Laddering propagation in Weft Knit Fabrics

We use weft knit fabrics every day, as their stretchiness makes them ideal for clothes that are easy to put on and can conform to our bodies. However, their highly interconnected structures means that a single yarn breaking can lead to large visible holes which are caused by unsupported loops that propagate vertically and create a laddering effect. Here, we use experiments and simulations to investigate this phenomenon. We study various knit architectures and identify loading conditions that result in this catastrophic event. Additionally, we harness horizontal transfers and tuck stitches to design knits that ladder only along diagonal lines of our choosing. Finally, we incorporate randomness into the design to realize an ideal density of stable holes--known as yarnovers in hand knitting-- capable of localizing failure. Together, we expect this framework to enable the design of knit architectures that retain many of the desirable properties of weft knits, while being more resistant to laddering propagation.