Isa Ahmadi¹, M.M. Aghdam²

CMES-Computer Modeling in Engineering & Sciences, Vol.108, No.1, pp. 21-48, 2015, DOI:10.3970/cmes.2015.108.021

Abstract In this study, a truly meshless method based on the meshless local Petrov-Galerkin method is formulated for analysis of the elastic-plastic behavior of heterogeneous solid materials. The incremental theory of plasticity is employed for modeling the nonlinearity of the material behavior due to plastic strains. The well-known Prandtl-Reuss flow rule of plasticity is used as the constitutive equation of the material. In the presented method, the computational cost is reduced due to elimination of the domain integration from the formulation. As a practical example, the presented elastic-plastic meshless formulation is employed for micromechanical analysis of More >

X. Wang¹, W.T. Ang^1,2, H. Fan¹

CMES-Computer Modeling in Engineering & Sciences, Vol.107, No.2, pp. 81-101, 2015, DOI:10.3970/cmes.2015.107.081

Abstract A micromechanical model is proposed here for estimating the effective stiffness of a pair of parallel microscopically damaged interfaces in a trimaterial under inplane elastostatic deformations. The trimaterial is made of an orthotropic thin layer sandwiched between two orthotropic half-spaces. The microscopically damaged interfaces are modeled using periodically distributed interfacial micro-cracks. The micromechanical model is formulated and numerically solved in terms of hypersingular boundary integro-differential equations. The effects of the width of the thin layer, the micro-crack densities of the two interfaces and the material constants of the thin layer and the two half-spaces on More >

B.J. Yang¹, K.J. Cho¹, G.M. Kim¹, H.K. Lee^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.103, No.5, pp. 343-365, 2014, DOI:10.3970/cmes.2014.103.343

Abstract The addition of carbon nanotubes (CNTs) to a matrix material is expected to lead to an increase in the effective electrical properties of nanocomposites. However, a CNT entanglement caused by the matrix viscosity and the high aspect ratio of the nanotubes often inhibits the formation of a conductive network. In the present study, the micromechanics-based model is utilized to investigate the effect of CNT agglomeration on the electrical conductivity and percolation threshold of nanocomposites. A series of parametric studies considering various shapes and curviness distributions of CNTs are carried out to examine the effects of More >

L. Rodríguez-Tembleque¹, M.H. Aliabadi²

CMES-Computer Modeling in Engineering & Sciences, Vol.102, No.3, pp. 183-210, 2014, DOI:10.3970/cmes.2014.102.183

Abstract This work presents new contact constitutive laws for friction and wear modelling in fiber-reinforced plastics (FRP). These laws are incorporated to a numerical methodology which allows us to solve the contact problem taking into account the anisotropic tribological properties on the interfaces. This formulation uses the Boundary Element Method for computing the elastic influence coefficients. Furthermore, the formulation considers micromechanical models for FRP that also makes it possible to take into account the fiber orientation relative to the sliding direction, the fiber volume fraction, the aspect ratio of fibers, or the fiber arrangement. The proposed More >

Qiubao Ouyang¹, Di Zhang^1,2, Xinhai Zhu³, Zhidong Han³

CMC-Computers, Materials & Continua, Vol.41, No.1, pp. 37-54, 2014, DOI:10.3970/cmc.2014.041.037

Abstract The present work is to investigate the failure mechanisms in the deformation of silicon carbide (SiC) particle reinforced aluminum Metal Matrix Composites (MMCs). To better deal with crack growth, a new numerical approach: the MLPG-Eshelby Method is used. This approach is based on the meshless local weak-forms of the Noether/Eshelby Energy Conservation Laws and it achieves a faster convergent rate and is of good accuracy. In addition, it is much easier for this method to allow material to separate in the material fracture processes, comparing to the conventional popular FEM based method. Based on a… More >

L.B. Borkowski¹, K.C. Liu¹, A. Chattopadhyay¹

CMC-Computers, Materials & Continua, Vol.37, No.3, pp. 161-193, 2013, DOI:10.3970/cmc.2013.037.161

Abstract The microstructural variation in fiber-reinforced composites has a direct relationship with its local and global mechanical performance. When micromechanical modeling techniques for unidirectional composites assume a uniform and periodic arrangement of fibers, the bounds and validity of this assumption must be quantified. The goal of this research is to quantify the influence of microstructural randomness on effective homogeneous response and local inelastic behavior. The results indicate that microstructural progression from ordered to disordered decreases the tensile modulus by 5%, increases the shear modulus by 10%, and substantially increases the magnitude of local inelastic fields. The More >

K. C. Liu¹, S. M. Arnold²

CMC-Computers, Materials & Continua, Vol.35, No.1, pp. 35-65, 2013, DOI:10.3970/cmc.2013.035.035

Abstract It is well known that failure of a material is a locally driven event. In the case of ceramic matrix composites (CMCs), significant variations in the microstructure of the composite exist and their significance on both deformation and life response need to be assessed. Examples of these variations include changes in the fiber tow shape, tow shifting/nesting and voids within and between tows. In the present work, the influence of many of these scale specific architectural features of woven ceramic composite are examined stochastically at both the macroscale (woven repeating unit cell (RUC)) and structural More >

K.W. Luczynski¹, A. Dejaco¹, O. Lahayne¹, J. Jaroszewicz², W.Swieszkowski², C. Hellmich¹

CMES-Computer Modeling in Engineering & Sciences, Vol.87, No.6, pp. 505-529, 2012, DOI:10.3970/cmes.2012.087.505

Abstract A 71 volume-% macroporous tissue engineering scaffold made of poly-l-lactide (PLLA) with 10 mass-% of pseudo-spherical tri-calcium phosphate (TCP) inclusions (exhibiting diameters in the range of several nanometers) was microCT-scanned. The corresponding stack of images was converted into regular Finite Element (FE) models consisting of around 100,000 to 1,000,000 finite elements. Therefore, the attenuation-related, voxel-specific grey values were converted into TCP-contents, and the latter, together with nanoindentation tests,entered a homogenization scheme of the Mori-Tanaka type, as to deliver voxel-specific (and hence, finite element-specific) elastic properties. These FE models were uniaxially loaded, giving access to the… More >

Lianhua Ma¹, Bernard F. Rolfe², Qingsheng Yang^1,3, Chunhui Yang^2,3

CMES-Computer Modeling in Engineering & Sciences, Vol.79, No.2, pp. 131-158, 2011, DOI:10.3970/cmes.2011.079.131

Abstract For fluid-filled closed cell composites widely distributed in nature, the configuration evolution and effective elastic properties are investigated using a micromechanical model and a multiscale homogenization theory, in which the effect of initial fluid pressure is considered. Based on the configuration evolution of the composite, we present a novel micromechanics model to examine the interactions between the initial fluid pressure and the macroscopic elasticity of the material. In this model, the initial fluid pressure of the closed cells and the corresponding configuration can be produced by applying an eigenstrain at the introduced fictitious stress-free configuration,… More >

L. Dong¹, S. N. Atluri²

CMC-Computers, Materials & Continua, Vol.24, No.1, pp. 61-104, 2011, DOI:10.3970/cmc.2011.024.061

Abstract A simple procedure to formulate efficient and stable hybrid/mixed finite elements is developed, for applications in macro- as well as micromechanics. In this method, the strain and displacement field are independently assumed. Instead of using two-field variational principles to enforce both equilibrium and compatibility conditions in a variational sense, the independently assumed element strains are related to the strains derived from the independently assumed element displacements, at a finite number of collocation points within the element. The element stiffness matrix is therefore derived, by simply using the principle of minimum potential energy. Taking the four-node… More >