Consistent mesoscopic mechanical behaviour model for woven composite reinforcements in biaxial tension

The knowledge of the mechanical behaviour of woven composite reinforcements is necessary to analyse and simulate the forming processes of these composites. Tensile rigidities of fabrics are large compared to others and they mainly drive the deformation. The tensile behaviour of woven reinforcements is specific because the undulations due to weaving lead to strong non-linearities at the beginning of the loading. These undulations in both directions lead to a biaxial phenomenon. In the present paper, a simplified biaxial tensile model gives the tension response for all warp and weft strains with very fast computations. It can be used to carry out optimization of the parameters of the woven reinforcement. This model is based on a consistent description of the fabric geometry. Contrary to most others models it strictly avoids spurious voids and interpenetrations of the yarns due to geometrical assumptions. The geometrical model remains nevertheless simple and requires three or six dimensional parameters according to whether the fabric is balanced or not. The simplified mechanical model based on this geometrical description is a truss type model. From the local equilibrium equations of woven yarns, it relates the tensions in the warp and weft directions to the axial strains in these two directions. The tensile surfaces are obtained very quickly and are in good agreement with results of experimental biaxial tests. (c) 2007 Elsevier Ltd. All rights reserved.