Microstructure-based experimental and numerical investigations on the sound absorption property of open-cell metallic foams manufactured by a template replication technique

- Open-cell IN625 foams with variable porosity and pore size were produced by a newly developed template replication method.
- There was a linear correlation between the average pore size of the polymeric templates and the produced IN625 foams.
- It indicates the advantage of microstructure controllability of the template replication method.
- Sound absorption coefficient of IN625 foams was predicted using measureable microstructure parameters via FP and DB models.
- IN625 foam with α > 0.9 at f > 1500 Hz of 50 mm thickness has been successfully fabricated and accurately predicted.

The current study investigates the acoustic absorption property of nickel-based superalloy open-cell foams manufactured by a newly developed template replication process. Inconel 625 open cell foams with controllable porosities (92%-98%) and cell sizes (300 μm-900 μm) have been successfully produced and tested for their sound absorption performance. It is evident that foam samples with the smallest cell size among them exhibit the best acoustic absorption performance, with sound absorption coefficient > 0.9 at frequencies > 1500 Hz for 50 mm thick sample. In the numerical simulation, the classical Delany­Bazley model is employed to predict the acoustic absorption property across a broad frequency range, and it requires knowledge of foam's static air flow resistivity, which, as proposed in this work, can be analytically expressed as a function of foam's microstructure parameters. A good agreement between such microstructure-based numerical model and experimental results was obtained. The proposed model can be utilized as a material design tool to guide the production of foam with optimal microstructure for sound absorption through the controllable template replication process.

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