Acoustic emission characterization of a notched aluminum plate repaired with a fiber composite patch

Edge-notched, aluminum-alloy (Al6061-T6) plate specimens were repaired with glass fiber composite patches as a function of the number of fiber ply stackings. Damage progress of the specimens under tensile loads, which was monitored by acoustic emission (AE) measurements, was divided into stages I, II and III. Stage I gave rise to only co-cured resin cracking while stage III generated only Al cracking. Stage II, where the fiber patches were actually fractured, were focused on to clarify AE characteristic differences. The behaviors of AE parameters were analyzed based on various fracture processes of Al cracking, resin cracking, fiber breakage, and delamination between fiber patches and aluminum plates. The fracture of the patch-repaired regions was differentiated in accordance with different peak frequency contents and amplitude distributions of the various fracture processes. These AE characteristics were ascertained using various thicknesses of the fiber ply stacks in a patch.