Fatigue performances of the cracked aluminum-alloy pipe repaired with a shaped CFRP patch

To fully understand performances of the cracked aluminum-alloy pipe repaired with CFRP patches, a series of fatigue and quasi-static tests were conducted on commercial available type-7005 pipes. The pipe damaged with artificial cracks was wrapped around by shaped CFRP patches. Two bonding surface treatment methods, i.e. screw-thread and mechanical grinding, were proposed and applied in the repairing process. The fatigue life, residual stiffness and cyclic creep of the repaired specimen were tested, respectively. A fine numerical model was built in ANSYS and validated by the test data. The stress intensity factor was calculated by the developed FE model to reveal the failure mechanism of fatigue tests. The influences of patch length and number of layers were also evaluated and discussed. Test results showed that the fatigue life of the wrapped specimen with the screw thread surface treatment was 22.18 times of that of the bare specimen, and 23.13% longer than that of specimen treated by mechanical grinding. It is concluded that the CFRP patch is capable of improving fatigue performances of the cracked aluminum-alloy pipe. The screw-thread surface treatment provides better fatigue effects than mechanical grinding. Optimized design in the shaped CFRP patch benefits achieving the best fatigue performances of repaired aluminum-alloy pipes.