A semi-analytical approach on the effect of external lateral pressure on free vibration of joined sandwich aerospace composite conical-conical shells

Abstract

This paper investigates the free vibrational behaviors of joined composite sandwich conical-conical shells under external lateral pressure. The corresponding equations are derived based on the first order shear deformation theory (FSDT). Herewith, free vibration equations are extracted via applying Hamilton's principle and considering initial mechanical stresses solved by static equilibrium equations. To establish the continuity of two conical shells, compatibility of displacements and stress resultants are satisfied at the junctions. The generalized differential quadrature (GDQ) method is adopted to discretize the governing equations for each conical segment, together with related boundary and continuity conditions in a meridian direction. In order to verify the results as well as representing the convergence of the presented approach, some pieces of case studies are accomplished. These studies provide a better exhibition of lateral pressure, cone angles and shell thickness influences on the free vibration of joined composite sandwich conical shells with various boundary conditions. Then, the effect of four different types of materials which are more applicable in pressurized environments such as underwater and submarine structures, i.e. polyetheretherketon (PEEK), polycarbonate (PC), solid propylene (SPP), and high density polyimide foam (HDPF) are investigated for the core layer. Critical buckling pressure in the present approach is obtained when the natural frequency takes the value of zero for the lowest pressure. Finally, the values of lateral pressure are selected considering the critical buckling pressure to avoid buckling occurrence.