Finite Element Investigation of Seatbelt Systems for Improving Occupant Protection during Rollover Crashes 2009-01-0825

The seatbelt system, originally designed for protecting occupants in frontal crashes, has been reported to be inadequate for preventing occupant head-to-roof contact during rollover crashes. To improve the effectiveness of seatbelt systems in rollovers, in this study, we reviewed previous literature and proposed vertical head excursion corridors during static inversion and dynamic rolling tests for human and Hybrid III dummy. Finite element models of a human and a dummy were integrated with restraint system models and validated against the proposed test corridors. Simulations were then conducted to investigate the effects of varying design factors for a three-point seatbelt on vertical head excursions of the occupant during rollovers. It was found that there were two contributing parts of vertical head excursions during dynamic rolling conditions. Part I was induced by stretching of the seatbelt due to the inertia of the occupant, and part II was induced by the lap belt rotation about its anchor point. Simulation results demonstrated that reducing the initial slack of the seatbelt, adding a pretensioner, and changing the sliding latch plate to cinching latch plate could effectively limit the part I head excursion. Changing the lap belt to a more vertical angle and reducing the clearance between the occupant and seatback could effectively limit the part II head excursion. The effectiveness of some new seatbelt designs in rollovers, such as 3+2-point seatbelt, H-type 4-point seatbelt, and double-lap seatbelt, were also evaluated in this study.