Computationally Efficient Finite-Element Modeling of Braided Inflatable Structural Members with Axial Reinforcing

Abstract

Braided, inflatable structural members with axial reinforcing cords have the ability to accommodate loading with a low mass and small storage volume. These members are particularly attractive for space-based applications. There is currently a need to develop computationally efficient structural design methodologies for these unique, compliant, inflatable structural members so that engineers can more-effectively perform structural analyses and conduct structural-optimization studies. In this paper, an analysis methodology is developed for the three-dimensional, large-displacement, materially nonlinear behavior of these inflatable, slender members that includes the effect of the internal inflation pressure. A three-dimensional, corotational, flexibility-based fiber-beam element is employed to handle geometric and material nonlinearities. Comparisons are made with the in-plane and out-of-plane response of component-level testing of inflatable straight tubes, as well as to higher-fidelity shell-based finite-element models. The model results show good agreement with both shell-based finite element (FE) models (with a significantly decreased number of degrees of freedom), and results of component-level tests well past the point where test specimens lose internal prestress due to bending and exhibit a nonlinear response.