Load–extension properties of glass plain knitted technical fabrics – Part II: extensions in the course-wise and wale-wise directions

Abstract

In this paper, the load–extension behavior of glass plain knitted fabrics is investigated both experimentally and theoretically. Experiments are carried out by preparing two sets of samples for two directions, namely for the course-wise and wale-wise directions. The load–extension properties are explored by attaching dead weights to the lower ends of the samples. Therefore, while obtaining the load–extension properties in the loading direction, the contraction properties of the samples in the lateral directions are also investigated. By observing the load–extension and load–contraction curves, three stages are distinguished. The first stage can be attributed to the fabric extension or contraction. The second stage can be attributed to the yarn extension or contraction as well as to the changes in the shapes of the samples. The third stage can be attributed to the extension or contraction of the fibers. After obtaining the dimensional properties of a single loop in the knitted fabric, curve fittings are carried out for the three stages. In the rest of the work, a theoretical analysis is carried out to explain the first stage of extension and contraction that was explained above. In the theoretical work, the load–extension or the load–contraction behaviors of the arms of the loops are calculated by using the inflexional elastica theory. The extension behaviors of the loop heads, on the other hand, are calculated by using the extension of the circular ring, which was given in Part I. As a result of the theoretical analysis, some simple equations between the loads applied and the extensions or contractions are obtained. These equations for the extension or contraction rates depend on the initial dimensional properties of the loop, the bending rigidity of the material, frictional restraints and the Poisson ratio. The equations also show that an extension or contraction in the wale-wise direction follows Hooke’s Law, whereas an extension or contraction in the course-wise direction depends on the square root of the applied load. Providing some simple equations about the relation between the load and extension in the loading direction as well as between the load and contraction in the lateral direction are suggested, determining the contractions in the lateral direction in addition to the extensions in the loading direction, which can be used in engineering software in simulating fabric load–extension behaviors under loadings. Finally, the initial and the extended states of the fabric are drawn to scale by using 3DS Max computer software.