Contributions of Strain Energy and PV-work on the Bending Behavior of Uncoated Plain-woven Fabric Air Beams

The bending performance of fabric air beams varies significantly from conventional beams. Both are dependent upon the constitutive relations of the material, but air beams are further dependent upon the thermodynamics of the internal air. As the governing energy balance demonstrates, air beam bending is dependent upon strain energy and PV-work (air compressibility). The relative importance of these terms will vary with pressure, volume changes and shear deformations. To this point, a swatch of uncoated plain-woven fabric was subjected to mechanical tests and its material properties determined. Attempts at using the stress-strain measurements in air beam models, assumed constructed with the same fabric, were made. The models accounted for fluid-structure interactions between the air and fabric. Homogenization methods were used and were necessary to provide computational efficiencies for the macro-scale air beam model while attempts were made to incorporate the combined extension and shear behaviors observed during the material tests. Bending behavior was numerically investigated for several constitutive cases. The models were solved with the ABAQUS-Explicit program over a range of pressures. The fabric strain energy and PV-work were tracked and compared. It was concluded that strain energy and PV-work must be considered in deflection analyses of uncoated plain-woven fabric air beams.