Free vibration analysis of grid-stiffened composite truncated spherical shells

Abstract

In this paper, the vibrational behavior of grid-stiffened truncated composite spherical shells has been studied. Using a smeared stiffener technique, the stiffness contribution of the non-uniform grid structures are superimposed with those of the shell. The helical stiffeners have been considered as truss, which are able to bear the axial forces. The equations of motion have been derived within the framework of the classical Donnell’s thin shell theory and then solved by means of Galerkin method in order to extract the natural frequencies and vibration modes. The simply supported, clamped and combination of these two boundary conditions have been considered for the shell ends. In order to validate the semi-analytical results and also conduct an extensive parametric study, a 3-D finite element model has been built using ABAQUS CAE software. Comparing the results obtained via the two approaches, good agreement has been achieved. The effects of spherical shell’s geometrical parameters, lamination angle and different configurations of the stiffening structure have been examined as well. The results are new and can be considered as a benchmark for further studies.