The waviness of a fibre, i.e. the condition in which the axis of a fibre under minimum external stress departs from a straight line and follows a simple or a complex or an irregular wavy path.
1. In its simplest form, crimp is uniplanar and regular, i.e. it resembles a sine wave, but it is frequently much more complicated and irregular. An example of three-dimensional crimp is helical.
2. Crimp may be expressed numerically as the number of waves (crimps) per unit length, or as the difference between the distance between two points on the fibre when it is relaxed and when it is straightened under suitable tension, expressed as a percentage of the relaxed distance.
b) In Yarn
The waviness or distortion of a yarn owing to interlacing in the fabric.
1. In woven fabric, the crimp is measured by the relation between the length of the fabric test specimen and the corresponding length of yarn when it is removed therefrom and straightened under suitable tension. The crimp may then be expressed numerically as a percentage or as a ratio, i.e. the ratio of yarn length to fabric length. In both methods, fabric length is the basis.
2. Although this definition could logically be applied to knitted fabrics or fabrics of pile construction, it is usual to employ special terms, e.g. stitch length, terry ratio.