Nesting in textile laminates: geometrical modelling of the laminate

The nesting of reinforcements in textile laminates is studied using a 3D geometrical model of a woven, braided and non-crimp stitched fabrics in the relaxed and sheared state. The following fabric parameters were varied in the numerical experiments: flatness of the yarns, tightness and balance of the fabric, fabric weaving/braiding/knitted pattern, number of layers and degree of shear. Monte-Carlo modelling of the random nesting generated data on the influence these parameters on the average laminate thickness and fibre volume fraction and distributions of these characteristics of the laminate. The results show that the nesting effect becomes more pronounced with the decrease of the fabric tightness and the decrease of the float length in the weave. For non-circular yarns, an average dimension of the cross-section proved to be a valid normalizing parameter to generalize the nesting behaviour of fabrics. Shear deformation of the fabric decreases the nesting. For non-crimp stitched fabrics the nesting is defined by the stitching pattern.