Mechanical properties of graphene

Our research is focused on the measurement of the mechanical and spectroscopic properties of exfoliated graphene flakes for samples either suspended or simply supported/embedded on polymeric substrates (Fig.1a).

Monolayer graphene flakes supported/embedded in polymer substrates have been studied under uniaxial tension and compression for small strains. The mechanical loading is induced by using a single cantilever frame (Fig. 1b). Using Raman spectroscopy for variant laser lines, the shift of the 2D and G bands versus strain were reported for both tension and compression experiments (Fig. 1c).

Tension reveals splitting of the 2D peak at zero strain depending on the wavelength of the excitation laser line. A master plot of G band behavior versus strain as a function of tensile modulus was developed.

Compression experiments for various rectangular geometries of monolayer graphene flakes were carried out. Utilizing the 2D peak measurements the critical strain to failure was estimated. A dependence on the flake’s geometry came out and the failure’s mode was found to be of a buckling type.

Detailed mapping measurements on uncovered/covered mono and few- layer graphene flakes for zero strain and for tension have been performed. Shear lag analysis was used with a view towards understanding the stress transfer mechanism.