Acoustic Absorption in 3D-Printed PLA Biocomposite Models: Influence of Grid, Trihexagonal, and Gyroid Infills and Biomass Reinforcement

High Resolution Image Download MS PowerPoint Slide The demand for sustainable and high-performance acoustic materials is rapidly increasing as industries seek eco-friendly solutions for noise control and circular material design. Conventional manufacturing methods often limit the ability to optimize internal structures for sound absorption, whereas 3D printing offers unprecedented freedom to design and fabricate complex geometries with precision. In this study, cylindrical absorbers were produced by additive manufacturing using polylactic acid (PLA) and PLA biocomposites reinforced with biomass residues. Different infill architectures with relative densities of 10, 20, and 30% were systematically investigated to assess the combined effect of geometry, porosity, and biofiller reinforcement on acoustic performance. Normal incidence and quasi-random incidence sound absorption coefficients were evaluated using the Microflown In-situ Impedance Gun 630–20,000 Hz, and the Johnson–Champoux–Allard (JCA) model was used to extract key microstructural parameters and validate predictive accuracy. The results show that gyroid infill structures significantly enhance sound absorption, with coefficients increasing up to approximately 0.9 at high frequencies for the 30% infill PLA samples. Biomass-reinforced composites further improve performance, with PLA–coffee systems reaching absorption values close to 1.0 in the high-frequency range (around 20,000 Hz), compared to lower values observed in cork-based and neat PLA structures. Overall, the study demonstrates that both infill architecture and biomass reinforcement play a critical role in tuning the acoustic response of additively manufactured PLA composites.