Mechanical Transitions in Knitted Fabrics with Coarsening Patterns

Conventional knitted materials rely on periodic patterning of stitches to generate fabrics with emergent bulk elastic properties. Periodically patterning the two most common stitches, the knit stitch and the purl stitch, introduces soft deformation modes in fabrics. The boundaries between knit and purl stitches govern the emergent fabric behavior. Controlling the lengthscale of these boundaries and the periodicity of the stitches enable us to explo­­re directed fabric strain outside of the fabric's bulk stress response. We use Cahn-Hilliard dynamics to model a two-phase separation of knit and purl stitches, allowing us to explore transitions from a completely disordered state to varying stages of coarsening, concluding in a two-domain state. Our preliminary work has shown that cluster size increases bulk fabric rigidity. We explore how clusters guide strain based on their size and orientation relative to the bulk fabric. Since other coarsening statistical systems, such as the Ising model, show phase transitions at percolations, we seek second-order phase transitions that give rise to new elastic anisotropies where one direction of the fabric exhibits high rigidity, and the other, soft deformations.