Parametric Design Curves for Shear Buckling of Flat Orthotropic Stiffened Panels with Application to Glare Material

Abstract

The present paper investigates the shear buckling of flat, stiffened panels of specially orthotropic skin material, for which the stiffeners are assumed to possess both flexural and torsional rigidity. It is shown that the shear buckling behaviour can be captured by four generic, non-dimensional panel parameters, two of which relate to the skin orthotropy, the other ones representing the flexural and torsional stiffness of the stiffeners. Several design curves, showing the non-dimensional shear buckling load as a function of these four panel parameters, are generated using the STAGS FEM (Finite Element Method) code, where beam elements are employed to represent the stiffeners. The validity of the FEM method is demonstrated through comparison with an analytical procedure based on the Rayleigh-Ritz and Lagrangian multiplier methods. Furthermore, to assess the accuracy of the design curves a number of stiffened Glare panels are analysed with the STAGS FEM code. Combinations are investigated of riveted and bonded, open (Z-shaped) and closed stiffeners (rectangular section), which are commonly applied in aerospace structures. These particular FEM analyses are more realistic than the ones used to generate the design curves in the sense that the exact shape of the stiffeners is modelled with shell elements and the attachment method is explicitly accounted for. It is shown that the predictions from the design curves are in reasonable agreement with the detailed FEM results.