density wave state concomitant with the lattice instability is discussed theoretically based on the partial gapping model appropriate for anisotropic materials. The present calculation aims at supplementing the theory by Bilbro and McMillan on the same partical gapping model. Various thermodynamic quantities such as the specific heat jump at the superconducting transition and anisotropic penetration depth easily accessible by experiments are derived.

Machida, Kazushige

1984-02-01

25

Composite Materials Handbook  

NSDL National Science Digital Library

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

26

Photoelastic effect and mirage deflection in anisotropic materials  

NASA Astrophysics Data System (ADS)

The collinear mirage technique is widely used to measure the thermal diffusivity of semi-transparent materials. However, in a recent paper [A. Salazar, M. Gateshki and A. Sánchez-Lavega: Appl. Phys. Lett. 76, 2665 (2000)], it was shown that for isotropic materials, because of the influence of photoelastic effect, the method was sensitive to the polarization state of the probe beam. The present paper extends the previous work to include anisotropic materials. In particular, we focus on the experimental conditions under which the thermal diffusivity of each crystal system can be measured using the phase method. Our theoretical model indicates that while the thermal diffusivity of isotropic materials can be measured using an unpolarized probe beam, for anisotropic materials, even the use of an unpolarized probe beam does not guarantee the validity of the method in all crystal systems. Experimental measurements performed on cubic, hexagonal and monoclinic crystals confirm the validity of the model.

Salazar, A.; Ang, W. T.; Gateshki, M.; Gutiérrez-Juárez, G.; Sánchez-Lavega, A.

27

Constitutive Modeling of Anisotropic Finite-Deformation Hyperelastic Behaviors of Soft Materials Reinforced by Tortuous Fibers.  

PubMed

Many biological materials are composites composed of a soft matrix reinforced with stiffer fibers. These stiffer fibers may have a tortuous shape and wind through the soft matrix. At small material deformation, these fibers deform in a bending mode and contribute little to the material stiffness; at large material deformation, these fibers deform in a stretching mode and induce a stiffening effect in the material behavior. The transition from bending mode deformation to stretching mode deformation yields a characteristic J-shape stress-strain curve. In addition, the spatial distribution of these fibers may render the composite an anisotropic behavior. In this paper, we present an anisotropic finite-deformation hyperelastic constitutive model for such materials. Here, the matrix is modeled as an isotropic neo-Hookean material. "The behaviors of single tortuous fiber are represented by a crimped fiber model". The anisotropic behavior is introduced by a structure tensor representing the effective orientation distribution of crimped fibers. Parametric studies show the effect of fiber tortuosity and fiber orientation distribution on the overall stress-strain behaviors of the materials. PMID:21822502

Kao, Philip H; Lammers, Steven R; Hunter, Kendall; Stenmark, Kurt R; Shandas, Robin; Qi, H Jerry

2010-04-01

28

Composite Structural Materials.  

National Technical Information Service (NTIS)

The promise of filamentary composite materials, whose development may be considered as entering its second generation, continues to generate intense interest and applications activity. Fiber reinforced composite materials offer substantially improved perf...

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

1982-01-01

29

Locating point of impact in anisotropic fiber reinforced composite plates.  

PubMed

The conventional triangulation technique cannot predict the point of impact in an anisotropic composite plate because the triangulation technique assumes that the wave speed is independent of the direction of propagation which is not the case for anisotropic plates. An alternative method based on the optimization scheme was proposed by Kundu et al. [T. Kundu, S. Das, K.V. Jata, Point of impact prediction in isotropic and anistropic plates from the acoustic emission data, J. Acoust. Soc. Am. 122, 2007, 2057-2066] to locate the point of impact in plates by analyzing the time of arrival of the ultrasonic signals received by the passive sensors attached to the plate. In this paper, that objective function is modified further to overcome the inherent difficulties associated with multiple singularities and to maximize the efficiency of the acoustic emission data for multiple receiving sensors. With this modified objective function the impact point on an anisotropic composite plate is predicted from the acoustic emission data. Experiments are carried out by dropping steel and ping pong balls on a graphite-epoxy composite plate and recording acoustic signals by passive transducers adhesively bonded to the plate at three different locations. The impact point is predicted by the proposed method and compared with the actual location of impact. PMID:18255117

Kundu, Tribikram; Das, Samik; Martin, Steven A; Jata, Kumar V

2007-12-23

30

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

Microsoft Academic Search

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

Z. W. Guan; E. C. Zhu

2009-01-01

31

Mechanics of composite materials  

SciTech Connect

This book contains the following papers: crack growth resistance of TiB{sub 2} particulate/SiC matrix composite; constitutive relations of flexible composites under elastic deformation; determination of two kinds of composite plasticity: inclusions plastic vs. matrix plastic; 3-D analysis of transient interlaminar thermal stress of laminated composites; effect of seawater on the fracture toughness of pultruded rods; evaluation of new failure criterion for fibrous composite materials; and bridged cracks in fiber-reinforced composites.

Dvorak, G.J. (Inst. Center for Composite Materials and Structures, Rensselaer Polytechnic Inst. (US)); Laws, N. (Dept. of Mechanical Engineering, Univ. of Pittsburgh, PA (US))

1988-01-01

32

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

33

Time-resolved line focus acoustic microscopy of layered anisotropic media: application to composites.  

PubMed

This paper presents theoretical and experimental studies of the time-domain response of line focus acoustic microscopy from a layered anisotropic medium. A method for elastic constant reconstruction from acoustic microscopy signatures also is presented. The microscopy response is complicated by multiple reflections in the layers and by the anisotropic nature of the material. The model is based on a new, stable recursive stiffness matrix algorithm developed for a multilayered anisotropic medium, which is applied to the interpretation of the time-resolved acoustic microscopy signature. Specific examples are given for unidirectional and multidirectional graphite epoxy composites. It is shown that the fluid load has a significant effect on the leaky surface waves in these composites, increasing surface wave speed above that for the slow transverse wave. This results in its absence from the microscopy signature of the surface wave. The theoretical results are compared with experiments carried out using a line focus PVDF transducer developed at National Institute of Standards and Technology (NIST). Time-resolved acoustic microscopy has been applied to the determination of elastic constants of a unidirectional composite or of one lamina in a cross-ply composite. The lateral waves and multiple reflections of bulk waves appearing in the microscopy signatures are used for the elastic properties reconstruction. The reconstruction results are compared to data obtained by the self-reference double-through-transmission ultrasonic bulk wave method. PMID:12243574

Wang, Lugen; Rokhlin, Stanislav I

2002-09-01

34

Propagation of surface waves at the interface between nonlinear MTMs and anisotropic materials  

NASA Astrophysics Data System (ADS)

Metamaterials (MTMs), which have both negative permeability and negative permittivity, have potential applications in optoelectronics and communications. These materials are fabricated in laboratories which is an added advantage. The focus of this work is on the propagation of surface waves at the interface between nonlinear MTMs and anisotropic materials in the optical range. The dispersion equation is derived from Maxwell's equations. The dispersion equation is solved numerically to study the characteristics of the propagated wave. Only TE modes are considered. The results display the dependence of the propagating waves on the characteristics of the structure composite materials.

El-Khozondar, Hala J.; El-Khozondar, Rifa J.; Zouhdi, Said

2013-10-01

35

Analysis of a Curved Interfacial Crack Between Viscoelastic Foam and Anisotropic Composites Under Antiplane Shear  

NASA Astrophysics Data System (ADS)

The analysis of curved interfacial crack between viscoelastic foam and anisotropic composites was conducted under antiplane shear loading applied at infinity. In the analysis, in order to represent viscoelastic behavior of foam, the Kelvin-Maxwell model was incorporated and Laplace transform was applied to treat the viscoelastic characteristics of foam. The curved interfacial crack problem was reduced to a Hilbert problem and a closed-form asymptotic solution was derived. The stress intensity factors in the vicinity of the interfacial crack tip were predicted by considering both anisotropic characteristics of composites and viscoelastic properties of foam. It was found from the analysis that the stress intensity factor was governed by material properties such as shear modulus and relaxation time, and increased with the increase in the curvature as well as the ratio of stiffness coefficients of composite materials. It was also observed that the effect of fiber orientation in the composite materials on the stress intensity factor decreased with the increase in the difference in stiffness coefficients between foam and composite.

Chun, Heoung Jae; Park, Sang Hyun

36

Stress Concentration around Circular Hole in a Composite Material Specimen Representative of the X-29A Forward-Swept Wing Aircraft.  

National Technical Information Service (NTIS)

The theory of anisotropic elasticity was used to evaluate the anisotropic stress concentration factors of a composite laminated plate containing a small circular hole. This advanced composite material was used to manufacture the X-29A forward swept wing. ...

H. Yeh

1988-01-01

37

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

PubMed

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

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

2013-05-28

38

Electrically conductive composite material  

DOEpatents

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

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

1989-01-01

39

Composite Material Switches  

NASA Astrophysics Data System (ADS)

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

Javadi, Hamid

2002-09-01

40

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

NASA Astrophysics Data System (ADS)

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

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

2008-05-01

41

A new macroscopically anisotropic pressure dependent yield function for metal matrix composite based on strain gradient plasticity for the microstructure  

NASA Astrophysics Data System (ADS)

Metal matrix composites with long aligned elastic fibers are studied using an energetic rate independent strain gradient plasticity theory with an isotropic pressure independent yield function at the microscale. The material response is homogenized to obtain a conventional macroscopic model that exhibits anisotropic yield properties with a pressure dependence. At the microscale free energy includes both elastic strains and plastic strain gradients, and the theory demands higher order boundary conditions in terms of plastic strain or work conjugate higher order tractions. The mechanical response is investigated numerically using a unit cell model with periodic boundary conditions containing a single fiber deformed under generalized plane strain conditions. The homogenized response can be modeled by conventional plasticity with an anisotropic yield surface and a free energy depending on plastic strain in addition to the elastic strain. Hill's classical anisotropic yield criterion is extended to cover the composite such that hydrostatic pressure dependency, Bauschinger stress and size-effects are considered. It is found that depending on the fiber volume fraction, the anisotropic yield surface of the composite is inclined compared to a standard pressure independent yield surfaces. The evolution of the macroscopic yield surface is investigated by quantifying both anisotropic hardening (expansion) and kinematic hardening (translation), where the coefficients of anisotropy and the Bauschinger stress are extracted.

Azizi, Reza; Nyvang Legarth, Brian; Niordson, Christian F.

2013-04-01

42

Resin composite restorative materials.  

PubMed

This paper surveys the most important developments in resin-based dental composites and focuses on the deficits (e.g. polymerization shrinkage) and strengths of the materials and their clinical implications. Moreover, differences between composite categories, such as hybrid, nanohybrid, microfilled, packable, ormocer-based, silorane-based, polyacid-modified composites (compomers) and flowable composites are highlighted, especially in view of their mechanical behaviour. In addition to the classical dimethacrylate-based composites, special attention is given to alternative monomers, such as siloranes, ormocers or high-molecular-weight dimethacrylate monomers (e.g. dimer acid-based dimethacrylates and tricyclodecane (TCD)-urethane), analysing their advantages, behaviour and abilities. Finally, the paper attempts to establish the needs and wishes of clinicians for further development of resin-based composites. PMID:21564116

Ilie, N; Hickel, R

2011-06-01

43

Research and Development of Bulk Anisotropic Nanograin Composite Rare Earth Permanent Magnets  

Microsoft Academic Search

Innovative and cost-effective technology for synthesizing bulk anisotropic nanograin composite rare earth magnets has been developed. Using a powder blending technique, (BH)max of nanograin composite magnets can reach 40 to 50 MGOe, while applying powder coating techniques, (BH)max = 45–55 MGOe were achieved. Thus, principal technical difficulties in synthesizing bulk anisotropic nanograin composite magnets are successfully overcome. In addition, it

Sam LIU; Don LEE; Mei-qing HUANG; Ashil Higgins; Yu-hui SHEN; Youngson HE; Christina CHEN

2006-01-01

44

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

45

Fretting contact of dissimilar isotropic/anisotropic materials  

NASA Astrophysics Data System (ADS)

A better understanding of the damage caused by the surface tribological phenomenon of fretting contact is achieved by a study of the local contact stresses. Many real life instances of fretting contact can be approximated as two elastic half spaces in contact with an appropriate gap function. This work presents a numerical method, based on the solution to coupled Cauchy Singular Integral Equations (SIEs), to obtain the contact tractions when two half-spaces made from dissimilar isotropic/anisotropic materials are in partial slip contact. If one of the half-spaces is anisotropic, Coulomb's law of friction is modified by assuming that the out-of-plane shear traction is identically zero. The numerical method is extensively verified by comparing its results to those found in the literature and to results obtained using FEM. A numerical method, based on the FFT technique, to obtain the sub-surface stresses in an anisotropic half-space is also presented. Well characterized fretting fatigue experiments were conducted with dissimilar isotropic materials (Ti-6Al-4V & Inco718 alloys) to study the effect of the contact loads on component life. Experiments were also conducted to measure the average coefficient of friction as a function of the number of fretting cycles. It was found that, similar to other fretting fatigue experiments, the average coefficient of friction stabilizes after a certain number of fretting cycles. A numerical method is developed to obtain the slip zone coefficient of friction from the measured average value. The calculations showed that the slip zone coefficient of friction is considerably higher than the average value. The SIE method is used to obtain the contact stresses in the experimental specimens by taking into account the slip zone coefficient of friction and the small deviations, caused by machining, in the fretting pad profiles. The contact stresses are then used in conjunction with a crack nucleation approach to predict life to fretting crack nucleation in the experimental specimens. The effect of residual stresses in the specimens was also included in this analysis. The trend of the predicted fretting crack nucleation lives was quite encouraging. Finally, the ability of the SIE method to calculate the contact stress evolution due to "fretting missions", with changing normal load, shear load, and moment, is demonstrated.

Pakalapati, Rajeev Tirumala

46

Enhancing photon tunnelling by a slab of uniaxially anisotropic left-handed material  

Microsoft Academic Search

We study the unusual enhancement of photon tunnelling by a slab of uniaxially anisotropic negative refractive index material, also known as left-handed material (LHM). It is found that the uniaxially anisotropic LHMs can greatly enhance the photon tunnelling for transverse electric (TE), transverse magnetic (TM), as well as both TM and TE waves when different conditions are satisfied. The phenomenon

Zheng Liu; Liangbin Hu; Zhifang Lin

2003-01-01

47

Orthopedic Composite Materials.  

National Technical Information Service (NTIS)

The program was designed as a pilot project to establish new techniques for making orthopedic prosthetic materials. The basic idea was to make metal supported ceramic composites, so that the metal provided strength (and an element of ductility) and the re...

B. J. Shaw

1972-01-01

48

On the theory of conductivity of anisotropic composites: A weakly inhomogeneous medium  

SciTech Connect

The conductivity of a weakly inhomogeneous anisotropic medium is considered. The effective conductivity tensor is determined in the approximation quadratic in deviation of local conductivity {sigma}(r) from mean value {sigma} for an arbitrary anisotropy of the composite.

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

2011-02-15

49

Point of Impact Prediction in Anisotropic Fiber Reinforced Composite Plates from the Acoustic Emission Data  

NASA Astrophysics Data System (ADS)

A newly developed optimization based method is followed to locate the point of impact in anisotropic composite plates for which conventional triangulation technique fails. The new technique works for both anisotropic and isotropic plates. Experiments are carried out by dropping a steel ball on a graphite-epoxy composite plate and picking up acoustic signals by passive transducers adhesively bonded to the plate at different locations. Predicted points of impact are compared with the true impact point.

Kundu, T.; Das, S.; Jata, K. V.

2008-02-01

50

Spin wave instability processes in anisotropic ferrite materials  

NASA Astrophysics Data System (ADS)

A theoretical and experimental study of spin wave instability processes in anisotropic ferrite materials has been performed. The theory of spin wave instability for ferromagnetic insulators is extended to include generalized anisotropy based on a tensor formulation of the static and dynamic effective fields. The formalism is set up for saturated magnetic ellipsoids and a general microwave field configuration. The analysis yields working formulae for the threshold microwave field amplitude evaluations and critical mode determinations. Numerical simulations are used to calculate threshold field and critical modes for first order oblique pumping processes in a thin disk with easy plane anisotropy. The theory was successfully applied to the analysis of comprehensive experimental data on anisotropic ferrite materials for various static and microwave field configurations. The dependence of the threshold field amplitude on the external field was investigated experimentally at 9 and 16.7 GHz. The high power thresholds were measured for different geometrical configurations and spin wave relaxation rates were determined. The data showed qualitative agreement with the theoretical calculations. The spin wave linewidth was found to be independent of the spin wave propagation direction. The specific results are presented for three different ferrite materials, liquid phase epitaxy (LPE) yttrium iron garnet (YIG) single crystal thin films, polycrystalline hipped YIG, and Y-type zinc (Zn-Y) single crystal easy plane hexagonal ferrite. In LPE YIG films, the spin wave linewidth was 0.2 Oe at 9 GHz and the influence of thin film geometry and small magnetocrystalline anisotropy on the high power thresholds was found. In hipped YIG, the spin wave linewidth was determined by the grain size and was 1.2 Oe at 9 GHz and 0.6 Oe at 16.7 GHz. In Zn-Y, 9 GHz data demonstrated related sample size effects, so that high power thresholds were inversely proportional to the sample lateral size. At 16.7 GHz, there were no sample size effects and oblique pumping measurements were performed. It was found that the spin wave linewidth increases from 12 Oe to about 18 Oe if the magnetization is pulled out of the easy crystallographic plane.

Nazarov, Alexey V.

2002-01-01

51

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

PubMed

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

Levitas, Valery I; Attariani, Hamed

2013-01-01

52

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.

Levitas, Valery I.; Attariani, Hamed

2013-01-01

53

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

54

Thermal Expansion Coefficients of Composite Materials Based on Energy Principles  

Microsoft Academic Search

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

R. A. Schapery

1968-01-01

55

Free vibration of advanced anisotropic multilayered composites with arbitrary boundary conditions  

NASA Astrophysics Data System (ADS)

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

Woodcock, Roland L.

2008-05-01

56

Liquid Helium Composite Regenerator Material.  

National Technical Information Service (NTIS)

A cryogenic composite material designed for application to gap regenerators in cyclic cryocoolers operating below 10 K is investigated. The material is a composite of helium self-loaded into a metallic extended surface structure whose dispersion form is s...

T. R. Knowles

1987-01-01

57

Multifunctional Autonomically Healing Composite Material.  

National Technical Information Service (NTIS)

A composite material, contains a polymer, a polymerizer, a corresponding catalyst for the polymerizer, and a plurality of capsules. The polymerizer is in the capsules. The composite material is self-healing.

J. S. Moore N. R. Sottos P. H. Geubelle S. R. Sriram S. R. White

2005-01-01

58

Effects of anisotropic surface texture on the performance of ionic polymer-metal composite (IPMC)  

NASA Astrophysics Data System (ADS)

Ionic polymer metal composite (IPMC), an electrically activated polymer (EAP), has attracted great attention for the excellent properties such as large deformation, light weight, low noise, flexibility and low driving voltages, which makes the material a possible application as artificial muscle if the output force can be increased. To improve the property, we manufactured the Nafion membrane by casting from liquid solution, modified the surface by sandblasting or polishing, and obtained the isotropic and anisotropic surface texture respectively. The microstructure of the Nafion surface and metal electrode, effects of surface texture on the output force and displacement of IPMC were studied. Results show that the output force of IPMC with the anisotropic surface texture is 2~4 times higher than that with the isotropic surface texture without enormous sacrifice of the displacement. The output force may reach to 6.63gf (Sinusoidal 3.5V and 0.1Hz, length 20mm, width 5mm and thickness 0.66mm), which suggest an effective way to improve the mechanical properties of IPMC.

He, Qingsong; Yu, Min; Ding, Haitao; Guo, Dongjie; Dai, Zhendong

2010-03-01

59

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

NASA Astrophysics Data System (ADS)

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

Lu, Gehao; da, Jian; Mo, Qi; Chen, Pengwu

2011-11-01

60

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

Microsoft Academic Search

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\\u000a materials are estimated to be anisotropic with an effective thermal conductivity. However, there is little quantitative data\\u000a on the anisotropic effective thermal

Naoto Haruki; Akihiko Horibe; Keigo Nakashima

2011-01-01

61

Laser ceramics with rare-earth-doped anisotropic materials.  

PubMed

The fabrication of laser-grade anisotropic ceramics by a conventional sintering process is not possible owing to optical scattering at randomly oriented grain boundaries. In this Letter, we report the first (to our knowledge) realization of transparent anisotropic ceramics by using a new crystal orientation process based on large magnetic anisotropy induced by 4f electrons. By slip casting in a 1.4 T magnetic field and subsequent heat treatments, we could successfully fabricate laser-grade calcium fluorapatite ceramics with a loss coefficient of 1.5 cm(-1). PMID:21042362

Akiyama, Jun; Sato, Yoichi; Taira, Takunori

2010-11-01

62

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

63

Evaluation of imaging in planar anisotropic and isotropic dendritic left-handed materials  

Microsoft Academic Search

We experimentally and theoretically demonstrate subwavelength imaging effects in two series of anisotropic and isotropic dendritic\\u000a left-handed materials (LHMs) lenses. A scanning transmission measurement was used to measure the spatial power distribution\\u000a of the focused electromagnetic waves that radiate from a point source. When using anisotropic LHMs lenses, the half maximum\\u000a of the focused beam with a width as small

X. Zhou; X. P. Zhao

2007-01-01

64

The phenomenon of super energy flows in the anisotropic left-handed material  

NASA Astrophysics Data System (ADS)

The super energy flows generated and transmitted have been investigated in a parallel-plate waveguide, which is filled with air and the anisotropic left-handed materials. Theoretical analysis and numerical simulations show that the propagation modes of the anisotropic super waveguide are consistent with those of the isotropic waveguides [1-3]. They also show that the loss of electromagnetic parameters size of waveguide will influence the amplitude of time-average power flows.

Xu, Bai Bing; Yu, Guan Xia; Xia, Li Juan; Wang, Zhi Yuan

2013-01-01

65

The phenomenon of super energy flows in the anisotropic left-handed material  

NASA Astrophysics Data System (ADS)

The super energy flows generated and transmitted have been investigated in a parallel-plate waveguide, which is filled with air and the anisotropic left-handed materials. Theoretical analysis and numerical simulations show that the propagation modes of the anisotropic super waveguide are consistent with those of the isotropic waveguides [1-3]. They also show that the loss of electromagnetic parameters size of waveguide will influence the amplitude of time-average power flows.

Xu, Bai Bing; Yu, Guan Xia; Xia, Li Juan; Wang, Zhi Yuan

2012-10-01

66

Energy Absorption of Composite Materials.  

National Technical Information Service (NTIS)

This paper results of a study on the energy absorption characteristics of selected composite material systems and compares the results with aluminum. Composite compression tube specimens were fabricated with both tape and woven fabric prepreg using graphi...

G. L. Farley

1983-01-01

67

The propagation of coupled Lamb waves in multilayered arbitrary anisotropic composite laminates  

NASA Astrophysics Data System (ADS)

Based on linear three-dimensional elasticity theory, the wave equations of coupled Lamb waves in multilayered arbitrary anisotropic composite laminates are derived using a Legendre orthogonal polynomial approach. The elastodynamic solution for the propagation of coupled Lamb waves in composite plates is also presented to determine the characteristics of coupled Lamb waves. To verify the applicability and validity of the method, two cases of bi-layered plates formed with isotropic components and anisotropic components, respectively, are primarily manipulated for comparison with earlier known results. Next, the dispersion curves, displacements and stress distributions of Lamb waves in multilayered anisotropic laminates are calculated. The effects of coupling and fiber orientation on the characteristics of the Lamb waves are illustrated. The potential usefulness of the fundamental modes of the coupled Lamb waves is discussed in detail.

Cunfu, He; Hongye, Liu; Zenghua, Liu; Bin, Wu

2013-12-01

68

Magnetic alignment of hexagonal boron nitride platelets in polymer matrix: toward high performance anisotropic polymer composites for electronic encapsulation.  

PubMed

We report magnetic alignment of hexagonal boron nitride (hBN) platelets and the outstanding material properties of its polymer composite. The magnetically responsive hBN is produced by surface modification of iron oxide, and their orientations can be controlled by applying an external magnetic field during polymer curing. Owing to the anisotropic properties of hBN, the epoxy composite with aligned hBN platelets shows interesting properties along the alignment direction, including significantly reduced coefficient of thermal expansion, reaching ?28.7 ppm/°C, and enhanced thermal conductivity, 104% higher than that of unaligned counterpart, both of which are observed at a low filler loading of 20 wt %. Our modeling suggests the filler alignment is the major reason for these intriguing material properties. Finite element analysis reveals promising applications for the magnetically aligned hBN-based composites in modern microelectronic packaging. PMID:23815609

Lin, Ziyin; Liu, Yan; Raghavan, Sathyanarayanan; Moon, Kyoung-Sik; Sitaraman, Suresh K; Wong, Ching-Ping

2013-07-15

69

Anisotropic oxidation and weight loss in PMR15 composites  

Microsoft Academic Search

Durability and degradation mechanisms in composites are fundamentally influenced by the fiber, matrix, and interphase regions that constitute the composite domain. The thermo-oxidative behavior of the composite is significantly different from that of the fiber and matrix constituents as the composite microstructure, including the fiber–matrix interphases\\/interfaces, introduces anisotropy in the diffusion behavior. In this work, unidirectional G30-500\\/PMR-15 composite specimens were

G. A. Schoeppner; G. P. Tandon; E. R. Ripberger

2007-01-01

70

Stress concentration factor of a structurally anisotropic composite plate weakened by an oval opening  

Microsoft Academic Search

Determining the stress concentration factor for a fiber-reinforced viscoelastic plate is given using the method of effective moduli. The plate is weakened by an oval or crack opening and deformed by forces applied to its middle plane. Problems of tension and pure bending of a structurally anisotropic composite plate with an oval opening or crack are presented. The effects due

M. N. M. Allam; A. M. Zenkour

2003-01-01

71

Characterization of cryogenic microcracking in carbon fiber\\/epoxy composite materials  

Microsoft Academic Search

Polymeric composite materials have been widely utilized to take advantage of their large specific strength and stiffness. These characteristics have made them attractive for use in aerospace applications as containment structures for cryogenic fluids. However, the anisotropic, heterogeneous, and viscoelastic nature of polymeric composite materials creates a unique set of challenges for the storage of cryogenic fluids. Mismatches in thermal

John Francis Timmerman

2003-01-01

72

On the equations governing the motion of an anisotropic poroelastic material  

Microsoft Academic Search

We address Biot's equations governing the motion of an anisotropic fluid-saturated poroelastic material with certain properties. First, we investigate the uniqueness in solutions of the three-dimensional governing equations for the regular region of the poroelastic material and enumerate the conditions sufficient for the uniqueness. Next, by applying Hamilton's principle to the motion of the region, we obtain a variational principle

Gülay Altay; M. Cengiz Dökmeci

2006-01-01

73

Experimental investigation of laws governing the hardening of initially anisotropic materials  

Microsoft Academic Search

A large number of studies are devoted to establishment of the relation between stresses and strains in initially anisotropic materials beyond the elastic limit. Alternate schemes of the strain theory of plasticity, which take into account the initial anisotropy of the plastic properties of a material, are proposed in [1-4, and others]. In the strain theories, the relation between the

V. V. Kosarchuk; B. I. Koval'chuk; A. A. Lebedev

1982-01-01

74

A constitutive formulation for anisotropic materials suitable for wave propagation computer programs—II  

Microsoft Academic Search

The constitutive relationships for an anisotropic material are established for shock wave propagation and nonlinear, large deformation computer programs, commonly referred to as hydrocodes. Stresses are formulated in terms of strains; the procedure for separating material compressibility effects (equation of state) from strength effects is formulated which permits the consistent calculation of stresses in the elastic regime, and allows the

Ch. E. Anderson; P. A. Cox; G. R. Johnson; P. J. Maudlin

1994-01-01

75

A constitutive formulation for anisotropic materials suitable for wave propagation computer programs---II  

Microsoft Academic Search

The constitutive relationships for an anisotropic material are established for shock wave propagation and nonlinear, large deformation computer programs, commonly referred to as hydrocodes. Stresses are formulated in terms of strains; the procedure for separating material compressibility effects (equation of state) from strength effects is formulated which permits the consistent calculation of stresses in the elastic regime, and allows the

Ch. E. Anderson; P. A. Cox; G. R. Johnson; P. J. Maudlin

1994-01-01

76

Composite material heat pipe radiator  

Microsoft Academic Search

Organic matrix composite material is recognized for its significant strength to weight ratio when compared to metal and consequently was investigated for reducing the mass of heat pipes for future space missions. The particular heat pipe that was constructed and tested was made from an organic matrix composite material applied to a linear of titanium tubing spun to foil thickness

Nelson J. Gernert; David B. Sarraf; Richard J. Guenther

1996-01-01

77

Investigation of Microstructural Change by X-ray Tomography and Anisotropic Effect on Thermal Property of Thermally Oxidized 2DC\\/C Composite for Very High Temperature Reactor  

Microsoft Academic Search

Two-dimensional carbon fiber reinforced carbon composite (2D-C\\/C composite) is one of the candidate materials for reactor internals, e.g., control rod element, of Very High Temperature Reactor (VHTR) because of its high strength at high temperature and thermal stability. From the viewpoint of its application to the reactor internals of the VHTR, it is important to investigate the anisotropic effect on

Junya SUMITA; Taiju SHIVARA; Eiji KUNIMOTO; Masatoshi YAMAJI; Takashi KONISHI; Kazuhiro SAWA

2010-01-01

78

Joining of composite materials  

SciTech Connect

This Conference Proceedings contains 9 papers, of which one is abstracted separately, describing the latest achievement in effective methods of joining of composite structures. Most composite systems do not deform plastically and thus cannot alleviate stress concentration. The papers cover the design, analysis, testing and inspection of joined interfaces. Data are given for both mechanically fastened and adhesively bonded joints.

