Developing car structures to provide improved car occupant protection.

This article discusses the impact characteristics of both frontal and side collisions and the role that car design plays in providing occupant protection. Most severe and fatal injuries are caused by contact with parts of the car interior, and cars are not tested to withstand the type of frontal impact that normally occurs. Currently the only legislative tests for passenger compartment integrity rely on a perpendicular impact to a rigid wall. This type of impact has very different characteristics from what is normally occurring in accidents. In frontal impacts it is usually only part of the car's front that is impacted. Cars usually hit a non rigid object like another car, and impact loads are not usually parallel with the longitudinal structure members. All these factors decrease the energy absorption potential of the front structure in comparison with a symmetrical impact, thus increasing the likelihood of the collapse of the passenger compartment. In side impacts, injury occurs 15-25 m sec after the start of the impact and experience with the EUROSID dummy has shown that all parameters used to estimate injury severity have peaked by 50 m sec. Door dynamics, load paths, door intrusion paths and the effect of door padding to decrease injury are all discussed.