The effects of cost and weight efficient structural design for manufacturing of composite automotive body structures

The automotive industry stands in front of a technology shift in order to adapt to future legislations on more energy efficient cars. Carbon fibre composites are by many seen as the only solution to succeed with this quest. Composite design and manufacturing methodologies need to be developed in order to reach a cost and weight effective design for high annual volumes. Potential advantages with composite materials, such as enabling manufacturing of highly integrated structures with complex geometries, i.e. integral designs, must be explored and questioned. In high series volumes, differential designs, i.e. structures divided with the intention of reducing the part complexity, seems to become more competitive. In this work the effect on financial and structural performance of differential and integral design solutions are addressed. Constraints on laminate and ply thickness as well as minimum ply cut area are considered and their impact on the weight optimisation evaluated. An automotive body structure section is studied and the weight and manufacturing cost is evaluated for both integral and differential design solutions. A cost model addressing both manufacturing and assembly processes are used together with finite element optimisation for the analysis. The results show that the weight efficiency for all design solutions is greatly reduced if the partitioning is made with of a clear focus. The results emphasise the importance of an efficient partitioning philosophy if the advantages of differential design are to be experienced to its fullest and to be able to create a manufacturing optimised design offering both cost and weight efficiency.QC 20220208