Stress-Strain Studies of Knitted Swatches

The properties of a knitted fabric are highly dependent on what stitches the fabric is made of and what patterns they are used in. Different stitches correspond to different linking topologies of the yarn that constrain the yarn configurations and therefore the overall fabric mechanics and shape. Here we examine the relationship between large scale properties of knitted swatches and the small scale yarn shape within each stitch via experiments that probe the elasticity of the swatches while imaging corresponding changes in the shape of the constituent yarn. Under stress, knitted fabric deforms not only as a bulk response, but the yarn-level deformations give rise to nonlinear elasticity. To quantify this shape change we are developing a method for tracking the 3D path of the yarn. By tracking the yarn within the fabric while we measure the stress-strain relationship, we can untangle the effects of curvature, compression, and friction on the emergent nonlinear elasticity of the textile.