Cost and weight effective composite design of automotive body structures

Abstract: The automotive industry stands in front of a great challenge, to decrease its impact on the environment. One important part in succeeding with this is to decrease the structural weight of the body structure and by that the fuel consumption or the required battery power. Carbon fibre composites are by many seen as the only real option when traditional engineering materials are running out of potential for further weight reduction. However, the automotive industry lacks experience working with structural composites and the methods for high volume composite manufacturing are immature. The development of a composite automotive body structure, therefore, needs methods to support and guide the conceptual work to improve the financial and technical results.In this thesis a framework is presented which will provide guidelines for the conceptual phase of the development of an automotive body structure. The framework follows two main paths, one to strive for the ideal material diversity, which also defines an initial partition of the body structure based on the process and material selection. Secondly, a further analysis of the structures are made to evaluate if a more cost and weight efficient solution can be found by a more differential design and by that define the ideal part size.In the case and parameter studies performed, different carbon fibre composite material systems and processes are compared and evaluated. The results show that high performance material system with continuous fibres becomes bothmore cost and performance effective compared to industrialised discontinuous fibre composites. But also that cycle times, sometimes, are less important than a competitive feedstock cost for a manufacturing process. When furtheranalysing the manufacturing design of the structures it is seen that further partition(s) can become cost effective if the size and complexity is large enough.