Influence of pulse duration on debonding of two layer materials by laser shock technique

Abstract

By inducing high power laser shocks in the substrate of a two layer material (substrate plus coating), it is possible to generate a tensile stress at the interface and so to use the technique as a test of the level of coating adhesion. The features of the stress history at the interface are governed mainly by the laser shock parameters (related to the laser intensity and the pulse duration) and by the influence of the properties of the target (shock impedance, thickness, strength, etc.) on shockwave propagation. The influence of these parameters on the stress at the interface is discussed on the basis of a simplified analytical model of laser shock propagation in the coated substrate. Some key points such as the interaction of pulse duration and coating thickness are checked by experiment. The study allows some guidelines to be inferred on the use of the laser shock debonding technique as a non-destructive test of adhesion in two layer materials.