| Since the hexagonal honeycomb structure has a series of excellent features and a wide range of applications, it is necessary to conduct a comprehensive understanding. In practical applications, they are often designed as an out-of-plane and in-plane directions subjected to load. The properties of cellular materials have great relevance of sizes, especially the impact on the mechanical performance of changing the in-plane size needs to be further refined studies. Therefore, the influence of the change of the in-plane size on the mechanical parameters is the main research content in this paper. Without size influence, the effect of strain rate on deformation mode and mechanical property is also the key point of our concerns in the plane compression.In this paper, we study the influence of the size effect on the mechanical properties of the specimen by experiment and numerical simulation, and the influence of different strain rates on the deformation modes and mechanical properties:18 kinds of aluminum honeycomb block specimens, including 3 kinds of relative density and 6 kinds of in-plane dimensions, are tested by Instron material testing machine. Compression experiments, respectively from x1 and x2 direction, found that deformation mode is the same in different size and density of aluminum honeycomb test pieces, and they are all by way of layer by layer periodic superimposed until compaction. For mechanical properties, densification strain of three kinds of aluminum honeycomb specimens don’t show a significant size effect for different in-plane sizes. It is considered that densification strain is a stable mechanical parameter. Macro stiffness, both in x1 and x2 direction, is sensitive to in-plane dimension, which tends to be stable until specimen size reached N×N=9×9. For small relative density(t/D=0.016) of the specimen, platform stress increased with the increase of in-plane dimensions until specimen size reached N×N=11×11,but for densities of 0.02 and t/d=0.026, specimen platform stress is not sensitive to specimen size. Finally introducing weak boundary layer theory to explain the reason that stiffness of the specimen become more sensitive in the relative density under the condition of small size. Through theoretical derivation and experimental data to verify the reference rationality. In a word, when cellular materials are used in-plane direction compression, cellular size at least reached N×N=11×11 should be chose to get stable mechanical parameters of materials. Then using the ABAQUS finite element software, the numerical simulation of quasi-static compression is carried out from x1 and x2 direction respectively. The influence of the deformation modes, the stress and the strain of the platform on the size effect is analyzed. The result is same as experiment, which verifies the reliability of the model.By the analysis on the reliability of the model as a guarantee, using ABAQUS finite element software establish aluminum honeycomb material model of dimension for N×N=11×11, which is not affected by the size effect. The result is that in different strain rate have obvious influence on the deformation mode. When the strain rate is high, the deformation mode is changed into the impact deformation, and the inertia effect is obvious. when strain rate change from quasi static to dynamic, plateau stress showed a clear upward trend, showing a strong strain rate sensitivity. In x2 direction compression, densification strain rise to a lesser extent before strain rate reached 500. But in x1 direction compression, densification strain do not increase with strain rate. So honeycomb aluminum material is strain rate sensitive material. |
PDF Full Text Request