Accelerated creep testing for aramid fibres using the stepped isothermal method

The article shows how the stepped isothermal method (SIM), which has hitherto been applied to polyester fibres, can be applied to the creep testing of aramids. The method is an improvement over the time temperature superposition method since a complete creep curve can be obtained from a single fibre. However, adjustments have to be made to account for the temperature changes and the past history of the fibre. Techniques are shown for performing these adjustments and the resulting master curves are compared from several different tests with different temperature sequences. Activation energies are calculated, which show that the same mechanism is acting at all stages, and creep rupture lifetime predictions are made which are longer than those hitherto made by extrapolations from short-term creep tests.