Structural efficiency study of graphite-epoxy aircraft rib structures

Abstract

The present study focuses on the structural efficiencies of optimally designed composite wing rib panel configurations. The configurations studied include a tailored corrugated panel, a corrugated panel with a constant-thickness continuous laminate, and a hat-stiffened panel. Also included in the study are a blade-stiffened panel and a flat unstiffened plate which are used as baseline configurations for comparison. Thicknesses of different plies with preselected ply orientations in the different sections of the panels and detailed cross-sectional dimensions are used as sizing variables. The constraints considered include those associated with material strength, buckling, and geometric limits. The loads considered for this study are based on a typical loading of an inboard wing rib fuel cell closeout panel for a large transport aircraft and include in-plane axial compression Nx, shear Nxy, and out-of-plane pressure P. Structural efficiencies and cross-sectional geometries of different configurations are compared for a wide range of combined loads. Transition of the optimal cross-sectional geometry from one panel configuration to another is demonstrated as the loading is varied. The sensitivities of optimized designs to large changes in some of the geometric parameters are also studied.