Immersed fatigue performance of glass fibre-reinforced composites for tidal turbine blade applications

This work presents an experimental study on the fatigue of glass fibre-reinforced polymers (GFRP) for use in ocean energy structures, with particular emphasis on the effects of water saturation. Quasi-isotropic specimens with either epoxy or vinyl-ester matrix were reinforced with E-glass or E-CR glass and immersion-aged for a period of up to two and a half years, using a moderately accelerated ageing technique. A number of the specimens were kept under constant tensile stress while immersed. The water-saturated specimens were fatigue tested while immersed in water. Dry specimens of the same materials were also fatigue tested and comparative results are presented. It was established that moisture saturation has a detrimental stress-dependent effect on the fatigue strength of the epoxy/E-glass composite. The measured evolution of specimen stiffness during the fatigue cycles was similar for both dry and water-saturated coupons.