Ichihito Narita

Using crack shear displacement (CSD) and load point displacement (LPD), which can measure the deformation of the adhesive layer with high sensitivity, end-notch flexure (ENF) fracture toughness tests were performed using three-point bending to investigate the joint at the crack tip. The load-displacement curves showed that after yielding, the load increased with a gradual non-linearity, and that the load increase slowed down when micro-cracking occurred in front of the crack tip. After the test, the specimens were immersed in fluorescent penetrant solution, and an R-curve was generated from the actual crack length observed at the fracture surface. It was confirmed that the increase in energy release rate ceased when microcracks occurred in front of the crack tip, and that the crack propagated steadily.