Improvement of sound absorption and flexural compliance of porous alumina-mullite ceramics by engineering the microstructure and segmentation into topologically interlocked blocks

Ceramic plates composed of topologically interlocked osteomorphic blocks with mono- and bimodal pore size distributions are fabricated by combining freeze gelation and sacrificial templating and trialled for sound absorption. These blocks present a concavo-convex geometry that constrains their movement solely by the contact with the neighbors. Our studies show that by using porous osteomorphic blocks, enhanced sound absorption coefficient (α) of 0.97 at 420 Hz can be reached, indicating that the gaps between blocks have a significant effect on the sound absorption at frequencies lower than 600 Hz, whereas the bimodal porosity of the block material enhances sound absorption for higher frequencies. Indentation tests confirm the advantages of the topologically interlocked structures, such as a spectacularly high flexural compliance, as compared to monolithic parts made from the same material. We concluded that materials design based on topological interlocking leads to an excellent combination of mechanical and sound absorption properties.