Light-Weight-Design: Detailed Comparison of Roof Panel Solutions at Crash and Stiffness Analyses

In the recent years, due to the enforcement of new EU normative, the interest of all the car manufacturers in producing light-weight vehicles is progressively increased as the combustion engine optimization has already used all improvement margins they had. Base on this auto industry interest, composite materials have absorbed lots of attention due to their superior characteristics. In this paper, a finite element model has been developed, starting from the available Toyota Yaris model, for evaluating the response of vehicle in case of full frontal crash and measuring the static stiffness and modal analysis of vehicle body with specific focus on roof panel material solutions. These analyses will help to have a broad view to compare the stiffness contribution of composite roof panel in crash analysis. The roof panel modeling is carried out in both explicit and implicit finite element code LS-DYNA (for crash and stiffness analyses respectively) with three material solutions of steel (that being the normal production solution will be used as the reference), aluminum and composite with the same thickness and modified thickness. MAT 24 "Piecewise Linear Plasticity" is applied to model the steel and aluminum roof panels and MAT 54 "Enhanced Composite Damage" along with the Chang-Chang and strain based failure criteria is utilized to model the composite roof panels. Results of crash analysis for the determined sections reveal that, although composite solutions have lower longitudinal deformations and energy absorption due to their lower compressive stiffness, performance are very close to the traditional solutions. Therefore, composite materials constitute an interesting solution in respect to mass reduction. Results of stiffness analysis reveal that composite roof panels have acceptable effect on the total body stiffness values and modal frequencies in comparison with the steel and aluminum ones and can be a good substitute for the traditional solution