Changing the Cross-Sectional Shapes of the Prestressed Rovings in Warp-Knitted Glass and Carbon Reinforcing Fabrics

Abstract Understanding the changes in the reinforcing fabrics during loading is an urgent task, as it provides the necessary information for predicting the mechanical behaviors of fabrics and fabric-based composites. The effect of the loading level on the internal structure of the reinforcing fabrics was evaluated through the experimental studies on samples of warp-knitted glass and carbon reinforcing fabrics with different stitch patterns, including tricot and pillar stitches. To establish relationships between the changes in the roving cross-section during loading, optical microscopy was used. Several prestressed levels corresponding to 0%, 25%, 50%, and 75% of the tensile strength of the reinforcing fabric were analyzed. Based on the constructed geometrical models, a statistical analysis of fiber distribution was carried out. With increasing loading, the cross-sectional shape changes significantly in the case of the tricot stitch. In contrast to the fabric with tricot stitch, the cross-sectional shape of the fabric with pillar stitch slightly decreases with an increase in the applied load.