Exploration of Vehicle Body Countermeasures Subjected to High Energy Loading

Enhanced protection against high speed crashes requires more aggressive passive safety countermeasures as compared to what are provided in vehicle structures today. Apart from such collision-related scenarios, high energy explosions, accidentally caused or otherwise, require superior energy-absorbing capability of vehicle body subsystems. A case in point is a passenger vehicle subjected to an underbody blast emanating shock wave energy of military standards. In the current study, assessment of the behavior of a “hollow” countermeasure in the form of a depressed steel false floor panel attached with spot-welds along flanges to a typical predominantly flat floor panel of a car is initially carried out with an explicit LS-DYNA solver. This is followed up with the evaluation of PU (polyurethane) foam-filled and liquid-filled false floor countermeasures. In all cases, a charge is detonated under the false floor subjecting it to a high-energy shock pressure loading. For the case of the liquid-filled countermeasure, a novel ALE (Arbitrary Lagrangian-Eulerian) formulation for fluid-structure interaction has been adopted with a Hybrid III dummy seating above the flat floor with a modified MIL-LX legform for injury prediction. In order to establish confidence on the ALE model, a drop-weight impact test on a liquid-filled square aluminum tube has been carried out and its behavior predicted, prior to the analysis of the countermeasures mentioned. It appears that the fluid-filled countermeasure is a promising solution in countering the effects of a shock pressure loading by greatly reducing the load transferred to the lower limb of an occupant sitting right above a detonated charge placed under the floor of a car.