Influence mechanism of void content on flutter characteristics of composite wings for low-altitude aircraft

To balance the dual demands of economy and low emissions, electric aircraft increasingly employ high-aspect-ratio, low-cost composite wing structures. However, such structures face two critical challenges: first, voids within the composite material reduce structural stiffness; second, high-aspect-ratio wings are susceptible to flutter instability. This study investigates how void-induced performance degradation affects wing flutter characteristics. An integrated framework is established by extending multiscale composite analysis method and coupling it with structural dynamic finite element model. A combination of experimental and numerical analyses was employed to systematically investigate the influence of void content. Experimentally validated multiscale analysis quantified the effect of void content (1–10%) on constitutive properties, revealing a limited reduction in fiber-dominated in-plane modulus (<6.43%) but a significant decline in matrix-dominated out-of-plane modulus (17.33%) and in-plane shear modulus (14.55%). These property degradations were propagated to a wing dynamics model, and flutter analysis via the P-K method in conjunction with nonlinear aeroelastic responses showed that a 10% void content reduces the critical flutter speed by over 11%. Mechanism analysis indicates that the reduction primarily stems from decreased bending stiffness due to lower in-plane moduli and, more critically, from weakened torsional stiffness resulting from shear modulus loss, which intensifies bending-torsion coupling.