Use of the fractal dimension for porosity modification in aluminum foams manufactured using space holder particles

Christian C. Reyes, Luis Béjar, Luis Pérez, Claudio Aguilar, Juan C. Carranza, Luis E. Carranza, Ismeli Alfonso

The effect of space holder particles (SHP) fractal distribution on the porosity of aluminum foams manufactured by infiltration is studied in the present work. Physical models were used to estimate aluminum foam porosity, simulating SHP distribution for bimodal mixtures with different particle sizes and relative quantities. Results of these models were compared with mathematical models and the results obtained for experimental aluminum foams manufactured using a 332 Al-alloy base material and NaCl grains as SHP. Experimental foam structural characterization was carried out using image analysis to obtain porosity, density, wall thickness and fractal dimension, while mechanical characterization focused on the compressive Young modulus. Results show that it was possible to manufacture foams with different fractal porosities and a wide variety of unit cells, reaching a maximum of $\sim\SI{68}{\percent}$. It was also found that pore wall thicknesses significantly decreased with the increase in the fine particles fraction. Besides, all the models presented a peak with a maximum porosity, whose values increased and shifted to low fine particles fraction with the increase in the sizes ratio. This behavior was also observed for the experimental foams with low particle size ratio. Nevertheless, for higher size ratios porosity showed an irregular behavior attributed to the mixing process.