Analytical methods for prediction of tensile properties of plain knitted fabric reinforced composites

This paper describes analytical models for predicting the elastic and tensile strength properties of knitted fabric reinforced composites. Owing to the looped yarn architecture, knitted fabric composites possess fiber and resin-rich regions. Initially, a geometric model has been identified for estimating the orientation of yarn in the knitted fabric. Using the unit cell approach, a 'cross-over model' has been proposed for expressing the cross-over of curved yarns of knitted fabric. Using laminated plate theory, the effective elastic properties of the yarns in the cross-over model have been estimated. Elastic properties of the composite were determined by combining the effective elastic properties of the curved yarns and the resin-rich regions. Tensile strength properties have been predicted by estimating the fracture strength of yarns bridging the fracture plane. Tensile properties of knitted fabric composites with different volume fraction of fibers were predicted. The analytical procedures have been validated by comparing one set of experimental results with the predictions. The applicability and limitation of these models have been discussed.