# Experimental Study of a Piezoelectric De-Icing System Implemented to Rotorcraft Blades
## 7 Conclusions  
This study discussed the design and preliminary testing of a piezoelectric de-icing system applied to a small rotating blade. The experimental tests conducted with the test setup were successful, and complete de-icing of the blade was achieved. Power consumption was calculated and showed a 25% reduction as compared to electrothermal systems. An FEA-based numerical model was also developed and used to investigate stresses. The numerical model allowed us to design the optimal positioning and excitation of the actuators to investigate shear stresses and conduct comparative studies. It was then estimated that the power reduction could be much more significant for a longer blade similar to a real tail rotor blade due to the size of the actuators, greater flexibility and higher centrifugal force. The numerical model was modified to the actual span of a real tail rotor, \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Mode**} & **Number of Actuators** & **Power without Rotation** & **Power in Rotation** & **Power Density in Rotation** & **Reduction from Thermal System** \\  & **Actuators** & **(W)** & **(W)** & **(W/in\({}^{2}\))** & **(\%)** \\ \hline
2 & 4 & 2250 & 1140 & 30 & \(-8\) \\
3 & 6 & 76 & 39 & 1.03 & 96 \\
4 & 8 & 53 & 27 & 0.72 & 97 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: De-icing power estimation based on numerical prediction for full-length tail rotor leading edge. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Mode**} & **Frequency (Hz)** & **Voltage for Shear Stress = 2.72 MPa (Vpp)** & **Voltage for Shear Stress = 2.72 MPa in Rotation (Vpp)** \\ \hline
2 & 1015 & 3510 & 2500 \\
3 & 1373 & 453 & 323 \\
4 & 1798 & 286 & 205 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Voltage prediction by the numerical model to obtain similar stress at de-icing for the small blade setup. and the first resonant modes were investigated. The numerical results have confirmed those assumptions, predicting a power reduction of up to 97%. Even if these results are preliminary and based on different assumptions and simplifications, they still show the great potential of the method. Following this comprehensive investigation on the use of piezoelectric actuators for ice protection systems, it is recommended to pursue the investigation with a full tail rotor prototype. In order to do so, the first step recommended is to use the FEA-based numerical model for the design of new optimal piezoelectric actuators. It is also recommended to design a measurement and operation system for the testing and validation of a full tail rotor prototype. The exact shedding mechanisms were not fully investigated, and the de-icing prediction was based only on the maximum shear stress prediction by the numerical model. While it was successful as a first step, with results for cracking and delamination within the literature values, a more complex approach should, however, be considered for full ice shedding. This kind of excitation could impact the fatigue life of the structure and its aeroelastic stability. This should be investigated in a future study, as well as the durability of the system itself. Finally, the centrifugal force, as defined in the numerical model should be investigated to ensure the validity of the results and could be verified experimentally on its own. This could be done using the Spinning Rotor Blade setup in the wind tunnel without any other systems involved. The stresses involved could then be compared and validated. Conceptualization, E.V. ; methodology, E.V. ; validation, E.V. and S.G.; formal analysis, E.V. ; investigation, E.V., S.G. and C.V.; data curation, E.V. and S.G.; writing--original draft preparation, E.V. ; writing--review and editing, S.G. and C.V.; supervision, E.V., S.G. and C.V.; project administration, E.V. and C.V.; funding acquisition, C.V. All authors have read and agreed to the published version of the manuscript. This research was funded jointly by the CRIAQ/CARIC (grant No. ENV-702), CRSNG (grant No.