Modelling distinct failure mechanisms in composite materials by a combined phase field method

A numerical computational framework that combines a phase field model (PFM) and cohesive element (CE) for modelling progressive failure in composite material is proposed. In this setting, cracks in single material and the interface are captured separately by using the PFM and CE. A unified PFM that incorporates general cohesive softening laws is adopted for quasi-brittle fracture process. An energy split scheme is used to prevent material cracking under compressive state. The irreversibility of the damage evolution is enforced by introducing a history related energy density. The compatibility issue between the CE and PFM is considered for accurately capturing complicated failure mechanisms in composite. The developed approach is implemented into commercial software ABAQUS through user-defined subroutine element (UEL). Validation is made by modelling an experiment on delamination migration of a cross ply composite. Failure mechanisms including delamination, matrix crack, and location of delamination migration that observed in the experiment are all well captured. Moreover, the importance of considering the compatibility between CE and other numerical methods is discussed through a complementary modelling.