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Session: Wind tunnel testing 2
Session starts: Tuesday 18 June, 16:00
Presentation starts: 16:00
Room: Room 1.1

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Alexander Pankonien (Air Force Research Lab)
Nicholas Jones (PCKrause & Associates)
Asa Palmer (University of Dayton Research Institute)
Joshua Deslich (Air Force Research Lab)
Kevin McHugh (Air Force Research Lab)
Robert Taylor (University of Texas Arlington)

Abstract:
Additive manufacturing has lowered barriers associated with rapidly realizing complex shapes, such as the airfoils of wind tunnel models. To construct a flexible, aeroelastic wind tunnel model, these printed airfoils are typically affixed to an underlying structure, made with conventional fabrication techniques. However, the resultant design is not representative of the topologies typically found in aircraft, complicating actuation and sensing integration. This work details several years of exploring aeroelastic wind tunnels that leverage new, printed materials to build the underlying load bearing structure and skins. It is hoped that building all load bearing components simultaneously will reduce integration complexity, as well as lower overall fabrication cost and time, providing an opportunity for data assimilation into a conceptual vehicle design process. The method employed to design these models is a traditional conceptual aircraft sizing tool that allocates material thickness, and material stiffness when applicable to the printing process. This technique has been demonstrated for statically and dynamically scaled 20-inch semi-span models of a flying wing. Models in this work have been fabricated using one of two printing processes for comparison---polyjet or selective laser sintering. The models have been structurally tested experimentally, both quasi-statically and dynamically to validate their properties. The quasi-static deflection of the models under aerodynamic loading has been measured via digital image correlation measurement during wind tunnel testing, showing good agreement with expected stiffness, albeit with creep in the polyjet models. Initial efforts using the same experimental setup to characterize dynamic aeroelastic characteristics are also described, indicating the need for external excitation in these more highly-damped material systems. Finally, initial scanning of airfoil measurement for data assimilation is described, indicating good outer mold line agreement with the as-designed geometries in camber, but up to two degrees of erroneous twist. These results show promise for even larger models made with selective laser sintering of materials with higher glass transition temperatures.