Computational determination of in-plane shear mechanical behaviour of textile composite reinforcements

The knowledge of the mechanical behaviour of woven fabrics is necessary in many applications in particular for the simulation of textile composite forming. This mechanical behaviour is very specific due to the possible motions between the fibres and the yarns. In this paper, the in-plane shear behaviour is analysed from virtual tests on the Representative Unit Cell. The in-plane shear strains can be very large (up to 50 degrees) in case of draping on a double curved surface. These virtual tests avoid performing tricky experimental tests. The presented 3D finite element analyses involve two main specific aspects. Firstly the boundary conditions have to render the periodicity at large deformations and, in some cases, the evolution of contacts between neighbouring yarns during the motion. Secondly the yarn that is made of thousand of fibres is modelled as a continuous medium but its constitutive law has to take its fibrous nature into account. For that reason a rate constitutive equation using a specific objective stress rate is used. It is based on the rotation of the fibre. The analysis is performed for two unit cells. Both results are in good agreement with the experiments, but the use of one of the cells turns out to be much easier. (C) 2007 Elsevier B.V. All rights reserved.