Finite element simulation to investigate interaction between crack and particulate reinforcements in metal-matrix composites

Elastic-plastic finite element simulations have been carried out to determine the effect of the presence of single particles and particle clusters ahead of the crack tip on the stress distribution at the crack tip. The resulting knowledge about stress distribution has been used to provide insight regarding the predominant factors that influence crack propagation. This study indicates that the presence of particle(s) relatively far away from the crack tip increases the crack opening stress at the crack tip. The crack opening stress is, however, subdued as the crack approaches the particle(s). Particle clustering influences the stress distribution by suppressing plastic deformation inside the cluster and hence plastic deformation occurs predominantly outside the cluster. Experimental observation of slip bands and crack propagation characteristics in SiC-reinforced aluminum A356 confirms this fact. It is also found that particle clustering creates higher interface shear stress and von-Mises stress regions in the particle away from crack tip, while the highest interface normal stress region exists at the interface of the particle along the crack line. Therefore, depending upon the stress that predominates, the crack can either deviate and go around the cluster region or go straight through the cluster region.