## 1 Introduction  
Rain erosion damage, resulting from repeated droplet impact on wind turbine blades, is a significant issue, particularly at offshore sites with larger blades and higher tip speeds. Erosion on wind turbine blade leading edge surfaces occurs throughout the entire lifespan of all blades under operational conditions. The repeated impact of liquid droplets and solid material particles creates a form of material wear. It may cause surface erosion or initially surface pits that progress to crack propagation in the leading edge protection (LEP) material or at critical composite interfaces [1], as shown in Figure 1. The damage can alter the surface of the blade, which modifies its aerodynamic profile and significantly reduces the annual energy production of the turbine. It creates an unbalanced behaviour increasing the drag and reducing the lift effect of the wind on the blade [2]. According to [PERSON] al. [3], erosion damage has been shown to represent the highest loss in aerodynamic performance, which reduces the economic attractiveness of the technology. Analysts from the U.S Department of Energy forecast a constant increase in the size and height of wind turbines [4]. Indeed, wind turbines use the kinetic energy from the wind to convert it into mechanical energy, producing consumable electricity. Since the wind tends to increase with altitude, the wind turbines are getting more-and-more enormous, especially in offshore farms [4; 5]. Increasing the size of each turbine also helps reduce the number of turbines per farm, mitigating significantly the frequency of the maintenance operations and therefore decreasing the levelized cost of wind energy (LCEO) [6]. [PERSON] et al. [7] estimate a reduction in annual energy production (AEP) ranging from 5% for low erosion to 25% for high erosion. This loss would represent a financial loss of 75 million euros across the European offshore wind energy sector, to which 56 million euros is added as the annual cost of repair and inspections [6]. Note that inspections and maintenance services have a significantly higher cost offshore compared to onshore locations, where the inland process is more simple and rapid to execute, according to the study of [PERSON] et al. [8], on wind turbines located in complex terrains. The study made by [PERSON] et al. [9] highlights the importance of overcoming the issues cited earlier. This remarkable growth is largely motivated by the finite nature of fossil fuels and the recent surge in the adoption of sustainable ideologies across society. Certain countries, such as Norway, are approaching nearly 100% electricity generation from renewable sources, according to [PERSON] et al. [10]. Additionally, the governments of many countries invest heavily in the area, underscoring the importance of involving researchers in this massive development. The aim is to find crucial solutions to all problems cited in the paper, making the technology as economically viable as possible. Since surface protection is an important factor in blade manufacturing and performance, it has been identified as an area where potential solutions can be explored. The wind turbine blade material and especially its leading-edge protection is one of the most researched topics in the wind industry. The more it resists erosion, the better the AEP. Nowadays, wind turbines are mainly manufactured using glass or carbon fibre composite layers with a polymer matrix. These composite materials offer good performance, optimising the weight and the structural integrity of the blade [11]. Composite materials are widely used in several industries, such as in aerospace, because of their high ratio between strength and stiffness to weight [12]. During the manufacturing process of a turbine blade, one or more layers of LEP are applied on the outer surface of the blade's leading edge. This  
Figure 1: Surface pits that may progress to crack propagation in the leading edge protection (LEP) material or through the composite substrate, affecting its integrity and aerodynamic performance.