Abstract :
An effective stress of a ductile matrix is defined directly from the average second order
stress moment. It is evaluated exactly provided that an estimation of the composite effective moduli
is given. On the basis of this effective stress and the secant moduli concept originally proposed by
Berveiller and Zaoui (BerveiUer, M. and Zaoui, A. (1979). An extension of the self-consistent scheme
to plastically-flowing polycrystals. J. Mech. Phys. Solids 35, 325 344) and modified for composite
materials by Tandon and Weng (Tandon, G. P. and Weng, G. J. (1988). A theory of particle
reinforced plasticity. ASME J. Appl. Mech. 55, 12(~135), a method for composite plasticity is then
proposed. The method is capable of predicting the influence of hydrostatic stress on particlereinforced
composite yielding, especially for porous materials at high triaxiality. Compared to
Tandon and Wengʹs model, the proposed method gives always softer predictions. For particle
reinforced composites, the new matrix average effective stress coincides with that obtained by Ponte
Castanedaʹs variational procedure (Ponte Castaneda, P. (1991). The effective mechanical properties
of nonlinear isotropic composites. J. Mech. Phys. Solids 39, 45 71). © 1997, Elsevier Science Ltd.
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