Framework for cost and weight efficient conceptual design of automotive composite body structures

Abstract: The automotive industry is facing a great challenge - reducing the weight of their vehicles. Carbon fibre composites are regarded by many as the only real option as traditional engineering materials are now running out of potential for further weight reduction. In this doctoral thesis a framework is presented which will provide guidelines for the conceptual phase of the development of an automotive composite body structure. The framework is initiated by defining ideal material diversity, as well as initial partition of the body structure based on process and material selection. Then, a further analysis of the structures is made in order to evaluate whether a more cost efficient solution can be found by further dividing the structure. Such a differential design approach is analysed in the third part of the work, studying both the financial and structural effects of such partitioning. In order to increase the understanding of the intimate relationship between design, material and manufacturing process, balancing manufacturing and structural optimization is addressed. Finally, drape simulation tools are used to assess the geometric complexity of composite structures in order to further quantify suitable split lines in cases of differential design approach.Different carbon fibre composite material systems and processes are compared and evaluated in the work. The results show that a high-performance material system with continuous fibres is both more cost and performance effective as compared to industrialised, discontinuous fibre composites. Further analysis shows the importance of balancing the design for manufacturing and the structural weight optimization of the structures in order to reach a cost and weight effective design. When restricting composite design freedom with manufacturing constraints, the great benefits of structural composites disappear and with this both weight and cost effectiveness.