Micromechanics of toughened polycarbonate

Numerical studies are presented on micromechanical and macromechanical aspects of deformation mechanisms in toughened polycarbonate. The dependence of the macroscopic stress-strain behavior, and of the underlying patterns of matrix deformation, on void distribution and triaxiality of the loading conditions are discussed. The presence of voids is shown to create stress fields which favor shear yielding over,brittle failure mechanisms and thus provide toughness even in the case of highly triaxial stress states. Additionally, we compare predictions obtained using a micromechanical model based on a traditional axisymmetric unit cell, with predictions obtained with an alternative model based on a staggered array of voids. The new model is an axisymmetric equivalent to the Voronoi tessellation of a Body Centered Cubic array of voids (V-BCC model). The V-BCC model appears to be able to better capture essential features of the mechanical behavior of the blends, and provides a more realistic cell-based representation of particle-filled materials in general. (C) 2000 Elsevier Science Ltd. All rights reserved.