Fatigue in assemblies of indefatigable carbon nanotubes
N Gupta and ES Penev and BI Yakobson, SCIENCE ADVANCES, 7, eabj6996 (2021).
Despite being one of the most consequential processes in the utilization of structural materials, fatigue at the nano- and mesoscale has been marginally explored or understood even for the most promising nanocarbon forms-nanotubes and graphene. By combining atomistic models with kinetic Monte Carlo simulations, we show that a pristine carbon nanotube under ambient working conditions is essentially indefatigable-accumulating no structural memory of prior load; over time, it probabilistically breaks, abruptly. In contrast, by using coarse-grained modeling, we demonstrate that any practical assemblies of nanotubes, e.g., bundles and fibers, display a clear gradual strength degradation in cyclic tensile loading due to recurrence and ratchet-up of slip at the tube-tube interfaces, not occurring under static load even of equal amplitude.
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