Influence of surface stress on elastic constants of nanohoneycombs

• The regular hexagonal honeycomb is not isotropic but orthotropic.
• The competition between the surface residual stress and the surface elasticity exists.
• The surface residual stress dominates the surface effect when the cell-wall thickness t<15 nm while the surface elasticity does when t>15 nm.

Surface effect on the four independent elastic constants of nanohoneycombs is investigated in this paper. The axial deformation of the horizontal cell wall is included, comparing to the Gibson's method, and the contributions of the two components of surface stress (i.e. surface residual stress and surface elasticity) are discussed. The result shows that the regular hexagonal honeycomb is not isotropic but orthotropic. An increase in the cell-wall thickness t leads to an increase in the discrepancy of the Young's moduli in both directions. Furthermore, the surface residual stress dominates the surface effect on the elastic constants when t<15 nm (or the relative density <0.17), which is in contrast to that the surface elasticity does when t>15 nm (or the relative density >0.17) for metal Al. The present structure and theory may be useful in the design of future nanodevices.

Summary: Comparision of shear modulus predicted by different considerations, i.e., without surface effect, only surface elasticity, both surface elasticity and surface residual stress.Figure optionsDownload as PowerPoint slide