Nonlinear multiscale model for interstitial structures of densely ordered multi-walled carbon nanotube bundles

The microscopic structural changes upon mechanical deformation of coiled multi-walled carbon nanotube (MWCNT) yarns were investigated through a multiscale constitutive model. All-atom molecular dynamics simulations reveal a strong dependence of the nonlinear mechanical behavior on the diameter of the nanotubes composing the MWCNT bundles. Accordingly, the multiscale modeling is configured to predict the stress and interstitial area change experienced by each nanotube according to the diameter and position distribution of the nanotubes constituting the microstructure. From the proposed multiscale method, representative volume elements (RVEs) of MWCNT bundles with micrometer scale lengths are developed. The RVEs are applied to characterize the deformation of each nanotube due to the longitudinal sway and the stress concentration in the cross-section due to local tightening. The results are in good agreement with those of the all-atom cross-sectional model corresponding to each longitudinal position, which proves the validity of the developed RVEs.