Local buckling modelling of isogrid and anisogrid lattice cylindrical shells with triangular cells

The paper deals with a refined analytical model for the local buckling failure modes of composite anisogrid lattice cylindrical shells made of a regular system of triangular cells. Such structures are preliminarily designed with the aid of closed-form solutions specifying the minimum mass and the corresponding optimal design variables under a set of formulated constraint equations. These equations address the main failure mechanisms that can be typically experienced by the structure due to axial compressive loads, namely, the global buckling of the shell, the local buckling of helical ribs, and the material failure of helical ribs. However, the local buckling of helical ribs is normally based on a simplified and qualitative approach. Thus, the scope of the present work is to improve the prediction of this failure mode by means of a rather accurate modelling which accounts for the interaction of intersecting hoop and helical ribs, the influence of the number of hoop sections of the shell, and the effect of the prebuckling tensile force in hoop ribs. The proposed model – that has been verified with the aid of finite-element analysis – lastly suggests the possibility to improve the preliminary design solution with respect to the fully analytical approach.

► Local buckling of ribs is one of the main failure mechanisms in lattice shells.
► Analytical modelling for the system of periodic triangular cells is addressed.
► The model accounts for the main design variables which characterize the shell.
► The good accuracy of the model has been verified via finite-element analysis.
► The proposed model enables to find more efficient preliminary design solutions.