Common identification methods for warp knitted and weft knitted fabrics are as follows:
1. Stretch the sample by hand and observe the weave direction of the yarn to judge whether it is warp knitted or weft knitted fabric. The extension line of warp knitted fabric is zigzag along the longitudinal direction, and the extension line of weft knitting is in a zigzag shape along the transverse direction. Refer to the microstructure of the yarn under the microscope. (usually, weft knitted fabrics have the same grain direction on both sides, and warp knitted fabrics are perpendicular.)
2. If the sample has full width, generally speaking, the fabric with or without selvage is warp knitted fabric, and the fabric without selvage is not necessarily weft knitted fabric. Sometimes, the edge of warp knitted fabric will be cut.
3. Trim the sample slightly along the grain, and then try to tear the four sides of the sample in turn. One side of the weft knitting will come apart and the whole yarn will be pulled out. Warp knitting does not come apart.