An experimental investigation of the general instability of ring-stiffened, unpressurized, thin-walled cylinders under axial compression

Abstract

Eight different series of thin-walled Mylar cylinders were tested experimentally to investigate the general instability of ring-stiffened, unpressurized, thin-walled cylinders under axial compressive loading. The primary objectives for these tests were: to determine whether the bending or the torsional stiffness of the rings was the most effective stiffening parameter; to determine the relative effectiveness of ring-stiffeners around the inside and the outside of the cylinders; and to investigate the mechanism of buckling of unpressurized cylinders under axial compression. It was found that the torsional stiffness of the ring-stiffeners was the most important parameter for stiffening the thin-walled Mylar cylinders under axial loading. Ring-stiffeners with a low torsional stiffness did not stiffen the cylinder effectively until the rings were closely spaced. Ring-stiffeners on the inside of the cylinders did not affect the maximum buckling load when they were not bonded to the cylinder walls. Ring-stiffeners on the outside of the cylinders provided effective stiffening whether they were bonded to the cylinder walls or not. The experimental results of thin-walled cylinders under axial compression indicated that the cylinder walls expand laterally to some critical amount, at which time they become unstable and suddenly collapse into buckling. The ring-stiffeners increase the critical compressive load with their effective torsional stiffness by resisting the annular collapse of the cylinder walls into diamond shaped buckles. At an L/R ring spacing ratio of 1.0 or less, the walls tended to buckle across the ring-stiffeners.