Tensile and fatigue response of alumina-fiber-reinforced aluminum matrix composite

The tensile and fatigue behavior of an alumina-fiber-reinforced pure aluminum matrix composite was investigated. The S–N curve was determined under tension–tension loading. The fracture surfaces and microstructures of test samples were examined to understand the fatigue damage mechanisms of the composite. The composite revealed a high tensile strength and high fatigue resistance attributed to a damage tolerant behavior. The monotonic tensile strength was 1400–1500 MPa while the endurance limit with an R ratio of 0.1 was 750 MPa. The fatigue damage mode was strongly dependent on applied stresses. At high stresses, the fatigue life was controlled essentially by the initiation and growth of a single crack, and the composite behaved in a damage-intolerant manner. At low stresses, the fatigue life was mainly controlled by the initiation and growth of longitudinal surface splitting. This lead to damage-tolerant behavior. At intermediate stress levels, a transformation in fatigue damage mode could evolve from the surface splitting and distributed matrix cracking to the growth of a single matrix crack.