Abstract
Interest in tidal power is continuously increasing due to its huge potential for reliable renewable energy generation. This has led to the emergence of tidal turbine designs often inspired from earlier developments in the wind turbine industry. Composite materials including Glass fibre reinforced polymers (GFRP) are a low-cost, low weight and corrosion resistant material for this application. Cyclic loading due to tidal flow and wave conditions is a common characteristic of tidal turbine devices and the good fatigue performance of composite materials means they are widely used, however limited information are available to predict material behaviour under coupled environmental and cyclic loading. This problem is addressed in this paper, by introducing a methodology for prediction of the fatigue behaviour of composite tidal turbine blades. The methodology combines: (a) a hydrodynamic model for calculation of distributions of fluid–blade forces; (b) a finite element structural model for prediction of mechanical and fatigue behaviour of blade and (c) performing cyclic and quasi static tests at the material scale in the environment of sea water to generate realistic data for modelling. To ensure the fatigue failure criterion is reasonable the fatigue failure mechanisms in test samples were investigated via microscopic techniques and it was found that inter-laminar cracks, delamination and breakage of fibres that run through the thickness direction of composites dominate the fatigue failure