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1.
Measuring and modeling the thermal conductivities of three-dimensionally woven fabric composites 总被引:1,自引:0,他引:1
The effect of a three-dimensional fiber reinforcement on the out-of-plane thermal conductivity of composite materials is investigated.
Composite preforms with different fibers in the thickness direction were fabricated. After in fusion by using a vacuum-assisted
resin transfer molding process, their through-thickness thermal conductivities were evaluated. The measured thermal conductivities
showed a significant increase compared with those of a typical laminated composite. Although the through-thickness thermal
conductivity of the samples increased with through-thickness fiber volume fraction, its values did not match those predicted
by the simple rule of mixtures. By using finite-element models to better under stand the behavior of the composite material,
improvements in an existing analytical model were performed to predict the effective thermal conductivity as a function of
material properties and in-contact thermal properties of the composite.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 45, No. 2, pp. 241–254, March–April, 2009. 相似文献
2.
On the basis of an expression for the scattering phase function of an individual fiber, relations modeling radiative properties
of fibrous composites are obtained. We calculate the temperature state of a layer of such a material under condition of external
thermal radiation. Dependences of temperature distributions on the volume fraction of fibers in the composite, their reflectance,
and size are investigated.
Translated from Matematychni Metody ta Fizyko-Mekhanichni Polya, Vol. 51, No. 1, pp. 185–193, January–March, 2008. 相似文献
3.
A. P. Marukhin 《Mechanics of Composite Materials》2007,43(6):561-572
A method of primers is elaborated which allows one to calculate the distribution function of durability of a composite material
in tension in the reinforcement direction. Integral and differential equations for calculating the probabilities of formation
of primers and destruction of a material caused by their formation are presented. Distribution functions of material strength
for the parameter of Weibull distribution of fiber strength on the interval 2.1 ≤ β
f ≤ 50.1 are calculated. From the functions, the average values and root-mean-square deviations of material strength are found.
The results obtained agree well with calculations by using the structural-imitation simulation. The distribution functions
of material strength with a high precision are approximated by the three-parameter Weibull distributions. The distribution
parameters are approximated by the linear functions of ln (βf).
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 6, pp. 823–838, November–December, 2007. 相似文献
4.
L. Nazarenko L. P. Khoroshun W. H. Müller B. R. Wille 《Mechanics of Composite Materials》2009,45(1):11-20
A model of deformation of stochastic composites subjected to microdamage is developed for the case of orthotropic materials
with microdamages accumulating in the fibers. The composite is treated as a matrix strengthened with elliptic fibers with
orthotropic elastic properties. The fractured microvolumes are modeled by a system of randomly distributed quasi-spherical
pores. The porosity balance equation and relations for determining the effective elastic moduli for the case of a fibrous
composite with orthotropic components are used as the fundamental relations. The fracture criterion is given as a limit value
of the intensity of average shear stresses occurring in the undamaged part of the material, which is assumed to be a random
function of coordinates and is described by the Weibull distribution. Based on an analytical and numerical approach, the algorithm
for determining the nonlinear deformation properties of such a material is constructed. The nonlinearity of composite deformations
is caused by the accumulation of microdamages in the fibers. By using a numerical solution, the nonlinear stress–strain diagrams
for an orthotropic composite in uniaxial tension are obtained.
Translated from Mekhanika Kompozitnykh Materialov, Vol. 45, No. 1, pp. 17–30, January–February, 2009. 相似文献
5.
D. P. Aleksandrov 《Mechanics of Composite Materials》2005,41(6):541-552
The mechanical state of a press-powder filler for pyroautomatics system units of aerospace equipment during their long-term
storage is investigated. With the use of the endochronic approach, the rheological properties of a dispersedly reinforced
composite are simulated based on the conceptions of linear and nonlinear creep. Analytical expressions of constitutive relations
of creep and strength for the composites are obtained.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 6, pp. 803–818, November–December, 2005. 相似文献
6.
We deal with the thermomechanical response of multilayer satin weave carbon-fiber-reinforced polymer (CFRP) laminates with
internal and/or edge cracks and temperature-dependent material properties subjected to tensile loading at cryogenic temperatures.
