Calculation of Natural Frequencies of Vibration of Thin Orthotropic Composite Shells by Energy Method

Abstract

The transverse shear effect should be included in calculating the natural frequencies of advanced composite material because of its high ratio of elastic modulus to shear modulus. The method which can include the transverse shear effect in calculating the natural fre quencies of thin orthotropic composite shells has been developed using the energy method (Rayleigh-Ritz method). In order to formulate the energy equations, the displacement equations which include the first order and sinusoidal terms w.r.t. the radial coordinate of the shell have been used rather than Kirchhoff-Love hypothesis. Also the Donnell's ap proximations were used in calculating the strains of the shell.