Prediction of a complex delamination front using a general cohesive model

The influence of the delamination direction with respect to the fiber orientation in adjacent plies on the apparent interlaminar toughness is considered by proposing a general cohesive model. A local delamination-direction definition method is adopted. Based on the mismatch between the fiber orientation and delamination direction, the linear evolution of the apparent toughness is developed. The general cohesive model is implemented in a user-defined element subroutine in ABAQUS and is validated on a case study with a single cohesive element. Second, a square sample under Mode I fractures is designed, where multiple delamination directions, ranging from 0° to 90°, form a complex delamination front. Nonlocal crack branching can be observed where high-delamination direction angles exist. Using the segmented linear evolution of toughness can significantly improve the accuracy of predicting the delamination fronts and the reaction-force-opening curve. This work provides a framework to assess the intra/interlaminar damage coupling during the multidirectional delamination propagation.