Abdominal and thoracic response to loading of pretensioner restraint systems

A better coupling of the occupant to the car seat in the early phase of a frontal crash using pretensioner systems may potentially avoid head-vehicle contact and reduces the likelihood of the submarining effect. However, the high belt forces developed during pre-tensioning may also increase the risk of abdominal injuries to the vehicle occupant. The main objective of this study was to investigate the biomechanical response and injury outcome to the thorax and the abdominal regions in static deployment tests using two pre-tensioner systems. Four post-mortem human specimens (PMHS) were positioned in production seats in a normal passenger position and were restrained using a standard three-point belt system. The pretension forces in the belts were generated at two points (retractor and right anchorage) or at all three locations (retractor, left anchorage and right anchorage). The normalized deflections of the thorax recorded at the level of fourth rib were under 10% (non-injury level). An optical motion capture system and acceleration cubes mounted to the lumbar spine were used to measure the abdomen deformation during testing. Two different patterns were observed in the time histories of abdominal penetration rate in the four PMHSs, associated with lower and higher Body Mass Index (BMI). Abdominal injuries (spleen lacerations) were observed in two PMHS with higher BMI. Using data from this study and similar data from the literature, belt velocity and FmaxCmax were shown to be the best injury predictors for injury risk analysis for AIS 2+ and for AIS 3+ injuries, respectively.