Elastic-plastic behavior of textured short-fiber composites

Abstract 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. Soc. 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-A1 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 flow stress over the entire range of deformation.