We propose a new model of brittle damage for initially orthotropic materials. The proposed strain energy-based formulation allows to account for the interaction between initial and induced anisotropies and to address the very challenging issue of opening-closure effects (unilateral behaviour). In order to derive the complete model including the damage growth, we take advantage of micromechanical developments suitably combined with the thermodynamics framework of the standard generalized materials. The model has been implemented within the finite-element code ABAQUS and various numerical simulations have been carried out to illustrate its predictive capabilities. In particular, emphasis is put on the evolution of the material symmetry and the influence of microcracks opening-closure states on the damage process
