Optimeringsmetoder för ASMC-strukturer

Sammanfattning: Thin metal sheets have for long been the dominant structural components in automotive bodies, but as environmental concerns mount new materials are needed to reduce mass. Advanced Sheet Moulding Compounds (ASMC) is a carbon fibre composite with short fibres and has been put forward as an alternative. It is both light and has good durability and can be formed in a mould similarly to steel sheets. A distinct advantage is that unlike for steel sheets the thickness in an ASMC component can be varied and stiffeners integrated. This creates great opportunities for optimisation, but as know-how in the industry is scarce a methodology is necessary. This master’s thesis describes a method developed for optimising structural components manufactured in ASMC by analysing a backplate mounted in a Body-In-White (BIW). The optimisation design process was first developed in a simplified model made to mimic a BIW without all the complexities therein. In this thesis free-size optimisation was done individually and coupled with adding uni-directional (UD) fibres and ribs to the backplate. This process was then verified in an accurate car body model and the process translated rather well to a more realistic model as favourable results were obtained. Optimisation resulted in more than 50% decrease in the component’s mass and body torsional stiffness could be increased by up to 7%. A step-by-step guide for this process is presented. Moving forward the design methodology needs to be verified and developed further for different structures and load cases. It is believed that the process detailed works well for many different structures as is, but improvements can be made and are ultimately necessary.