@article{f4c53e0154fc438297b56b09c1e484d3,
title = "Morphology-dependent load transfer governs the strength and failure mechanism of carbon nanotube yarns",
abstract = "The outstanding properties of individual carbon nanotubes (CNTs) have motivated interest in CNT fibers and yarns for composite materials, high-strength conductors and multifunctional textiles. However, despite advances in manufacturing, the strength of CNT yarns remains 10–100 fold less than individual CNTs. In light of the complex, multi-scale load transfer in CNT yarns, a hierarchical model taking into consideration the morphology-dependent mechanics is necessary to understand this limitation. We present a coupled analytical and finite element model of three-dimensional morphology and the full tensile behavior of CNT yarns. By incorporating load-induced changes in morphology, simulations of yarns in tension show different load paths such as fracture-type or stick–slip failure depending on the waviness and number density of CNTs. The strength of untwisted pristine CNT yarns is shown to be limited to <10% of the intrinsic CNT strength, even at practical limits to CNT packing density and alignment. Load-induced changes in CNT morphology are verified by tensile testing of CNT yarns along with in-situ X-ray scattering. In addition, the nominal structure of the yarn is shown to strongly influence the improvement in strength achieved by densified and/or cross-linking, and a sublinear relationship between CNT contact enhancement and yarn strength is predicted. Thus, this work provides a means to investigate the complex load transfer mechanisms in CNT yarns and other assemblies, to further study their process–structure–property relationships, and to understand potential property limits.",
keywords = "Carbon nanotube, Fiber, Mechanics, Strength, Yarn",
author = "Abhinav Rao and Sameh Tawfick and Mostafa Bedewy and Hart, {A. John}",
note = "Funding Information: Primary financial support was provided by the Office of Naval Research (Young Investigator Program, Award N 000141210815). A.R. was also supported in part by a University of Michigan Mechanical Engineering Department Fellowship and by the MIT Department of Mechanical Engineering via the Betty and Ira Dyer Fund and the Karl H Otte Memorial Fund. Electron microscopy was performed at the Electron Micro Analysis Lab (EMAL) at the University of Michigan. X-ray scattering was performed at the G1 beamline at the Cornell High-Energy Synchrotron Source (CHESS), which is supported by the NSF and the National Institutes of Health under Grant No. DMR-0225180. We thank Prof. Ray Baughman (University of Texas at Dallas) for providing yarn samples, and Jinjing Li (University of Michigan) and Dr. Arthur Woll (Cornell University) for assistance with SAXS experiments. Funding Information: Primary financial support was provided by the Office of Naval Research (Young Investigator Program, Award N 000141210815 ). A.R. was also supported in part by a University of Michigan Mechanical Engineering Department Fellowship and by the MIT Department of Mechanical Engineering via the Betty and Ira Dyer Fund and the Karl H Otte Memorial Fund . Electron microscopy was performed at the Electron Micro Analysis Lab (EMAL) at the University of Michigan. X-ray scattering was performed at the G1 beamline at the Cornell High-Energy Synchrotron Source (CHESS), which is supported by the NSF and the National Institutes of Health under Grant No. DMR-0225180 . We thank Prof. Ray Baughman (University of Texas at Dallas) for providing yarn samples, and Jinjing Li (University of Michigan) and Dr. Arthur Woll (Cornell University) for assistance with SAXS experiments. Publisher Copyright: {\textcopyright} 2016 Elsevier Ltd",
year = "2016",
month = dec,
day = "1",
doi = "10.1016/j.eml.2016.05.003",
language = "English (US)",
volume = "9",
pages = "55--65",
journal = "Extreme Mechanics Letters",
issn = "2352-4316",
publisher = "Elsevier Limited",
}