Papers by Author: Zao Yang Guo

Abstract: Carbon nanotube has attracted tremendous scientific and industrial interests due to its exceptional mechanical, electrical and thermal properties. In this paper, classic molecular dynamic simulations are carried out to investigate the buckling behaviors and mechanical properties of single-walled carbon nanotubes under axial compression, both for perfect and imperfect ones introducing atomic vacancies. The effect of chirality, diameter, quantity and position of vacancy are systematically studied. The simulation results reveal that their mechanical properties such as Young’s modulus, critical strain and stress suffering a significant decline as the increasing numbers of vacancies. It is also found that the critical stress and strain are sensitive to position of atomic vacancy. Carbon nanotubes with vacancies located at the center have lower critical strain and are easier to reach the failure stage than those with vacancies at both sides.

Abstract: This paper describes uniaxial compression tests on a melt-extruded closed-cell Low-Density Polyethylene (LDPE) foam. The stress-strain response shows the mechanical behaviour of the foam is predominantly transversely isotropic viscoelastic and compressible. Images analysis is used to estimate the Poisson’s ratio under large strains. When the deformation is less than 5 percent, the kinematics and mechanical response of the polymer foam can be well-described by a linear compressible transversely isotropic elastic model. For large strain, a method of manipulating experimental data obtained from testing in the principal and transverse directions (stress vs strain and Poisson’s ratio) in order to estimate the uniaxial compression response of the foam at any arbitrary orientation is proposed. An isotropic compressible hyperfoam model is then used to implement this behaviour in a finite element code.