The nonlinear orthotropic material model describing biaxial tensile behavior of PVC coated fabrics

Abstract

The nonlinear orthotropic material model describing the biaxial tensile behavior of PVC coated fabrics is developed in this paper. Based on energy function, the general nonlinear stress-strain relationship is derived and the second-order and third-order nonlinear equations are proposed due to the in-plane stress-strain relationship assumption. The Membrane Structures Association of Japan (MSAJ) standard testing method for elastic constants of membrane materials is adopted and three types of PVC coated fabrics are tested under five different load ratios. The measured stress-strain data are used to calculate the coefficients of proposed nonlinear equations using the Least-square method of minimizing strain. Then the stress-strain curves of five different load ratios are compared among MSAJ suggested linear orthotropic model, proposed second-order nonlinear model, third-order nonlinear model, and the test data, also the 3D strain surfaces are plotted to make an intuitive comparison. Results show that both two proposed nonlinear models have a better representation of the test data than the linear model. Finally, considering the convenience and simplicity of the calculation, the second-order nonlinear model was integrated into the finite element software and further prove its adaptability. Thus it is recommended to apply the second-order nonlinear model to engineering design and numerical calculation.