There are several key issues to consider when designing a bumper system within today's automotive environment. These include impact efficiency, corporate average fuel economy (CAFE), federal requirements, and independent consumer agency requirements. Impact efficiency of a bumper system is critical for three reasons. First, it enables vehicles to absorb more energy in less packaging space. Second, with CAFE a high priority, thermoplastic bumper systems provide an excellent opportunity to reduce vehicle mass, and improve CAFE ratings when they replace conventional steel foam systems. Finally, the system needs to meet Federal Motor Vehicle Safety Standards (FMVSS) part 581 and Insurance Institute for Highway Safety (IIHS) requirements. The bumper system described in this paper offers the ability to achieve each of these goals and remain cost competitive.
This bumper system is comprised of a compression molded glass mat thermoplastic (GMT) (AZDEL ® C507® composite) I-beam bumper section that is coupled with a thermoplastic polycarbonate / polybutylene teraphthalate (PC/PBT) energy absorber (EA). The inherent strength-to-weight ratio of the I- beam [1, 2] provides an exceptional reaction surface for a PC/PBT injection molded energy absorber. The strength of the I-beam along with the tunable crush cans of the PC/PBT energy absorber [3] result in a highly efficient, fast loading, controlled impact event. Furthermore, the increased stiffness enables automotive designers to reduce vehicle bumper offsets. Also, this system can enable part integration, reduce complexity, and provide consistent performance over the automotive temperature range. Overall, the I-beam/EA combination can give rise to a lightweight, impact efficient, cost-effective system that not only meets FMVSS and IIHS requirements, but also maintains the ability to be packaged in the aggressive styling of today's vehicles.