DEFORMATION OF METAL-MATRIX COMPOSITES WITH CONTINUOUS FIBERS - GEOMETRICAL EFFECTS OF FIBER DISTRIBUTION AND SHAPE

Numerical results are presented on the effects of fiber distribution and of fiber cross-sectional geometry on the deformation of a metal-matrix composite reinforced with continuous fibers. The geometrical variables analyzed include several periodic and random distributions of unidirectional cylindrical fibers with circular, hexagonal and square shapes. The model system chosen for the finite element analysis is a 6061-O aluminum alloy reinforced with boron fibers. It is shown that, for a reinforcement level of 46 vol.% boron fibers, tensile and shear deformation in orientations transverse to the fiber axes are markedly influenced by both the packing of fibers and their cross-sectional shape, although the deformation of the composite is insensitive to such geometrical effects for tensile loading in the direction of fiber alignment. The effect of fiber distribution on the constitutive response is relatively stronger than that of fiber shape. The geometrical effects of fiber distribution on deformation are significantly less pronounced for the 6061 aluminum-matrix composite with 20 vol.% boron fibers. Details of the evolution of plastic strains and hydrostatic stresses in the constrained matrix during far-field loading are discussed, and the influence of such constraint on the geometry dependence of deformation is examined. The scientific and practical implications of the results are also pinpointed.