Ice adhesion strength measurements for rotor blade leading edge materials

Icing environments have long been an issue for rotorcraft. Flight in icing conditions is fraught with operational hazards, including reduced vehicle performance and large torque rises. Shedding of ice from blades due to centrifugal forces poses a ballistics danger to the aircraft and creates large vibrations due to imbalanced rotors. For years, researchers have attempted to enhance this process by developing rotor coatings with low ice adhesion to continuously shed small pieces of accreted ice. These coatings would form the basis of a passive ice protection system, removing the need for a heavy and maintenance intensive active system to expand flight envelope in adverse weather conditions. A series of test fixtures has been developed to compare the performance of newly developed materials against the requirements for a passive ice protection system. The evaluations took a phased approach, as the test specimens and icing conditions becoming more complicated as more coatings were downselected. Ice adhesion testing was combined with erosion testing to determine the suitability of the coatings to survive the harsh environment in which rotor blades operate. Test results from the final test fixture compared favorably to published test results, but no material was able to meet the requirements for an icephobic material. The coatings intended to be icephobic had similar icing performance to materials designed to be erosion resistant, but were not able to survive the erosion testing.