Kedward, K.T.

1981-01-01

79

Determining true stress–strain curve for isotropic and anisotropic materials with rectangular tensile bars: method and verifications  

Microsoft Academic Search

Based on an extensive numerical study, the authors have recently developed a method for determining the true stress–strain curve for isotropic materials by using rectangular tensile specimens. In this method only load versus thickness reduction (at the diffuse necking zone) curve is needed. This method has been further developed for anisotropic materials. For anisotropic materials, both thickness and width reduction

Z. L. Zhang; J. Ødegård; O. P. Søvik

2001-01-01

80

Numerical solution of three-dimensional problem of free vibrations of composite laminated anisotropic shells of revolution  

SciTech Connect

For many years, the main targets of improved approaches to the calculation of natural frequencies and modes of elastic vibrations have been laminated (mainly three-layer) plates and shells with layers differing substantially in rigidity. In such structural elements, specific modes of vibration are realized, owing to the low rigidity of the filler. Composite material structures usually have layers that are similar or equal in rigidity in the original state; the nonuniformity stems from differences in orientation of the layers in the packet. Composites that are used in machinery construction are characterized by low normal and shear transverse rigidities. These features also give rise to nonclassical phenomena in free vibrations. Vibrations of thick-wall orthotropic plates and hollow circular cylinders have been analyzed. In those cases, three-dimensional effects were governed largely by the thickness. Where the stress-strain state of laminated composite shells of revolution was analyzed, it follows that a complex three-dimensional character of the strained state is also characteristic for extremely thin shells if the layers are anisotropic (nonorthotropic). In the work reported here, the authors developed a procedure for the numerical solution of the problem of elastic free vibrations of composite shells of revolution, in which all of the features they have enumerated are taken into account to the greatest extent possible. A universal algorithm has been based on finite-element idealization of the three-dimensional relationships in the theory of anisotropic elasticity.

Nosatenko, P.Ya.; Omel`chenko, M.N.

1992-03-01

81

Magnetostatically-Coupled Anisotropic Composite Magnets with Enhanced Remanence.  

National Technical Information Service (NTIS)

The computer simulation confirmed a magnetostatic coupling between R- Fe-B matrix and thick Fe layers in hot-deformed composite magnets. However, enhancement in the remanence and maximum energy product of the hard-soft composites requires at least a parti...

G. C. Hadjipanayis

2007-01-01

82

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

2013-08-15

83

Mechanics of composite materials  

Microsoft Academic Search

The book presents a comprehensive account of the basic theory of the mechanical behavior of heterogeneous materials. Basic results of continuum mechanics concerning elasticity theory, viscoelasticity theory, plasticity theory and Eshelby's formula are summarized, and the stiffness or effective moduli of materials containing spherical inclusions and cylindrical and lamellar systems are examined in detail. Laminates are discussed, and the analysis,

R. M. Christensen

1979-01-01

84

Specific heat and thermal conductivity measurements for anisotropic and random macroscopic composites of cobalt nanowires.  

PubMed

We report simultaneous specific heat (c(p)) and thermal conductivity (?) measurements for anisotropic and random macroscopic composites of cobalt nanowires (Co NWs), from 300 to 400 K. Anisotropic composites of Co NW consist of nanowires grown within the highly ordered, densely packed array of parallel nanochannels in anodized aluminum oxide. Random composites are formed by drop-casting a thin film of randomly oriented Co NWs, removed from the anodized aluminum oxide host, within a calorimetric cell. The specific heat measured with the heat flow parallel to the Co NW alignment ([Formula: see text]) and that for the random sample (c(p)(R)) deviate strongly in temperature dependence from that measured for bulk, amorphous, powder cobalt under identical experimental conditions. The thermal conductivity for random composites (?(R)) follows a bulk-like behavior though it is greatly reduced in magnitude, exhibiting a broad maximum near 365 K indicating the onset of boundary-phonon scattering. The thermal conductivity in the anisotropic sample ([Formula: see text]) is equally reduced in magnitude but increases smoothly with increasing temperature and appears to be dominated by phonon-phonon scattering. PMID:21836319

Pradhan, N R; Duan, H; Liang, J; Iannacchione, G S

2008-11-12

85

Biotechnology and Composite Materials.  

National Technical Information Service (NTIS)

Biotechnology, in general terms, is the science and engineering of using living organisms for making useful products such as pharmaceuticals, foods, fuels, chemicals, materials or in waste treatment processes and clinical and chemical analyses. It encompa...

B. C. Woolsey R. Narayan R.C. Schiavone

1993-01-01

86

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

Microsoft Academic Search

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.

J. M. Winey; Y. M. Gupta

2010-01-01

87

Fracture mechanics of composite materials  

Microsoft Academic Search

The above circumstances lead to models based on a discussion of the structure of a composite being used most frequently in the fracture mechanics of composite materials. In view of the stochastic properties of the elements in the structure, especially the dispersion in the strength of the fibers, stochastic fracture models are widely used [4-7]. Nevertheless, there has been no

V. V. Bolotin

1981-01-01

88

Omnidirectional reflection from the one-dimensional photonic crystal containing anisotropic left-handed material  

Microsoft Academic Search

We study the transmission properties in the one-dimensional\\u000aphotonic crystal containing alternate anisotropic left-handed\\u000amaterial (LHM) layers and regular isotropic right-handed material\\u000a(RHM) layers. For such an anisotropic case, the dispersion\\u000arelation from the Bloch theorem is derived and the Bragg gaps of\\u000athe periodic structure are observed. It is found that in the m=0\\u000aBragg gap, there is an

S. Wang; L. Gao

2005-01-01

89

Anisotropic Hardness Estimations of Some Inorganic Functional Materials  

NASA Astrophysics Data System (ADS)

For the first time, this work indicates that mechanical concerns of inorganic materials are highly demanded when well optimizing their functional applications. We quantitatively give the proper data of hardness on different planes of some representative inorganic functional materials including borides, carbides, nitrides and oxides. This work clearly indicates mechanical importance in studying functionality of inorganic materials, and provides people guidance in the practical applications of these materials.

Yang, Peng; Li, Keyan; Xue, Dongfeng

2012-03-01

90

Anisotropic material properties of fused deposition modeling ABS  

Microsoft Academic Search

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

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

2002-01-01

91

Left Handed Materials Using Magnetic Composites.  

National Technical Information Service (NTIS)

A left-handed composite material which includes a mixture of a ferromagnetic material and a dielectric material. The direction of magnetization of the ferromagnetic material, and its volume fraction are controlled such that the composite material exhibits...

J. Q. Xiao S. T. Chui

2003-01-01

92

Anisotropic thermal conductivity of three-layer laminated carbon-graphite composites from carbonized wood  

Microsoft Academic Search

Composites with characteristics of anisotropic thermal conductivity for thermal management in Solar Power Satellite (SPS),\\u000a to discharge the heat that was generated when solar energy was not converted to electricity, were developed by alternating\\u000a layers of laminated graphite and carbonized wood. The effects of the weight fraction of carbonized wood, particle size, interlayer\\u000a interfaces, and environment temperature on the thermal

Joko Sulistyo; Toshimitsu Hata; Masashi Fujisawa; Kozo Hashimoto; Yuji Imamura; Tamami Kawasaki

2009-01-01

93

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

SciTech Connect

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

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

2011-11-15

94

Determination of the Anisotropic Thermal Conductivity of a Carbon Aerogel–Fiber Composite by a Non-contact Thermographic Technique  

Microsoft Academic Search

The carbon-composite under investigation consists of a felt of carbon fibers infiltrated by a nanoporous sol-gel derived carbon\\u000a aerogel; in addition, cracks caused by the shrinkage of the gel upon drying are present within the composite. Due to the anisotropic\\u000a structure of the felt, consisting of a pinned stack of fiber mats, the thermal conductivity of the compound is anisotropic.

V. Drach; M. Wiener; G. Reichenauer; H.-P. Ebert; J. Fricke

2007-01-01

95

Ski Technology And Composite Materials  

NSDL National Science Digital Library

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

2010-01-01

96

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

Microsoft Academic Search

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

Wei Ding; Liang Chen; H. Liang

2007-01-01

97

Surface polaritons and transmission in multi-layer structures containing anisotropic left-handed materials  

Microsoft Academic Search

We study the surface polaritons and optical transmission in multi-layer structures containing alternate anisotropic left-handed\\u000a materials and isotropic right-handed materials. By means of the transfer matrix method, the dispersive relations of the surface\\u000a polaritons are derived. In contrast to the single left-handed slab, the multi-layer structure is capable of supporting more\\u000a surface polaritons due to the existence of more interfaces

L. Gao; Y. Huang; C. Tang

2007-01-01

98

Anisotropic constitutive relationships in energetic materials: PETN and HMX  

NASA Astrophysics Data System (ADS)

One of the important goals in energetic materials (EM) research is predicting EM properties from first principles based upon underlying atomic structure. Special attention is being focused on obtaining accurate equations of state for several important classes of EMs. In this presentation, we will discuss the results of first-principles density functional theory calculations of the energetic materials PETN and HMX. For each material, we have simulated both hydrostatic compression and uniaxial compression in the crystallographic directions [100], [010], [001], [110], [101], [011], and [111] up to V/V0 = 0.50 (˜40-50 GPa). We will examine the equations of state for each material and other structural properties of the unit cell as a function of volume and compare with available experimental results. Also, we will discuss the correlation between calculated shear stresses upon uniaxial compression with experimentally observed anisotropies in sensitivity to shock-induced detonation.

Conroy, Michael; Oleynik, Ivan; Zybin, Sergey; White, Carter

2007-06-01

99

The effect of beam directivity on the inspection of anisotropic materials using ultrasonic arrays  

NASA Astrophysics Data System (ADS)

The beam directivity from an ultrasonic transducer in isotropic materials is well documented. However, beam directivities in elastically anisotropic materials and their effect on ultrasonic NDE inspection has been investigated far less extensively. In this paper, analytical and numerical finite element models are developed to predict the beam directivity in a single crystal nickel-based superalloy. This material is highly anisotropic and is used widely in the gas-turbine industry. The developed models are used to investigate the effect of the crystallographic orientation on the beam directivity. In turn, the effect of beam directivity on defect detection sensitivity and characterization capability using an ultrasonic array is demonstrated. It is shown that the effect is particularly important for the accurate sizing of small defects.

Lane, C. J. L.; Wilcox, P. D.

2012-05-01

100

Dense, finely, grained composite materials  

DOEpatents

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

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

1990-01-01

101

Dense, finely grained composite materials  

DOEpatents

Dense, finely grained composite materials comprising one or more ceramic phase or phase and one or more metallic and/or intermetallic phase or phases are produced by combustion synthesis. Spherical ceramic grains are homogeneously dispersed within the matrix. Methods are provided, which include the step of applying mechanical pressure during or immediately after ignition, by which the microstructures in the resulting composites can be controllably selected. 10 figs.

Dunmead, S.D.; Holt, J.B.; Kingman, D.D.; Munir, Z.A.

1988-10-21

102

Effect of Residual Stress and Reinforcement Geometry in AN Anisotropic Composite Rotating Disc Having Varying Thickness  

NASA Astrophysics Data System (ADS)

The influence of the thermal residual stress and reinforcement geometry on the creep behavior of a composite disc has been analyzed in this paper. The creep analysis in a rotating disc made of Al-SiC (particle/whisker) composite having hyperbolically varying thickness has been carried out using anisotropic Hoffman yield criterion and results obtained are compared with those using Hill's criterion ignoring difference in yield stresses. The steady state creep behavior has been described by Sherby's creep law. The creep parameters characterizing difference in yield stresses have been used from the available experimental results in literature. It is observed that the stresses are not much affected by the presence of thermal residual stress, while thermal residual stress introduces significant change in the strain rates in an anisotropic rotating disc. Secondly, it is noticed that the steady state creep rates in whisker reinforced disc with/without residual stress are observed to be significantly lower than those observed in particle reinforced disc with/without residual stress. It is concluded that the presence of residual stress in an anisotropic disc with varying thickness needs attention for designing a disc.

Gupta, Vandana; Singh, S. B.

2012-12-01

103

Propagation of Elastic Waves Through Inhomogeneous, Anisotropic Materials  

Microsoft Academic Search

The recent advances in the field of ultrasonic nondestructive inspection have demanded a more precise knowledge of the propagation of sound beams within materials. Quantitative models for propagation of ultrasonic fields from a transducer can be used as tools to both analyze the inspection data and to predict inspection results. An approximate Gauss -Hermite model was developed a few years

Ali Minachi

1992-01-01

104

Negative Index of Refraction in Anisotropic Nonmagnetic Materials  

Microsoft Academic Search

We analyze the possibility of negative refractive index and\\/or negative refraction of energy flow in a uniaxial nonmagnetic dielectric material. It is shown that an extraordinary p-polarized electromagnetic wave can exhibit a negative refraction provided the parallel (with respect to the optical axis) and perpendicular components of the permittivity have different signs. Such a situation can be encountered near phonon

V. Dvo?ák; P. Kužel

2006-01-01

105

Negative Index of Refraction in Anisotropic Nonmagnetic Materials  

Microsoft Academic Search

We analyze the possibility of negative refractive index and\\/or negative refraction of en- ergy flow in a uniaxial nonmagnetic dielectric material. It is shown that an extraordinary p-polarized electromagnetic wave can exhibit a negative refraction provided the parallel (with respect to the optical axis) and perpendicular components of the permittivity have different signs. Such a situation can be encountered near

V. DVO

106

Creep damage and life analysis of anisotropic materials  

Microsoft Academic Search

Summary  ?This paper provides a short survey of some recent advances in the mathematical modelling of materials behaviour under creep\\u000a conditions. The tertiary creep phase is accompanied by the formation of microscopic cracks on the grain boundaries in such\\u000a a way so that damage accumulation occurs. The paper is divided into three parts. Firstly, the damage state in a uniaxial tension

J. Betten

2001-01-01

107

A 3D displacement measurement methodology for anisotropic porous cellular foam materials  

Microsoft Academic Search

This paper presents a new testing methodology for three dimensional (3D) full-field displacement mapping at the surface of elastic materials under static loading, here with a special focus on macroscopic behaviour of an anisotropic porous cellular foam. Three displacement components on four adjacent surfaces are estimated for cubic samples of the foam using a dual-camera 3D image correlation system. The

Rémi Guastavino; Peter Göransson

2007-01-01

108

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

109

Dynamic material parameters in an anisotropic plate estimated by phase-stepped holographic interferometry  

Microsoft Academic Search

Material parameters in an anisotropic plate are determined using two non-destructive measuring techniques: real-time phase-stepped electronic speckle pattern interferometry and dual-reference-beam pulsed holographic interferometry. The first technique is used to measure the lower modes of vibration of the plate with free-free boundary conditions. Finite element analysis is then used to determine two effective Young's moduli and the in-plane shear modulus.

Karl-Evert Fällström; Kenneth Olofsson; Henrik O. Saldner; Staffan Schedin

1996-01-01

110

Composite containing coated fibrous material  

SciTech Connect

This patent describes a process for producing a composite containing at least about 10% by volume of boron nitride coated fibrous material and having a porosity of less than about 20% by volume. It comprises: forming a slurry of infiltration-promoting material and organic binding material in a liquid medium; depositing a coating of boron nitride on fibrous material leaving no significant portion thereof exposed; depositing a silicon-wettable coating on the boron nitride-coated fibrous material leaving no significant portion of the boron nitride exposed; providing the resulting coated fibrous material substantially as a layer; casting the slurry onto the coated fibrous material in an amount sufficient to form a tape therewith; evaporating the liquid medium forming a tape; firing the tape to remove the organic binding material producing a porous body; providing an infiltrant comprised of boron and silicon containing elemental boron in solution in silicon in an amount of at least about 0.1% by weight of elemental silicon; contacting the porous body with infiltrant associated infiltrating means whereby the infiltrant is infiltrated into the porous body; heating the resulting assembly in a partial vacuum to a temperature at which the infiltrant is molten and infiltrating the molten infiltrant into the porous body to produce an infiltrated product; and cooling the product producing the composite.

Singh, R.N.; Gaddipati, A.R.

1989-12-26

111

Joining of polymer composite materials  

SciTech Connect

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

Magness, F.H.

1990-11-01

112

Modern Carbon Composite Brake Materials  

Microsoft Academic Search

Carbon-carbon composites used in friction systems are becoming increasingly popular in aircrafts owing to their combination of low weight and high performance. Their current acceptance as brake materials is somewhat restrained due to two factors: cost and performance variations. Many manufacturers are taking steps toward improving their cost efficiency by utilizing lower cost precursor fibers and processing methodologies. At the

Christopher Byrne

2004-01-01

113

Durability of polymer composite materials  

Microsoft Academic Search

The purpose of this research is to examine structural durability of advanced composite materials under critical loading conditions, e.g., combined thermal and mechanical loading and shear fatigue loading. A thermal buckling model of a burnt column, either axially restrained or under an axial applied force was developed. It was predicted that for a column exposed to the high heat flux

Liu Liu

2006-01-01

114

Welds in thermoplastic composite materials  

NASA Astrophysics Data System (ADS)

Welding methods are reviewed that can be effectively used for joining of thermoplastic composites and continuous-fiber thermoplastics. Attention is given to the use of ultrasonic, vibration, hot-plate, resistance, and induction welding techniques. The welding techniques are shown to provide complementary weld qualities for the range of thermoplastic materials that are of interest to industrial and technological applications.

Taylor, N. S.

115

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

PubMed

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

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

2012-02-06

116

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

NASA Astrophysics Data System (ADS)

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

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

2007-01-01

117

Anisotropic material synthesis by capillary flow in a fluid stripe  

PubMed Central

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

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

2011-01-01

118

Transverse thermal conductance of thermosetting composite materials during their cure  

SciTech Connect

The transverse thermal conductance of thermosetting advanced composite materials during their cure was modeled analytically and then investigated experimentally. AS4/3501-6 graphite/epoxy was used for the experiments. A model for the effective transverse conductivity of a material with cylinders arranged in rectangular order, first derived by Lord Rayleigh was modified to account for the possible effects of a fiber/resin contact resistance and for the ransversely anisotropic behavior of the composites' thermal conductivity. A model was derived that accounts for the effect of resin heat generation on the measured thermal conductivity of an uncured thermosetting composite. These models were experimentally verified using a guarded hot plate apparatus to measure the thermal conductivity of the graphite/epoxy laminates as a function of independent cure variables. 29 refs.

Farmer, J.D.; Covert, E.E.

1993-01-01

119

Transverse thermal conductance of thermosetting composite materials during their cure  

SciTech Connect

The transverse thermal conductance of thermosetting advanced composite materials during their cure was modeled analytically and then investigated experimentally. AS4/3501-6 graphite/epoxy was used for the experiments. A model for the effective transverse conductivity of a material with cylinders arranged in rectangular order, first derived by Lord Rayleigh, was modified to account for the possible effects of a fiber/resin contact resistance and for the transversely anisotropic behavior of the composites' thermal conductivity. A model was derived that accounts for the effect of resin heat generation on the measured thermal conductivity of an uncured thermosetting composite. These models were investigated experimentally using a guarded hot plate apparatus to measure the thermal conductivity of the graphite/epoxy laminates as a function of independent cure variables. Good agreement was found between the models and the experimental data. 80 refs.

Farmer, J.D.; Covert, E.E. (Massachusetts Inst. of Technology, Cambridge, MA (United States))

1994-04-01

120

Composite materials and their use in structures  

Microsoft Academic Search

This book attempts to provide a basic fundamental understanding of the physical and mathematical aspects of the materials system and structures comprised of composite materials. The introduction discusses the nature and scope of composite materials, the strengthening processes used in the manufacture of alloys, and the needs for composite materials. Then various types of fiber-reinforced materials are examined, first by

J. R. Vinson; T. W. Chou

1975-01-01

121

An efficient method for thermal analysis of composites containing anisotropic continuous fibers and an arbitrary number of interfacial layers  

Microsoft Academic Search

Based on the existing composite cylinder model, the analysis of anisotropic fiber-reinforced composites comprising an arbitrary number of interfacial layers is transformed into that of a cylindrical assemblage consisting of multiple coaxial circular cylinders. Analytical expressions of the deformations and stresses in the cylindrical assemblage are introduced. A recursive formula is obtained from the continuity conditions of the deformations and

L. H. You

2004-01-01

122

Damage and fracture mechanics of composite materials  

NASA Astrophysics Data System (ADS)

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 ones (metals) according to the basic properties, such as density, elastic modulus and also long-time and short-time strength, shows their superiority over traditional materials, when weight is a major design factor, like in the aerospace industry. Most composite materials of interest to aerospace applications have been adequately characterized under static loading conditions. Related work to study their fracture behaviour has been limited. Since most failure mechanisms involve crack growth and/or delamination, design of such components requires knowledge and understanding of their fracture properties. This thesis includes an experimental and analytical investigation of fracture characteristics of composite materials. The post-peak response of notched specimens subjected to uniaxial cyclic loading is established to evaluate the fracture energy associated with progressive matrix damage and subsequent crack growth. A total of 75 uniaxial tension specimens were tested. The experimental work consisted of first testing several un-notched specimens with different thickness (number of layers) to determine the initial and secondary elastic modulus as well as the tensile strength. The investigation studied the effect of the various fracture parameters, including thickness, fiber orientation, and crack width ratio (a/w) on the behaviour of crack propagation, peak load, and post-peak response. The specimens used in this research were prepared using the vacuum bagging technique, with a chosen number of fiber glass cloth layers and fiber orientation. The experimental results provided information regarding the peak load, post-peak response, fracture energy and stress intensity factor of the notched composite materials specimen under repeated loading/unloading cyclicity. The load versus crack opening displacement as well as crack length, fracture toughness and fracture energy versus number of loading cycles are produced for different specimens. Based on the experimental results, concepts of fracture mechanics are applied to evaluate stiffness degradation, fracture toughness and fracture energy evolution associated with crack growth. In addition, a linear elastic fracture mechanics approach combined with continuum damage representation is used to predict the response of specimens (peak load and crack opening displacement). This effort has also generated a new crack band model for computational purposes. A new formula is derived to compute delamination and interlaminar buckling loads using the finite element method. By matching the analytical near crack tip displacement field with the finite element approximation, the crack-axial stress magnitude is established, and therefore an accurate assessment of the buckling load responsible for delamination of composites is accurately evaluated. A comprehensive derivation of the fracture inelastic zone size and shape in anisotropic solids is presented. An adaptation of Hill's failure criterion is used to derive the shape of the inelastic zone. The findings explain the "banded" shape of the damage zone observed during crack growth.

Abdussalam, Saleh Ramadan

123

Optical properties of composite systems based on anisotropic fibers with axisymmetric stacking  

NASA Astrophysics Data System (ADS)

Simulation of optical properties of composite systems in the form of bundles consisting of anisotropic fibers with axisymmetric stacking is carried out in the ray-optics approximation. It is shown that such composite systems observed by the interference-polarization method for the case of crossed Nicol prisms produce figures in the form of a system of concentric light and dark rings, in the center of which there is a dark cross. The results of simulations applied to microsections of the human tooth taking into account the numerical values of the constituent components of the dentin (the sizes and optical properties of the dentinal tubules and of the matrix, etc.) are compared with the experiment. A good qualitative agreement between the calculation and the experiment for the observed patterns is found in the cases of some samples (molar and premolar).

Zolotarev, V. M.

2004-10-01

124

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

NASA Astrophysics Data System (ADS)

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

Eberlein, Claudia; Zietal, Robert

2012-12-01

125

Optimizing Material Use in Blade Design by Improving Failure Prediction Methodology and Introducing Damage Tolerant Concepts in FRP Composites  

Microsoft Academic Search

Preliminary results are presented in this work, concerning the validation of a reliable FEM tool under development, featuring damage tolerant concepts, to enhance design capabilities and optimize material use in large composite structures. User defined material constitutive equations concerning anisotropic non- linearity and material stiffness degradation as a result of damage accumulation, are implemented to model inherent damage tolerance of

A. E. Antoniou; T. P. Philippidis

126

Properties of Five Toughened Matrix Composite Materials.  

National Technical Information Service (NTIS)

The use of toughened matrix composite materials offers an attractive solution to the problem of poor damage tolerance associated with advanced composite materials. In this study, the unidirectional laminate strengths and moduli, notched (open-hole) and un...

R. J. Cano M. B. Dow

1992-01-01

127

Composite, Ordered Material Having Sharp Surface Features.  

National Technical Information Service (NTIS)

A composite material having sharp surface features includes a recessive phase and a protrusive phase, the recessive phase having a higher susceptibility to a preselected etchant than the protrusive phase, the composite material having an etched surface wh...

B. R. D'Urso J. T. Simpson

2005-01-01

128

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

SciTech Connect

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

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

2005-08-05

129

Extinction theorem and propagation of electromagnetic waves between two anisotropic materials  

Microsoft Academic Search

.  We systematically investigate the reflection and refraction of an\\u000a electromagnetic wave between two semi-infinite anisotropic\\u000a magnetoelectric materials. Using the integral formulation of Hertz\\u000a vectors and the principle of superposition, we generalize the\\u000a extinction theorem and derive the propagation characteristics of\\u000a wave. Applying the results obtained, we find a general origin of\\u000a Brewster effect. We also show that, through choosing appropriate

W. X. Shu; Z. Ren; H. L. Luo; F. Li

2007-01-01

130

An anisotropic viscoelastoplastic model for composites—sensitivity analysis and parameter estimation  

Microsoft Academic Search

Because of their potential in achieving many performance enhancements, composite material systems (e.g. fiber-reinforced composites) are presently called upon to operate under wide range of stresses, temperatures, and loading rates. This in turn requires the development of general material models to capture the significant effects of anisotropy on both elastic and inelastic responses. The starting point in the present contribution

A. F. Saleeb; T. E. Wilt; N. R. Al-Zoubi; A. S. Gendy

2003-01-01

131

A RESEARCH REVIEW ARTICLE ON COMPOSITE MATERIAL  

PubMed Central

The search of aesthetic dental material is on. Composites are a material of choice in this category. Composite have developed over past few years and increased use of material is in demand. This article gives us a brief knowledge of existing and newer composites.

CHOKSI, DIPTI; IDNANI, BARKHA

2013-01-01

132

Optimum condition of anisotropic plasma etching for improving bending properties of ionic polymer-metal composites.  

