Damage evolution in laminated polymer matrix composites containing a cohesive zone

Close examination of the delaminated surfaces of laminated polymeric composites will often reveal the presence of a process zone ahead of the advancing delamination. In thermosetting polymeric matrices, the process zone will most likely contain micro-shear cracks. Their presence can introduce nonlinearities to the response of the interface and thus affect the growth of the delamination. The evolution of delaminations containing this type of process zone is examined. The formation of the process zone is modeled via a non-linear interfacial constitutive relationship that is based on a micro-mechanics solution for distributed non-interacting cracks. The mechanical characteristics of the interface constitutive relationship are examined. In addition, the delamination behavior of laminates possessing this type of interfacial response and subjected to simulated low velocity impact condition is investigated. These results are compared with experimental measurements.