Simulation of the spherical deformation of biaxial weft-knitted fabrics using meso and macro models

Abstract

The main objective of this research is the numerical simulation of the spherical deformation of biaxial weft-knitted fabrics produced based on 1×1 rib structure. Biaxial knitted samples were produced on a modern flat knitting machine using the polyester yarn as the fabrics stitch background and the nylon yarn as the reinforcing inlays. Bagging test was applied to the samples for investigating their behaviors during the spherical deformation. Considering two different approaches in analytical studies, the test procedure and its results were simulated through the Abaqus software environment based on the finite element method. In the first approach, by the help of Python scripting, the real structure of the fabric was simulated based on a unit-cell of the three-dimensional loop model for 1×1 rib structure comprised of warp and weft reinforcing yarns. In the second approach a constitutive equation was used for macro modeling of biaxial knitted fabrics. The stiffness matrices of these fabrics were assumed to be a combination of stiffness matrices for both 1×1 rib based-structure and reinforcement yarns. To implement the constitutive behavior in Abaqus software, a VUMAT subroutine was provided. To evaluate the accuracy of the two suggested models, fabric spherical deformation was simulated and results were compared with experimental measurements. The findings showed that the both models can successfully predict the spherical deformation of the biaxial weft knitted fabric.