Fractures en spirale, croissant, dune et étoile dans des couches minces

Drying mud or crazing in ceramics glaze leads to familiar hierarchical cracks network where a new crack connects perpendicularly to older ones. We report unusual spirals and croissants crack patterns in methylsiloxane drying thin films moderately adhering on a substrate. Such cracks are also observed in a very different situation when magnetron sputtering multilayers are under external tension. The amplitude and wavelength of the pattern are robusts and are orders of magnitude larger than the thickness of the layer. The propagation of the spiral and croissant cracks is driven by the combination of the residual energy available in the film, the fracture energy of the film and the interfacial energy. The crack propagation criteria and the pattern selection criteria form will be discussed. Mots clefs : rupture ; motifs ; film mince