Technology update
Jan 20, 2009
Graphene model suggests auxetic structure
Researchers at the Universities of Bristol, Swansea and British Columbia have developed a new model to predict the mechanical properties of single layer graphene sheets (SLGS) based on an equivalent atomistic-structural approach. SLGS are currently proposed as cornerstones for future innovative transistor generations, nanocomposites, mass sensors and resonators, and designers of nano-devices increasingly need closed expressions of the various material properties for fast prototyping of the nano-components.
The new mechanical model developed by the team is based on the equivalence between the chemical potentials and the mechanical strain energies of the C–C bonds considered as structural beams with bending, axial and shear deformation mechanisms. The approach allows the group to identify not only the equivalent mechanical properties of the C–C bonds, but also their thickness and bond length, as well as providing closed-form solutions for the in-plane mechanical properties of the graphene sheets.
The model shows good agreement with the experimental results available from open literature. Moreover, the model shows that the shear behaviour of the graphene sheets can be explained mechanically when the C–C bonds deform as an auxetic (Negative Poisson's ratio) component. Auxetic structures expand when pulled along one direction, having a counterintuitive deformation behaviour compared with classical structures and materials. The strong auxetic behaviour of the bonds is present for all of the force models considered, and provides an overall shear stiffness for the graphene sheet in good agreement with results from other work performed using molecular dynamics methods.
The researchers presented their work in Nanotechnology.
About the author
Fabrizio Scarpa (PhD) is a reader in Smart Structures at the Department of Aerospace Engineering of the University of Bristol, UK. Dr Scarpa works on auxetic materials and structures development, smart materials and multiphysics and nanostructures modelling. Sondipon Adhikari (PhD) is a professor at the Department of Civil and Computational Engineering of Swansea University, UK. Professor Adhikari works in structural dynamics, nanostructures modelling, probabilistic and random matrix theory. Anasavarapu Srikantha Phani (PhD) is an assistant professor at the Department of Mechanical Engineering at the University of British Columbia, Vancouver, Canada. Dr Phani works in the field of structural dynamics, computational mechanics, MEMS and thin films.