PubMed

We presented an anisotropic plasma etching technique by reactive ion etcher (RIE) as a new pretreatment method of fabrication of ionic polymer-metal composite (IPMC). We already found that the new technique provided large displacement to the fabricated IPMC in the presence of low applied voltage. However, we did not examine the optimum condition for the anisotropic plasma etching. In this research, we tried to figure out optimum treatment condition of film in etcher. Nafion (by DuPont) films were etched using various etching time and shadow masks with various slit and space sizes. The etched samples were plated with Pt at top and bottom side by Oguro's reduction method. The surface morphology of fabricated IPMCs was characterized by SEM. And, we've measured surface resistance, bending displacement, and driving force in order to check the IPMC properties out. Here, we found that optimum condition for pre-treatment of Nafion was 1 min for etching time under shadow mask with 200 microm slit and 100 microm space. PMID:20358943

Choi, N J; Lee, H K; Jung, S; Park, K H

2010-05-01

133

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

134

Composite material heat pipe radiator  

SciTech Connect

Organic matrix composite material is recognized for its significant strength to weight ratio when compared to metal and consequently was investigated for reducing the mass of heat pipes for future space missions. The particular heat pipe that was constructed and tested was made from an organic matrix composite material applied to a linear of titanium tubing spun to foil thickness (0.076 mm). The thin liner transitioned to heavier-walled ends which allowed the tubing to be sealed using conventional welding. More specifically, the heat pipe was 1.14 m long, 24 mm in diameter and had a mass of 0.165 kg. Water was the working fluid. The heat pipe was tested in a Thermacore thermal vacuum chamber under hot and cold wall operating conditions. The heat load dissipated ranged from 10 to 60 watts. Heat pipe operating temperatures varied from 278 K to 403 K. After testing, the heat pipe was delivered to NASA JSC where future thermal vacuum chamber tests are planned. {copyright} {ital 1996 American Institute of Physics.}

Gernert, N.J.; Sarraf, D.B. [Thermacore, Inc., 780 Eden Road, Lancaster, Pennsylvania 17601 (United States); Guenther, R.J. [Battelle, Pacific Northwest Laboratories, Richland, Washington 99352 (United States); Hurlbert/, K.M. [NASA Johnson Space Center, 2101 NASA Road, 1 Houston, Texas 77058-3696 (United States); EC3

1996-03-01

135

Anisotropic thermal diffusivity characterization of aligned carbon nanotube-polymer composites.  

PubMed

The anisotropic thermal diffusivity of aligned carbon nanotube-polymer composites was determined using a photothermoelectric technique. The composites were obtained by infiltrating poly-dimethyl siloxane (PDMS) in aligned multiwall CNT arrays grown by chemical vapor deposition on silicon substrates. The thermal diffusivities are insensitive to temperature in the range of 180 K-300 K. The thermal diffusivity values across the alignment direction are approximately 2-4 times smaller than along the alignment direction and larger than effective media theory predictions using reported values for the thermal diffusivity of millimeter thick aligned multiwall carbon nanotube arrays. The effective room temperature thermal conductivity of the composite along the carbon nanotube alignment direction is at least 6X larger than the thermal conductivity of the polymer matrix and is in good agreement with the effective media predictions. This work indicates that infiltration of long and aligned carbon nanotube arrays is currently the most efficient method to obtain high thermal conductivity polymer composites. PMID:17450929

Borca-Tasciuc, T; Mazumder, M; Son, Y; Pal, S K; Schadler, L S; Ajayan, P M

136

Novel properties of wave propagation in biaxially anisotropic left-handed materials  

NASA Astrophysics Data System (ADS)

Some physically interesting properties and effects (including the quantum effects) of wave propagation in biaxially anisotropic left-handed materials are investigated in this paper: (i) we show that in the biaxially gyrotropic left-handed material, the left-right coupling of circularly polarized light arises due to the negative indices in permittivity and permeability tensors of gyrotropic media; (ii) it is well known that the geometric phases of photons inside a curved fiber in previous experiments often depend on the cone angles of solid angles subtended by a curve traced by the direction of wave vector of light, at the center of photon momentum space. Here, however, for the light propagating inside certain anisotropic left-handed media we will present a different geometric phase that is independent of the cone angles; (iii) the extra phases of electromagnetic wave resulting from the instantaneous helicity inversion at the interfaces between left- and right-handed (LRH) media is also studied in detail by using the Lewis-Riesenfeld invariant theory. Some interesting applications (e.g., controllable position-dependent frequency shift, detection of quantum-vacuum geometric phases and helicity reversals at the LRH interfaces etc.) of above effects and phenomena in left-handed media is briefly discussed.

Shen, J. Q.

2004-06-01

137

Isotropic and anisotropic Raman scattering from molten LiCl–CsCl mixtures: Composition and temperature effects  

Microsoft Academic Search

Molten mixtures of lithium chloride and cesium chloride have been studied using Raman spectroscopy at temperatures up to 850 °C. Reduced isotropic and anisotropic Raman relative intensities have been measured at different compositions and temperatures. The spectra of the mixtures show two bands with ‘‘characteristic’’ frequencies ?Cs and ?Li close to the frequencies of the bands of the pure components.

G. N. Papatheodorou; S. G. Kalogrianitis; T. G. Mihopoulos; E. A. Pavlatou

1996-01-01

138

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

139

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

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

140

Easy fabrication and resistivity-temperature behavior of an anisotropically conductive carbon nanotube-polymer composite.  

PubMed

An easy fabrication method comprising a slit die extrusion-hot stretch-quench process was used to make carbon nanotubes (CNTs) filled with anisotropically conductive polymer composite (ACPC). CNTs were first premixed with polycarbonate (PC) by coagulation and then melt mixed with polyethylene (PE). During extrusion, the CNT/PC/PE composite was subjected to hot stretching to make the CNT/PC phase form in situ an oriented conductive fibril assembly in the PE matrix. Finally the aligned CNT/PC short fibrils were quenched to preserve their structure. The resultant CNT/PC/PE composite exhibited strong anisotropy in conductivity. This method has the advantages of giving a highly oriented structure with good control of electrical anisotropy as well as the ability to be fabricated in a high rate manner. Temperature-resistivity behavior was investigated by observing the resistivity during isothermal treatment (IT) as well as nonisothermal treatment (NIT). Percolation behavior was seen in the isolated direction during the first IT at 180 degrees C. This was a result of a disordering-induced conductive network. In addition, the positive temperature coefficient (PTC) effect attenuated with IT duration. This was seen in contrast to the remaining negative temperature coefficient (NTC). The unique evolution of PTC and NTC effects originated from the ACPC's special conductive network. It can be seen that this is composed of the originally connected "intrinsic pathway" and isolated "potential pathway". PMID:20030304

Li, Bo; Zhang, Yi-Chuan; Li, Zhong-Ming; Li, Sha-Ni; Zhang, Xiao-Na

2010-01-21

141

Fe-nanoparticle coated anisotropic magnet powders for composite permanent magnets with enhanced properties  

NASA Astrophysics Data System (ADS)

Utilizing the chemical reduction of FeCl2 with NaBH4 in the presence of 2:17 Sm-Co powders, we synthesized composite Sm(Co0.699Fe0.213Cu0.064Zr0.024)7.4/nano-Fe anisotropic hard magnetic powders. The average particle size of the hard magnetic core powder was 21 ?m while the soft magnetic Fe nanoparticles deposited uniformly on the core powder had a particle size smaller than 100 nm. Different reaction protocols, such as immersion of the hard magnetic core powder in each reagent, the use of microemulsion (micelle) technique, or doubling the weight ratio of FeCl2 to core powder, led to different degrees of magnetic coupling of the hard and soft magnetic components of the composite powder. A reaction time of 180 s led to deposition of 3.5 wt % Fe nanoparticles and improved magnetic properties of the composite powder compared to the uncoated Sm(Co0.699Fe0.213Cu0.064Zr0.024)7.4 powder. The respective magnetic hysteresis parameters were 4?M18 kOe=11.3 kG, 4?Mr=11 kG, and iHc>20 kOe with a smooth demagnetization curve.

Marinescu, M.; Liu, J. F.; Bonder, M. J.; Hadjipanayis, G. C.

2008-04-01

142

Polyolefin composites containing a phase change material  

DOEpatents

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

Salyer, Ival O. (Dayton, OH)

1991-01-01

143

Thin film dielectric composite materials  

DOEpatents

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

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

2002-01-01

144

Flexure Tests of Three Fibrous Composite Materials.  

National Technical Information Service (NTIS)

Carbon and glass/ester composites were tested for flexural stiffness and strength. The test specimens were prepared from three types of composite materials: carbon fiber cloth/vinylester, glassfiber cloth/vinylester, and glassfiber/polyester in prepreg fo...

L. Knutsson H. Bjermert

1980-01-01

145

Composite, Nanostructured, Super-Hydrophobic Material.  

National Technical Information Service (NTIS)

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 materia...

B. R. D'Urso J. T. Simpson

2005-01-01

146

Preparation and magnetic properties of anisotropic (Sm,Pr)Co5/Co composite particles  

NASA Astrophysics Data System (ADS)

Anisotropic (Sm,Pr)Co5/Co nanocomposite particles have been fabricated by chemical coating the 2 h ball milled (Sm,Pr)Co5 flakes with Co nanoparticles. The Co nanoparticles were synthesized with mean particle sizes in the range of 20-50 nm. The nanocomposite particles present [0 0 1] out-of-plane texture and improved magnetic properties, e.g., an enhanced remanent magnetization of 72 emu/g for (Sm,Pr)Co5/Co and 66 emu/g for (Sm,Pr)Co5. In addition, by using the 8 h ball milled powders (much smaller than the 2 h ball milled powders) as the starting materials, Co nanoparticles can also be successfully coated on the surface of the flakes. A plausible mechanism for the formation of Co nanoparticles on the surface of (Sm,Pr)Co5 flakes is discussed.

Wang, Xiaoliang; He, Huanlong; Wang, Fengqing; Chen, Yan; Xu, Lei; Li, Xiaohong; Zhang, Xiangyi

2012-03-01

147

Optical sensor using functionalized composite materials  

US Patent & Trademark Office Database

The invention relates to a method for sensing the presence of at least one analyte in a medium, comprising disposing in the medium a functionalized composite material such that the at least one analyte is absorbed by the functionalized composite material, the functionalized composite material having at least one optical property that is modulated by absorption of the at least one analyte; and measuring modulation of the at least one optical property of the functionalized composite material; wherein modulation of the at least one optical property of the functionalized composite material is indicative of the presence of the analyte in the medium. The invention also relates to an optical sensor for sensing the presence of at least one analyte in a medium, and a functionalized composite material having at least one optical property that is modulated upon absorption of one or more analyte.

2010-08-17

148

Dynamic compaction of particulate composite materials  

NASA Astrophysics Data System (ADS)

This paper describes the mechanical alloying + dynamic compaction flowchart for producing composites with particulate reinforcements. The combinations of components tested included aluminum silicon carbide, aluminum boron carbide, copper silicon carbide, and copper silica. Mechanical alloying produced granules of composite with reinforcements uniformly distributed in the matrix material. Dynamic compaction of mechanically alloyed granules was shown to produce high quality composite materials with crack-free structure. As the standard methods for explosive treatment lead to crack formation in bulk composites, this work included the development of a tool for treating composite materials.

Popov, V. A.; Staudhammer, K. P.; Goulbin, V. N.

2006-08-01

149

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

150

Composite Materials with Improved Properties in Compression.  

National Technical Information Service (NTIS)

Preparation of composite materials which have high strength in compression. Scientific approach is to prepare novel polymeric coupling agents. These will permit formation of multiple flexible covalent bonds between fibers as well as to matrix materials. I...

W. P. Weber

1993-01-01

151

Self-sensing structural composite materials  

Microsoft Academic Search

Self-sensing was attained in lightweight structural composite materials, including those with polymer (epoxy), carbon and ceramic (Si3N 4) matrices. Either a volume of the composite or the interlaminar interface in the composite was used as the sensor. The use of the interlaminar interface as a sensor is a new approach, which was found to be effective in continuous carbon fiber

Shoukai Wang

2002-01-01

152

The interaction between lining materials and composite resin restorative materials.  

PubMed

The effects of four lining materials, Dycal, Procal, Cavitec and Poly F cement on Adaptic and Concise have been investigated in vitro. The parameters studied were surface roughness, hardness and colour both with and without an intermediate (or bonding) resin being present between the restorative material and the liner. The effects of the four liners on the composites varied both between the lining materials themselves and with the composite resin. Two materials, Procal and Dycal, had little interaction with the composites, provided an intermediate resin was used with the latter. Cavitec appeared to have an adverse reaction with the composites and Poly F, whilst having no effect on the colour of the composites, did increase surface roughness. The adverse effects of linig materials were ascribed to minor constituents, particularly methyl salicylate, present in the formulation. PMID:6453213

Lingard, G L; Davies, E H; Von Fraunhofer, J A

1981-03-01

153

Dancing Discs: Bending and Twisting of Soft Materials by Anisotropic Swelling  

NASA Astrophysics Data System (ADS)

Soft materials, e.g. biological tissues and gels, undergo morphological changes, motion, and instabilities when subjected to external stimuli. Tissues can exhibit residual internal stresses induced by growth, and generate elastic deformations to move in response to light or touch, curl articular cartilage, aid in seed dispersal, and actuate hygromorphs, such as pine cones. Understanding the dynamics of such osmotically driven movements, in the influence of geometry and boundary conditions, is crucial to the controlled deformation of soft materials. We examine how thin elastic plates undergo rapid bending and buckling instabilities after anisotropic exposure to a favorable solvent that swells the network. An unconstrained beam bends along its length, while a circular disc bends and buckles with multiple curvatures. In the case of a disc, a large-amplitude transverse travelling wave rotates azimuthally around the disc. Theoretical interpretations inspired by the complementary thermal expansion problem of transient shape changes triggered by time-dependent heating are presented and allow collapse of time-dependent data on universal curves. Understanding the dynamics of strain-driven shape changes provides new insight into natural systems and control of advanced functional materials.

Holmes, Douglas; Roché, Matthieu; Sinha, Tarun; Stone, Howard

2011-03-01

154

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

NASA Astrophysics Data System (ADS)

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

Souhar, Youssef; Rémy, Benjamin; Degiovanni, Alain

2013-02-01

155

Stress distribution in antifriction composite materials  

Microsoft Academic Search

The optimum shape of hard inclusions in a composite material, irrespective of the magnitude of load and mode of its application to the surface, is a spheroid or ellipsoid of revolution. The characteristic linear size of a hard inclusion should be greater than the calculated diameter of a single spot of contact. If a composite material is to exhibit high

L. V. Zabolotnyi

1979-01-01

156

Electromagnetic shielding effectiveness of composite material  

Microsoft Academic Search

The purpose of this paper is to present an engineering study of the electromagnetic shielding effectiveness of composite materials used in space applications. The objective of the study is to identify and quantify the important electrical characteristics of composite materials proposed as substitutes for conventional metal-based structural elements of spacecraft. Current design practices utilized by various developers of spacecraft, particularly

Patrick J. Serna; Gary H. Liechty

1999-01-01

157

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

158

Structure and properties of hybrid composite materials  

NASA Astrophysics Data System (ADS)

The structure and interfacial interaction are studied in the hybrid aluminum-matrix composite materials fabricated by reactive casting combined with mechanical mixing of fillers with a metallic melt. The following types of hardening are considered: hardening by ceramic particles and by the phases formed as isolated inclusions or coatings on ceramic particles during in situ reactions. The hardness and tribological properties of the composite materials as functions of their compositions are discussed.

Chernyshova, T. A.; Kobeleva, L. I.; Bolotova, L. K.; Katin, I. V.

2013-03-01

159

Composite Dielectric Materials for Electrical Switching  

SciTech Connect

Composites that consist of a dielectric host containing a particulate conductor as a second phase are of interest for electrical switching applications. Such composites are "smart" materials that can function as either voltage or current limiters, and the difference in fimction depends largely upon whether the dielectric is filled to below or above the percolation threshold. It also is possible to combine current and voltage limiting in a single composite to make a "super-smart" material.

Modine, F.A.

1999-04-25

160

NUMERICAL STUDY OF GOOS-HÃ?NCHEN SHIFT ON THE SURFACE OF ANISOTROPIC LEFT-HANDED MATERIALS  

Microsoft Academic Search

Abstract—The Goos-H¨ anchen shift on the surface when an optical beam,is obliquely incident from one isotropic right-handed material (RHM) into another biaxial anisotropic left-handed material (BA- LHM) is numerically studied with the finite difference time domain (FDTD) method based on the Drude dispersive models. The analytical expression of the Goos-H¨ anchen shift is firstly presented,moreover the condition for the existence

Wei Ding; Liang Chen; Chang-Hong Liang

2008-01-01

161

Latent heat nano composite building materials  

Microsoft Academic Search

Heat storage for heating and cooling of buildings reduces the conventional energy consumption with a direct impact on CO2 emissions. The goal of this study was to find the physico-chemical fundamentals for tailoring phase change material (PCM)-epoxy composites as building materials depending on phase change temperature and latent heat using the optimal geometry for each application. Thus, some nano-composite materials

M. Constantinescu; L. Dumitrache; D. Constantinescu; E. M. Anghel; V. T. Popa; A. Stoica; M. Olteanu

2010-01-01

162

Architecture and properties of anisotropic polymer composite scaffolds for bone tissue engineering.  

PubMed

Bone is a complex porous composite structure with specific characteristics such as viscoelasticity and anisotropy, both in morphology and mechanical properties. Bone defects are regularly filled with artificial tissue grafts, which should ideally have properties similar to those of natural bone. Open cell composite foams made of bioresorbable poly(L-lactic acid) (PLA) and ceramic fillers, hydroxyapatite (HA) or beta-tricalcium phosphate (beta-TCP), were processed by supercritical CO2 foaming. Their internal 3D-structure was then analysed by micro-computed tomography (microCT), which evidenced anisotropy in morphology with pores oriented in the foaming direction. Furthermore compressive tests demonstrated anisotropy in mechanical behaviour, with an axial modulus up to 1.5 times greater than the transverse modulus. Composite scaffolds also showed viscoelastic behaviour with increased modulus for higher strain rates. Such scaffolds prepared by gas foaming of polymer composite materials therefore possess suitable architecture and properties for bone tissue engineering applications. PMID:16051346

Mathieu, Laurence Marcelle; Mueller, Thomas L; Bourban, Pierre-Etienne; Pioletti, Dominique P; Müller, Ralph; Månson, Jan-Anders E

2005-07-27

163

Spectral representation theory of graded composite materials  

NASA Astrophysics Data System (ADS)

In graded composite materials, the physical properties can vary continuously in space and it may give different physical phenomena when compared with homogeneous materials. The Bergman-Milton spectral representation is a rigorous mathematical formalism to express the effective dielectric constant of nongraded composite materials [1]. In this study, we consider a material (rather than microsture [2]) graded composites, and generalize the Bergman-Milton spectral representation to extract the spectral density function for the effective dielectric constant of this graded composite material in the frequency domain [3]. Analytic and numerical solution will be presented for graded films and graded spheres. [1] D. J. Bergman, Phys. Rev. B 14, 4304 (1976). [2] J. P. Huang, K. W. Yu, G. Q. Gu, M. Karttunen, Phys. Rev. E 67, 051405 (2003). [3] L. Gao, J. P. Huang, K.W. Yu, Eur. Phys. J. B 36, 475 (2003).

Chan, K. L.; Kwok, C. M.; Yu, K. W.

2008-03-01

164

Localisation of shear fracture networks in anisotropic materials: influence of strain rate and material strength  

Microsoft Academic Search

This contribution presents an experimental study of deformation localisation and the formation of fracture networks in elastoviscoplastic layered materials under pure shear boundary conditions. The mechanical properties of the analogue mixtures, which are made of plasticine, have been used to analyse the transition from models in which deformation is accommodated by homogeneous viscous flow to systems controlled by a few

E. Gomez-Rivas; A. Griera

2009-01-01

165

Localisation of shear fracture networks in anisotropic materials: influence of strain rate and material strength  

NASA Astrophysics Data System (ADS)

This contribution presents an experimental study of deformation localisation and the formation of fracture networks in elastoviscoplastic layered materials under pure shear boundary conditions. The mechanical properties of the analogue mixtures, which are made of plasticine, have been used to analyse the transition from models in which deformation is accommodated by homogeneous viscous flow to systems controlled by a few active faults. Two series of experiments have been studied: (a) the same material was deformed at different strain rates and (b) four materials with different mechanical properties were deformed at a fixed strain rate. The results show that strain rate and viscous ductility define a change on the degree of deformation localisation and the geometry of fracture networks. The increase of deformation also produces changes on the mechanical behaviour of the systems and the type of deformation. Localisation of fracture networks is enhanced when strain rate is increased. Moreover, there is a progressive increment in the relationship between fracture displacement and fracture length related to the strain rate applied to the system. This experimental observation is also corroborated by a series of simple finite element linear elastoviscous simulations. In these models, a horizontal inclusion within a matrix simulates a pre-existing fracture. The displacement along this fracture is tracked at all times using some selected nodes located at the two walls. The results indicate that there is a dependency of fracture displacements on the strain rate. A deviation between shear strains registered by fractures and the one applied by the boundary conditions is also detected, especially at low strain. The degree of localisation and the nucleation of shear fractures also depend strongly on the viscous ductility and strength of the analogue material. The raise of the material stiffness causes an increase of the length of fractures and displacements along them. This fact must be associated to the competition between the viscous stress relaxation of the material related to ductile flow and the brittle behaviour associated to the propagation of fractures. When the dominant process is ductile flow the material is able to relax the deviatoric stress at fault tips and the propagation of fractures is inhibited. The presented models are illustrative examples of the transition between brittle and ductile behaviour.

Gomez-Rivas, E.; Griera, A.

2009-04-01

166

Autophagous spacecraft composite materials for orbital propulsion  

Microsoft Academic Search

We are developing structural polymer composite materials that can be converted into fuels and combusted with oxidizers for orbital propulsion of spacecraft. We have identified candidate materials and demonstrated sustained combustion with nitrogen tetroxide (NTO) as an oxidizer. To improve reaction chemistry we have evaluated several energetic additives. Detailed material compatibility tests were conducted to identify stable combinations of structural

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

2002-01-01

167

High temperature composite materials and magnetodielectric composites for microwave application  

NASA Astrophysics Data System (ADS)

In the part I, we investigated the microstructures, mechanical properties, and oxidation behavior of hot pressed BN in the presence of sintering additives Al2O3, Y2O3 and SiO2. BN platelets size in the sintered samples grew from ˜5 to ˜30 times for the use of all three oxides, and the use of Al2O3 and Y2O3, correspondingly. The excessive growth of BN platelets in samples containing Al2O3 and Y2O 3 caused them to misalign which, in turn, resulted in its low relative density (92.0%). The use of SiO2 mitigated this grain growth so that BN platelets aligned better to gain a higher relative density (99.5%). Flexural strength and elastic modulus of BN were proportional to their densities. Oxidation experiments conducted at 1200°C in flowing dry air showed borate glass droplets were formed on all of oxidized BN samples. The addition of SiO2 resulted in the formation of a glass layer before the appearance of these glass droplets. The presence of glass droplets was a result of the poor wetting of liquid B2O3 on BN and the dominance of the formation of B2O3 to its evaporation. Their size evolution described the "breadth figure" theory, similar to the formation of water droplets on a flat surface from the saturated water vapor air. Substructures observed inside the glass droplets contained high and consistent Al:Y atomic ratio (5:7) in all samples. The evaporation of B2O 3 isolated Al2O3, Y2O3 in the form of immiscible liquid phase to borate. In the part II, we investigated the formulation of equivalent permittivity and permeability with isotropic and anisotropic Co2Z-polymer composition. These two properties of isotropic Co2Z-LDPE/Co2Z-Silicone composites increased with Co2Z composition. However, their permittivity was always higher than that of their permeability. Permittivity and permeability of anisotropic Co2Z-Silicone composites were split into high and low values along the parallel and perpendicular directions to the alignment direction of Co2Z particles. The separation at 20 vol% Co2Z was strongest, attained 46% anisotropy so that its parallel permeability approached closer to that of its perpendicular permittivity. However, the low permittivity of Co2Z required a higher electric field to increase its particles' alignment.

Do, Thanh Ba

168

Delamination Growth in Composite Materials.  

National Technical Information Service (NTIS)

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 geomet...

J. W. Gillespie L. A. Carlsson R. B. Pipes R. Rothschilds B. Trethewey

1986-01-01

169

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

SciTech Connect

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

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

1994-12-01

170

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

171

A Statistical Theory of Composite Materials Strength  

Microsoft Academic Search

A statistical tensile failure theory of composite materials with uniaxially oriented fibers is proposed. In the theory, the strength of fibers is assumed to be a statistical quantity and the fibers around a broken fiber are supposed to be subjected to localized stress concentra tions. The number of broken fibers in a layer of composite as a function of average

Yuntian Zhu; Benlian Zhou; Guanhu He; Zongguang Zheng

1989-01-01

172

Carbon-Carbon Materials and Composites.  

National Technical Information Service (NTIS)

Carbon-fiber-reinforced carbon matrix (carbon-carbon) composites have received increasing emphasis over the past 15 years. These materials have been used primarily in the aerospace and automotive industries. Carbon-carbon composites can be made in a wide ...

D. D. Edie J. D. Buckley

1992-01-01

173

Self-healing structural composite materials  

Microsoft Academic Search

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

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

2003-01-01

174

Method to fabricate layered material compositions  

SciTech Connect

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

175

Laser welding of discontinuously reinforced composite materials  

NASA Astrophysics Data System (ADS)

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

Shiganov, I. N.

1999-01-01

176

Dynamic compressive behavior of thick composite materials  

Microsoft Academic Search

The effect of strain rate on the compressive behavior of thick carbon\\/epoxy composite materials was investigated. Falling weight impact and split Hopkinson pressure bar systems were developed for dynamic characterization of composite materials in compression at strain rates up to 2000 s–1. Strain rates below 10 s–1 were generated using a servohydraulic testing machine. Strain rates between 10 s–1 and

H. M. Hsiao; I. M. Daniel; R. D. Cordes

1998-01-01

177

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

178

Composite materials: composition, properties and clinical applications. A literature review.  

PubMed

Various composite materials are available today for direct restorative techniques. The most well-known materials are the hybrid composites. This technology, based on methacrylates and different types of filler coupled with silanes, has been continuously improved. Disadvantages such as polymerisation shrinkage, bacterial adhesion and side effects due to monomer release still remain. The aim of material development is to eliminate or at least reduce these negative factors by adapting the individual components of the material. With ormocers, the methacrylate has been partially replaced by an inorganic network. According to recent studies, the biocompatibility was not improved in all cases. The development of compomer was an attempt to combine the positive properties of glassionomers with composite technology. This has only partially succeeded, because the fluoride release is low. In an in-situ study, a caries protective effect could be shown at least in the first days following filling placement with concurrent extra-oral demineralisation. By replacing the chain-monomers in the composite matrix by ring-shaped molecules, a new approach to reduce polymerisation shrinkage was investigated. A new group of materials, the siloranes, has been developed. Siloranes are hydrophobic and need to be bonded to the dental hard tissue using a special adhesive system. Long-term clinical studies are still needed to prove the superiority of this new group of materials over modern hybrid composites. PMID:21243545

Zimmerli, Brigitte; Strub, Matthias; Jeger, Franziska; Stadler, Oliver; Lussi, Adrian

2010-01-01

179

Evaluation of Hybrid Composite Materials.  

National Technical Information Service (NTIS)

An examination of the available fiber prepregs clearly suggests that the higher stiffness and strength materials such as boron and graphite have higher price levels than the lower stiffness and strength prepregs such as Kevlar-49 and S-Glass. A logical ou...

S. V. Kulkarni B. W. Rosen H. C. Boehm

1975-01-01

180

3-D textile reinforcements in composite materials  

SciTech Connect

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

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

1999-11-01

181

Nonmetallic materials and composites at low temperatures  

Microsoft Academic Search

This book presents articles by leading scientists who explore the cryogenic behavior of such materials as epoxies, polyethylenes, polymers, various composites, and glasses. Examines the thermal and dielectric properties of these materials, as well as their elasticity, cohesive strength, resistance to strain and fracturing, and applications. Topics include thermal properties of crystalline polymers; thermal conductivity in semicrystalline polymers; ultrasonic absorption

G. Hartwig; D. Evans

1982-01-01

182

Prediction of Crushing Stress in Composite Materials  

Microsoft Academic Search

A simple mathematical model for predicting the crushing stress of composite materials was derived and presented in this article. The present knowledge of fracture mechanics and strength of materials are used as the basis for the model. The fracture mechanics part of the analysis was based on energy release rate approach; the energy release rate, G, of the proposed model

S. Goh; H. Ku; S. L. Ang

2008-01-01

183

Recent developments in composite materials structures; Proceedings of the Symposium, ASME Winter Annual Meeting, Dallas, TX, Nov. 25-30, 1990  

NASA Astrophysics Data System (ADS)

The present conference discusses the parametric design of composite ducts and pressure vessels, enhanced material damping through the use of thermoelasticity, a performance simulation of structural composite rods, a stress analysis of anisotropic laminated circular cylindrical shells, the stresses in rotating (orthotropic, circular) composite disks and plates, and the effects of wear tip behavior on particulate composites. Also treated are a model for compression failure in fiber composite laminates, the effect of fiber interaction on matrix and interfacial microcracking in ceramic matrix composites, the dynamic response of an external circular crack to normal stresses in a transversely isotropic material, and the pinned joint behavior of laminated holes reinforced with braided composite.

