Mechanical behavior and micro-mechanism of carbon nanotube networks under friction

• Published in: Carbon (New York) 2022-11, Vol.200, p.108-115
• Main Authors: Hu, Tianxiong, Qian, Guian, Wu, Xianqian, Wang, Chao
• Format: Article
• Language: English
• Subjects: Carbon nanotube network; Coarse-grained molecular dynamics; Crosslink; Deformation behavior; Friction
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2022.08.042

Friction behavior of carbon nanotube networks (CNNs) is ubiquitous in applications, however, is poorly investigated. Here, we employ coarse-grained molecular dynamics (CGMD) simulations to investigate friction behaviors and microscopic mechanism of CNNs. We first give a phase diagram to determine the initial contacting state of “supported” or “trapped” for an indenter in CNNs. In a “supported” state, friction force is mainly originated from the local surface adhesion of CNNs which experience stable elastic deformation in friction process. In contrast, in a “trapped” state, friction force is mainly activated by nonlocal reconstitution of carbon nanotubes (CNTs) accompanied with irreversible bond breaking. Furthermore, with an increased normal pressure, the friction force keeps nearly constant for a “supported” indenter while it increases linearly for a “trapped” one; the friction force is linearly or nonlinearly related to the sliding velocity of an indenter in a supported or trapped state. Importantly, there is a critical crosslink density, above which, the coefficient of friction is greatly decreased due to enhanced integrity of CNNs. These results provide a profound understanding of friction deformation behavior of CNNs, which is of great significance for optimal design in practical applications. The left figure shows the contacting state of a spherical indenter on a CNN film. The red thick line divides the σ-R plane into two parts: trapped and supported; the right one shows the top view of CNN color-coded by the value of σxx after friction and the comparison of normalized dynamic friction force for the two initial contact states of the indenter. [Display omitted]