Ice accretion on aircraft has a negative impact on both safety and performance, as it affects lift, drag, and thrust. As such, there have been great efforts devoted to the development of coatings that reduce ice adhesion, delay ice formation, or shed water droplets before it freezes. Such coatings are referred to as “icephobic coatings”. Among the different surface design strategies to enable icephobicity, one has attracted considerable interest due to its efficiency and manufacturing flexibility: superhydrophobic surfaces. Superhydrophobicity means extreme water repellency; it is obtained by combining a low surface energy material to an appropriate surface micro/nano structure (e.i, micro-pillars, grooves, bumps, etc). Water on superhydrophobic rests in the so-called “Fakir” state, e.g., at the top of the micro/nano structure features.

Ice-build up on aircraft occurs under specific conditions that can be reproduced in laboratory solely by means of costly installation (icing wind tunnel). Therefore, research groups have been studying the link between surface wettability and ice adhesion strength so as to find simpler way of assessing icephobicity. This was based on the reasoning that water and ice have a similar surface energy and that a surface that repels water should have the ability to lower ice adhesion. However, to date, no clear correlation was established between water wettability and ice adhesion strength. On the other hand, surface micro/nano structure has been experimentally proven to drastically affect ice adhesion, whether it is in a positive or negative way. Nevertheless, to our knowledge, no mechanical analysis of ice adhesion to non-planar substrate is provided in the literature. This lack of understanding restricts the development of icephobic coating to less efficient empirical approaches.

This study aims to clarify the role of the surface micro/nano structure on ice adhesion in order to derive design rules. To this end, experimental data were gathered by measuring ice adhesion shear strength on substrates that were regularly patterned using a nano-second laser. The test was performed using a custom-made apparatus, in a cold room. Failure analysis were done using a replica resin at cold temperature. A thermodynamic model, based on the Gibbs free energy of the wetted surface, was used to determine the ratio of wetted area to non-wetted area. Finally, a numerical model of the bi-material ice/substrate interface was developed at a mesoscopic scale, using the extended finite element method coupled with a cohesive traction–separation laws.

First experimental results show a good correlation between ice adhesion strength and the ratio of wetted area to non-wetted area. The morphology of the ice/structure interface (e.g., whether the water filled the grooves or not prior to freezing) has a great influence on the ice adhesion, as replica resin revealed that ice trapped within the micro structure leads to a mixed cohesive/adhesive failure. Future works will focus on corroborating those results to the numerical model.


Effect of Microstructure Design on Ice Adhesion for Icephobic Application \u2013 an Experimental and Numerical Approach

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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