Effects of particle shape and size distribution on particle size dependent flow strengthening in metal matrix composites

Particle size effects in metal matrix composites are studied within the continuum theory of mechanism-based strain gradient (CMSG) plasticity. This theory has been quite successful in predicting the size dependent plastic behavior in a wide variety of problems. Two-dimensional (plane-strain) analyses which are carried out on the composite unit cell models with multi-particles of circular shape show that the flow stress of the composites increases by decreasing particle size with a high sensitivity to small particle size. The numerical results are in good agreement with experimental data. Subsequently, the effects of particle shape, orientation and size distribution on the behavior of composites are investigated. Analyses are carried out on the composites containing squared, rectangular and elliptical (with aspect ratio of four) particles of various orientations with respect to the loading direction (i.e. vertical, horizontal and 45 degree inclined directions). The stress inhomogeneity in the matrix, the overall stress-strain curve and the maximum principle stress in the particles of composites with non-circular particles are investigated and compared with those obtained for the composites containing circular particles. The effects of particle size distribution on the behavior of composites are also addressed.