Understanding the fatigue behavior of tidal turbine blades

Global warming and subsequently its effects in climate change is one of the most pressing issue of our time. We all agree that fossil fuels such as oil, natural gas, coals etc are the major sources of carbon dioxide emissions resulting in the global warming. In order to save the lonely planet, we must shift from current fossil-based energies to carbon-neutral renewable energy. To achieve net-zero carbon emissions by 2050 in the UK, a balanced energy portfolio should include wave and tidal energy. The extraction of clean and green energy from tidal waves is relative new area of research. In harvesting energy from tidal waves, among other techniques, tidal turbine blades are one of them. Tidal turbine blades are made of composite materials. Composites are natural choices over metals because they can be formed into complex shapes and have fatigue tolerance, corrosion resistance and damage tolerance, particularly in harsh operating environments such as subsea conditions. High reliability is of particular importance for subsea components due to the high cost of marine operations. Therefore, it is vitally important to fully understand the loads that tidal turbines will experience and to design against potential failure mechanisms. This allows appropriate safety factors to be applied without excessive over-conservative design, and can result in significant cost reduction.

Tidal turbines are prone to various failure mechanisms such as micro-cracks, delamination between fibres and matrix resins, chemical and physical aging from salinity, bio-fouling etc. Among these phenomena, water ingress due to diffusion under submerged conditions makes them seriously vulnerable to reduced service life.The aim of this research project is to predict the effects of aging by a de-coupled approach in order to understand the fatigue failure behaviour of tidal turbine blades made of fibre-reinforced composites. For this, essential experiments such as three-point, four-point flexural and biaxial fatigue tests will be conducted in submerged conditions under ambient and elevated temperatures. Furthermore, the same tests will be performed in air under ambient and elevated temperatures. Computational methods have already proved successful in simulating crack growths and various failure mechanisms. Based on experimental findings, continuum-based coupled models will be developed and validated to guide design techniques in the future to minimize the number of expensive structural tests that need to be performed.