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 for composite materials, high-strength conductors and multifunctional textiles. However, despite advances in manufacturing, the strength of CNT fiber 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 threedimensional morphology and the full tensile behavior of CNT yarns. By incorporating loadinduced 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.

Collapsed carbon nanotubes: From nano to mesoscale via density functional theory-based tight-binding objective molecular modeling

“…Owing to recent advances in characterization and capturing the dynamical friction [35] and inter-tube shear between CNTs represented at the ultra CG level [16,17], the derived mDEM models will be useful for simulating the mechanics of material systems comprising collapsed CNTs obtained by sheet stretching [2]. Recent modeling [36] revealed that bending rigidity of CNTs impacts, among other factors, the strength of CNT yarn, with the more flexible CNTs making stronger yarns. As our DFTB calculations showed, collapsed CNTs present extraordinary flexibility, comparable to that of few-layer graphene.…”

In Situ Mechanochemical Modulation of Carbon Nanotube Forest Growth

“…We therefore compare the per-CNT forces shown to influence growth with the strengths of CNT–CNT contacts within the forest. The contact strength between any pair of CNTs within the forest is determined by the local contact area that results from a balance between elastic deformation and vdW adhesion, which is determined by the diameter, wall number, and shape of each CNT . Using a three-dimensional model of the wavy morphology of the CNT forest and analytical calculation of the strength of each contact, we derive the distribution of contact strengths (Figure a) for CNT forests with alignments spanning the range in the force-modulated growth series.…”

“…The contact strength between any pair of CNTs within the forest is determined by the local contact area that results from a balance between elastic deformation and vdW adhesion, which is determined by the diameter, wall number, and shape of each CNT. 35 Using a three-dimensional model of the wavy morphology of the CNT forest and analytical calculation of the strength of each contact, 35 we derive the distribution of contact strengths (Figure 7a) for CNT forests with alignments spanning the range in the force-modulated growth series. We find that the contact strength distribution shifts upward with greater vertical alignment of CNTs, because the alignment induces a greater contact area between CNTs.…”

“…Compression simulations were performed on an array 100 nm tall of 5 × 5 CNTs by inputting the CNT geometry and contact information into ANSYS finite element simulation software, which performed compressive displacements from the top of the array in 0.2 nm increments. This model is an adaption of a model we developed to simulate CNT yarns, and further details can be found in ref 35.…”

Tough Nano‐Architectured Conductive Textile Made by Capillary Splicing of Carbon Nanotubes

“…In this communication, by fabricating and studying CNT sheets with deterministic geometry, we were able to apply fracture mechanics principles to explain for the first time the toughening mechanisms of CNT sheets . As a final note, we can demonstrate, how these values can be compared to the mechanical behavior of CNT yarns . For example, CNT yarns are known to dissipate energy in the range of 100 J g −1 for gauge length of 20 mm and 30 μm diameter, and their weight density is in the range of 1 000 kg m −3 .…”