Stress enhancement at inclusion particles in aluminum matrix composites: computational modeling and implications to fatigue damage

The evolution of stresses inside the native inclusion particles in silicon carbide (SiC) particulate reinforced aluminum (Al) matrix composites is studied computationally by recourse to the finite element method. It is motivated by the experimental findings that inclusion fracture serves as the fatigue crack initiation in such types of composite materials. The analyses were performed for a simplistic model, with the inclusion embedded within a homogeneous material bearing the properties of Al/SiC mixture, and a refined model, with the inclusion, Al matrix and SiC particles specifically included. The simplistic model was found to be able to predict the stress enhancement in the inclusion that is consistent with the measured propensity of fatigue crack initiation when elasticity dominates. When plastic yielding occurs, the simplistic model failed to predict the experimental trend due to its inability to capture the highly nonuniform plastic flow field within the Al matrix. The refined three-phase model is needed for the plastic analysis. Implications of the present findings to general numerical modeling of composite materials are discussed. (C) 2001 Elsevier Science B.V. All rights reserved.