Creep and Inverse Stress Relaxation Behaviors of Carbon Nanotube Yarns
Misak, Heath Edward
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Misak, Heath Edward; Sabelkin, V.; Miller, L.; Asmatulu, Ramazan; Mall, S. 2013. Creep and Inverse Stress Relaxation Behaviors of Carbon Nanotube Yarns. Journal of Nanoscience and Nanotechnology, vol. 13:no. 12, December 2013:ppg. 8331-8339(9)
Creep, creep recovery and inverse stress relaxation behaviors of carbon nanotube yarns that consisted of 1-, 30-, and 100-yarn(s) were characterized. Primary and secondary creep stages were observed over the duration of 336 h. The primary creep stage lasted for about 4 h at an applied load equal to 75% of the ultimate tensile strength. The total strain in the primary stage was significantly larger in the carbon nanotube multi-yarn than in the carbon nanotube 1-yarn. In the secondary stage, 1-yarn also had a smaller steady state strain rate than the multi-yarn, and it was independent of number of yarns in multi-yarn. Strain response under cyclic creep loading condition was comparable to its counterpart in non-cyclic (i.e., standard) creep test except that strain response during the first cycle was slightly different from the subsequent cycles. Inverse creep (i.e., strain recovery) was observed in the 100-yarn during the cyclic creep tests after the first unloading cycle. Furthermore, inverse stress relaxation of the multi-yarns was characterized. Inverse stress relaxation was larger and for longer duration with the larger number of yarns.
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