Stepped Isothermal Method for CreepRupture Studies of Aramid Fibres


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Title: Stepped Isothermal Method for CreepRupture Studies of Aramid Fibres

Author(s): K.G.N.C. Alwis and C.J. Burgoyne

Publication: Special Publication

Volume: 230


Appears on pages(s): 181-194

Keywords: accelerated testing; creep-rupture; master curve; steppedisothermal method (SIM)

Date: 10/1/2005

Aramid fibres have been used in rope construction and for prestressingtendons, but when subjected to a constant static load the fibres creep with time andmay rupture, leading to a catastrophic failure of the rope. To understand this behaviourmany life-time models have been suggested but they suffer from the lack of long termcreep rupture data to make firm conclusions on rupture times and load levels. Suchdata is expensive to obtain using conventional creep testing as it takes a long timebefore failure of a specimen. To overcome this problem, and to obtain the creep-rupture data at low stress levels within a reasonably short time scale (hours),accelerated testing methods, the Stepped Isothermal Method (SIM) and TimeTemperature Superposition (TTSP), have been investigated. In SIM testing a single yarnspecimen is tested at a specific stress level under a series of increasing temperaturesteps from which a single response curve, known as the master curve, is obtainedwhich predicts the long-term behaviour. Some manipulation of the data is required, butthe technique has many advantages over the TTSP and conventional creep testing andit can be automated to obtain the long-term creep-rupture data points relatively easily.