INFLATION OF AN ELASTIC CYLINDRICAL MEMBRANE - NONLINEAR DEFORMATION AND INSTABILITY

The axisymmetric free inflation of an initially cylindrical membrane is examined in this study. The initial thickness and radius distributions are in general non-uniform. The neo-Hookean constitutive model is used. Special attention is focused on the non-linear buckling instability under various inflation and geometrical conditions. It is found that for a given inflation pressure and aspect ratio S, the thicker the cylinder ends are, the more unstable the deformation becomes. The study also shows that for a given aspect ratio there are in general two solutions and that beyond a maximum S value no solution exists. In some cases of pressure and thickness values the number of bulges increases from one in the unstable cylinder profile as S is increased beyond a certain critical value. A similar phenomenon is observed for a long cylinder when the pressure is increased. Although the problem is formulated to account for non-uniform original thickness and radius distributions, only results based on linear thickness and radius variations are presented.