Electronic Thesis/Dissertation


Evaluation of composites for light-weighting of highly loaded components in dynamic impacts of vehicles. Open Access

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Nowadays car manufacturers face the challenge of reducing the weight of their vehicles for an increased efficiency on the one side but also improve the crash performance on the other side. Materials which provide the potential to fulfill both criteria, a low density as well as a high ability to absorb energy are fiber reinforced composites. This study investigates the potential of composites as a substitution material for highly loaded components in frontal crashes to reduce the weight but keep or improve the crashworthiness of the vehicle.Basis of the investigations is the FE model of a 2010 Toyota Yaris Hatchback which was validated for the National Highway Traffic Safety Administration (NHTSA) frontal crash test procedure by the National Crash Analysis Center (NCAC). Two beams composed of eight components which absorb the most energy in a frontal crash were evaluated in detail with the help of the Finite Element Method (FEM). In fact, the behavior of the components was compared between the original materials and triaxially braided composite material with a varying number of layers.First, component-level and assembly-level simulations proved the fundamental ability of composites to provide the same stiffness and absorb the same energy like the original materials. Although the process of failure is completely different, an increase of the thickness between 2 and 2.5 times corresponds to six or seven layers of the composite resulted in the same external work that was needed to reach a certain displacement. The increase of the stiffness does not differ significantly between different components or assemblies.In a second step, full-scale simulations of the model proved the insights of the component- and assembly-level simulations. Substitutions of the highly loaded components with composite material and an increase in the thickness of around two times which corresponds to six layers of composite material resulted in comparable stiffness of the model and even lower intrusions in the occupant compartment. Although, the components have to be thicker to maintain the crash performance, the weight of the two beams can be reduced by 60.1 % and the overall vehicle weight by 0.53 % with the help of composites.In conclusion, fiber reinforced composites are able to provide significant benefits in light weighting a vehicle without negative impacts on the crash performance. In fact, the crash worthiness of the vehicle benefits of the use of composite materials. Since this study focused on substituting materials without changes of the geometry, results of this study can be considered in future developments without huge design changes.

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