Experimental and FEA evaluation of the Young´s modulus for Al2O3/Al(OH)3 reinforced aluminum foams: effect of the interfacial bonding

In this work, the compressive Young´s moduli of metallic aluminum foams reinforced with spherical ceramic particles were both experimentally determined and predicted using Finite Element Analysis (FEA). Different combinations pore/reinforcement were used, keeping 4 mm in diameter pores and 2 mm reinforcements, which were Al2O3 or Al(OH)3. Volume ratios pore/reinforcement of 4:1, 2:1, and 1:1 were selected. For validation purposes, experimental foams were manufactured through infiltration, using NaCl as space holders that generate pores upon dissolution. A wide distribution of characteristics was obtained for both experimental foams and FEA models, with porosities ranging from 35 to 51%, and reinforcement percentages from 11 to 37%. Results showed FEA estimations well aligned with experimental findings, but only after the correct selection of the bonding characteristics for the matrix-reinforcement interface, which depended on the use of Al2O3 or Al(OH)3. Such a linkage is associated with the formation of a SiO2 layer at the Al(OH)3-matrix interface, observed during the characterization of the experimental foams. This led to simulating interfacial regions with complete bonding, but only when Al(OH)3 was used as reinforcement. Contrarily, in the FEA analysis of the foams reinforced with Al2O3 these particles were simulated completely de-bonded with matrix, because of the total lack of interfacial reaction products observed for the experimental foams. Although the Young´s modulus of Al2O3 is significantly higher than for Al(OH)3, total debonding Al2O3-matrix caused a significant decrease in the mechanical properties of these foams. It was demonstrated the importance of selecting appropriate reinforcements and accurately defining boundary conditions for reliable simulation results.