共查询到20条相似文献,搜索用时 29 毫秒
1.
A variant of a stepwise analysis of the elastic properties of a carbon-nanotube-reinforced composite with account of the effect
of interphase layers between the nanotubes and the polymer matrix is reported. The preliminary calculation of the elastic
constants of a structural element incorporating a nanotube and an interphase layer and the subsequent calculation of independent
elastic constants of a composite with such transversely isotropic structural elements oriented in one direction are both performed
by using the Mori–Tanaka theory of an equivalent medium. The calculations are carried out for a wide range of ratios between
the elastic moduli of the interphase layer and matrix. The elastic constants of a composite with randomly oriented nanotubes
are obtained by using the method of orientational averaging. 相似文献
2.
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.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 4, pp. 493–504, July–August, 2008. 相似文献
3.
G. I. Petrashen V. V. Reshetnikov Yu. A. Surkov 《Journal of Mathematical Sciences》2007,142(6):2645-2654
A nonstationary problem concerning the propagation of low-frequency waves for a model that consists of a packet of elastic
layers lying on an elastic half-space is considered, and exact mathematical solutions in the form of repeated integrals are
constructed in three basic forms. It is proved that these solutions satisfy initial conditions. The representation of solutions
as a superposition of multiple waves is treated. Bibliography: 6 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 332, 2006, pp. 220–239. 相似文献
4.
Incompressible elastic material with a periodic system of pores is considered. Processes are studied with a typical length
which is much more than the typical diameter of pores and the typical distance between pores. Porous material behaves as a
certain “effective” material without pores in such processes. The method of calculation of effective moduli based on mathematical
homogenization theory is described. The estimates for the effective moduli are proved. The results of numerical calculations
of effective moduli for materials with spherical and cubic pores are presented. The dependence of the effective moduli on
the volume fracture of pores is investigated. The explicit formulae for effective coefficients are deduced. Comparison with
the effective moduli for compressible materials is performed.
Presented at the Ninth International Conference on the Mechanics of Composite Materials, Riga, October, 1995.
Lomonosov Moscow State University, Department of Mathematics and Mechanics, Moscow. Published in Mekhanika Kompozitnykh Materialov,
No. 5, pp. 579–587, September–October, 1996. 相似文献
5.
The identification of elastic properties of laminated composite plates from measured eigenfrequencies has been performed.
The elastic moduli of the laminates were determined by using a multilevel modeling and a two-step identification procedure.
At the first step, based on a genetic algorithm, the Young’s and shear moduli were found, but at the second one, by minimizing
an error function, the values of transverse moduli were refined.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 2, pp. 207–216, March–April, 2008. 相似文献
6.
A variant of determining the elastic characteristics of composites containing irregularly oriented shape-anisotropic filler
particles of two types (short fibers and thin platelets) is considered. The effective elastic constants of the composites
are calculated by using the method of orientational averaging of elastic characteristics of isolated transversely isotropic
structural elements reinforced with unidirectionally oriented short fibers or coplanarly arranged thin platelets. The superposition
of elastic properties of the irregularly oriented structural elements, with account of their orientational distribution in
the composite material, is accepted. The calculation results are compared with experimental data for the effective elastic
moduli of polymeric composites reinforced with short glass fibers and of polymeric nanocomposites containing the platelet-type
particles of organically modified montmorillonite.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 3, pp. 285–300, May–June, 2006. 相似文献
7.
Within the framework of a piecewise homogeneous body model, with the use of the three-dimensional linearized theory of elastic
waves in initially stressed bodies, the dynamical (time-harmonic) axisymmetric stress field in a finitely prestretched multilayered
slab resting on a rigid foundation is studied. It is assumed that the slab consists of two-layer packets. The elasticity of
layer materials is described by the Treloar potential. It is assumed that the material of the lower layer in the packets is
more rigid than that of the upper one. Numerical results are presented for the cases where the number of layers (packets)
in the slab is 2 (1), 4 (2), or 6 (3). These results concern the normal stresses acting on the interface between the layers
of the first, upper packet and on the interface between the first and second packets. The influence of the number, prestretch
level, and thickness of the layers on relation ships between the stresses and the frequency of the external force is analyzed.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 5, pp. 667–680, September–October, 2006. 相似文献
8.
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
9.
The plane problem of three-dimensional stability is solved for a transversely compressed composite material reinforced with
ribbons taking into account the inhomogeneous initial state. An approximate solution of the problems is based on the net method.
The effect of the ribbon form factor, the ratio between the elastic moduli of the matrix and filler, and Poisson ratio of
the filler on the critical deformation of the material is investigated.
Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 1, pp. 77–86, January–February, 2000. 相似文献
10.
An analytic-numerical method based on perturbations in the elastic moduli is proposed for solving problems involving the diffraction
of two-dimensional longitudinal-shear harmonic deformation waves on a cavity with a smooth curvilinear cross section in an
elastic medium with an anisotropy corresponding to a monoclinic system in the dynamic deformation plane. Results from a numerical
analysis of the distribution of the dynamic stresses in the near diffraction field are presented for the case of longitudinal
waves scattered on a dome-shaped cavity as the direction of the incident wave and the degree of anisotropy of the medium are
varied.
Donetsk State University. Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 30, pp. 137–147, 1999. 相似文献
11.
The transient response of sandwich beams, plates, and shells with viscoelastic layers under impulse loading is studied using
the finite element method. The viscoelastic material behavior is represented by a complex modulus model. An efficient method
using the fast Fourier transform is proposed. This method is based on the trigonometric representation of the input signals
and the matrix of the transfer functions. The present approach makes it possible to preserve exactly the frequency dependence
of the storage and loss moduli of viscoelastic materials. The logarithmic decrements are determined using the steady state
vibrations of sandwich structures to characterize their damping properties. Test problems and numerical examples are given
to demonstrate the validity and application of the approach suggested in this paper.
