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1.
The problem of bifurcational instability of rectangular plates made of laminated composites with components subject to long-term
damage is formulated and solved by the proposed method. Numerical results are presented 相似文献
2.
The surface instability of laminated composites of regular structure is analyzed in a three-dimensional linearized formulation. A case is considered where the material is compressed by a surface distributed dead or follower load. Numerical results are presented for a specific problem. 相似文献
3.
《International Journal of Solids and Structures》2004,41(22-23):5979-5993
A modified single-pulse loading split Hopkinson torsion bar (SSHTB) is introduced to investigate adiabatic shear banding behavior in SiCp particle reinforced 2024 Al composites in this work. The experimental results showed that formation of adiabatic shear band in the composite with smaller particles is more readily observed than that in the composite with larger particles. To characterize this size-dependent deformation localization behavior of particle reinforced metal matrix composites (MMCp), a strain gradient dependent shear instability analysis was performed. The result demonstrated that high strain gradient provides a deriving force for the formation of adiabatic shear banding in MMCp. 相似文献
4.
Aude Hauert 《Journal of the mechanics and physics of solids》2009,57(11):1781-1800
Weibull parameters of angular alumina particles are determined from experimental tensile test data on high-ceramic-content metal matrix composites using a micromechanical model that accounts for internal damage in the form of particle cracking, the dominant damage mode in these composites. The fraction of broken particles is assessed from the drop of Young's modulus and particle fracture is assumed to be stress controlled. Two extreme load-sharing modes, namely a purely local and a global load-sharing mode, are considered to account for the load redistribution due to particle fracture. Consistent powder strength parameters can be thus “back-calculated” for particles that are embedded in different Al-Cu matrices. On the other hand, this calculation fails for pure Al matrix composites, which exhibit a much larger strain to failure than Al-Cu matrix composites. It is shown that for Al matrix composites, the role of plastic (composite) strain on particle fracture constitutes a second parameter governing particle damage. This finding is rationalized by particle-particle interactions in these tightly packed ceramic particle-reinforced composites, and by the increase of matrix stress heterogeneity that is brought with increasing plastic strain. Failure of the alloyed matrix composites is well described by the (lower bound) local load-sharing micromechanical model, which predicts a catastrophic failure due to an avalanche of damage. The same model predicts failure of pure aluminium matrix composites to occur at the onset of tensile instability, also in agreement with experimental results once the role of plastic strain on damage accumulation is accounted for. 相似文献
5.
Macroscopic instabilities of fiber reinforced composites undergoing large deformations are studied. Analytical predictions
for the onset of instability are determined by application of a new variational estimate for the behavior of hyperelastic
composites. The resulting, closed-form expressions, are compared with corresponding predictions of finite element simulations.
The simulations are performed with 3-D models of periodic composites with hexagonal unit cell subjected to compression along
the fibers as well as to non-aligned compression. Throughout, the analytical predictions for the failures of neo-Hookean and
Gent composites are in agreement with the numerical simulations. It is found that the critical stretch ratio for Gent composites
is close to the one determined for neo-Hookean composites with similar volume fractions and contrasts between the phases properties.
During non-aligned compression the fibers rotate and hence, for some loading directions, the compression along the fibers
never reaches the level at which loss of stability may occur. 相似文献
6.
M.D. Nestorovi? 《Journal of the mechanics and physics of solids》2004,52(4):941-974
A limiting factor in the design of fiber-reinforced composites is their failure under axial compression along the fiber direction. These critical axial stresses are significantly reduced in the presence of shear stresses. This investigation is motivated by the desire to study the onset of failure in fiber-reinforced composites under arbitrary multi-axial loading and in the absence of the experimentally inevitable imperfections and finite boundaries.By using a finite strain continuum mechanics formulation for the bifurcation (buckling) problem of a rate-independent, perfectly periodic (layered) solid of infinite extent, we are able to study the influence of load orientation, material properties and fiber volume fraction on the onset of instability in fiber-reinforced composites. Two applications of the general theory are presented in detail, one for a finitely strained elastic rubber composite and another for a graphite-epoxy composite, whose constitutive properties have been determined experimentally. For the latter case, extensive comparisons are made between the predictions of our general theory and the available experimental results as well as to the existing approximate structural theories. It is found that the load orientation, material properties and fiber volume fraction have substantial effects on the onset of failure stresses as well as on the type of the corresponding mode (local or global). 相似文献
7.
