Dynamic failures in knits

While knit materials are ubiquitous in our daily lives due to their compliance and manufacturability, their topology induces a failure mode. This failure mode is commonly seen as runs in women's stockings, where a single torn yarn leads to large defects that permanently weaken the fabric. Constrained by the knit's topology, this defect always moves along the warp direction of the fabric; here, we study the dynamic process of these defects and show that their propagation shows an analogy with the propagation of transition waves. Using a spring-mass model, we quantify how changing biaxial pre-strain in the knit affects the propagation of the defect through the knitted fabric and compare these predictions to experiments. This work aids in understanding how knit materials, such as those used in soft wearable systems, fail in dynamic processes.