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

Lessons from Nature for Carbon‐Based Nanoarchitected Metamaterials

“…The material parameters obtained by MD simulation cannot be directly used in the FE analysis because the graphene nanosheets and CNT contains the thickness effect. [20,56,57] The 2D graphene nanosheets are one-atom-thick nanomaterials. In MD calculation, we assume a thickness of 0.34 nm for all samples.…”

“…In MD calculation, we assume a thickness of 0.34 nm for all samples. [20,39,41] To exclude the thickness effects from these material parameters (e.g., stiffness and ultimate strength), an effective thickness for graphene and CNT is identified based on the strain energy and deflection in a three-point bending simulation. [56,57] The effective thickness and stiffness used in FE calculation are 1.27 Å and 2.81 TPa, respectively.…”

“…[56,57] The effective thickness and stiffness used in FE calculation are 1.27 Å and 2.81 TPa, respectively. [20,57] Based on the equivalent thickness of 3.4 Å used in the MD simulation, the equivalent volume of individual carbon atoms in the pristine graphene and CNT is calculated as 8.92 Å 3 . Then the relative density of the designed graphene-and CNT-based nanostructures is calculated by ρ ¼ n=ðV 0 =8.92Þ, in which n and V 0 are the number of atoms and the volume in the designed nanostructures, respectively.…”

“…[13,14] The unique properties of graphene and CNT make them exciting candidates in flexible electronic devices, [15,16] nanosensors, [17] complementary metal-oxidesemiconductor, [11] and nanoelectromechanical systems (NEMS). [18] Nevertheless, some of CNT's and graphene's intrinsic properties, such as the limited stretchability (%0.2) [19,20] and low dimensional (1D and 2D) features, [21] can hamper their applications.By introducing rationally designed underlying architectures as the constitutive unit cell, architected materials, so-called metamaterials, with unparalleled multiphysical properties can be developed at multiple scales, from nano to macro. [22][23][24][25][26][27][28][29] For example, 3D nanoarchitected pyrolytic carbon exhibits extreme energy dissipation, which is %70% superior to that of Kevlar composites and nanoscale polystyrene films, owing to its material architecture and nanoscale material size effects.…”

Micro‐Scale Auxetic Hierarchical Mechanical Metamaterials for Shape Morphing

“…It seems that some of the first studies devoted to this topic were published by Gatt et al [45] and Cho et al [46] where the famous hierarchical rotating square system was proposed. In the following years, it was demonstrated [45][46][47][48][49] that this structure can exhibit tunable auxetic behavior where the extent of auxeticity depends on the relative rate of the deformation of hierarchical levels constituting the system. Recently, it was also reported that the design of the hierarchical square system can be modified in order to change its characteristic.…”