Solvent stress crazing in PMMA: 1. Geometrical effects

Abstract Single crazes were propagated in poly(methyl methacrylate) (PMMA) by loading sheet specimens containing ‘starter’ cracks and immersed in various alcohols. Craze lengths and propagation velocities were measured (as functions of the applied load) using an ultrasonic scanning technique, for three types of behaviour. These were: (I) where craze arrest occurs after some growth; (II) where the craze grows at a constant velocity for an unlimited distance; and (III) where constant velocity growth continues after removal of the original ‘starter’ crack and re-application of the load. The results are analysed using the concept of an ‘equivalent crack’, whose length I turns out to be related to the length c 0 of the starter crack. At temperatures above a previously identified ‘characteristic temperature’, I is commensurate with c 0 , but at lower temperatures, I ⪡ c 0 . These results are discussed in terms of the strain hardening properties of the craze matter which fills the craze.