BOUNDS ON OVERALL INSTANTANEOUS PROPERTIES OF ELASTIC PLASTIC COMPOSITES

Minimum principles of plasticity are used to derive upper and lower bounds on ordered eigenvalues and on diagonal terms of instantaneous stiffness and compliance matrices of elastic-plastic composite aggregates subjected to uniform overall stress or strain increments. The method is implemented with the help of a periodic model of binary fibrous composites; overall properties are derived from incremental solutions of an inclusion problem in a small unit cell. Actual results are found with displacement and equilibrium formulations of the finite element method. Examples are presented for the fibrous B-Al system. The technique can be used to evaluate instantaneous element properties in a finite element program for analysis of metal matrix composite structures.