Development of an innovative design of a composite-sandwich based vehicle roof structure

Obligatory standards are dictated to vehicle manufacturers for decreasing the high number of road dead tolls in rollover crashes; at the same time demands to produce light-weight vehicles have increased substantially to reduce the toxic gases emission. This paper presents a new design of the roof strengthening configuration in which sandwich material has been used. This type of configuration improves the energy-absorption capacity of the vehicle roof system and dissipates impact energy in a controlled manner. In reality, carrying out roof crush test is not cost effective, thus numerical analysis of vehicle roof crush test has been performed according to standard FMVSS 216 test. Sandwich structures with unidirectional carbon/epoxy composite face-sheets and Expanded Polypropylene (EPP) foam core have been used to model different configurations for vehicle roof structure. The effects of increasing the foam core density and face-sheets thickness on the energy absorption and strength-to-weight ratio (SWR) of vehicle roof structure have been investigated. Results revealed that, the optimized sandwich solution type 6 with the face-sheets thickness of 0.8 mm and foam core of 70 kg/m3 density reduces the vehicle roof panel mass by 68% while it has almost the same structural performance with the steel solution having equal value of SWR.