Cohesive Model for the Simulation of Crack Initiation and Propagation in Mixed-Mode I/II in Composite Materials

A cohesive element able to connect and simulate crack growth between independently modeled finite element subdomains with non-matching meshes is proposed and validated. The approach is based on penalty constraints and has several advantages over conventional FE techniques in disconnecting two regions of a model during crack growth. The most important is the ability to release portion of the interface that are smaller than the local finite element length. Thus, the growth of delamination is not limited to advancing by releasing nodes of the FE model, which is a limitation common to the methods found in the literature. Furthermore, it is possible to vary the penalty parameter within the cohesive element, allowing to apply the damage model to a chosen fraction of the interface between the two meshes. A novel approach for modeling the crack growth in mixed mode I+II conditions has been developed. This formulation leads to a very efficient computational approach that is completely compatible with existing commercial software. In order to investigate the accuracy and to validate the proposed methodology, the growth of the delamination is simulated for the DCB, ENF and MMB tests and the results are compared with the experimental data.