Standard

This paper presents an anisotropic damage model suitable for predicting failure and post-failure behavior in fiber-reinforced materials. In the model the plane stress formulation is used and the response of the undamaged material is assumed to be linearly elastic. The model is intended to predict behavior of elastic-brittle materials that show no significant plastic deformation before failure. In the model four different failure modes-- fiber tension, fiber compression, matrix tension, and matrix compression-- are considered and modeled separately. The onset of damage is predicted using Hashin's initiation criteria [I], which are expressed in terms of effective stresses. Once the damage process starts, it is assumed that its effect can be taken into account by modifying the stiffness coefficients. In this model, we adapt the formulation of Matzenrniller et al. [2]. In this formulation the damage is simulated by four internal variables (a different variable is used for each failure mode). An important characteristic of the formulation is that the thermodynamic forces are always positive. Therefore to assure positive dissipation during the damage process it is sufficient to require that the damage variables either remain constant or increase their values. To describe the evolution of the damage variables we use a law that is a generalization of that proposed by Camanho and Davila [3] for cohesive elements. The evolution law is based on energy dissipation during the damage process, whic