# Experimental Study of a Piezoelectric De-Icing System Implemented to Rotorcraft Blades
## 2 Materials and Methods
### Static Small-Scale Blade  
The setup is based on a real helicopter tail rotor blade with a NACA 0012 airfoil shape and a 13.1 cm (5.25 inches) chord, as used by industrial partners. The span is limited to 22.9 cm (9 inches) to prevent excessive imbalances in rotation, as well as to fit in the wind tunnel test section used for testing. An aluminum foil 0.8 mm thick, the same thickness as the tail rotor blade's hollow leading edge [16], was given a curved shape to recreate the first 4.5 cm (1.8 in) of a NACA0012 airfoil profile (Figure 2). This section was selected since the leading edge of the blade is where most of the ice accumulation occurs. Aluminum was selected to fabricate a representative NACA0012 shape. It was observed that trying to bend a steel sheet with sufficient precision in order to fabricate the NACA0012 profile in the laboratory would have been very challenging or impossible with the tooling that was readily available. Six piezoelectric actuator patches PI876.A15 were installed on the curved aluminum foil. The patches were 61 mm long by 35 mm wide, with a total thickness of 0.8 mm. They were made of PIC255 piezoelectric materials, a flexible, modified PZT material. The patches were installed along the blade length due to size limitations within the profile (Figure 2). This configuration was selected to allow the installation of the patches within the very limited space in the hollow volume of the profile. For the real tail rotor, the hollow space behind the leading edge is approximately 1 cm [16], and the test setup's hollow dimension was kept as close to this value as possible while allowing the integration of the actuators. Three patches were installed on the upper and lower inner surfaces of the profile. The patches were installed as close as possible to the leading edge in the chord direction, limited by the curvature of the profile, which resulted in a distance of 1.3 cm (0.50 inch) from the leading edge. Spanwise, an actuator was installed centered with the profile on both the top and bottom surface to excite the resonant modes with an odd number of anti-nodes since they all contain an anti-node at the center of the structure. On each side of those actuators, the other actuators were centered in the remaining available space, at 1.14 cm (0.45 inch) from the edges of the profile. Epo-tek 353 ND glue, as recommended by the piezoelectric actuator manufacturer, was used to bond the actuators to the structure.  
Figure 1: AMIL icing wind tunnel [20].  
Two additional aluminum plates of the same thickness were used to build the back of the profile. They were shaped to replicate the back of the NACA0012 profile shape. The leading edge and back of the profile were assembled using an H spar (Figure 2). Rivets were used to assemble the parts on the H spar. The maximum number of possible rivets were used for the leading edge to recreate, as closely as possible, a fully clamped boundary condition. The blade structure was held in place in the wind tunnel using two fixation plates on each side of the profile. To operate the piezoelectric actuators, an Agilent 33500B waveform generator was used to provide the electrical driving signal to the actuators. The driving signal for the actuators was amplified using an Amp-line AL-1000-HF-A amplifier with a range of 50 to 1000 V to generate the required vibration level. Since the operational voltage of the actuators is \(-250\) to 1000 V, an Amp-line AL-100 DC power source was used to offset the voltage to allow testing at higher voltage swings (higher Vpp). However, when an actuator must be dephased from the other actuators, the positive wire was plugged into the negative output. This means that when an actuator is dephased, a maximum voltage of 500 Vpp can be applied to the actuators due to their voltage limit of \(-250\) V to 1000 V, and only the same offset can be applied to all actuators. The voltage applied to the actuators was measured using a Fluke 105B oscilloscope.