AN LS-DYNA USER DEFINED MATERIAL MODEL FOR LOOSELY WOVEN FABRIC WITH NON-ORTHOGONAL VARYING WEFT AND WARP ANGLE

The behavior of loosely woven fabrics (LWF) differs significantly from other types of woven fabric materials, the major difference being the significant change that the angle between the weft and warp fibers undergoes as the fabric stretching forces change. These unique characteristics have made the LWF a very important part for the functionality of some recently developed occupant protection safety devices for the automotive and heavy machine and truck industry. To efficiently model and analyze the behavior of such devices within an occupant protection model, an accurate representation of the characteristics of the LWF is needed. However, none of the many available LS-DYNA material models seem to fit well with the unique kinematics of the LWF. Therefore, the aim of this work is to present the basics of a formulation for a material model for the analysis of LWF and its implementation as a user defined material in LS-DYNA. To assess the performance of the model, results from the simulation are presented. Although relatively simple, the developed model seems to represent very well the behavior of the LWF and the simplicity of the formulation attributes to the efficiency and stability of the user defined material subroutine.