Abusive Testing of Thermoplastic vs. Steel Bumpers Systems

Over the last decade, on small- and medium-size passenger cars, a new class of front bumper - injection or blow molded from engineering thermoplastics - has been put into production use. These bumper systems provide full 8-km/hr federal pendulum and flat-barrier impact protection, as well as angled barrier protection. Thermoplastic bumpers, offering weight, cost, and manufacturing advantages over conventional steel bumper systems, also provide high surface finish and styling enhancements. However, there remain questions about the durability and engineering applicability of thermoplastic bumper systems to heavier vehicles. This paper presents results of a preliminary study that examines the durability of thermoplastic bumpers drawn from production lots for much lighter compact, and mid-size passenger cars against baseline steel bumper systems currently used on full-size pickup truck and sport-utility vehicles (SUVs). Bumpers were subjected to U.S. FMVSS581 test (at 4 km/hr) and customer abuse testing. A blow-molded polycarbonate/polybutylene terephthalate system for a compact car and a compression-molded glass-mat thermoplastic composite system for a mid-size car showed equal or better dent and deformation resistance than the steel system.