Hui, David; Sun, C. T.

184

Advanced composite materials for optomechanical systems  

NASA Astrophysics Data System (ADS)

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

Zweben, Carl

2013-09-01

185

Elastic Coupling Effects in Tapered Sandwich Panels with Laminated Anisotropic Composite Facings  

Microsoft Academic Search

A newly developed theory for the analysis of tapered sandwich panels with laminated anisotropic facings is presented. Unlike sandwich panels of uniform depth, the response of tapered sandwich panels is counterintuitive. For example, prior studies have demonstrated that a tapered cantilever sandwich beam having constant dimensions at the clamped edge and subjected to a tip load has an optimum taper

Senthil S. Vel; Vincent Caccese; Huyue Zhao

2005-01-01

186

Crack—Interface Interaction in Composite Materials  

Microsoft Academic Search

The presence of cracks has a major impact on the reliability of advanced materials, like fiber or particle reinforced composites\\u000a or laminated composites. This paper presents different aspects of the interaction between crack and interface: stress field\\u000a and fracture parameters for a crack approaching the interface and the crack deflection versus penetration for a crack with\\u000a the tip on the

Liviu Marsavina; Tomasz Sadowski

187

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

188

An anisotropic model of damage and frictional sliding for brittle materials  

Microsoft Academic Search

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

D. Halm; A. Dragon

1998-01-01

189

Characteristics of electromagnetic wave propagation in uniaxially anisotropic left-handed materials  

Microsoft Academic Search

We investigate the characteristics of electromagnetic wave propagation in uniaxially anisotropic left-handed media. We discuss mainly under what conditions anomalous reflection or refraction shall occur at the interface when propagating waves pass from one isotropic regular medium into another uniaxially anistotropic left-handed medium and under what conditions anomalous transmission shall occur when an evanescent wave is transmitted through a slab

Liangbin Hu; S. T. Chui

2002-01-01

190

Anisotropic Modeling of Shocked Single Crystals with Application to Energetic Materials  

Microsoft Academic Search

A continuum, anisotropic modeling framework has been developed for simulating shock wave propagation in single crystals of arbitrary orientation. Our modeling approach incorporates nonlinear elasticity and crystal plasticity in a thermodynamically consistent tensor formulation. Crystal plasticity is described using a model that considers dislocation motion along specified slip planes. Shear cracking along specified crystal planes is also considered. Numerical simulations,

J. M. Winey

2005-01-01

191

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

NASA Astrophysics Data System (ADS)

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.

2013-04-01

192

Natural frequency behavior of damaged composite materials  

NASA Astrophysics Data System (ADS)

Attention is given to characterizing the effect of material system, geometry, and stacking sequence on the vibration response of damaged plates of fiber-reinforced composite. Plate layups are fashioned from various composite materials and subjected to four damage cycles, and a signal analyzer is employed to study the frequency response function (FRF) of the materials. The materials employed include the AS4/3501-6, IM7/E7T1-2, and IM7/977-2 families, and numerical analyses are used for comparison. Frequencies are obtained from the experimentally established FRFs, and natural frequencies tend to decrease in the presence of extensive localized damage. The fiber is argued to dominate the response of the plate, and the experimental data are confirmed in some cases by the results of finite-element calculations.

Duggan, M. B.; Ochoa, O. O.

1992-11-01

193

Composite Materials: Properties as Influenced by Phase Geometry  

Microsoft Academic Search

This book deals with the mechanical and physical behavior of composites as influenced by composite geometry. The monograph provides a comprehensive introduction for researchers and students to modern composite materials research with a special emphasis on the influence of geometry to materials properties. Composite Materials enables the reader to a better understanding of the behavior of natural composites, improvement of

Lauge F. Nielsen

2005-01-01

194

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

PubMed Central

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

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

2010-01-01

195

Modeling of laser interactions with composite materials.  

PubMed

We develop models of laser interactions with composite materials consisting of fibers embedded within a matrix. A ray-trace model is shown to determine the absorptivity, absorption depth, and optical power enhancement within the material, as well as the angular distribution of the reflected light. We also develop a macroscopic model, which provides physical insight and overall results. We show that the parameters in this model can be determined from the ray trace model. PMID:23669848

Boley, Charles D; Rubenchik, Alexander M

2013-05-10

196

Study of the compatibility between light-cured repair materials and composite materials by holographic interferometry  

Microsoft Academic Search

Based on current trends in research on techniques for repairing composite materials, this paper focuses on the compatibility between a light-cured repair material and composite materials. The repair material used in this study is intended to find applicability in techniques for repairing damaged composite materials. Test pieces of the composite material were excited by a sinusoidal acoustic source at a

Linfeng Guo; Zhimin Zhao; Mingjuan Gao

2005-01-01

197

Load-transfer from fibre to anisotropic half-space for dilute composites  

Microsoft Academic Search

Summary  An asymptotic approach is proposed to describe the load-transfer from a single fibre to an anisotropic half-space through\\u000a weak and stiff interfaces. To start with we simplified the input boundary value problem using ratios of the elastic constants\\u000a as small parameters. The simplified boundary value problem is solved using integral transforms. Inverse transforms are approximately\\u000a expressed through elementary and special

I. V. Andrianov; V. V. Danishevs’kyy; D. Weichert

2008-01-01

198

Interlaminar fracture and damage of composite materials  

Microsoft Academic Search

Interlaminar fracture behavior of composite materials under static and cyclic loadings was studied. The fracture energy is evaluated by compliance, beam and area methods. The comparison results show that the initial fracture energy could be evaluated either by beam or area method while the crack growth resistance could be calculated by compliance method. Increases in the critical load and fracture

1988-01-01

199

Physics in ``Polymers, Composites, and Sports Materials  

Microsoft Academic Search

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

Eric Hagedorn; Milijana Suskavcevic

2007-01-01

200

Crashworthy capability of composite material structures  

Microsoft Academic Search

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

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

1997-01-01

201

Characterization of self-healing composite materials  

Microsoft Academic Search

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

Kevin John Ford

2006-01-01

202

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

203

Damping Analysis of Sandwich Composite Materials  

Microsoft Academic Search

The article presents an analysis of the damping of sandwich composites, made of PVC foam cores and laminated skins. Damping parameters are investigated using beam test specimens and an impulse technique. Damping modeling is developed using a finite element analysis which evaluated the different energies dissipated in the material directions of the core and the layers of the skins. The

Mustapha Assarar; Abderrahim El Mahi; Jean-Marie Berthelot

2009-01-01

204

Magnetic Composite Materials and Arbitrary - Relationships  

Microsoft Academic Search

This theoretical study addresses fabricating composite conducting materials with an effective arbitrary B-H relationship in the quasi-static field approximation, exhibiting new magnetic properties. The experimental results demonstrate the possibility of having linear artificial structures with negative effective magnetic permeability. The equivalent circuital model confirms the theoretical and experimental analysis. In particular, following the circuital approach we show how to obtain

Bernardo Tellini; Mauro Bologna

2010-01-01

205

Candida albicans adhesion to composite resin materials.  

PubMed

The adhesion of Candida albicans to dental restorative materials in the human oral cavity may promote the occurrence of oral candidosis. This study aimed to compare the susceptibility of 14 commonly used composite resin materials (two compomers, one ormocer, one novel silorane, and ten conventional hybrid composites) to adhere Candida albicans. Differences in the amount of adhering fungi should be related to surface roughness, hydrophobicity, and the type of matrix. Cylindrical specimens of each material were made according to the manufacturers' instructions. Surface roughness R (a) was assessed by perthometer measurements and the degree of hydrophobicity by computerized contact angle analysis. Specimens were incubated with a reference strain of C. albicans (DMSZ 1386), and adhering fungi were quantified by using a bioluminometric assay in combination with an automated plate reader. Statistical differences were analyzed by the Kruskal-Wallis test and Mann-Whitney U test. Spearman's rank correlation coefficients were calculated to assess correlations. Median R (a) of the tested composite resin materials ranged between 0.04 and 0.23 microm, median contact angles between 69.2 degrees and 86.9 degrees . The two compomers and the ormocer showed lower luminescence intensities indicating less adhesion of fungi than all tested conventional hybrid composites. No conclusive correlation was found between surface roughness, hydrophobicity, and the amount of adhering C. albicans. PMID:18810508

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

2008-09-23

206

Slow crack propagation in composite restorative materials.  

PubMed

The double-torsion test technique was used to study slow crack propagation in a set of dental composite resins including two glass-filled and two microfilled materials. The microstructure within each pair was the same but one of the resins was selfcured and the other photocured. The fracture behavior was dependent on the filler concentration and the presence of absorbed water. Wet materials fractured by slow crack growth in the range of crack velocity studied (10(-7) to 10(-3) m/s), and the microfilled composites, which contain a lower concentration of inorganic filler, had lower stress intensity factors (K1c) than the glass-filled composites tested. Dry specimens of the microfilled materials and the selfcured, glass-filled composite also showed unstable, stick-slip fracture behavior indicative of a crack blunting mechanism which leads to an elevation of the stress intensity factor for crack initiation over K1c for stable crack growth. The plasticizing effect of water increased the viscoelastic response of the materials measured by the slope of curves of slow crack growth. Analysis of fracture surfaces showed that cracks propagated at low velocities (10(-7) to 10(-5) m/s) by the apparent failure of the filler/matrix interfacial bond, and absorbed water affected the strength or fracture resistance of the interface. At high crack velocities the properties of the composite depend on the properties of the polymeric matrix, the filler, and the filler volume fraction, but at low velocities the interface is the controlling factor in the durability of these composites exposed to an aqueous environment. PMID:3584167

Montes-G, G M; Draughn, R A

1987-05-01

207

Accelerated aging of polymer composite bridge materials  

NASA Astrophysics Data System (ADS)

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

Carlson, Nancy M.; Blackwood, Larry G.; Torres, Lucinda L.; Rodriguez, Julio G.; Yoder, Timothy S.

1999-05-01

208

Accelerated Aging of Polymer Composite Bridge Materials  

SciTech Connect

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

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

1999-03-01

209

Nonlinear and anisotropic tensile properties of graft materials used in soft tissue applications  

Microsoft Academic Search

BackgroundThe mechanical properties of extracellular matrix grafts that are intended to augment or replace soft tissues should be comparable to the native tissue. Such grafts are often used in fiber-reinforced tissue applications that undergo multi-axial loading and therefore knowledge of the anisotropic and nonlinear properties are needed, including the moduli and Poisson’s ratio in two orthogonal directions within the plane

Jonathon H. Yoder; Dawn M. Elliott

2010-01-01

210

Magnetic-field-dependent energy levels in a highly anisotropic electronic material  

Microsoft Academic Search

We report the direct observation of magnetic-field-dependent energy levels in an anisotropic two-dimensional electron gas. The experiment was carried out by far-infrared-reflectivity measurements on a well studied member of the Bechgaard salts, (TMTSF)2ClO4, at low temperatures. We find two distinct bands above a threshold field and a number of unusual features which we interpret in terms of the underlying quantized

A. S. Perel; J. S. Brooks; C. J. G. N. Langerak; T. J. B. M. Janssen; J. Singleton; J. A. A. J. Perenboom; L. Y. Chiang

1991-01-01

211

Nonlinear and Anisotropic Tensile Properties of Graft Materials used in Soft Tissue Applications  

PubMed Central

Background The mechanical properties of extracellular matrix grafts that are intended to augment or replace soft tissues should be comparable to the native tissue. Such grafts are often used in fiber-reinforced tissue applications that undergo multi-axial loading and therefore knowledge of the anisotropic and nonlinear properties are needed, including the moduli and Poisson's ratio in two orthogonal directions within the plane of the graft. The objective of this study was to measure the tensile mechanical properties of several marketed grafts: Alloderm, Restore, CuffPatch, and OrthADAPT. Methods The degree of anisotropy and nonlinearity within each graft was evaluated from uniaxial tensile tests and compared to their native tissue. Results The Alloderm graft was anisotropic in both the toe and linear-region of the stress-strain response, was highly nonlinear, and generally had low properties. The Restore and CuffPatch grafts had similar stress-strain responses, were largely isotropic, had a linear-region modulus of 18 MPa, and were nonlinear. OrthADAPT was anisotropic in the linear region (131 vs 47 MPa) and was highly nonlinear. The Poisson ratio for all grafts was between 0.4 and 0.7, except for the parallel orientation of Restore which was greater than 1.0. Interpretation Having an informed understanding of how the available grafts perform mechanically will allow for better assessment by the physician for which graft to apply depending upon its application.

Yoder, Jonathon H; Elliott, Dawn M

2010-01-01

212

Hydrogel Composite Materials for Tissue Engineering Scaffolds  

NASA Astrophysics Data System (ADS)

Hydrogels are appealing for biomaterials applications due to their compositional similarity with highly hydrated natural biological tissues. However, for structurally demanding tissue engineering applications, hydrogel use is limited by poor mechanical properties. Here, composite materials approaches are considered for improving hydrogel properties while attempting to more closely mimic natural biological tissue structures. A variety of composite material microstructures is explored, based on multiple hydrogel constituents, particle reinforcement, electrospun nanometer to micrometer diameter polymer fibers with single and multiple fiber networks, and combinations of these approaches to form fully three-dimensional fiber-reinforced hydrogels. Natural and synthetic polymers are examined for formation of a range of scaffolds and across a range of engineered tissue applications. Following a discussion of the design and fabrication of composite scaffolds, interactions between living biological cells and composite scaffolds are considered across the full life cycle of tissue engineering from scaffold fabrication to in vivo use. We conclude with a summary of progress in this area to date and make recommendations for continuing research and for advanced hydrogel scaffold development.

Shapiro, Jenna M.; Oyen, Michelle L.

2013-04-01

213

Mechanical Spectroscopy of Nanostructured Composite Materials  

NASA Astrophysics Data System (ADS)

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

Mari, Daniele; Schaller, Robert; Mazaheri, Mehdi

2011-07-01

214

Conductor-polymer composite electrode materials  

DOEpatents

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

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

1984-06-13

215

Unified streamline, heatline and massline methods for the visualization of two-dimensional heat and mass transfer in anisotropic media  

Microsoft Academic Search

Many of the actual materials are anisotropic, ranging from natural products to the most sophisticated composite materials. Special emphasis needs to be devoted to the heat and mass transfer calculations in anisotropic media, and to the development of visualization tools for the transport phenomena occurring in such media, similarly to what happens with isotropic media. The most adequate tools for

V. A. F. Costa

2003-01-01

216

Combustion products from advanced composite materials.  

PubMed

Recent advances in armament and materials applications are beginning to outpace the development of adequate safety characterizations. To avoid unnecessary and restrictive regulations implemented to protect individuals from potential toxic consequences resulting from exposure to combustion products of advanced composite materials (ACM); this laboratory has begun an investigation of combustion characteristics. In this preliminary investigation we have assessed the production of particulate matter and the production of organic compounds contained in both the combustion vapor phase or associated with the particulate matter. The results of these investigations have revealed that a substantial fraction of the particulates appear to be in the respirable range and that a high number of organic compounds and potential toxicants are associated with particulate matter. These findings are the first to describe the production of potentially toxic atmospheres from the combustion of advanced composite materials and indicate the usefulness of further investigations to quantify the risk of exposure to humans. These and forthcoming data will be useful in determining proper protective equipment and precautions required to protect human health during exposures to products from the combustion of advanced composite materials. PMID:9433657

Lipscomb, J C; Kuhlmann, K J; Cline, J M; Larcom, B J; Peterson, R D; Courson, D L

1997-11-01

217

Titanium composite materials for transportation applications  

NASA Astrophysics Data System (ADS)

Discontinuously reinforced titanium alloys containing in-situ formed TiB needles are emerging as candidate materials for advanced applications. This new family of titanium composites presents technical advantages, and it can be less expensive and easily amenable for net-shape manufacturing relative to titanium metal-matrix composites developed to date. The production of a master compound by a novel and cost-effective process called self-propagating high-temperature synthesis (SHS) has been studied. This master compound could be subsequently used in an investment casting process to obtain TiB-reinforced net-shape titanium-matrix composites. The SHS technique and its features were investigated in depth before a suitable master compound was defined and produced. Cast samples obtained from the addition of the master compound have been produced and the most important issues concerning the processing, microstructure, and mechanical properties are highlighted in this paper.

García de Cortazar, M.; Agote, I.; Silveira, E.; Egizabal, P.; Coleto, J.; Le Petitcorps, Y.

2008-11-01

218

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.; Horne, Michael R.

1998-03-01

219

A self-organized anisotropic liquid-crystal plasmonic metamaterial.  

PubMed

A composite material that leads to self organization of mesogen-coated gold nanospheres is synthesized and shows enhanced anisotropic optical properties due to synergistic effects of the mesogens intrinsic birefringence and its ability to drive the self-assembly process into highly anisotropic architectures with densely packed nanospheres. Such nanoengineered matter sustains a response beyond that achievable by its individual constituents, i.e., a metamaterial. PMID:23401232

Dintinger, José; Tang, Bai-Jia; Zeng, Xianbing; Liu, Feng; Kienzler, Tobias; Mehl, Georg H; Ungar, Goran; Rockstuhl, Carsten; Scharf, Toralf

2013-02-07

220

Putting it Together: The Science and Technology of Composite Materials  

NSDL National Science Digital Library

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

2000-01-01

221

Laboratory Blast Simulator for Composite Materials Characterization  

Microsoft Academic Search

\\u000a Blasts and explosives have raised serious concerns in recent years due to the fatal injury and catastrophic damage they have\\u000a caused in the combat zones and due to industrial accidents. Owing to their lightweight and complex damage process, fiber-reinforced\\u000a composite materials have been found to have higher energy absorption capability and to be able to generate less lethal debris\\u000a than

Guojing Li; Dahsin Liu

222

Nonlinear dielectric response of periodic composite materials  

Microsoft Academic Search

This paper addresses the rigorous treatment of the tunability effect (dc electric field driven variation of the permittivity)\\u000a in a high-contrast two dimensional periodic composite (a matrix of a large dielectric constant ferroelectric material with\\u000a linear dielectric inclusions). The theoretical analysis here shows that the trend established for the case of low linear dielectric\\u000a concentrations (that the dilution with a

A. Kolpakov; A. K. Tagantsev; L. Berlyand; A. Kanareykin

2007-01-01

223

Characterization of self-healing composite materials  

NASA Astrophysics Data System (ADS)

Damage occurs in almost every composite material in the form of microcracks that develop in the epoxy matrix that binds the fibers together. Researchers at the University of Illinois Urbana Champaign have recently developed a method to reverse the effects of, or heal, damage in the epoxy matrix. Their in-situ self-healing system uses embedded microcapsules and a catalyst that trigger a romp reaction in an effort to rebond the microcracks. Several models have been developed in an effort to predict how a composite laminate damages. One model in particular, the Continuous Damage Mechanics model, CDM that has been developed at West Virginia University uses material properties that are easily obtained from standard ASTM and ISO testing methods. The CDM model has been extended at West Virginia University to incorporate the effects of a self-healing system to develop a Continuous Damage and Healing Mechanics model, CDHM. In this work, a testing procedure to characterize the autonomic healing of polymer matrix composites is outlined, as well as the regenerative effects of the self-healing system. The capability of the CDHM model to predict the material properties of the self-healing system is also addressed. The CDHM model is validated with experimental results for various laminates fabricated out of E-glass/epoxy.

Ford, Kevin John

224

Chlorhexidine-releasing methacrylate dental composite materials.  

PubMed

Light curable antibacterial, dental composite restoration materials, consisting of 80 wt% of a strontium fluoroaluminosilicate glass dispersed in methacrylate monomers have been produced. The monomers contained 40-100 wt% of a 10 wt% chlorhexidine diacetate (CHXA) in hydroxyethylmethacrylate (HEMA) solution and 60-0 wt% of a 50/50 mix of urethane dimethacrylate (UDMA) and triethyleneglycol dimethacrylate (TEGDMA). On raising HEMA content, light cure polymerisation rates decreased. Conversely, water sorption induced swelling and rates of diffusion controlled CHXA release from the set materials increased. Experimental composites with 50 and 90 wt% of the CHXA in HEMA solution in the monomer were shown, within a constant depth film fermentor (CDFF), to have slower rates of biofilm growth on their surfaces between 1 and 7 days than the commercial dental composite Z250 or fluoride-releasing dental cements, Fuji II LC and Fuji IX. When an excavated bovine dentine cylinder re-filled with Z250 was placed for 10 weeks in the CDFF, both bacteria and polymers from the artificial saliva penetrated between the material and dentine. With the 50 wt% experimental HEMA/CHXA formulation, this bacterial microleakage was substantially reduced. Polymer leakage, however, still occurred. Both polymer and bacterial microleakage were prevented with a 90 wt% HEMA/CHXA restoration in the bovine dentine due to swelling compensation for polymerisation shrinkage in combination with antibacterial release. PMID:15955557

Leung, Danny; Spratt, David A; Pratten, Jonathan; Gulabivala, Kishor; Mordan, Nicola J; Young, Anne M

2005-12-01

225

Characterization of cryogenic microcracking in carbon fiber/epoxy composite materials  

NASA Astrophysics Data System (ADS)

Polymeric composite materials have been widely utilized to take advantage of their large specific strength and stiffness. These characteristics have made them attractive for use in aerospace applications as containment structures for cryogenic fluids. However, the anisotropic, heterogeneous, and viscoelastic nature of polymeric composite materials creates a unique set of challenges for the storage of cryogenic fluids. Mismatches in thermal expansion between the fibers and the matrix in these materials result in the generation of thermal stresses at low temperatures that can ultimately cause failure in the form of microcracks that propagate throughout the material, degrading performance. This work examined the phenomenological and theoretical aspects of microcrack formation in carbon fiber/epoxy composite materials at low temperatures. Microcrack formation was initially investigated using an experimental approach. The role of the fiber and matrix type in microcracking was studied, along with the interaction between the fibers and the matrix and the effects of nanoparticle matrix modification. It was found that the fiber and matrix type had significant effects on microcrack formation, with decreased fiber moduli, decreased matrix coefficient of thermal expansion, nanoparticle modification, rubber toughening, and increased adhesion all corresponding to reduced microcracking. These improvements were achieved by reducing the thermal stresses in the materials studied and increasing the failure resistance of the laminates. It was found that the processing conditions of a laminate, namely the cure temperature, had a direct impact on microcracking by changing the stress free temperature of a material and the corresponding thermal stresses at cryogenic temperatures. The analysis of the variables that contributed to microcrack formation was used to develop a stress-based compound beam model to predict the onset temperature for microcracking in composite materials. This model was unique in that it accounted for the variation in material properties at low temperatures. Collectively, this work examined the phenomena behind the cryogenic microcracking of composite materials and applied this information to develop a predictive model for low temperature failure of composite materials from thermal stress generation.

Timmerman, John Francis

226

Fracture path in an anisotropic material in the light of a friction experiment  

NASA Astrophysics Data System (ADS)

A slider is pulled by means of a flexible link on a flat solid surface which exhibits anisotropic frictional properties. The resulting trajectory of the slider is assessed experimentally. First, we check that the experimental results are in excellent agreement with a theoretical description of the problem based on an expression of the frictional forces. Second, we point out that the trajectory of the slider can be recovered by the use of a “maximum of energy release rate” criterion which is generally used to predict the path of a fracture even if the validity of the principle is difficult to verify in the latter complex systems.

Chateau, D.; Géminard, J.-C.

2013-09-01

227

Fibrous composite materials in dentistry and orthopaedics: review and applications  

Microsoft Academic Search

In this report, the usage of fibrous composite materials in dentistry and orthopaedics is reviewed. Furthermore, the authors introduced functionally graded composite dental post, aesthetic composite archwires and brackets, and braided carbon\\/PEEK composite compression bone plate. Functionally graded composite dental post has continuously varied stiffness and this function successfully solved stress concentration at the root. Aesthetic composite archwires made of

K Fujihara; K Teo; R Gopal; P. L Loh; V. K Ganesh; S Ramakrishna; K. W. C Foong; C. L Chew

2004-01-01

228

Material selection and grade optimization applied to aluminum matrix composites  

Microsoft Academic Search

A general model for the optimal use of materials based on structural optimization is derived. The competitiveness of materials\\u000a is assessed with merit parameters. The competition between materials (material selection optimization) and the role of the composition and microstructure for a given material (grade optimization) are analyzed. The model is applied to aluminum matrix composites. The influence of matrix material,

J. Eliasson; R. Sandstroem

1995-01-01

229

A Grammatical Approach for Customization of Laminated Composite Materials  

Microsoft Academic Search

The wide range of properties covered by the manufacturable fiber—matrix combinations of composite materials, along with their directional property characteristics, provides designers with material selection flexibility during 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 intricate with the multiple loading conditions, which may

Soumitra Nandi; Zahed Siddique; M. Cengiz Altan

2011-01-01

230

Self-sensing structural composite materials  

NASA Astrophysics Data System (ADS)

Self-sensing was attained in lightweight structural composite materials, including those with polymer (epoxy), carbon and ceramic (Si3N 4) matrices. Either a volume of the composite or the interlaminar interface in the composite was used as the sensor. The use of the interlaminar interface as a sensor is a new approach, which was found to be effective in continuous carbon fiber epoxy-matrix composites for sensing temperature, moisture and damage. In case of temperature sensing, the interlaminar interface functioned as either a thermistor or a thermocouple junction. The thermocouple approach required the fibers in the contacting laminae to be dissimilar, whereas the thermistor approach did not. By using two crossply laminae, a two-dimensional array of sensors was attained and demonstrated to be effective for temperature distribution sensing. By measuring the contact electrical resistivity of the interlaminar interface during shear, the interlaminar shear process was monitored in real time. Study of the electrical conduction across the interlaminar interface led to the observation of apparent negative electrical resistance, which could be controlled by composite design. The use of a volume of a structural composite as the sensor and measurement of the volume electrical resistivity of the volume showed that continuous carbon fiber epoxy-matrix and carbon-matrix composites were effective for the self-sensing of strain and damage, whereas the SiC whisker Si3N 4-matrix composite was effective for the self-sensing of strain only. For the case of the epoxy-matrix composite, it was found that the four-probe method of resistance measurement was effective, whereas the two-probe method was not; it was also found that the though-thickness resistance was a sensitive indicator of matrix damage, while the longitudinal resistance was a less sensitive indicator. Polycrystalline beta-SiC fiber without a carbon core was found to be a piezoresistive strain sensor, but that with a carbon core was not. The consolidation of carbon fiber epoxy-matrix laminae during composite fabrication by lamination was monitored in real time by measurement of the through-thickness electrical resistivity. The consolidation was thus found to be hastened and to occur to a greater extent by increasing the pressure. The consequence of better consolidation remained after curing and subsequent cooling.

Wang, Shoukai

231

Using Optical Microscopy to Monitor Anisotropic Oxidation Growth in High-Temperature Polymer Matrix Composites  

Microsoft Academic Search

Durability and degradation mechanisms in composites are fundamentally influenced by the fiber, matrix, and interphase regions that constitute the composite domain. In this work, unidirectional G30-500\\/PMR-15 composite specimens are aged at elevated temperature in air resulting in oxidation propagation parallel and perpendicular to the fibers. The observed anisotropy in composite oxidation is explained by carefully monitoring the development and growth

G. P. Tandon; W. R. Ragland; G. A. Schoeppner

2009-01-01

232

Infrared synchrotron radiation from bending magnet and edge radiation sources for the study of orientation and conformation in anisotropic materials  

NASA Astrophysics Data System (ADS)

Over the last decade the use of synchrotron infrared microspectroscopy to spatially discriminate chemical and structural features in many different types of materials has grown considerably and has made significant impact in numerous research areas, in particular, in biological sciences and medicine. Although the brightness advantage of the synchrotron infrared (IR) source is well accepted as the key to high spatial discrimination, little attention has been given to measure the polarization properties of the synchrotron light at the sample stage in IR microscopy. In this work the intrinsic polarization of the IR source and its consequences for the study of anisotropic materials are discussed. The polarization characteristics of predominantly bending magnet radiation and predominantly edge radiation sources were measured at the microscope focus and compared. To illustrate the direct use of the intrinsic polarization of these sources in microscopy, the orientation and conformational details of a drawn polymer sample are considered.

