Analytical formulation for local buckling and post-buckling analysis of stiffened laminated panels

This paper presents an analytical formulation for the study of linearized local skin buckling load and nonlinear post-buckling behaviour of isotropic and composite stiffened panels subjected to axial compression. The skin is modelled as a thin plate introducing Donnell-Von Karman and Kirchhoff hypothesis and applying classical lamination theory, while the stiffeners are considered as torsion bars. The first part of the work deals with the study of linearized buckling load, and two analytical solutions are presented: one is based on Kantorovich method and the other one on Ritz method. The second part of the work regards the development of a semi-analytical formulation for the study of the post-buckling field, using a variational approach and applying Ritz method. Results are compared with a serie of finite element analysis. It is shown that analytical buckling loads differ from numerical ones for less than 12%, and that force–displacement curves are well predicted. A computer program called stiffened panels analysis (StiPAn) is developed on the basis of the presented formulation. It allows quick analysis of stiffened laminated panels and is suited to be used in optimization routines for preliminary design.