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The progressive damage mechanism is a major concern for engineering metals, particularly in the aerospace industry. This manuscript reviews the application of composite patches for repairing cracked metal substrates. The survey includes both experimental and numerical investigations primarily focused on the fatigue performance of cracked aluminum, with and without composite patches. Various performance factors, such as patch geometry, ply orientation, stacking sequence, adhesive effects, temperature variations, and their impacts on material properties, are explored in detail. The significance of optimal values for these factors is highlighted. Performance measures are examined, including the stress intensity factor (SIF), stress concentration factor, crack propagation, and fatigue crack growth rate, along with their relationship to material fatigue life. This review paper emphasizes the reduction of the SIF at the crack tip, achieved through adhesive bonding, which leads to mitigated crack propagation and consequently increases the fatigue life of damaged metal substrates. Achieving adhesion between the composite patch and the substrate metal presents a significant challenge that affects stress concentration and distribution, enhancing the substrate material’s fatigue resistance. The paper thoroughly explores these challenges, highlighting the importance of bonded repair in optimizing the repair methodology. Improvement techniques such as overloads, single- and double-sided bonded patches, and experimental parameters like loading frequency and ratios have been extensively explored. The analysis is further extended to discussions on the effects of environmental and operational conditions.
Rajendran et al. (Wed,) studied this question.