Principal Investigator: Declan Patton, PhD, Children's Hospital of Philadelphia
This study uses impact tests in order to:
- test the strengths of a range of child restraint system support legs using a drop rig to replicate the force time-histories previously obtained from frontal impact sled tests; and
- quantify the strength of underfloor compartments, with and without foam fillers, when loaded with a support leg during drop tests.
WHAT WAS THE PURPOSE OF THIS PROJECT?
CRS support legs, also referred to as load legs, extend from the rear of the CRS to the floor of the vehicle and have been associated with a significant reduction of head injury metrics of pediatric ATDs during sled tests. As some vehicles have underfloor storage compartments in rear rows, there has been concern that installing a CRS with a support leg on top of these compartments may cause the compartment to collapse. The aim of this study was to investigate the strength of support legs from rear-facing (RF) infant CRS models against an underfloor storage compartment, with and without a foam filler, when subjected to loads simulating a frontal crash.
HOW WAS THE RESEARCH CONDUCTED?
We designed a drop test that simulated the vertical forces experienced by the support leg during FMVSS 213 frontal sled tests. An exemplar support leg from a RF infant CRS model was tested at peak reaction forces of 2.5-5.6 kN. Alternate support legs from the three additional RF infant CRS models were tested under the same conditions that resulted in a peak reaction force of 5.6 kN in the exemplar support leg.
The reaction forces measured from these tests were applied via the exemplar support leg to the lids of an underfloor storage compartment across a range of peak reaction forces (2.5-5.6 kN), and residual deformation of the lid was measured. The lids were then loaded using the exemplar support leg for a peak reaction force of 5.6 kN with an expanded polystyrene foam filler placed inside the underfloor storage compartment.
WHAT DID YOU FIND?
The integrity of the exemplar support leg from the RF infant CRS model was maintained during all tests. 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 compressed by 23 mm. In terms of the underfloor storage compartment lid, the residual deformation and the extent of cracking increased with peak reaction force, which we expected. However, the lid did not completely collapse in any of the tests, which has been previously reported as a concern. The foam filler reduced the average residual deformation of the lids by 67%.
HOW ARE THESE RESULTS APPLICABLE TO INDUSTRY MEMBERS?
This is the first study to report the strength of CRS support legs or underfloor storage compartments when loaded by a CRS support leg. Our results demonstrate that a support leg can maintain integrity to effectively reduce the rotation of the CRS during frontal impacts unless it has been intentionally designed to partially collapse and attenuate some of that force. Our results support the recommendation of some vehicle manufacturers that a foam filler be used in an underfloor storage compartment if a CRS with a support leg is installed in the vehicle.
Test setup to measure the reaction force of the support leg using a load cell at the base of the drop rig.
Co-Investigators
Kristy Arbogast, PhD, Children’s Hospital of Philadelphia; Julie Mansfield, PhD, The Ohio State University
IAB Mentors
Emily Thomas, Consumer Reports; Suzanne Johansson, General Motors Holdings, LLC; Mark LaPlante, Graco Children’s Products Inc; Susan Mostofizadeh, American Honda Motor Co., Inc.; Curt Hartenstein, Iron Mountains; Nick Rydberg, Minnesota Health Solutions; Steve Gerhart, Nuna Baby; Anita Sabapathy, UPPAbaby; Uwe Meissner, Technical Advisor