Conceptual Study on Large Scale Morphing in Helicopter Rotorblades

Abstract

Active rotor technologies have labeled the evolution of rotary-wing aircraft over the last years or even decades. The advent of new materials which have not only incorporated the traditional structural function but also an actuation function in response to a stimulus, enabled major ad-vances by being inserted directly on the actuation surface. The present master thesis introduces a feasibility study to investigate the potential of an anhedraltip on a rotor blade actuated by one of the actuators available on the market. The study is based on a numerical study conducted by ONERA where an optimization of the rotor aerodynamic performance was achieved in terms of the Figure of Merit for an anhedral tip of 30 deg. Pneumatic artificial muscles (PAM) are the selected actuators after a careful revision of the a vantages and disadvantages of each considered actuator. A detailed characterization of the PAM is per-formed through (1) a free displacement test, (2) a blocked force test and (3) spring contraction tests. A Working Diagram is proposed for the selected PAM from the results of these tests. A _nal test is conducted on the laboratory to measure the displacement of the PAM when different constant masses (to which correspond different loads) are suspended on the PAM. The whirl tests are conducted in the rotor tower of DLR (Deutsches Zentrum für Luft- und Raumfahrt) Braunschweig. A U-profile is used instead of a real blade allowing the permanent access to the arrangement. The hinge system is design in such way that the contraction of the PAM promotes the deection of the tip allocated in the last 20% of the blade. A maximum anhedral tip deection of 4:5 deg is achieved for 500 rpm.