Abstract
The tensile properties of coextruded multilayer composites comprised of predominantly 49 alternating layers of polycarbonate (PC) and polystyrene- acrylonitrile (SAN) were investigated in the bulk and microscopically. The bulk was characterized by three types of behaviour: brittle fracture at low strains, ductile yielding with fracture during neck formation, and formation of a stable neck followed by drawing to high extension. Optical microscopy was utilized to correlate deformation mechanisms within each phase to the observed modes of deformation in the bulk. Optical microscopy showed that in all cases the initial irreversible deformation event was the formation of cracks or crazes in the SAN layers. Good adhesion between the layers resulted in the subsequent initiation of shear bands in the polycarbonate layers at the craze tips. Interaction of crazes and shear bands produced an expanded damage zone ahead of the propagating crack which delocalized the stress and delayed fracture. The ultimate mode of fracture depended on the relative thickness of the SAN and PC layers, as determined by the composition, and the strain rate.
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Gregory, B.L., Siegmann, A., Im, J. et al. Deformation behaviour of coextruded multilayer composites with polycarbonate and poly(styrene-acrylonitrile). J Mater Sci 22, 532–538 (1987). https://doi.org/10.1007/BF01160765
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DOI: https://doi.org/10.1007/BF01160765