Application of the Dugdale model to crazing and fracture in rubber-modified polystyrene

Abstract

The fracture toughness of impact (rubber‐modified) polystyrene can be more adequately described by a strain criterion than by a stress criterion, such as K_IC. Recent work from other laboratories has resulted in several theories which relate plastic‐zone length (craze length), applied stress, and crack‐opening displacement for edge‐notched finite‐width strips pulled in tension. Experimental data on impact polystyrene show that a solution of the problem due to Ashbaugh gives the best representation of crack‐opening displacement as a function of craze length, but with a significant deviation from experiment even so. Within experimental error, fracture initiation occurs at a constant crack‐opening displacement. The applied stress required to generate a given craze length is higher than predicted by the Asbaugh theory for rotatable grips.