A strain-rate dependent 3-D micromechanical model for finite element simulations of plain weave composite structures

A new 3-D constitutive model is developed for finite element simulations of plain weave composites (PWC) structures and implemented in the explicit finite element software DYNA3D. The aim of this work is to develop a material model for PWC which incorporates their significant deformation characteristics like strain rate sensitivity, progressive failure phenomena, and nonlinearity in shear and yet is computationally efficient. The constitutive relations are obtained using micromechanical analysis of a simple representative unit cell developed earlier in [1] to predict the mechanical properties of PWC. The matrix is modeled as a viscoplastic strain-rate dependent material, thereby incorporating strain-rate sensitivity in the composite model. Nonlinearity in shear is modeled using an explicit strain dependent relation for shear moduli of the constituents. A set of strain based failure criteria and corresponding stiffness degradations is used to model the progressive failure behavior. The constituents are checked for various modes of failure at each time step and if found to have failed, their moduli are reduced based on the mode. Only fiber breakage is assumed as ultimate failure of the composite. Initially, the yarns and the matrix are assumed to be transversely isotropic and isotropic materials respectively. They become orthotropic with the advent of initial failure. Experimental results available in the literature are used to verify the model’s predictions.