MECHANISM OF DELAMINATION IN MICROLAYER C OMPOSITES OF POLYCARBONATE AND STYRENE-ACRYLONITRILE COPOLYMER

The mechanism of delamination in polymer composite composed of 194 alt ernating layers of plastic polycarbonate and more brittle styrene-acry lonitrile copolymer was studied by means of dual-cantilever bending. D elamination was shown to posses a cohesive character, and a crack was shown to propagate through crazes in the layers of styrene-acrylonitri le copolymer. Two slightly different mechanisms of delamination were o bserved. The first mechanism is associated with crack propagation with in a single layer of styrene-acrylonitrile copolymer, while in the sec ond case, a crack growth involves the neighboring layers. The equation for interlayer fracture toughness at variable thickness of cantilever s of dual-cantilever bending was derived. This equation allowed descri ption of both weak and strong bending of the cantilevers. The method f or estimation of fracture toughness by measuring the bending angle bet ween the cantilever ends, which was based on the above equation, was a dvanced. When delamination Was accompanied by crack jump between the n eighboring layers of styrene-acrylonitrile copolymer, a crack propagat es through the layer of plastic polycarbonate, and fracture toughness was shown to increase.