Buckling of a sandwich composite cylindrical shell stiffened by rings under external pressure

A solution is presented for the problem of buckling of a sandwich composite cylindrical shell stiffened by rings and subjected to external pressure. The solution is obtained on the basis of the theory of stiffened composite shells taking into account the discrete position of the rings, the transverse shear deformation in the shell and rings, the laminated structure, and the orthotropy of the facing materials. The perturbed state of the stiffened shell is described by a semimembrane model, The prebuckling state of the structure is considered to be axisymmetric with allowance for prebuckling bending moments. It is assumed that the rings are deformed in their planes only and that the contact load between the rings and the shell is applied along Phe axis lying at the midsurface of the shell. The Dirac delta-function is used for the description of the distribution of contact forces acting between the shell and the rings. As an example, the critical external pressure has been obtained for a glass-epoxy structure of 5 m length, 1.25 m radius, and 0.12 m thickness stiffened by various numbers of rings.