The composite material is assumed to be under the generalized plane strain. Cracks are located in the transverse fiber bundles
and extend to the interfaces between two fiber bundles. A finite-element model is employed to study the influence of residual
thermal stresses on the mechanical behavior of multilayer CFRP woven laminates with cracks. Numerical calculations are carried
out, and Young’s modulus and stress distributions near the crack tip are shown graphically.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 4, pp. 479–492, July–August, 2008. 相似文献
7.
L. V. Nazarenko 《Journal of Mathematical Sciences》2009,160(4):429-442
In the present paper, a model of deformation of stochastic composites under microdamaging is developed for the case of orthotropic
composite, when the microdamages are accumulated in the matrix. The composite is treated as an isotropic matrix strengthened
by three-axial ellipsoidal inclusions with orthotropic symmetry of elastic properties. It is assumed that the loading process
leads to accumulation of damages in the matrix. Fractured microvolumes are modeled by a system of randomly distributed quasispherical
pores. The porosity balance equation and relations for determining the effective elastic moduli for the case of a composite
with orthotropic components are taken as the basic relations. The fracture criterion is assumed to be given as the limit value
of the intensity of average shear stresses occurring in the undamaged part of the material. Based on the analytical and numerical
approach, an algorithm for the determination of nonlinear deformation properties of such a material is constructed. The nonlinearity
of composite deformations is caused by the accumulation of microdamages in the matrix. Using the numerical solution, nonlinear
stress-strain diagrams for the orthotropic composite in the case of biaxial extension are obtained.
Published in Matematychni Metody ta Fizyko-Mekhanichni Polya, Vol. 51, No. 1, pp. 121–130, January–March, 2008. 相似文献
8.
The stability problem is solved for cylindrical shells made of a laminated composite whose directions of layer reinforcement
are not aligned with coordinate axes of the shell midsurface. Each layer of the composite is modeled by an anisotropic material
with one plane of symmetry. The resolving functions of the mixed variant of shell theory are approximated by trigonometric
series satisfying boundary conditions. The stability of the shells under axial compression, external pressure, and torsion
is investigated. A comparison with calculation data obtained within the framework of an orthotropic body model is carried
out. It is shown that this model leads to considerably erroneous critical loads for some structures of the composites.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 5, pp. 651–662, September–October, 2005. 相似文献
9.
L. V. Nazarenko 《Journal of Mathematical Sciences》2010,167(2):217-231
In the present work, a model of nonlinear deformation of stochastic composites under microdamaging is developed for the case
of a composite with orthotropic inclusions, when microdefects are accumulated in the matrix. The composite is treated as an
isotropic matrix strengthened by triaxial arbitrarily oriented ellipsoidal inclusions with orthotropic symmetry of the elastic
properties. It is assumed that the process of loading leads to accumulation of damage in the matrix. Fractured microvolumes
are modeled by a system of randomly distributed quasispherical pores. The porosity balance equation and relations for determining
the effective elastic modules in the case of orthotropic components are taken as basic relations. The fracture criterion is
specified as the limiting value of the intensity of average shear stresses acting in the intact part of the material. On the
basis of the analytic and numerical approach, we propose an algorithm for the determination of nonlinear deformation properties
of the investigated material. The nonlinearity of composite deformations is caused by the finiteness of deformations. By using
the numerical solution, the nonlinear stress–strain diagrams are predicted and discussed for an orthotropic composite material
for various cases of orientation of inclusions in the matrix. 相似文献
10.
S. V. Shil’ko E. M. Petrokovets Yu. M. Pleskachevskii 《Mechanics of Composite Materials》2006,42(5):477-484
The adaptive mode of frictional interaction has been studied as a self-locking effect upon contact deformation of isotropic
and anisotropic auxetic materials with a negative Poisson ratio. This effect manifests itself in the fact that the bearing
capacity of the joint rises with increasing shear load. In particular, the parameters of stress state (contact load, tangential
stresses, slippage, etc.) were determined for a double-lap joint under conditions of compression with or with out shear. The
contact interaction was analyzed by the finite-element method for three profiles of symmetrically located contact elements
(plane, cylindrical, and wedge-shaped). The Poisson ratio was varied within the range theoretically admissible for isotropic
elastic media. Analogous calculations were also performed for a joint with a deformed element made of an anisotropic auxetic
composite, whose reinforcement angle was varied. The maximum loads, tangential stresses, and slippage are obtained as nonlinear
functions of Poisson ratio (in the isotropic case) and reinforcement angle of the composite material. The stress concentration
and the increased ultimate shear forces are also estimated.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 5, pp. 681–692, September–October, 2006. 相似文献
11.
