Hair Mono Filament Testing
Tensile testing is the simplest method for measuring the strength of a hair fibre. Hair strength correlates with the amount of damage that it has undergone, whether from UV, bleach or mechanical treatments.
If the diameter of the hair is accurately measured using a micrometer, fundamental measurements of breaking stress, breaking strain, energy to failure and elastic modulus can be calculated. Hair fibres can be variable, so a large number of repeats will aid with data interpretation.
This type of test is generally performed at a constant strain rate (constant loading arm velocity), but fatigue testing can also provide useful information, as it is more imitative of the trials and tribulations undergone by a head of hair over its lifetime. In a fatigue test, a large number of small displacement cycles are performed. The sample is stretched a small distance, then a fluctuating movement applied for a given number of cycles, or until breakage.
