Structural design and additive manufacturing of multifunctional metamaterials with low-frequency sound absorption and load-bearing performances

Low-frequency noise is harmful but difficult to be removed due to the long wavelength and low dissipation coefficient. Acoustic absorption metamaterials (AAMs) can absorb low-frequency sound waves within a deep subwavelength scale using discrete cavities and have attracted extensive attention in electronics, automotive engineering and aerospace applications. However, the large cavity of traditional AAMs leads to a conflict between absorption and load-bearing capacity and limits the wide application. Here, we proposed a multifunctional metamaterial that can simultaneously achieve low-frequency sound absorption and excellent load-bearing capacity, namely acoustic absorption-bearing metamaterial (AABM). The advent of 3D printing technologies provides a time-and-labor-saving method for the fabrication of AABM samples. The load-bearing capacity of the AABM was compared with the triply period minimal surface (TPMS). The experiment results showed that the modulus of the AABM was 391 and 185% higher than that of primitive-type (P-type) and diamond-type (D-type) TPMS under the same volume fraction. Moreover, the AABM unit could achieve a nearly perfect sound absorption effect at 338 Hz with a thickness of only 20 mm. What's more, four AABM units with different absorption frequencies were combined and an absorption bandwidth was increased by about 600% compared to a unit cell. This structural design and additively manufacturing integration strategy can efficiently realize the key components of acoustic metamaterials and improve their application scenarios