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A variety of energy absorbing foams were evaluated to address the Federal Motor Vehicle Safety Standard (FMVSS) 201 extended rule requirements for automotive interior head impact protection. The methodology used for the comparative study was the “Fast Path System” developed in part by Chrysler Corporation to provide a quick and reliable procedure to compare different materials and designs for energy management. Polyurethane, expanded polypropylene and expanded polystyrene energy absorbing foams were evaluated in this study.

Since 1987 Woodbridge has been engaged in the manufacture of recoverable energy management polyurethane foams. After the development and introduction of our first product we continued our efforts in this field. As part of that development process we adapted a piece of seat testing equipment to small scale impact testing for use in guiding our research activities. As we have worked with different customers, we've found ourselves using different impact head shapes. Clearly the number of geometrical forms and shapes that could be used for testing foamed plastics is infinite. For these reasons we decided to do this study in order to bench mark where we are with respect to impact head shape and the force deflection curves associated with each.

Polyurethane foams developed for interior automotive applications were tested to determine their mechanical responses to uniform dynamic compression. Specimens 50x100x100 mm were compressed to 25%, 50% or 75% strain at nominal strain rates of 0.14/s to 14/s. From 1 to 100 compression cycles were imposed on the specimens. A recovery period was provided between cycles. In all cases, the foam undergoes cyclic softening. The percent reduction in stress response varies with strain, and is greatest at the low strain levels within each compression cycle.