Notched behaviour of a silicon carbide particulate reinforced aluminium alloy matrix composite

The notched fatigue behaviour of a fine particulate reinforced AlCuMg (2124) matrix composite is compared with that of an equivalent monolithic alloy (2024), both in the T4 condition. The difference in response of the materials for tensile and fatigue loading is pronounced. Under tensile loading the composite exhibits ‘notch weakening’ and an almost brittle fracture, while the monolithic alloy shows a degree of ‘notch strengthening’. In contrast, under fatigue loading the composite exhibits a much smaller notch sensitivity than that of the monolithic alloy. At 107 cycles the fatigue notch sensitivity factor is reduced by ∼ 6.5. The notched tensile behaviour of the composite is interpreted in terms of its reduced ductility and susceptibility to cavitation. Conventional notch theory is able to account for the notch sensitivity of the monolithic alloy in fatigue, but not the composite.