Micromechanisms of crack initiation in thin films and thick sections of polyethylene

Abstract

The morphology of the micro-deformation and fracture processes that occur in the neighbourhood of a notch prior to macroscopic crack growth were determined by a variety of microscopic techniques. The first micro-event that was observed in all instances was the formation of crack-like pores. The shape of the porous zone could not be deduced from existing yield criteria. In thick sections the porous zone transformed to a fibrillated region and in thin films the porous zone tends to transform into a continuous oriented zone. Fibril fracture consisted of a slow process of thinning by shear followed by a rapid rupture. The above micro-events precede macroscopic crack growth in polyethylene.