Composite materials are attractive in aerospace and automotive applications due to their high stiffness-to-weight ratios. Non-crimp-fabric (NCF) reinforced composites have been receiving attention in the composite market due to their cost-effectiveness and excellent mechanical performance. However, compared to traditional unidirectional laminates (UD), NCF composites have different mechanical behaviours due to their heterogeneous internal structures. The ability to predict the mechanical performance of NCF composites is necessary for a robust and reliable design.
The objective of this PhD research was to develop numerical methods to predict the in-plane mechanical behaviour and damage tolerance of the carbon fibre reinforced biaxial NCF composites. The in-plane mechanical behaviours of NCF composites were investigated at different scales by conducting multiscale analyses in the LS-DYNA finite element (FE) software. The macroscopical FE modelling results were validated by a series of in-plane characterisation tests of biaxial NCF composites. The compression-after-impact (CAI) test was adopted to assess the damage tolerance of the composite laminates. The complex failure mechanisms of NCF composites involved in a CAI failure process were comprehensively studied by experimental methods. The experimental results contributed to the validation of FE models to predict the low-velocity impact (LVI) and CAI behaviours of NCF composites in LS-DYNA. Furthermore, different laminate designs were employed to change the CAI behaviour of NCF composites by altering layup sequence and ply-level hybridisation. An optimised scheme was proposed to enhance the CAI behaviour of NCF composites, providing a practical guide to damage tolerance design.