An experimental study on the hybrid bolted/bonded jointed carbonfiber reinforced epoxy composite: The effect of recycled nanofiber polystyrene

In this thesis, the effect of polystyrene (PS) nanofiber reinforcement on carbon fiber-reinforced epoxy composites was investigated in single lap bolted, bonded, and hybrid bolted/bonded (HBB) joint configurations. HBB joints combine the advantages of bolted and bonded joint techniques; however, the performance of the adhesive layer significantly affects the load-carrying capacity of HBB joints. Nanofiber reinforcement has emerged as an effective solution to enhance the bonding performance of bonded and HBB joints. For this purpose, PS nanofibers were produced from waste polymers using the electrospinning method as an environmentally friendly approach. PS nanofiber mats were placed as a reinforcement layer between the adherends, and the specimens were tested under quasi-static tensile loading. Tensile testing was performed according to ASTM D5961 standards. By PS nanofiber reinforcement, a significant improvement of 10% in the maximum load value of the bonded joint was observed, while the fracture energy of the HBB joint increased by 15%. All nanofiber reinforced specimens exhibited higher strength in terms of maximum load and fracture energy compared to the specimens without nanofiber reinforcement. Progressive damage modes were observed in PS-reinforced specimens compared to neat epoxy specimens. In this sense, the compatibility of recycled PS nanofiber with epoxy and the improved performance of the adhesive layer through PS modification were tought to be effective. The morphology of the fracture surfaces of the specimens was examined using scanning electron microscopy (SEM), and the factors influencing fracture toughness were investigated.