Toughening Mechanism of Ceramic Based Composites for Dynamic Crack Propagation

2000 Fiscal Year Final Research Report Summary

• Project/Area Number: 10450249
• Research Category: Grant-in-Aid for Scientific Research (B).
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Composite materials/Physical properties
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: TANABE Yasuhiro Tokyo Institute of Technology, Materials and Structures Laboratory, Associate Professor, 応用セラミックス研究所, 助教授 (70163607)
• Co-Investigator(Kenkyū-buntansha): WAKAI Fumihiro Tokyo Institute of Technology, Materials and Structures Laboratory, Professor, 応用セラミックス研究所, 教授 (30293062) ; AKATSU Takashi Tokyo Institute of Technology, Materials and Structures Laboratory, Lecturer, 応用セラミックス研究所, 講師 (40231807) ; YASUDA Eiichi Tokyo Institute of Technology, Materials and Structures Laboratory, Professor, 応用セラミックス研究所, 教授 (70016830)
• Project Period (FY): 1998 – 2000
• Keywords: Ceramics / Composite / Work-of-fracture / Sharpy Impact Test / Dynamic Crack Propagation

Research Abstract

The problem on the Work-Of-Fracture (WOF) measurement of ceramic matrix composites reinforced with ceramic fibers has been examined throughout the term of the project. Fracture processes during the WOF measurement has also scrutinized considering the correlation between crack path and the microstructure of the composite. It was found that the sharpy impact test was suitable for the WOF measurement, because it was rather easy to rupture a specimen such as C/C or SiC/SiC composite into two pieces through the impact test. The WOF-value measured, however, should be higher than a few kJ/m^2 in order to evaluate WOF with high precision. The validity of the sharpy impact test for WOF measurement was confirmed by the insignificant difference between WOF-values measured by the impact and the static 3-point bend tests. Furthermore, it was found that the WOF-value strongly depended on the ratio of Span to the Width of a bend beam, S/W.The remarkable dependence of WOF on S/W was attributed to elastic strain energy stored in the specimen and interlayer shear and/or debonding fracture. Both of them were given in terms of S/W, while the former was regardless of the fracture process on the one hand, the latter occurred with relation to the rupture of the specimen. It was found that the large extent of the interlayer fracture remarkably increased the WOF-value of the composite.