Manufacturing and analysis of functionally graded perlite-aluminium syntactic foam

The graded structure of porous materials has attracted increasing research attention recently. Their tailored structure allows mechanical properties to be controlled throughout their deformation. In fact, the properties change selectively along one direction of a functionally graded material. The gradient in porous metals is also beneficial for some engineering applications, such as biomedical implants and energy absorbers in construction and automotive industries. Metal syntactic foams (MSFs) are considered a promising energy absorber material. Creating any gradient in the structure of MSFs permits controlling their energy absorption capability at different deformation stages. Therefore, it is essential to explore functionally graded metal syntactic foams (FG-MSFs), a novel material, to broaden the knowledge about the metallic foams field and their graded structures. The current study focuses on FG-MSFs to explore their processing as well as to investigate their physical and mechanical properties. For this purpose, various approaches, including the spatial arrangements of different filler particles, the partial pre-compaction of particles and the integration of the foam with a metal tube are considered to create a gradient in either the longitudinal or the radial directions of MSFs through the counter-gravity infiltration casting technique. Then, the mechanical properties of the FG-MSFs are determined according to ISO 13314. The deformation mechanisms of these samples are investigated through light photography and IR-thermal imaging under quasi-static and dynamic loadings, respectively. In addition, the cycling loading of the FG-MSFs is examined to determine their fatigue behaviour. The mechanical properties of uniform MSFs are also investigated and compared with those of FG-MSFs to identify differences between them. This study also characterises the physical properties of the manufactured FG-MSFs to determine the fraction of the matrix, particles and voids in their structures. Their physical properties provide a vision for comparing FG-MSFs with other engineering materials.