Variation in mode II dominated interface fracture of stainless steel–epoxy bonds. Part 2: Multi-scale damage analysis

The fracture at stainless steel–epoxy interfaces is investigated using acoustic emission (AE), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The effects of substrate morphology and aging on the interface are traced. Narrow grooves at the grain boundaries of steel introduce submicron-scale mechanical interlocking and result in high toughness. Sharp ridges after nitric acid etching introduce secondary cracking but may initiate interface collapse. The tough fracture process induced negligible AE. Short-term aging of an interphase region causes diminished secondary cracking and the mechanical interlocking to malfunction.