Comparison of stiffness properties of common coated fabrics

Woven coated fabrics commonly used for tensile membrane structures are PVC-coated polyester fabrics and PTFE-coated glass-fibre fabrics. Regarding the stiffness of these materials, membrane structure experts frequently point out that glass/PTFE fabrics are “stiffer” than PES/PVC fabrics. However, this statement cannot be verified by existing literature, although numerous publications deal with the stress-strain behaviour of coated woven fabrics. Available stress-strain test data are almost impossible to compare, mainly because published stress-strain data for glass/PTFE refer to materials with higher strengths than the published test data for PES/PVC materials. The aim of the present paper is to compare the stiffness properties of PES/PVC and glass/PTFE fabrics with identical tensile strength properties by means of theoretical investigations and uniaxial tensile tests. The results demonstrate that glass-fibre fabric indeed exhibits a higher tensile stiffness than comparable polyester fabric for typical working stress ranges between the prestress level and the maximum design strength. However, for lower stress ranges up to approximately three-quarters of the design strength, the tensile stiffness of glass-fibre fabrics is identical with or even lower than that of comparable polyester fabric. The transverse strain is considerably higher for the glass-fibre fabric throughout.