ICSV26

Porous materials everywhere in the Universe! At the Planck length scale (10e-33 cm), physicists describe space as a quantum foam. At the cosmic scale (> 10e26 cm), galaxies are distributed according to the structure of a cosmic foam. Closer to the human scale, natural porous media are formed (honeycomb, soil, rock, bone). This omnipresence and the remarkable properties of these media have long fascinated the engineers who have inspired them to create porous materials adapted to different applications of mechanical engineering: sound absorption and insulation, cooling of electronic components, implants and substitute bones, light structures, absorption of impacts, porous electrodes for fuel cells, filtration and purification of water. After an introduction of the porous media at these different scales, this presentation gives an overview of the porous materials used in noise control. This overview presents conventional and unconventional porous materials. Man manufactures conventional porous materials based on conventional chemical and physical processes and the mimicry of natural porous media. However, it seems that these materials have reached the physical limits of sound absorption and sound insulation. Moreover, their use becomes an important issue in terms of sustainable development. To obtain acoustic properties that go beyond those of conventional materials, and materials more in line with sustainable development, man must intervene by structuring the material and choosing materials safer for the environment. Metamaterials and materials designed using an ascending or a multiscale approach belong to the family of unconventional materials. Similarly, materials based on natural fibers and recycled materials belong to this family. The presentation mainly focuses on this family of materials and the underlying design methods, while presenting examples of applications and comparisons to conventional materials. In parallel, what makes a porous material a good acoustic absorber will be discussed and analyzed.