Quantifying Core Sheath Shear Slip in Jet Processed Stretch Fabrics under Extended Static Load
Exceeding 3.5 elastane draft without heat-setting crosslinking causes sheath slip under prolonged static load.
Dual-Core Spandex
Elastic Architecture
Elastic core stabilization maintains the shape of stretch denim by incorporating a rigid reinforcement alongside the flexible element. Dual-core spandex utilizes two distinct core components, typically a polyester strand alongside an elastane filament, both wrapped in a staple fibre sheath. This configuration provides a high recovery force that prevents the bagging often seen at knees and elbows.
Stress Response
Rigid inner filaments limit the total extension of the elastane to protect the yarn from over-stretching and permanent deformation. When the fabric reaches its designed limit, the polyester core carries the load. This mechanism ensures that the garment returns to its original dimensions after tension is released.
Fabric Stability
Stability in heavy-weight bottom fabrics improves because the dual-core spandex provides a higher modulus than traditional elastic yarns. Industrial finishing processes like mercerization or intensive stonewashing do not degrade the internal structure as easily. The outer sheath remains intact, preventing the elastic from snapping or poking through the fabric surface.
Verification Method
Quality control technicians measure the power and recovery of these yarns using standardized cyclic extension tests. Higher force at a specific elongation indicates a successful core-spinning process. Because the two cores work in tandem, the resulting fabric exhibits a firmer handle that mimics non-stretch textiles while providing the comfort of a flexible material.