Nonlinear finite element analysis of inflatable beams made from orthotropic woven fabric

This paper was devoted to the three-dimensional nonlinear finite element analysis of inflatable beams. The beams under consideration are made of modern textile materials and can be used as a load-bearing beams or arches when inflated. A 3D Timoshenko beam with a homogeneous orthotropic woven fabric (OWF) was proposed. The model took into account the geometric nonlinearities and the follower force resulting from the inflation pressure. The use was made of the usual total Lagrangian form of the virtual work principle to perform the nonlinear equilibrium equations which were discretized by the finite element method. Two kinds of solutions were then investigated: finite elements solutions for linearized problems which were obtained by the means of the linearization around the prestressed reference configuration of the nonlinear equations and nonlinear finite element solutions which were performed by the use of an optimization algorithm based on the Quasi-Newton method. As an example, the bending problem of a cantilever inflated beam under concentrated load was considered and the deflection results improve the existing theoretical models. As these beams are made from fabric, the beam models were validated through their comparison with a 3D thin-shell finite element model. The influence of the material effective properties and the inflation pressure on the beam response was also investigated through a parametric study. The finite elements solutions for linearized problems were found to be close to the theoretical results existing in the literature. On the other hand, the results for the nonlinear finite element model were shown to be close to the results for the linearized finite elements model in the case of high mechanical properties and the nonlinear finite element model was used to improve the linearized model when the mechanical properties of the fabric are low.