Experimental study and constitutive modeling on viscoelastic-plastic mechanical properties of ETFE foils subjected to uniaxial monotonic tension at various strain rates

Abstract

Apart from the well-known excellent basic properties, the mechanical behaviors of ETFE (ethylene tetrafluoroethylene) foils are more fundamental for the refined design and analysis of ETFE membrane structures. This paper investigates the nonlinear mechanical properties of ETFE foils at varying strain rates (0.01 to 10 min−1) through a combination of experiments and modeling. First, the uniaxial tensile tests at nine loading strain rates were completed on ETFE foil dumbbell specimens. The analysis of experimental results shows that ETFE foils exhibit the rate-sensitive and viscoelastic-plastic behaviors with two distinct yield points. Next, to simulate the nonlinearity of ETFE foils at the former deformation stage, the stress–strain constitutive equations at certain strain rates are established based on the generalized Maxwell model comprising one basic spring element and several basic Maxwell models. After identifying the model parameters, it is observed that the proposed model can accurately describe the viscoelastic-plastic mechanical behaviors of ETFE foils since good agreement is gained from the comparison between experimental results and model predictions. Finally, through establishing the relationship functions between model parameters and strain rates, the continuum constitutive model can be extended to predict the rate-dependent viscoelastic-plastic behaviors of ETFE foils. The experimental observations and constitutive model concerning the rate-dependent mechanical properties of ETFE foils would be helpful for the refined design, optimization and analysis of ETFE membrane structures.