Modal density of honeycomb sandwich composite cylindrical shells considering transverse shear deformation

Abstract

Honeycomb sandwich shells with composite face sheets are of extensive use in the spacecraft industry. Information on the number of resonant modes present in a frequency band is required to study their response behaviour under acoustic excitation. Modal densities of thin composite cylindrical shells have been reported while transverse shear deformations have not been considered. But in honeycomb sandwich panels, transverse shear deformations are significant, especially at higher order modes of vibration. In this work expressions for natural frequency and modal density of composite cylinders incorporating transverse shear deformation are derived. The modal densities of a typical cylinder that are obtained using the derived expression are compared with the results obtained using the finite element method and they are similar. Effects of transverse shear and orthotropic nature of the face sheets on the modal densities are investigated. It is shown that computing the modal density of honeycomb sandwich cylinders without considering the transverse shear deformation can lead to significant errors at high frequencies. Expressions of modal densities for special cases are also derived from the general expression.