The development of an approximate method for the design of bead-stiffened composite panels

Abstract

Bead stiffened panels are extensively used in aircraft and other structural components to satisfy requirements of increased stiffness and weight reduction. Forming the vertical beads integrally in a composite panel as one piece makes it stiffer against compression buckling. Finite elements buckling analyses are performed for various panels with different beads spacing, beads depths, beads radiuses and panels lengths. The analysis of results has shown that the beads spacing is of chief significance as far as the panel buckling load is concerned. For a given panel, with a certain number of beads, there is an optimum value of beads spacing, which makes the panel stiffer than the other possible beads arrangement against buckling. A simple equation is proposed to estimate the optimum beads spacing for a given beaded panel. In order to, avoid several time consuming and costly finite elements buckling analyses, an approximate method is also proposed to obtain the upper and lower bound buckling load for the beaded panels. This fairly simple method benefits from the closed-form solution of a rectangular orthotropic plain plate. If the appropriate length and width are adopted for the orthotropic plain plate, the closed-form buckling solution of the same plate which is assumed to be either simply supported or clamped at the two sides can be used, respectively, to represent the lower or the upper limits to the critical buckling load of the corresponding composite beaded panel. This method can be used to estimate the buckling load of beaded panels in preliminary design stage of structures.