Accurate simulation of delamination growth under mixed-mode loading using cohesive elements: Definition of interlaminar strengths and elastic stiffness

A methodology for predicting accurately the propagation of delamination under mixed-mode fracture with cohesive elements is proposed. It is shown that changes in the local mode ratio during the evolution of damage under mixed-mode loading can cause errors in the determination of the energy dissipation and result in inaccurate predictions of the global load–displacement response – even under conditions where, according to Linear Elastic Fracture Mechanics, the global mode ratio is constant. To address this difficulty, relations between the interlaminar strengths and the penalty stiffness are proposed which ensure a correct energy dissipation when delamination propagates. The validity of the proposed methodology is demonstrated for different mode ratios by comparison with the corresponding analytical solutions.