EFFECTS OF REINFORCEMENT ORIENTATION ON THE TENSILE RESPONSE OF METAL-MATRIX COMPOSITES

A three-dimensional unit cell model is used to analyze the effect of reinforcement orientation on the tensile response of particle and whisker-reinforced metal-matrix composites. The metal matrix is characterized as an isotropically hardening elastic-viscoplastic solid and the ceramic reinforcement is taken to be isotropic elastic. Perfect bonding between the matrix and the reinforcement is assumed. The numerical results show a strong decrease in tensile stress level for small deviations of the whiskers from perfect alignment with the tensile axis. The tensile stress-strain response becomes rather insensitive to the precise value of the misalignment angle when the misalignment is sufficiently large. These trends are also seen in the experiments conducted in the present work on SiC whisker-reinforced aluminum alloys subject to tension at various angles to the whisker axis. For particle-reinforced composites, the computed overall tensile is much less sensitive to reinforcement alignment. The numerical simulations also provide results for the evolution of field quantities in the matrix and in the reinforcement. A strain-induced rotation of the reinforcement is predicted for the case of whiskers reinforcement, whereas nearly no rotation is predicted for the particles.