  Surface wrinkling is an instability mode that is often observed in a wide
variety of multilayer tubes under bending deformation. When the degree of
applied bending exceeds a critical value, wrinkles appear at the intrados of
the tube and release a large amount of in-plane strain energy stored by bending
deformation. In the present work, we propose a simple theoretical model for
evaluating the critical curvature and critical bending moment for the
occurrence of wrinkling in multilayer tubes and apply the model to carbon
nanotubes in a case study. Results indicate an inverse proportional
relationship between the two critical properties, which holds true regardless
of the number of layers and the size of the hollow core.
