Design and Analysis of a Novel Reversible Airfoil Mechanism

Stop-rotor aircraft, which utilize a central lifting surface capable of transitioning between rotation and fixed configurations, offer a promising option for improving the efficiency of vertical take-off and landing aircraft. However, across the transition between rotation and fixed configurations, the necessary airfoil directionality for efficient aerodynamic performance changes. This work presents the design and experimental analysis of a novel reversible morphing airfoil capable of altering the airfoil directionality necessitated for stop-rotor aircraft. Inspired by roll-up chair design by Uros Vitas, the proposed morphing reversible airfoil, henceforth referred to as the folding slat method, takes shape primarily through a flexible strip that is symmetric about the center and consists of a series of rigid trapezoidal extrusions, forming slats, that are mounted on a flexible substrate. The directionality of the airfoil is switched by altering the compression and tension of each side of the strip, thereby pressing and releasing the contact points between the trapezoidal sections. While the proposed folding slat successfully morphed the leading and trailing edge, the experimental evaluation of the morphing airfoil was critical to justify its usage in a real system. As such, a suite of tests evaluating the compression, bending, and fatigue behaviors were performed. From this testing, it was shown that the folding slat could transfer up to a 150 N load without any added electrical energy usage and was able to switch the orientation of the leading and trailing edge at least 1,000 times, while still maintaining adequate stiffness.