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1.
IntroductionRecently ,theinterphaseincompositeshasattractedtheattentionofmanyresearchers[1- 7].Someinterphasesareproducedbydesignandothersbychemicalreactionsinfabricatingcomposites.Fromtheviewpointofmechanicsofcompositematerials,oneofthefundamentalproblemsofcompositeswithinterphasesistopredicttheeffectivemoduli.Therearemanymethodsforpredictingeffectivemoduliofcomposites,suchasgeneralizedself_consistentmethod(GSCM) ,compositesphereandcompositecylindermodels (CCAandCSA)andIDDestimate ,etc … 相似文献
2.
In conjunction with the homogenization theory and the finite element method, the mathematical models for designing the corss-section
of composite shafts by maximizing the torsion rigidity are developed in this paper. To obtain the extremal torsion rigidity,
both the cross-section of the macro scale shaft and the representative microstructure of the composite material are optimized
using the new models. The micro scale computational model addresses the problem of finding the periodic microstructures with
extreme shear moduli. The optimal microstructure obtained with the new model and the homogenization method can be used to
improve and optimize natural or artificial materials. In order to be more practical for engineering applications, cellular
materials rather than ranked materials are used in the optimal process in the existence of optimal bounds for the elastic
properties. Moreover, the macro scale model is proposed to optimize the cross-section of the torsional shaft based on the
tailared composites. The validating optimal results show that the models are very effective in obtaining composites with extreme
elastic properties, and the cross-section of the composite shaft with the extremal torsion rigidity.
The project supported by the National Natural Science Foundation of China (10172078 and 10102018) 相似文献
3.
In the axial tensile failure process of intraply hybrid composites, the breakage of some fibers may lead to interfacial damage,
thus directly influencing the local stress concentrations near the sites of breakage. A modified shear-lag model, in which
the interfacial damage is considered, is proposed. Based on the model, the influence of interfacial shear strength on the
stress concentrations and the lengths of interfacial damage zone is first studied. The present results also provide an important
theoretical basis for investigating the failure mechanism and hybrid effects for such kind of composites.
Project supported by the National Natural Science Foundation of China (No. 199902004) and Guangdong Provincial Natural Science
Foundation (No. 000391). 相似文献
4.
In this paper, a systematic approach is proposed to obtain the macroscopic elastic-plastic constitutive relation of particle
reinforced composites (PRC). The strain energy density of PRC is analyzed based on the cell model, and the analytical formula
for the macro-constitutive relation of PRC is obtained. The strength effects of volume fraction of the particle and the strain
hardening exponent of matrix material on the macro-constitutive relation are investigated, the relation curve of strain versus
stress of PRC is calculated in detail. The present results are consistent with the results given in the existing references.
The project supported by the National Natural Science Foundation of China (No. 19704100) and National Science Foundation of
Chinese Academy of Sciences (Project KJ951-1-20). 相似文献
5.
A micromechanical model is developed to simulate the mechanical behaviors of discontinuous reinforced composites. The analysis
for a representative unit cell is based on the assumption of a periodic array of aligned reinforcements. The minimum energy
principle is used to determine the unknown coefficients of the displacement field of the unit cell. The constitutive behavior
of composites is studied to obtain the relationship between the main variables of matrix and reinforcements. It is concluded
that the flow strength of composites is strongly influenced by volume fraction, aspect ratio of reinforcement, and the strain
hardening exponent of matrix. An analytical constitutive relation of composites is obtained. The predicted results are in
agreement with the existing experimental and numerical results.
The project supported by the National Natural Science Foundation of China (19704100) and National Science Foundation of Chinese
Academy of Sciences (KJ951-1-20) 相似文献
6.
