Controllable toughness enhancement in graphene hybrid materials via planar twist-angle of carbon nanotubes

A controllable toughness enhancement in graphene hybrid materials via twist-angle of CNTs was first investigated. The mechanical properties, such as out-of-plane deformation, stress–strain curves, strain energy and interlayer loading transfer of Gr Hybrid model coupled by twist-angle CNTs were investigated by molecular dynamics simulations and nonlinear fracture mechanics theory. We find that these mechanical properties are sensitive to the existence of twist-angle CNTs in the Gr hybrid model. The crosslinking sites can be considered as structural defects. In addition, the CNTs exert a strengthening influence on the out-of-plane deformation, interlayer loading transfer as well as bond strain energies, thereby deflecting the crack paths of Gr Hybrid model under axial tension. Nevertheless, the existence of CNTs also triggers a reduction in the in-plane stress and the associated strain due to sp2 + sp3 hybrid state. We find that this abnormal improvement in toughness derives from the localization of the stress fields arising from their out-of-plane displacements at the interface, resulting in the stress fields being localized only at the crosslinking sites. These interfacial toughening strategies can redistribute crack tip stress in a wider range, avoid stress concentration, and at the same time realize a lot of energy dissipation by promoting crack deflection, thus achieving overall high toughness.