2009 JAN 5 - (VerticalNews.com) -- According to a study from the United States, "Graphite at the nanoscale is modeled as a material system consisting of a stack of parallel plates buffered by an elastic material. While the plates represent individual graphene sheets, the buffer material models the Van der Waals interaction between the graphene sheets."

  "As such, the loading on graphite at the nanoscale is characterized by the membrane force, the bending moment, and the shear force in the graphene sheets. Cylindrical nanoindentation of graphite is analyzed by applying a special boundary element method that employs Green's function for multilayers with platelike interfaces. Because Green's function satisfies the traction-free surface, the interfacial displacement continuity and the interfacial traction discontinuity conditions, only the indentation surface area where the boundary condition is altered, are numerically discretized. Numerical results of cylindrical nanoindentation are presented. It is shown that the bending moment and the shear force in the graphene sheets are concentrated around the edge of contact, consistent with the singularities existing in the second and the third derivatives of the surface displacement in the reduced case of a semi-infinite homogeneous solid under cylindrical contact," wrote B. Yang and colleagues ...read more

  2008 DEC 15 - (VerticalNews.com) -- "A finite-deformation shell theory for carbon nanotubes (CNTs) is established directly from the interatomic potential for carbon to account for the effect of bending and curvature," researchers in the United States report.

  "Its constitutive relation accounts for the nonlinear multibody atomistic interactions and therefore can model the important effect of CNT chirality and radius. The equilibrium equations and boundary conditions are obtained for the symmetric stresses and bending moments, which are different from many existing shell theories that involve asymmetric stress and bending moments," wrote J. Wu and colleagues, Northwestern University ...read more

  2008 DEC 15 - (VerticalNews.com) -- According to a study from the United States, "Based on the finite-deformation shell theory for carbon nanotubes established front the interatomic potential in Part I of this paper, we have studied the instability of carbon nanotubes subjected to different loadings (tension, compression, internal and external pressures, and torsion)."

  "Similar to the conventional shells, carbon nanotubes may undergo bifurcation under compression/torsion/external pressure. Our analysis, however, shows that carbon nanotubes may also undergo bifurcation in tension and internal pressure, though the bifurcation modes for tension and compression are very different, and so are the modes for the internal and external pressures," wrote J. Wu and colleagues, Northwestern University ...read more