1National Highway Traffic Safety Administration, United States of America
Federal Motor Vehicle Safety Standard (FMVSS) No. 226, “Ejection mitigation,” set requirements for ejection mitigation systems to reduce the likelihood of complete and partial ejections of vehicle occupants through side windows during rollovers or side impact events. At the time of the final rule, the agency was not in a position to extend coverage to roof glazing because of the need to research a viable performance test procedure. This paper presents the results of initial assessments of the test as a viable performance test procedure and of the performance of current production roof glazings in preventing occupant ejections.
The assessment of ejection protection offered by laminated glazing roof panels in production vehicles was made primarily using a guided impactor (18 kg) directed toward pre-broken roof glazing from inside the vehicle. Test procedures followed those developed in the FMVSS No. 226 regulation. Test speeds were 16 and 20 km/h (10 and 12.5 mph). Three vehicles with laminated glass sunroofs were selected: a 2008 Ford Flex and a 2013 Ford CMAX, both equipped with a panoramic laminated glass roof that is fixed to the vehicle structure, and a 2013 Subaru Forester with a moveable laminated glass inbuilt sunroof.
When tested at the 16 km/h impact speed, the displacements for both vehicles with fixed glass roof structures were within the 100 mm criterion specified for side windows in FMVSS No. 226, although the results from the Ford Flex were at or just slightly below the criterion. As expected, higher values were seen at the 20 km/h speed. The Ford CMAX displacements were slightly below the criterion, while the Ford Flex exceeded the criterion for all tests conducted at the higher speed. There was no incidence of bonding material failure at the glass/roof structure interface, and no damage was seen to the roof sheet metal in either vehicle. All tests on the Subaru Forester were conducted with the sunroof in the fully closed position, and all displacement values exceeded 100 mm at both test speeds.
The number of vehicle designs tested was limited by the availability of laminated glazing used in production sunroof designs. Extensive vehicle preparation was required to ready them for testing with the impactor used for side window ejection evaluations.