Fracture simulation for anisotropic materials using a virtual internal bond model

A virtual internal bond (VIB) model for isotropic materials has been recently proposed to describe material deformation and fracture under static and dynamic loading situations. Fracture simulation using an isotropic VIB model, is made possible by incorporating a cohesive type law, inspired by atomistic-level interaction among particles into a hyper-elastic framework at the continuum level. Thus, fracture is built directly into the constitutive formulation. The numerical implementation of the model into a finite element scheme and the determination of model material parameters was described in detail in [Eng. Fract. Mech. 71 (2004) 401]. In this paper, the isotropic model is extended for the fracture simulation of anisotropic materials. This is done by introducing a bond density function at the atomistic level, that can model a variety of anisotropic materials. The bond density function is modeled by spherical harmonics expansions. The derived anisotropic model is implemented as a material model subroutine in ABAQUS and used to perform fracture simulations in anisotropic materials. Simulations and results of comparisons with the isotropic model are presented in this paper. (C) 2004 Elsevier Ltd. All rights reserved.