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Rollover accidents account for a large number of serious to fatal injuries annually. In the past, these injuries were often the result of unrestrained occupant ejection. Subsequent to mandatory belt use laws, a larger percentage of these injuries occur inside the vehicle, and the head and neck areas sustain a substantial number of these injuries. Rollovers have been characterized as violent events, roof crush as the natural consequence of such violence. Further, head and neck injury have been thus considered unavoidable, even with occupant use of the production restraints. This paper will describe the relationship between the three dimensional extent (severity) of roof crush and the equivalent drop test contact velocity as derived from physical experiments and tests. The drop test contact velocity is directly related to the cumulative change of velocity experienced by a vehicle as a result of roof contact deformation during a rollover accident by validated computer simulations.

Experimental results from three point bending and axial compression tests of common automotive roof elements are presented. Modifications of these components were also tested to evaluate the effect of structural reinforcements and void filling. Under three-point bending, an open hat section side header (or side rail) was tested and failed in a manner consistent with observed failures in real world accidents. Modifying the hat section to create a closed section increased load capacity and energy absorption, and demonstrated some gains in strength to weight performance. Two epoxy compounds in a similar closed section configuration resulted in substantial increases in peak load, energy absorption and strength-to-weight ratio. In the axial compression tests, a open “c” section front header were tested in axial compression and failed just past a sheet metal reinforcement consistent with observed failures in real world accidents.