Uniaxial tensile mechanical properties and model parameters determination of ethylene tetrafluoroethylene (ETFE) foils.

This study concerns the uniaxial tensile mechanical properties and model parameters determination of ethylene tetrafluoroethylene (ETFE) foils used in structural engineering for membrane structures such as roofs and claddings. On one hand, a series of uniaxial tensile tests under a wide range of temperatures and constant loading speeds were conducted. The experimental results were processed with mathematical methods to determine the mechanical properties, such as first yield stress and elastic modulus. It is obtained that the first yield stress and elastic modulus decrease with increasing temperature but increase with the increasing loading speed. In detail, for the elastic modulus, the dimensionless ratio of the difference between the maximum and minimum values to the maximum value are 91% and 27% for temperature and loading speed tests; for the first yield stress, the dimensionless ratio are 82.9% and 19.2%, respectively. This indicates that the effect of temperature on mechanical properties is greater than that of loading speed when considering the normal working conditions. On the other hand, a constitutive model based on viscoelasticity–plasticity of semicrystalline polymers is employed for ETFE foils. The material parameters are determined with a numerical method based on the Runge–Kutta and least squares methods. The numerical results are in good agreement with the experimental results with a maximum deviation of 6.2%, demonstrating that this model could correctly predict the stress–strain relation of ETFE foils. [ABSTRACT FROM AUTHOR]