Thermodynamic Damage Model for Compositeunder Severe Loading

Abstract

A damage model for a dynamically loaded composite structure under severe loading conditions is presented. The model is based on a thermodynamic micromechanic approach making use of the conservation laws and the first and second laws of thermodynamics. It makes use of an irreversible thermodynamic concept where damage is introduced as an internal variable. The model characterizes micromechanical damages in an average sense where three modes of damage for composites are used: tensile, shear, and interphase damage. A homogenization or an averaging technique is implemented to simplify the representation of the nonhomogeneous material. The composite materials are modeled as being inelastic where the Maxwell viscoelastic constitutive relation is incorporated. The initiation of microcracks in the continuum is predicted based on a dissipation function. The coalescing of these microcracks and the onset of macrocracks is modeled where the macrocracks are assumed to initiate when the computed power of dissipation reaches a critical value. Verification analysis and numerical results to demonstrate the model's damage characteristics are also presented.