Identification of Bodner-Partom model parameters for technical fabrics

The thorough analysis of modeling technical fabrics behavior with the viscoplastic Bodner-Partom constitutive law is presented. The study has been focused on differences between the warp and weft direction of the material. To obtain the model's parameters only the uniaxial tensile laboratory tests with three different, but constant strain rates are required. The parameters have been found for polyester fibers PVC coated fabrics: VALMEX and AF9032, respectively. An extensive attention has been paid to the behavior of the textile in the weft direction, therefore for this direction the supplementary cyclic tests have been performed and analyzed. Consequently, the same identification procedure for the warp and weft direction of the fabric, taking into account the appropriate longitudinal stiffness, has been successfully implemented. Two new approaches for the weft threads direction description have been proposed. All identification results have been examined through computer simulations producing sound convergence with the laboratory results for both analyzed materials.