Digital image correlation for measuring strain concentration and distribution mechanics in holed spacer fabrics for knee brace applications

Knee braces are often utilized to prevent injury, but brace slippage caused by differences in deformation between the skin and the brace materials can compromise their effectiveness. A knee brace with a hole aperture at the patella level could mitigate this issue by reducing the contact area, yet a lack of characterization of hole shapes limits our understanding. This study explores spacer fabric as a viable material for knee braces and investigates the impact of hole shapes on strain concentration using Digital Image Correlation (DIC) for precise measurement. The findings reveal that spacer fabric deform inconsistently under tensile strength, with variations ranging from 8 to 17%. Additionally, hole shapes significantly influence strain concentration at the edges, with variations up to 26.4%. Traditional strain concentration theory was found to be inadequate for spacer fabrics because the non-uniform structure relies on knit columns. Creating holes by interrupting these columns is suggested to significantly affect the strain field. These results enhance the understanding of spacer fabric behavior and provide guidelines for better hole design, potentially improving knee brace performance and reducing slippage.