Flutter analysis of sandwich panel with the constrained viscoelastic layer considering the effects of the imperfection and the core thickness deformation

Abstract

The supersonic flutter analysis of panels treated with the viscoelastic constrained layer damping (CLD) is performed with a special focus on the effects of the initial geometric imperfection and the core through-the-thickness deformation on the flutter boundaries. For kinematic modeling of the CLD core, a higher-order shear deformation theory is used where the through-the-thickness deformation is also taken into account. The core viscoelastic property is also described using the frequency-dependent complex-modulus approach and the first-order Piston theory is employed to determine the aerodynamic pressure. The discretized equations of motion are then derived using the finite element method (FEM). The integrations required in the FEM for obtaining each element stiffness matrix are also facilitated by approximating the imperfection function using the quintic Hermite interpolation function. Moreover, due to the large dimension of the final global matrices, the model is reduced using the oscillatory damped modes of the panel, which greatly reduces the computation time needed for flutter analysis. Numerical studies are performed for two different viscoelastic materials (VEMs), which shows that an efficient flutter suppression could not always be achieved with any type of VEMs. The thickness deformation effect is also found to be most prominent when the CLD length is about 80% of the panel length. Moreover, the mode crossing phenomenon that occurs by increasing the imperfection amplitude is found to significantly reduce the flutter boundaries.