The problem of bifurcation instability of shells of revolution made of particulate composites with components subject to long-term
damage is formulated and solved 相似文献
8.
9.
《European Journal of Mechanics - A/Solids》2002,21(2):333-346
The questions of a dynamical stability and instability of soliton-like solutions (solitary pulses) of the Hamiltonian equations, describing planar waves in nonlinear elastic composites are considered, both in the presence as well as in the absence of the anisotropy. In the anisotropic case one has the slow and the fast two-parametric soliton families on the background of the quiescent state. In the absence of the anisotropy these two families coalesce into the unique three parametric family. It was shown recently that solitary pulses of the slow family in the anisotropic composite and pulses in the isotropic composite are stable when their speeds lie inside a certain range, the so-called range of stability. In the present paper, on the basis of numerical solving of the Cauchy problem for the basic governing equations, the classification is given of the types of instability of solitary pulses from the fast family for all range of speeds as well as in the case of the slow family and in the isotropic case, when the speeds of the pulses lie without the range of stability. The first type of instability is the blow-up instability for the slow anisotropic and isotropic pulses, living without the range of stability and also for high amplitude fast anisotropic pulses. The second type of instability is the instability resulting in energy exchange between the components of strain tensor for low amplitude fast anisotropic solitary pulses. The reasons of the both types of instability are discussed in detail.The interaction between the pairs of solitary pulses of different nature is investigated both analytically as well as numerically. It is found out that solitary pulses having the different polarization, i.e. different sign of amplitudes, can form bound states, oscillating about the common center, subjected to a motion with a constant speed, approximately equal to the average of speeds of two pulses when they are far apart. 相似文献
10.
A. N. Guz' 《International Applied Mechanics》1982,18(6):489-494
Conclusions Thus, based on the concepts in [5–7], the beginning of fracture of a composite in compression along a plane containing cracks can be represented as follows. If the material has not fractured already, then local fracture necessarily occurs next to the cracks at a value of compressive load corresponding to surface instability. Here, the upper limit of the ultimate theoretical strength corresponds to the minimum value of the shear modulus. This fracture mechanism can be seen in composites reinforced with high-modulus fibers. It should be noted that fracture can also take place on free surfaces of the material at these load values as a result of surface instability [1]. If the area of the free surface (lateral surface) of the material is substantially less than the total area of the cracks present throughout the volume of the material, then obviously the cracks will be the deciding factor in the fracture mechanism. The above-noted conclusions and quantitative abalysis were made only for a linearly elastic, orthotropic material with a high shear stiffness (brittle fracture), while the general results obtained in the present article also pertain to nonlinearly elastopiastic models. The results can be refined for more complex models. It must also be noted that the theoretical ultimate strength may be reduced substantially if the interaction of cracks located in parallel planes during instability is considered. This feature of the fracture mechanism was noted in note 6 in the article [6]. Composite materials generally have a fairly large number of cracks in planes and surfaces along the reinforcing elements. In connection with this, for composites it is best to allow for interaction of cracks located in parallel planes, which in turn should lead to a substantial reduction in the theoretical ultimate strength value obtained in the present article.Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Prikladnaya Mekhanika, Vol. 18, No. 6, pp. 3–9, June, 1982. 相似文献
11.
Domenico Bruno Fabrizio Greco Paolo Lonetti Paolo Nevone Blasi Girolamo Sgambitterra 《International Journal of Solids and Structures》2010,47(20):2806-2824
An analysis of the effects of microscopic instabilities on the homogenized response of heterogeneous solids with periodic microstructure and incrementally linear constitutive law is here carried out. In order to investigate the possibility to obtain a conservative prediction of microscopic primary instability in terms of homogenized properties, novel macroscopic constitutive stability measures are introduced, corresponding to the positive definiteness of the homogenized moduli tensors relative to a class of conjugate stress–strain pairs.Numerical simulations, addressed to hyperelastic microstructural models representing cellular solids and reinforced composites, are worked out through the implementation of an innovative one-way coupled finite element formulation able to determine sequentially the principal equilibrium solution, the incremental equilibrium solutions providing homogenized moduli and the stability eigenvalue problem solution, for a given monotonic macrostrain path. Both uniaxial and equibiaxial loading conditions are considered.The exact microscopic stability region in the macrostrain space, obtained by taking into account microstructural details, is compared with the macroscopic stability regions determined by means of the introduced macroscopic constitutive measures. These results highlight how the conservativeness of the adopted macroscopic constitutive stability measure with respect to microscopic primary instability, strictly depends on the type of loading condition (tensile or compressive) and the kind of microstructure. 相似文献
12.
