To understand the relationship between the collapse mechanisms and geometry parameters of sandwich plate with two aluminum alloy faces and one polyurethane foam core, samples subjected to three-point bending loads were studied through simulation, test and analytic methods. Based on published papers, the dimensionless values of limit loads for different failure modes were modified according to real test condition. The load-deformation relation from the analytical formulae was compared with that from experimental and numerical results. A mechanism map was provided to reveal the dependence of the dominant collapse mechanism upon the geometry parameters of the face and the core. The results show that the prediction accuracy was high only if the face thickness was much smaller than the core thickness.
The multi scale modeling method was utilized to study the bending characteristics of a carbon nanotube （CNT） and CNT reinforced composites. Through combining molecular dynamics and continuum mechanics, the tensional and flexural modulus of a CNT were calculated by a finite element model constructed by reticulate beams with solid cylinder shape and energy equal to C-C bonds. Then, another beam element with hollow cylinder shape and equivalent stiffness was utilized in place of a CNT in a matrix, thus, a multi scale representative volume element （RVE） model of CNT reinforced composite was established. Using this RVE model, the bending behavior of CNT based composites was analyzed. The influence of diameter D, length L, aspect ratio L/D, volume fraction, chiral of CNTs and shape of RVE as well as the arrangement of CNTs in matrix on the rein forcement effect of flexural modulus of resultant nanocomposites were further discussed. The ob tained data provide useful information for the design of CNT reinforced composites.
The excellent mechanical properties of carbon nanotubes make them potential candidates for engineering application. In this paper, the impact and failure behaviors of single-walled carbon nanotubes （SWCNTs） are investigated. The effects of diameter, length, and chirality on their energy absorption characteristics under lateral impact and axial crush are studied. By integrating the principle of molecular structural mechanics （MSM） into finite element method （FEM）, the locations and directions of fracture process can be predicted. It is shown that the specific energy absorption （SEA） of SWCNTs is 1-2 order of magnitude higher than that of the ordinary metallic materials and composites in axial impact, indicating that carbon nanotubes are promising energy absorption materials for engineering applications.
