Developing a Constitutive Model for Knitted Fabrics

Knitting is the manipulation of a one-dimensional yarn into a two-dimensional lattice of interconnected loops and a craft that has been done for centuries in both manual and mechanized settings. In comparison to weaving, knitted fabrics have more elastic properties and as such are typically used for cuffs, hats, and socks. Knitted fabrics have two basic stitches: a new loop is pulled through an existing loop from the front (purl) or the back (knit). Previous simulations show how knitted fabric behaves differently for different fabric types, indicating that fabric behavior has a large dependence on the topology of the stitches themselves. Beyond fabric types, the yarn itself has several mechanical properties that can be experimentally measured, such as the bending modulus, compression modulus, and length of yarn per stitch. By exploring the parameter space of yarn properties for a single fabric type, we can further determine how yarn elasticity and manufacturing processes individually affect fabric behavior. These studies also allow us to identify the properties that have the largest effects on the mechanics and develop a constitutive model to link yarn and fabric elasticity.