Autonomous Camber Morphing of a Helicopter Rotor Blade with Temperature Change using Integrated Shape Memory Alloys

Abstract

The present study proposes and explores a new autonomous morphing concept, whereby an increase in helicopter rotor blade camber of the order of 12-13° is realized over the inboard section of the blade with increase in ambient temperature. The camber change is achieved through a proper integration of Shape Memory Alloys (SMAs) on the lower surface of the blade aft of the leading-edge spar. For a reference rotor (no-SMA) generating 21,000 lbs thrust, operation in hot conditions resulted in a 2,590lb loss in lift. When the SMA camber morphing section extends from the blade root to 50% span, the rotor recovered up to 43% of the lift loss at high temperature. If the camber-morphing section is further extended to 75% span, up to 82% of the lost lift can be recovered.

Shape Memory Alloys Applied to Automotive Adaptive Aerodynamics

“…SMA wires have been used as actuators [ 34 , 35 , 36 ] or embedded in laminated composites to drive surface morphing [ 37 , 38 , 39 ]. However, the literature suggests that several difficulties have been encountered in these applications, mainly related to the fracture mechanisms at the interface between SMAs and composites, as well as the need to maintain SMA temperatures within specific ranges for the stable activation of both the actuators and the morphing surfaces [ 40 , 41 , 42 ]. Furthermore, to overcome the limitations of constant force and cooling processes associated with shape memory alloys, some studies have explored different approaches to utilize the benefits of the austenite and martensite phase transformation [ 43 ].…”