Lateral Deformation
The reduction in the diameter of a textile yarn that occurs when it is subjected to longitudinal tensile strain is a fundamental physical behavior. In linen weaving, yarn poisson contraction is highly pronounced because of the low elasticity and high crystalline structure of flax fibers. This contraction occurs when the warp yarns are stretched during the open phase of the loom shed.
Laboratory technicians measure this diameter change using optical sensors during tensile testing.
Fabric Density
When the warp yarns stretch and undergo this lateral contraction, the spaces between them increase, which affects the weft insertion process. If the yarn poisson contraction is high, the woven fabric may develop a looser structure than intended once the tension is released. When the loom lets off the warp, the yarns expand back to their original diameter, locking the weft yarns tightly into place.
This expansion is essential for creating the dense, durable structure characteristic of traditional linen fabrics. Technicians document these diameter changes in the yarn structural analysis sheet, adjusting the loom’s reed density settings to account for the yarn’s dynamic behavior during weaving.
Fabric Shrinkage
This lateral contraction and subsequent expansion directly influence the fabric’s crimp and shrinkage properties during finishing. This structural behavior is listed in the finished fabric’s technical specification. Checking this parameter helps to prevent dimensional discrepancies in the finished cloth.
