Load-transfer efficiency and mechanical reliability of carbon nanotube fibers under low strain rates

For practical applications, long term performance of carbon nanotube (CNT) fibers is essential, as in these cases CNT fibers are expected to work under cyclic loading or under a certain stress/strain for a long time. In this paper, the mechanical behavior of CNT fibers, including stress relaxation, load transfer and failure process, are investigated under low strain rates which are close to practical situations. Static mechanical test, electrical measurement and Raman spectroscopy are used to in situ monitor the load transfer and failure process. Transmission electron microscopy is utilized to characterize the structures and morphologies of CNTs inside the fibers. Based on the experimental results, it is believed that there is a close relationship between CNT morphology and fiber performance. Nonuniform load bearing, straightening of wavy CNTs and serious sliding exist in the fibers and are main factors that degrade fiber’s reliability.

► The reliability of CNT fibers have been examined at very low strain rate. ► Load transfer inside CNT fibers has been in situ monitored. ► Serious stress relaxation of CNT fiber is observed. ► Nonuniform load bearing, straightening and sliding of CNTs exist. ► Structure dependence failure mechanism is deduced.