Intra-laminar Toughening Mechanisms to Enhance Impact Damage Tolerance of 2D Woven Composite Laminates via Yarn-level Fibre Hybridisation and Fibre Architecture

Advanced composites are widely used in primary and secondary structural applications, e.g. aerospace, automotive, marine and renewable energy sectors. But it is well recognised that the impact resistance and damage tolerance of composite laminates are in general poor, which is a major challenge for optimising structural designs. In this regard, an experimental study is conducted for enhancing the damage tolerance of 2D woven composite laminates by exploring yarn-level fibre hybridisation. Hybrid yarns are produced by combing high-strength fibres, i.e. S-glass, and high-toughness fibres, i.e. polypropylene (PP), and using commingling and core-wrapping processes. Using the hybrid yarns, 2D fabrics, i.e. with 5H satin, 2/2 twill and 2/2 basket architectures, are weaved, and subsequently hybrid S-glass/PP/epoxy laminates are manufactured via vacuum assisted resin infusion. The low velocity impact response and energy absorption of the hybrid laminates are investigated by drop-weight impact tests at different energy levels, i.e. 15 J, 25 J, 35 J and 50 J. The damage tolerance is studied by compression-after-impact (CAI) tests, measuring the residual compressive strength of the damaged laminates. Furthermore, the failure modes are investigated using scanning electron microscopy for identifying damage mechanisms in the hybrid laminates after the impact and CAI tests. The impact response and damage tolerance of the 5H satin, 2/2 twill and 2/2 basket fabric laminates are compared with that of non-crimp-fabric laminates produced with (i.e. S-glass/PP yarns) and without (i.e. S-glass yarns) yarn-level hybridisation. It is shown that yarn-level hybridization and fibre architecture significantly affect the impact behaviour and damage tolerance of the 2D woven S-glass/PP/epoxy hybrid laminates investigated. The microscopy studies show that intra-yarn, inter-yarn, inter-lamina failure mechanisms can in general be introduced by combining yarn-level fibre hybridisation and fibre architecture for modifying failure and energy dissipation mechanisms under low velocity impact and hence the damage tolerance of composite laminates.