Erosion issues in tidal turbine blades

The erosion of materials used in tidal turbine blades is a significant problem, as it can compromise the blade's structural integrity and efficiency over time. The present study aimed to investigate the erosion mechanism in composite and coating materials and the influence of seawater immersion on their mechanical properties. Scanning electron microscope and optical microscope were used to analyse the effect of various parameters such as impact velocity, impingement angle, erosion particle size, and fibre orientation on the character of erosion in the blade’s material. The investigation revealed that the erosion mechanism in GFRP was the result of the fibre matrix being eroded away, leading to a cracked surface composite, removal of the fibres, and exposure of the matrix. Moreover, seawater immersion significantly reduced the overall strength of the materials by de-bonding the glass fibres in the composite matrix. However, the GFRP material's tensile and flexural strengths could be regained by the desorption process. To address the problem of erosion in tidal turbine blades, a gradient-toughened composite with varying proportions of standard and toughened powders was developed using an inventive powder-epoxy fabrication method. The study showed that the gradient-toughened plates outperformed the standard plates in general, with a more ductile response to erosion and a more constant erosion performance across the range of impingement angles examined. The study also highlighted the importance of using erosion maps to visualise and analyse the level of material loss experienced by coatings under different impact conditions. The erosion map produced in the study provided valuable insights into the behaviour of the coating and can be used to optimise the design of the tidal turbine blades for increased durability and longevity. Overall, the study's results and conclusions provide valuable insights into the erosion mechanism in UD-GFRP and coating materials and the impact of seawater environment on their mechanical properties. The findings could be useful for the development of more durable and reliable blades that can withstand the harsh marine environment.The erosion of materials used in tidal turbine blades is a significant problem, as it can compromise the blade's structural integrity and efficiency over time. The present study aimed to investigate the erosion mechanism in composite and coating materials and the influence of seawater immersion on their mechanical properties. Scanning electron microscope and optical microscope were used to analyse the effect of various parameters such as impact velocity, impingement angle, erosion particle size, and fibre orientation on the character of erosion in the blade’s material. The investigation revealed that the erosion mechanism in GFRP was the result of the fibre matrix being eroded away, leading to a cracked surface composite, removal of the fibres, and exposure of the matrix. Moreover, seawater immersion significantly reduced the overall strength of the materials by de-bonding the glass fibres in the composite matrix. However, the GFRP material's tensile and flexural strengths could be regained by the desorption process. To address the problem of erosion in tidal turbine blades, a gradient-toughened composite with varying proportions of standard and toughened powders was developed using an inventive powder-epoxy fabrication method. The study showed that the gradient-toughened plates outperformed the standard plates in general, with a more ductile response to erosion and a more constant erosion performance across the range of impingement angles examined. The study also highlighted the importance of using erosion maps to visualise and analyse the level of material loss experienced by coatings under different impact conditions. The erosion map produced in the study provided valuable insights into the behaviour of the coating and can be used to optimise the design of the tidal turbine blades for increased durability and longevity. Overall, the study's results and conclusions provide valuable insights into the erosion mechanism in UD-GFRP and coating materials and the impact of seawater environment on their mechanical properties. The findings could be useful for the development of more durable and reliable blades that can withstand the harsh marine environment

Erosion Mapping of Through-Thickness Toughened Powder Epoxy Gradient Glass-Fiber-Reinforced Polymer (GFRP) Plates for Tidal Turbine Blades

Erosion of tidal turbine blades in the marine environment is a major material challenge due to the high thrust and torsional loading at the rotating surfaces, which limits the ability to harness energy from tidal sources. Polymer-matrix composites can exhibit leading-blade edge erosion due to marine flows containing salt and solid particles of sand. Anti-erosion coatings can be used for more ductility at the blade surface, but the discontinuity between the coating and the stiffer composite can be a site of failure. Therefore, it is desirable to have a polymer matrix with a gradient of toughness, with a tougher, more ductile polymer matrix at the blade surface, transitioning gradually to the high stiffness matrix needed to provide high composite mechanical properties. In this study, multiple powder epoxy systems were investigated, and two were selected to manufacture unidirectional glass-fiber-reinforced polymer (UD-GFRP) plates with different epoxy ratios at the surface and interior plies, leading to a toughening gradient within the plate. The gradient plates were then mechanically compared to their standard counterparts. Solid particle erosion testing was carried out at various test conditions and parameters on UD-GFRP specimens in a slurry environment. The experiments performed were based on a model of the UK marine environment for a typical tidal energy farm with respect to the concentration of saltwater and the size of solid particle erodent. The morphologies of the surfaces were examined by SEM. Erosion maps were generated based on the result showing significant differences for materials of different stiffness in such conditions