# Durability of Superamphiphobic Polyester Fabrics in Simulated Aerodynamic Icing Conditions
## 4 Summary and Conclusions  
The supermphiphobic fabrics maintained their favorable wetting properties after exposure to a range of aerodynamic multiphase flow conditions, including those conducive to atmospheric icing  
Figure 9: Sketch of two envisioned damage mechanisms of the flat plate configuration. (**a**) One being the tearing of an isolated feather ice grain from the fabric surface due to aerodynamic drag. (**b**) The second being after breakage of the feathery ice grain, it being carried, by a separated backflow of air, away from the surface and then back towards it, causing erosive or scratching damage to surface nanofilaments. The insets are SEM images of either pulling or erosive damage that was observed from experiments.  
of aircraft. When they were slightly damaged, they retained a high contact angle and much of the changed, but their chemistry and microstructure remained intact. Exposure to an airflow up to 115 m/s, to clouds of water droplets, and to icing conditions in a laboratory icing wind tunnel appeared to damage the fabrics similarly to an extended exposure on a car side-view mirror, but not significantly more [18]. When exposed to external environments like on a car, the conditions are much less controlled than in a laboratory test: mechanical degradation can occur from different types of impacting particles (rocks, sand, hail, and insects) and chemical degradation of of organic fluorine groups can occur after prolonged exposure to UV radiation. The results of this study show that exposure to small water droplets, even supercooled ones, at speeds up to 430 km/h, only slightly degraded the performance of a superamphiphobic fabric on a flat plate.  
Complete failure occurred at Reynolds numbers \(>\)1.4 \(\times\) 10\({}^{6}\) (speed of 120 m/s on a NACA 0012 airfoil) and mostly on the suction side of the airfoil. Thus, the fabrics may not be durable enough for forward facing surfaces of single-engine propeller aircraft that operate at that or at higher speeds. For low speed aircraft such as for urban air mobility, experimental aircraft, agricultural aircraft, drones, or gliders, aerodynamic shear on its own does not appear to be aggressive enough to remove the SNF coating. For cases where icing occurs over long periods of time and at relatively low speeds, such as for telecommunication antennae or oil rigs at sea, the first layer of ice build-up would protect the fabric from damage, meaning the icing conditions there would not cause significant damage to the superamphiphobic coating if the ice is not removed by hand, but allowed to detach when the ambient conditions become more favorable.  
Conceptualization, D.V. and E.B.; methodology, A.S.A., D.V., M.D., J.A.M.G., V.V., L.R., A.L., and E.B.; formal analysis, A.L., J.A.M.G., V.V., and L.R.; investigation, A.L.; resources, D.V. and E.B.; data curation, A.L.; writing--Original draft preparation, A.L.; writing--Review and editing, A.L. and E.B.; visualization, A.L., A.S.A., J.A.M.G., and V.V.; supervision, J.H. and E.B.; project administration, E.B.; funding acquisition, D.V. and E.B. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the European Union's Horizon 2020 research and innovation program under the [PERSON] grant agreement No. 722497--LubISS.  
The authors would like to express gratitude to [PERSON] for designing the manufacturing process for the NACA 0012 airfoil used in this study.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.