The clasto-plastic constitutive behaviors of continuous fiber reinforced composites under cyclic loadings are studied by the micromechanics method in which the equal-strain model is used in the fiber direction, the equal-stress model in the other directions. It is supposed that fiber is linearly elastic and matrix is clastic-viscoplastic. The constitutive equations of the matrix are described by Bodner-Partom's unified constitutive theory. Boron/Aluminum composite, as an example, is investigated in detail for an understanding of the stress-strain relations and initial yield behaviors of metal matrix composites. Present results are compared with the experimental data.The project was supported by the Chinese National Natural Science Foundation. 相似文献
7.
The weak point of the generalized self-consistent method (GSCM) is that its solution for the effective shear moduli involves
determining the complicated displacement and strain fields in constitutents. Furthermore, the effective moduli estimated by
GSCM cannot be expressed in an explicit form. Instead of following the procedure of GSCM, in this paper a generalized self-consistent
Mori-Tanaka method (GSCMTM) is developed by means of Hill's interface condition and the assumption that the strain in the
inclusion is uniform. A comparison with the existing theoretical and experimental results shows that the present GSCMTM is
sufficiently accurate to predict the effective moduli of the coated inclusion-based composite materials. Moreover, it is interesting
to find that the application of Hill's interface condition in volumetric domain is equivalent to the Mori-Tanaka average field
approximation.
This project was supported by the National Natural Science Foundation of China and China Postdoctoral Science Foundation. 相似文献
8.
Xiaoling Peng Jianyong Huang Lei Qin Chunyang Xiong Jing Fang 《Acta Mechanica Sinica》2009,25(4):565-570
A convenient technique is reported in this note for measuring elastic modulus of extremely soft material for cellular adhesion. Specimens of bending cylinder under gravity are used to avoid contact problem between testing device and sample, and a beam model is presented for evaluating the curvatures of gel beams with large elastic deformation. A self-adaptive algorithm is also proposed to search for the best estimation of gels' elastic moduli by comparing the experimental bending curvatures with those computed from the beam model with preestimated moduli. Application to the measurement of the property of polyacrylamide gels indi- cates that the material compliance varies with the concentrations of bis-acrylamide, and the gels become softer after being immersed in a culture medium for a period of time, no matter to what extent they are polymerized. 相似文献
9.
An improved large eddy simulation using a dynamic second-order sub-grid-scale (SGS) stress model has been developed to model
the governing equations of dense turbulent particle-liquid two-phase flows in a rotating coordinate system, and continuity
is conserved by a mass-weighted method to solve the filtered governing equations. In the current second-order SGS model, the
SGS stress is a function of both the resolved strain-rate and rotation-rate tensors, and the model parameters are obtained
from the dimensional consistency and the invariants of the strain-rate and the rotation-rate tensors. In the numerical calculation,
the finite volume method is used to discretize the governing equations with a staggered grid system. The SIMPLEC algorithm
is applied for the solution of the discretized governing equations. Body-fitted coordinates are used to simulate the two-phase
flows in complex geometries. Finally the second-order dynamic SGS model is successfully applied to simulate the dense turbulent
particle-liquid two-phase flows in a centrifugal impeller. The predicted pressure and velocity distributions are in good agreement
with experimental results.
The project supported by the National Natural Science Foundation of China (50779069 and 90510007), the Start-up Scientific
Research Foundation of China Agricultural University (2006021) and the Beijing Natural Science Foundation (3071002). 相似文献
10.
Transfer matrix approach of vibration isolation analysis of periodic composite structure 总被引:1,自引:0,他引:1
Wang Yong Huang Qibai Zhou Minggang Xu Zhisheng 《Archive of Applied Mechanics (Ingenieur Archiv)》2007,77(7):461-471
The transmission properties of elastic waves propagating in a three-dimensional composite structure embedded periodically
with spherical inclusions are analyzed by the transfer matrix method in this paper. Firstly, the periodic composite structures
are divided into many layers, the transfer matrix of monolayer structure is deduced by the wave equations, and the transfer
matrix of the entire structure is obtained in the case of boundary conditions of displacement and stress continuity between
layers. Then, the effective impedance of the structure is analyzed to calculate its reflectivity and transmissivity of vibration
isolation. Finally, numerical simulation is carried out; the experiment results validate the accuracy and feasibility of the
method adopted in the paper and some useful conclusions are obtained.
