By elongating the regular Kelvin model in one direction and keeping unchanged in the other two directions,the anisotropic model was constructed.Then,the simplified periodic structural cell was obtained according to the periodicity and symmetry of the model in the whole space.Using the half-strut element and elastic deflection theory to analyze the mechanical behavior as were adopted in the previous studies,this paper obtained the theoretical expressions for the compressive stress and strain as well as the corresponding curves in the rise and transverse directions.In addition,the theoretical results were examined by the finite element simulation.Results indicated that the theoretical analysis was very close to the finite element simulation when the strain was not too high,which confirmed the validity of theoretical analysis.At the same time,the anisotropy was shown to have a significant effect on the mechanical properties of open-cell foams.As the anisotropy ratio increased,the compressive stress was improved in the rise direction but dropped in the transverse direction under the same strain.
LU ZiXing,HUANG JiXiang&CHEN Xin School of Aeronautic Science and Engineering,Beijing University of Aeronautics and Astronautics,Beijing 100191,China
The random models of open-cell foams that can reflect the actual cell geometrical properties are constructed with the Voronoi technique. The compression process of elastic open-cell foams is simulated with the nonlinear calculation module of finite element analysis program. In order to get the general results applicable to this kind of materials, the dimensionless compressive stress is used and the stress-strain curves of foam models with different geometrical properties are obtained. Then, the influences of open-cell geometrical properties, including the shape of strut cross section, relative density and cell shape irregularity, on the compressive nonlinear mechani- cal performance are analyzed. In addition, the numerical results are compared with the predicted results of cubic staggering model. Numerical results indicate that the simulated results reflect the compressive process of foams quite well and the geometrical properties of cell have significant influences on the nonlinear mechanical behavior of foams.
