Tension/torsion testing of inflatable fabric tubes
Publication Name: Experimental Techniques
The focus of this work was on developing an experimental test method for characterizing the constitutive properties of the fabrics used to fabricate these inflatable beams and arches. The experimental test method must accurately determine fabric constitutive properties for the beam material when under pressure. It is also important to investigate the influence of fabric coatings and internal bladders on the overall structural performance. Preliminary modeling and other research suggest that the shear modulus is an important material property for the design of airbeams due to its strong contribution to the overall deformations of the structure.6 Further, past research suggests that fabric axial and shear moduli are highly dependent on inflation pressure.6,7 In order to accurately predict the constitutive properties of woven and braided fabrics used in airbeams, multiple stress states must be applied to the specimen. Previous experience has shown that one of the key response aspects of inflatable beams is localized wrinkling or buckling in regions of compressive strain.2 However, airbeams can sustain very large load-induced deformations without tearing or failure of the fabric. Thus, nondestructive test methods should be used to obtain the material properties of airbeam fabrics. However, obtaining repeatable test results is a significant challenge due to the complex nature of the fiberÐtow interactions combined with the pressurization of the beams. This article presents the development of a novel, tension/torsion testing procedure used to determine the fabric constitutive properties for inflatable beams.