Nonlinear high-dimensional flutter analyses of variable stiffness porous sandwich conical shells

Abstract

In this work, the nonlinear flutter characteristics of the truncated porous sandwich conical shell with variable stiffness under simply supported boundary, which is placed in the thermal environment and supersonic flow, are explored. The sandwich variable stiffness conical shell is constructed of two carbon fiber surface sheets and a porous core with aluminum foam, which has the exponential variable thickness along the longitudinal direction and five various styles of porosity distribution schemes along the thickness direction. The supersonic aerodynamic pressure is presented by utilizing the first-order piston theory considering the curvature effect. By means of the first-order shear deformation theory (FSDT), Hamilton's principle and Galerkin technique, the high-dimensional nonlinear variable stiffness second-order ordinary differential equations of motion are derived. The critical flutter points can be determined and flutter boundaries can be examined by addressing the linear eigenvalue problem. By applying the fourth-order Runge-Kutta approach, the influences of the exponent of thickness function, porosity distribution pattern, porosity coefficient, semi-vertex angle, temperature increment, total number of layers, fiber orientation angle, the core layer's minimum radius-thickness ratio and length-thickness ratio, on nonlinear flutter behaviors are analyzed in depth. The results reveal that the porous varying thickness sandwich conical shell with Style-O distribution and 0° fiber orientation angle is a better choice for high stability against flutter, and linear flutter analysis can be chosen to explore the flutter boundary by further comparison.