**3. Quantitative Analysis of Relative Acoustic Impedance Characterization A**ff**ecting Rain Erosion Performance**

The wear erosion lifetime prediction model used in this research was computationally evaluated and implemented [15] to link material input data definition with its performance estimation. A complete map of the liquid droplet, coating LEP and substrate (primer or filler) material impedances as input parameters of the equations defined in the modelling is proposed in Figure 5.

**Figure 5.** Map of impedance values as input data for the wear erosion lifetime modelling, implemented equations in [15]. Diagram of liquid, coating and substrate material impedances and operational parameters affecting rain erosion performance.

In order to discuss assumptions and capabilities of the proposed modelling, different study cases are followed throughout this section of the document.
