Successive Measurements of Fracture Toughness in Mode I and Mode II with a Single Specimen I.

To measure fracture toughness in both mode I and mode II, possibility of successive measurement tests with a single specimen was examined. The DCB test for G(lc) measurement and the 3ENF test for G(llc), measurement were adopted because the shape of these specimen is the same. Effects of crack length and test order on fracture toughness were examined. Stable fracture toughness was achieved with both the DCB tests and the 3ENF tests when crack length was 100 mm. By including the influence of shear deflection in the corrected crack length, the influence of shear was removed from fracture toughness in mode I. But in mode II, the corrected crack length and fracture toughness have to be calculated with the equation considering shear deflection. Fracture toughness obtained by the succeeding test tends to be less than that obtained by the foregoing test.