ELASTOPLASTIC CONSTITUTIVE RELATIONS FOR FIBER-REINFORCED SOLIDS

In this paper, we make use of a procedure for estimating the effective properties of nonlinear composite materials, proposed recently by Pon te Castaneda (1991, J. Mech. Phys. Solids 39, 45-71), to study the eff ective constitutive behavior of ductile, fiber-reinforced composites. Both estimates and rigorous bounds are obtained for the effective ener gy functions of multiple-phase, fiber composites with general ductile behaviors (in the context of deformation theory of plasticity) for the isotropic constituent phases. The resulting expressions for the energ y functions may be differentiated in a straightforward manner to obtai n corresponding estimates for the anisotropic effective stress-strain relations. Explicit calculations are carried out for the case of an al uminum-matrix composite reinforced with boron fibers. The results reve al some interesting features distinguishing the constitutive behavior of ductile-matrix, fiber-reinforced composites from that of linear-ela stic, fiber-reinforced composites. One such feature is the strong coup ling between the dilatational and distortional modes for the ductile f iber composites. Finally, comparisons are made with available experime ntal data.