The influence of temperature and humidity on the flex fatigue lives of nylon 6, nylon 6.6 and polyester fibres.
A multi-station flex fatigue tester has been
developed, allowing a wide range of environmental
settings. A detailed study of fatigue behaviour under
increasing temperature and humidity is made. In general,
an upward trend in fatigue life of all the polymers tested
is recorded with increasing temperature and humidity.
Scanning electron microscope studies of unbroken
samples under specific conditions revealed a central split
in the fibre at the point of flexure. Partially fatigued
fibres are tensile tested for their remaining strength and
their fracture morphologies examined. Finally, a
theoretical explanation of the apparent cause of increase
in fatigue life is given in relation to the development of
the central crack.