Impact of overload on the fatigue behaviour of a plate with a central crack

Fatigue, a critical concern in aeronautical engineering, arises from the repeated application of cyclic loads, which can lead to the initiation and growth of cracks over time. Such fatigue-induced cracks, particularly internal microcracks, are challenging to detect and can severely compromise components' structural integrity and service life. This study focuses on the fatigue behavior of aluminum alloy plates featuring a central crack subjected to cyclic loading, with particular attention to the impact of overload events and the efficiency of Boron/Epoxy composite patch repairs. The investigation is conducted on four aerospace-grade aluminum alloys—2024-T3, 2024-T861, 7075-T73, and 7075-T6. It examines the effect of load ratio on fatigue crack propagation rates (oK) and provides a comparative analysis between unrepaired plates and those reinforced with Boron/Epoxy patches. Additionally, the study evaluates the influence of overload ratios on fatigue life and crack growth dynamics, demonstrating that composite repairs can induce significant crack growth retardation. The results confirm the effectiveness of Boron/Epoxy patches in enhancing fatigue life and resistance to crack propagation under a range of loading conditions. Among the alloys tested, 2024-T3 displayed the most favorable fatigue performance. Overall, the findings underscore the critical role of material selection and repair strategy in extending the service life and ensuring the structural reliability of aeronautical components.