Effectiveness of Polyurethane Foam in Energy Absorbing Structures

Future vehicle safety, performance and fuel economy objectives make the development of new materials, concepts and methods of crash energy management desirable. The technique of foam filling structural rails for increased energy absorption was investigated as one such concept.

A fractional factorial test program was established to evaluate the weight effectiveness of polyurethane foam as an energy absorber and stabilizer. The experiment provided the quantitative effects of design parameter, varability of results and statistical significance of each parameter with regard to crash characteristics.

High density foam was found to be weight effective as a structural reinforcement, but not as an energy absorber. Medium density foam improves the energy absorption of a section. Equivalent energy, however, can be absorbed more weight effectively by changing the metal thickness or the section size. Low density foam proved to be weight ineffective as an energy absorber in typical automotive structures. Regression models were developed which reasonably predict the load capacity and axial collapse of the foam-filled sections.