Rapid Determination of Suitable Reinforcement Type in Continuous-Fibre-Reinforced Composites For Multiple Load Cases

With respect to their extraordinary weight-specific mechanical properties, continuous-fibre-reinforced plastics (CoFRP) have drawn increasing attention for use in load bearing structures. Significant effort has been carried out with respect to optimising CoFRP-components for maximum structural performance [1, 2]. Besides conventional optimisation techniques, e.g. topology or thickness optimisation, CoFRPs offer further potential for tailoring to lightweight requirements: Apart from choice of fibre and matrix material, the inherently anisotropic behaviour gives additional design freedom for engineering, e.g. fibre orientation and stacking sequence. Although offering high lightweight potential, determining a robust optimum with CoFRPs is a great challenge, especially, when multiple load cases need to be considered. This work proposes numerical analysis of principal stresses in multiple load cases to assess the lightweight potential when applying CoFRPs. Three common layups are considered: quasi-isotropic (QI) as well as bidirectional (BD) and unidirectional (UD) reinforcement. Principal stresses and their directions are obtained in Finite Element simulations. In extension of previous work [3,4], an algorithm is presented which methodologically determines the most suitable layup-type and orientation for each element across all considered load cases: Thereby, regions are identified, in which UD, BD or QI, respectively, are most favourable. Subsequently, each element per region is accordingly updated with new material properties, the simulations are rerun und the evaluation procedure repeated until convergence. The multi-load-case optimisation results are compared against separate optimisation of each individual load case and found to give meaningful results. The methodology is demonstrated using two generic geometries and one real-world load-bearing component. It is found to reliably allocate most beneficial reinforcement types with low computational effort compared to iterative parameter optimisation algorithms and is thus deemed to facilitate a lean part and process design under consideration of multiple load cases.