Geometrically Poisson’s Ratio of the Polyester Double-bar Warp-Knitted Structures on the Jamming Point

The main aim of this study is to present a new theory which shows the relationship between the warp knitted structures and some parameters of the fabric stiffness matrix. One of the important factors in this matrix is Poissonʹs ratio that influence on the mechanical behavior of knitted fabric. The theoretical loop model based on geometry is used to investigate the tensile behavior of the fabric. The proposed loop model is basically based on the previously published assumption of fabric structure. This geometrically loop model is assumed to be two dimensional, but this model is applicable to analysis of the three dimensional structures as well. The specimen fabrics are produced with various two bar warp knitted fabric structures with changing the underlap length of the front or back guide bar (Tricot, Locknit, Reverse Locknit, Satin and Sharkskin) from polyester yarn. A uni-axial tensile tester is used for measuring the experimental work and geometrical parameters such as wale and course spacing of the fabrics are obtained during the extension. The model predicts the variation of Poissonʹs ratio with longitudinal strain in all structures on the jamming point. Comparison between experimental and theoretical results for variety of fabric structures shows reasonable agreement between predicted and measured extension behavior of warp knitted fabric.