Curvature-controlled wrinkling of double-walled carbon nanotubes under internal pressure

The mechanical instability of double-walled carbon nanotubes (DWCNTs) under internal pressure is systematically investigated using classical molecular dynamics simulations. Particular attention is focused on the curvature-dependent wrinkling of the outer wall. We find that small-radius DWCNTs undergo stable, nearly axisymmetric expansion sustained by strong interlayer force differences. In contrast, when the outer radius exceeds a critical value of approximately 29 nm, reduced curvature induces early wrinkling on the outer wall at small deformations, accompanied by localized energy concentrations and periodic patterns. This work reveals a distinct transition from uniform radial expansion to localized instability that is primarily governed by nanotube curvature. Different from most previous studies on axial compression or bending, the present results highlight the unique response of DWCNTs under internal pressure, a loading condition of direct relevance to high-pressure hydrogen storage and nanofluidic devices. These findings offer atomic-scale insights into size-dependent wrinkling mechanisms and provide practical guidance for the structural design and stability assessment of large-radius carbon nanotubes.