A damage constitutive model of progressive debonding in aligned discontinuous fiber composites

A micromechanical damage constitutive model is presented to predict the overall elastoplastic behavior and damage evolution in aligned discontinuous fiber polymer composites (AFPCs). In an attempt to estimate the overall elastoplastic-damage responses, an effective yield criterion is micromechanically derived based on the ensemble-volume averaging process and first-order (noninteracting) effects of eigenstrains stemming from the existence of (prolate) spheroidal fibers. The proposed effective yield criterion, in conjunction with the assumed overall associative plastic flow rule and hardening law, provides analytical foundation for the estimation of effective elastoplastic behavior of ductile matrix composites. Uniaxial elastoplastic stress-strain behavior of AFPCs is also investigated. An evolutionary interfacial debonding is subsequently employed in accordance with Weibull's probability function to characterize the varying probability of fiber debonding. Finally, the present damage model is compared with Halpin-Tsai's bounds for stiffness predictions and is applied to uniaxial loading to illustrate the damage behavior of AFPCs. (C) 2001 Elsevier Science Ltd. All rights reserved.