Experimental study on stable growth of crack and craze damage in HIPS under tension at room temperature

This study focuses on investigating the stable damage and crack growth proc ess of high impact polystyrene (HIPS) by using the damage mechanics approac h and the moire method. Under excessive tensile loading, HIPS will be damag ed due to multiple crazing that causes volume dilatation. A damage variable is defined by the dilatation of the representative volume element to chara cterize the craze-damage. The relationship between the dilatation and the t otal strain has been determined experimentally. A specimen with a sharp ini tial discontinuity is tested under tensile force to study the damage and cr ack growth process. It is observed that an elliptical damage zone is formed in front of the crack tip. The crack propagation is stabilized by the dama ge zone. Moire fringe patterns show that the deformation within the damage zone is non-uniform. A dynamic configuration of deformation, which comprise s the elastic zone, the transition zone, the damage processing zone, and th e residual damage zone, has been established. The non-linear strain and str ess fields inside the transition zone and the damage processing zone are an alyzed. The experimental result also shows that a critical plastic strain c riterion may be used to predict the stable growth of macrocracks for HIPS. (C) 2001 Elsevier Science Ltd. All rights reserved.