Understanding the fatigue behavior of tidal turbine blades

全球变暖及其对气候变化的影响是我们时代最紧迫的问题之一。我们都同意，化石燃料，如石油，天然气，煤炭等是导致全球变暖的二氧化碳排放的主要来源。为了拯救这个孤独的星球，我们必须从目前的化石能源转向碳中性的可再生能源。为了在2050年前实现净零碳排放，平衡的能源组合应该包括波浪能和潮汐能。从潮汐波中提取清洁的绿色能源是一个相对较新的研究领域。在从潮汐波收集能量的技术中，潮汐涡轮机叶片是其中之一。潮汐涡轮机叶片由复合材料制成。复合材料是金属的自然选择，因为它们可以形成复杂的形状，具有耐疲劳性，耐腐蚀性和耐损伤性，特别是在恶劣的操作环境中，如海底条件。由于海上作业的高成本，高可靠性对于水下部件特别重要。因此，充分了解潮汐涡轮机将经历的载荷并针对潜在的失效机制进行设计是至关重要的。这允许在没有过度保守设计的情况下应用适当的安全系数，并且可以显著降低成本。潮汐涡轮机容易出现各种故障机制，例如微裂纹、纤维和基体树脂之间的分层、由盐引起的化学和物理老化、生物污垢等。在这些现象中，在浸没条件下由于扩散而导致的水进入使它们严重容易受到使用寿命降低的影响。本研究项目的目的是通过一个耦合的方法，以了解由纤维增强复合材料制成的潮汐涡轮机叶片的疲劳失效行为。为此，将在环境温度和高温下的浸没条件下进行三点、四点弯曲和双轴疲劳试验等基本实验。此外，将在环境温度和高温下的空气中进行相同的试验。计算方法在模拟裂纹扩展和各种破坏机制方面已经证明是成功的。根据实验结果，将开发和验证基于连续体的耦合模型，以指导未来的设计技术，从而最大限度地减少需要进行的昂贵结构测试的数量。

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.