ANALYTICAL EVALUATION OF AN ADVANCED INTEGRATED SAFETY SEAT DESIGN IN FRONTAL, REAR, SIDE, AND ROLLOVER CRASHES 2001-06-0017

Analytical computer simulations were used to optimize and fabricate an Advanced Integrated Safety Seat (AISS) for frontal, rear, side, and rollover crash protection. The AISS restraint features included: dual linear recliners, pyrotechnic lap belt pretensioner, 4 kN load-limiter, extended head restraint system, rear impact energy absorber, seat-integrated belt system, and side impact air bag system. The evaluation and optimization of the AISS design was achieved through analytical simulations using MADYMO multi-body analysis software, LS-DYNA3D finite element software, and through LS-DYNA3D/MADYMO coupling. Frontal and rear impact sled tests were also conducted with physical AISS prototypes and baseline integrated seats to verify performance.

Both the analytical modeling and the experimental sled testing demonstrated safety improvements over the baseline integrated seat. The AISS pyrotechnic lap belt pretensioner and 4 kN load-limiter contributed to a 26 percent reduction in occupant chest acceleration in the frontal impact mode. In the rear impact mode, the AISS dual linear recliners, rear impact energy absorber and extended head restraint system contributed to reducing the occupant upper neck injury parameters. Full vehicle finite element models were used in both the side impact and rollover simulations to evaluate occupant restraint performance. Two generic AISS restraint features were modeled for side impact protection: an inflatable tubular cushion air bag system and a combination head/thorax side impact air bag system. The combination head/thorax side impact air bag system model was found to provide improved occupant protection due to its ability to cover both head and thorax regions and provided a softer reaction surface for the occupant. Upper and lower rib Thoracic Trauma Index (TTI) were reduced 22.1 percent and 14.8 percent, respectively in the side impact simulations. The AISS extended head restraint, pyrotechnic lap belt pretensioner, and seat-integrated belt system also provided benefit in restraining the occupant and minimizing roof crush in the rollover simulations.