Santoro, Gonzalo; Yousef, Ibraheem; Jamme, Frederic; Dumas, Paul; Ellis, Gary

2011-03-01

233

POLYMER ENGINEERING: Research on composite materials at Liverpool University, Part 2: Energy absorbing composite materials  

Microsoft Academic Search

The ability of a composite material to absorb energy in its bulk rather than at the tip of a crack is very important when such materials are used in the automobile industry, for example to protect passengers from the consequences of high speed impact under crash conditions. Part 2 of this article describes research into the design and fabrication of

D. Hull

1983-01-01

234

Self-assembly of segmented anisotropic particles: tuning compositional anisotropy to form vertical or horizontal arrays.  

PubMed

Columnar arrays of anisotropic nano- and microparticles, in which the long axes of the particles are oriented perpendicular to the substrate, are of interest for photovoltaics and other applications. Array assembly typically requires applied electric or magnetic fields and/or controlled drying, which are challenging over large areas. Here, we describe a scalable approach to self-assemble multicomponent nanowires into columnar arrays. Self-assembly of partially etched nanowires (PENs) occurred spontaneously during sedimentation from suspension, without drying or applied fields. PENs, which have segments that are either gold or "empty" (solvent-filled) surrounded by a silica shell, were produced from striped metal nanowires by first coating with silica and then removing sacrificial segments by acid etching. Electrostatic repulsion between the particles was necessary for array assembly; however, details of PEN surface chemistry were relatively unimportant. The aspect ratio and relative center of mass (COM) of the PENs were important for determining whether the PEN long axes were vertically or horizontally aligned with respect to the underlying substrate. Arrays with predominantly vertically aligned particles were achieved for PENs with a large offset in COM relative to the geometric center, while other types of PENs formed horizontal arrays. Assemblies were formed over >10 cm(2) areas, with over 60% of particles standing. We assessed array uniformity and reproducibility by imaging many positions within each sample and performing multiple assemblies of differently segmented PENs. This work demonstrates the versatility of gravity-driven PEN array assembly and provides a framework for designing other anisotropic particle systems that self-assemble into columnar arrays. PMID:23244212

Smith, Benjamin D; Kirby, David J; Rivera, Isamar Ortiz; Keating, Christine D

2012-12-20

235

Nondestructive evaluation of advanced ceramic composite materials  

SciTech Connect

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

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

1991-09-01

236

Data-driven imaging in anisotropic media  

SciTech Connect

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

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

2012-05-17

237

Data-driven imaging in anisotropic media  

NASA Astrophysics Data System (ADS)

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

Volker, Arno; Hunter, Alan

2012-05-01

238

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

239

Dental composites/glass ionomers: the materials.  

PubMed

Most commercial dental composites contain liquid dimethacrylate monomers (including BIS-GMA or variations of it) and silica-containing compositions as inorganic reinforcing filler particles coated with methacrylate-functional silane coupling agents to bond the resin to the filler. They also contain initiators, accelerators, photo-initiators, photosensitizers, polymerization inhibitors, and UV absorbers. Durability is a major problem with posterior composites. The typical life-span of posterior composites is from three to 10 years, with large fillings usually fewer than five years. Polymerization shrinkage and inadequate adhesion to cavity walls are remaining problems. Some pulp irritation can occur if deep restorations are not placed over a protective film. Some have advocated the use of glass-ionomer cement as a lining under resin composite restorations in dentin. The concept of glass-ionomer cements (GICs) was introduced to the dental profession in the early 1970's. Current GICs may contain poly(acrylic acid) or a copolymer. Higher-molecular-weight copolymers may also be used to improve the physical properties of some GICs. Stronger and less-brittle hybrid materials have been produced by the addition of water-soluble compatible polymers to form light-curing GIC formulations. The ion-leachable aluminosilicate glass powder, in an aqueous solution of a polymer or copolymer of acrylic acid, is attacked by the hydrated protons of the acid, causing the release of aluminum and calcium ions. Salt bridges are formed, and a gel matrix surrounds the unreacted glass particles. The matrix is adhesive to mineralized tissues. Provisions must be made for maintenance of the water balance of restorations for the first 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1292462

Bowen, R L; Marjenhoff, W A

1992-09-01

240

Architecture and properties of anisotropic polymer composite scaffolds for bone tissue engineering  

Microsoft Academic Search

Bone is a complex porous composite structure with specific characteristics such as viscoelasticity and anisotropy, both in morphology and mechanical properties. Bone defects are regularly filled with artificial tissue grafts, which should ideally have properties similar to those of natural bone. Open cell composite foams made of bioresorbable poly(l-lactic acid) (PLA) and ceramic fillers, hydroxyapatite (HA) or ?-tricalcium phosphate (?-TCP),

Laurence Marcelle Mathieu; Thomas L. Mueller; Pierre-Etienne Bourban; Dominique P. Pioletti; Ralph Müller; Jan-Anders E. Månson

2006-01-01

241

Orthotropic piezoelectric composite materials actuator and its preliminary application  

Microsoft Academic Search

In this paper, the laminated piezoelectric composite materials with orthotropic properties, the structures, performances of orthotropic piezoelectric actuation elements are studied. Orthotropic piezoelectric composite materials present remarkable differences in two primary directions perpendicular to each other. As actuation chips, the laminated orthotropic piezoelectric composite materials present opposite deformation tendencies in two primary directions, which conforms to the deformation law of

Ying Luo; Guoqi Zhao; Jianzu Gu; Zuting Liu

2002-01-01

242

Lignins as Components of Polymeric Composite Materials  

NASA Astrophysics Data System (ADS)

The results of studies of natural, native, and technical lignins are surveyed. Data are presented on the structures and physicochemical properties of various technical lignins (hydrolytic, sulphite, and sulphate lignins), which constitute the waste of the cellulose-paper and hydrolytic industries. Considerable attention is devoted to the examination of the properties of lignins which are responsible for their employment for the reinforcement of elastomers and the modification of plastics. The methods of utilisation and rational employment of technical lignins in the plastics industry as active ingredients of polymeric composite materials are examined. The importance of sulphate lignins as the most active from the standpoint of structure and properties in relation to the polymer matrix for the creation of highly filled lignin-containing polymeric materials — lignoplastics of the type of poprolin — is specially emphasised. The bibliography includes 160 references.

Lyubeshkina, E. G.

1983-07-01

243

Manufacturing of hard magnetic composite materials Nd-Fe-B  

Microsoft Academic Search

Purpose: This paper presents the material and technological solution which makes it possible obtaining of hard magnetic composite materials: nanocrystalline material - polymer. Design\\/methodology\\/approach: For fabrication of composite materials the Nd-Fe-B powder obtained by melt quenching technique was used and for matrix: epoxy resin (EP) or high density polyethylene (HDPE) (2.5 % wt.). Composite materials were compacted by the one-sided

M. Drak; B. Zi?bowicz; L. A. Dobrza?ski

244

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

SciTech Connect

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

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

2011-06-23

245

Hybrid nanocolloids with programmed three-dimensional shape and material composition  

NASA Astrophysics Data System (ADS)

Tuning the optical, electromagnetic and mechanical properties of a material requires simultaneous control over its composition and shape. This is particularly challenging for complex structures at the nanoscale because surface-energy minimization generally causes small structures to be highly symmetric. Here we combine low-temperature shadow deposition with nanoscale patterning to realize nanocolloids with anisotropic three-dimensional shapes, feature sizes down to 20?nm and a wide choice of materials. We demonstrate the versatility of the fabrication scheme by growing three-dimensional hybrid nanostructures that contain several functional materials with the lowest possible symmetry, and by fabricating hundreds of billions of plasmonic nanohelices, which we use as chiral metafluids with record circular dichroism and tunable chiroptical properties.

Mark, Andrew G.; Gibbs, John G.; Lee, Tung-Chun; Fischer, Peer

2013-09-01

246

Spectroscopic ellipsometry of anisotropic materials: application to the optical constants of HgI2.  

PubMed

A variable angle-of-incidence spectroscopic fixed-polarizer, rotating-polarizer, fixed-analyzer ellipsometer (PRPSE) across a spectral range from 300 to 800 nm is used to determine the optical properties of anisotropic uniaxial tetragonal red mercuric iodide (HgI(2)). For the first time, to our knowledge, the bulk crystal HgI(2) surface measured by ellipsometry was not subjected to potassium iodide cutting or etching. Measurements were made at an air-HgI(2) interface with the optic axis parallel to the sample surface. To determine the optical constants, we varied both the angle of incidence and the azimuth of the optic axis with the plane of incidence. The detailed formulas needed for reliable procedures for analyzing the data are presented. The ordinary and extraordinary complex indices of refraction, (n(o)--ik(o)) and (n(e)--ik(e)), respectively, are determined. Good agreement between PRPSE and the prism technique for the refractive index is observed. The surface aging effects of the ellipsometric parameters of HgI(2), during 30 h of exposure to air, were detected by PRPSE. PMID:18305658

En Naciri, A; Johann, L; Kleim, R; Sieskind, M; Amann, M

1999-02-01

247

Viscoelastic models for polymeric composite materials  

SciTech Connect

An improved model of the mechanical properties of the explosive contained in conventional munitions is needed to accurately simulate performance and accident scenarios in weapons storage facilities. A specific class of explosives can be idealized as a mixture of two components: energetic crystals randomly suspended in a polymeric matrix (binder). Strength characteristics of each component material are important in the macroscopic behavior of the composite (explosive). Of interest here is the determination of an appropriate constitutive law for a polyurethane binder material. A Taylor Cylinder impact test, and uniaxial stress tension and compression tests at various strain rates, have been performed on the polyurethane. Evident from time resolved Taylor Cylinder profiles, the material undergoes very large strains ({gt}100{percent}) and yet recovers its initial configuration. A viscoelastic constitutive law is proposed for the polyurethane and was implemented in the finite element, explicit, continuum mechanics code EPIC. The Taylor Cylinder impact experiment was simulated and the results compared with experiment. Modeling improvements are discussed. {copyright} {ital 1996 American Institute of Physics.}

Bardenhagen, S.G.; Harstad, E.N. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Foster, J.C. Jr. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)]|[Wright Laboratory, Armament Directorate, Eglin AFB, Florida 32542 (United States); Maudlin, P.J. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

1996-05-01

248

Composition of estuarine colloidal material: organic components  

NASA Astrophysics Data System (ADS)

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

Sigleo, Anne C.; Hoering, Thomas C.; Helz, George R.

1982-09-01

249

High velocity impact resistance of composite materials  

NASA Astrophysics Data System (ADS)

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

Justo, Jo; Marquer, A. T.

2003-09-01

250

Aluminium composite materials for multichip modules  

SciTech Connect

This paper reports that, as a result of continued advances in microelectronics, packaging technologies have become ital to the success of advanced designs. Progress in this field has been driven by advances in active device technologies that have resulted in significant miniaturization, increased functional density, and higher operating frequencies. These developments have produced ever-increasing power densities requiring improve thermal management schemes. In particular, multichip modules (MCMs) present challenges because they contain several devices in close proximity. The alternatives to improve cooling schemes-higher junction temperatures and decreased reliability-are clearly unacceptable. Requirements for improved cooling are complicated further in avionics systems by the need to minimize system weight and in automotive systems by the need to provide protection from a more hostile environment while maintaining low cost. These needs are driving materials developments along a number of fonts, as reviewed in Carl Zweben's article in this issue. Unfortunately, no current-generation material can meet all of these challenges. The use of aluminum or copper results in unacceptable expansion stress on silicon- or gallium arsenide-based devices. Kovar is costly to manufacture in complex configurations and ins inherently poor in thermal conductivity. The Cu/W and Cu/Mo blends, either in the form of metallurgical or macroscopic composites, offer good thermal conductivity but are inherently heavy and are manufactured from expensive raw materials.

Premkumar, M.K.; Hunt, W.H. Jr.; Sawtell, R.R. (Innometalx Group, Alcoa Center, PA (US))

1992-07-01

251

A heat spreading resistance model for anisotropic thermal conductivity materials in electronic packaging  

Microsoft Academic Search

The electronic package structure often comprises of materials that occur in thin layers. In many instances, these materials are lumped. Together as a simplified compact model to represent their thermal performance enabling parametric studies of the package structure. This new compact structure will have a new set of thermal properties that differs from its constituent components. Their combined material properties

T. M. Ying; K. C. Toh

2000-01-01

252

Ultrasonic guided wave mechanics for composite material structural health monitoring  

NASA Astrophysics Data System (ADS)

The ultrasonic guided wave based method is very promising for structural health monitoring of aging and modern aircraft. An understanding of wave mechanics becomes very critical for exploring the potential of this technology. However, the guided wave mechanics in complex structures, especially composite materials, are very challenging due to the nature of multi-layer, anisotropic, and viscoelastic behavior. The purpose of this thesis is to overcome the challenges and potentially take advantage of the complex wave mechanics for advanced sensor design and signal analysis. Guided wave mechanics is studied in three aspects, namely wave propagation, excitation, and damage sensing. A 16 layer quasi-isotropic composite with a [(0/45/90/-45)s]2 lay up sequence is used in our study. First, a hybrid semi-analytical finite element (SAFE) and global matrix method (GMM) is used to simulate guided wave propagation in composites. Fast and accurate simulation is achieved by using SAFE for dispersion curve generation and GMM for wave structure calculation. Secondly, the normal mode expansion (NME) technique is used for the first time to study the wave excitation characteristics in laminated composites. A clear and simple definition of wave excitability is put forward as a result of NME analysis. Source influence for guided wave excitation is plotted as amplitude on a frequency and phase velocity spectrum. This spectrum also provides a guideline for transducer design in guided wave excitation. The ultrasonic guided wave excitation characteristics in viscoelastic media are also studied for the first time using a modified normal mode expansion technique. Thirdly, a simple physically based feature is developed to estimate the guided wave sensitivity to damage in composites. Finally, a fuzzy logic decision program is developed to perform mode selection through a quantitative evaluation of the wave propagation, excitation and sensitivity features. Numerical simulation algorithms are validated with both finite element analyses and laboratory experiments. For the quasi-isotropic composite, it is found that the ultrasonic wave propagation characteristics are not always quasi-isotropic. The directional dependence is very significant at high frequency and higher order wave modes. Mode separation between Rayleigh-Lamb type and Shear Horizontal type guided waves is not possible. In addition, guided wave modes along one dispersion curve line could have a significant difference in wave structure. Therefore, instead of using traditional symmetric, antisymmetric, and SH notation, a new notation is used to identify the dispersion curves in a numerical order. Wave modes with a skew angle larger than 30 degrees can exist in a quasi-isotropic composite plate, which is validated by both FEM and experiment. At low frequency, the first wave mode has higher sensitivity than that of the third wave mode. However, the attenuation of the first wave mode is higher than that of the third wave mode. The mode selection trade-offs are evaluated and recommendations are provided for guided waves used in long range structural health monitoring.

Gao, Huidong

253

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.

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

2010-01-01

254

Anisotropic elastic waves with dissipation  

NASA Astrophysics Data System (ADS)

The formulation of the elastodynamics problem as a system of first-order partial differential equations has shown promise for improved analysis for anisotropic composite materials as reported previously and is quickly reviewed. Engineering criticism of acoustic decay modeling by viscoelastic for its complexity motivates a search for a simpler model for non-destructive measurement applications. An adjustment to the first order system that indicates a linear Maxwell type dissipation structure is easily included in the system. As is expected, providing for a Voigt or standard linear model is more difficult.

Roetman, E. L.

2012-05-01

255

Anisotropic Modeling of Shocked Single Crystals with Application to Energetic Materials  

NASA Astrophysics Data System (ADS)

A continuum, anisotropic modeling framework has been developed for simulating shock wave propagation in single crystals of arbitrary orientation. Our modeling approach incorporates nonlinear elasticity and crystal plasticity in a thermodynamically consistent tensor formulation. Crystal plasticity is described using a model that considers dislocation motion along specified slip planes. Shear cracking along specified crystal planes is also considered. Numerical simulations, using a finite-difference code, for large amplitude wave propagation in single crystals are presented. From these simulations, issues related to pure mode propagation for nonlinear elastic waves are discussed. Also, the effects of plasticity on wave propagation in single crystals are explored by comparing simulations to wave profile data for copper (Jones and Mote, 1969) and for LiF (Asay, et al., 1972). For copper, a single dislocation model for slip on 111 planes provides good agreement with quartz gauge data for shocks along the [100], [110], and [111] directions. For LiF, slip occurs on 110 planes, and good agreement with data is obtained for shocks along the [100] direction. Using the same dislocation model, simulated shock wave propagation along the low symmetry [310] direction of LiF is also examined. In addition, simulations are compared to transmitted wave profiles (Dick and Ritchie, 1994; Dick, 1997) for various orientations of shocked pentaerythritol tetranitrate (PETN) single crystals. For shocks along the insensitive [100] orientation of PETN, dislocation slip is unhindered and a dislocation dynamics model provides good fits to the wave profile data. For shocks along the sensitive [110] orientation, in which steric hindrance impedes the motion of dislocations, evidence of strain-softening behavior is observed and a shear cracking model fits the data well. Work supported by DOE and ONR.

Winey, J. M.

2005-07-01

256

Effective thermal conduction in composite materials  

NASA Astrophysics Data System (ADS)

The problem of determining the bounds and/or estimating the effective thermal conductivity ( ? eff) of a composite (multiphase) system given the volume fractions and the conductivities of the components has been investigated. A comparison between the measured data and the results predicted by theoretical models has been made for seven heterogeneous samples. The tested models include those of the effective medium theory (EMT), Hashin and Shtrikman (HS) bounds, and Wiener bounds. These models can be used to characterize macroscopic homogeneous and isotropic multiphase composite materials either by determining the bounds for the effective thermal conductivity and/or by estimating the overall conductivity of the random mixture. It turns out that the most suitable one of these models to estimate ? eff is the EMT model. This model is a mathematical model based on the homogeneity condition which satisfies the existence of a statistically homogeneous medium that encloses inclusions of different phases. Numerical values of thermal conductivity for the samples that satisfy the homogeneity condition imposed by the effective medium theory are in best agreement with the experimentally measured ones.

Suleiman, Bashir M.

2010-04-01

257

DBR PSi\\/PMMA composite materials for smart patch application  

Microsoft Academic Search

New nanostructured composite materials based on porous silicon (PSi) have been developed as a smart patch type for drug delivery applications. Distributed Bragg reflector (DBR) PSi films and caffeine-impregnated polymethyl methacrylate (PMMA) are used to produce flexible and stable composite materials in which the porous silicon matrix is covered with polymer. DBR PSi films and the composite films display a

Youngdae Koh; Seunghyun Jang; Jihoon Kim; Sungsoo Kim; Young Chun Ko; Sungdong Cho; Honglae Sohn

2008-01-01

258

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

259

Elastic wave propagation in anisotropic pipes in circumferential direction: An analytical study  

Microsoft Academic Search

Detection of stress corrosion cracks and other types of deterioration in pipes can be performed by producing elastic Lamb waves in the circumferential direction. Availability of Fiber Composite materials that have been utilized to retrofit the pipeline networks necessitates development of new theoretical procedures to analyze the behavior of anisotropic materials including Fiber Composites. The study of propagation of elastic

Saeed Towfighi

2001-01-01

260

A study on determining true stress–strain curve for anisotropic materials with rectangular tensile bars  

Microsoft Academic Search

Recently, a method has been proposed for determining material true stress–strain curve with rectangular tensile bars up to localized necking. In the proposed method, material true stress–strain curve can be directly calculated from the load versus thickness reduction (at the minimum cross-section) curve. The method was established based on the finite element (FE) analysis for isotropic materials. In this study,

Z. L. Zhang; J. Ødegård; O. P. Søvik; C. Thaulow

2001-01-01

261

Mechanics of composite materials - A unified micromechanical approach  

Microsoft Academic Search

This book presents a unified theory for the prediction of the overall behavior of composite materials. After discussing the fundamentals of the mechanics of composites, several basic composite models are described, together with the micromechanical method of cells for the analysis of elastic composites with aligned continuous or short fibers. The cell method is used to predict the strength and

Jacob Aboudi

1991-01-01

262

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

263

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

Microsoft Academic Search

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

Viktor A. Podolskiy; Leonid V. Alekseyev; Evgenii E. Narimanov

2005-01-01

264

Nanostructured Shape Memory Alloys: Adaptive Composite Materials and Components.  

National Technical Information Service (NTIS)

Methods for fabricating adaptive composite materials and components using shape memory alloy (SMA) constituents were investigated using a variety of fabrication techniques, including mechanical rolling methods. Both SMA- polymer and SMA-metal composites w...

A. B. Ellis J. H. Perepezko W. C. Crone

2007-01-01

265

Power Composites: Structural Materials that Generate and Store Electrical Energy.  

National Technical Information Service (NTIS)

We describe progress in the development of a synthetic multifunctional material: namely a fiber composite with both power and structural function. The structural composite contains batteries encased in piezoelectric tubes. When the structure vibrates the ...

D. A. Shockey S. C. Ventura S. C. Narang J. W. Simons B. C. Bourne

2005-01-01

266

Soviet Developments in Composite Materials, January - June 1975.  

National Technical Information Service (NTIS)

Selected Soviet publications on composite materials over a period of 6 months (January to June 1975) are abstracted in this report. The publications cover both experimental and theoretical research on carbon fiber-reinforced plastic composites and carbon ...

J. Kourilo

1976-01-01

267

Developing polymer composite materials: carbon nanotubes or graphene?  

PubMed

The formation of composite materials represents an efficient route to improve the performances of polymers and expand their application scopes. Due to the unique structure and remarkable mechanical, electrical, thermal, optical and catalytic properties, carbon nanotube and graphene have been mostly studied as a second phase to produce high performance polymer composites. Although carbon nanotube and graphene share some advantages in both structure and property, they are also different in many aspects including synthesis of composite material, control in composite structure and interaction with polymer molecule. The resulting composite materials are distinguished in property to meet different applications. This review article mainly describes the preparation, structure, property and application of the two families of composite materials with an emphasis on the difference between them. Some general and effective strategies are summarized for the development of polymer composite materials based on carbon nanotube and graphene. PMID:23813859

Sun, Xuemei; Sun, Hao; Li, Houpu; Peng, Huisheng

2013-07-01

268

Microrobotics using composite materials: the micromechanical flying insect thorax  

Microsoft Academic Search

The use of high performance composite materials provides a substantial performance improvement for microrobotics. Such materials have great beneflts over common MEMs materials such as better frac- ture toughness and fatigue properties than semicon- ductors, and higher stifiness to weight ratios than most metals. Composite structures yield remarkable improvements in microrobotic links and joints, as well as greater performance actuators

Robert J. Wood; Srinath Avadhanula; M. Menon; Ronald S. Fearing

2003-01-01

269

Using of Composite Material in Wind Turbine Blades  

Microsoft Academic Search

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

Bulent Eker; Aysegul Akdogan; Ali Vardar

2006-01-01

270

Nickel composite magnetostrictive material research for ultrasonic transducer  

Microsoft Academic Search

The immediate objective was to manufacture and test a composite transducer material of the compound SmFe2 in a nickel matrix fabricated by a powder metallurgy technique. The long term objective was the effective utilization of a 'giant' magnetostrictive REFe2 material in a ductile and corrosion resistant composite for use as a transducer core material.

D. T. Peters; E. L. Huston

1977-01-01

271

A class of theories of plasticity of anisotropic and pressure sensitive materials  

Microsoft Academic Search

Summary A class of theories of plasticity for orthotropic and pressure sensitive materials is described. The theories are based on quadratic yield criteria and hardening rules that are directly related to experimental stress-strain curves.

A. Maewal

1999-01-01

272

Anisotropic passage of high-energy protons through a quasicrystalline material  

SciTech Connect

Theoretical and experimental results of investigations of the passage of protons with energies in the 1-1000 MeV range through a quasicrystalline material have been presented. The quasicrystalline material consisted of specially oriented graphite crystallites measuring no more than 1000 {angstrom}. The computer experiment was based on recognized models of the passage of protons through matter and the Monte Carlo method. It took into account energy-loss processes and multiple scattering of the protons and microstructural features of the material. A quantitative dependence of the characteristics of the passage of protons on the microstructural parameters of the material and on the direction of propagation and energy of the protons has been discovered. In some cases, the mean range of protons in the material decreased to 80%, and the range straggling varied by more than two- to threefold at a constant density of the material {rho}{congruent}2.25 g/cm{sup 3}. The authenticity of the effect has been confirmed by experimental measurements. 10 refs., 8 figs.

Vagin, V.P.; Savichev, V.V. [N.E. Bauman Moscow State Technical Univ. (Russian Federation)

1995-01-01

273

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

274

Composite materials for extremely large mirrors and optical structures  

NASA Astrophysics Data System (ADS)

Building on our successful production of a world-class dimensionally stable composite optical bench structure for the SOLAR-B space telescope, Mitsubishi Electric is continuing to develop high performance lightweight composites for optical structures including mirrors. A key feature of composite materials is the ability to design the material to optimally meet the application requirements. Thus, various materials with individual characteristics are under development, each providing significant improvement over the state of the art.

Ozaki, Tsuyoshi; Hahn, Steven

2004-07-01

275

Orthotic Devices Using Lightweight Composite Materials.  

National Technical Information Service (NTIS)

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, a...

E. Harrison

1983-01-01

276

On the distinction between large deformation and large distortion for anisotropic materials  

SciTech Connect

A motion involves large distortion if the ratios of principal stretches differ significantly from unity. A motion involves large deformation if the deformation gradient tensor is significantly different from the identity. Unfortunately, rigid rotation fits the definition of large deformation, and models that claim to be valid for large deformation are often inadequate for large distortion. An exact solution for the stress in an idealized fiber-reinforced composite is used to show that conventional large deformation representations for transverse isotropy give errant results. Possible alternative approaches are discussed.

BRANNON,REBECCA M.

2000-02-24

277

Spectral and polarization effects in deterministically non-periodic multilayers containing optically anisotropic and gyrotropic materials  

Microsoft Academic Search

The influence of material anisotropy and gyrotropy on optical properties of fractal multilayer nanostructures is theoretically investigated. Gyrotropy is found to uniformly rotate the output polarization for bi-isotropic multilayers of arbitrary geometrical structure without any changes in transmission spectra. When introduced in a polarization splitter based on a birefringent fractal multilayer, isotropic gyrotropy is found to resonantly alter output polarizations

S. V. Zhukovsky; V. M. Galynsky

2006-01-01

278

Anisotropic, effective diffusivity of porous gas diffusion layer materials for PEFC  

Microsoft Academic Search

A comparative, experimental diffusivity study of gas diffusion layer (GDL) materials for polymer electrolyte fuel cells (PEFC) is presented for the first time. The GDL plays an important role for electrochemical losses due to gas transport limitations at high current densities. Characterization and optimization of these layers is therefore essential to improve power density. A recently developed method which allows

Reto Flückiger; Stefan A. Freunberger; Denis Kramer; Alexander Wokaun; Günther G. Scherer; Felix N. Büchi

2008-01-01

279

Nanostructured Composite Materials for High Temperature Thermoelectric Energy Conversion.  

National Technical Information Service (NTIS)

The goals of this project were to synthesize, characterize and model bulk nanostructured composite materials for thermoelectric energy conversion applications. The objective was to produce materials which demonstrate an increase in intrinsic thermoelectri...

C. J. O'Connor

2012-01-01

280

Preparation of Composite Materials in Space. Volume 2 Technical Report.  

National Technical Information Service (NTIS)

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 experiment...

W. H. Steurer S. Kaye

1973-01-01

281

HDPE Wood-Plastic Composite Material Model Subject to Damage.  

National Technical Information Service (NTIS)

The information presented in this thesis is part of an ongoing research project being performed at Washington State University to develop wood-plastic composite materials for waterfront structures. Material development has been finished and relevant infor...

