Evaluation of the Benefit of Energy-Absorbing Material in Side impact Protection: Part I

This paper presents a methodology to link reductions in biomechanical responses due to force-limiting material to projections of injury mitigation in real-world side impact crashes, and to use this approach to evaluate the potential injury reducing benefit for the chest and abdomen of constant crush force material in the side door and armrest. Using a simulation of the human impact response, a range in crush force was determined which effectively reduced a peak biomechanical response from that obtained with a rigid impact. The range in constant crush force depended on the velocity of impact. The higher the velocity of impact, the higher the level of crush force to achieve a reduction in the peak response. NCSS field accident data for car-to-car side impacts provided information on the occupant exposure and injury as a function of the change in velocity (ΔV) of the struck vehicle. Based on various experimental studies, the velocity of the side door at contact with the occupant's chest is similar to the ΔV of the struck vehicle (about 60% of the closing speed of the striking vehicle). The chest impact velocity in the simulation was assumed equal to the observed ΔV in the NCSS data. This related the simulation data to real-world injury data. Reductions in biomechanical response were related to lower injury risk. This enabled a calculation of a reduction in injured occupants assuming an equivalent reduction in real-world injury risk for the velocity range in which the EA material was effective. The greatest reductions in seriously injured occupants were found with a relatively soft constant crush force EA material which is effective in low-speed (ΔV = 4-8 m/s) crashes, whereas padding of this type was negligibly effective in high-speed crashes (ΔV > 10 m/s).