Coupled human body and side impact model to predict thoracic response

Significant advances have been made in automotive safety; however, thoracic injuries resulting from side impact collisions continue to be a leading cause of fatality and severe injury. The goal of this study was to investigate thoracic response in side impact crash conditions using a detailed human thorax model to provide an improved understanding of side impact injury and the primary contributing factors. This study builds on an advanced numerical thorax and human model, which has been validated using available post-mortem human subject test data for pendulum and side sled impact tests. Crash conditions were investigated through the development of a coupled door and seat model to reproduce full-scale crash tests. The model accounts for several important factors that contribute to occupant response as noted in the literature: the relative velocities between the seat and door, the occupant to door distance, door shape, and door compliance. Importantly, the door and seat models were developed using experimental data and the coupled side impact model was validated using Federal Motor Vehicle Safety Standard (FMVSS) 214 and Insurance Institute for Highway Safety (IIHS) side impact test data, comparing the thoracic response predicted by the model to that of the EuroSID-2 (ES-2) dummy used in the crash tests. The side impact model correlated well with the thoracic compression, velocity, and viscous criterion (VC) response of the ES-2 in full-scale crash tests. Finally, the model was used to demonstrate the effects of seat foam stiffness, arm position, and restraint system on thoracic injury. It was found that both the presence of a restraint system as well as stiffer seat foam acted to improve the occupant contact with the seat and reduced thoracic response and the potential for injury. Importantly, it was found that the position of the occupant's arms can contribute to thoracic injury by causing a localised loading of the chest when the arm is aligned with the thorax. Occupant protection in side impact is challenging due to the limited door to occupant spacing associated with lateral collisions. However, the study has shown that there are several factors that may be utilised to further improve occupant safety in side impact collisions.