Numerical Studies on the Air–Membrane Interaction of ETFE Cushions

Abstract

Inflated membranes are popularly used in civil and aerospace engineering. They are flexible and their behaviors are featured by the interaction between the inner air pressure and deformation of the enveloping membrane (air–membrane interaction) which has not yet received attention in the literature. This paper aims at studying the air–membrane interaction and its influence on the static and dynamic properties of an inflated membrane by numerically analyzing a square ETFE (ethylene–tetrafluoroethylene) cushion. To account for the air–membrane interaction, the inner air was regarded as a linear potential fluid in developing the governing equations. The finite element model was derived from the discretized equations and verified through comparison with experimental results and those in the literature. Thereafter, the air–membrane interaction and its variation with influencing factors were investigated in the static and dynamic analysis by comparing results from the verified finite element model with the numerical solutions where the inner air was treated as the traction boundary conditions of the enveloping membrane. Results of this study indicate that (1) air–membrane interaction becomes more prominent with increasing external load and is gradually weakened with a rise in the frequency order; (2) air–membrane interaction makes the top membrane joined with the bottom membrane in the deformation and vibration; and (3) air–membrane interaction is strengthened with an increase in the initial inner pressure or geometric dimensions, but weakened when the membrane thickness or rise–span ratio increases. The present research is helpful to the understanding of the role the inner air plays in the behavior of inflated membranes, and may therefore improve the accuracy in analysis and the rationality in the design.