Fatigue Behaviour of AA 7075-T6 Plates Repaired at Different Crack Lengths

Abstract

Bonded Composite Repair Technology (BCRT) is widely used to reinforce weakened cracked components and damaged metallic structures in various aerospace applications. In this work, the fatigue crack behaviour of V- notched aluminium 7075-T6 plates, of 2 mm thickness, bonded with “single side” carbon composite patch configuration was experimentally investigated. The repair efficiency and fatigue life of cracked specimens repaired at different initial crack lengths of (a₀ = 3 mm, 6 mm and 9 mm) and different stress ratios of (R = 0 and R = 0.1) were investigated. The results obtained showed that the bonded patch increases the fatigue life of all repaired samples ranging from 2.2 folds for 9 mm to 4.3 folds for 3 mm initial crack lengths. Repair can be treated at any level of crack initiation but preferably should be conducted as soon as it is detected. Stress ratio and initial crack lengths affect the repair efficiency. This is clearly manifested in the extended life and load carrying capacity of adhesively bonded specimen.