G. Lu

2002-01-01

282

Statistically reconstructing continuous isotropic and anisotropic two-phase media while preserving macroscopic material properties  

NASA Astrophysics Data System (ADS)

We propose a method to generate statistically similar reconstructions of two-phase media. As with previous work, we initially characterize the microstructure of the material using two-point correlation functions (a subset of spatial correlation functions) and then generate numerical reconstructions using a simulated annealing method that preserves the geometric relationships of the material’s phase of interest. However, in contrast to earlier contributions that consider reconstructions composed of discrete arrays of pixels or voxels alone, we generate reconstructions based on assemblies of continuous, three-dimensional, interpenetrating objects. The result is a continuum description of the material microstructure (as opposed to a discretized or pixelated description), capable of efficiently representing large disparities in scale. Different reconstruction methods are considered based on distinct combinations of two-point correlation functions of varying degrees of complexity. The quality of the reconstruction methods are evaluated by comparing the total pore fraction, specific surface area of the percolating cluster, pore fraction of the percolating cluster, tortuosity, and permeability of the reconstructions to those of a set of reference assemblies. Elsewhere it has been proposed that two-phase media could be statistically reproduced with only two spatial correlation functions: the two-point probability function (the probability that two points lie within the same phase) and the lineal path function (the probability that a line between two points lies entirely within the same phase). We find that methods employing the two-point probability function and lineal path function are improved if the percolating cluster volume is also considered in the reconstruction. However, to reproduce more complicated geometric assemblies, we find it necessary to employ the two-point probability, two-point cluster, and lineal path function in addition to the percolating cluster volume to produce a generally accurate statistical reconstruction.

Davis, M. A.; Walsh, S. D. C.; Saar, M. O.

2011-02-01

283

Anisotropic thermal expansion in silicates: A density functional study of beta-eucryptite and related materials  

Microsoft Academic Search

Linear response density functional calculations of the structures, phonon spectra, and thermal expansion have been performed for the hexagonal silicate beta-eucryptite [beta-LiAlSiO4] and related materials, extending and refining earlier work using direct diagonalization of the dynamical matrix. The temperature (T) dependence of the lattice constants of beta-eucryptite agrees well with measurements, including the minimum in a(T) found at low T.

A. I. Lichtenstein; R. O. Jones; S. de Gironcoli; S. Baroni

2000-01-01

284

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

285

Composite tribological materials. (Latest citations from Fluidex). Published Search  

SciTech Connect

The bibliography contains citations concerning the properties, behavior, and uses of composite tribological materials in and on various objects, devices, and equipment. The citations examine friction and wear characteristics, mechanisms, and the performance of these materials and the objects to which they are applied. Composite tribological materials are used, for example, in bearings, gears, and piston rings. Included are self lubricating materials. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

NONE

1998-02-01

286

Environmental effects on composite materials. Volume 3  

SciTech Connect

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

Springer, G.S.

1988-01-01

287

Statistically reconstructing continuous isotropic and anisotropic two-phase media while preserving macroscopic material properties.  

PubMed

We propose a method to generate statistically similar reconstructions of two-phase media. As with previous work, we initially characterize the microstructure of the material using two-point correlation functions (a subset of spatial correlation functions) and then generate numerical reconstructions using a simulated annealing method that preserves the geometric relationships of the material's phase of interest. However, in contrast to earlier contributions that consider reconstructions composed of discrete arrays of pixels or voxels alone, we generate reconstructions based on assemblies of continuous, three-dimensional, interpenetrating objects. The result is a continuum description of the material microstructure (as opposed to a discretized or pixelated description), capable of efficiently representing large disparities in scale. Different reconstruction methods are considered based on distinct combinations of two-point correlation functions of varying degrees of complexity. The quality of the reconstruction methods are evaluated by comparing the total pore fraction, specific surface area of the percolating cluster, pore fraction of the percolating cluster, tortuosity, and permeability of the reconstructions to those of a set of reference assemblies. Elsewhere it has been proposed that two-phase media could be statistically reproduced with only two spatial correlation functions: the two-point probability function (the probability that two points lie within the same phase) and the lineal path function (the probability that a line between two points lies entirely within the same phase). We find that methods employing the two-point probability function and lineal path function are improved if the percolating cluster volume is also considered in the reconstruction. However, to reproduce more complicated geometric assemblies, we find it necessary to employ the two-point probability, two-point cluster, and lineal path function in addition to the percolating cluster volume to produce a generally accurate statistical reconstruction. PMID:21405929

Davis, M A; Walsh, S D C; Saar, M O

2011-02-28

288

High frequency probes of superconductivity and magnetism in anisotropic materials in very high magnetic field  

NASA Astrophysics Data System (ADS)

In this dissertation, I present a study of a wide range of organic and inorganic materials using radio frequency (rf) measurement methods. The organic samples under study were lambda-(BETS)2 GaCl4 and lambda-(BETS)2 FeCl4. In the lambda-(BETS)2 GaCl4, the H-T superconductivity phase diagram was studied using the tunnel diode oscillator (TDO) method and compared with simultaneous four terminals resistivity measurements. These simultaneous measurements show signs of para-conductivity in this material. The same method was used to study the lambda-(BETS)2 FeCl4 sample which is a field induced superconductor (FISC). The inorganic materials that I have studied include Ba 0.55K0.45Fe2 As2 and USb2. In Ba0.55K0.45Fe 2As2 (which belongs to the recently discovered Pnictide superconductors family), I have studied the H-T phase diagram for magnetic fields applied parallel and perpendicular to the crystallographic c-axis up to 65 tesla and in temperature as low as 4 K. Ba0.55K0.45 Fe2As2 was studied by a new rf technique that I have developed recently (PDO?Proximity Detector Oscillator). The rf measurements of Ba0.55 K0.45Fe2 As2 from my work support the prediction of an unconventional multigap superconductivity in this material. In the USb 2 sample, a Fermi surfaces measurement was performed by the TDO rf probe and by a torque magnetometer for comparison purposes in high magnetic fields up to 65 tesla and in temperatures above 0.5 K. I found that both the rf and the torque measurements reveal a cylindrical Fermi surface with approximately the same effective mass. However, the rf and the torque measurements reveal some differences in the frequencies obtained from the FFT obtained for each method. In this dissertation, most of the measurements were performed using rf probes like the TDO or the PDO. The PDO method has successfully replaced the TDO method to perform rf measurements in all different kinds of magnets (dc and pulsed).

Altarawneh, Moaz

289

Stress Concentration around a Small Circular Hole in the Himat Composite Plate.  

National Technical Information Service (NTIS)

Anisotropic plate theory is used to calculate the anisotropic stress concentration factors for a composite plate (AS/3501-5 graphite/epoxy composite, single ply or laminated) containing a circular hole. This composite material is used on the highly maneuv...

W. L. Ko

1985-01-01

290

Environmental effects on composite materials. Volume 3  

Microsoft Academic Search

The present collection of papers, each of which has previously been abstracted in International Aerospace Abstracts, discusses the accelerated environmental testing of composites, moisture solubility and diffusion in epoxy and epoxy-glass composites, the influence of internal and external factors affecting moisture absorption in polymer composites, long-tern moisture absorption in graphite\\/epoxy angle-ply laminates, the effect of UV light on Kevlar 49-reinforced

1988-01-01

291

Materials characterisation and crash modelling of composite-aluminium honeycomb sandwich material  

Microsoft Academic Search

Composite sandwich materials are extensively used in aerospace, motorsport and other applications that require low-weight, high-stiffness materials with high strength and energy absorption. In Formula 1 vehicles, composite-aluminium sandwich materials are used for the energy absorbing structures and the protective cell for the driver. Generally, the loading and failure mechanisms in sandwich composite materials are well understood. However, their behaviour

A. K. Pickett; A. J. Lamb; F. Chaudoye

2009-01-01

292

Methodology for Evaluating Manufacturability of Composite Materials  

NASA Astrophysics Data System (ADS)

It is widely acknowledged that decisions made in the early design stages have a greater influence on the final product than those made in the later stages. In a conventional design process, composite products are designed without sufficient consideration being given to limitations of composite manufacturing process. Quite often some of composite designs cannot be produced with special performance requirement or cannot be produced at a reasonable cost. To resolve this drawback and achieve the competitive designs for composite product, an integrated knowledge framework that supports the quantitative manufacturability evaluation of composite design proposals was introduced. The essential concept of the composite manufacturability was defined through an in-depth analysis of composite manufacturing process. The evaluation flow was acquired according to the hierarchical indices. A stage-based quality assessment model for the composite multistage process was mainly studies. It relies on the consideration that the final quality of a composite product is mainly determined by some critical stages during a production cycle. Finally, the method is illustrated through a case focusing on the quality issue of void formation in autoclave process.

Cong, Jingjie; Zhang, Boming

2012-06-01

293

Microstructural design of composite materials for crashworthy structural applications  

Microsoft Academic Search

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

S Ramakrishna

1997-01-01

294

Characterization and prediction of abrasive wear of powder composite materials  

Microsoft Academic Search

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

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

2009-01-01

295

CFRP\\/titanium hybrid material for improving composite bolted joints  

Microsoft Academic Search

The structural joining remains an essential challenge for the development of composite aerospace structures: every structural interconnection means a disturbance of an optimized structure resulting in an increase in overall structural weight. The lightweight potential of advanced, high-performance fiber composite materials is affected more strongly by mechanical fastening techniques than by conventional metallic materials due to the low shear and

B. Kolesnikov; L. Herbeck; A. Fink

2008-01-01

296

Biomedical applications of polymer-composite materials: a review  

Microsoft Academic Search

An overview of various biomedical applications of polymer-composite materials reported in the literature over the last 30 years is presented in this paper. For the benefit of the readers, general information regarding structure and function of tissues, types and purpose of implants\\/medical devices, and various other materials used, are also briefly presented. Different types of polymer composite that are already

S. Ramakrishna; J. Mayer; E. Wintermantel; Kam W Leong

2001-01-01

297

Thermophysical Analysis of High Modulus Composite Materials for Space Vehicles  

Microsoft Academic Search

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

Ho-Sung Lee

2009-01-01

298

Modeling for ultrasonic nondestructive evaluation or columnar structures in anisotropic materials. Progress report  

SciTech Connect

The levitation zone refiner facility has been upgraded with a new crystal pulley. This produces larger crystals with better control of the crystallographic orientation. Progress also has been made toward controlled bicrystal production. Ultrasonic measurements and calculations have been performed to determine elastic constants and study velocity and alternation along principal directions in single crystal Ni; study velocity, attenuation and mode conversion along nonprincipal directions in single crystal Ni; and measure attenuation through two crystals coupled together with different orientations. Finite element development of ultrasonic wave propagation has been extended into material having cubic symmetry. Mode conversion for waves along nonprincipal directions has been demonstrated and preliminary work has been done on the two-crystal problem. Progress has advanced our understanding on techniques for ultrasonic inspection of oriented structures such as weldments and castings.

Dewey, B.R.; Oliver, B.F.; Adler, L.

1981-12-15

299

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

PubMed

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

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

1991-01-01

300

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

Code of Federal Regulations, 2010 CFR

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

2009-04-01

301

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

Code of Federal Regulations, 2010 CFR

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

2010-04-01

302

Wear behaviour of aluminium matrix composite materials  

Microsoft Academic Search

Wear behaviour of aluminium matrix composites is characterized by the dry spindle wear test under various conditions (volume fractions of reinforcements, sliding distances and speeds). Wear resistance of composites is improved due to the presence of reinforcements, but no noticeable improvements are observed in the wear resistance with more than 20% addition of reinforcements. To analyse wear mechanisms, wear surfaces

C. S. Lee; Y. H. Kim; K. S. Han; T. Lim

1992-01-01

303

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.

Song, Jie; Saiz, Eduardo; Bertozzi, Carolyn R; Tomasia, Antoni P

2013-10-08

304

Automobile leaf springs from composite materials  

Microsoft Academic Search

The automobile industry has shown increased interest in the replacement of steel springs with fiberglass reinforced composite leaf springs. Therefore, the aim of this paper is to present a general study on the analysis, design and fabrication of composite springs. From this viewpoint, the suspension spring of a compact car, “a jeep” was selected as a prototype.A single leaf, variable

H. A. Al-Qureshi

2001-01-01

305

Tungsten filament as a reinforcing material for heat resistant composite materials  

Microsoft Academic Search

Translated from Metalloved. Term. Obrab. Metal.; 15: No. 7, 45-46(Jul ; 1973). Composite materials incorporating W wires in steel matrix were ; investigated. Data on wire and matrix composition are tabulated along with data ; on composite short-term strength. It is noted that the reinforcing filaments are ; weakened by recrystallization during prolonged use of the composite. (JRD);

F. P. Banas; A. B. Natapova; A. A. Shegai; Yu. V. Sukhanov

1973-01-01

306

New possibilities of composite materials application—Materials of specific magnetic properties  

Microsoft Academic Search

This paper presents the material and technological solution which makes it possible obtaining of soft and hard magnetic composite materials: nanocrystalline material–polymer. For fabrication of composite materials the following powders were used: soft magnetic material (Fe73.5Cu1Nb3Si13.5B9) and hard magnetic material (Nd14.8Fe76Co4.95B4.25). Polymer was used as the matrix (2.5wt.%). Advanced composite materials were compacted by the one-sided uniaxial pressing. The complex

L. A. Dobrza?ski; M. Drak; B. Zi?bowicz

2007-01-01

307

Effective magnetoelectric tensor of a composite material  

NASA Astrophysics Data System (ADS)

We calculate the effective magnetoelectric coefficient tensor of a composite of two single-phase magnetoelectrics in which effect of strain is unimportant. We obtain exact relations for elements of the effective magnetoelectric coefficient tensor entirely in terms of the elements of the individual components, and the composite geometry. The problem is solved by a decoupling transformation that reduces the problem to finding the effective coefficients in a composite of the same geometry but with two independent, curl-free fields. The decoupling transformation is found to be identical to that used in the problem of composite thermoelectrics footnotetextD. J. Bergman and O. Levy. Thermoelectric properties of a composite medium. J. Appl. Phys., 70:6821 - 6833, 1991. Details of the calculation will be presented.

Stroud, David; Dixit, Mehul

2013-03-01

308

Development of novel polymer\\/quasicrystal composite materials  

Microsoft Academic Search

We report on a new class of materials, polymer\\/quasicrystal composites with useful properties for beneficial exploitation in applications, such as dry bearings and composite gears. Our preliminary results indicate that our new composites are a means of enhancing the properties of certain organic polymers while providing a new means of processing quasicrystals. Al–Cu–Fe quasicrystalline materials significantly improved wear resistance to

Paul D Bloom; K. G Baikerikar; Joshua U Otaigbe; Valerie V Sheares

2000-01-01

309

Influence of material properties on the wear of composite coatings  

Microsoft Academic Search

Aluminium matrix composite (AlMC) materials are finding more and more applications in machine construction. The addition of reinforcing materials to the matrix significantly improves the composite wear resistance. However, the presence of particles of a very hard, ceramic phase (Al2O3 and SiC) increases the wear of the sliding counterpart operating against the composite. Therefore, there exists a need to find

Andrzej Posmyk

2003-01-01

310

Modeling of self-healing composite materials  

Microsoft Academic Search

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

Alexander Dementsov

2008-01-01

311

Carbon-Carbon Materials - Carbon Composites Materiaux Carbone-Carbone Composites Carbones.  

National Technical Information Service (NTIS)

The application of carbon based materials in solid propellant rocket engine nozzles is discussed. Considered are polycrystalline graphites, pyrographite, carbon reinforced phenolic composites, and carbon-carbon composites. The importance of sepcarb (carbo...

C. Choury

1977-01-01

312

Overview of bacterial cellulose composites: A multipurpose advanced material.  

PubMed

Bacterial cellulose (BC) has received substantial interest owing to its unique structural features and impressive physico-mechanical properties. BC has a variety of applications in biomedical fields, including use as biomaterial for artificial skin, artificial blood vessels, vascular grafts, scaffolds for tissue engineering, and wound dressing. However, pristine BC lacks certain properties, which limits its applications in various fields; therefore, synthesis of BC composites has been conducted to address these limitations. A variety of BC composite synthetic strategies have been developed based on the nature and relevant applications of the combined materials. BC composites are primarily synthesized through in situ addition of reinforcement materials to BC synthetic media or the ex situ penetration of such materials into BC microfibrils. Polymer blending and solution mixing are less frequently used synthetic approaches. BC composites have been synthesized using numerous materials ranging from organic polymers to inorganic nanoparticles. In medical fields, these composites are used for tissue regeneration, healing of deep wounds, enzyme immobilization, and synthesis of medical devices that could replace cardiovascular and other connective tissues. Various electrical products, including biosensors, biocatalysts, E-papers, display devices, electrical instruments, and optoelectronic devices, are prepared from BC composites with conductive materials. In this review, we compiled various synthetic approaches for BC composite synthesis, classes of BC composites, and applications of BC composites. This study will increase interest in BC composites and the development of new ideas in this field. PMID:24053844

Shah, Nasrullah; Ul-Islam, Mazhar; Khattak, Waleed Ahmad; Park, Joong Kon

2013-08-15

313

Modeling and simulation of manufacturing processes of advanced composite materials  

NASA Astrophysics Data System (ADS)

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

Lee, Woo I.; Springer, George S.

314

Wear resistance of composite materials. (Latest citations from Engineered Materials abstracts). Published Search  

SciTech Connect

The bibliography contains citations concerning wear resistance of composite materials. References discuss polymer, ceramic and metal composites. Tribological testing and failure analyses are included. (Contains a minimum of 200 citations and includes a subject term index and title list.)

Not Available

1994-09-01

315

Anisotropic AAA: computational comparison between four and two fiber family material models.  

PubMed

Abdominal aortic aneurysm (AAA) is a cardiovascular disease with high incidence among elderly population. Biomechanical computational analyses can provide fundamental insights into AAA pathogenesis and clinical management, but modeling should be sufficiently accurate. Several constitutive models of the AAA wall are present in the literature, and some of them seem to well describe the experimental behavior of the aneurysmatic human aorta. In this work we compare a two (2FF) and a four (4FF) fiber families constitutive models of the AAA wall. Both these models satisfactorily fit literature data from biaxial tests on the aneurysmatic tissue. To investigate the peculiar characteristics of these models, we considered the problem of AAA inflation, and solved it by implementing the constitutive equations in a finite element code. A 20% axial stretch was imposed to the aneurysm ends, to simulate the physiological condition. Although fitted on the same dataset, the two material models lead to considerably different outcomes. In particular, adopting a 4FF strain energy function (SEF), an increase of the circumferential stress values can be observed, while higher axial stresses are recorded for the 2FF model. These differences can be attributed to the intrinsic characteristics of the SEFs and to the effective stress field, with respect to the one experienced in biaxial experimental tests on which the fitting is based. In fact the two SEFs appear similar within the region of the stress-strain experimental data, but become different outside it, as in case of aneurysms, due to the effects of the data extrapolation process. It is suggested that experimental data should be obtained for conditions similar to those of the application for which they are intended. PMID:21767843

Di Achille, P; Celi, S; Di Puccio, F; Forte, P

2011-07-20

316

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

317

Reflection and transmission for layered composite materials  

NASA Astrophysics Data System (ADS)

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.

1991-03-01

318

Review of Recent Developments. Advanced Composite Materials.  

National Technical Information Service (NTIS)

Contents: Hybrid composites, Beryllium-wire reinforced alloys by roll bonding, Transverse strength of ductile-fiber-reinforced metals, Transverse strength of brittle-fiber-reinforced alloys, Transverse strength of Al2O3-filament reinforced nickel-chromium...

K. R. Hanby

1971-01-01

319

Photorefractivity in liquid crystalline composite materials.  

National Technical Information Service (NTIS)

We report recent improvements in the photorefractive of liquid crystalline thin film composites containing electron donor and acceptor molecules. The improvements primarily result from optimization of the exothermicity of the intermolecular charge transfe...

G. P. Wiederrecht M. R. Wasielewski

1997-01-01

320

Towards the Molecular Design of Composite Materials.  

National Technical Information Service (NTIS)

The objective of this project is to develop a theory of the statistical thermodynamics at polymer blends and block copolymer systems in which the theory relates microscopic and macroscopic properties and thereby assists in the molecular design of composit...

K. F. Freed

1994-01-01

321

Environmental Fatigue Tests with Composite Materials.  

National Technical Information Service (NTIS)

Since the certification of composite airframe structures requires consideration of the effects of in service environmental conditions on fatigue and residual strength, two environmental test rigs for eight specimens were developed. Different graphite/epox...

M. Berg D. Rott H. Huth

1991-01-01

322

Thermally Conductive Structural 2D Composite Materials.  

National Technical Information Service (NTIS)

Report developed under STTR contract for topic number AF10-BT01. The recent Small Business Technology Transition (STTR) program was focused on the thermal property enhancement of polymeric composites using various functionalizations and treatments of pitc...

D. B. Curliss J. E. Lincoln J. T. Brown

2012-01-01

323

Wear behaviour of aluminium matrix composite materials  

Microsoft Academic Search

Wear behaviour of aluminium matrix composites is characterized by the dry spindle wear test under various conditions (volume\\u000a fractions of reinforcements, sliding distances and speeds). Wear resistance of composites is improved due to the presence\\u000a of reinforcements, but no noticeable improvements are observed in the wear resistance with more than 20% addition of reinforcements.\\u000a To analyse wear mechanisms, wear surfaces

C. S. Lee; Y. H. Kim; K. S. Han; T. Lim

1992-01-01

324

Tunneling and nonuniversal conductivity in composite materials  

NASA Astrophysics Data System (ADS)

A simple model based on interparticle tunneling conduction and a percolative network is shown to imply a diverging distribution of high resistors in the system. This distribution is expected to yield a nonuniversal behavior of the electrical conductivity. An experimental study of carbon black-polymer composites seems to confirm this expectation, as well as explaining why a nonuniversal behavior has not been observed in previous experimental studies on such composites.

Balberg, I.

1987-09-01

325

Nondestructive inspection and evaluation of composite-material flywheels  

SciTech Connect

It has been demonstrated that flywheels made from composite materials are capable of storing energy with a significantly higher energy density than those made from conventional metals. Since composite materials are also very durable and inherently safer for such applications, it would appear that they will play a major role in flywheel energy-storage systems. This report addresses the question of how flywheels made from composite materials can be inspected with nondestructive test methods to establish their initial quality and their subsequent integrity during service. A variety of methods is discussed in the context of special requirements for the examination of composite flywheel structures and the results of several example nondestructive evaluations before and after spin testing are presented. Recommendations for general nondestructive testing and evaluation of composite-material flywheels are made.

Reifsnider, K.L.; Boyd, D.M.; Kulkarni, S.V.

1982-02-24

326

Angular spectrum approach for the computation of group and phase velocity surfaces of acoustic waves in anisotropic materials  

PubMed

The decomposition of an acoustic wave into its angular spectrum representation creates an effective base for the calculation of wave propagation effects in anisotropic media. In this method, the distribution of acoustic fields is calculated in arbitrary planes from the superposition of the planar components with proper phase shifts. These phase shifts depend on the ratio of the distance between the planes to the normal component of the phase slowness vector. In anisotropic media, the phase shifts depend additionally on the changes of the slowness with respect to the direction of the propagation vector and the polarization. Those relations are obtained from the Christoffel equation. The method employing the fast Fourier transformation algorithm is especially suited for volume imaging in anisotropic media, based on holographic detection in transmission of acoustic waves generated by a point source. This technique is compared with measurements on crystals performed by phase-sensitive scanning acoustic microscopy. PMID:10829665

Pluta; Schubert; Jahny; Grill

2000-03-01

327

Composite Materials Having Low Filler Percolation Thresholds and Methods of Controlling Filler Interconnectivity.  

National Technical Information Service (NTIS)

Composite materials are disclosed having low filler percolation thresholds for filler materials into the composite matrix material along with methods of controlling filler interconnectivity within the composite matrix material. Methods are, thus, disclose...

C. J. Capozzi R. Qu R. A. Gerhardt R. J. Samuels Z. Li

2006-01-01

328

Percolation and Tunneling in Composite Materials  

NASA Astrophysics Data System (ADS)

Classical percolation theory is concerned with the onset of geometrical connectivity and the accompanied onset of electrical connectivity in disordered systems. It was found, however, that in many systems, such as various composites, the geometrical and electrical onsets of the connectivity are not simultaneous and the correlation between them depends on physical processes such as tunneling. The difference between the above two types of systems and the consequences for the electrical transport properties of the latter composites have been largely ignored in the past. The application of scanning local probe microscopies and some recent theoretical developments have enabled a better understanding of the latter systems and their sometimes "strange" behavior as bona fide percolation systems. In this review we consider the above issues and their manifestation in three types of systems: Carbon Black-Polymer composites, metal-insulator cermets and hydrogenated microcrystalline silicon.

Balberg, I.; Azulay, D.; Toker, D.; Millo, O.

329

Material, process, and product design of thermoplastic composite materials  

Microsoft Academic Search

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

Heming Dai

2001-01-01

330

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

331

Nonmetallic materials and composites at low temperatures 3  

Microsoft Academic Search

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

G. Hartwig; D. Evans

1986-01-01

332

Characterization and performance of a self-healing composite material  

Microsoft Academic Search

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

Michael Richard Kessler

2002-01-01

333

Networks of channels for self-healing composite materials  

Microsoft Academic Search

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

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

2006-01-01

334

Left-handed materials in metallic magnetic granular composites  

Microsoft Academic Search

There is recently interests in the “left-handed” materials. In these materials the direction of the wave vector of electromagnetic radiation is opposite to the direction of the energy flow. We present simple arguments that suggests that magnetic composites can also be left-handed materials. However, the physics involved seems to be different from the original argument. In our argument, the imaginary

S. T. Chui; Z. F. Lin; L.-B. Hu

2003-01-01

335

Optical properties of polymer\\/chalcogenide glass composite materials  

Microsoft Academic Search

The novel composite material based on middle density polyethylene on one hand and thermoplastic chalcogenide glass on other hand has been worked out. Both materials used in the research are highly transparent in the middle and far IR but refraction indexes of components differ dramatically. The basic materials, polymer and glass, have close viscosities at the temperature of polyethylene processing.

Edward Bormashenko; Roman Pogreb; Semion Sutovski

2000-01-01

336

Composite materials with giant anisotropy and negative index of refraction  

Microsoft Academic Search

We demonstrate that a nanostructured plasmonic composite material can show negative index of refraction at infrared and optical frequencies. In contrast to conventional negative refraction materials, our design does not require periodicity and thus is highly tolerant to fabrication defects. Moreover, since the proposed material is intrinsically non-magnetic (mu ? 1), its performance is not limited to proximity of a

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

2005-01-01

337

Field-responsive smart composite particle suspension: materials and rheology  

NASA Astrophysics Data System (ADS)

Both electrorheological (ER) and magnetorheological (MR) fluids are known to be smart materials which can be rapidly and reversibly transformed from a fluid-like to a solid-like state within milliseconds by showing dramatic and tunable changes in their rheological properties under external electrical or magnetic field strength, respectively. Here, among various smart composite particles studied, recently developed core-shell structured polystyrene/graphene oxide composite based ER material as well as the dual-step functionally coated carbonyl iron composite based MR material are briefly reviewed along with their rheological characteristics under external fields.

Zhang, Wen Ling; Liu, Ying Dan; Choi, Hyoung Jin

2012-09-01

338

Understanding the anisotropic initiation sensitivity of shocked pentaerythritol tetranitrate single crystals  

NASA Astrophysics Data System (ADS)

Shock initiation experiments of single crystals of pentaerythritol tetranitrate (PETN) have revealed that they show anisotropic sensitivity to mechanical impact. An ignition and growth model is developed based on the empirical observations of these impact studies. Because this model is independent of the direction of compression, the anisotropic material response of single crystals has not been addressed. Here, we present a complete description of the anisotropic ignition and growth of PETN and provide quantitative validations using the experimental data. The model is appropriate for use in single crystal studies of explosive initiation, or in grain scale simulations of composites.

Kim, Ki-Hong; Fried, Laurence E.; Yoh, Jack J.

2013-09-01

339

Elemental composition of lunar surface material.  

PubMed

Elemental abundances, so far obtained, derived from the analysis of Apollo 11 lunar material are reported. Similarities and differences exist between lunar material, the eucritic achondrites, and the augite achondrite Angra dos Reis, the analysis of which is also reported. PMID:17781474

Smales, A A; Mapper, D; Webb, M S; Webster, R K; Wilson, J D

1970-01-30

340

Advanced AE Techniques in Composite Materials Research  

Microsoft Academic Search

Advanced, waveform based acoustic emission (AE) techniques have been successfully used to evaluate damage mechanisms in laboratory testing of composite coupons. An example is presented in which the initiation of transverse matrix cracking was monitored. In these tests, broad band, high fidelity acoustic sensors were used to detect signals which were then digitized and stored for analysis. Analysis techniques were

William H. Prosser

1996-01-01

341

Composite metal foil and ceramic fabric materials  

DOEpatents

The invention comprises new materials useful in a wide variety of terrestrial and space applications. In one aspect, the invention comprises a flexible cloth-like material comprising a layer of flexible woven ceramic fabric bonded with a layer of metallic foil. In another aspect, the invention includes a flexible fluid impermeable barrier comprising a flexible woven ceramic fabric layer having metal wire woven therein. A metallic foil layer is incontinuously welded to the woven metal wire. In yet another aspect, the invention includes a material comprising a layer of flexible woven ceramic fabric bonded with a layer of an organic polymer. In still another aspect, the invention includes a rigid fabric structure comprising a flexible woven ceramic fabric and a resinous support material which has been hardened as the direct result of exposure to ultraviolet light. Inventive methods for producing such material are also disclosed. 11 figs.

