Improving interlaminar properties of woven carbon fibre composite laminates with industrial-scale carbon nanotube fibre interleaves

This work introduces a method to fabricate carbon nanotube fibre veils on woven carbon fibre/epoxy composite laminates and analyses the role of interleaf thickness and degree of infiltration on interlaminar properties. The interlaminar fracture toughness (IFT) under mode I and mode II loading conditions are investigated and discussed comparatively, followed by a systematic analysis of failure and toughening mechanisms. The experimental results revealed that the toughening effects of CNT veils depend highly on their thickness and degree of resin infiltration observed by electron microscopy and Raman spectroscopy. The propagation value of mode I interlaminar fracture toughness (G(IC,prop)) increased as much as 77 % and 76 % after interleaving CNT veils with a thickness of 5 and 10 mu m, but strikingly dropped by 36 % as the thickness of the CNT veils reached up to 15 mu m. In comparison, the mode II fracture toughness (G(IIC)) improved continuously with increasing the thickness of CNT veils. The figure of merit for interlaminar reinforcement, consisting of the change in interlaminar properties normalised by interleaf thickness and ply thickness, comes out as high as 58.5, which is an order of magnitude above the state-of-the-art.