FRACTURE OF RANDOM MATRIX-INCLUSION COMPOSITES - SCALE EFFECTS AND STATISTICS

We study crack patterns and effective stress-strain curves in unidirec tional fiber-matrix composites subjected to a uniform out-of-plane she ar. The fibers are aligned in the longitudinal direction and arranged randomly, with no overlap, in the transverse plane. Both fibers and ma trix are isotropic and elastic-brittle. We conduct this analysis numer ically using a very fine two-dimensional spring network and simulate t he crack initiation and propagation by sequentially removing bonds whi ch exceed a local fracture criterion. In particular, we focus on effec ts of scale and geometric randomness in these composites. We consider several ''windows of observation'' (scales) and study crack patterns, types of constitutive responses, and statistics of the corresponding s cale dependent effective elastic stiffness and strength of such compos ites. In the parametric study we cover a wide range of material combin ations defined by the stiffness ratio and the strain-to-failure ratio and we employ a damage plane in terms of these two parameters to illus trate the results. (C) 1998 Elsevier Science Ltd. All rights reserved.