Finite element analyses of shear yielding and crazing in glassy polymers under cyclic mode I loading

A simple and yet physically motivated continuum-micromechanical model for crazing is developed, focussing on cyclic loading. The model features fibril drawing and fibril creep deformation, loose hanging fibrils upon unloading and the morphology change fibrils undergo between craze initiation up to a fully developed craze. The crazing model is implemented in a user material subroutine in the commercial finite element programme ABAQUS. The performance is investigated on a mode I crack growth boundary value problem under cyclic loading. Experimentally measured craze/crack opening profiles from the literature are reasonably-well captured by the model. The results exhibit further interesting model characteristics, such as a variation of the craze length in the course of a load cycle.