Thermomechanical properties and stress analysis of 3-D textile composites by asymptotic expansion homogenization method

This paper formulates asymptotic expansion homogenization method for the analysis of 3-D composites whereby thermomechanical effects are considered. The equivalent thermomechanical properties, viz. elastic constants and coefficient of thermal expansion, of 3-D orthogonal interlock composites are obtained based on a unit-cell derived from the optical microscopy observation. The Young's modulus and Poisson's ratio obtained from the analysis are compared with those obtained by experiments. The results show a good agreement especially for the Young's modulus. Localization analysis based on the present formulation is also presented to assess the stresses within the constituents of 3-D composites (fiber tows and resin region) due to mechanical loading and temperature difference. In order to facilitate the localization analysis, the unit-cell of 3-D composites is first subjected to temperature difference in order to obtain thermal residual stresses. Subsequently, a beam model utilizing homogenized thermomechanical properties of 3-D composites is built to obtain stresses due to mechanical loading. Two loading cases are considered: beam under uniaxial tension (Case I) and beam under bending load (Case 2). The thermal residual stresses and stresses due to mechanical loading in each case are then superposed to obtain total stresses. The total stresses are then used to understand the complete response of composite constituents under mechanical and thermal loadings. (C) 2013 Elsevier Ltd. All rights reserved.