Abstract
A combined experimental and computational study on the fatigue of glass-fibre reinforced
polymers (GFRP) is presented, with particular emphasis on the effects of water saturation,
for use in ocean energy structures. The experimental characterisation consisted (i) of
immersion-aging of test specimens for a period of up to two years, using a moderate
accelerated aging technique, designed to simulate longer-term seawater exposure of the
material, and (ii) fatigue testing of aged and unaged specimens in immersed and nonimmersed conditions, with emphasis on identification of fatigue damage evolution. The
computational methodology incorporates the development of a multiaxial fatigue damage
user material subroutine, based on the static Puck approach, adapted for fatigue by
combining (i) fatigue-induced fibre strength and modulus degradation, (ii) irrecoverable
cyclic strain effects and (iii) inter-fibre fatigue. Finally the impact of water saturation on the
fatigue life of a tidal turbine blade is assessed using a fatigue life model.