Development and Testing of a Span-Extending Morphing Wing

Abstract

Recent developments in morphing aircraft research have motivated investigation into conformal morphing systems, that is, shape change without discrete moving parts or abrupt changes in the airfoil profile. In this study, implementation of a continuous span morphing wing is described. The system consists of two primary components: (1) zero-Poisson ratio morphing core and (2) fiber-reinforced elastomeric matrix composite skin with a nearly zero-Poisson ratio in-plane. The main goal for improved air vehicle efficiency was a nominal 100% change in area of the active wing section with less than 2.54 mm out-of-plane deflection under representative aerodynamic loading. Objectives of this study included exploring fabrication techniques for advanced morphing core shapes (i.e., having airfoil-shaped cross-section), exploiting customizable design parameters of in-house fabricated skin and core material, designing a prototype wing structure such that integration with a candidate UAV was feasible, and experimentally evaluating a laboratory prototype. As a result of this study, the ability to physically build and test a viable airfoil structure capable of increasing its planform area by 100% (doubling span with constant chord) was demonstrated on a prototype hardware demonstration article. Satisfying objectives of designing, fabricating, and testing a prototype morphing wing section capable of 100% span extension, while maintaining constant chord, a wind tunnel test highlighted the resulting viable aerodynamic surface in a wind tunnel test up to 130 km/h wind speeds. The prototype wing in its resting condition had a span of 61.0 cm, which could be extended to 122.0 cm, with less than 2.54 mm out-of-plane deflection in dynamic pressures consistent with the maximum speed, 130 km/h, of a candidate unmanned aerial vehicle platform. In meeting these goals, the morphing core was successfully transitioned from a simple 1D concept into a complex, cambered airfoil with sufficient free volume to house an actuation system. A refined elastomer matrix composite skin fabrication technique was also devised and experimentally validated on skins of various thicknesses and overall dimensions.

Development of a Span-Extending Blade Tip System for a Reconfigurable Helicopter Rotor

“…22 Though these advanced blade shapes are static, feasibility of dynamic shape changing skin technologies has been proven for one-dimensional structures 23,24,25 and airfoil structures. 26,27 Hence, it appears that the maturity of these types of components has progressed to a level where design for fabrication and testing on a rotorcraft system is possible. Herein, shape-changing rotor blades could be designed to account for the conflicting requirements of advancing and retreating blades, approaching an aerodynamic optimum, or to change configuration for optimal hover or forward flight performance.…”

Morphing Trailing Edge Control Using Flexible Matrix Composite Actuators

“…In general, morphing aircraft is developed to increase vehicle performance by changing their external shapes during flight. 1 Morphing on a larger scale that involves significant changes in the camber, 2-4 wing span, [5][6][7] twist, 8,9 or sweep 10,11 has been profoundly investigated since the early 90's with NASA's Morphing Project. 12 A recent review on morphing aircraft, focusing on structural active morphing concepts, can be found in Barbarino.…”

A review on shape memory alloys with applications to morphing aircraft

“…Applications for morphing aircraft (Vocke III et al 2011) based on SMAs are of great scientific interest. The lifting surfaces of current aircraft are designed as a 'compromise' geometry that allows the aircraft to fly in a range of flight conditions, but the performance in each condition is likely to be sub-optimal.…”