• Manufacture graphene films suspended on 1-micron-diameter circular holes by exfoliating bulk graphite
• Mechanical tests were employed on those graphene films by indenting the circular films at the center with AFM (atomic force microscope). Experimental data were analyzed by the model of "center-point load on circular membrane". The results confirmed the excellent mechanical properties of graphene—the strongest material in the world (work published on Science July 2008)
• Build up numerical models (such as finite element simulation, molecular dynamics simulation and ab initio simulation) for further studies on graphene including mechanical properties, etc.

• Analytical solution for circular membrane under point load at the center:
Pasted Graphic 2
F = Force, σ0 = pre-stress, E =Young’s modulus, w = deflection, h = thickness, a=radius of membrane, ν=Poisson’s ratio, R=tip radius

Distribution of measured in-plane stiffness and effective Young's Modulus (taking thickness of graphene as interlayer spacing of graphite)

• Non-linear elastic behavior (the 3rd-order elastic modulus)