The Rain Erosion Effects On Polyurethane Coating For Wind Blade

Wind power is a new type of energy that is different from traditional energy sources.It is environmentally friendly,easy to clean,economical and efficient.As people's understanding of the drawbacks of traditional energy sources continues to deepen,more and more countries regard wind power as a focus of future development.In actual operation,the blade tip speed of the fan blade can reach more than 100 m/s.Blades without coating protection are exposed to the natural environment for a long time,which can quickly wear,age and even damage.It can be seen that the role of the coating in the working process of the blade is very important.In this paper,the mechanical response of wind turbine blade coating under rain erosion is theoretically analyzed,numerical simulation and experimental research are carried out to investigate the mechanism of coating failure under rain erosion.Based on this,the material selection of coating and parameter optimization is proposed.Firstly,this paper analyzes the raindrop collision of wind turbine blade coating,discusses the influence of various impact parameters on the stress and deformation of the coating,and further optimizes the parameters of the coating.It is found that the coating stress is linearly related to the impact angle of the raindrops,and the coating stress increases rapidly as the droplet size increases.The increase in coating thickness can cause the surface compressive stress of the coating to decrease rapidly and eventually stabilize.Reducing the coating modulus can significantly reduce the tensile stress in the coating during impact.When the high modulus and low modulus coatings are used together,the lower modulus coating can reduce the coating tensile stress on the surface and largely increase compressive stress.In addition,this paper also studies the case of raindrop coupling shock,and investigates the influence of raindrop spacing and height difference on the stress and strain of the coating.When double raindrops are coupled in the same plane,the tensile stress is affected by a larger range,and the compressive stress is affected by a smaller range.In the double raindrop coupling with different height differences,as the ?h increases,the tensile and compressive stresses of the material increase first and then decrease.When the four raindrops are coupled,as the distance between the raindrops and the plate center point increases,the tensile compressive stress decreases,and the compressive stress is more sensitive to the change of the pitch.The study also found that the water film on the surface of the coating has a buffering effect on the raindrop impact,which can greatly reduce the stress in the coating,and play a role in protecting the coating and extending the service life of the leading edge of the blade during the blade working process.Subsequently,this paper explores the failure mechanism of wind turbine blade coating.The destruction of the coating material is generally divided into two modes: cohesive failure of the coating itself and debonding of the coating from the substrate.The analysis results show that the failure of the coating is a gradual process,and the initial stage is the tensile stress fatigue caused by repeated impact of raindrops,resulting in microcracks.Hydraulic cracking is further induced after the occurrence of cracks,and high-speed liquid can penetrate into these cracks and generate high pressure at the crack tip,thereby promoting its growth and causing further destruction of the material.The concave structure formed after a small surface damage will increase the stress on the coating and accelerate the failure process of the coating.The polyurethane coating cure reaction will leave traces of carbon dioxide inside the coating forming a cavity.When the raindrops hit,the cavity is prone to stress concentration,causing the coating to break from the inside.In this paper,the interfacial properties of polyurethane coatings were studied in succession.The adhesion test of polyurethane coatings was carried out.The results showed that the adhesion of polyurethane coatings was good and met the requirements of the industry.The results of rain erosion test show that the crack of the sample tends to develop from the top of the curved resin block to the upper and lower ends during the development process,showing tensile damage,indicating that the tensile stress on the surface of the coating is the coating.The main factors in the destruction process are consistent with the results obtained by numerical simulation.