Séminaire Liquides/Mat. molle

Vendredi 18 Juillet 2014 à 11h00.

Exotic cracks in thin films

''Nanometer to micrometer thin film coatings are extensively used in material science to protect and functionalize surfaces. Coating processes however generally result into residual strains and may induce the propagation of cracks with dramatic consequence on film reliability. Such cracks result into disordered network patterns observed in china crockery or dry mud, and bear analogies with plant leaves venation or urban networks. We found that classical criteria fail to predict the stability of thin films in the case of moderate adhesion. Moreover intriguing cracks of regular geometry are found to self-replicate an initial triggering pattern independently from the local material properties. We describe the fracture mechanism with universal energy arguments and provide a simple model describing the crack path. We show that the extreme robustness of the peeled pattern can turn fracture into a design tool, opening potential applications to micro-tailoring.''