To simulate the behaviour of textiles, three major characteristics are important, kinematic fibre interaction, shear behaviour, and thickness changes of the fabric caused by shearing. Instead of anisotropic continuum mechanical models normally used, a macroscopic finite element coupled with an internal unit cell, made of beam elements is proposed here. The beam elements represent the yarns. The method is generalized for unit cells with parallelogram shaped unit cell geometries. The coupled unit cell model can improve finite element simulations, in terms of calculation time and modelling effort, because the major characteristics named before can be described in detail by the unit cell without using full-scale models.

Today finite element simulations for draping are based on anisotropic continuum mechanical models. Effects like fiber separation, fiber sliding and Poisson's ratio greater than 0.5 are not describable with such an approach. The work presents a new finite element formulation for plain woven fabric involving an internal unit cell. The unit cell is a finite element model based on beams. This beam model represents the kinematics and the interactions of the rovings of the real fabric. This approach offers possibilities to overcome the limitations of models based on a continuum. The new finite element formulation is implemented in the user environment of the industrial explicit FE software PAM-COMPOSITES from the ESI group.

The presented work deals with the simulation of problems related to dry fabric materials. Especially draping over double curved molds is a huge field for industrial simulation methods. Although industrial solutions are available, there are still many open issues. The main reason for these issues is the fact that the mechanical behavior of dry fabric layers is not describable with a standard continuum mechanical approach because the fabric is not a continuum. The idea of the approach presented here is to model the inner structure of the fabric with a unit cell consisting of crossed beams and to couple this inner structure with a macroscopic membrane element (coupled multi-scale approach).