Improving the fracture toughness of glass/epoxy laminates through intra-yarns hybridisation

Glass fibre reinforced composite laminates have shown poor interlaminar fracture toughness which makes them vulnerable to impact damages; hence, it is essential to improve their fracture toughness and understand the mechanisms of impact energy dissipation. In this study, polypropylene (PP) fibres are mixed with glass fibres at yarn-level hybridisation to enhance the interlaminar fracture toughness of glass/epoxy composite laminates. Composite laminates containing S-glass and hybrid yarns (S-glass and PP) have been manufactured with non-crimp cross-ply preforms using vacuum bagging process. The fracture resistance of laminates with S-glass fibres and hybrid yarns laminates have been evaluated using double cantilever beam (DCB) and end notch flexural (ENF) tests. In addition, the fracture surface analysis was conducted using Scanning Electronic Microscope (SEM). It has been noticed that the yarn-level hybridisation considerably enhanced the mode-I (DCB) and mode-II (ENF) fracture toughness of hybrid laminates compared to that of baseline samples. SEM micrographs of fracture surface illustrated that PP fibre/epoxy de-bonding followed by pull-out of fibre and bridging of fibre has been the effective mechanisms of toughening the hybrid laminates resulting into higher fracture resistance. The results demonstrated that the hybridisation of glass fibres with polypropylene fibres could potentially improve the delamination resistance with the improvement of impact damage tolerance of glass/epoxy laminates.