Parametrized regression model and experimental validation for an effective spacer fabric compression

Warp-knitted spacer fabrics are featured by a 3d integral structure consisting of two warp-knitted fabric layers, which are kept on distance by vertical threads. This structure enables the realization of several functions like mechanical cushioning, permeability for air and moisture, and thermal insulation. Due to these functions, spacer fabrics can be used as moisture and thermal-regulating functional components in various sewing products, whereby compression stability is essential for the functionalities mentioned above. These can also be influenced locally by stitching. A numerical tool is preferred to compute the mechanical properties in an accurate way, taking into account the varying sewing parameters. This study's objective is to extend the macroscopic material law for spacer fabrics through numerical analysis of experimental data. For this purpose, 3d samples stitched at varying intervals were tested by a compression test. A regression analysis was applied to predict the compressive stress for each structure. The research steps included representing and approximating the coefficients and potencies for the experimental curves as explicit functions of the distance between the stitch lines. An effective contact model for spacer fabrics with stitches was developed, which is to be expressed in the form of seam distance in terms of the effective compression of the spacer fabrics. Thus, in the future, it will be much easier to predict the effective properties for selected semi-analytical applications with such materials.