Bifurcation Analysis of Unbending and Eversion of a Bilayer

This study analyzes the finite deformation and the bifurcation behavior associated with the opening (i.e., unbending and eversion) of a bilayered cylinder, with layers made of hyperelastic and incompressible materials. The solution to the finite deformation problem reveals interesting stress states, including the presence of multiple neutral axes, as well as in certain cases the absence of neutral axes. Additionally, we show that the presence of a second layer can significantly impact the bifurcation behavior of the system, when compared to the homogeneous cylinder. The addition of a stiff, thin layer (i.e., coating) both at the tensile as well as at the compressive side can significantly affect when a system loses stability on applying unbending and eversion.