Investigation of the stress state and assessment of the stability of an anisogrid cylindrical shell when changing the parameters of the rib structure under static loading

The object of the study is a cylindrical mesh shell without a regular structure covering, made of carbon fiber composite material. A distinctive feature of this class of structures is the intersection of families of annular and spiral ribs. Mesh shells are used as power elements of spacecraft, therefore, when designing them, the main re-quirements are a reduction in the mass of the structure, high strength and stiffness characteristics. The re-duction of the shell mass is achieved by varying and selecting the structural and geometric parameters of the ribs. The article considers a set of mesh cylindrical structures of fixed mass. The authors have developed and presented an algorithm for calculating the number of elements of a regular rib structure and calculating the values of geometric parameters of elements of rib families. Two approaches to the formation of rib sys-tems are considered: by changing the heights or thicknesses of the rib structure. A macro has been developed for modeling parametric discrete models of such rib structures in the An-sys Mechanical APD software package. When constructing discrete grid models, a one-dimensional two-node finite element BEAM4 was used. The model was rigidly attached at the nodes along the lower edge, a load was applied to the nodes of the upper edge. Two types of loading were considered. The “non-flight” mode was determined by the axial loading of the shell evenly distributed along the upper edge. Flight mode – additionally took into account the applied moment. The displacement and deformation fields were calculated numerically in the ANSYS finite element package. The article presents the results of a study of the effect of the density of the rib structure on the stability of mesh shells under static axial loading, natural frequencies and waveforms. It is shown that with increasing density, the rib structure becomes thinner. At the same time, the critical load decreases, the values of the natural frequencies of the shells decrease, and the number of waves in the forms increases. The influence of approaches to the modeling of rib structures on the results of numerical calculations is noted.