Consistent 3D geometrical model of fabric elementary cell. Application to a meshing preprocessor for 3D finite element analysis

Many different methods can be used to obtain a composite part. Among them, several require the forming of a dry fabric before the resin is injected. The mechanical properties of the obtained part depend to a large extent on the mechanical behavior of the dry fabric. Experimental methods are efficient to identify this behavior, but they need to be complemented with numerical approaches. Among the numerical approaches, 3D finite element simulation is very interesting but requires an accurate 3D mesh of the fabric elementary cell. In this paper, we are proposing a new consistent 3D geometrical model of 2D fabrics. Experimental observations using different optical processes have been performed in order to determine real yam geometry in different cases of yarn structure and weaving. The analysis of these results helps us define the accurate generic 3D model of a yarn shape when it is weaved. Using this model of a yam, a consistent 3D geometrical model of 2D fabrics is presented. One particularity of this model is that it ensures a realistic contact surface between yams without interpenetration for all types of weaving. The section shape varies along the trajectory, so that the influence of contact between yarns on their cross section shape can be taken into account. This model can be easily identified using three to seven parameters measured on a real fabric. A meshing preprocessor based on this geometrical model is then developed. It substantially reduces the time needed to obtain an accurate hexahedral mesh of the elementary cell of a fabric. This is an important point for the 3D finite element simulation of fabrics, which is a powerful method to investigate their mechanical behavior. Examples of shear and biaxial extension are presented to show the efficiency of the whole simulation chain. (c) 2005 Elsevier B.V. All rights reserved.