Designing vehicle structures using materials with a low carbon footprint

Abstract

The development of modern automotive structures is currently focused on energy optimisation to minimise their negative environmental impact. One of the key trends in this field is the implementation of renewable materials and composites reinforced with natural fibres. This article presents the results of static finite element method (FEM) simulations conducted on a newly designed self-supporting monocoque structure of a prototype vehicle developed for the international Shell Eco-marathon competition. The numerical analysis, carried out using Ansys Mechanical, compares the structural response of the chassis when configured with conventional carbon fibre-reinforced polymer (CFRP) versus a flax-fibre-based biocomposite. The numerical models were defined using orthotropic mechanical parameters determined by the authors through prior experimental testing. The structural analysis under the nominal driver weight demonstrated that a direct 1:1 material substitution results in a drastic, nearly 2.6-fold increase in maximum deformation, thereby disqualifying the structure on the basis of structural stiffness. It was shown that to maintain the monocoque's deflection at a consistent, safe level (below 1 mm), it is necessary to increase the number of flax fibre layers. This modification increases the laminate thickness by 30%, leading to a nearly twofold (91%) increase in the mass of the monocoque itself. The research demonstrated that sustainable materials of natural origin can be used to design a fully compliant and safe load-bearing vehicle structure, provided that their lower specific stiffness is compensated for during the wall-thickness optimisation stage.