K. Lee¹, H. Park², S.W. Lee³

CMES-Computer Modeling in Engineering & Sciences, Vol.32, No.3, pp. 113-122, 2008, DOI:10.3970/cmes.2008.032.113

Abstract A post-processing scheme is presented to accurately determine transverse shear and normal stresses in composite panels undergoing geometrically nonlinear deformation under dynamic loading conditions. Transverse stresses are assumed through thickness at a point of interest and are recovered via a one-dimensional finite element method. The finite element method is based on the least square functional of the error in the equilibrium equation along the thickness direction and utilizes the in-plane stresses and resultant transverse shear forces per unit length obtained by a shell element analysis. Numerical results demonstrate that, with minimal addition of computational efforts, the present post-processing approach can… More >

H. T. Wang¹, Z. H. Yao²

CMES-Computer Modeling in Engineering & Sciences, Vol.29, No.1, pp. 1-14, 2008, DOI:10.3970/cmes.2008.029.001

Abstract Carbon nanotubes (CNTs) may provide ultimate enhancement in stiffness and strength for composite materials. This paper presents a rigid-fiber-based boundary integral equation formulation for the numerical simulation of debonding process and the corresponding strength of CNT reinforced composites. The CNT/matrix interfaces are assumed to fail when the interfacial shear force reaches a prescribed threshold, and the CNTs and matrix are considered to be detached in the failed areas. The matrix with one or several tens of originally well-bonded CNTs is subjected to an incremental tensile load and the effective stress-strain relations are readily obtained by the introduction of CNT/matrix debonding… More >

Vadiraja D. N.¹, A. D. Sahasrabudhe²

CMES-Computer Modeling in Engineering & Sciences, Vol.27, No.1&2, pp. 49-62, 2008, DOI:10.3970/cmes.2008.027.049

Abstract Rotating beams are flexible structures, which are often idealized as cantilever beams. Structural modelling of rotating thin-walled composite beam with embedded MFC actuators and sensors using higher shear deformation theory (HSDT) is presented. A non-Cartesian deformation variable (which represents arc length stretch) is used along with two Cartesian deformation variables. The governing system of equations is derived from Hamilton's principle and solution is obtained by extended Galerkin's method. Optimal control problem is solved using LQG control algorithm. Vibration characteristics and optimal control for a box beam configuration are discussed in numerical examples. Gyroscopic coupling between lagging-extension motions is found to… More >

Thi D. Dang¹, Bhavani V. Sankar²

CMES-Computer Modeling in Engineering & Sciences, Vol.26, No.3, pp. 169-188, 2008, DOI:10.3970/cmes.2008.026.169

Abstract In this paper the meshless local Petrov-Galerkin (MLPG) method is used in the micromechanical analysis of a unidirectional fiber composite. The methods have been extended to include shear loadings, thus permitting a more complete micromechanical analysis of the composite subjected to combined loading states. The MLPG formulation is presented for the analysis of the representative volume element (RVE) of the periodic composite containing material discontinuities. Periodic boundary conditions are imposed between opposite faces of the RVE. The treatment of periodic boundary conditions in the MLPG method is handled by using the multipoint constraint technique. Examples are presented to illustrate the… More >

S. D. Harris¹, R. Mustata², L. Elliott², D. B. Ingham², D. Lesnic²

CMES-Computer Modeling in Engineering & Sciences, Vol.25, No.2, pp. 69-80, 2008, DOI:10.3970/cmes.2008.025.069

Abstract Two homogeneous anisotropic materials are butted together to form a contact surface within a single composite material (the specimen). An inverse boundary element method (BEM) is developed to determine the components of the hydraulic conductivity tensor of each material and the position of the contact surface. A steady state flow is forced through the specimen by the application of a constant pressure differential on its opposite faces. Experimental measurements (simulated) of pressure and average hydraulic flux at exposed boundaries are then used in a modified least squares functional. This functional minimises the gap between the above measured (simulated) values and… More >

