Edge delamination of residually stressed thin films: viscoelastic effects

The theory of interfacial delamination governed by the critical energy release rate criterion is used to predict the initiation of crack growth in thin polyimide films bonded to elastic substrates. The elastic solution for thin films is extended to the viscoelastic case using a correspondence principle valid to the point of initiation of crack growth. A tentative model for decohesion under moisture cycling is proposed to model delayed failure due to exposure to ambient humidity. The effects of relevant parameters such as film thickness and relative humidity are shown for a PMDA/ODA polyimide film bonded to glass.