Quasi-static Inflation Simulations Based on Co-rotational Triangular Space Membrane Elements

Co-rotational triangular space membrane elements are developed for the quasi-static analysis of very thin structures subjected to pressure loadings from compressible media, aiming primarily at simulations of inflation processes. By separating rigid body motion and deformational displacement, the major part of geometric nonlinearity is treated by a co-rotational filter. With the formulation, hyper-elastic and linear elastic material models are used in the local plane element expressions. Numerical experiments show that either material model can be used in the present context, but that the linearly elastic model demands an optimal reference system. The hyper-elastic form is useful also for very large expansions, but the neo-Hookean expression chosen has some limitations for large strains. Simulations are parameterized by internal over-pressure, but an amount of injected gas can be calculated from pressure and enclosed volume. The uniqueness and stability in the response of the structures must be seen as a function of either pressure or amount of gas, dependent on the precise mechanism for inflation.