Researchers incorporated adaptive wingtip devices in UAVs and full-scale aircraft to improve aerodynamic efficiency and to act as control effectors. However, these devices had been characterized statically, where their dynamic response was ignored. This paper characterizes the deployment dynamics of a novel adaptive multi-winglet (AMW) device. Each winglet in AMW is a feather-inspired composite exhibiting bending-torsion coupling. The gap spacing between each winglet is controlled by SMAs to vary the effective stiffness of AMW. Wind tunnel experiment’s results show the aerodynamic forces and moments produced by a wing with an AMW device with different gap spacing under different flight conditions.
Multifunctional lifting surfaces can expand the mission capabilities of aerial vehicles with a minimal number of components added to the vehicle. This paper presents a bio-inspired segmented wingtip concept for lift enhancement enabled by passive structural tailoring and active bistable truss mechanisms. The development of wingtips stems from studies of birds with desirable flight capabilities. The structural characteristics and maneuverable changes of a bird’s primary feathers during flight have identified three notable feather degrees of freedom: incidence angle, dihedral angle, and gap spacing. Wind tunnel experiments conducted on multi-wingtip systems have determined that different wingtip orientations and spacings are desired to enhance aerodynamic performance depending on the flight conditions. These results suggest that the wingtip degrees of freedom must be varied during flight to achieve optimal aerodynamic performance. This paper presents two structural concepts, one passive and one active, to achieve desired morphological wingtip parameters during flight. The passive structural concept exploits bend-twist coupling of additively manufactured composite laminate wingtips by using aerodynamic loads to induce passive shape adaptation of the composite wingtips to control the twist and dihedral angles. The active concept utilizes bistable truss mechanisms to vary the wingtip gap spacing. The force-displacement responses of bistable mechanisms and the bending and twist of bend-twist coupled composite wingtips are measured using a universal testing machine and Digital Image Correlation, respectively. Experimental results include the energy storage characterization of the bistable mechanisms as a function of material characteristics and the bend-twist coupling of the composite wingtips as a function of fabrication process and laminate properties.
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