THE CRAZE-TIP DEFORMATION ZONE IN PC SAN MICROLAYER COMPOSITES/

Crazing in styrene-acrylonitrile copolymer (SAN) layers of polycarbona te (PC) / SAN microlayer composites and the deformation zone that form ed in the PC layer in response to the stress concentration created at the PC/SAN interface by the craze tip were examined by optical and sca nning electron microscopy. A 49-layer composite with relatively thick layers, on the size scale of tens of microns, was chosen in order to c onfine interactions to the region of a single PC/SAN interface. The SA N craze density, which increased with applied stress, was shown to fit the Weibull distribution function. The distance between crazes was de scribed by a correlation length, and the distribution of correlation l engths indicated that crazing occurred randomly in the SAN layers. In the PC layer, the craze-tip deformation zone consisted of a colinear p lastic zone together with a pair of micro-shearbands that grew away fr om the craze tip at an angle of about 45-degrees. Assuming a blunted c raze tip, the plastic zone was analyzed using the slip-line field theo ry. The dependence of the micro-shearband length on remote stress was similar to that predicted by both the BCS and Vitek models. (C) 1994 J ohn Wiley & Sons, Inc.