Theoretical study of soft-to-hard transition of copper-filled carbon nanotubes

Copper-filled carbon nanotubes (Cu@CNTs) have been extensively reported to possess remarkable axial mechanical properties, but little is known about their radial mechanical properties. In this study, we perform the molecular dynamics (MD) simulations to systematically investigate the radial compression of Cu@CNTs. The results indicate that Cu@CNTs possess very high radial strength. The force–strain curves show several soft-to-hard transitions during the compression. The radial strengths of the empty CNTs and copper-filled double-walled carbon nanotubes (Cu@DWCNTs) have been calculated for comparison. Effects of tube length, diameter, chirality, and the number of Cu atoms on the radial mechanical properties are also discussed. This study may provide motivation to explore new applications of metal-filled CNTs.

• We investigated the radial mechanical properties of Cu@CNTs.
• The Cu@CNTs display several soft-to-hard transitions during the compression.
• These properties are quite different from those of the empty CNTs.
• These properties are quite different from those at the axial direction.