One of the physical tests performed within the scope of fabric performance tests in the textile sector is shear resistance tests. As is known, during the weaving of fabrics, there are two yarn systems that form the fabric: weft yarns and warp yarns. The weft threads are those which extend transversely of the fabric, ie perpendicular to the fabric edge. The warp yarns are those which extend across the fabric and are perpendicular to the weft yarns. The weft and warp threads pass through each other to form the fabric texture.

Yarn slippage in fabrics is caused by weft yarns on warp yarns or warp yarns on weft yarns due to some physical effects. When the yarn slides in the fabric texture, the fabric surface deteriorates. Most of the time these deformations turn into tears and openings on the face of the fabric. Of course, this shortens the service life of the fabric.

The weft and warp yarns that make up the fabric must thus be resistant to slippage and unwinding. This resistance is called slip resistance. There are many factors that affect slip resistance. The type of fiber from which the yarn is obtained, the yarn twist, the weaving density of the fabric and the weave of the weft and warp yarns, adversely affect the slip resistance.

Yarns do not change their state when weaving and using fabrics with high slip resistance. For this reason, slip resistance of fabrics is important in textile sector.

Shear resistance tests of fabrics in authorized laboratories are carried out on the basis of standards published by domestic and foreign organizations. The main standards considered in this regard are:

• TS EN ISO 13936-1 Textile - Determination of shear strength of yarns in woven textile products - Sewing method - Part 1
• TS EN ISO 13936-2 Textile - Determination of shear strength of yarns in woven textile products - Sewing method - Part 2
• TS EN ISO 13936-3 Textile - Determination of the slip resistance of yarns in woven textile products - Part 3: Needle fastening method

Technically speaking, for a certain amount of displacement of yarns parallel to the seam in the fabric, the force to be applied perpendicular to the seam is called slip resistance in woven fabrics. The sewing method of the above standards is applied only to woven fabrics. This standard does not apply to other textile products and belts.

Shear resistance tests are carried out as follows:

• To determine the slip resistance in the warp direction, five woven fabric samples with 100 mm length in the warp direction and 350 mm length in the weft direction are used for the seams to be sewn.
• To determine the slip resistance in the weft direction, five woven fabrics with 100 mm length in the weft direction and 350 mm in the warp direction are used for the seams to be sewn.
• Test environment is prepared in accordance with TS EN ISO 139 (Textile - Conditioning and standard atmospheric conditions for tests) standard for tests.
• As the sewing machine, 3000 stitch / minute sewing machine is used which makes straight stitch with single needle. As the sewing thread, polyester white yarn with elongation at break not more than 20 percent is used.
• Test results are obtained by sewing in accordance with the conditions described in the standards.

The slippage and deformation of the fabrics is an important indicator that affects the properties of the fabrics to be draped and foldable, their attitude and shape. Shear resistance also affects the flexural and durability properties of woven fabrics.

Shear deformation is the distortion caused by the forces applied in the direction that will form an angle in the width and length direction of the woven fabrics. It is natural that fabrics are exposed to such forces during their daily use. Shear deformation in woven fabrics, warp and weft yarns due to the effect of various forces change the direction of the connection point