ͺqήΏΜjσθΥ«ΙyΪ·\«τ±ό@ΜψΚ
The Effect of Precracking Techniques on Fracture Toughness of Polymers
IR μE¬ΰVθv
Kuriyama, Takashi / Narisawa, lkuo
The technique of introducing an initial crack in the specimen for fracture toughness tests has a significant effect on the fracture toughness. This study is mainly concerned with the technique of pressing a razor blade to make a pre-crack in PMMA, GPPS and PC which were commercial grades. A pre-crack of 5 mm depth was in-troduced using a home-made notching machine at various temperatures. Then, three point bending tests were carried out to obtain the fracture toughness. For PMMA and GPPS, the crack length was difficult to be control at room temperature and 50. When the temperature was raised near Tg a pre-crack of 5 mm length without crazes could be introduced which reduced fracture toughness. In such a case, the shape of the pre-crack was like a natural crack, but residual stress remained around the crack. A pre-crack of 5 mm length could be introduced in PC even at room temperature. However, plastic deformation and residual stress were also generated around the crack. The fracture toughness was increased by the presence of this plastic deformation around the crack.
Key words: Fracture Toughness / Razor Precracking / Residual Stress / Craze / Plastic Deformation