The paper presents results of an experimental investigations carried out to estimate the cooperation between a steel bar reinforcement
and round concrete cylinders confined by a carbon-epoxy composite, concerning the increase in the concrete compression strength
due the composite wrapping. The steel bar reinforcement with its yield stress considerably increases the bearing capacity
of concrete. This also happens above the unconfined concrete strength of specimens. The onset of reinforcement yielding roughly
coincides with reaching of the unconfined concrete strength at a compressive strain of ≈0.20%, and therefore it does not produce
a change in the tangent modulus of the stress-strain relationships above the limit of linearity.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 3, pp. 293–308, May–June, 2007. 相似文献
12.
The free-vibration behavior of symmetrically laminated fiber-reinforced composite beams with different boundary conditions
is examined. The effects of shear deformation and rotary inertia, separately and/or in combination, on the free-vibration
properties of the beams are investigated. The finite-difference method is used to solve the partial differential equations
describing the free-vibration motion in each case. The effect of shear deformation on the natural frequencies is considerable,
especially for higher frequencies, whereas the influence of rotary inertia is less significant. The study includes comparisons
with results available in the literature. In addition, the impact of such factors as the span/depth ratio, fiber orientation,
stacking sequence, and material type on free vibrations of the composite beams is investigated.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 3, pp. 331–346, May–June, 2006. 相似文献
13.
C. Gonilho Pereira R. Fangueiro S. Jalali M. Araujo P. Marques 《Mechanics of Composite Materials》2008,44(3):221-230
This paper reports on the development of braided reinforced composite rods as a substitute for the steel reinforcement in
concrete. The research work aims at understanding the mechanical behaviour of core-reinforced braided fabrics and braided
reinforced composite rods, namely concerning the influence of the braiding angle, the type of core reinforcement fibre, and
preloading and postloading conditions. The core-reinforced braided fabrics were made from polyester fibres for producing braided
structures, and E-glass, carbon, HT polyethylene, and sisal fibres were used for the core reinforcement. The braided reinforced
composite rods were obtained by impregnating the core-reinforced braided fabric with a vinyl ester resin. The preloading of
the core-reinforced braided fabrics and the postloading of the braided reinforced composite rods were performed in three and
two stages, respectively. The results of tensile tests carried out on different samples of core-reinforced braided fabrics
are presented and discussed. The tensile and bending properties of the braided reinforced composite rods have been evaluated,
and the results obtained are presented, discussed, and compared with those of conventional materials, such as steel.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 4, pp. 327–338, May–June, 2008. 相似文献
14.
The main focus of the present paper is the estimation of the macroscopic stress–strain behavior of a particulate composite.
A composite with a cross-linked polymer matrix in a rubbery state filled with an alumina-based mineral filler is investigated
by means of the finite-element method. The hyperelastic material behavior of the matrix is described by the Mooney–Rivlin
material model. Numerical models on the basis of unit cells are developed. The existence of a discontinuity (breaking) in
the matrix at higher loading levels is taken into account to obtain a more accurate estimate for the stress–strain behavior
of the particulate composite investigated. The numerical results obtained are compared with an experimental stress–strain
curve, and a good agreement is found to exist. The paper can contribute to a better understanding of the behavior and failure
of particulate composites with a polymer matrix. 相似文献
15.
L. P. Khoroshun 《Journal of Mathematical Sciences》2010,165(2):221-239
We propose a thermodynamic method and a statistical one for constructing the constitutive equations of elastoviscoplastic
deformation and strengthening of materials. The thermodynamic method is based on the energy conservation law as well as the
equations of entropy balance and entropy generation in the presence of self-equilibrated internal microstresses, which are
characterized by coupled strengthening parameters. The general constitutive equations consist of the relations between thermodynamic
flows and forces, which follow from nonnegativity of entropy generation and satisfy the generalized Onsager principle, as
well as the thermoelasticity relations and the expression for entropy, which follow from the energy conservation law. The
specific constitutive equations are obtained on the basis of representation of the energy dissipation rate as a sum of two
constituents that describe translational and isotropic strengthening and are approximated by power and hyperbolic sine laws.
