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Uniaxial Compressive Mechanical Properties of Three-Dimensional Graphene: Theoretical Models and Molecular Dynamics Simulations

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1 School of Mechanical Engineering, Tianjin University, No. 92 Weijin Road, Nankai District, Tianjin, 300072, China

* Corresponding Author: Jiangang Guo. Email:

The International Conference on Computational & Experimental Engineering and Sciences 2023, 27(1), 1-2. https://doi.org/10.32604/icces.2023.09484

Abstract

As the first two-dimensional (2D) material discovered in experiments, graphene has attracted increasing attention from the scientific community [1]. And it possesses many superb mechanical, electronic and optical properties [2-4] due to its unique atomic structure. Its Young’s modulus and failure strength are 1TPa and 130GPa [5], respectively. Thus, 2D graphene has been extensively used in nanosensors and nanocomposites [6-8], etc. In order to fabricate graphene-based devices which inherit outstanding properties of 2D graphene, materials scientists are trying to use 2D graphene as building blocks to construct three-dimensional (3D) carbon nanomaterials, such as 3D graphene networks [9-11]. Nowadays, these 3D carbon nanomaterials have become potential candidates which can be integrated into molecular sieves, supercapacitors and energy absorbing devices [12-14], etc. Therefore, it is important to investigate compressive mechanical properties and deformation mechanisms of 3D carbon nanomaterials.
Combining molecular dynamics (MD) simulations and continuum modeling, the uniaxial in-plane compressive properties and deformation mechanisms of honeycomb three-dimensional graphene, trianglelike 3D graphene and non-equilateral hexagon 3D graphene are investigated to elucidate configurationproperty relationships, and the constitutive relations of three kinds of 3D graphene are derived to evaluate the compressive mechanical properties. Based on theoretical and MD simulation results, it is found that the compressive stress-strain responses of three types of 3D graphene can be divided into five stages. They are the linear elastic stage I, the stress plateau stage II, the van der Waals (vdW) hardening stage III, the initial crushing stage IV and the densification stage V, respectively. The compressive mechanical properties and deformation mechanisms of each stage are different.
In the linear elastic stage I, the stress increases linearly with increasing strain. Graphene sidewalls of 3D graphene undergo compressive deformation, bending deformation and rotation. In the stress plateau stage II, the plateau stress of 3D graphene is almost a constant with increasing the compressive strain. Graphene sidewalls undergo buckling deformation and rotation. In the vdW hardening stage III, the compressive stress gradually increases with the increase of strain. The distance between graphene sidewalls gradually decreases with the increase of compressive strain. And vdW repulsive interaction strength between two sidewalls gradually increases. In the initial crushing stage IV, as increasing the compressive strain, the stress increases exponentially. And the crushing region of graphene sidewalls gradually extends to the whole 3D graphene structure. In the densification stage V, the stress increases sharply with the increase of compressive strain. And 3D graphene is completely compacted.
Through analyzing energy absorption mechanisms and compression-unloading stress-strain curves for three types of 3D graphene, it is found that there are extraordinary compression-recovery properties and energy absorption capacities in 3D graphene. Besides, the Young's modulus, plateau stress and locking strain of 3D graphene gradually decrease with increasing graphene sidewall width.

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Keywords

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