PhD Offer: Enhanced Acoustic Foams
The microstructure of open-cell solid foams is inherited from the liquid foams that preceded them in the production phase: pores are connected by throats which size depend on both pore size and density. For several years now, we study the functional properties of monodiperse open-cell foams made from cement, geopolymer, elastomer, hydrogel, … Monodispersity appeared to be a key element to understand fully those properties. For example, we showed how acoustic absorption is set by the foam microstructure.
To further improve those properties, it turns out to be necessary to introduce/combine other ingredients to optimize the basic microstructure. It is proposed to deposit elastic material into to foam porosity, in the form of membranes at the level of the passages between pores (see figure), which could allow to put into action local mechanical resonance phenomena. According to a first model of this effect, it is possible to find resonance regimes that allow a very strong absorption of sound waves. This type of regime seems to have been observed in flexible foams; here we propose to develop more mechanically resistant materials thanks to the rigid skeleton of the foam that hosts the flexible membranes.