LU Shuwei, LUO Ruiying, WANG Lianyi
(School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191, China)
Abstract: 3D-braided Al2O3 fiber preforms were used to prepare Al2O3f/Al2O3 composites by sol-gel method. Before the sol-gel process, the preforms were coated with pyrolytic carbon (PyC) by chemical vapor infiltration (CVI). The mechanical property and microstructure were investigated via the three-point bending experiments and SEM analysis. The results indicated that the flexural strength of the uncoated composite was only 55.8 Mpa, while the coated composites with 0.6 μm and 0.8 μm PyC interfaces were 231.3 MPa and 158.2 MPa, respectively, increased by 314.5 % and 183.5 %. Through the microstructure analysis of the fracture surface, it was found that the PyC interface played a vital role in the toughening mechanism of the continuous fiber, such as the fiber pull-out, interface debonding and crack deflection, thus the brittle-ductile transition of composite was achieved.
Key words: Al2O3f/Al2O3; PyC interface; sol-gel; mechanical property; microstructure