Engineered systems in today’s automobiles are often designed and built to meet conflicting and complex requirements. While mobility is a car’s primary function, accomplishing that in an energy-efficient manner and ensuring the safety of the occupants are critical requirements. Automotive OEMs, therefore, are aggressively working on making vehicles lighter without compromising its safety. Meeting such complex requirements often requires solutions encompassing innovative designs, manufacturing processes and multi- material systems.

This paper focuses on the development of lightweight metal-plastic body-in-white (BIW) solutions. A generic vehicle validated for high-speed crash scenarios such as full frontal impact, side deformable barrier impact, side pole impact and rollover (roof crush resistance) is chosen for the feasibility study of developing hybrid lightweight solutions using metals and thermoplastics. Various weight reduction opportunities by either replacing the existing metal reinforcements in the BIW or by replacing a complete sub-system such as B-pillar were explored using metal-plastic hybrid combinations. Developed reinforcements include those in the floor rocker, rails, floor etc. A combination of high heat unfilled thermoplastic resins (tough and ductile) or fiber reinforced thermoplastic resin (high stiffness and strength) and metal are chosen appropriately depending on the requirements. For instance, an unfilled thermoplastic resin over-molded with multiple metallic inserts was chosen to replace the incumbent energy-absorbing members in the floor rocker for side impact, and fiber compounded thermoplastic resin over molded with a metallic insert is chosen to replace the existing B- pillar with comparable crash performance. The developed lightweight hybrid B-pillar replaces a multi-piece B-pillar made of high-strength steel. The metal inserts in the hybrid systems are exploited for assembly ease in the BIW structure. Such a solution not only offers part integration possibilities with equivalent crash performance as that of the baseline system, but also opens the door for replacing the high-strength steel used in the BIW with a medium-strength steel.

A significant weight reduction potential (approximately 30%) is observed as the baseline BIW structures were down-gauged with overmolded thermoplastics. Thermoplastic material overmolded on steel plays a crucial role in avoiding localized buckling of the BIW structures and in absorbing impact energy as and when required. The develo

ed solutions – validated using CAE studies – are further correlated using component level studies with a generic 800 mm long metal-plastic system weight 1.6 kilograms. This system is subjected to 3-point bending and force vs. deflection characteristics and the deformation kinetics in the above loading scenario is correlated using sub-system level CAE studies.