The mechanism of brittle fracture in notched impact tests on polycarbonate
- Cite this article as:
- Mills, N.J. J Mater Sci (1976) 11: 363. doi:10.1007/BF00551448
The impact testing of notched polycarbonate bars that are thick enough to yield in plane strain has been investigated. Shear bands occur in the plastic zone that resemble the slip line field for yielding from a circular notch. Eventually, an internal craze nucleates at the tip of the plastic zone, where the stresses are highest, and a crack forms in the thickest part of the craze. Above −15‡ C the stress for the craze to nucleate is a nearly constant multiple of the yield stress. It is shown that previous observations that annealing polycarbonate causes a ductile to brittle transition is a consequence of testing bars of thickness less than 5 mm.