Compressive properties of syntactic aluminium foams using expanded silica gel

Abstract

A vacuum casting method was used for the syntactic foam production. A mixed cell structure (containing both open and closed cells) and spherical cell morphology were obtained. The lowest achieved relative density measured was 0.26 for an aluminum matrix sample. The specimens showed typical foam behavior during the compression test. 12.3 and 29.2 MPa maximum plateau stress were measured for aluminum and Al-12Si alloy, respectively. Largest densification strain of 40% was measured. Under constant process parameters, the density of the metal foam depends largely on the initial bead density, which is in turn strongly dependent on the expansion process. Because of the fast reduction reaction of SiO₂ by aluminum, the bead properties (outer shell thickness) should be controlled during the expansion process. The proposed production route has the potential to address the many problematic features of metal foam production, such as unpredictable foam properties and cell structure, as well as to eliminate the need for complex and costly production processes. The novel metallic foam cells produced had the potential to allow for new designs in heat sink, storage and regeneration applications.