Designing a High Speed Morphing Rotor Blade

Abstract

High speed rotorcraft experience regions of reverse flow over the inboard sections of blades. In these regions, because of the reverse flow, the rotor blade experiences high drag, large dynamic pitching moments, and the resulting significant vibrations. If the shape of the rotor can be changed “morphed” in the inboard section, a number of these adverse effects can be minimized. This paper outlines the approach to morphing the rotor blade to achieve two desired shapes suited for hover and forward flight. Different elements and associated risk reduction of the morphing system are discussed in details. A key element of a successful morphing structure is a flexible skin which can change shape and at the same time maintain rigidity and stiffness. The approach to achieving these conflicting goals through interleaved and off set layers of elastomers and composite sections, all co-cured in one step, is described. In addition an actuation approach and associated kinematics to achieve the shape change while minimizing actuation forces is also described. Assembly of the full-scale (in the chord-wise direction) prototype hardware of an 18% thick SC325218 airfoil is also included.