Résumé
This paper presents a cohesive zone model (CZM) in which a scalar state variable characterizing damage evolution is used to depict an anisotropic degradation of elastic properties.The proposed model extends a previous modelling work where the damage criterion was based on the energy balance form associated with cohesive zone degradation and particularly on the evolution of the maximum elastic energy that can be stored for a given damage state. This extended model allows the description of various interactions between normal and tangential stiffness degradation. This model relies on a single scalar damage variable combined with an energy-based formulation to capture various types of coupling between normal and tangential damage mechanisms. The model's capabilities and limitations to consider different normal and tangential separation curve are then illustrated through a few simulations. Following in the footsteps of Rice and Willis, the paper then compares the local CZ approach to damage and the mechanics of brittle fracture, which introduces the concept of energy release rate proposed by Griffith.
For this purpose, various numerical bending tests inspired by conventional tests (DCB, ENF, MMB) are performed by adjusting several parameters re-lated to the normal and tangential characteristics of the CZ. When a stable propagation of the crack is observed, the energy released rate, estimated macroscopically via an area method, is compared with the dissipated energy developed by the CZs.