Head-Impact Testing of Polyurethane Energy-Abosrbing (EA) Foams 970160
In August, 1995, the federal government enacted legislation (amendments to Federal Motor Vehicle Safety Standard (FMVSS) No. 201, “Occupant Protection in Interior Impact”) which is designed to improve occupant safety by reducing head and neck injuries received during impacts with the automobile interior. This legislation is significant in that all automobiles, trucks, buses and multipurpose passenger vehicles with a gross vehicle weight rating (GVWR) of 4535 kg (10,000 lb) or less must meet the new federal standard after the 2002 model year.
The testing of potential countermeasures to this legislation (e.g., padding materials and component designs) is key towards developing materials which meet the requirements. As a result, modifications have been made to an in-house dynamic sled impact tester enabling head-impact testing to be performed. This ability allows for the coordinated development, testing and screening of energy-absorbing (EA) polyurethane foams for head-impact protection. These modifications, which are reversible, allow testing under both high-speed dynamic impact as well as head-impact conditions. The new test configuration records the acceleration of a free-motion headform (FMH) undergoing a 6.7 m/s (15 mph) impact with test materials that simulate head impacts with the automobile interior. From this data, HIC(d) values for a variety of foams may be calculated and compared.
The head-impact tester has been used to investigate the impact performance of different types of polyurethane EA foams. Results which compare two different polyurethane foams, a recoverable foam and a rigid foam, will be presented. The dependence of the head-impact properties on foam type, density and thickness as well as foam-cover interactions will also be presented.