Elastic-plastic behavior of textured short-fiber composites

We propose a relatively simple micromechanics model to predict the elastic-plastic response of short-fiber composites with a preferred orientation of the reinforcement, i.e. a texture. Our theoretical efforts are directed toward a composite system with an elastic-plastic matrix containing elastic reinforcement, but the extension to allow elastic-plastic response of the reinforcement is straightforward. The theory is based on the combination of our recent model for textured elasticity of short-fiber composites and the often-used idea of a linear comparison composite to simulate the nonlinear behavior of the actual composite as proposed by Hill(J. Mech. Phys. Solids, 1965, 13, 89) and Hutchinson (Proc. R. Sec. London, 1970, A319, 247). We compute the effective stress of the heterogeneously deforming matrix from the distortional energy of the matrix using the approach recently proposed by Qiu and Weng (J. appl. Mech., 1992, 59, 261, J. appl. Mech., 1995, 62, 1039). We give simple, easily used, results for orientation distributions of practical significance. We compare our predictions with measured stress-strain curves for an extruded SiC/6061-Al short-fiber composite with a fiber orientation distribution that is axially symmetric about the extrusion axis. The predictions are in excellent agreement with measurements for the axial and transverse Young's moduli and the 0.2% yield stress. Good agreement is obtained between the predicted and measured how stress over the entire range of deformation. (C) 1997 Acta Metallurgica Inc.