Starting from the stochastic microstructural concepts, we construct the constitutive equations of elastoviscoplastic deformation
and strengthening on the basis of the linear model of thermoelasticity and the nonlinear Maxwell model for spherical and deviatoric
components of microstresses and microstrains, respectively. The solution of the problem of the effective properties and stress-strain
state of a three-component material is constructed with the use of the combined Voigt–Reuss scheme and leads to constitutive
equations coinciding, as to their form, with similar equations constructed by the thermodynamic method. 相似文献
16.
In this work a material model for shape memory alloy (SMA) fibers is presented. A constitutive model is provided which aims for computational use. The presented model incorporates all relevant material nonlinear phenomena. It takes pseudoplasticity into account as well as pseudoelasticity and further the shape memory effect (SME). The constrained SME (CSME) and the two-way SME are covered by the presented material model. The constitutive model is implemented in a one-dimensional truss formulation and in a 3D-rebar element. Both formulations are used to model fiber composite structures. Those are described by the use of a non-conforming and a conforming mesh on the mesoscale. The numerical examples show the capability of the formulation. Different meshing strategies for the fiber–matrix compound are discussed. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
17.
R. Brenner 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2010,16(1):919-927
A numerical scheme based on fast Fourier transform is presented to compute the effective response and the local fields within
a heterogeneous material which exhibits a coupled constitutive law. It consists in the iterative resolution of periodic coupled
Lippmann–Schwinger equations. This approach is illustrated in the case of electroelastic composite materials. By using an
augmented Lagrangian formulation, a simple iterative scheme relying on the uncoupled Green operators for the elastic and electrostatics
problems is proposed. This computational framework, which allows to consider composite materials with an infinite contrast
on the local properties, is assessed in the case of porous and fiber-reinforced piezoelectric materials. 相似文献
18.
The problem on the elastoplastic deformation of reinforced shells of variable thickness under thermal and force loadings is
formulated. A qualitative analysis of the problem is carried out and its linearization is indicated. Calculations of isotropic
and metal composite cylindrical shells have shown that the load-carrying capacity of shell structures under elastoplastic
deformations is several times (sometimes by an order of magnitude) higher than under purely elastic ones; the heating of shells
with certain patterns of reinforcement sharply reduces their resistance to elastic deformations, but only slightly affects
their resistance to elastoplastic ones; not always does the reinforcement in the directions of principal stresses and strains
provide the greatest load-carrying capacity of a shell; there are reinforcement schemes that ensure practically the same resistance
of shells at different types of their fastening.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 6, pp. 707–728, November–December, 2006. 相似文献
19.
Junjie Ye Xuefeng Chen Zhi Zhai Bing Li Yugang Duan Zhengjia He 《Mechanics of Composite Materials》2010,46(4):405-416
This paper aims to investigate the effect of microstructure parameters (such as the cross-sectional shape of fibers and fiber
volume fraction) on the stress–strain behavior of unidirectional composites subjected to off-axis loadings. A micromechanical
model with a periodic microstructure is used to analyze a representative volume element. The fiber is linearly elastic, but
the matrix is nonlinear. The Bodner–Partom model is used to characterize the nonlinear response of the fiber-reinforced composites.
The analytical results obtained show that the flow stress of composites with square fibers is higher than with circular or
elliptic ones. The difference in the elastoplastic response, which is affected by the fiber shape, can be disregarded if the
fiber volume fraction is smaller than 0.15. Furthermore, the effect of fiber shape on the stress–strain behavior of the composite
can be ignored if the off-axis loading angle is smaller than 30°. 相似文献
20.
For a consistent lightweight design the consideration of the nonlinear macroscopic material behaviour of composites, which is amongst others driven by damage and strain-rate effects on the mesoscale, is required. Therefore, a modelling approach using numerical homogenization techniques is applied to predict the effective nonlinear material behaviour of the composite based on the finite element simulation of a representative volume element (RVE). In this RVE suitable constitutive relations account for the material behaviour of each constituents. While the reinforcing glass fibres are assumed to remain linear elastic, a viscoplastic constitutive law is applied to represent the strain-rate dependent, inelastic deformation of the matrix material. In order to analyse the influence of the nonlinear matrix material behaviour on the global mechanical response of the composite, effective stress-strain-curves are computed for different load cases and compared to experimental observations. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献