Regulation of automotive CO2 emissions is becoming increasingly stringent throughout the world in response to global warming. For automakers, this means a focus not only on increasing the fuel economy of powertrains, but also on reducing automotive driving resistance. High expectations are held for thermoplastic fiber-reinforced plastics (FRP) for the realization of automotive weight savings while also offering high levels of productivity and recyclability.
Thermoplastic FRP crush boxes display a higher level of energy absorption performance than metal (steel, aluminum, etc.) crush boxes. This will contribute to automotive weight savings and improved package design. In the case of automotive front bumper beam systems, it is necessary to realize stable load characteristics irrespective of the use environment. It is therefore necessary to consider the effects of temperature and thermoplastic resin degradation. The molding process for discontinuous fiber-reinforced FRP produces disordering of the fiber orientation. Research concerning the performance of thermoplastic FRP crush boxes produced findings that assisted in the design of a thermoplastic FRP crush box that would maintain a stable load characteristic in all use environments.
It was found that the temperature-dependency of the compression load characteristic of thermoplastic FRP crush boxes in progressive crushing mode in compression tests is low, and that it is necessary to realize an Euler buckling load higher than the progressive crushing load in order to produce a stable crushing mode. This paper discusses a design method for a thermoplastic FRP crush box based on the above-mentioned conditions in order to realize a stable compression load characteristic, with consideration of the use environment and the effect of fiber orientation.
