Page 358 - Fiber Fracture

340 J.W.S. Hearle

from 0% to 2%: uniform extension
at 2%: IFs reach critical stress

from 2 to 30%: zones open in succesion
in open zone: IF at eq. stress, matrix at 30%

I ! 7 -1- 7 r-

at 30% extension, all zones open

beyond 30%, IF at eq., matrix stress rises

In recovery, IFs at eq. stress
all zones contact until they disappear

Fig. 7. Schematic representation of the sequence of changes during extension of the C/H model, based on
Chapman (1969).

sharing in bundles of fibres. The strength of individual wool fibres is sensitive to fibre
variability. For example in Western Australia, there is a dry period in the summer when
feed is short. This leads to ‘tender wools’, which break at thin places in the fibres, which
gives a low tenacity if expressed on the basis of the average linear density (tex, denier)
or area of the fibre.