A review is presented of the results on the near-surface instability of fiber composites under compression. The article reviews
those results obtained within the framework of the model of a piecewise-uniform medium with the use of the three-dimensional
linearized theory of deformable bodies. A general statement of the problem is given. Some important specific problems are
formulated and methods for solving them are proposed. A numerical study is performed for typical cases which permit the analysis
of mechanical effects associated with the loss of stability near a boundary.
S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Prikladnaya
Mekhanika, Vol. 35, No. 7, pp. 3–34, July, 1999. 相似文献
13.
Aude Hauert 《Journal of the mechanics and physics of solids》2009,57(3):473-499
We present an analytical micromechanical model designed to simulate the tensile stress-strain behaviour and failure of damaging composites containing a high volume fraction of reinforcing particles. One internal damage micromechanism is considered, namely particle fracture, which is assumed to obey a Weibull distribution. Final composite tensile failure occurs when one of two possible failure criteria is reached, given by (i) the onset of tensile instability, or (ii) an “avalanche-like” propagation of particle breaks to neighbouring particles. We show that an experimentally observed transition from failure by tensile instability to abrupt failure resulting from an increase of matrix strength can be mimicked by the model because local load-sharing (i.e. load transfer from a broken particle to its immediate neighbours) is accounted for. 相似文献
14.
The bifurcation instability problem for rectangular plates made of particulate composites with nonlinear elastic matrix and
damaged inclusions is formulated and solved
__________
Translated from Prikladnaya Mekhanika, Vol. 43, No. 7, pp. 79–89, July 2007. 相似文献
15.
The bifurcation instability problem for cylindrical shells made of particulate composites with nonlinear elastic inclusions
and damageable matrix is formulated and solved
__________
Translated from Prikladnaya Mekhanika, Vol. 43, No. 10, pp. 68–79, October 2007. 相似文献
16.
The problem of bifurcation instability of shells of revolution made of particulate composites with physically nonlinear matrix
and damageable inclusions is formulated and solved
__________
Translated from Prikladnaya Mekhanika, Vol. 44, No. 6, pp. 70–80, June 2008. 相似文献
17.
The bifurcation instability problem for shells of revolution made of particulate composites with nonlinear elastic inclusions
and damageable matrix is formulated and solved
__________
Translated from Prikladnaya Mekhanika, Vol. 43, No. 11, pp. 55–65, November 2007. 相似文献
18.
The bifurcation instability problem for cylindrical shells made of particulate composites with nonlinear elastic matrix and
damaged inclusions is formulated and solved
__________
Translated from Prikladnaya Mekhanika, Vol. 43, No. 8, pp. 80–91, August 2007. 相似文献
19.
《International Journal of Solids and Structures》2003,40(25):7155-7179
Graded materials are multiphase composites with continuously varying thermophysical properties. The concept provides material scientists and engineers with an important tool to develop new materials tailored for some specific applications. One such application of this new class of materials is as top coats or interfacial regions in thermal barrier systems. A widely observed failure mode in these layered materials is known to be interfacial cracking that leads to spallation. In many cases it is the buckling instability of coating under mechanically or thermally induced compressive stresses that triggers spallation. Under in-plane loading since the linear elastic small deformation theory gives only a trivial solution, in this study the plane strain interface crack problem for a graded coating bonded to a homogeneous substrate is formulated by using a kinematically nonlinear continuum theory. Both the instability and the postbuckling problems are considered. The main objective of the study is the investigation of the influence of material nonhomogeneity, kinematic nonlinearity and plate approximation on the critical instability load and on such fracture mechanics parameters as strain energy release rate, stress intensity factors and crack opening displacements. 相似文献
20.
本文用广义胞元法结合应力集中系数模型,从细观、宏观力学结合的角度,预测了弱界面复合材料偏轴拉伸强度值.用广义胞元法/高精度广义胞元法计算复合材料开裂前和开裂后的应力场,引入基体应力集中系数以得到基体真实应力.在计算真实应力时根据宏观试验现象考量是否对界面开裂后的复合材料进行刚度衰减,最终形成4种方案计算出复合材料的偏轴拉伸强度.通过对比芳纶纤维和亚麻纤维两种弱界面复合材料的偏轴拉伸强度试验值,找到了最可靠的预报方案并具有良好的预报精度. 相似文献