Air Jet Spun Yarn Mechanics in Elastic Woven Fabrics
Air jet core-spun yarns deliver torque-free, pill-resistant elastic wovens by locking polyurethane filaments inside parallel staple cores bound by vortex wrappers.
Core Sheath Slippage
Sheath Separation
Physical failure of a core-spun yarn occurs when the outer layer of staple fibres slides along the length of the internal filament. This core sheath slippage results in bunched sections of fibre known as bird nesting followed by exposed lengths of the bare core. Such movement typically triggers during the high-friction environment of the weaving loom or during the needle penetration of high-speed sewing machines.
Slip Mechanism
Low surface friction between a smooth synthetic core and a dry natural fibre sheath prevents the two components from gripping each other effectively. If the twist inserted during spinning is too low, the frictional force holding the staple fibres in place fails to overcome the axial tension applied during processing. This core sheath slippage often becomes apparent at the edges of garments where seam stress pulls at the yarn structure.
Detection Protocol
Laboratory testing involves the use of a constant rate of extension machine to measure the force required to move the sheath. A sample of the yarn is clamped and the core is pulled until the sheath begins to pile up. Higher values on this test indicate a more stable yarn construction.
Fabric Consequence
Fabrics containing yarn with poor adhesion suffer from unsightly surface irregularities and reduced seam strength. This failure necessitates a complete halt in production to adjust the roving twist or the spinning tension.