Weight Comparisons of Optimized Stiffened, Unstiffened, and Sandwich Cylindrical Shells

Abstract

This work presents optimum designs for unstiffened, hat-stringer-stiffened, and honeycomb sandwich cylinders under axial compression. Optimization results for graphite-epoxy cylinders show approximately a 50% weight savings over corresponding optimized aluminum cylinders for a wide loading range. The inclusion of minimum gage considerations results in a significant weight penalty, especially for a lightly loaded cylinder. Effects of employing a smeared stiffener buckling theory in the optimization program are investigated through comparison of results obtained from a more accurate branched shell buckling computer code. It was found that the stiffener cross-sectional deformations, which are usually ignored in smeared stiffener theory, result in a reduction of buckling load by 30% for the graphite-epoxy hat stiffened cylinder.