Flutter analysis of inflatable wings

The stiffness of inflatable wing is determined by the internal pressure, so the static and dynamic coupling method should be established to solve the flutter problems of such wings. The structural stiffness and the normal modes should be calculated on the base of the static analysis. Then the unsteady aerodynamics can be calculated and the flutter characteristics of the wing can be analyzed using the traditional methods. For an inflated wing, the finite element model was created using membrane elements. The structure stiffness of the wing was derived by the static analysis and the normal modes were calculated. Then the flutter of the wing was analyzed. The results show that, as the internal pressure increases, each mode's natural frequencies increases. Except for the typical bending and torsion modes, the chord-wise bending modes have low frequencies. The chord-warping modes can induce flutter besides the conventional bending-torsion flutter type. The critical flutter speed of the inflatable wing presents nearly linearity with internal pressure increased in specific range and the corresponding flutter modes dose not change as well.