Project (No. 50075029) supported by the National Natural Science Foundation of China. 相似文献
11.
One of fundamental but difficult problems in damage mechanics is the formulation of the effective constitutive relation of
microcrack-weakened brittle or quasi-brittle materials under complex loading, especially when microcrack interaction is taken
into account. The combination of phenomenological and micromechanical damage mechanics is a promising approach to constructing
an applicable damage model with a firm physical foundation. In this paper, a quasi-micromechanical model is presented for
simulating the constitutive response of microcrack-weakened materials under complex loading. The microcracking damage is characterized
in terms of the orientation domain of microcrack growth (DMG) as well as a scalar microcrack density parameter. The DMG describes
the complex damage and its evolution associated with microcrack growth, while the scalar microcrack density factor defining
the isotropic magnitude of damage yields an easy calculation of the effects of microcrack interaction on effective elastic
moduli.
Project supported by the National Natural Science Foundation of China (19891180). 相似文献
12.
An explicit expression of the effective moduli for composite materials filled with coated inclusions
The obvious shortcoming of the generalized self-consistent method (GSCM) is that the effective shear modulus of composite
materials estimated by the method can not be expressed in an explicit form. This is inconvenient in engineering applications.
In order to overcome that shortcoming of GSCM, a reformation of GSCM is made and a new micromechanical scheme is suggested
in this paper. By means of this new scheme, both the effective bulk and shear moduli of an inclusion-matrix composite material
can be obtained and be expressed in simple explicit forms. A comparison with the existing models and the rigorous Hashin-Shtrikman
bounds demonstrates that the present scheme is accurate. By a two-step homogenization technique from the present new scheme,
the effective moduli of the composite materials with coated spherical inclusions are obtained and can also be expressed in
an explicit form. The comparison with the existing theoretical and experimental results shows that the present solutions are
satisfactory. Moreover, a quantitative comparison of GSCM and the Mori-Tanaka method (MTM) is made based on a unified scheme.
The project supported by the National Natural Science Foundation of China under the Contract NO. 19632030 and 19572008, and
China Postdoctoral Science Foundation 相似文献
13.
BEM for simulation of a 2D elastic body with randomly distributed circular inclusions 总被引:7,自引:0,他引:7
Based on our 2D BEM software THBEM2 which can be applied to the simulation of an elastic body with randomly distributed identical
circular holes, a scheme of BEM for the simulation of elastic bodies with randomly distributed circular inclusions is proposed.
The numerical examples given show that the boundary element method is more accurate and more effective than the finite element
method for such a problem. The scheme presented can also be successfully used to estimate the effective elastic properties
of composite materials.
Project supported by the National Natural Science Foundation of China (No. 19772025). 相似文献
14.
The elastoplastic model in the deviatoric stress space is constructed to describe the cyclic undrained creeping behaviour
of soft clays under cyclic stress by using Mises yield criterion and the concept of a field of hardening moduli. Furthermore,
the effect of model parameters on the deformation is studied, and a method is given to determine quantitatively model parameters
from results of cyclic triaxial tests of the saturated soft clay.
The project supported by National Natural Science Foundation of China and Tianjin Twenty-one Century Youth Science Foundation 相似文献
15.
