Definition of crimp
The
waviness of a fiber is expressed as ‘crimp per unit length’
The
difference in the distance between two points on an unstretched fiber and the
same two points when the fiber is straightened under specified tension. Crimp
is expressed as the percentage of the unstretched length.
The
difference in the distance between two points on a yarn as it lies in a fabric
and the same two points when the yarn has been removed from the fabric and
straightened under specified tension, expressed as a percentage of the distance
between two points as the yarn lies in the fabric.
Mathematically the Crimp can be
expressed as-
Where, ly = Length of Yarn
lf = Length of fiber
Different values of crimp for different textile application
1) Flat composite
reinforcement - <1%
2) Light weight
garments - <2-6%
3) Heavy weight
garments – 4-6%
4) Multi-layered
apparel – 10-20%
5) 3D industrial warp
interlaced – 10-200%
6) True 3D fabric –
upto 1000%
Factors affecting the crimp behavior
1) Yarn diameter ↑
- Crimp ↓
2) No of interlacement ↑
- Crimp ↑
3) Beat up force ↑
- Crimp ↑
4) Yarn and fabric
tension ↑ - Crimp ↑
5) Yarn elasticity
6) Yarn extensibility
7) EPI and PPI
8) Structure of fiber
Crimp amplitude
Crimp amplitude refers
to the extent to which the threads are defected from the central plane of the
cloth
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