Development of 3D knitted fabrics for advanced composite materials

The purl evolution is often used to produce knitted fabrics on flat machines and is characterised by specific 3D stitch geometry. There are a small number of models defined in the specialty literature for the stitch length calculus. The paper presents the calculus methodology for the purl stitches, emphasising the calculus specifics for stitch height and for stitch length. The idea of normal and conventional row height is introduced in the paper. These heights are correlated through the fabric packing. The paper defines the limits (minimum and maximum) between which the purl stitch is placed. The stitch length calculus is based on the real purl stitch geometry within the fabric. The elaborated model is validated using experimental data that are processed to verify their correlation to the model. The model for the purl stitch geometry will eliminate the simplifying hypothesis currently use.