Analysis of Different Countermeasures in Response to FMVSS 201 Upper Interior Head Impact Protection and A Comparison Study on the Injury Parameters and Energy Absorption

In response to Federal Motor Vehicle Safety Standards (FMVSS) 201 upper interior head impact protection, development of a suitable countermeasure has become an important aspect. FMVSS 201 safety regulation stipulates that the Head Injury Criterion, HIC (d) should be less than 1000 when a FMH is impacted at a speed of 15 mph. The interior components of a vehicle generally do not generate high HIC (d) numbers by themselves but the steel structures behind them to which they are attached do so. The gap between the interior component and the steel structure makes a provision for the introduction of some countermeasures which can absorb the kinetic energy of the FMH in the form of internal energy so that the acceleration response of the FMH does not generate high HIC (d) and Peak G force. This paper discusses the analysis of different countermeasures using a dynamic finite element tool LS-DYNA for automotive interior components to comply with FMVSS 201 requirements. The effectiveness of introducing a countermeasure between the headliner and the steel structure or the body in white (BIW) is evaluated. Several materials for the countermeasure have been analyzed and a comparison is made in terms of injury parameters, HIC (d) and Peak G. Comparison is also made for the energy absorption by the different countermeasures. Several geometric configurations of the countermeasure have been studied to ascertain its suitability in absorbing the kinetic energy of the FMH. Parametric studies have been carried out by varying the thickness of the countermeasure to see the effect on the injury parameters, HIC (d) and Peak G. Finite element analysis results match very closely with the test results as per the FMVSS 201 regulations which makes it possible to design an effective countermeasure.