Caustics observations for a study of environmental crack-craze stress fields

The method of caustics is applied to a study of the environmental crack-craze stress field in polymethylmethacrylate during craze growth in methanol and later during a drying procedure in air. In the presence of methanol non-uniform stress with a maximum level at the craze tip was observed. The concept of a "critical equivalent stress intensity factor" below which no craze growth occurs in liquid is defined. During the drying procedure the location of the maximum stress shifted dramatically from the craze tip to the crack tip.