Molecular dynamics simulations of the failure behaviors of closed carbon nanotubes fully filled with C60 fullerenes

Various failure behaviors of closed single-walled carbon nanotubes fully filled with C60 fullerenes under compressive, tensile, torsional, and combined tensile-torsional loads are examined using classical molecular dynamics simulations. In particular, the details of multiple failure modes in combined tension-torsion are investigated, and then multiple failure envelopes are identified as failure criteria. In the cases of uniaxial loading, filling the nanotubes with C60 fullerenes importantly increases their compressive and torsional buckling loads (not tensile failure loads), and the rate of increase is much higher in torsional loading. The observations under combined tensile-torsional loading reveal that while the tensile failure load decreases with combined torsion, the torsional buckling load increases with combined tension. As the result, the failure envelopes under this type of combined loading are definitely different relative to what is predicted under uniaxial tension or torsion, and exhibit the feature of multiple failure envelopes that consist of both tensile and torsional failure envelopes.