Aeroelastic Analysis of Actuated Adaptive Wingtips Based on Pressure-Actuated Cellular Structures

Abstract

Folding wingtips are in the focus of research for their potential to counteract the challenges posed by high aspect ratio wings, such as airport conformity and increased wing root bending moment. Existing concepts for in-flight folding and morphing wingtips either enable passive load alleviation by adding free-flapping aeroelastic hinges to the wingtips or allow for advanced flight control and mission adaptability by actively deflecting the wingtips. In contrast, actuated adaptive wingtips combine the functionalities of passive and active in-flight folding wingtips by using a stiffness-adaptive aeroelastic hinge that is actively adjustable in flight. The objective of this paper is the aeroelastic analysis of a wing equipped with an adaptive-stiffness hinge. While the structural design of the wingtip actuator based on pressure-actuated cellular structures (PACS) was developed in a previous study, in this study the authors verify the concept of actuated adaptive wingtips through aeroelastic analysis. The aeroelastic model consists of a reduced beam structure coupled with the vortex lattice method. In the structural model, the PACS-based adaptive-stiffness hinge is implemented as an equivalent beam element and a pair of counteracting moments. This study shows that the investigated PACS actuator, which is structurally designed from glass-fiber reinforced plastic, is capable of bearing the loads acting on the wingtips of a Cessna Citation X. The adaptive-stiffness hinge, positioned between 86.7% and 91.2% of the semi-span, reduces the wing root bending moment by up to 7.8% in a 2.5 g maneuver load case, while keeping the wing straight in cruise. A further increase in load alleviation potential can be achieved in the future by extending the actuator's operating envelope and thus increasing its load-bearing capacity so that the actuator can be positioned more inboard. The functional verification of the actuated adaptive wingtip concept by means of aeroelastic analysis forms the basis for the manufacturing and testing of a functional prototype.