COMPOSITE PLASTICITY BASED ON MATRIX AVERAGE 2ND-ORDER STRESS MOMENT

An effective stress of a ductile matrix is defined directly from the a verage second order stress moment. It is evaluated exactly provided th at an estimation of the composite effective moduli is given. On the ba sis of this effective stress and the secant moduli concept originally proposed by Berveiller and Zaoui (Berveiller, M. and Zaoui, A. (1979). An extension of the self-consistent scheme to plastically-flowing pol ycrystals. J. Mech. Phys. Solids 35, 325-344) and modified for composi te materials by Tandon and Weng (Tandon, G. P. and Weng, G. J. (1988). A theory of particle reinforced plasticity. ASME J. Appl. Mech. 55, 1 26-135), a method for composite plasticity is then proposed. The metho d is capable of predicting the influence of hydrostatic stress on part icle-reinforced composite yielding, especially for porous materials at high triaxiality. Compared to Tandon and Weng's model, the proposed m ethod gives always softer predictions. For particle reinforced composi tes, the new matrix average effective stress coincides with that obtai ned by Ponte Castaneda's variational procedure (Ponte Castaneda, P. (1 991). The effective mechanical properties of nonlinear isotropic compo sites. (C) 1997, Elsevier Science Ltd.