Analysis of hybrid joints of green composites under tensile and compressive loadings

Adhesive bonding and mechanical fastening techniques are mostly applied for the joining of polymer composites. However, in recent times, the hybrid joining (bonded/bolted) technique is emerging, as it prevents premature failure of composite joints. An experimental investigation was carried out in this study to analyze the hybrid joining behavior of green composites (bamboo/poly(lactic acid) (PLA)) under tensile and compressive loadings. The hybrid joints were developed by combining bolted and bonded joints. The hole in the specimen prerequisite for the bolted joint was obtained by traditional drilling performed at a constant spindle speed of 2000 revolutions per min and an axial feed of 45 mm/min using a multifaceted solid carbide drill bit. A bolt fastening torque of 20 N m was applied to facilitate the mechanical joining. Three bonding materials – namely, (a) epoxy, (b) polyurethane and (c) parent polymer (PLA) – were used to obtain the bonded joint. The important factors of the hybrid joint, such as (a) overlapping length, (b) width of the specimen and (c) bonding material, were considered, and their effect on both tensile and compressive failure loads was evaluated. The significance of the parameters of the hybrid joint was evaluated through statistical modeling.