**4. Conclusions**

In the current work, an investigation into various LEP configuration cases have been undertaken and related with the rain erosion durability factors, in an effort to assess the response of changing material and processing parameters involved on its blade application.

Diverse cases are developed throughout the research work, in order to ponder the key issues on appropriate LEP system definition for its mechanical characterization, to avoid a lack of accuracy on erosion performance analysis. Viscoelastic material models are originally considered within a coating layer impedance characterization methodology, based on ultrasound measurements for the modelling input data in rain erosion lifetime applications. The computational tool has been used to define erosion performance analysis, depending on the relative acoustic impedance of liquid, coating and substrate materials. The proposed numerical procedures to predict wear surface erosion have been used to identify suitable LEP coating and composite substrate combinations. Experimental campaigns of LEP erosion performance at rain erosion accelerated rain erosion testing (RET) technique have been used as the validation key metric to assess the response of each combined material configuration.

**Author Contributions:** Conceptualization, F.S.; investigation, L.D., V.G.-P., A.Š. and D.P.F.; methodology, F.S.; resources, A.Š., D.P.F., E.S. and F.S.; software, L.D. and V.G.-P; supervision, E.S. and F.S.; validation, F.S.; writing – original draft, F.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research has been partially funded by the DEMOWIND-2 Project Offshore Demonstration Blade (ODB) Funded by MINECO with reference PCIN-069-2017, by the ESI-Group Chair at CEU-UCH and from the European Union's Horizon 2020 research and innovation program under grant agreement No 811473. Project "LEP4BLADES".

**Conflicts of Interest:** The authors declare no conflict of interest.
