Mechanical behavior of aerostat envelope and constitutive modeling

To meet the requirements of load-bearing and special environmental adaptability, the envelope of near-space operational aerostats consists of multiple layers, such as high-performance fiber fabrics, helium barrier layers, weather layers, and adhesive layers. Since the internal pressure inside the envelope directly determines load-bearing capacity of the aerostat, it is necessary to develop a reliable constitutive model to predict the equivalent mechanical properties of the envelope, which therefore, lays the foundation for strength and life evaluations of the airship. Effects of fiber fabrics and functional layers on the equivalent mechanical properties of the envelope were investigated by experimental characterizations. Based on experimental results, an equivalent constitutive model was developed to study the anisotropic and nonlinear mechanical behavior of the envelope. For both uniaxial and off-axis tensile conditions, predictions on the effective stress, yarn shear angle and specimen cross-sectional contraction agree well with experimental results. The combined experimental and numerical studies have led to insightful understanding between the overall mechanical response and microstructure deformation of the envelope.