Aeroelastic deformation and buckling of inflatable wings under dynamic loads

Wind tunnel investigations have been conducted in order to determine the aerodynamic and structural deflection characteristics of a new inflatable wing design for unmanned aerial vehicles (UAVs). The wings were tested over a range of dynamic pressures from 0 to 400 N/m² and angles of attack from 0° to 16° corresponding to below the minimum stall speed up to speeds resulting in wing buckling. Since the inflatable wing stiffness varies as a function of the internal inflation pressure, the inflation pressure was varied below the design pressure in order to examine the effect of reduced stiffness on wingtip twist and bending. In order to accurately record deflections across the entire wing, photogrammetry was used as the measurement technique. The inflatable wings display a wash-in deformation behavior, increasing the span-wise angle of attack as the wing bends. Vibrational analysis was conducted using XModal for modal parameter estimation and measured in the wind tunnel using a laser displacement sensor. At an inflation pressure of 41.4 kPa (6 psi) the measured broadband frequency response due to dynamic loading is ±10 Hz.