A modified mode I cohesive zone model for the delamination growth in DCB laminates with the effect of fiber bridging

Fiber bridging has a significant influence on the delamination propagation behavior in multidirectional composite laminates. Traditional pure mode I bilinear cohesive zone models (CZM) do not consider the effect of fiber bridging and result in an inaccurate simulation on the delamination behavior. This study proposed a physical-based three-linear CZM superposed by two bilinear CZMs, which represent two different phenomena including the quasi-brittle matrix fracture characterized by a higher peak stress and a shorter critical opening displacement, and the fiber bridging characterized by a lower peak stress and a longer critical opening displacement, respectively. The three-linear CZM was implemented in the commercial FE software using a user-subroutine UMAT. Double Cantilever Beam (DCB) tests on the multidirectional composite laminates with 0 degrees/5 degrees and 45 degrees/- 45 degrees interfaces conducted in our previous studies are shown to have large-scale fiber bridging in mode I delamination and are used to provide experimental data for calibrating the new CZM. Good agreements between the predicted and tested results can be achieved by adopting this new CZM, demonstrating its applicability on predicting the mode I delamination behavior in composite laminates with the effect of fiber bridging.