Theoretical Analysis for the Mechanical Properties of the Knitted Structures

Knitting is a technology that has a thousand-year-old history, and can be normally seen in our daily lives. The knitted structure is constructed by the interwoven yarns that are constrained by themselves, exhibiting extreme stretchability. The mechanical properties of the knit fabric also enable their integration with flexible electronic devices. Nonetheless, it is yet problematic to expose the mechanical behaviors of knitting intrinsically. This paper investigates the mechanical characteristics of knitted structures subjected to uniaxial stretching. The analysis includes a structural assessment of the unit cell, with a focus on half of the cell accounting for symmetry. Mechanical analysis for three distinct scenarios (without elongation and friction, with elongation and no friction, with elongation and friction) is also presented. The stress–strain curve of the knitted structure and the correlation between stiffness and geometric parameters are illustrated. Additionally, simulations are carried out based on the finite element analysis, yielding consistent results with the theoretical calculations. Subsequently, a uniaxial stretching experiment is conducted, and the experimental outcomes also verify the theoretical analysis. Our analysis successfully explains the mechanical behavior of knitted structures, and also provides a reference for studying knitted fabrics with other topologies.