Rotor Design Using Smart Materials to Actively Twist Blades

A method utilizing so-called "smart materials" to achieve main spar twist is presented. This method is called Inter-Digitated Etectode Piezoelectric in Fiber Composite (IDEPFC), and is being applied jointly by MIT and Boeing to rotor blades. It uses active materials embedded in the composite plies of rotor blades actuated through applied electrical fields. Active twist for a 1/16 scale CH-47 rotor blade is demonstrated, and a preliminary design for a 1/6 scale blade is presented. The benefits of actively twisting the main rotor spar are quantified in terms of reductions in vibratory loads and hover power required. The influence that active twist may have on rotor design constraints and traditional ground rules is illustrated. Overall system performance, including economic merit, weight and power consumption for this method of actuation is evaluated, and the feasibility of applying this process to rotorcraft is discussed.