Mechanics of granular distribution of aligned carbon nanotube bundles

The diameter of an aligned multiwalled carbon nanotube (MWCNT) is critical to creating electric double-layer capacitance in yarn twists. Despite the various fabrication geometries of MWCNT yarns, the formation mechanism of the radial diameter gradient within the yarns remains unknown. In this study, we investigated the mechanical behavior of aligned MWCNTs when they pass through each other using all-atom molecular dynamics simulations. Nonlinear attraction and repulsion occur during passage owing to the contact between the MWCNT surfaces and radial collapse. In silico quantification of adhesion and strain energies revealed that the larger the difference in diameter between MWCNTs, the easier it is for them to pass through each other. The dynamics demonstrated a granular distribution in the MWCNT bundle. Under twisting pressure, the small- and large-diameter MWCNTs were penetrated and sieved into the yarn core and sheath, respectively.