Design of composite patch reinforcement applied to mixed-mode cracked panel using finite element analysis

Aircraft repair is gaining importance for extending the fatigue life of aging aircrafts and also for improving its structural integrity. Among various repair techniques, bonded composite repair is mostly preferred. In this paper, a three-dimensional finite element analysis is carried out to study and compare the performance of single- and double-sided patch on center-cracked aluminum panel. The effects of different parameters such as patch layup, patch thickness and patch material on the stress intensity factor is highlighted. It is shown that the mechanics of double-sided repair is completely different from the single-sided repair. Also, it is found that double-sided repair is more efficient than single-sided repair. In case of single-sided repair, alternative patch material like unbalanced lamina or transversely graded material is proposed. It is observed that there is significant reduction of stress intensity factor with transversely graded patch in case of single-sided repai