Trailing edge flap activated by a piezo-induced bending-torsion coupled beam

An active rotor blade trailing edge flap, driven via a piezo-induced bending-torsion composite beam was developed and hover tested. A novel spanwise variation in the beam ply-layup and piezoceramic element phasing was used to maximize the twist response, while minimizing the bending response. The induced tip twist of the actuator beam deflects the trailing edge flap. A proof-of-concept actuator beam was developed and tested, demonstrating pure tip twist actuation. Two small-scale model rotor blades were fabricated, each with a flap of 20% chord and 3% span, centered at 90% of the blade radius. The flaps were directly connected to the actuator beam and were not supported via bearings. Hover tests were conducted at rotor speeds from 300 to 900 rpm (corresponding to Mach 0.25) and collective settings from - 4 to 8 degrees to evaluate performance of the flap drive system. In open loop hover tests, 4/rev deflection amplitudes of 1.5 to 2 degrees (half peak-to-peak) were achieved at a rotor speed of 900 rpm.