Development of a novel material for improved crash energy management in collisions involving vulnerable road users

Correctly packaged, foam-filled fluids are a material technology that will lead to enhanced pedestrian safety. It is the combination of energy absorption mechanisms and how this combination can be altered by changes to the properties of the constituent components that provides significant opportunity for tailoring the response of the energy absorber to meet the different demands placed upon it. To date, the research stream has tended to focus on one-factor-at-a-time (OFAT) characterisation in order to develop an understanding of the individual energy absorption mechanisms present in the system. It is unlikely that the full implications of setting the design variables could be understood for such a complex system using an OFAT approach. An experimental design approach to the problem of characterising the response of foam-filled fluids is proposed. To demonstrate the applicability of this approach, the work presented here investigated four process parameters over a limited number of levels. Out of the four parameters, velocity and length were shown to be the significant process parameters determining peak load; velocity and capsule size were shown to be the significant process parameters determining deflection; and viscosity was shown to be the significant process parameter determining absorber efficiency. On the basis of the work presented, a methodology for simultaneous optimisation is proposed that will support the vehicle designer in the development of a foam-filled bumper system. The work is considered timely because of changes in regulations and will support the automotive industry and the requirement to design future vehicles that afford additional protection for pedestrians.