Stability of lobed balloons

This paper presents a computational study of the stability of simple lobed balloon structures. Two approaches are presented, one based on a wrinkled material model and one based on a variable Poisson's ratio model that eliminates compressive stresses iteratively. The first approach is used to investigate the stability of both a single isotensoid and a stack of four isotensoids, for perturbations of infinitesimally small amplitude. It is found that both structures are stable for global deformation modes, but unstable for local modes at sufficiently large pressure. Both structures are stable at any pressure if an isotropic model is assumed. The second approach is used to investigate the stability of the isotensoid stack for large shape perturbations, taking into account contact between different surfaces. For this structure a distorted, stable configuration is found. It is also found that the volume enclosed by this configuration is smaller than that enclosed by the undistorted structure.