Particle size effect in metal matrix composites: A study by the continuum theory of stress gradient plasticity

Abstract

The plastic behavior of particle-reinforced composites is studied by the continuum theory of stress gradient plasticity. This theory has been quite successful in predicting the size-dependent behavior in micro-torsion and -bending. Analyses are carried out on the axisymmetric unit cell finite element models for two sets of SiC/Al composites. Subsequent stress gradient plasticity predictions of the stress–strain curves in comparison with the corresponding experimental data show excellent agreement of flow strength for composites of varying particle size. Our results reveal that the experimental observations of particle size effect can be explained in terms of a stress gradient plasticity theory with one material length variable, which depends on the matrix microstructure. Therefore, stress gradients in the matrix—originated from the mismatch of elastic moduli between the particles and matrix—together with the matrix microstructure can control the size-dependent behavior in composites. However, the impact of this novel mechanism in competition with other well-known mechanisms can only be revealed by experimental investigations with careful attention on the matrix microstructure of composites.