MODELING THE CONDITIONS FOR FATIGUE FAILURE IN METAL-MATRIX COMPOSITES

An investigation on the fatigue crack growth (FCG) and fatigue failure in metal matrix composites (MMCs) has been conducted using a model ba sed on micromechanical elasto-plastic fracture mechanics (EPFM) princi ples. To evaluate the model comparisons between experimental and predi cted fatigue life have been made for two silicon carbide strengthened (SCS)-6/Ti-based MMCs. Conditions for crack arrest and crack instabili ty have also been considered in order to define the fatigue damage lim its. Crack arrest occurs from the added effects of fibre bridging and the constraint provided by the fibre on matrix microplasticity, while crack instability is achieved when the fibre constraint effect is mini mum and the fatigue resistance of the material is reduced due to the a ccumulation of fatigue damage. Comparisons of the predicted fatigue da mage limits with experimental results show good agreement which underl ines the usefulness of a microstructural fracture mechanics model.