The objective of the first task was the specification by the industrial Partners of the list of elements to undergo coating or surface modification. The list drawn up initially consisted of 30+ proposed elements. Confronting these elements with the specific characteristics of the surface treatments and deposition techniques available within the consortium, as well as with the materials from which the components are made, the list was narrowed down to seven elements. In order to limit project costs, most work is conducted on small samples made of materials corresponding to those used in the full-scale elements. The work focuses on five materials, i.e. aviation aluminium and titanium alloys, stainless steel, carbon-epoxy composite and polyamide.
The overall research was divided into three categories, i.e. basic research which include common tests like surface topography, adhesion tests, wettability tests etc, more advanced tests including tests in icing conditions (mainly ice adhesion and accretion tests) and finally, coating durability tests e.g. corrosion resistance, degradation and UV resistance etc, performed only on those coatings that qualified in the previous two testing stages. This methodology is more efficient since it will not be necessary to test all the coatings but only those with the best performers. The most promising will be tested in two sessions by means of ice wind tunnel and during flight tests.
The research was focused on the work foreseen for the first stage, i.e. basic research. In parallel with the work within WP3 and WP4 tasks, computer simulations were conducted within the WP2 task. This work supported the practical tests aimed at developing appropriate surfaces. It also helped to better understand contact phenomena in micro and nano scale between droplet and surface.
The simulations were performed at three scales – nano, micro scale and macro. In order to confirm the hypotheses, the tests conducted in 2016 consisted of simulation of droplet behaviour on initial surfaces, i.e. on materials currently used to manufacture surfaces with particular risk of icing. The behaviour of droplets on aluminium oxide (Al2O3) and titanium oxide (TiO2) were modelled.
The partners performed sequence 1 tests (basic tests) to assess the fabricated coatings and/or surface modifications. More than 700 coatings/samples were prepared and reported to AGI in order to down-select the promising coatings for sequence 2 tests including ice accretion, ice adhesion, rain and sand erosions according the guidelines specified in testing matrix (D4.3). After performing sequence 2 assessment tests and the recommendation of the coating developers, a final selection of 14 coatings were tested in sequence 3 i.e. the large-scale icing wind tunnel at NRC (Ottawa) and the flight tests at INTA (Madrid).
