Finite element analysis and experimental whiffletree testing of a small UAV composite wing

This study presents a comprehensive investigation of the structural performance of a small unmanned aerial vehicle (UAV) composite wing, integrating finite element analysis (FEA) and experimental whiffletree testing. The study focuses on a pusher-type UAV with a 2.9-m wingspan and 21 kg maximum takeoff weight. The distributed load from the Schrenk's method was converted into multiple point loads for whiffletree load by using the cantilever beam approach. When subjected to load within the limit load, the observed failure at the upper skin wing near the wing-body joint also complied with the failure results according to the finite element analysis with the Tsai-Wu failure index of 1. Conversely, the deflection comparison between the finite element analysis using whiffletree loads and the actual whiffletree testing showed good agreement, with maximum deflection values of 122 mm and 120 mm, respectively. With a difference of 1.67 in maximum deflection, the study validates the wing's structural integrity up to the design limit load and identifies failure modes within this limit. This aircraft structure can withstand load factor up to 2.8, making it safe for standard maneuvers during flight operations.