Study Of Cell Structure And Compressive Deformation Process Of A Closed Cell Aluminum Foam

Effect of cell structure on mechanical properties and uni-axial compressive deformation process of closed-cell aluminum foams by air injection was studied in this paper. The parameters of cell structure with varied densities were measured, the relation of cell size, density and node size were explored, and uni-axial compressive experiment was conducted to analyze the effect of density on collapse strength, Young’s modulus and crack initiation and propagation.The results through observation, analysis and study of the experimental data and images show that the cell wall thickness and node size of aluminum foams decrease with increasing cell size, and the relation of the cell diameter and density is expressed as ρ*=0.1085+4.8627exp(-0.608ψ). When foam density increase from0.12to0.28g/cm3, the collapse strength of the closed cell aluminum foams in uni-axial compression rises from0.51to1.44MPa, while Young’s modulus of these samples increases from0.65to1.51GPa. During the compressive process, the closed-cell aluminum foams experience three deformation stages as other foams, linear-elastic deformation, plastic collapse and densification process. The cell-level deformation is that the cell wall has some initial curvature after elastic deformation with increasing load, and the deformation is strongly localized to defects and the thinnest parts of the cell wall, where cracks initiate and propagate faster in higher stress. The corrugation is caused by incomparable strength in the cell wall membrane, and the cracks become unstable and rotate in their directions after running through the wall, which causes plastic collapse of the cells. The further increase in strain results in subsequent densification process.