Reduction of CO_2 Emissions through Lightweight Body Panels – Design and Optimization of a SMC Liftgate for the Volkswagen Atlas

摘要

Lightweight strategies are an essential part of Volkswagen’s overall initiative of reducing CO_2 emissions and enhancing customers driving experience. Due to its low material cost combined with established manufacturing technology, steel is the most commonly used material for automotive exterior parts. Unfortunately, steel has a high density, resulting in a relatively low specific strength and stiffness. Glass fiber based sheet molding compound (SMC) provides properties which combine a lower density with specific strength and stiffness to offer great lightweight potential. In comparison to steel, a mass reduction of up to 30% in automotive parts, without limiting functionalities, is possible. By performing a comprehensive simulation study of material characteristics and manufacturing processes, lightweight construction using functional integration and part consolidation is feasible. Utilizing both advantages, it is possible to eliminate separate reinforcement parts (i.e. braces and mounting plates) to further reduce weight and cost. These measures reduce the number of parts, assembly operations, and the number of tools required, reducing overall direct and indirect costs and investments. The Composites Manufacturing & Simulation Center (CMSC) of Purdue University is performing, in cooperation with the North American Engineering & Planning Center of Volkswagen Group of America Inc., the transformation of the current steel liftgate of the Volkswagen Atlas into a lightweight SMC liftgate. The emphasis of the design process is manufacturing-informed performance where manufacturing process simulation is utilized to inform the ultimate performance based on the as-manufactured part. The design and optimization goals are to reach a weight target similar to aluminum, performance comparable to metal, and costs on par with conventional stamping technology. This project marks the first large and complex composite exterior component producible in high volumes for Volkswagen Group of America.