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

1992-03-24

342

Composite metal foil and ceramic fabric materials  

SciTech Connect

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

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

1992-01-01

343

Processing of magnesia pyrochlore composites for inert matrix materials  

NASA Astrophysics Data System (ADS)

Inert matrix (IM) materials for nuclear fuel in light water reactors must meet several critical requirements that include high temperature stability, good irradiation behaviour, high thermal conductivity, and hot water corrosion resistance. MgO possesses all of the necessary requirements for an ideal IM candidate, except hot water corrosion resistance. A composite approach is being investigated in order to improve the corrosion resistance of MgO, while simultaneously taking advantage of the high thermal conductivity of MgO and its ability to be reprocessed in nitric acid. MgO pyrochlore composite compositions are fabricated based on neutronic property simulations for assessment as potential IM materials. The selected pyrochlore compositions are synthesized by both sol gel and solid state processing, and how composite processing affects the microstructure will be discussed. Among the multiple composite processing approaches investigated, ball milling produces the most homogeneous and consistent microstructures.

Yates, S. J.; Xu, P.; Wang, J.; Tulenko, J. S.; Nino, J. C.

2007-05-01

344

Metal oxide composite dosimeter method and material  

DOEpatents

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

Miller, Steven D. (Richland, WA)

1998-01-01

345

Strength Criteria for Composite Materials (A Literature Survey).  

National Technical Information Service (NTIS)

Literature concerning strength (failure) criteria for composite materials is reviewed with emphasis on phenomenological failure criteria. These criteria are primarily intended to give a good estimation of the safety margin with respect to failure for arbi...

F. Roode

1982-01-01

346

Cone Calorimeter Evaluation of the Flammability of Composite Materials,  

National Technical Information Service (NTIS)

A study was undertaken to evaluate the fire performance of composite materials using the cone calorimeter as the bench-scale method of test simulating the thermal irradiance from fires of various magnitudes. Five parameters were derived from the calorimet...

J. E. Brown E. Braun W. H. Twilley

1988-01-01

347

Material Model Evaluation of a Composite Honeycomb Energy Absorber.  

National Technical Information Service (NTIS)

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 th...

E. L. Fasanella K. E. Jackson M. A. Polanco M. S. Annett

2012-01-01

348

Materials Aspects of Fiber-Reinforced Polymer Composites in Infrastructure.  

National Technical Information Service (NTIS)

This paper provides a review of the technical literature pertaining to materials aspects of fiber-reinforced polymer (FRP) composites in infrastructural and other civil engineering applications. The main focus is placed upon the durability, chemical and m...

J. W. Chin

1996-01-01

349

Durability of composite polymer materials working in contact with pulp  

NASA Astrophysics Data System (ADS)

Composite materials were modified in order to increase their wear resistance when in contact with raw-cotton. It is found that the friction pairs increases their efficiency and durability to 2.0-2.2 times.

Abed-Negmatova, N. S.; Gulyamov, G.; Negmatov, S. S.; Hodzhikariev, D. M.; Negmatov, J. N.; Eminov, Sh. Sh.; Bozorbaev, Sh.; Aripova, A.; Negmatova, M. I.

2012-07-01

350

Smoke Production And Thermal Decomposition Products From Advanced Composite Materials.  

National Technical Information Service (NTIS)

This report describes the smoke production and thermal decomposition products from the combustion of Advanced Composite Materials (ACM) used on high performance aircraft. There are three distinct project phases with only Phase I described here. The prelim...

D. L. Courson C. D. Flemming K. J. Kuhlmann J. W. Lane J. H. Grabau

1996-01-01

351

Application of Eddy Current Techniques to Graphite Composite Materials.  

National Technical Information Service (NTIS)

Eddy current methods have been extensively applied in metals. The common characteristic for these applications is the high electrical conductivity of materials tested, higher than 1 pct. IACS (titanium). With the increasing use of graphite composite mater...

M. Alvaro V. Cortes

1991-01-01

352

Investigation of the Role of the Interface in Composite Materials.  

National Technical Information Service (NTIS)

The role of the interface in composite materials has been investigated to determine the nature of bonding between matrix and dispersed constituents and the manner in which these bonds across the interface actually give rise to the resultant properties of ...

M. H. Richman R. D. French

1968-01-01

353

Core Programs of High-Performance Composite Materials.  

National Technical Information Service (NTIS)

Evaluation of composites and components continued from the previous contract. Materials used to RTM carbon-carbon preforms were evaluated. RDS data analysis software was written and modulated DSC evaluated as an analysis tool. Bridge rehabilitation succes...

A. Crasto D. Anderson R. Esterline K. Han C. Hill

1998-01-01

354

Photorefractivity in liquid crystalline composite materials  

SciTech Connect

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

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

1997-09-01

355

A tensile impact test apparatus for composite materials  

Microsoft Academic Search

A tensile impact test apparatus capable of applying a pure axial tensile loading to even a highly orthotropic composite material, e.g., a unidirectionally reinforced composite, was designed and constructed. Existing impact test methods such as Charpy, Izod and plate impact induce very complex stress states, making the interpretation of results difficult. Details of the apparatus design, and instrumentation problems which

D. F. Adams; L. G. Adams

1989-01-01

356

Iatrogenic tooth abrasion comparisons among composite materials and finishing techniques  

Microsoft Academic Search

Statement of Problem. Many different rotary instruments are available for shaping composite restorations. Whether use of these instruments causes undesirable iatrogenic abrasion of either the tooth surface or the composite restorative material is unknown. Assuming that damage occurs, which technique is least damaging is unknown. Purpose. This in vitro study quantified the loss of surface enamel and dentin surrounding Class

Christina A. Mitchell; Maria R. Pintado; William H. Douglas

2002-01-01

357

Chemical composition of material fractions in Danish household waste  

Microsoft Academic Search

The chemical composition of Danish household waste was determined by two approaches: a direct method where the chemical composition (61 substances) of 48 material fractions was determined after hand sorting of about 20tonnes of waste collected from 2200 households; and an indirect method where batches of 80–1200tonnes of unsorted household waste was incinerated and the content of the waste determined

Christian Riber; Claus Petersen; Thomas H. Christensen

2009-01-01

358

Embedded fibre Bragg grating sensors in advanced composite materials  

Microsoft Academic Search

Fibre Bragg grating (FBG) sensors have been embedded in a number of advanced composite materials and fibre\\/metal laminates (FMLs). The post-fabrication FBG spectra were studied to examine the influence of manufacturing variables (such as composite stacking sequence and resin flow during processing) on the final profile of the spectrum and the functionality of the FBG sensor. Distortion and broadening of

K. S. C. Kuang; R. Kenny; M. P. Whelan; W. J. Cantwell; P. R. Chalker

2001-01-01

359

Polymer?Nanoparticle Composites: Preparative Methods and Electronically Active Materials  

Microsoft Academic Search

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

P. K. Sudeep; Todd Emrick

2007-01-01

360

Introduction to Composite Materials for Engineers and Technicians  

NSDL National Science Digital Library

This learning module will help instructors explain composite materials specifically for engineers and technicians. Students will learn the structure and advantages of composite materials as well as the basic processing procedures involved in their creation. It will serve as a one-lecture introduction and would be appropriate for students at the high school or college level. This document will serve as a framework for instructors and may be downloaded in PDF format.

Stuart, William J.

2012-11-08

361

Measurement of Poisson's ratio of dental composite restorative materials  

Microsoft Academic Search

The aim of this study was to determine the Poisson ratio of resin-based dental composites using a static tensile test method. Materials used in this investigation were from the same manufacturer (3M ESPE) and included microfill (A110), minifill (Z100 and Filtek Z250), polyacid-modified (F2000), and flowable (Filtek Flowable [FF]) composites. The Poisson ratio of the materials were determined after 1

Sew Meng Chung; Adrian U Jin Yap; Wee Kiat Koh; Kuo Tsing Tsai; Chwee Teck Lim

2004-01-01

362

Glass-Containing Composite Materials. Alternative Reinforcement Concepts  

Microsoft Academic Search

Glass-containing composites with interpenetrating, graded or layered microstructures as well as hybrid glass and glass-ceramic\\u000a matrix composites are discussed. Aspects of their fabrication, microstructural characterisation, properties and applications\\u000a are reviewed. These materials have advantages regarding ease of processing and\\/or special properties which can be achieved,\\u000a in comparison with conventional dispersion-reinforced and fibre-reinforced glasses and glass-ceramics. The use of these materials

Aldo R. Boccaccini

363

Electrolytic cut-off grinding machine for composite materials  

Microsoft Academic Search

A new cut-off machine for a composite material has been developed. The machine uses a combined system of grinding and electrolysis and it can cut off a fragile composite material consisting of metal and non-metal components. Its fundamental performance is examined on low-carbon steel and cast iron. The machine can reduce the cutting force and roughness of a finished surface

Masahiko Yoshino; Takahiro Shirakashi; Toshiyuki Obikawa; Eiji Usui

1998-01-01

364

Electromagnetic properties of dielectric and magnetic composite material for antenna  

Microsoft Academic Search

Electromagnetic properties of dielectric and magnetic composite materials were studied with various weight fractions and particle\\u000a sizes of ferrite. The composite materials were prepared through Ni-Zn spinel ferrite and silicon elastomer, and were characterized\\u000a with regard to permittivity, permeability, loss tangente, and loss tangentu. Those properties of Ni-Zn spinel ferrite were approximately 7.0, 8.4, 0.01 and 0.1 MHz to 150

Sang-Hoon Park; Won-Ki Ahn; Jun-Sig Kum; Jeong-Keun Ji; Ki-Ho Kim; Won-Mo Seong

2009-01-01

365

Hydrogen storage properties of magnesium based nanostructured composite materials  

Microsoft Academic Search

In this work, nanostructured composite materials Mg–Ni, Mg–Ni–La, Mg–Ni–Ce and Mg–LaNi5 have been synthesized using the mechanical alloying process. The new materials produced have been investigated by X-ray diffraction (XRD), transition electron microscope (TEM), scanning electron microscope (SEM) and electron energy dispersion spectrum (EDS) for their phase compositions, crystal structure, grain size, particle morphology and the distribution of catalyst element.

Ming Au

2005-01-01

366

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

367

Fast, Contactless Monitoring of the Chemical Composition of Raw Materials  

NASA Astrophysics Data System (ADS)

A technique to monitor chemical composition of materials during manufacturing of ceramic products, in particular - of bricks, is investigated. The technique of monitoring is likely to offset environmental pollution and save energy. For this purpose, we use the Surface photo charge effect, which is generated for each solid body interacting with electromagnetic field. The measurement is express and can be performed in-situ in production conditions. The experimental work has shown that different samples of the investigated materials with different compositions produce different signals specific to each sample. For the same material, the signal varies with the change in chemical composition. More specifically, it is shown that for the material from which the bricks are fired, the signal is a function of the percentage of coal sludge. The results indicate that the characterization technique as a viable technique for control of incoming raw materials.

Ivanov, O.; Stoyanov, Zh.; Stoyanov, B.; Nadoliisky, M.; Vaseashta, Ashok

368

Composite material stub-blade wing joint  

NASA Astrophysics Data System (ADS)

The viability of a composite stub-blade wing joint for high-altitude long-endurance aircraft was investigated in a joint-design study. The results of an analysis show that the resulting joint design is capable of carrying moderately high bending, shear, and torsional loads. The stub-blade wing joint design is weight-competitive with the traditional tension-type wing joint. In addition, it offers attractive features such as the ease of assembly and disassembly, the ease of fabrication, and an aerodynamic smoothness.

Franklin, Walter M.; Kreimendahl, Bryan W.

369

Quality control materials in food composition databanks  

Microsoft Academic Search

Reference materials (RMs) have emerged with the aim of improving analytical methods performance, in what regards to their validation, calibration, uncertainty, training and internal quality control, and of increasing the comparability of measurements between laboratories. Due to their unquestionable importance, but still low availability and high cost, the present work has determined the suitability of infant formula, powdered garlic, tea

I. Castanheira; C. Abrantes; M. Batista; I. Coelho; A. Sanches-Silva

2009-01-01

370

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

371

Personal care compositions comprising a zinc containing material in an aqueous surfactant composition  

US Patent & Trademark Office Database

Disclosed are compositions comprising an effective amount of a zinc containing material having an aqueous solubility within the composition of less than about 25% by weight at 25.degree. C.; from about 5% to about 50% of a surfactant; and from about 40% to about 95% water; wherein the pH of the composition is greater than about 7. Further disclosed are compositions comprising an effective amount of a zinc containing material having an aqueous solubility within the composition of less than about 25% by weight at 25.degree. C.; from about 5% to about 50% of a surfactant; and from about 0.1% to about 5% of a zinc ionophoric material; from about 40% to about 95% water; and wherein the pH of the composition is greater than about 7.

2012-02-21

372

Olivine Composite Cathode Materials for Improved Lithium Ion Battery Performance  

SciTech Connect

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

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

2006-01-01

373

Accelerated hygrothermal stabilization of composite materials  

SciTech Connect

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

Gale, J.A.

1994-05-01

374

Data analysis techniques for impact tests of composite materials  

Microsoft Academic Search

This paper discusses data analysis techniques for instrumented impact tests conducted on glass fiber composite materials. For this study, a drop weight tower has been instrumented with an accelerometer and computer data acquisition system. From the acceleration data obtained, load, energy, velocity, and displacement are calculated in a spreadsheet environment. The resulting data from multiple tests for each material type

A. L. Svenson; M. W. Hargrave; B. S. Ye; L. C. Bank

1994-01-01

375

Impact damage processes in composite sheet and sandwich honeycomb materials  

Microsoft Academic Search

The research interest of this study is the impact toughness of different lightweight sandwich panels and composite sheet materials. This is as to the degrees of damage inflicted on the contact surface, through-thickness and rear surface of the materials when subjected to different impacts. For this study, specimens were prepared from sheet moulding compound (SMC), glass mat thermoplastic (GMT) and

J. P. Dear; H. Lee; S. A. Brown

2005-01-01

376

Measurement of Damping of Composite Materials for Turbomachinery Applications.  

National Technical Information Service (NTIS)

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 qua...

D. L. Harris

1998-01-01

377

Experimental techniques for dynamic characterization of composite materials  

SciTech Connect

This research combines theoretical and experimental approaches for dynamic material characterization of composite materials. The samples studied include continuous fiber graphite/epoxy beams with various symmetric lay-up configurations. Included are laminated beams with the following lay-ups: [0[sub 8]/90[sub 8

Greif, R. (Tufts Univ., Medford, MA (United States). Dept. of Mechanical Engineering); Hebert, B. (Cambridge Collaborative, Inc., MA (United States))

1995-01-01

378

Polymer-based composite materials in general industrial fields  

Microsoft Academic Search

An overview of material research and product development for polymer-based composite materials since the 1950s in Japanese general industrial use is given. This progress is divided into four steps, each lasting about one decade; the trends of the fourth period (1984-today), following the third, transition period, are emphasised. In addition, as a future perspective, the possibility of development of intelligent

Tatsuo Ogasa; Jun Takahashi; Kiyoshi Kemmochi

1995-01-01

379

DOE Automotive Composite Materials Research: Present and Future Efforts  

Microsoft Academic Search

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

1999-01-01

380

Effective mechanical, transport and cross properties for distressed composite materials  

Microsoft Academic Search

Composite materials and materials that have been subjected to varying level of damage have been the subject of extensive research for several decades especially with regard to prediction of constitutive behavior. Classical homogenization techniques aim at replacing an actual heterogeneous body by a fictitious homogeneous solid, which globally behaves in the same way. In this thesis, we are considering the

Morteza Eskandari-Ghadi

2003-01-01

381

Thermographic investigation of sandwich structure made of composite material  

Microsoft Academic Search

In this paper an experimental procedure, by means of thermographic technique, was set up in order to detect some typical defects, which could be found in composite material sandwich structures. The material thermal response was investigated for different artificially defects inserted in some specimens; every kind of defect was listed. Then the experimental procedure was applied to study a wind-turbine

V. Dattoma; R. Marcuccio; C. Pappalettere; G. M. Smith

2001-01-01

382

A Novel Non-Halogenated Flame Retardant for Composite Materials  

Microsoft Academic Search

Flame retardants, such as inorganic fillers or halogenated resins, are incorporated into composites either as additives or reactive materials. In order to improve processability and mechanical properties, as well as reduce smoke toxicity, a method is being developed to introduce highly effective, inexpen- sive flame retardant materials into thermoset resins. Superabsorbent polymers (SAP) can be loaded with inexpensive inorganic phosphates

Martin Rogers; Lisa Sterner; Thomas Amos; Ayesha Johnson

383

Anisotropic enhanced backscattering induced by anisotropic diffusion.  

PubMed

The enhanced backscattering cone displaying a strong anisotropy from a material with anisotropic diffusion is reported. The constructive interference of the wave is preserved in the helicity preserving polarization channel and completely lost in the nonpreserving one. The internal reflectivity at the interface modifies the width of the backscatter cone. The reflectivity coefficient is measured by angular-resolved transmission. This interface property is found to be isotropic, simplifying the backscatter cone analysis. The material used is a macroporous semiconductor, gallium phosphide, in which pores are etched in a disordered position but with a preferential direction. PMID:15524650

Bret, B P J; Lagendijk, A

2004-09-03

384

Collagen/hydroxyapatite composite materials with desired ceramic properties.  

PubMed

Our purpose was to obtain and characterize some collagen/hydroxyapatite (COLL/HA) hybrid composite materials with desired ceramic properties. The ceramic properties of these materials were achieved by combining two drying methods: controlled air drying at 30°C followed by freeze-drying. Through the function of the air drying times, the materials morphology varies from porous materials (when the materials are freeze-dried) up to dense materials (when the materials are air-dried), while the combined drying allows us to obtain an intermediary morphology. The composite materials intended to be used as bone grafts and in a drug delivery system were characterized by XRD, FTIR, SEM, and also by determining the ceramic properties by using the Arthur method. The ceramic properties of these COLL/HA composite materials vary in large range, for instance the density of the materials varies from 0.06 up to 1.5 g/cm(3) while the porosity varies from 96.5% down to 27.5%. PMID:21415027

Andronescu, Ecaterina; Voicu, Georgeta; Ficai, Maria; Mohora, Ioana Anita; Trusca, Roxana; Ficai, Anton

2011-03-16

385

Method of forming a composite material having improved bond strength  

SciTech Connect

A composite material having improved bond strength and a substantially smooth external surface comprises a deoxidized copper alloy core material and a copper-aluminum-silicon clad material. The composite is formed by rolling together the core and clad, preferably in an unheated condition, in a single pass with a reduction of about 50% to 75% to form a metallurgical bond between the core and clad and thereafter enhancing the bond strength by heating the bonded core and cladding to a temperature in the range of about 200/sup 0/ C. to about 750/sup 0/ C. for a time period of about 5 minutes to about 24 hours.

Breedis, J.F.; Fister, J.C.

1985-02-19

386

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

387

Global Material Characterization of Composite Structures Using Lamb Wave Stmr Array Technique  

NASA Astrophysics Data System (ADS)

Structural health monitoring of plate like structures, using transducer arrays located suitably on the structure, finds applications in monitoring aerospace structures. These plates are anisotropic, with wave propagation properties varying with direction. Single Transmitter Multiple Receiver (STMR) arrays have been shown before to have the ability to locally characterize the stiffness properties of a composite material with anisotropy. The STMR arrays have also been demonstrated for SHM applications using phase reconstruction techniques. The guided ultrasonic Lamb waves are used where the central piezoelectric wafer-active sensor (PWAS) emits the guided waves, and the other PWAS sensors receive the Lamb wave signals. In the current work, this technique has been extended to the determination of global elastic moduli using the Lamb wave S0 and A0 mode signals that are reflected from features in the structure such as edge of the plate, bolt holes, etc. that are known apriori using STMR array and then reconstruct the unknown defects present on the structure using the same sensor array. The reconstruction of elastic moduli is accomplished using a Genetic Algorithm (GA) based inversion algorithm that optimizes an objective function for a particular configuration of the STMR array and the elastic moduli of the component. The solution to this inversion is the global elastic moduli of the composite which is then used to determine the unknown defects in the test component. Simulations were carried out using S0 and A0 mode velocity data for composite layups such as unidirectional, cross-ply, and quasi-isotropic graphite-epoxy composite layups. The inversion algorithm was tested using the simulated edge reflector data and found to agree well with the expected values. Experimental validation has been performed on 3.15 mm quasi-isotropic graphite-epoxy composite.

Vepakomma, Rajesh; Janapati, Vishu Vardhan; Balasubramaniam, Krishnan; Krishnamurthy, C. V.

2010-02-01

388

Bioactive ceramic composite materials in hydroxyapatite-tricalcium phosphate system  

Microsoft Academic Search

Materials in hydroxyapatite-tricalcium phosphate systems are promising for the use in cell technologies for regeneration of\\u000a damaged bone tissue. The results of investigations of the influence of the synthesis conditions on the phase composition of\\u000a materials and the formation of their structure and properties upon baking of powders are given. The parameters of the process\\u000a of preparation of materials with

O. L. Kubarev; V. S. Komlev; S. M. Barinov

2010-01-01

389

The Yeh-Stratton Criterion for Composite Materials  

Microsoft Academic Search

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

Hsien-Yang Yeh; Chang H. Kim

1994-01-01

390

Modern composite materials manufa- ctured by pressure infiltration method  

Microsoft Academic Search

Purpose: The purpose of this paper is to present the technique of manufacturing the composite materials based on porous ceramic preforms infiltrated by liquid aluminium alloy and examination of the structure and corrosion resistance of those materials. Design\\/methodology\\/approach: The material for investigations was manufactured by pressure infiltration method of ceramic porous preforms. The eutectic aluminium alloy EN AC - AlSi12

L. A. Dobrza?ski; M. Kremzer; M. Drak

391

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

392

Linear geometrical magnetoresistance effect: Influence of geometry and material composition  

NASA Astrophysics Data System (ADS)

This work reports theorems on geometrical magnetoresistance effects in simply or multiply connected surfaces. We consider planar or three-dimensional device geometries, and assume that the current/voltage relations are linear. It is shown that the resistance of any two-wire device must be an even function of the magnetic field. We further calculate the magnitude of the highest and lowest second-order geometrical magnetoresistance of a planar two-wire device, for given isotropic material parameters. The largest change in magnetoresistance occurs when the boundaries of the device contain only electrically conducting leads and no insulating components. When the Fermi surface and the mobility tensor are isotropic, as is the case for n-type InAs and InSb, the magnetoresistance obtained in the Corbino geometry is the largest possible, but this conclusion does not generalize to materials with anisotropic conductivity tensors. The presence of multiple ellipsoidal carrier pockets in Bi also explains why the geometrical magnetoresistance effects are much smaller in the trigonal plane of Bi than in InAs, even though these materials have similar mobilities at room temperature, and the conductivity of Bi is isotropic in that plane.

Baker, Daniel R.; Heremans, Joseph P.

1999-06-01

393

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

394

Materials characterization center workshop on compositional and microstructural analysis of nuclear waste materials. Summary report  

Microsoft Academic Search

The purpose of the Workshop on Compositional and Microstructural Analysis of Nuclear Waste Materials, conducted November 11 and 12, 1980, was to critically examine and evaluate the various methods currently used to study non-radioactive, simulated, nuclear waste-form performance. Workshop participants recognized that most of the Materials Characterization Center (MCC) test data for inclusion in the Nuclear Waste Materials Handbook will

J. L. Daniel; D. M. Strachan; J. W. Shade; M. T. Thomas

1981-01-01

395

Thermal, mechanical, and electroelastic behavior of composite materials  

SciTech Connect

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

Dunn, M.L.

1992-01-01

396

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

397

Annual Conference on Composites and Advanced Ceramic Materials  

SciTech Connect

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

Not Available

1991-10-01

398

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

399

The Cost of Automotive Polymer Composites: A Review and Assessment of DOE's Lightweight Materials Composites Research  

SciTech Connect

Polymer composite materials have been a part of the automotive industry for several decades, with early application in the 1953 Corvette. These materials have been used for applications with low production volumes, because of their shortened lead times and lower investment costs relative to conventional steel fabrication. Important drivers of the growth of polymer composites have been the reduced weight and parts consolidation opportunities the material offers, as well as design flexibility, corrosion resistance, material anisotropy, and mechanical properties. Although these benefits are well recognized by the industry, polymer composite use has been dampened by high material costs, slow production rates, and to a lesser extent, concerns about recyclability. Also impeding large scale automotive applications is a curious mixture of concerns about material issues such as crash energy absorption, recycling challenges, competitive and cost pressures, the industry's general lack of experience and comfort with the material, and industry concerns about its own capabilities (Flynn and Belzowski 1995). Polymer composite materials are generally made of two or more material components--fibers, either glass or carbon, reinforced in the matrix of thermoset or thermoplastic polymer materials. The glass-reinforced thermoset composites are the most commonly used composite in automotive applications today, but thermoplastic composites and carbon fiber-reinforced thermosets also hold potential. It has been estimated that significant use of glass-reinforced polymers as structural components could yield a 20-35% reduction in vehicle weight. More importantly, the use of carbon fiber-reinforced materials could yield a 40-65% reduction in weight.

Das, S.

2001-01-26

400

Fabrication of a nanostructured gold-polymer composite material  

NASA Astrophysics Data System (ADS)

A facile synthesis route is described for the preparation of a poly-(o-aminophenol)-gold nanoparticle composite material by polymerization of o-aminophenol (AP) monomer using HAuCl4 as the oxidant. The synthesis was carried out in a methanol medium so that it could serve a dual solvent role, a solvent for both the AP and the water solution of HAuCl4. It was found that oxidative polymerization of AP leads to the formation of poly-AP with a diameter of 50±10nm, while the reduction of AuCl4- results in the formation of gold nanoparticles (˜ 2nm). The gold nanoparticles were uniformly dispersed and highly stabilized throughout the macromolecular chain that formed a uniform metal-polymer composite material. The resultant composite material was characterized by means of different techniques, such as UV-vis, IR and Raman spectroscopy, which offered the information about the chemical structure of polymer, whereas electron microscopy images provided information regarding the morphology of the composite material and the distribution of the metal particles in the composite material.

Mallick, K.; Witcomb, M.; Scurrell, M.

2006-07-01

401

Probabilistic fatigue life prediction of metallic and composite materials  

NASA Astrophysics Data System (ADS)

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

Xiang, Yibing

402

Optimization of internal damping in fiber reinforced composite materials  

SciTech Connect

This dissertation describes new, reliable, and fast impulse techniques for characterization of damping in fiber reinforced composite materials. Flexural and extensional vibration tests are used for determination of complex moduli of aligned discontinuous fiber composite, and off axis fiber composite specimens, respectively. The results from these tests are then compared with theoretical predictions from micromechanics models based on a single fiber. The analytical model is fitted to the experimental results by varying certain parameters that have uncertainties associated with them. It is shown that improved damping can be obtained with very low fiber aspect ratios, and that even better damping properties are possible with off-axis fibers. These results were obtained from tests done on three different fiber reinforced composite materials: graphite/epoxy, Kevlar/epoxy and boron/epoxy.

Suarez, S.A.

1985-01-01

403

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

404

Material selection and grade optimization applied to aluminum matrix composites  

SciTech Connect

A general model for the optimal use of materials based on structural optimization is derived. The competitiveness of materials is assessed with merit parameters. The competition between materials (material selection optimization) and the role of the composition and microstructure for a given material (grade optimization) are analyzed. The model is applied to aluminum matrix composites. The influence of matrix material, amount of reinforcement, and value of weight savings is studied. Mechanical properties are analyzed with the aid of published experimental data and available models. The Tsai-Halpin model is used to represent the variation of the elastic modulus with the amount of reinforcement. For yield strength the modified shear lag model is applied. It can satisfactorily describe experimental data and the variation with reinforcement for high-strength matrix alloys. For aluminum alloys of medium and lower strength, the observed increase is larger than the predicted one. This can be explained by the help of more recently developed micromechanical models that take into account the changes in microstructure in the matrix. For structural parts, large values of weight savings are usually necessary to make the particulate-reinforced composites competitive with carbon steel or their parent aluminum alloys. In other applications, combinations of properties are important to make the composites competitive.

