Résumé:

We investigate the dynamics of thin sheets freely expanding in air. The sheets are produced by impacting a drop onto a small solid target or onto a cushion of liquid nitrogen, in order to suppress any dissipation process. To disentangle the role of capillary, viscous and elastic forces in the dynamics of the sheets several materials are used, whose rheological characteristics are tuned over several orders of magnitude: viscous liquids, viscoelastic Maxwell fluids and ultrasoft solids. In this talk, I will present our approaches to rationalize the spreading of sheets for viscous, viscoelastic and elastic materials by taking into account surface tension, elastic deformation and shear and biaxial viscous dissipations.