Effects of stone–wales defects of carbon nanotubes on the elastic properties of the carbon nanotube-polyethylene nanocomposite and its interface

Abstract

Carbon nanotube (CNT) filling in a polymer is an advanced approach to improve and manage the mechanical behaviors of polymer-matrix nanocomposites. However, some structural defects exist in CNTs, e.g., Stone–Wales (SW) defects on single-walled carbon nanotubes (SWCNT), which reduces the strength and changes the mechanical properties of CNT-reinforced nanocomposites. The influences of CNTs’ SW defects on the Young’ modulus of the CNT-polyethylene (PE) composite and its interface were investigated. All studies were performed through molecular dynamics (MD) simulations with the consistent force field (PCFF) on the platform of a large-scale atomic/molecular massively parallel simulator (LAMMPS). In the MD model of the CNT-PE nanocomposite, CNTs contained SW defects. The elastic modulus of the nanocomposite was obtained from its stress-strain relation, and that of the CNT-PE interface varied with strain according to the interfacial interaction energy. The correctness and rationality of the work were verified by comparing the results from references, experiments, and the rule of mixtures (ROM). The results showed that SW defects of CNTs reduced the mechanical strength no matter for the interface and integral nanocomposite. Specifically, with increased SW defect concentration (defined as the ratio of atoms in the SW defect region to total atoms of a CNT), the interfacial strength significantly weakened, and the elastic modulus of the integral nanocomposite reduced on the macro level. These results are beneficial to understanding the mechanical properties of CNT-PE composites and the design of related products.

Keywords

• CNT-polyethylene nanocomposite
• stone-wales defects
• interface
• elastic modulus
• molecular dynamics modeling