Dynamic Impact Testing of Polyurethane Energy Absorbing (EA) Foams

Energy absorbing (EA) materials are used in automobile interiors to help protect occupants from injury in the event of front or side collisions. Depending on their function (shoulder or knee bolster) and location within the automobile (instrument panel or door) different energy absorbing characteristics may be required. Polyurethane (PU) foam is ideally suited for these applications because of its chemical and design versatility and excellent energy absorbing properties.

Routine measurements to characterize EA materials are often performed at relatively low velocity. Collisions which have a high probability of causing occupant injury, however, usually occur at much higher velocities. Because energy managing properties of EA materials can exhibit a dependence on velocity, testing at velocities similar to actual impact velocities is highly desired to accurately characterize a material's performance.

This paper describes a highly versatile, horizontal dynamic impact sled designed by and in use at Miles Inc. to routinely and quickly characterize EA materials at relatively high impact velocities (15 to 56 kph). The application of the sled to characterize the performance of two different types of polyurethane EA foam under various environmental conditions is also presented.