Mineral bridges of nacre and its effects 总被引:2,自引:1,他引:1
Nacre, or mother-of-pearl, is a kind of composites of aragonite platelets sandwiched between organic materials. Its excellent
mechanical properties are thought to stem from the microarchitecture that is traditionally described as a “brick and mortar”
arrangement. In this paper, a new microstructure, referred to as mineral bridge in the biomineralization, is directly observed
in the organic matrix layers (mortar) of nacre. This is an indication that the organic matrix layer of nacre should be treated
as a three-dimensional interface and the microarchitecture of nacre ought to be considered as a “brick-bridge-mortar” structure
rather than the traditional one. Experiments and analyses show that the mineral bridges not only improve the mechanical properties
of the organic matrix layers but also play an important role in the pattern of the crack extension in nacre.
The project supported by the Natural Science Foundation of Chinese Academy of Sciences (KJ951-1-201) and the National Natural
Science Foundation of China (19891180 and 10072067) 相似文献
16.
Yang Qingsheng 《Acta Mechanica Sinica》1998,14(2):171-178
The paper describes use of self-consistent finite element method (SCFEM) for predicting effective properties of fiber composite
with partially debonded interface. The effective longitudinal Young's modulus and shear modulus for unidirectional fiber reinforced
composites with fiber-end cracks are calculated. Numerical results show that the effective properties are considerably influenced
by the fiber-end cracks. The effects of microstructural parameters, such as fiber volume fraction, modulus ratio of the constituents
and fiber aspect, on the effective properties of the composites were discussed.
The project supported by the National Natural Science Foundation of China 相似文献
17.
Based on the three dimensional elastic theory, the state equation of the axisymmetric free vibration of transversely isotropic
circular plates is established. Taking the advantage of finite Hankel transform, two exact solutions are derived for two boundary
conditions, i. e. the rigid-slipping boundary and elastic simply supported boundary. Finally, numerical results are presented
and compared with those of FEM.
The project is supported by the National Natural Science Foundation of China and the Zhejiang Provincial Natural Science Foundation. 相似文献
18.
Using strain energy-based prediction of effective elastic properties in topology optimization of material microstructures 总被引:1,自引:0,他引:1
Weihong Zhang Gaoming Dai Fengwen Wang Shiping Sun Hicham Bassir 《Acta Mechanica Sinica》2007,23(1):77-89
An alternative strain energy method is proposed for the prediction of effective elastic properties of orthotropic materials
in this paper. The method is implemented in the topology optimization procedure to design cellular solids. A comparative study
is made between the strain energy method and the well-known homogenization method. Numerical results show that both methods
agree well in the numerical prediction and sensitivity analysis of effective elastic tensor when homogeneous boundary conditions
are properly specified. Two dimensional and three dimensional microstructures are optimized for maximum stiffness designs
by combining the proposed method with the dual optimization algorithm of convex programming. Satisfactory results are obtained
for a variety of design cases.
The project supported by the National Natural Science Foundation of China (10372083, 90405016), 973 Program (2006CB601205)
and the Aeronautical Science Foundation (04B53080). The English text was polished by Keren Wang. 相似文献
19.
Analysis of laminated piezoelectric cylindrical shells 总被引:2,自引:0,他引:2
A new method is developed for three-dimensional stress analysis of laminated piezoelectric cylindrical shell with simple support.
The shell can be subjected to various applied loadings, including distributed body force, inner and outer surface traction
and potential. Each layer of the shell can be piezoelectric or elastic/dielectric, with perfect bonding assumed between each
interface. The governing equations are solved by the state-space technique. Numerical results are presented to show the sensing
and actuating effects of three-layered piezoelectric cylindrical shell.
The project supported by the National Natural Science Foundation of China (19572027) 相似文献
20.
Classical micromechanical methods for calculating the effective moduli of a heterogeneous material are generalized to include the interface (surface) effect. By using Hashin‘s Composite Sphere Assemblage (CSA) model, a new expression of the bulk modulus for a particle-reinforced composite is derived. It is emphasized that the present study is within the finite-deformation framework such that the effective properties are not influenced by the interface stress itself solely, but influenced by the change of the interface stress due to changes of the shape and size of the interface, itence some inadequacies in previous papers are pointed out. 相似文献