Design and development of automotive bumper subsystem for lightweight and vehicular crashworthiness

Reducing fuel consumption, satisfying the current regulations regarding GHG emissions and customer safety requirements are the main targets for automotive industries. Today, the research and development departments of car industries are trying to address such issues by substituting the traditional steel components with lightweight advanced composite materials. However, the complexity of composite failure behavior for impact loading and the trade-off between vehicle weight and crashworthiness make the change from metallic to composite materials very difficult and remains the main obstacle for their rapid development. With the current die forming and injection over-molding technologies, open composite beam shells can be structurally can be integrated with the crash box. Therefore, if the strength/stiffness of an open structure can be maintained, the capability of component integration will offer a reduction in the number of parts, increase the production rate and reduce the number of mechanical joints. It is obvious that, open-channel thin-wall beam is structurally weak and can readily buckle under lateral and compressive loads. However, with very little lateral support, provided by a thin-wall rib-like injection-molded plastic sub-component, the buckling and bending stiffness can be improved. In the current study, three composite materials are considered for a lightweight automotive bumper beam and better crashworthiness. The rib pattern selection, beam end section and geometry optimization have been conducted numerically. A low velocity impact test was carried out and four parameters, such as impact energy, peak load, crash resistance and energy absorption were taken as evaluation criteria to compare the materials proposed with steel solutions. The results show that with a proper end section, rib geometry optimization and reinforcement rib selection, an open section beam can yield a structural performance comparable with that of a closed section beam