Evolution of the crack patterns in nanostructured films with subsequent wetting and drying cycles

Crack patterns in coatings present various morphologies as a signature of the matter to external stresses. Brittle films generally show a network of connected cracks due to a hierarchical formation process. On the contrary, non-sequential crack growth leads to a different morphology with few junctions. The present work focuses on the evolution of both crack networks under the effect of repeated stresses. The experimental work is performed through porous thin films over subsequent wetting and drying processes. The non-connected network of cracks is investigated through nanostructured films exhibiting compliant and elastic properties. Over repeated stresses, this crack network evolves until it reaches stabilization. The stabilization appears when the cracks stop growing and a shielding effect occurs. This behaviour is compared with a more classical connected network of cracks that do not evolve in the plane under the effect of repeated processes.