A Review on Direct Assembly of Through-the-Thickness Reinforced Metal–Polymer Composite Hybrid Structures

Constant efforts to reduce the structural weight of transportation systems as a solution to control emission levels are currently shaping the way modern cars and airplanes are designed and manufactured. Increased attention has been given to innovative metal–composites multi-material concepts for the production of lightweight structures. However, the nature of these very dissimilar materials makes their joining a rather complicated task. Recently several technologies have been proposed to overcome process limitation and increase the load transfer between metal and composite in hybrid structures. One of the promising solutions is a new concept known as direct assembling with through-the-thickness reinforcements. In this concept, the composite material of a hybrid joint is directly assembled upon a surface-structured metallic part. Features structured on the metallic part, by a manufacturing phase, act as a through-the-thickness reinforcement improving the out-of-plane strength and load transfer capabilities of such joints. The current status and state-of-art direct assembling technologies are reviewed in this article. Examples of reviewed metal structuring techniques include micromachining, stamping, Surfi-Sculpt, additive manufacturing, cold metal transfer, and metal injection molding structuring. Direct assembling techniques addressed in this article are vacuum-assisted resin infusion, resin transfer molding, prepreg/autoclave assembly, and ultrasonic joining. POLYM. ENG. SCI., 2018.