Experimental analysis of tensile behaviors of polytetrafluoroethylene-coated fabrics subjected to monotonous and cyclic loading

This paper presents the tensile behaviors of polytetrafluoroethylene (PTFE)-coated fabrics subjected to monotonous and cyclic loading. First, uniaxial tensile tests are conducted to study the uniaxial cyclic behaviors, in which the effects of stress amplitude and temperature on the fabrics are studied. Then, biaxial tests are carried out to analyze the biaxial cyclic behaviors with different stress ratios. Finally, the mechanical properties of PTFE-coated fabrics without initial loading and after cyclic loading are compared. The results show that the tensile behaviors of PTFE-coated fabrics are asymmetric and affected obviously by loading protocols, which are concerned with the woven structure of substrate and properties of yarns. After cyclic loading, the significant stiffness strengthening and the linearity of tensile behaviors becomes obvious, while the discrepancy between the elastic modulus of the warp and the weft decreases. Compared with the new material without initial loading, the material tensile strength after cyclic loading remains almost unchanged, which may be related with fewer cycle numbers. The tensile behaviors under cyclic loading are mainly related with stress amplitude, temperature and woven structure of substrate. With temperature increasing, the degree of stiffness strengthening after cyclic loading increases. The effect of loading history on the mechanical properties of PTFE-coated fabric is obvious, and different constitutive constants should be conducted regarding different design stages.