The effect of spanwise rib-boom stiffness on the stress distribution near a wing cut-out

Abstract

A theoretical investigation is made into the effect of spanwise rib-boom stiffness on the stress distribution at a cut-out in the inter-spar skin of a stressed skin wing in bending. Both shear and bending stiffness of the rib-boom are taken into account, and attention is concentrated on the case in which the rib-boom is built-in to the spar flanges. Curves are included which determine, for any particular case, the magnitude of the peak shear stress adjacent to the flange, the approximate spanwise variation of this shear stress, the proportion of load transferred by the rib-boom to the skin and stringers, and the bending moment in the rib-boom at its points of attachment to the spar flanges. By suitable design of the rib-boom it is possible to lower the shear stresses adjacent to the flange with little or no increase in structure weight. Available experimental results for the peak shear stresses are in good agreement with this theoretical work; previously developed methods a give over-estimates of the order of 100 per cent.