Optimum design of an A-pillar trim with rib structures for occupant head protection

NHTSA (National Highway Traffic Safety Administration) has been conducting biomechanical studies to reduce head injuries sustained during automotive collision. Furthermore, NHTSA added the new regulation to the FMVSS201 (Federal Motor Vehicle Safety Standard), limiting the equivalent HIC(Head Injury Criterion) value under 1000. In the present study, a methodology is developed for the optimum design of the A-pillar trim with rib structures, which can maximize the energy dissipation during the head impact. The design variables for the rib structures are the transverse spacing, the longitudinal spacing, and the thickness. The required set of design variables is decided on the bases of the design of experiments. A series of simulations for head impact to A-pillar trim are carried out by using the LS-DYNA3D, and the HIC(d) values are computed using results from simulations, which utilize design variables determined by a combination of the central composite design and the full factorial design. A proper regression function with R-square value above 0.9 was constructed using the response surface method, and it was used as an objective function for optimization. A HIC(d) value under 850 for 15mph head-trim impact was obtained using the rib structures suggested by the present design methodology.