Mechanical properties of SWNT X-Junctions through molecular dynamics simulation

The mechanical behavior of seven different carbon nanotube (CNT) X-junctions with a varying number of bonds was investigated through molecular dynamics simulations. The X-junctions are composed of two (6,0) single-walled carbon nanotubes (SWNTs) created via vibration-assisted heat welding. The junctions, containing anywhere between one and seven bonds, are subject to uniaxial tensile, shear and torsional strain, and then the stiffness values are determined for each case. When subjected to tensile and shear strain, both the arrangement and orientation of bonds are found to affect the stiffness of junctions more substantially than the number of bonds, bond length or bond order. Surprisingly, anisotropic shear behavior is observed in the X-junctions, which can be attributed to the junction's bond orientation. Also, the stiffness of X-junctions tested under an applied torque (torsion) differs from the stiffness under tensile and shear strain, however, in that it is more substantially affected by the number of bonds present in the junction than by any other property.