The crush resistance of roof structures is critical to minimizing injuries and enhancing occupant survival during rollover crashes. Federal Motor Vehicle Safety Standard FMVSS 216 requires the roof structure to resist a load equal to one and one half (1&1/2) the unloaded weight of the vehicle during the first 127 millimeters (five inches) of deformation.
This paper discusses the analytical methodologies applied and challenges encountered developing a hybrid Aluminum-Random Chop Material (RCM) roof structure. The roof structure materials are extruded 6260T6 aluminum and RCM. This hybrid roof structure has to satisfy not only the FMVSS 216 roof crush resistance, but also packaging, torsional stiffness and head impact requirements. Due to packaging constraints, the structure has to be developed without the roof bow at the B-pillar level. Head impact and manufacturing requirements, for current architecture and materials, necessitated limiting the inner thickness of the extruded 6260T6 Aluminum pillars, headers and roof side rails to 1.8 mm.
A composite component code COMCOLLAPSE was used in parallel with a stability and strength crush code SECOLLAPSE in the development, design and analysis of the Aluminum-RCM roof structure components. An in-house non-linear beam finite element code VCRUSH was used in the design and analysis of the roof structural system. The newly developed hybrid Aluminum-RCM roof structure exceeded all FMVSS 216 design and certification requirements.