Triple tunability of phononic bandgaps for three-dimensional printed hollow sphere lattice metamaterials

Sound and vibration pollution is ubiquitous in urban areas. How to alleviate the pollution has been concerned because of their broad frequency range. Currently, phononic crystals (PCs) are potential candidates for solutions. However, specific geometry, mass, and stiffness of PCs produce only fixed narrow bandgaps. Many PCs can only be tuned from one bandgap to the other. Here, in order to realize triply or multiply tunable phononic bandgaps, we introduce the three-dimensional (3D) printed hollow sphere lattice metamaterials. Utilizing the reversible temperature-dependent stiffness of the glassy polymer and discontinuity of stable thermal field in the lattice structure, we soften triply the binders between hollow spheres, keep hollow spheres hard, and attain triple modulation of the phononic bandgaps, which was validated by conducting low-amplitude transmission testing and numerical simulations. The results show that phononic bandgaps can be magnified by 37.5%. The findings reported here provide a path for designing phononic lattices with controllable and broad band gaps, offering extensive potential applications in acoustic and vibration suppression, wave guiding or filtering, and nondestructive testing.

Automated summary

Sound and vibration pollution is a common issue in urban areas. This study introduces 3D printed hollow sphere lattice metamaterials to achieve tunable phononic bandgaps. By softening the binders between hollow spheres and keeping the spheres hard, the phononic bandgaps can be modulated and magnified.