EXPERIMENTAL INVESTIGATION OF INFLATABLE CYLINDRICAL CANTILEVERED BEAMS

Z. H. Zhu (Canada), R. K. Seth (Canada) and B. M. Quine (Canada)

Received April 22, 2008

Abstract

This paper investigates experimentally the bending of inflatable cylindrical cantilevered beams made of modern fabric materials. A dimensionless form of load vs deflection has been developed to characterize and generalize the bending behavior of the inflatable cylindrical cantilevered beams of different sizes, materials, and inflation pressures in a unified way for easy application. The dimensionless form of experimental results demonstrates that the inflatable beams, highly or lightly inflated, can be modeled by the Euler beam theory accurately before wrinkle occurs. The initial wrinkle is hardly noticeable in the experiments and the transition from non-wrinkle to wrinkle is mainly defined by the slope change of load-deflection curve. Compared with the experimental data, the strain-based wrinkle moment provides a lower bound prediction while the stress-based wrinkle moment gives an upper bound prediction. In the post-wrinkle stage, the Euler beam theory using a nonlinear moment-curvature model gives an upper bound estimation of load-deflection relationship while the finite element analysis based on membrane theory gives a lower bound estimation. The actual collapse moment is hard to measure in experiments due to the inflatable beam becomes unstable in the collapsed stage. However, the trends of experimental results show that the stress-based collapse moment gives the upper limit prediction and the strain-based collapse moment does not agree with the experimental data.

Keywords and phrases: inflatable, fabric beam, cylindrical, wrinkle, cantilever.