Abstract
As model specimens of surface film-bonded materials with or without resin interlayer, pure copper and commercial grade iron films were bonded to the surface of steel base plates by epoxy resin bonding or by diffusion bonding. The film thickness was 100 and 50μm for the copper and 100μm for the iron, respectively. In the fatigue testing results using these specimens, the fatigue crack initiation life is smaller on the film bonded with epoxy resin than on the film bonded by diffusion. This tendency is particularly strong for the iron film. On the other hand, the epoxy bonding layer protects the inner base plate against fatigue damage, thus increasing the fatigue crack propagation life of the film-bonded plates with epoxy resin. In this connection, both the compressive residual stress on the iron film and the smaller tensile residual stress on the thinner copper film increases the fatigue crack propagation life significantly as compared with the larger tensile residual stress on the thicker copper film. Finally, the effect of the epoxy bonding layer on the fatigue crack propagation rate of the film is discussed in terms of the measured crack opening displacement range at 250μm behind from the crack tip, Δφ_<250>.
