Mechanical model for the compression of weft-knitted spacer fabrics

Weft-knitted spacer fabrics are thick 3D knitted structures notable for their cushioning properties, until now their mechanical behaviour was almost only empirically compiled without being understood nor directly linked to the fabric’s properties. The current effort to describe the fabrics geometry focuses on extremely complex models when a mechanical model requires a simple one. This study investigated 4 different weft-knitted spacer layer geometries through FEA simulations, it identified the model composed of two arcs bending in opposite directions to match very well the compression behaviour of the samples. The Euler buckling load and Euler–Bernoulli beam theory were successfully used with the selected geometrical model to predict the plateau force (average error 22.7%, R² = 0.91) and the Young’s modulus (average error 38.7%, R² = 0.66) of the experimental samples. The study also investigated a compression behaviour model describing the compression of weft-knitted spacer fabrics until the plateau phase, giving predictions based on the fabric’s structure and materials showing a 35.8 ± 18.2% average error. A simple geometrical model was also developed to predict the buckling thickness of the spacer layer (average error of 15.9%, R² = 0.85). Those finding can trigger a great acceleration of research on spacer fabrics by reducing the important time allowed to empirical samples production and testing and open a path of selected production helped using formulas and solvers.