Full-stress Range Stiffness Characteristics and a New Constitutive Model for Tensile Behaviors of Coated Fabrics under Plane Stresses

The paper investigates the mechanical properties of coated polyester fabrics in biaxial monotonic tensile tests. The nonlinear behaviors of the constitutive parameters within the full-stress range were in detail analyzed, and a new constitutive model based on the specific coupling relationships between the uniaxial and biaxial flexibilities was proposed to describe the complex tensile behaviors of coated fabrics under plane stresses. Finally, the accuracy of the nonlinear model in numerical simulations was verified, and special attention was devoted to the finite element (FE) implementation of the model as an ABAQUS user material (UMAT) subroutine. It was found that the constitutive parameters of the material varied noticeably with the stress level and ratio. The stiffnesses in the larger-stress direction are nearly stress-dominated, and the stress ratios exert a more significant effect on Poisson’s ratios than that on stiffnesses in the lower-stress direction. The proposed constitutive model, considering the material nonlinearities, is validated by the good correlations between the numerical and experimental results. Additionally, the FE simulation results using the UMAT are consistent with the experiments which reveals that the constitutive model proposed and the results obtained in this work are reliable.