Design, Optimization, and Evaluation of Al–2139 Compression Panel with Integral T-Stiffeners

Abstract

A T-stiffened panel was designed and optimized for minimum mass subjected to constraints on buckling load, yielding, and crippling or local stiffener failure using a new analysis and design tool named EBF3PanelOpt. The panel was designed for a compression loading configuration, a realistic load case for a typical aircraft skin-stiffened panel. The panel was integrally machined from a 2139 aluminum alloy plate and was tested in compression. The panel was loaded beyond buckling and strains, and out-of-plane displacements were extracted from 36 strain gages and one linear variable displacement transducer. A digital photogrammetric system was used to obtain full-field displacements and strains on the smooth (unstiffened) side of the panel. The experimental data were compared with the strains and out-of-plane deflections from a high-fidelity nonlinear finite element analysis. The test data indicated that the panel buckled at the linear elastic buckling eigenvalue predicted for the panel. The out-of-plane displacement measured by the digital photogrammetric system compared well both qualitatively and quantitatively with the nonlinear finite element solution in the postbuckling regime. Furthermore, the experimental strains compared well with both the linear and nonlinear finite element models before buckling. The weight of the optimized panel was 20% less than that of a T-stiffened panel optimized using conventional design techniques.