Eliasson, J.; Sandstroem, R. [Royal Inst. of Tech., Stockholm (Sweden). Materials Science and Engineering

1995-06-01

405

Material selection and grade optimization applied to aluminum matrix composites  

NASA Astrophysics Data System (ADS)

A general model for the optimal use of materials based on structural optimization is derived. The competitiveness of materials is assessed with merit parameters. The competition between materials ( material selection optimization) and the role of the composition and microstructure for a given material ( grade optimization) are analyzed. The model is applied to aluminum matrix composites. The influence of matrix material, amount of reinforcement, and value of weight savings is studied. Mechanical properties are analyzed with the aid of published experimental data and available models. The Tsai-Halpin model is used to represent the variation of the elastic modulus with the amount of reinforcement. For yield strength the modified shear lag model is applied. It can satisfactorily describe experimental data and the variation with reinforcement for high-strength matrix alloys. For aluminum alloys of medium and lower strength, the observed increase is larger than the predicted one. This can be explained with the help of more recently developed micromechanical models that take into account the changes in microstructure in the matrix. For structural parts, large values of weight savings are usually necessary to make the particulate-reinforced composites competitive with carbon steel or their parent aluminum alloys. In other applications, combinations of properties are important to make the composites competitive.

Eliasson, J.; Sandström, R.

1995-06-01

406

Grained composite materials prepared by combustion synthesis under mechanical pressure  

DOEpatents

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

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

1990-01-01

407

High-specific-energy composite-material flywheel. Final report  

SciTech Connect

A flywheel rotor has been designed and fabricated to demonstrate energy densities ranging from 50.6 watt-hour/kg (23 watt-hour/lb) to 88 watt-hour/kg (40 watt-hour/lb). The design is composed of a multiring rim made of S-2 glass/epoxy and Kevlar/epoxy composite materials, mounted on a four-spoke aluminum and graphite/epoxy composite hub. Ten flywheel rotors were produced for test.

Not Available

1983-03-29

408

Radiopacity of experimental composite resins containing radiopaque materials.  

PubMed

This study aimed to investigate the relationship between the radiopacity of an experimental light-cured composite resin and the amount and type of its radiopaque material: Ti, SrCO3, ZrO2, BaSO4, or Bi2O3. Radiopacity of each material was evaluated in terms of aluminum equivalent thickness using an aluminum step wedge. Then, the half-value layer thickness of the experimental composite resin, which had an aluminium equivalent thickness of 1 mm, was evaluated. It was found that the effects of elemental composition were not identical when evaluated in terms of aluminum equivalent thickness and by half-value layer. Nevertheless, both measurement methods indicated that radiopacity increased with increase in radiopaque material content as well as increase in atomic number of the element. PMID:16279720

Aoyagi, Yujin; Takahashi, Hidekazu; Iwasaki, Naohiko; Honda, Ei-ichi; Kurabayashi, Toru

2005-09-01

409

A physically-based abrasive wear model for composite materials  

SciTech Connect

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

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

2001-05-01

410

Hot extruded carbon nanotube reinforced aluminum matrix composite materials.  

PubMed

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

Kwon, Hansang; Leparoux, Marc

2012-09-26

411

Hot extruded carbon nanotube reinforced aluminum matrix composite materials  

NASA Astrophysics Data System (ADS)

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

Kwon, Hansang; Leparoux, Marc

2012-10-01

412

Thermally mediated multiferroic composites for the magnetoelectric materials  

NASA Astrophysics Data System (ADS)

A magnetoelectric (ME) composite through thermal mediation is presented, which is different from the traditional strain/stress mediated ME composites. The ME laminate uses the large magnetocaloric effect, that is, a temperature change induced in the ferromagnetic Gd crystal by a magnetic field, and a large pyroelectric response in the relaxor ferroelectric polymer. Consequently, a simple laminate composite can produce a ME response ~0.5 V/(cm Oe). The ME coefficient was further enhanced to ~0.9 V/(cm Oe) by exploiting the magnetic flux concentration effect. The approach opens up an avenue in developing ME materials for broad range of applications.

Lu, S. G.; Fang, Z.; Furman, E.; Wang, Y.; Zhang, Q. M.; Mudryk, Y.; Gschneidner, K. A.; Pecharsky, V. K.; Nan, C. W.

2010-03-01

413

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 relative low thermal conductivity. The results indicate that, below some threshold thickness, the composite 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. [Arizona State Univ., Tempe, AZ (United States). Dept. of Mechanical and Aerospace Engineering; Niemann, R.C. [Argonne National Lab., IL (United States). Energy Technology Div.

1997-10-01

414

A thermodynamical constitutive model for shape memory materials. Part II. The SMA composite material  

Microsoft Academic Search

The phenomenological SMA equations developed in Part I are used in this second paper to derive the free energy and dissipation of a SMA composite material. The derivation consists of solving a boundary value problem formulated over a mesoscale representative volume element, followed by an averaging procedure to obtain the macroscopic composite constitutive equations. Explicit equations are derived for the

James G. Boyd; Dimitris C. Lagoudas

1996-01-01

415

Nondestructive inspection and evaluation of composite-material flywheels  

SciTech Connect

Several composite panels and flywheel designs were evaluated in support of the Mechanical Energy Storage Technology (MEST) project. Conventional nondestructive evaluation (NDE) technology was used on the panels and flywheels. All flywheels and panels were radiographed and, where practical, were also inspected using ultrasonic techniques. The results provided information about the structural features of flywheels and materials. This information is useful for the quality control of fabrication procedures. The detection of apparent flaws in fabrication cannot be related to the ultimate strength until failure mechanisms in composite materials have been fully defined. Therefore, the location of detected flaws should be recorded for later comparison with dynamic and destructive evaluations.

Boyd, D.M.; Maxfield, B.W.; Kulkarni, S.V.; Schwarber, A.J.

1982-02-24

416

Self-healing bentonite sheet material composite drainage structure  

SciTech Connect

A composite drainage structure capable of directing water longitudinally away from a potential area of water flow and incapable of transverse water penetration is described comprising: drainage means for receiving water and channeling the water to a predetermined area; channel means disposed between the first and second sheet materials of the drainage means for channeling water longitudinal within the drainage means to the predetermined area; and a cohesive layer of a water-swellable clay composition secured to the water-impermeable layer of sheet material.

Harriett, T.D.

1988-03-29

417

NDE of composite materials using ultrasonic oblique insonification  

SciTech Connect

The analysis of reflected ultrasonic waves induced by oblique insonification of composite materials is increasingly recognized as a powerful tool in providing information about defects and material properties. The theoretical modeling of the wave behavior for tone-burst and pulses has been very successful in accurately corroborating the experimental results. The data repeatability and accuracy make oblique insonification methods easy to standardize for practical applications. Recent theoretical and experimental results and the progress in using frequency- and time-domain data are discussed with an emphasis on the application to graphite/epoxy composites.

Bar-Cohen, Y. (California Inst. of Tech., Pasadena, CA (United States). Jet Propulsion Lab.); Mal, A.K.; Lih, Shyh-Shiuh (Univ. of California, Los Angeles, CA (United States). Mechanical, Aerospace, and Nuclear Engineering Dept.)

1993-11-01

418

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

419

Anisotropic branes  

NASA Astrophysics Data System (ADS)

We present a class of anisotropic brane configurations which shows BKL oscillations near their cosmological singularities. Near horizon limits of these solutions represent Kasner space embedded in AdS background. Dynamical probe branes in these geometries inherit anisotropies from the background. Amusingly, for a probe M5 brane, we find that there exists a parameter region where three of its world-volume directions expand while the rest contract.

Banerjee, Souvik; Bhowmick, Samrat; Mukherji, Sudipta

2013-10-01

420

Silicon carbide composites as fusion power reactor structural materials  

NASA Astrophysics Data System (ADS)

Silicon carbide was first proposed as a low activation fusion reactor material in the mid 1970s. However, serious development of this material did not begin until the early 1990s, driven by the emergence of composite materials that provided enhanced toughness and an implied ability to use these typically brittle materials in engineering application. In the decades that followed, SiC composite system was successfully transformed from a poorly performing curiosity into a radiation stable material of sufficient maturity to be considered for near term nuclear and non-nuclear systems. In this paper the recent progress in the understanding and of basic phenomenon related to the use of SiC and SiC composite in fusion applications will be presented. This work includes both fundamental radiation effects in SiC and engineering issues such as joining and general materials properties. Additionally, this paper will briefly discuss the technological gaps remaining for the practical application of this material system in fusion power devices such as DEMO and beyond.

Snead, L. L.; Nozawa, T.; Ferraris, M.; Katoh, Y.; Shinavski, R.; Sawan, M.

2011-10-01

421

Influence of magnetic materials on the transport properties of superconducting composite conductors  

NASA Astrophysics Data System (ADS)

Magnetic materials can help to improve the performance of practical superconductors on the macro/microscale as magnetic diverters and also on the nanoscale as effective pinning centres. It has been established by numerical modelling that magnetic shielding of the filaments reduces ac losses in self-field conditions due to decoupling of the filaments and, at the same time, it increases the critical current of the composite. This effect is especially beneficial for coated conductors, in which the anisotropic properties of the superconductor are amplified by the conductor architecture. However, ferromagnetic coatings are often chemically incompatible with YBa2Cu3O7 and (Pb,Bi)2Sr2Ca2Cu3O9 conductors, and buffer layers have to be used. In contrast, in MgB2 conductors an iron matrix may remain in direct contact with the superconducting core. The application of superconducting-magnetic heterostructures requires consideration of the thermal and electromagnetic stability of the superconducting materials used. On the one hand, magnetic components reduce the critical current gradient across the individual filaments but, on the other hand, they often reduce the thermal conductivity between the superconducting core and the cryogen, which may cause the destruction of the conductor in the event of thermal instability. A possible nanoscale method of improving the critical current density of superconducting conductors is the introduction of sub-micron magnetic pinning centres. However, the volumetric density and chemical compatibility of magnetic inclusions has to be controlled to avoid suppression of the superconducting properties.

Glowacki, B. A.; Majoros, M.; Campbell, A. M.; Hopkins, S. C.; Rutter, N. A.; Kozlowski, G.; Peterson, T. L.

2009-03-01

422

Contact acoustic nonlinearity phenomenon caused by the acoustic wave propagating in the composite material  

Microsoft Academic Search

Due to the massive applications of multilayered composite materials (for example carbon fiber material, glass fiber material etc.) in material industry, aviation industry, medical enterprise and other consumer industries, it becomes an important work to carry on the non-destructive evaluation to the long-term characteristic and the security of the composite materials in use. The reliability of a composite material is

Jian-jun Chen; De Zhang; Yi-wei Mao

2008-01-01

423

A polymethacrylate-silica composite material for dental implants.  

PubMed

A study has been carried out on the structure and surface texture of a new dental implant material composed of silica microspheres (3 or 5 wt%) and poly(methyl methacrylate). A recently developed composite material composed of vitreous carbon microballoons and poly(methyl methacrylate) has proven highly successful in clinical use, but the black color presents aesthetic problems at the gingival margin. The new material was developed in order to reproduce the many desirable qualities of the vitreous carbon-polymethacrylate composite, while omitting the black color. Square wafers (10 mm X 10 mm X1 mm) were studied, with the surface sandblasted in half of the specimens. Light microscopy revealed an even spacing of spherical configurations throughout the material. Scanning electron microscope studies revealed a finely porous surface with many large craters in the sandblasted specimens. PMID:201644

Hodosh, M; Shklar, G

1977-11-01

424

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

Microsoft Academic Search

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

Xianxian Wu

2002-01-01

425

Composite materials of nichrome with molybdenum and with tungsten  

Microsoft Academic Search

1.Hot isothermal pressing of nickel-chromium composites reinforced with refractory filaments makes it possible to regulate the parameters of the process and ensures obtaining a dense material with a given distribution of filament and high volume percentage of the filament.In combination with subsequent rolling, this method makes it possible to manufacture dense materials strengthened with grids.2.A white nonetching zone is formed

F. P. Banas; V. V. Gaiduk; B. S. Natapov; B. V. Aleksandrov; L. N. Efimenko

1971-01-01

426

Application of silcomp composite materials to turbine systems  

Microsoft Academic Search

A Si\\/SiC family of high temperature composite materials is being developed which, in some respects, resembles the related reaction bonded SiC materials in terms of its corrosion resistance, temperature limits, etc., but differs in the ability to tailor its mechanical properties over a fairly wide range. Two iterations of prototype turbine combustor components have been designed and fabricated from it

Hillig

1978-01-01

427

Alternative processing methods for tungsten-base composite materials  

SciTech Connect

Tungsten composite materials contain large amounts of tungsten distributed in a continuous matrix phase. Current commercial materials include the tungsten-nickel-iron with cobalt replacing some or all of the iron, and also tungsten-copper materials. Typically, these are fabricated by liquid-phase sintering of blended powders. Liquid-phase sintering offers the advantages of low processing costs, established technology, and generally attractive mechanical properties. However, liquid-phase sintering is restricted to a very limited number of matrix alloying elements and a limited range of tungsten and alloying compositions. In the past few years, there has been interest in a wider range of matrix materials that offer the potential for superior composite properties. These must be processed by solid-state processes and at sufficiently low temperatures to avoid undesired reactions between the tungsten and the matrix phase. These processes, in order of decreasing process temperature requirements, include hot-isostatic pressing (HIPing), hot extrusion, and dynamic compaction. The HIPing and hot extrusion processes have also been used to improve mechanical properties of conventional liquid-phase-sintered materials. Results of laboratory-scale investigations of solid-state consolidation of a variety of matrix materials, including titanium, hafnium, nickel aluminide, and steels are reviewed. The potential advantages and disadvantages of each of the possible alternative consolidation processes are identified. Postconsolidation processing to control microstructure and macrostructure is discussed, including novel methods of controlling microstructure alignment.

Ohriner, E.K.; Sikka, V.K.

1995-12-31

428

Airborne ultrasonic inspection in carbon/carbon composite materials  

NASA Astrophysics Data System (ADS)

In this work, a carbon/carbon (C/C) composite material was nondestructively characterized with non-contact ultrasonic methods using automated acquisition scanner as well as contact ultrasonic measurement because (C/C) composite materials have obvious high price over conventional materials. Because of permeation of coupling medium such as water, it is desirable to perform contact-less nondestructive evaluation to assess material properties and part homogeneity. Also through transmission mode was performed because of the main limitation for air-coupled transducers, which is the acoustic impedance mismatch between most materials and air. Especially ultrasonic images and velocities for C/C composite disk brake was measured and found to be consistent to some degree with the non-contact and contact ultrasonic measurement methods. Low frequency through-transmission scans based on both amplitude and time-of-flight of the ultrasonic pulse were used for mapping out the material property inhomogeneity. Measured results were compared with those obtained by the motorized system with using dry-coupling ultrasonics and through transmission method in immersion. Finally, results using a proposed peak-delay measurement method well corresponded to ultrasonic velocities of the pulse overlap method.

Yang, In-Young; Kim, Young-Hun; Park, Je-Woong; Hsu, David K.; Song, Song-Jin; Cho, Hyun-Jun; Kim, Sun-Kyu; Im, Kwang-Hee

2007-10-01

429

Temperature Effect on Stress Concentration around Circular Hole in a Composite Material Specimen Representative of X-29A Forward-Swept Wing Aircraft.  

National Technical Information Service (NTIS)

The theory of anisotropic elasticity was used to evaluate the anisotropic stress concentration factors of a composite laminated plate containing a small circular hole. This advanced composite was used to manufacture the X-29A forward-swept wing. It was fo...

H. Yeh

1988-01-01

430

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

431

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

SciTech Connect

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

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

1993-01-01

432

Ptah-socar fuel-cooled composite materials structure  

NASA Astrophysics Data System (ADS)

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

Bouchez, M.; Beyer, S.

2009-09-01

433

Intermetallic and titanium matrix composite materials for hypersonic applications  

Microsoft Academic Search

As part of the French Program of Research and Technology for Advanced Hypersonic Propulsion (PREPHA) which was launched in 1992 between Aerospatiale, Dassault Aviation, ONERA, SNECMA and SEP, an important work is specially devoted to the development of titanium and intermetallic composite materials for large airframe structures. At Dassault Aviation, starting from a long experience in Superplastic Forming - Diffusion

B. Berton; G. Surdon; C. Colin

1995-01-01

434

Vibrations of Stiffened Composite Panels With Smart Materials  

Microsoft Academic Search

The feasibility of using electrorheological (ER) fluids and self-sensing piezoelectric (PZT) actua- tors to control structural vibrations of stiffened composite panels subjected to wide-band random inputs is investigated. A collocated velocity feedback control mechanism is integrated using piezoelectric materials as sensors and actuators. Control of structural dynamic characteristics is introduced by elec- trorheological fluids located in the stiffeners. The transfer

Kevin C. Poulin; Rimas Vaicaitis

2004-01-01

435

Polymeric composite photorefractive materials for nonlinear optical applications  

NASA Astrophysics Data System (ADS)

Polymeric composite materials constitute a new and very promising class of photorefractive materials. In the design of polymeric photorefractive materials we use multicomponent composites in which necessary functionalities can be independently optimized. The investigated composites consisted of charge transporting polymeric matrix, and optically second-order active molecules. Two different photosensitizers were used to vary the wavelength response. Photorefractive properties of these materials were investigated using erasable volume holography in a non-degenerate four-wave mixing geometry and two-beam coupling techniques. A previously developed model of space-charge field grating formation in photoconductive polymers was used to explain the field dependence of four-wave mixing diffraction efficiency. The model takes into account the field dependence of charge photogeneration quantum yield, carrier field mobility, and electro-optic coefficient. Necessary information about these parameters was obtained from the results of photoconductivity and electro-optic modulation experiments. Special attention was focused on the kinetics of photorefractive response in the composite for optical signal processing and optical storage. It was found that a very effective switching of diffraction efficiency induced by dc electric field occurs in this system. Also, the results of kinetic studies of the index grating writing and its subsequent light-induced erasure, as well as a demonstration of the holographic image recording and retrieval, are reported.

Prasad, Paras N.; Orczyk, Maciek E.; Zieba, Jaroslaw W.; Burzynski, Ryszard; Zhang, Yue; Ghosal, Saswati; Casstevens, Martin K.

1994-05-01

436

Method and Apparatus for Gripping Uniaxial Fibrous Composite Materials.  

National Technical Information Service (NTIS)

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. Sufficien...

J. D. Whittenberger F. I. Hurwitz

1982-01-01

437

Ultrasonic inspection of impact induced damage in polymeric composite materials  

Microsoft Academic Search

An account is given of current performance capabilities in the ultrasonic inspection of graphite-epoxy composite materials of both simple laminate and sandwich type. Attention is given to damage types ranging from barely-visible impact effects to complete destruction. These ultrasonic inspection procedures have been implemented in the case of certification tests for the EH 101 helicopter.

R. Pezzoni; L. Merletti; G. Battagin; R. Denis

1992-01-01

438

Thermophysical properties of epoxy composite materials at low temperatures  

Microsoft Academic Search

The thermal conductivity, thermal diffusivity and specific heat of epoxy composite materials were investigated from 5 to 400 K. Experimental results of thermal expansion measurements in the temperature range 77–380 K are also presented. The spectrum of relaxation transitions is obtained by two independent methods; calorimetric and dilatometric.

I. E. Evseeva; S. A. Tanaeva

1995-01-01

439

Adsorbent new materials and composites produced in a single step  

Microsoft Academic Search

The aim of this work is the production and preliminary characterization of adsorbent new materials useful for sensor development. A new plasma chamber was simulated and designed in order to obtain multiple layers and\\/or composites in a single step. Plasma deposited organic fluorocompound and hexamethyldisilazane (HMDS) thin films were produced and tested as adsorbent layers. Chemical characterization used ellipsometry, Raman,

R. R. Lima; R. A. M. Carvalho; A. T. Carvalho; E. W. Simões; M. L. P. da Silva

2009-01-01

440

Study of the Nature of Fracture Failure in Composite Materials.  

National Technical Information Service (NTIS)

The boron, aluminum composite material samples were cut to shape and subjected to push-pull type of loading under Instron Servo Hydrolic test system to failure. The failure surfaces were examined under electron microscope. The data collected under about t...

R. N. Rao

1986-01-01

441

Damage evolution monitoring in unidirectional graphite\\/epoxy composite materials  

Microsoft Academic Search

Possible solutions to the difficulties associated with life prediction efforts in unidirectional graphite\\/epoxy composite laminates are suggested. Specimens were fatigue cycled at five different load levels to characterize the fatigue behavior as well as the scatter in the data for this material system. Based on S-N data for this system, the mean life of samples at each load level could

A. Razvan; M. Elahi; K. L. Reifsnider; C. Gaylord

1991-01-01

442

Multiscale Damage Modeling for Composite Materials: Theory and Computational Framework  

Microsoft Academic Search

A nonlocal multiscale continuum damage model is developed for brittle composite materials. A triple-scale asymptotic analysis is generalized to account for the damage phenomena occur- ring at micro-, meso- and macro- scales. A closed form expressions relating microscopic, mesoscopic and overall strains and damage is derived. The damage evolution is stated on the smallest scale of interest and nonlocal weighted

Jacob Fish; Qing Yu

443

Tungsten filament as reinforcement for heat resistant composite materials  

Microsoft Academic Search

Fine tungsten filament is a promising reinforcement for composite materials. This is due to the good properties of alloys based on tungsten - high recrystallizatio n temperature, high strength and modulus of elasticity in a fairly wide temperature range, and, particularly valuable, deformability of a continuous filament with a diameter from a few microns to several millimeters. Thin filaments are

N. M. Fonshtein; G. N. Tikhomirova; V. F. Kotov; V. I. Shvarts

1971-01-01

444

Studies of Tension Test Specimens for Composite Material Testing.  

National Technical Information Service (NTIS)

This report covers stress analysis and experimental studies of four types of tension specimens designed for testing composite materials. Two ASTM specimen types (D3039 tab-ended and D638 dogbone) are considered, along with the bowtie (flat bar with linear...

B. S. Parker D. W. Oplinger K. R. Gandhi

1982-01-01

445

Fatigue life prediction and failure mechanisms of composite materials  

Microsoft Academic Search

Fatigue life prediction and failure mechanisms of composite materials are studied based on the fatigue modulus concept and experimental results. Single-stress level fatigue life is predicted using generalized fatigue modulus degradation model and resultant strain failure criterion. Cumulative damage models defined by fatigue modulus and resultant strains are derived as functions of fatigue cycle and applied stress. This approach can

K. S. Han; W. Hwang

1992-01-01

446

OVERVIEW OF RESEARCH ON COMPOSITE MATERIAL IMPACT BEHAVIOR  

Microsoft Academic Search

Impact resistance of composite materials is an important area of research. Fiber reinforced polymer structures typically respond very poorly to transverse impact events. In addition uncertainties about the dominant mechanisms of damage make it difficult to ascertain the effect of an impact event on the performance of a FRP structure. Compounding these considerations is the fact that, in some cases,

Kurt Henkhaus; Guillermo Ramirez

447

Design And Formability Of A New Composite Material  

NASA Astrophysics Data System (ADS)

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

Bolay, C.; Liewald, M.

2011-05-01

448

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

Microsoft Academic Search

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

STEVE R OSENCRANS; XUEFENG WANG; WILLIAM W INTER

2009-01-01

449

Electromagnetic Shielding of Oriented Carbon Fiber Composite Materials  

NASA Astrophysics Data System (ADS)

The paper analyses the electromagnetic shielding measurements of carbon fiber composite structure. In particular the shielding effectiveness is measured applying the nested reverberation chamber method in the frequency range of 3.5 GHz - 8.5 GHz. This method ensure a realistic electromagnetic excitation of the sample under test characterized by a random polarization and incoming direction. The paper also describes the material manufacturing procedure and gives important details about the sample mounting technique. Three material samples are considered which differ in carbon fiber orientation and stratification. Obtained results highlight the capability of such materials to behave as high-performance shields in the microwave region.

Micheli, D.; Laurenzi, S.; Mariani Primiani, V.; Moglie, F.; Gradoni, G.; Marchetti, M.

2012-05-01

450

Anisotropic electromagnetic properties of polymer composites containing oriented multiwall carbon nanotubes in respect to terahertz polarizer applications  

NASA Astrophysics Data System (ADS)

Polystyrene composites with 0.5 wt. % loading of oriented multiwall carbon nanotubes (MWCNTs) have been produced by forge rolling method. The composites showed anisotropy of transmission and reflection of terahertz radiation depending on sample orientation relative to the polarization of electromagnetic wave. The structural characteristics of composites (nanotube ordering, length, defectiveness) were estimated by fitting the theoretical dependencies calculated within the Clausius-Mossotti formalism for cylindrical particles to the experimental data. The presented model was used for prediction of electromagnetic response of composites containing oriented MWCNTs with various structural parameters in THz region.

Bychanok, D. S.; Shuba, M. V.; Kuzhir, P. P.; Maksimenko, S. A.; Kubarev, V. V.; Kanygin, M. A.; Sedelnikova, O. V.; Bulusheva, L. G.; Okotrub, A. V.

2013-09-01

451

A VERSATILE ULTRASONIC MEASUREMENT SYSTEM FOR FLAW DETECTION AND MATERIAL PROPERTY CHARACTERIZATION IN COMPOSITE MATERIALS  

Microsoft Academic Search

There is an ever increasing interest in the use of polymer-matrix composite materials in high performance automotive, marine, and aerospace structures. Ultrasonic NDE is a particularly effective method of insuring that such materials are fit for their intended purpose. Specifically, ultrasonic methods are inherently appropriate for internal-flaw detection and material-property characterization. Although flaw detection is certainly important, the real measurement

G. L. PETERSEN; B. B. CHICK; C. M. FORTUNKO

1992-01-01

452

Dual-nanoparticulate-reinforced aluminum matrix composite materials  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

453

Fracture properties of composite and glass ionomer dental restorative materials.  

PubMed

The double-torsion technique has been used to determine critical stress intensity factor (K1c) values for a range of composites and glass ionomer cements used in restorative dentistry. From these values and determined elastic modulus (E) and tensile strength (sigma T) values, two other fracture properties: G1c, the critical strain energy release rate and a0, the inherent flaw size, have been evaluated. Glass ionomers have low K1c and high a0 values, coarse particle composites high K1c and high a0 values, microfine materials low K1c and low a0 values and fine particle composites medium to high K1c values and medium to low a0 values. Light curing materials have K1c values according to their group but tend to have lower a0 values than their chemically curing analogues. Glass ionomers have very low G1c values; however, there is no significant difference between the G1c values of the composite groups. The K1c and a0 values have been used to predict relative performance of the materials in highly stressed restorations and wear. PMID:4077896

Goldman, M

1985-09-01

454

A Numerical Simulation to Propose a Flash Method for In Situ Detection of the Thermal Diffusivity of Anisotropic Thin Film Materials  

NASA Astrophysics Data System (ADS)

Strong anisotropy of thermal diffusivity is frequently observed in thin film materials. We propose an in situ experimental method to remotely measure radial and axial components of the thermal diffusivity. The method is based on the traditional laser flash technique but is specialized to also highly challenging experimental situations such as sample manufacture and use phase when thin films may be exposed to very high pressures or temperatures and to high temperature gradients. The method requires laser pulses of very short duration and fast measurement of transient temperature excursions in only radial directions on the surface of the thin film samples. The accuracy of the method is checked by comparison with results from a finite element calculation for a graphite sheet with high anisotropic conductivity that simulates a thermo-physical experiment.

Troitsky, Oleg Yu.; Reiss, Harald

2009-06-01

455

Ceramic composite material and process of manufacturing thereof  

US Patent & Trademark Office Database

A MgO/SiC composite material in which SiC particles with nano-meter order in size are dispersed within MgO matrix grains can be prepared by hot-pressing the mixture of fine MgO and SiC powders. Addition of SiC particles in the range of 5 volume percent to 50 volume percent to the MgO matrix increased remarkably the fracture strength and the hardness in a nanometer-order structure of the composite.

Ueda; Hisao (Urawa, JP); Sasaki; Hiroshi (Urawa, JP); Niihara; Koichi (Yokosuka, JP)

1992-07-14

456

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

457

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

458

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

459

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

460

The percolation staircase model and its manifestation in composite materials  

NASA Astrophysics Data System (ADS)

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