Lightweight concept design of economical FRTP-metal multi-material vehicle doors

The vehicle door, as a major steel-intensive closure, can achieve a certain degree of weight-saving potential by the use of lightweight materials and new design principles. Due to the different stiffness and strength requirements on different areas of vehicle doors under static and crash loading conditions, multi-material construction can be one of the most effective ways to achieve lightweight design with minimal additional cost. This work illustrates an approach for the design of economical lightweight multi-material vehicle door concepts based on a market-available steel reference, while considering typical static and crash loading cases. An innovative door structure is introduced that includes a major load-bearing ring structure and a highly function-integrated inner panel. The structure incorporates economical lightweight materials, such as aluminum, long-fiber thermoplastics, and unidirectional tapes, and corresponding mass-production-oriented manufacturing methods. Anisotropy analysis under different loadings guarantees an effective use of unidirectional tapes. Topology and parameter optimizations provide design suggestions for rib structures of long-fiber-reinforced thermoplastics. The final door concepts achieve ca. 20% weight reduction and comparable mechanical performance compared to the steel reference door. Especially for the crash loading case, an innovative component development method is used to validate the final door concepts, which rebuilds the crash behavior close to the full-vehicle scenario with limited surrounding components.