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

A micromechanical damage constitutive model is presented to predict the ove rall elastoplastic behavior and damage evolution in aligned discontinuous f iber polymer composites (AFPCs). In an attempt to estimate the overall elas toplastic-damage responses, an effective yield criterion is micromechanical ly derived based on the ensemble-volume averaging process and first-order ( noninteracting) effects of eigenstrains stemming from the existence of (pro late) spheroidal fibers. The proposed effective yield criterion, in conjunc tion with the assumed overall associative plastic flow rule and hardening l aw, provides analytical foundation for the estimation of effective elastopl astic 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. Final ly, the present damage model is compared with Halpin-Tsai's bounds for stif fness predictions and is applied to uniaxial loading to illustrate the dama ge behavior of AFPCs. (C) 2001 Elsevier Science Ltd. All rights reserved.