Bending test and numerical analysis of inflatable tubes

In this paper, bending test of an inflatable, polyvinylchloride (PVC)-coated fabric tube is carried out to study the deformation, bearing capacity, and wrinkling characteristics. In order to illustrate the effect of hoop stress, two nonlinear stress-strain relationships are measured through the uniaxial tension and the biaxial tension tests. Meanwhile, a computing method based the fiber beam model is developed for the inflatable tube. This method can consider nonlinearity of membrane materials and wrinkling effect easily. The numerical results using the stress-strain relationship considering hoop stress effect are shown to more accurately predict the load-displacement response in bending test. As the test results shown, the cross-section remains basically circular and the strain distribution in no wrinkling region approximately satisfies the plane section assumption before and after wrinkling. Furthermore, the wrinkling load of the inflatable tube in bending test is compared with the numerical results. Lastly, wrinkling expansion process and wrinkling angle at ultimate load are detailed.