Submitted to the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000).
Published in Mekhanika Kompozitnykh Materialov, Vol. 36, No. 3, pp. 367–378, March–April, 2000. 相似文献
12.
13.
Results of an experimental investigation into the thermal behavior and mechanical properties of a room-temperature-cured epoxy
adhesive (diglycidyl ether of bisphenol A, DGEBA) cross-linked with polyetheramines and filled with different fillers, namely
nanosilica, liquid rubber (CTBN), and clay, are reported. The nanosilica and liquid rubber increased the flexural strength
and elastic modulus of the adhesive systems; the addition of clay particles raised the elastic modulus significantly, but
embrittled the adhesive. Establishing a correct cure time is very important for bonded-in timber structures, as it will affect
the bond strength. A study on the effect of cure time on the flexural strength was carried out, from which it follows that
the adhesives should be cured for at least 20 days at room temperature. The damping characteristics and the glass-transition
temperature of the adhesives were determined by using a dynamic mechanical thermal analysis. The results showed that the filled
adhesives had a higher storage modulus, which was in agreement with the elastic moduli determined from static bending tests.
The introduction of the fillers increased its glass-transition temperature considerably.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 5, pp. 599–614, September–October, 2006. 相似文献
14.
Sergio Conti Georg Dolzmann 《Calculus of Variations and Partial Differential Equations》2009,34(4):531-551
We derive a two-dimensional model for elastic plates as a Γ-limit of three-dimensional nonlinear elasticity with the constraint
of incompressibility. The resulting model describes plate bending, and is determined from the isochoric elastic moduli of
the three-dimensional problem. Without the constraint of incompressibility, a plate theory was first derived by Friesecke
et al. (Comm Pure Appl Math 55:1461–1506, 2002). We extend their result to the case of p growth at infinity with p ϵ [1, 2), and to the case of incompressible materials. The main difficulty is the construction of a recovery sequence which
satisfies the nonlinear constraint pointwise. One main ingredient is the density of smooth isometries in W
2,2 isometries, which was obtained by Pakzad (J Differ Geom 66:47–69, 2004) for convex domains and by Hornung (Comptes Rendus
Mathematique 346:189–192, 2008) for piecewise C
1 domains. 相似文献
15.
Z. A. Yanson 《Journal of Mathematical Sciences》2007,142(6):2689-2696
The whispering gallery modes propagating along the surface of an anisotropic elastic body are investigated with the use of
space-time caustic expansions and space-time ray series. Each surface mode modulated in amplitude and frequency, is interpreted
as a wave packet, with its amplitude’s maximum moving at a group velocity. On the boundary surface, asymptotic expressions
for the group velocity (as a function of time and coordinates) are derived, which are in agreement with analogous formulas
for Rayleigh waves of SV type in the isotropic case. Bibliography: 6 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 332, 2006, pp. 299–312. 相似文献
16.
V. Kalkis R. D. Maksimov M. Kalnins J. Zicans T. Bocoka O. Revjakin 《Mechanics of Composite Materials》2000,36(3):223-232
Gamma-irradiated blends of polyethylene (PE) with ethylene-propylene-diene copolymer (EPDM) and a thermotropic liquid-crystalline
polymer (LCP) are investigated at absorbed radiation doses not exceeding 150 kGy (10 kGy=1 Mrad). The temperature dependences
of elastic moduli, tension diagrams at a temperature above the melting point of the crystalline phase of PE, and long-term
strain recovery curves for oriented test specimens are presented. The kinetics of thermal relaxation and shrinkage stresses
in previously oriented composite specimens upon their heating and cooling is investigated. Data on the influence of LCP additions
on the adhesive interaction of the compositions with steel are obtained. The peculiarities of thermomechanical and adhesion
properties of these composites are discussed taking into account the morphologic and calorimetric data obtained.
Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 3, pp. 379–394, May–June, 2000. 相似文献
17.
The diffraction of a plane longitudinal harmonic wave on a cavity with a smooth curvilinear cross section in a rectilinearly
orthotropic medium is solved by using small perturbations in the elastic moduli and introducing generalized wave potentials.
Results are presented from a numerical analysis of the dynamic stresses in the near diffraction field and at the boundary
of an elliptical cavity including variations in the relative incident wavelength, eccentricity of the cavity, and degree of
anisotropy of the medium.
Donetsk State University. Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 29, pp. 102–110, 1999. 相似文献
18.
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
19.
Some inequalities similar to the Jackson theorem and the Landau-Hadamard-Kolmogorov theorem for the best approximations and
moduli of continuity of the derivatives of odd order with different steps are established. The inequalities are sharp if the
norm is uniform. Bibliography: 4 titles.
Translated fromProblemy Matematicheskogo Analiza, No. 19, 1999, pp. 69–87. 相似文献
20.
V. A. Buryachenko 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2005,56(6):1107-1115
We consider a linearly elastic composite medium, which consists of a homogeneous matrix containing a statistically uniform
random set of aligned fibers. Effective elastic moduli as well as the stress concentrator factors in the components are estimated.
The micromechanical approach is based on the Green’s function technique as well as on the generalization of the “multiparticle
effective field method” (MEFM, see for references, Buryachenko [1]). The refined version of the MEFM takes into account the
variation of the effective fields acting on each pair of fibers. The dependence of effective elastic moduli and stress concentrator
factors on the radial distribution function of the fiber locations is analyzed.
Received: October 20, 2004 相似文献