Damage initiation under transverse loading of unidirectional composites with arbitrarily distributed fibers

A limiting property governing the thermomechanical behavior of composites i s the strength transverse to the fibers. The present study investigates the dependence of this property on the distribution of fibers in the cross-sec tion of a unidirectional composite. The approach taken is to consider actua l distributions, which are arbitrary and are not necessarily described by r andom or periodic distributions. A fundamental issue in studying non-unifor m distributions is the size of a representative volume element (RVE). By th e use of an actual radial distribution function obtained for a ceramic-matr ix composite by quantitative stereology in conjunction with a simulation te chnique developed in this study, the RVE size is investigated with respect to initiation of debonding and radial matrix cracking - two basic mechanism s governing the transverse strength of composites. Tensile loading transver se to the fibers and residual stresses induced by thermal cooldown are cons idered separately as loading modes for transverse failure. The results prov ide some useful insight into the importance of non-uniformity of fiber spat ial distribution with regard to the transverse failure of composites. (C) 1 999 Elsevier Science Ltd. All rights reserved.