Molecular Dynamics Simulations and Theoretical Model for Engineering Tensile Properties of Single-and Multi-Walled Carbon Nanotubes.

Keiichi Shirasu,Go Yamamoto,Fan Liu,Shunsuke Kitayama,Toshiyuki Hashida

doi:10.3390/nano11030795

Keiichi Shirasu, Go Yamamoto + Show 3 more

Open Access

https://doi.org/10.3390/nano11030795

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Abstract

To apply carbon nanotubes (CNTs) as reinforcing agents in next-generation composites, it is essential to improve their nominal strength. However, since it is difficult to completely remove the defects, the synthesis guideline for improving nominal strength is still unclear, i.e., the effective strength and the number of nanotube layers required to improve the nominal strength has been undermined. In this study, molecular dynamics simulations were used to elucidate the effects of vacancies on the mechanical properties of CNTs. Additionally, the relationships between the number of layers and effective and nominal strengths of CNTs were discussed theoretically. The presence of extensive vacancies provides a possible explanation for the low nominal strengths obtained in previous experimental measurements of CNTs. This study indicates that the nominal strength can be increased from the experimentally obtained values of 10 GPa to approximately 20 GPa by using six to nine nanotube layers, even if the increase in effective strength of each layer is small. This has advantages over double-walled CNTs, because the effective strength of such CNTs must be approximately 60 GPa to achieve a nominal strength of 20 GPa.

Highlights

The exceptional mechanical properties of carbon nanotubes (CNTs) make them highly attractive as potential reinforcing components in next-generation composites, such as in hydrogen storage tanks and space elevator cables
To enable the development of CNTs with superior mechanical properties, we have previously investigated the structural–mechanical property relationships of multi-walled carbon nanotubes (MWCNTs) based on a theoretical model of their tensile strength
We presented Molecular dynamics (MD) simulations showing the effects of pitting on the mechanical properties of single-walled CNT (SWCNT)

Summary

Introduction

The exceptional mechanical properties of carbon nanotubes (CNTs) make them highly attractive as potential reinforcing components in next-generation composites, such as in hydrogen storage tanks and space elevator cables For these applications, webs, sheets, and yarns of multi-walled carbon nanotubes (MWCNTs), which are fabricated by directly dry-drawing MWCNTs from drawable MWCNT forests, have been developed [1,2,3,4,5,6,7,8]. Xiang et al [17] used machine-learningassisted, high-throughput MD simulations to investigate the relationship between the structural parameters and mechanical properties (including the nominal strength) of CNTs with Frenkel-pair-type crosslinks In these studies [14,17], interlayer crosslinking was introduced to a defect-free MWCNT model to evaluate the CNT’s mechanical properties. Following our previous work [12], we are investigating the nanotube structure required to improve the nominal strengths of CNTs

Molecular Dynamics Models and Computational Methods

Schematic computational models with different pitting densities from

For intact

Nominal strengthand of CVD-grown and arc-discharge-grown

60 GPafor was

Conclusions