Strength of an underfloor storage compartment when loaded with a support leg during a frontal crash.

Objective: To investigate the strength of support legs from rearward-facing infant CRS models and the strength of an underfloor storage compartment, with and without a foam filler, when subjected to loading by a support leg simulating a frontal crash.

Methods: A range of support leg normal reaction force time-histories from previous frontal sled tests were simulated using a drop test rig with an impact mass of 39.4 kg. An exemplar support leg from a rearward-facing infant CRS model was tested across a range of drop heights (135-360 mm) and the reaction force was measured. Support legs from three alternate rearward-facing infant CRS models were tested at a drop height of 310 mm and the reaction force was measured. The reaction forces measured from these tests were applied the exemplar support leg to the lids of an underfloor storage compartment across a range of drop heights (135-310 mm) and residual deformation was measured. Lids were subsequently loaded using the exemplar support leg for a drop height of 310 mm with an expanded polystyrene (EPS) foam filler placed inside the underfloor storage compartment.

Results: The integrity of the exemplar support leg from the rearward-facing infant CRS model was maintained during all tests, including tests up to a peak reaction force of 7.9 kN. For a drop height of 310 mm, the support legs from two alternate CRS models performed similarly to the exemplar leg; however, the support leg from the third alternate CRS model was observed post-test to have compressed by 23 mm. The underfloor storage compartment lid deformed plastically when loaded with a support leg and residual deformation increased proportionally with drop height. The extent of cracking of the lid also increased with drop height. The foam filler reduced the average residual deformation of the lids by 67%.

Conclusions: Although the underfloor storage compartment lids deformed plastically when loaded with a support leg, no lid completely collapsed in any of the tests. The foam filler effectively reduced deformation of the lid, the use of which is recommended when a rearward-facing CRS with a support leg is being used in a vehicle with an underfloor storage compartment. The results of the current study may have implications for electric vehicles, which have unique floor designs to accommodate battery packs and other components.