Compression Behavior of Single-Layer Graphenes

Abstract

Central to most applications involving monolayer graphenes is its mechanical response under various stress states. To date most of the work reported is of theoretical nature and refers to tension and compression loading of model graphenes. Most of the experimental work is indeed limited to the bending of single flakes in air and the stretching of flakes up to typically approximately 1% using plastic substrates. Recently we have shown that by employing a cantilever beam we can subject single graphenes to various degrees of axial compression. Here we extend this work much further by measuring in detail both stress uptake and compression buckling strain in single flakes of different geometries. In all cases the mechanical response is monitored by simultaneous Raman measurements through the shift of either the G or 2D phonons of graphene. Despite the infinitely small thickness of the monolayers, the results show that graphenes embedded in plastic beams exhibit remarkable compression buckling strains. For large length (l)-to-width (w) ratios (> or =0.2) the buckling strain is of the order of -0.5% to -0.6%. However, for l/w < 0.2 no failure is observed for strains even higher than -1%. Calculations based on classical Euler analysis show that the buckling strain enhancement provided by the polymer lateral support is more than 6 orders of magnitude compared to that of suspended graphene in air.

Raman spectra of bilayer graphene covered with Poly(methyl methacrylate) thin film

“…Both the G and 2D peaks stiffen and broaden because of the residual compression strain induced by the high-temperature baking during device fabrication. These results are similar to those of a previously described monolayer graphene 30 and are consistent with theoretical predictions. 31 The Raman spectra of PMMA-covered graphene obtained using different laser powers are shown in Fig.…”

Structure and dynamics of poly(methyl methacrylate)/graphene systems through atomistic molecular dynamics simulations

“…The importance of this material is based on its exceptional physical properties ) with emphasis to electronic properties (Catro-Neto et al 2009), like its electron transport capacity and electrical conductivity. Moreover, the mechanical properties of graphene, such as the high intrinsic tensile strength and stiffness, are also of particular interest (Zhao et al 2002;Tsoukleri et al 2009;Frank et al 2010). In addition, graphene exhibits high thermal conductivity, a very high specific surface area and is stable in air and transparent.…”

Transparent, flexible, and solid-state supercapacitors based on graphene electrodes

“…In another study, the buckling strains for graphene supported on substrates are 0.5%-0.6%. 27 In this study, the Raman shift of the 2D band was chosen to investigate the mechanical response to compressive strain in the graphene electrodes. The position of the 2D band as a function of the compressive strain is shown in Fig.…”

“…On the other hand, a tensile strain of 0.86% does not cause fracture and instability in the graphene electrodes. 27 Therefore, at bending angles (2θ ) larger than 40 • (strains > 0.86%), ripples are generated on the graphene electrodes in compression due to the weak van der Waals forces between the graphene and the PET substrate. 26 The ripples cause the increase in the thickness (d) of the electric double layer.…”