Effect of Friction Between Head and Airbag Fabric on Ejection Mitigation Performance of Side Curtain Airbag Systems

The Federal Motor Vehicle Safety Standard 226 (FMVSS 226) ejection mitigation standard proposes to measure the performance of ejection mitigation countermeasures (like side curtain airbags) in side impacts and rollovers. An ejection impactor, consisting of a head form attached to a shaft, is propelled at the airbag system at different locations, and the ability of the system to prevent complete or partial ejection out of the side window portals is documented. The friction between the head form and airbag can affect the performance of the airbag to retain the impactor, particularly when the impactor strikes at the bottom of the airbag near the windowsill level. In this study, friction tests were conducted to measure the friction coefficients between a head form scalp material and airbag fabric, human hair and airbag fabric, and human skin and airbag fabric. A series of LS-DYNA Finite Element simulations of the FMVSS 226 tests then were performed to determine the variation in ejection mitigation performance of a side curtain airbag system for the case of the various friction characteristics applied to the head form. The results indicate that the level of friction on the test device head form can influence the ability to pass the FMVSS 226 requirement. In addition, it was found that the friction from Hybrid III skin is substantially higher than human skin or hair on airbag material.