Design Development of Energy Absorbing Ribs for Meeting FMVSS 201 Extended Head Impact

Revisions to the FMVSS 201 head impact legislation have had a significant impact on the design and engineering of upper interior trim components of cars and light trucks. Structural performance with energy absorbing capability to prevent head injury is now a significant addition to these requirements. However, occupant visibility blockage limits the amount of packaging space available for implementing countermeasures in this area.

A novel approach to meeting the FMVSS 201 structural requirements, while keeping the interior trim on the vehicle minimally changed, has been developed. This approach requires the use of energy absorbing rib structures sandwiched between the trim panel and the inner body-in-white (B/W) sheet metal in A and B pillars. Heat staking is used to attach the rib structure to the interior trim panel. This design approach provides flexibility, particularly so for vehicle platforms that will be manufactured and sold in markets where no provision for head impact protection is required. In such cases, the same trim panel design can be used with no modifications, and the rib cartridge can be selectively included in those vehicles to be sold in North America.

Finite element (FE) models of all surrounding B/W structures were built to simulate the compliance of the entire system. Non-linear FE analysis was extensively used to develop the optimum design of the rib cartridge structure. High speed, true-stress/true-strain data were generated for the different materials used to obtain a fair degree of accuracy and correlation between the analytical simulation and testing. The FE analysis results indicate the rib cartridge system is able to meet the FMVSS 201 requirements.