Investigation the interface and charpy impact behavior of fiber metal laminates containing graphene nanoplatelets and glass kevlar hybrid fibers

In this research, the effect of graphene on the impact behavior of fiber metal laminates (FMLs) reinforced with hybrid of glass-Kevlar fibers, was investigated. FMLs including hybrid of glass-Kevlar fibers/ aluminum 2024 with different weight percent of graphene were made by hand lay-up method and subjected to impact charpy test. Also, before making composites, the surface of aluminum is modified using a chemical method to improve the bond between it and composite. The use of graphene reduced impact strength in the FMLs. Thus, by adding 0.25, 0.5 and 1 wt.% graphene to epoxy, 34.2, 41.8 and 58.86%, respectively, reduction were observed in the impact strength compared to the graphene-free sample. Increasing the amount of graphene in the composite, the degree and the probability of separation between the aluminum and the composite increased, and the FMLs showed a more brittle behavior. Thus, in the sample without graphene, the separation did not occurred, but with increasing graphene, the separation become more and finally for samples containing 1 wt.% graphene despite the separation between the aluminum and composite, brittle fracture in the composite and the subsequent failure of aluminum was observed. According to microscopic images, the presence of graphene and its agglomerate at the interface between aluminum and composite causes initiation and crack growth. Graphene also fills the cavities formed on the aluminum surface, which are formed to better interact with the resin by surface modification, and prevent the penetration of the resin and the proper bonding between the epoxy and the aluminum.