Weixue Tian¹, Ronggui Yang²

CMES-Computer Modeling in Engineering & Sciences, Vol.24, No.2&3, pp. 123-142, 2008, DOI:10.3970/cmes.2008.024.123

Abstract In this paper, we investigated the effective thermal conductivity of three dimensional nanocomposites composed of randomly distributed binary nanoparticles with large differences (contrast ratio) in their intrinsic (bulk) thermal conductivity. When random composites are made from particles with very different thermal conductivity (large contrast ratio), a continuous phase of high thermal conductivity constituent is formed when its volumetric concentration reaches beyond the percolation threshold. Such a continuous phase of material can provide a potentially low resistance pathway for thermal transport in random composites. The percolation theory predicts the thermal conductivity of the random composites to increase according to a scaling… More >

F.C. Araújo¹, L.J. Gray²

CMES-Computer Modeling in Engineering & Sciences, Vol.24, No.2&3, pp. 103-122, 2008, DOI:10.3970/cmes.2008.024.103

Abstract In recent years, carbon nanotubes (CNTs) have been widely employed to build advanced composites. In this work, a Boundary Element Method (BEM) is applied to 3D representative volume elements (RVEs) to estimate mechanical properties of CNT-based composites. To model the thin-walled nanotubes, special integration procedures for calculating nearly-strongly-singular integrals have been developed. The generic BE substructuring algorithm allows modeling complex CNT-reinforced polymers, containing any number of nanotubes of any shape (straight or curved). The subregion-by-subregion strategy, based on Krylov solvers, makes the independent generation, assembly, and storage of the many parts of the complete BE model possible. Thus, significant memory… More >

B. Yang^1,2, S.-C. Wong³, S. Qu³

CMES-Computer Modeling in Engineering & Sciences, Vol.24, No.2&3, pp. 81-94, 2008, DOI:10.3970/cmes.2008.024.081

Abstract In the modeling of overall property of composites, the effect of particle interaction has been either numerically taken into account within a (representative) volume element of a small number of particles or neglected/ignored in order for efficient solution to a large system of particles. In this study, we apply the point-defect Green's function (GF) to take into account the effect of particle interaction. It is applicable to small volume fractions of particles (within 10 %). The high efficiency of the method enables a simulation of a large system of particles with generally elastic anisotropy, arbitrary shape and composition, and arbitrary… More >

A.P.S. Selvadurai¹, H. Ghiabi²

CMES-Computer Modeling in Engineering & Sciences, Vol.23, No.1, pp. 53-74, 2008, DOI:10.3970/cmes.2008.023.053

Abstract This paper deals with the problem of the consolidation of a composite consisting of alternate layers of soft clay and a granular material. A series of experiments were conducted on components to develop the constitutive models that can be implemented in a computational approach. The constitutive response of the soft clay is represented by a poro-elasto-plastic Cam clay-based model and the granular medium by an elasto-plastic model with a Drucker-Prager type failure criterion and a non-associated flow rule. The computational poro-elasto-plastic model is used to calibrate the experimental results derived from the one-dimensional tests and to establish the influence of… More >

S. Namilae¹, U. Ch,ra², A Srinivasan³, N. Ch,ra⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.3, pp. 189-202, 2007, DOI:10.3970/cmes.2007.022.189

Abstract Molecular dynamics (MD) simulations play an important predictive role in understanding the behavior of nanoscale systems. In this paper, parallel MD simulations are used to understand the mechanical behavior of interfaces in CNT based composites. We present an algorithm for parallel implementation of MD simulations of carbon nanotube (CNT) based systems using reactive bond order potentials. We then use that algorithm to model the CNT-polymer interfaces with various levels of interaction as (a) described only by long range Van Der Waals interactions (b) chemically bonded with fixed matrix and (c) chemically bonded with matrix explicitly modeled. It is shown that… More >