LS-DYNA Study of the Innovative Concepts of Engine Bonnets to Improve the Passive Safety of Head Impact

Pedestrian protection is one development issue where up-frontloading is essential. Bringing in new innovative ideas, based on analytical approaches and parameter studies, which would allow checking the efficiency of the concept even before the CAD work starts, leads to a good head start. LS-Dyna can be used as one tool to carry out such fundamental examinations. This presentation starts by providing an update on pedestrian protection, giving a brief overview of head impact legislation and the head injury criterion. Afterwards, a simplified analytical approach is used to give an idea of a minimum HIC value depending on the bonnet shape and clearance below the bonnet. Then a first parameter study aims to find the main factors for the head impact related values, examining first a simple steel plate and then a flat sandwich panel. The study then continues to evaluate an innovative sandwich concept for engine bonnets. Several materials and various designs of sandwich bonnets are reviewed, constituting the issue of the next step of the parameter study. Comparison of such results to a standard steel concept shows the advantage of having a smooth distribution of the values throughout the bonnet surface, a slight improvement in HIC and an important reduction in weight.