Design of Replicated Open-Pore Aluminium Cellular Materials with a Non-Stochastic Structure for Sound Absorption Applications

Several porous materials, especially natural fibres and polyurethane foams, are frequently used as sound absorbers in multiple noise reduction applications. Notwithstanding their excellent absorption performance, these materials usually lack the structural strength and fire resistance required for use in aggressive environments or situations requiring structural stability. This paper proposes the design of open-pore polymer and aluminum cellular materials with non-stochastic structures for sound absorption. These materials were fabricated using additive manufacturing (polymeric materials) and the replication method (aluminum materials), which involves infiltrating porous preforms formed by compacting spheres of a martyr material, such as NaCl, with liquid aluminum. The proposed materials can be employed as a resonator system when backed by an air cavity, with the change in cavity depth used to tune its sound absorption peak. Following the standard ASTM E1050, the sound absorption of these materials was investigated. In addition, the sound absorption performance of the materials was predicted using an Equivalent Circuit Method model. The experimental results are consistent with those predicted by the model, highlighting the potential of the microstructural and configurational design of these materials as sound absorbers.