Snap-through instability of short and long hyperelastic tubes under inflation

We study the bulging behavior of thin cylindrical balloons with various aspect ratios under internal pressure loading. Although the localized bulging of long circular tubes has been extensively studied experimentally and analytically, there is a lack of investigation on the deformation of short and moderate-length tubes. For non-cylindrical balloons, a recent simulation study on the inflation of spheroidal shells reported the boundary aspect ratio that determines the occurrence of localized bulging. We first experimentally investigate the bulging behavior of hyperelastic tubes under internal pressure by systematically varying the aspect ratio. We also explore the effect of prestretch both on the critical bulging pressure and the instability. Then, we compare our experimental results with analytical solutions. Furthermore, we combine multiple tube segments to achieve complex deformation. Our results can be used to understand inflatable biological structures and design soft pneumatic actuators.1