Effect of inelastic material behavior on residual stresses in metal matrix composites

A crucial problem in the application of Metallic and Intermetallic Matrix Composites is the presence of high residual (internal) stresses, induced during the fabrication process. These stresses are essentially thermal in nature, and are caused by a significant difference in the coefficients of thermal expansion (CTE) of the fiber and the matrix and the large temperature differential of the cooling process. Residual stresses may lead to the development of matrix cracking, and may also have an adverse effect on the thermomechanical properties of the composites, e.g., stress-strain behavior, fracture toughness, fatigue and creep. The nature, magnitude and the spatial distribution of residual stresses in the matrix and interface are very strongly influenced by the temperature-dependent matrix inelastic behavior, e.g., plasticity, and creep. In this paper, the effect of matrix inelasticity on residual stress is examined by evaluating the stress distribution as a function of space and time through finite element simulation. It is shown that in Aluminum-based metal matrix composites, viscous effects lead to the decay of stresses with time whereas such effects are insignificant in Titanium-based composites.