COMPOSITE PATCHES AS REINFORCEMENTS AND CRACK ARRESTORS IN AIRCRAFT STRUCTURES

The application of adhesively bonded composite patches as reinforcemen ts and crack arrestors for a multisite damaged aircraft structure is i nvestigated. Experiments are performed to test the ability of a bonded composite reinforcement to prevent cracks from coalescing. With a fin ite element model developed for composite patch repairs, the effect of thermal residual stresses on the stress-intensity factor and the resu lting fatigue crack growth rate is demonstrated. An effective thermal stress is estimated by comparing experimental results with model predi ctions. Reinforcement for a multiple-site damage situation is analyzed by modeling an infinite row of closely spaced cracked rivet holes. Th e composite reinforcement is shown to dramatically reduce the stress-i ntensity factor, increase fatigue life, and protect against catastroph ic failure.