Durable Anti-Icing Coatings
Materials and Coatings
Durable Anti-Icing Coatings (LAR-TOPS-381)
Passive Prevention of Ice Accretion for Aircraft Surfaces and Beyond
Overview
Prevention of ice accretion on aircraft surfaces while in flight is critical. Ice accumulation on aircraft wings can effectively change the shape of the wing, resulting in degraded aerodynamic performance, fuel efficiency, and most importantly, flight safety. Commercial aircraft use active (i.e., energy-consuming) strategies, such as heated surfaces, to mitigate ice buildup. Recognizing the drawbacks of such active strategies, including increased fuel burn, manufacturing / maintenance complexity, and increased aircraft mass, innovators at NASA's Langley Research Center set out to formulate low ice adhesion strength coatings for aircraft and other surfaces. NASA developed coatings that reduced impact ice adhesion strength on surfaces, resulting in four issued patents.
However, one challenge remains - ensuring the low ice adhesion strength coatings are robust enough to withstand the harsh environments experienced by aircraft leading edges.
The Technology
Low ice adhesion strength coatings are only useful insofar as they remain on the surface of interest, and aircraft leading edges experience extreme environmental conditions during flight. Ensuring durability while maintaining performance – in this case, reduction of impact (i.e., accreted in-flight) ice adhesion strength – is critical to meeting the needs of the aviation industry and other commercial applications.
To that end, NASA engineers investigated coating compositions comprised of epoxy resins, including aromatic and aliphatic resins, and aromatic diamine hardeners. Several nonreactive additives were incorporated and tested. The first was holey graphene, a unique nanomaterial made by partly oxidizing areas of graphene that already have defects. This creates high energy functionalities that result in good dispersion throughout the matrix, enabling the mechanical properties of graphene to be imparted throughout the coating. Secondly, micrometer-sized core-shell rubber particles were dispersed throughout the epoxy resin to increase toughness. Finally, a series of polyhedral oligomeric silsequixones (POSS) were used for mechanical reinforcement.
Several different coating formulations were development and tested, each incorporating different relative amounts of additives, with good results. Thus, the coatings can be tailored to meet different application-specific requirements.
NASA's coating formulations, with further development, may be suitable for in-flight (i.e., impact) ice adhesion reduction on aircraft leading edges and other platforms exposed to harsh environments.
Benefits
- Durability: Improved durability has been demonstrated in a series of controlled laboratory experiments. Further coating development work could allow these coatings to persist in harsh environments, such as those experienced by aircraft wing leading edges.
- Passive: Active anti-icing methods consume energy, add mass, and entail mechanical complexity, leading to increased fuel burn and degraded aircraft performance. NASA's coatings represent a completely passive method for mitigating impact ice adhesion, potentially reducing reliance on active systems.
- Expands aircraft operating conditions: Small aircraft that cannot support the mass or complexity of active anti-icing systems are forced to rely on passive strategies, reducing the range of weather conditions at which flight is safe. An effective, durable low ice adhesion coating may help expand the range of safe operating conditions for such aircraft.
Applications
- Passive anti-icing in harsh environments: NASA's coatings can be used to reduce ice adhesion on aeronautic exterior surfaces (e.g., aircraft wings, propeller blades, UAVs), wind turbine blades, ship surfaces, and other leading-edge surfaces.
- Mitigating adhesion of other contaminants on surfaces: In addition to ice, these coatings may also find applications for preventing the accumulation of other surface contaminants (e.g., insects) for aircraft, wind turbines, etc.
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