Buckling and Postbuckling Experiments of Integrally Stiffened Panel Under Compression-Shear Loads

Experiments have been conducted to investigate the buckling and postbuckling behavior of aluminum alloy 7050-T7651 integrally stiffened panel under a combined compression-shear load. A new combined-load test fixture was designed and used in these experiments. There were a total of six large rectangular stiffened panels in the size of 960 by 850 mm, which were classified in two groups according to the cross section and layout of their stiffeners. Three panels, named J panels, were designed in four parallel J-shaped stiffeners. Another three panels, named X panels, were designed in eight orthogonal blade-shaped stiffeners. Strain rosettes bonded back-to-back on the skin were used to measure the strains of skin at their locations in three directions (0, 45, and 90 deg), whereas the strain gauges installed on the stiffeners were used to measure the strains of stiffeners in a single direction. The integrally stiffened panels were loaded up to a sudden drop of the applied load and an accompanying harsh noise caused by the stringers splitting from skins. All the test panels failed in the same modes of global flexural buckling and the spitting of the stiffeners from skins. The mean value of the first buckling loads of Xpanels is 11.6% higher than that of the J panels. The mean value of the failure loads of X panels is 1.5% less than that of the J panels. All experimental results will be employed for the validation of finite element models and optimization method on the buckling and postbuckling analyses of integrally stiffened aluminum panel in further studies.