A Study on the Charpy Impact Response of the Cracked Aluminum Plates Repaired with FML Composite Patches

Fiber metal laminates (FMLs) are widely used in aerospace industries nowadays. Reparation of the cracks in these advanced materials was first done by some aeronautical laboratories in the early 1970s. In this study, experimental investigations were done on the effects of repairing the edge-cracked aluminum plates using the FML patches. The repairing processes were conducted to characterize the response of the repaired structures to the Charpy impact tests. The composite patches were made of one aluminum layer and two woven glass–epoxy composite layers. Three different crack lengths, crack angles, and patch lay-ups were examined. It was indicated that for the lengthen cracks, the effect of increasing the crack angle on energy absorption in the structure was more. When the ratio of crack length to the specimen width, i.e., a/w, is 0.5, the energy absorption per unit area of the specimens having different crack angles but the same patch lay-ups was so different. It was also observed that the percentage of the absorbed energy of 45° cracked angle specimens was about 25% higher than the 0° ones. Also it was observed that the lay-up of the patches and the place where the metal layer was embedded in the FML patches had an important effect on the impact response of the tested specimens. The more the metal layer of the patches is far from the interfacial surface of the aluminum plate and the FML patches, the less the energy absorbs in the structure.