THE EFFECTIVE YIELD STRENGTH OF FIBER-REINFORCED COMPOSITES

This work is concerned with the determination of the effective propert ies of transversely isotropic fiber composites made up of two rigid-pe rfectly plastic phases in prescribed volume fractions. The phases are assumed to satisfy incompressible, isotropic yield criteria of the Mis es type. To study the behavior of these composites we make use of vari ational principles, recently developed by Ponte Castaneda (1991, J. Me ch. Phys. Solids 39, 45-71), that provide a method for generating esti mates for the effective properties of nonlinear composites from corres ponding estimates for the effective properties of linear composites. W e demonstrate that this method allows us to obtain simple expressions for the effective yield functions of rigid-perfectly plastic composite s. Explicit results, corresponding to the Hashin-Shtrikman bounds, the self consistent and the generalized self consistent estimates, and th e composite cylinder assemblage model are obtained for the class of ri gid-perfectly plastic fiber composites. These estimates exhibit the ex istence of two distinct yielding modes, in agreement with correspondin g experimental results.