The impact of surface roughness on an additively manufactured acoustic material: An experimental and numerical investigation

Unlocking the industrial potential of acoustic metamaterials requires a design process which accounts for the realities of the required additive manufacture. At present, the impact of additive manufacturing tolerances and surface topologies on the acoustic behaviour of designs is not well understood. This research investigates the effects of the surface roughness arising from the layer-by-layer fabrication technique on the acoustic properties of additively manufactured parts. The process parameters of the additive manufacture can be chosen to introduce a systematic variation in the surface roughness. In this study, a benchmark acoustic material was fabricated using fused deposition modelling with four commonly used layer heights: 0.10, 0.15, 0.20 and 0.25 mm. The material samples were inspected using a confocal microscope to obtain the precise surface profiles created by the printer. The response of the overall system may be efficiently predicted from a detailed viscothermal numerical analysis of the lattice exploiting efficiencies due to the repeating structure. The experimental measurements of the surface topology as a function of layer height were used to define a numerical surface representative of the real samples. Computational models of the structure with both smooth and rough surfaces were created. The numerical and experimental data were compared as a function of additive manufacturing layer height. It was shown that the impact of the surface roughness was accurately captured in this modelling approach but that surface roughness alone is not sufficient to fully explain differences between the experimental and numerical datasets.