The effect of hygrothermal ageing on the delamination of Carbon/epoxy laminates with Core-shell rubber nanoparticle and Micro-fibre thermoplastic veil toughening

This work investigates the effect of hygrothermal ageing on the interlaminar fracture of carbon fibre/epoxy composite laminates with (i) core-shell rubber nanoparticle toughening, (ii) micro-fibre non-woven thermoplastic veil toughening, and (iii) hybrid nanoparticle and veil toughening. The untoughened and toughened carbon fibre/epoxy composite laminates are manufactured by resin infusion of a unidirectional non-crimp carbon fabric and a two-part epoxy matrix with out-of-autoclave curing. Core-shell rubber nanoparticles with 100 nm to 3 & mu;m diameters are mixed in the epoxy resin at a 10 wt% content for matrix toughening. Thermoplastic veils with - 20 g/m2 made of short micro-fibres (i.e. polyphenylene sulfide fibres with - 6 mm in length and - 9 & mu;m diameter) are used for interlaminar toughening. Double cantilever beam and end-notch flexure fracture tests are conducted with completely dry, moisture saturated and re-dried laminate conditions. The results show that the Mode-I and Mode-II fracture behaviour (i.e. R-curves, fracture energies, and crack paths) of the baseline and toughened laminates by nanoparticles and veils are considerably affected by hygrothermal ageing. In the case of veil toughening and hybrid nanoparticle and veil toughening, it is found that the Mode-I and Mode-II fracture energies are considerably degraded, yet the interlaminar fracture response of the toughened laminates is superior to that of the untoughened dry laminates. In addition, the carbon/epoxy laminates with hybrid nanoparticle and veil toughening have further decreased fracture energies-rather than restored-after redrying, which indicates that the degradation due to hygrothermal ageing is irreversible.

Automated summary

This study investigates the impact of hygrothermal ageing on interlaminar fracture of carbon fibre/epoxy composite laminates with different toughening methods. The results show that hygrothermal ageing significantly affects the fracture behavior of baseline and toughened laminates. In particular, the fracture energies of laminates with veil toughening and hybrid nanoparticle and veil toughening are considerably degraded and cannot be restored after re-drying, indicating the irreversible degradation caused by hygrothermal ageing.