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1.
The transient creep of a UD composite with a quadratic arrangement of elastic fibers of quadratic cross section is investigated.
The deformational properties of the composite are determined from the known properties of its constituents. A structural model
of the UD composite is developed, whose minimal elementary cell contains four elements. The stress-strain state of the elements
is assumed homogeneous. Two types of basic and resolving governing equations of transient creep are deduced, which are based
on static or kinematic assumptions. In each of the cases, a formula for the longitudinal elastic shear modulus of the composite
is found. The stationary solutions of creep equations allow one to obtain formulas of the steady-state creep of the composite
in a form similar to Norton’s law. Numerical calculations are also performed, and a comparison of the results with data given
in the literature bears witness to the efficiency of the models developed and the solutions obtained.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 4, pp. 437–448, July–August, 2007. 相似文献
2.
L. A. Golotina L. L. Kozhevnikova T. B. Koshkina 《Mechanics of Composite Materials》2008,44(6):633-640
Composites with an elastomeric matrix containing rigid particles of diameter 10–1000 μm are studied. One of possible mechanisms
of the rheological behavior of such filled systems, related to the origination and growth of vacuoles near the rigid inclusions
in a viscous matrix, is considered. For simulating the mechanism of formation of rheological properties of the filled elastomers,
we use a structural cell in the form of an elastomeric cylinder, whose height and diameter are equal in magnitude, with a
rigid spherical inclusion at its center. Deformation of the cells is examined with the observance of boundary conditions providing
the preservation of their close packing. The inclusion is assumed to be rigid, and the matrix properties are described by
equations of the linear hereditary viscoelasticity theory. The formation of vacuoles is described by using the approach suggesting
that an initial debonding begins to propagate when the energy accumulated in the extended matrix reaches a value sufficient
to create a new interface. The heterogeneity of the composite is simulated by taking into account the variability of the local
filler concentration. Creep curves obtained for composite cells with different content of the solid phase are presented. Comparisons
between the numerical and experimental results show a satisfactory agreement.
Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 6, pp. 895–906, November–December, 2008. 相似文献
3.
E. A. Aliyev 《Mechanics of Composite Materials》2007,43(6):521-534
Within the framework of a piecewise homogenous body model and with the use of a three-dimensional linearized theory of stability
(TLTS), the local near-surface buckling of a material system consisting of a viscoelastic (elastic) half-plane, an elastic
(viscoelastic) bond layer, and a viscoelastic (elastic) covering layer is investigated. A plane-strain state is considered,
and it is assumed that the near-surface buckling instability is caused by the evolution of a local initial curving (imperfection)
of the elastic layer with time or with an external compressive force at fixed instants of time. The equations of TLTS are
obtained from the three-dimensional geometrically nonlinear equations of the theory of viscoelasticity by using the boundary-form
perturbation technique. A method for solving the problems considered by employing the Laplace and Fourier transformations
is developed. It is supposed that the aforementioned elastic layer has an insignificant initial local imperfection, and the
stability is lost if this imperfection starts to grow infinitely. Numerical results on the critical compressive force and
the critical time are presented. The influence of rheological parameters of the viscoelastic materials on the critical time
is investigated. The viscoelasticity of the materials is described by the Rabotnov fractional-exponential operator.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 6, pp. 771–788, November–December, 2007. 相似文献
4.
Within the frame work of the three-dimensional linearized theory of stability of deformable bodies (TLTSDB), the near-surface
buckling instability of a system consisting of a half-plane (substrate), a viscoelastic bond layer, and an elastic covering
layer is suggested. The equations of the TLTSDB are obtained from the three-dimensional geometrically non linear equations
of viscoelasticity theory by using the boundary-form perturbation technique. By employing the Laplace transform, a method
for solving the problem is developed. It is supposed that the covering layer has an insignificant initial imperfection. The
stability of the system is considered lost if the imperfection starts to increase and grows indefinitely. Numerical results
for the critical compressive force and the critical time are presented.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 4, pp. 517–530, July–August, 2006. 相似文献
5.
