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 the unidirectional composite material. A… 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 entanglement on the electrical performance… 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 contact and wear laws, as… More >

F.C. de Araújo^1,2, C. R. da Silva Jr.¹, M. J. Hillesheim¹

CMES-Computer Modeling in Engineering & Sciences, Vol.96, No.3, pp. 185-198, 2013, DOI:10.3970/cmes.2013.096.185

Abstract In this paper, the BE SBS (subregion-by-subregion) algorithm, a generic substructuring technique for the BEM, is applied to evaluate stresses at boundary and interfacial points of general 3D composites and solids. At inner points, regular boundary integration schemes may be employed. For boundary or interfacial points, the Hooke’s law along with global-to-local axis-rotation transformations is directly applied. In fact, in thin-walled domain parts, only boundary stresses are needed. As the SBS algorithm allows the consideration of a generic number of subregions, the technique applies to the stress analysis in any composite and solid, including the microstructural (grain-by-grain) modeling of materials.… More >

L. Rodríguez-Tembleque¹, A. Sáez¹, F.C. Buroni¹

CMES-Computer Modeling in Engineering & Sciences, Vol.96, No.2, pp. 131-158, 2013, DOI:10.3970/cmes.2013.096.131

Abstract A boundary element based formulation is applied to study numerically the tribological behavior of fiber-reinforced plastics (FRP) under different frictional contact conditions, taking into account the micromechanics of FRP. Micromechanical models presented consider continuous and short fiber reinforced plastics configurations. The Boundary Element Method (BEM) with an explicit approach for fundamental solutions evaluation is considered for computing the elastic influence coefficients. Signorini’s contact conditions and an orthotropic law of friction on the potential contact zone are enforced by contact operators over the augmented Lagrangian. The proposed methodology is applied to study carbon FRP under frictional contact. The obtained numerical results… More >

Seyed Mahmoud Hosseini ¹

CMES-Computer Modeling in Engineering & Sciences, Vol.95, No.1, pp. 1-29, 2013, DOI:10.3970/cmes.2013.095.001

Abstract In this article, the effects of carbon nanotubes distributions on natural frequency are studied for a functionally graded nanocomposite thick hollow cylinder reinforced by single-walled carbon nanotubes using a hybrid mesh-free method. The FG nanocomposite cylinder is excited by a shock loading, which is applied on the inner surface of cylinder. The first natural frequency is obtained for various nonlinear grading patterns of distributions of the aligned carbon nanotubes. The effects of various nonlinear grading patterns on natural frequency are obtained and discussed in details. The presented hybrid mesh-free method is based on the generalized finite difference (GFD) method for… More >

Yaochan Zhu¹, Eckart Schnack¹, Al Mahmudur Rahman¹

CMES-Computer Modeling in Engineering & Sciences, Vol.92, No.3, pp. 315-326, 2013, DOI:10.32604/cmes.2013.092.315

Abstract A novel multiphase field model is formulated to simulate the complex microstructure evolution during chemical vapor infiltration (CVI) process, which is widely used technique to produce SiC matrix composites reinforced by SiC fibers in ceramic engineer. The model consists of a set of nonlinear partial differential equations by coupling Ginzburg-Landau type phase field equations with mass/heat balance equations as well as modified Navier-Stokes equations. The microstructure evolution of preferential codeposition of Si, SiC and C under high ratio of H2 to MTS is simulated. The simulation is in good agreement with experiments result. The potential risk of blockage of the… More >

J. A. Nairn¹

CMES-Computer Modeling in Engineering & Sciences, Vol.92, No.3, pp. 271-299, 2013, DOI:10.32604/cmes.2013.092.271

Abstract The “multimaterial” version of the material point method (MPM) extrapolates each material to its own velocity field on a background grid. By reconciling momenta on nodes interacting with two or more materials, MPM is able to automatically handle contact without any need for special contact elements. This paper extends multimaterial MPM to automatically handle imperfect interfaces between materials as well. The approach is to evaluate displacement discontinuity on multimaterial nodes and then add internal forces and interfacial energy determined by an imperfect interface traction law. The concept is simple, but implementation required numerous corrections to make the analysis mesh independent,… More >

J. Wang¹, E. Andres, P. Simacek, S.G.Advani

CMES-Computer Modeling in Engineering & Sciences, Vol.88, No.3, pp. 155-182, 2012, DOI:10.3970/cmes.2012.088.155

Abstract In Liquid Composite Molding (LCM) processes, the process design requires an infusion and venting scheme which will saturate all the empty spaces between the fibers during mold filling resulting in a composite part without voids. However, the inherent material and process variability can change the filling patterns significantly which complicate this task. The objective of this work is to develop methodologies and tools to automate infusion process design and integrate it within the CAD design environment. The methodologies and algorithms developed examine the designed part geometry and material layups for ease of manufacturing with feasible infusion schemes by accounting for… More >

R. Khanna^1,2, D. R. Katti¹, K. S. Katti¹

CMES-Computer Modeling in Engineering & Sciences, Vol.87, No.6, pp. 530-556, 2012, DOI:10.3970/cmes.2012.087.530

Abstract Here we report a new in situ nanoindentation technique developed to evaluate the composite mechanical behavior of cell-biomaterial construct under physiological conditions over the time scale of bone nodule generation. Using this technique, mechanical behavior of osteoblast cell-substrate interfaces on tissue engineered materials (chitosan-polygalacturonic acid-nanohydroxyapatite (CPH) films) is investigated. Mechanical behavior of cells in the elastic regime over the time scale of cell adhesion (1 day), proliferation (4 days), development (8 days) and maturation (22 days) of bone nodules is evaluated. Our results indicate that the elastic properties of flat cells are higher (indicating stiffer response, after 4 days, as… More >