What is Fibre Curvature?

	mean fibre curvature is the average curvature of fibre snippets measured by the OFDA
	the value is expressed in degrees per millimetre (deg/mm) fibre length
	the correlation between staple crimp frequency and fibre curvature is high
	therefore low staple crimp frequency wools have low fibre curvature, while high staple crimp frequency wools have a high fibre curvature
	fibre curvature can be measured throughout processing, in the raw wool, top, roving, yarn and even the fabric, whereas it is impossible to measure staple crimp frequency past the greasy wool stage. This makes fibre curvature a potentially more useful measurement than crimp frequency
	curvature could be used as a specification for wool throughout the processing pipeline from farm to fabric. Diameter is the only other measurement which can also be used from farm to fabric
	the variation in curvature or standard deviation of curvature has been related to crimp definition or the degree of character or boldness in the staple crimp pattern
	at a certain level of curvature a high standard deviation would indicate a staple with poor character, while a low standard deviation would indicate a staple with good character

Measuring Fibre Curvature

the diagram shows how the curvature of a fibre snippet is measured. The angle A represents the amount the fibre turns in degrees from point B to point C. The OFDA measures a 200µm section of the fibre snippet and multiplies this value by 5 to convert the degrees per 200µm to degrees per millimetre (deg/mm). All measured snippets are averaged to give the mean fibre curvature. The standard deviation or variation in fibre curvature is also calculated

The OFDA is able to measure fibre curvature at the same time as it measures the mean fibre diameter and variation in fibre diameter. Therefore curvature can be easily measured on samples sent to your OFDA fleece testing laboratory for fibre diameter testing

Fibre Curvature Data on the OFDA Histogram

The fibre curvature data measured by the OFDA is presented at the top of the histogram.
The following example is used in describing the data:

Curve=74.6[57]deg/mm

This is the mean fibre curvature and standard deviation of curvature in brackets.

Curve Number=2647

This is the number of fibre snippets measured for curvature. This is less than the sample size set for measuring fibre diameter due to the fact that some fibres in the sample overlap in the OFDA slide and hence cannot be measured for fibre curvature.

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