Buckling and postbuckling of advanced grid stiffened truncated conical shells with laminated composite skins

A theoretical approach is presented to derive an explicit formula for buckling load and postbuckling path of advanced grid stiffened conical shells (stiffeners with laminated composite skins). Different types of fiber paths of grids including stringer, ring, and helical are considered. The simply supported truncated conical shell with imperfection is subjected to axial compression. Basic formulations are constructed using the classical theory of shells and von Karman type of nonlinear strain-displacement relationships. The equilibrium and compatibility equations are solved by Galerkin procedure, and an explicit relation is obtained to predict the equilibrium paths. Results for different conditions are verified by comparison to existing data in the literature. Novel results are revealed in the parametric study to show the effects of different fiber paths, geometrical conditions, and lay-up configurations on the buckling and postbuckling of the advanced grid stiffened structures. As a key finding, the helical and ring fibers of grids are more effective than stringer on the buckling load and postbuckling path. Especially when high number of ribs are considered.