Abstract
Fatigue properties of surface film bonded materials with resin interlayer have to be discussed because these materials are often used in electronic parts and their expected electronic function must be maintained in operation. As a model specimen, pure copper films with the thickness of 100μm were bonded to steel base plates with epoxy resin. Using these specimens, fatigue testing was conducted under compressive and tensile mean stresses, and then fatigue crack initiation behavior inside the notch hole was observed using SEM (Scanning Electron Microscope) and fatigue crack propagation behavior on the surface film was observed in relation to the roughness pattern measured by laser-microscope. As a result, fatigue damage inside the notch root showed that cracks were caused at a few sites and connected through the thickness of film, irrespective of slip lines, during fatigue with each mean stress. In addition, fatigue crack propagation rate on the surface film increased near the notch with zigzag roughness of relatively smaller and larger region around crack for the compressive and tensile mean stresses, respectively. The fracture surface and the zigzag roughness around fatigue cracks were discussed in relation to the compressive and tensile mean stresses using an atomic potential energy model.
