Tensile strength of a transverse grain boundary in a single-walled carbon nanotube

Abstract

Adding carbon nanotubes (CNTs) into ceramics is an important way to promote toughness. Crystalline defects existing in materials play a significant role in affecting both their mechanical and functional performances because they bring symmetry breaking of the periodic lattice structures. For CNTs existing in real ceramic materials, which almost appear as polycrystalline forms, the most notable defects are the grain boundaries (GBs) which consist of defect cores of dislocations. It is of engineering importance to investigate the effects of these defect cores of GBs on the strength of the polycrystalline CNTs to promote the composites’ performances. The variety of grain orientations of the polycrystalline CNTs allows the GBs to have various misorientations and different arrangements of the defect cores of dislocations at the GBs, which causes disparity in the stress fields near the GBs under an external stress condition, thus making distinguishable effects on the strength. While effective rules have been established for graphene (GP) GBs to predict the tensile strengths of GP GBs with different misorientations, the effects of misorientation and curvature on the strength of CNT GBs have yet to be reported. This work studied these effects by molecular dynamics (MD) simulation. The results illustrate that the misorientation and temperature have much more significant effects than the curvature on the strength of CNT GBs, and verified a consistent tendency of the misorientation-strength relationship of the CNT GBs with the corresponding GP GBs. The CNT GBs and their corresponding GP GBs have almost identical strengths for most of the simulated results. Notable differences between CNT and GP GBs were only found at misorientations near 0 and 30° in armchair GBs. These strength differences were attributed to the crack stabilization and structural reconstruction in CNT GBs.