Hierarchical pseudo-ductile hybrid composites combining continuous and highly aligned discontinuous fibres

Hybrid composites allow avoiding catastrophic failure, a key limitation of composite materials, and can provide a balanced suite of modulus, strength and ductility. The aim of this research is to manufacture hierarchical hybrid composites using a combination of continuous high elongation fibres and intermingled hybrids made out of highly aligned discontinuous fibres with lower elongation to achieve pseudo-ductility through control of failure development. The HiPerDiF (High Performance Discontinuous Fibres) method that allows a high level of fibre alignment, leading to excellent mechanical properties close to continuous fibre composites, was used to produce the intermingled hybrid discontinuous fibre preforms. The hierarchical hybrid composite configuration is composed of an intermingled hybrid discontinuous fibre layer sandwiched between continuous S-glass layers. The overall stress-strain response of the intermingled hybrid composites and the hierarchical hybrid composites was investigated for different fibre types and ratios. The analytical modelling approach previously developed by the authors for interlaminated hybrid composites was modified for this new type of hierarchical composite. The experimental results were analysed and the analytical model was used to evaluate the optimised balance of constituents to maximise pseudo-ductile strain in tension.