Abstract
In this study, the three-dimensional and nonlinear finite element method is used to estimate the performances of bonded composite repairs of metallic cracked aircraft structures by analyzing the J integral and at the crack tips of repaired cracks for single and double symmetric patches. Several calculations have been realized to extract the plasticized elements around the crack tip. The obtained results show that composite repair reduces significantly the J integral at the crack tip which can improve the fatigue life of aircraft structures. It was also shown that the double symmetric patch has a considerable beneficial effect on the repair performance compared to the single patch.