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

The National Highway Traffic Safety Administration (NHTSA) has been conducting biomechanical studies to reduce head injuries sustained during automotive collision. Furthermore, NHTSA added a new regulation to the Federal motor vehicle safety standard FMVSS201, limiting the equivalent head injury criterion (HIC) value to 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 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 upon on the basis of the design of experiments. A series of simulations for head impact to A-pillar trim are carried out by using the explicit finite element (FE) code LS-DYNA3D, and the HIC(d) values are computed using results from simulations utilizing design variables determined by a combination nation of the central composite design and the full factorial design. A proper regression function with an R² value above 0.9 was constructed using the response surface method, and it was used as an objective function for optimization. An HIC(d) value under 850 for 15 mile/h head-trim impact was obtained using the rib structures suggested by the present design methodology.