FE simulation of interfacial delamination between SiO2 thin film and polymeric substrate

International audienceOphthalmic lenses are made of plastic polymeric substrates usually coated with functional treatments composed of 5 to 15 layers, ranging from micrometers to nanometers. Each of these interfaces may lead to delamination due to poor adhesion, and therefore affect the vision and comfort of wearers. The interface between the anti-reflective stack and the hardcoat is particularly sensitive because of chemical and mechanical contrast of its materials. To better understand mechanisms that lead to loss of adhesion between the SiO2 anti-reflective layer deposited on the anti-scratch hardcoat, compression experiments are performed to induce buckling of SiO2 layer. A Finite Element Model is developed to refine characterization of interfacial properties. Simulation of buckling phenomenon and delamination of SiO2 layer under compressive stress is proposed. Interfacial properties between SiO2 layer and hardcoat are modeled using cohesive elements following a traction separation law. Geometry of buckle yielded by the model is compared against experimental results to adjust the numerical model and access interfacial properties