All-terrain vehicle chassis design using multi-material topology optimization

There has been a significant surge in the demand for electric all-terrain vehicles (eATV) recently due to a rising number of government subsidies for electric vehicles, better availability of charging infrastructure, and the increasing need to minimize the level of greenhouse gas emissions. To address this growing demand and enhance the overall performance of new ATV architectures, automakers are looking to develop new lightweight chassis designs with the application of multi-material parts, assemblies, and systems. To achieve these goals, conventional material selection and design strategies may be employed, such as standard material performance indices, full-combinatorial substitution studies, or recently developed multi-material topology optimization (MMTO). In this paper, a prototype design for a lightweight eATV chassis using titanium, aluminium, and carbon fibre sheet moulding compound is developed using a novel design process. The design space for the MMTO design is developed from the baseline steel chassis design. The proposed design process reduces the time required to design an eATV chassis significantly as it reduces the number of design update iterations by efficiently modelling the material interface. The process utilizes MMTO considering total joint cost (TJC) constraints to refine the chassis design and reduce the material interface. This method allows for simultaneously minimizing the compliance as well as restricting the TJC of the structure which is calculated based on the user-defined relative costs for each material interface. This reduces the number of iterations between design update and validation as the performance of the prototype design would be more in line with the design considering actual joint material properties than considering the MMTO design without TJC constraint. A Pareto front is created to determine the trade-off between the two competing functions. It was observed that an 80% reduction in TJC can be obtained in the eATV chassis design with only a 4.2% loss in stiffness, as compared to an MMTO design without joint considerations. Both this final design and the single-material topology optimization (SMTO) design considering titanium were reinterpreted into a practical concept and analysed. The final selected MMTO design is 32% lighter than the baseline steel chassis design, with a stiffness increase of 64%.