Thickness effects on fatigue properties of cracked aluminum alloy plate single-side repaired with boron fiber/epoxy patches

Using the vacuum bag technique for the patches of boron fiber/epoxy (B_f/epoxy) composites，the center-cracked aluminum alloy plates with different thickness were repaired，and then the fatigue properties of the repaired specimens were tested. The fatigue life，crack growth rate and crack growth lag of the repaired specimens were investigated under fatigue loadings. The results show that the fatigue life of the center-cracked aluminum alloy plates is increased by repairing with B_f/epoxy patches，and the increment of fatigue life decreases with the increase of the plate thickness. The fatigue life of the repaired specimens with thicknesses of 1.76mm，5.20mm and 10.20mm is 22.30 times，12.84 times and 8.40 times that of those unrepaired specimens respectively. The repaired specimens with thickness of 1.76 mm can still bear fatigue loading when the aluminum alloy plate fractured completely，while the repaired specimens with thickness of 5.20mm and 10.20mm can not do so. Both crack growth rate and normalized crack length difference increase with the increase of the plate thickness.