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 stu died computationally by recourse to the finite element method. It is motiva ted by the experimental findings that inclusion fracture serves as the fati gue crack initiation in such types of composite materials. The analyses wer e performed for a simplistic model, with the inclusion embedded within a ho mogeneous material bearing the properties of Al/SiC mixture, and a refined model, with the inclusion, Al matrix and SiC particles specifically include d. The simplistic model was found to be able to predict the stress enhancem ent in the inclusion that is consistent with the measured propensity of fat igue crack initiation when elasticity dominates. When plastic yielding occu rs, the simplistic model failed to predict the experimental trend due to it s 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 com posite materials are discussed. (C) 2001 Elsevier Science B.V. All rights r eserved.