Nanobending tests are widely used in the mechanical characterization of nanomaterials. However, nanomechanics analysis with considerations for surface energy, surface stress and adhesion between a probe-tip and a tested nanomaterial has not been systematically studied. This PhD research aims at analysing the nanomechanics of nanobending and the mechanism of measured size-dependent Young’s modulus. The nanomechanics analysis is based on energy-based surface elastic model, which theoretically treats a nanowire as composed of hypothetical bulk-phase, two-dimensional surface-phase, and one-dimensional edge phase. The governing equation of Euler beam bending is revised within the nanomechanics analysis. The nonlinear load-deflection relation is derived for nanobridge bending, in which both t...[ Read more ]

Nanobending tests are widely used in the mechanical characterization of nanomaterials. However, nanomechanics analysis with considerations for surface energy, surface stress and adhesion between a probe-tip and a tested nanomaterial has not been systematically studied. This PhD research aims at analysing the nanomechanics of nanobending and the mechanism of measured size-dependent Young’s modulus. The nanomechanics analysis is based on energy-based surface elastic model, which theoretically treats a nanowire as composed of hypothetical bulk-phase, two-dimensional surface-phase, and one-dimensional edge phase. The governing equation of Euler beam bending is revised within the nanomechanics analysis. The nonlinear load-deflection relation is derived for nanobridge bending, in which both tensile deformation and bending deformation occur. Molecular dynamic simulations of four-point bending and nanobridge bending are conducted and analysed by the developed continuum model. The surface and edge stiffness determined from the bending simulations are all consistent with those from tensile/compressive simulations, which indicates that they are material properties independent of the loading mode. The surface and edge stiffness are intrinsic factors to Young’s modulus. The second work here is to analyze the nanobridge bending experiment with consideration of the adhesive contact deformation occurring between the probe-tip and the tested nanobeam and deformation of substrate or template that supports the tested nanobeam. Analytical load-displacement relation is presented for small deflection. Adhesive contact deformation is modelled by a spring connecting the tip and the nanobeam and analyzed based on the Johnson-Kendall-Roberts theory. This analytic solution is comparable to finite element analysis. Substrate deformation is modelled by two coupled springs at the ends. Substrate compliance and adhesion contact compliance are presented as generalized expressions. Adhesive contact deformation and substrate deformation are extrinsic factors, leading to size-dependent apparent Young’s modulus of tested nanobeams.