Effect of resin impregnation on the mechanical properties of bulk-superconductors with holes

We have measured the rupture strength of Y-Ba-Cu-O rods having an artificial hole filled with and without epoxy resins using a three point bending test. The rupture strength was reduced by introducing the hole. In contrast, the sample with the hole filled with resin exhibited higher rupture strength than that of virgin bulk materials. These results suggest that the improvement of mechanical properties through resin impregnation is ascribed to the prevention of crack propagation along the cleavage plane due to the presence of resin. The presence of internal defects was also confirmed with the observation of ultrasonic wave.