Flexural, torsional, and axial global stiffness properties of anisogrid lattice conical shells in composite material

Abstract

Flexural, torsional, and axial global stiffness properties of anisogrid lattice conical shells in composite material are analytically formulated in the paper. The conventional manufacturing process of this kind of structures is based on the continuous deposition of carbon fiber tows, by means of automated winding technology, which realizes regular systems of intersecting hoop and helical ribs. Winding trajectories of helical ribs are normally designed in order to be coincident with geodesics of the conical shell. As a consequence, given the geometry of the shell and the number of hoop and helical ribs, specific anisogrid configurations are determined that are feasible by winding. Various cross-sections of such ribs complete the specific solution. Each solution provides peculiar overall stiffness properties of the shell, which need to be predicted and optimized in order to fully meet the typical design requirements occurring in aerospace applications.In order to approach analytical global stiffness models, smeared elastic properties are introduced along with the classical membrane theory of conical shells. Developed models are verified by means of finite-element analysis showing a close correspondence with numerical results.