A simple technique for characterizing flexible materials using pressurised tubes

This work numerically and experimentally investigates the deformation of flexible tubes under positive transmural pressure. The numerical analysis employs asymmetric static simulations using a neo-Hookean model defined by the shear modulus, and is validated through experiments with two different materials. A dimensionless study was conducted to evaluate the variation in tube volume as a function of transmural load (the ratio of transmural pressure to shear modulus), considering different lengths and thicknesses. For sufficiently slender tubes, reducing the thickness by one order of magnitude requires a transmural load smaller by the same order to achieve the same deformation. Additionally, tube length does not affect deformation for relatively long tubes. Therefore, for tubes that are both sufficiently long and slender, the volumetric deformation as a function of the ratio between transmural load and dimensionless thickness collapses onto a single curve, simplifying deformation prediction. This curve enables the shear modulus to be estimated from a single experiment using a manometer, facilitating material characterization.