UD xFRP composites, i.e., isotropic plastics reinforced with long transversely isotropic fibres packed unidirectionally according
to the hexagonal scheme are considered. The constituent materials are geometrically and physically linear. The previous formulations
of the exact stiffness theory of such composites are revised, and the theory is developed further based on selected boundary-value
problems of elasticity theory. The numerical examples presented are focussed on testing the theory with account of previous
variants of this theory and experimental values of the effective elastic constants. The authors have pointed out that the
exact stiffness theory of UD xFRP composites, with the modifications proposed in our study, will be useful in the engineering
practice and in solving the current problems of the mechanics of composite materials.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 45, No. 1, pp. 109–144, January–February, 2009. 相似文献
6.
V. V. Moskvitin 《Mechanics of Composite Materials》1967,3(2):139-142
The author examines a simple extension, to the nonlinear case, of memory-type theory based on the Boltzmann-Volterra superposition principle. It is shown that given certain assumptions the quasi-linear theory of viscoelasticity reduces to introduction into the equations of linear memory theory of a single stress- or strain-intensity function. This function is determined from creep or relaxation tests. A successive-approximation method is presented for solving problems of nonlinear viscoelasticity with the aid of the equations introduced. It is shown that in the case of simple loading the equations of the theory of small elastic-plastic deformations are an analog of the equations considered.Mekhanika Polimerov, Vol. 3, No. 2, pp. 207–212, 1967 相似文献
7.
R. Yu. Amenzadeh 《Mechanics of Composite Materials》2009,45(2):159-164
The use of the hereditary theory for shells heterogeneous across their thickness is considered. A variational method is formulated
for calculating thin anisotropic shells made of a material whose deformation behavior can be described by relations of the
linear theory of viscoelasticity. In order to transform the corresponding functional into a form suitable for shells, some
assumptions related to concepts of the theory of thin shells are introduced. In the capacity of Euler equations, physical
relations, nonlinear equilibrium equations, and nonlinear boundary conditions are derived. The state equations are deduced
for a multilayered shell.
Translated from Mekhanika Kompozitnykh Materialov, Vol. 45, No. 2, pp. 231–240, March–April, 2009. 相似文献
8.
M. Klasztorny 《Mechanics of Composite Materials》2004,40(4):349-358
A rheological HWKK/H model for resins is developed taking into consideration the up-to-date analyses of experimental results. Constitutive compliance equations of linear are formulated for this model in the shear/bulk form, which describes, among other things, the first-rank reversible isothermal creep. The shear (distorsional) deformations are simulated with three independent stress history functions of fractional and normal exponential types. The volume deformations are simulated as perfectly elastic. The model is described by two elastic and six viscoelastic constants, namely three long-term creep coefficients and three retardation times.The constitutive compliance equations of viscoealsticity for resins are also formulated in the coupled form. Formulae for converting the constants of shear/bulk (uncoupled) viscoelasticity into the constants of coupled viscoelasticity are given too.An algorithm for identifying the material constants, based on the creep of uniaxially tensioned bar samples, is formulated in a way that gives unique results. The material constants are fiund for Epidian 53 epoxy and Polimal 109 polyester resins. The creep processes, simulated based on the experimental data, are presented graphically for both the resins examined. 相似文献
9.
A. A. Pan’kov 《Mechanics of Composite Materials》2000,36(1):19-36
A generalized self-consistent method [1, 2] is developed and applied to the boundary-value problems of composites with random
elastic properties of inclusions. The approach suggested makes it possible to allow for a random mutual arrangement, statistical
dispersion of elastic properties and sizes of the inclusions, and their mutual correlation in terms of special homogenized
indicator functions. For comparison, the analytical solutions and those obtained from a corresponding sequence of H+1 (H=0,1,…)
linked homogenized problems of the self-consistent method for the strain distribution in the inclusions and for the tensor
of effective elastic properties of the composite are given. A numerical calculation of the effective transversely isotropic
elastic characteristics for a unidirectional polydisperse fibrous composite is also presented.
Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 1, pp. 33–58, January–February, 2000. 相似文献
10.
K. Aniskevich O. Starkova J. Jansons A. Aniskevich 《Mechanics of Composite Materials》2010,46(4):375-386
A model composite — a silica-filled styrene-butadiene rubber with a various filler volume content — was tested for creep and
creep recovery at different tensile load levels to evaluate the effect of viscoelasticity on the deformational properties
of filled rubbers. A constitutive equation describing the diagram of equilibrium deformation of the composite in quasi-static
loading was obtained from an analysis of creep test results. The equation was common for the filled rubber at different filler
content. The existence of such a curve has been confirmed by experimental unloading diagrams registered in cyclic loading-unloading
tests. It is shown that the phenomenological equations obtained from an analysis of creep recovery test results can be used
successfully for describing the hysteresis loops of second and subsequent cycles for cyclic tests with a constant maximum
stretch ratio. 相似文献
11.
S. A. Kaloerov E. S. Goryanskaya Yu. B. Shapovalova 《Journal of Mathematical Sciences》2000,101(1):2773-2779
Generadized complex potentials are used to solve a problem for the elastic stressed state of a body with a general rectilinear
anisotropy in a two-dimensional stressed-deformed state. The body has longitudinal cavities, inclusions, planar cracks, or
rigid lamellar inclusions. A least-squares methods is used to reduce the problem to a system of linear algebraic equations
which is solved for the unknown constants in the complex potentials.
Donetsk State University. Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 29, pp. 63–70, 1999. 相似文献
12.
S. A. Kaloerov E. S. Goryanskaya Y. B. Shapovalova 《Journal of Mathematical Sciences》2000,101(6):3708-3717
A method is proposed for studying the two-dimensional stressed state of a multiply connected anisotropic body with cavities
and elastic and rigid inclusions, as well as planar cracks and rigid laminar inclusions. Generalized complex potentials, conformal
mapping, and the method of least squares are used. The problem is reduced to solving a system of linear algebraic equations.
Formulas are given for finding the stress intensity factors in the case of cracks and laminar inclusions. For an anisotropic
plate with a single elliptical hole or a crack and an elastic (rigid) inclusion, some numerical results are presented from
a study of the effect of the rigidity of the inclusion and the closeness of the contours to one another on the distribution
of stresses and the stress intensity factor.
Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 30, pp. 175–187, 1999. 相似文献
13.
14.
The authors investigate the creep of inhomogeneous materials consisting of a large number of stiff orthotropic elastic layers alternating with layers of linear isotropic viscoelastic material. The elastic layers are assumed to be almost plane; the functions describing the irregularities (curvature) form a random field. The averaged characteristics of the medium are found together with the variation of the averaged displacements and strains in time. An analogous problem was previously considered in [1, 6] on the assumption that the binder layers are elastic. The present paper is based on the equations of [1] and the elastic-viscoelastic correspondence principle [4]. When the correlation scales of the irregularities are small as compared with the dimensions of the body and the characteristic distances over which the averaged parameters of the stress-strain state vary appreciably is considered in detail. A relation is established between the creep functions for simple cases of the state of stress and the parameters characterizing the properties of the components, the properties of the random field of initial irregularities, etc. The development of perturbations with different wave numbers is investigated. The theory is used to describe the creep of reinforced layered plastics.Mekhanika Polimerov, Vol. 2, No. 5, pp. 755–762, 1966 相似文献
15.
Using the machinery of complex variable theory we study the stressed state in an unbouned medium of cyclically located thin
elastic inclusions of finite length. The problem is reduced to solving a system of two singular integro-differential equations.
A numerical analysis is carried out for the stress intensity factors in the vicinity of the ends of the inclusions.
