## 1 Introduction
Since ice is a very brittle material at high-strain rates, relatively little mechanical energy is required for breaking ice by using mechanical shocks as energy is not readily dissipated [7]. A main advantage of using a mechanical method instead of a thermal method is the relative ease of application. In fact, mechanical methods are the preferred choice for a timely and fast intervention to de-ice short critical sections [7]. [PERSON] et al. presented a novel pneumatic method to assist rotorcraft de-icing [10]. The pneumatic method consists of using a low-power, non-thermal, ultrasonic de-icing system as a potential replacement to current electro-thermal systems on helicopter rotor blades. [PERSON] et al. also proposed a low-energy de-icing system based on piezo-electric actuators [7]. The developed model allows for the design of a proper actuator to efficiently deice. Passive methods do not use conventional sources of energy as other methods do. Instead, they use natural forces such as wind, gravity, or solar radiation. Consequently,they can be applied on any structure, including rotorcraft. The main passive method consists of utilizing coatings that reduce the ice adhesion on structures of interest. These coatings are known as icephobic materials and have been used in several fields [14; 15; 16]. The benefit of using icephobic coatings is the decrease in ice adhesion to a structure and/or prevent supercooled water droplets from freezing. In order to achieve an icephobic surface, three different approaches have been introduced including fabricating a superhydrophobic surface [17], delaying ice nucleation [18], and designing a surface with low ice adhesion strength [19]. Superhydrophobic materials were introduced by [PERSON] [20] and claimed to exhibit promising anti-icing performance. However, [PERSON] showed in another study that by increasing the surface roughness of a superhydrophobic surface, ice adhesion increases [20]. In some cases, icephobic coatings have shown to exhibit good performance for rotor blades. Unfortunately, in most cases, these coatings lose their icephobic properties soon after application and exhibit poor durability [21; 22]. Hence, research in the field of icephobic coatings for rotorcraft applications is still ongoing. Many studies have been performed to both quantify and qualify the performance of coatings. For example, by assessing the icephobicity of superhydrophobic coatings of a helicopter blade in an icing chamber, [PERSON] [23] revealed that temperature and surface roughness have a strong impact on ice adhesion. The latter study showed that by decreasing the chamber temperature and increasing the coating roughness, ice adhesion strength increases. In another study, [PERSON] [24] developed an icephobic coating based on acrylic urethane resin and polytetrafluoroethylene (PTFE) particles for aircraft applications. The coating proved to be superhydrophobic and effective in anti-/de-icing aircrafts. [PERSON] [25], in 2009, impregnated a PTFE nanoparticle coating on a wind turbine blade surface. It was found that the very simple dipping provided a superhydrophobic surface and reduced ice adhesion. [PERSON] [26] investigated the effectiveness of superhydrophobic coatings on surfaces exposed to icing conditions equipped with an electrical heater. The results showed that superhydrophobic coatings could lead to a remarkable reduction of heating power on surfaces exposed to icing conditions. Recent advances in the development of icephobic coatings were also undertaken using superhydrophobic surfaces [27; 28; 29]. In order to evaluate the capability of a system subjected to icing conditions, ice adhesion is the main parameter used in industrial and academic investigations. As a complex physicochemical process, ice adhesion is not easy to quantify or compare since it depends on process parameters. Examples of these include ice density, ice formation conditions and substrate nature, and surface profile [30].