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Boundary-dependent mechanical properties of graphene annular under in-plane circular shearing via atomistic simulations

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ABSTRACT

Graphene annulus possesses special wrinkling phenomenon with wide range of potential applications. Using molecular dynamics simulation, this study concerns the effect of boundary on the mechanical properties of circular and elliptical graphene annuli under circular shearing at inner edge. Both the wrinkle characteristic and torque capacity of annular graphene can be effectively tuned by outer boundary radius and aspect ratio. For circular annulus with fixed inner radius, the critical angle of rotation can be increased by several times without sacrificing its torque capacity by increasing outer boundary radius. The wrinkle characteristic of graphene annulus with elliptical outer boundary differs markedly with that of circular annulus. Torque capacity anomalously decreases with the increase of aspect ratio, and a coupled effect of the boundary aspect ratio and the ratio of minor axis to inner radius on wrinkling are revealed. By studying the stress distribution and wrinkle characteristics, we find the decay of torque capacity is the result of circular stress concentration around the minor axis, while the nonuniform stress distribution is anomalously caused by the change of wrinkle profiles near the major axis. The specific mechanism of out-of-plane deformation on in-plane strength provides a straightforward means to develop novel graphene-based devices.

No MeSH data available.


Coupled effect of outer boundary shape and radii ratio Ros/Ri on shear stress distribution of elliptic annular graphene.(a–c) Shear stress contours of annuli with fixed Ri = 6 nm, Ros = 8 nm and varying Rol = 8, 14, 16 nm under critical torsional angle. (d–f) Shear stress contours of annuli with fixed Ri = 3 nm, Ros = 8 nm and varying Rol = 8, 14, 16 nm under critical torsional angle.
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f3: Coupled effect of outer boundary shape and radii ratio Ros/Ri on shear stress distribution of elliptic annular graphene.(a–c) Shear stress contours of annuli with fixed Ri = 6 nm, Ros = 8 nm and varying Rol = 8, 14, 16 nm under critical torsional angle. (d–f) Shear stress contours of annuli with fixed Ri = 3 nm, Ros = 8 nm and varying Rol = 8, 14, 16 nm under critical torsional angle.

Mentions: In order to explain the mechanism for the coupled effect of boundary aspect ratio and radii ratio Ros/Ri on torque capacity, we further calculate the in-plane shear stress distribution of elliptical annulus under critical torsion angle. Figure 3 shows the comparison of shear stress contour for two groups of annuli with Ri = 6 nm and Ri = 3 nm. For circular annuli (Fig. 3a,d), the stress distribution is relatively uniform around the inner edge, regardless of the outer radius Ro. Since the failure of annuli is caused by the stress concentration around the inner edge, the torque capacity of annulus with same inner radius is close, as demonstrated by Fig. 2c (the first points of black and blue lines). With the increase of major axis Rol, the stress distribution of thick elliptical annuli with Ros = 8 nm, Ri = 3 nm (Fig. 3a–c) is almost as uniform as circular annulus, as a result, the torque capacity does not change much with Rol. For thin annuli with fixed Ros = 8 nm, Ri = 6 nm (Fig. 3d–f), the stress concentration near the short axis becomes more and more severe with Rol. As a result, the torque capacity of the elliptical structure decays with the increase of the aspect ratio. However, the increase of aspect ratio will not lead to consistent decrease of τ. By comparing Fig. 3b and c, we find that the stress concentration degree converge to a stable state after Rol is large enough, leading to the decrease of decay rate.


Boundary-dependent mechanical properties of graphene annular under in-plane circular shearing via atomistic simulations
Coupled effect of outer boundary shape and radii ratio Ros/Ri on shear stress distribution of elliptic annular graphene.(a–c) Shear stress contours of annuli with fixed Ri = 6 nm, Ros = 8 nm and varying Rol = 8, 14, 16 nm under critical torsional angle. (d–f) Shear stress contours of annuli with fixed Ri = 3 nm, Ros = 8 nm and varying Rol = 8, 14, 16 nm under critical torsional angle.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC5304194&req=5

f3: Coupled effect of outer boundary shape and radii ratio Ros/Ri on shear stress distribution of elliptic annular graphene.(a–c) Shear stress contours of annuli with fixed Ri = 6 nm, Ros = 8 nm and varying Rol = 8, 14, 16 nm under critical torsional angle. (d–f) Shear stress contours of annuli with fixed Ri = 3 nm, Ros = 8 nm and varying Rol = 8, 14, 16 nm under critical torsional angle.
Mentions: In order to explain the mechanism for the coupled effect of boundary aspect ratio and radii ratio Ros/Ri on torque capacity, we further calculate the in-plane shear stress distribution of elliptical annulus under critical torsion angle. Figure 3 shows the comparison of shear stress contour for two groups of annuli with Ri = 6 nm and Ri = 3 nm. For circular annuli (Fig. 3a,d), the stress distribution is relatively uniform around the inner edge, regardless of the outer radius Ro. Since the failure of annuli is caused by the stress concentration around the inner edge, the torque capacity of annulus with same inner radius is close, as demonstrated by Fig. 2c (the first points of black and blue lines). With the increase of major axis Rol, the stress distribution of thick elliptical annuli with Ros = 8 nm, Ri = 3 nm (Fig. 3a–c) is almost as uniform as circular annulus, as a result, the torque capacity does not change much with Rol. For thin annuli with fixed Ros = 8 nm, Ri = 6 nm (Fig. 3d–f), the stress concentration near the short axis becomes more and more severe with Rol. As a result, the torque capacity of the elliptical structure decays with the increase of the aspect ratio. However, the increase of aspect ratio will not lead to consistent decrease of τ. By comparing Fig. 3b and c, we find that the stress concentration degree converge to a stable state after Rol is large enough, leading to the decrease of decay rate.

View Article: PubMed Central - PubMed

ABSTRACT

Graphene annulus possesses special wrinkling phenomenon with wide range of potential applications. Using molecular dynamics simulation, this study concerns the effect of boundary on the mechanical properties of circular and elliptical graphene annuli under circular shearing at inner edge. Both the wrinkle characteristic and torque capacity of annular graphene can be effectively tuned by outer boundary radius and aspect ratio. For circular annulus with fixed inner radius, the critical angle of rotation can be increased by several times without sacrificing its torque capacity by increasing outer boundary radius. The wrinkle characteristic of graphene annulus with elliptical outer boundary differs markedly with that of circular annulus. Torque capacity anomalously decreases with the increase of aspect ratio, and a coupled effect of the boundary aspect ratio and the ratio of minor axis to inner radius on wrinkling are revealed. By studying the stress distribution and wrinkle characteristics, we find the decay of torque capacity is the result of circular stress concentration around the minor axis, while the nonuniform stress distribution is anomalously caused by the change of wrinkle profiles near the major axis. The specific mechanism of out-of-plane deformation on in-plane strength provides a straightforward means to develop novel graphene-based devices.

No MeSH data available.