Fatigue Behavior of Notched Aluminum Plates Repaired by Smart and Composite Patches

In this study, mode I fatigue crack growth behavior of single edge notched thin aluminum plates repaired with single side composite patches is investigated experimentally. Three patches are investigated in this analysis, 1- three layers carbon/epoxy laminated composite patch, 2- smart patches contained shape memory alloy (SMA) wires without pre-strain embedded in between the carbon/epoxy layers, and 3- smart patches contained SMA wires with pre-strain embedded in between the carbon/epoxy layers. The results are compared with the results obtained for un-repaired notched plate and the influence of SMA wires is also studied. The experimental results show a significant increase in crack growth life in all repaired plates compared with un-repaired plate. The repaired plates with smart pre-strained SMA patches show greater life as compared to other plates repaired by other patches. The three layers carbon/epoxy patches show better results compared to smart SMA un-strained patches. Also, numerical modeling is done by ANSYS software to obtain the stress intensity factor in mode I fatigue loading and then applied to Paris law for prediction of the fatigue crack growth life. The results are compared with the experimental results and a good agreement is obtained.