Low-velocity impact studies on Kevlar/Epoxy composites reinforced with carboxyl functionalized Graphene

Abstract

The addition of nanoparticles as fillers improves the properties of polymer matrix composites. In this work functionalized Graphene Platelets are added to Kevlar-reinforced epoxy composites and their mechanical properties such as tensile, short beam strength and low-velocity ballistic response are evaluated. For comparison, composites prepared with 0.25, 0.5, and 0.75 wt% filler addition was compared with the condition of no filler addition. The fractured samples were examined to understand the failure mechanisms involved. The results indicated that the sample with 0.5 wt% had superior tensile, shear and energy-absorbing characteristics. A lower reinforcement weight percentage (0.25%) was unable to effectively transfer the loads while higher reinforcement percentage (0.75%) showed premature failures due to agglomeration. At the optimum reinforcement, a sufficient amount of nano-fillers passes through the matrix and the functionalization assists in good fiber–matrix adhesion through surface bonding. This leads to high interfacial properties giving high resistance to impact motion. In addition, the nanoparticles in the matrix phase help in matrix toughening giving resistance to cracking. This is evident from the micro and macroscopic fracture images which show a high fiber interaction and the least matrix failure. The lower damage area and the higher fiber pullouts also indicate the effectiveness of 0.5 wt% reinforcement.