Aeroelastic Coupled Mode Behavior of Swept Composite Wing

Abstract The aeroelastic behavior of swept composite wings is predominantly governed by the coupling between bending and torsion modes due to the anisotropic characteristics of composite materials. This study analytically investigates the aeroelastic response of swept rectangular wings, modeled as carbon fiber/epoxy plates, to determine flutter and divergence speeds. The analytical approach integrates classical plate theory, Rayleigh-Ritz energy formulation, potential and kinetic energy equations, and unsteady incompressible two-dimensional aerodynamic theory within the Lagrange framework for free vibration and aeroelastic analyses. Numerical free vibration analysis is conducted using NASTRAN to validate the proposed analytical model. V-g curves are employed to extract flutter and divergence speeds, and the results exhibit excellent agreement with published findings. The study reveals that negative bending-torsion coupling stiffness significantly increases the likelihood of divergence occurring before flutter. Positive bending-torsion coupling significantly increases the divergence speed, effectively shifting the critical divergence speed beyond the typical flight envelope. Moreover, increasing the sweepback angle generally increases divergence speed. The effect on flutter speed is complex and depends on various factors, such as fiber orientation, stacking sequence, and bending-torsion coupling. These findings provide critical insights into aeroelastic behavior and offer a foundation for optimizing the performance and structural design of swept composite wings.