Translated fromMatematichni Metodi ta Fiziko-Mekhanichni Polya, Vol. 40, No. 2, 1997, pp. 87–90. 相似文献
16.
V. I. Kushch 《Journal of Mathematical Sciences》1991,57(1):2897-2900
The problem is considered of thermal stresses in a composite material which is an elastic isotropic matrix with uniform spherical inclusions placed regularly within it. A solution is presented in the form of series for a system of double-periodic solutions of the equilibrium equation built up in a special way. An infinite set of linear algebraic equations of the normal type is obtained from the boundary conditions. Numerical studies are carried out for the stress distribution at the matrix-grain contact surface, and their nature in relation to the volume content of dispersed phase and geometric structure parameters of the composite is determined.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 19, pp. 90–93, 1988. 相似文献
17.
R. D. Maksimov J. Bitenieks E. Plume J. Zicans R. Merijs Meri 《Mechanics of Composite Materials》2012,48(1):47-56
Results of an investigation into the properties of polyethylene (PE) with small, no more than 5 wt.%, additions of multiwall
carbon nanotubes (CNTs) are reported. Specimens of the composite were prepared using a concentrate containing 31.6 wt.% of
nanotubes in the polyethylene matrix. The concentrate was fabricated by a patent in situ polymerization method. Experimental
data on the influence of CNT additions on the thermograms of differential scanning calorimetry, the crystallinity of the polyethylene
matrix, and the indices of mechanical properties (yield stress, strength, elastic modulus, ultimate elongation, and long-term
creep) of PE/CNT composite are obtained. A theoretical analysis of elastic properties of the PE/CNT composite was carried
out by using the Mori–Tanaka theory of an equivalent medium. The calculation results are compared with experimental data. 相似文献
18.
Models of composites with three-dimensional structure, a proposed problem solving method, and Rabotnov's creep operators were used assuming purely elastic deformation of the composite along the orientation of the fibers to determine the viscoelastic properties of composites on inclined surfaces in a three-dimensional stressed state. The formulas used in viscoelasticity theory in the elastic region of component deformation lead to results in satisfactory accord with the reported experimental elastic properties of composites with three-dimensional structure.A. A. Blagonravov Mechanical Engineering Institute, Russian Academy of Sciences, Moscow. Translated from Mekhanika Kompozitnykh Materialov, Vol. 32, No. 6, pp. 780–786, November–December, 1996. 相似文献
19.
V. A. Kochetkov 《Mechanics of Composite Materials》1996,31(4):337-345
A theoretical investigation was carried out to examine the possibilities of a structural approach to prediction of elastic constants, creep functions, and thermal properties of multiphase polymer composite materials filled with composite or hollow spherical Inclusions of several types. The problem of determining effective properties of the composite was solved by generalizing the effective medium method, a variant of the self-consistent method, for the case of a four-phase kernel-shell-matrix-equivalent homogeneous medium model. Exact analytical expressions for the bulk modulus thermal expansion coefficient, thermal conductivity coefficient, and specific heat were obtained. The solution for the shear modulus is given in the form of a nonlinear equation whose coefficients are the solution of a system of 12 linear equations.To be presented at the Ninth International Conference on the Mechanics of Composite Materials, Riga, October 1995.Published in Mekhanika Kompozitnykh Materialov, Vol. 31, No. 4, pp. 462–472, July–August, 1995. 相似文献
20.
Analysis results for the elastic properties of a composite with a small amount of coplanarly arranged platelike filler particles
are presented. The geometrical form of the particles is described by an oblate ellipsoid of revolution. The calculations are
performed by formulas obtained by using the Eshelby approach for media with a low concentration of inclusions. The effect
of anisometry of the ellipsoidal particles and of the ratio between the elastic moduli of the filler and matrix on the effective
elastic constants of the composite is discussed. Calculation results are compared with experimental data for the elastic moduli
of a nanocomposite containing completely exfoliated particles of an unmodified montmorillonite.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 4, pp. 493–504, July–August, 2008. 相似文献