A Hybrid De-icing Strategy Utilizing Tailored Anti-Icing Coatings Paired with Electro-Thermal and Electro-Mechanical Ice Protection Systems for Use on Rotary-Wing Aircraft

Since the beginning of aviation, ice accumulation on aircraft surfaces has been a persistent problem. On rotorcraft, the consequences can be catastrophic as small changes to the blade aerodynamics can result in a loss of the vehicle. Most small and medium-sized civil helicopters do not have a means of de-icing while in flight as these systems are heavy and require a significant amount of power. This dissertation aims to investigate hybrid ice protection systems (IPS), in which an icephobic coating is paired with an electro-thermal or electro-mechanical IPS to reduce the weight and required power of the system. First, the surface properties required for an effective hybrid IPS pairing were identified. For an electro-thermal IPS, the coating should have a low ice adhesion strength and high thermal conductivity while electro-mechanical IPS require a coating with a low ice adhesion strength, high elastic modulus, and low critical energy release rate. In this study, polymer coatings were developed with enhanced mechanical properties. Although they had a high icephobicity, their mechanical properties were insufficient to facilitate an effective pairing. Metallic coatings had a very high wear resistance and moderate ice adhesion strength, which would still make for a good pairing. Then, a model was developed which evaluated the heating requirements for rotorcraft operating in icing conditions. The model found that, when a coating was added to the blade surface, the thermal power required for ice shedding could be reduced by up to 50 per cent. Finally, the critical energy release rate of coated samples was measured using a three-point bend test and a vibratory-based method. The latter method proposed in this dissertation is based on the measurement of the frequency shift during crack propagation, the displacement, and the crack length. The final results show the consistency of the two methods and the efficiency of the coatings: the critical energy release rate of coated titanium plates can be reduced from 0.35 J/m2 to 0.18 J/m2. From the findings of this research, de-icing strategies incorporating the ice protection method and desired coating properties were developed for electro-thermal and electro-mechanical IPS to be installed on rotor blades.