Hierarchical kirigami-inspired graphene and carbon nanotube metamaterials: Tunability of thermo-mechanic properties

Tuning and programming the multiphysical properties of advanced materials are of critical importance for developing the next generation of adaptable multifunctional metamaterials. This study demonstrates the tunability of thermo-mechanical properties of graphene sheets and carbon nanotubes by inspiring from hierarchical kirigami mechanical metamaterials. The theoretical investigation, multiscale simulation, and experimentation show that the thermo-mechanical properties of nano-architected kirigami metamaterials can be tuned by altering geometrical parameters and introducing the hierarchical cutting patterns. Additionally, the thermal conductivity of kirigami-inspired graphene and carbon nanotube metamaterials can be regulated by an external mechanical tension. We develop closed-form formulations for predicting the mechanical behavior of kirigami graphene sheets and carbon nanotubes. Molecular dynamics and finite element simulations are conducted to evaluate theoretical predictions. By analyzing and comparing the results from atomistic and continuum-based simulations, the effect of length scale on the thermo-mechanical properties is explored. We realize that the stress-strain response, thermal conductivity, and buckling-induced 3D patterns of nano-architected graphenes can be programmed by utilizing kirigami building blocks, nano-architectural hierarchy, and heterogeneous material design. (c) 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).