Design and fused filament fabrication of multilayered microchannels for subwavelength and broadband sound absorption

A comprehensive procedure to design and manufacture multilayered microchannels presenting competitive mechanical properties, effective subwavelength and near perfect broadband sound absorption in targeted frequency ranges is presented. The acoustic properties of microchannels are predicted with the Johnson-Champoux-Allard-Lafarge (JCAL) model. The JCAL parameters are calculated with the Two-scale Asymptotic Method (TAM) and the sound absorption coefficient of multilayered microchannels is simulated with the transfer matrix method (TMM). The simplex Nelder-Mead optimization method is used to find the size of the channels and the stacking sequence leading to effective acoustic absorption for three different frequency ranges (500–2400 Hz, 2400–6500 Hz and 500–6500 Hz). 30 mm-thick samples with up to 30-layers of unobstructed and non interconnected channels and microchannels were successfully produced via fused filament fabrication (FFF). The minimum channel size is 100 µm which is very appropriate to produce micro-perforated panels or acoustic liners with optimal absorption and different degrees of freedom. Multilayered microchannels with absorption average up to 0.87 and noise reduction coefficient (NRC) up to 0.49 were produced. The multilayered microchannels offer a good compromise between effective acoustic properties and useful mechanical properties compared to other 3D printed acoustic structures and can be considered as viable candidates for applications where structural resistance is required.

Mots clés

acoustic modeling; sound absorbing materials; design and optimization; additive manufacturing; multifunctional structures