HALE UAV Composite Wing Structure Design

HALE (High Altitude Long Endurance) UAVs are aircraft systems for surveillance and reconnaissance for over 25 hours. Most of UAVs consist of fuselage and high aspect ratio wing because of long-endurance flight mission. The structural weight of HALE UAV is one of the most critical design requirements. In addition, the structural stiffness for the high aspect ratio wing is another critical design requirement because the UAV has to keep the minimum clearance between wing tip and ground when the UAV is being towed. For above design requirements, the wing structure of the UAV has been designed by intermediate modulus Gr/Ep composite materials. The goal of this research is to present the optimized design concepts for the composite wing structure of the UAV. Although there are many design parameters for the composite structure of the aircraft, this research is focused on composite structure strength and buckling analysis for the plate type structures, such as cover panel skins and spar webs, which are loaded in in-plane shear and/or compression. This research presents that the wing structural weight can be reduced when the material allowables based on tape laminate are applied instead of unidirectional lamina allowables. For the buckling analysis, this report has a trade off study to find an optimized lay-up design and stacking sequence with 0°, ±45° and 90° plies. This research shows that the critical buckling load is a function of the number of ±45° plies and the position of the ±45° plies through the laminate thickness using a typical Gr/Ep composite tape material. The structural design of the UAV composite wing regarding buckling analysis is more effective when the laminates are stacked up with high percent of ±45° plies and the ±45° plies are located toward outside through the laminate.