Micromechanics of toughened polycarbonate

Numerical studies are presented on micromechanical and macromechanical aspe cts 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 con ditions are discussed. The presence of voids is shown to create stress fiel ds which favor shear yielding over,brittle failure mechanisms and thus prov ide toughness even in the case of highly triaxial stress states. Additional ly, we compare predictions obtained using a micromechanical model based on a traditional axisymmetric unit cell, with predictions obtained with an alt ernative model based on a staggered array of voids. The new model is an axi symmetric equivalent to the Voronoi tessellation of a Body Centered Cubic a rray of voids (V-BCC model). The V-BCC model appears to be able to better c apture essential features of the mechanical behavior of the blends, and pro vides a more realistic cell-based representation of particle-filled materia ls in general. (C) 2000 Elsevier Science Ltd. All rights reserved.