界面类型对三维Nextel 720纤维增韧莫来石陶瓷基复合材料力学性能的影响

采用化学气相渗透工艺在Nextel 720纤维表面制备PyC和PyC／SiC两种涂层，然后以正硅酸乙酯和异丙醇铝作为先驱体，以先驱体浸渗热解法制备三维Nextd 720纤维增韧莫来石陶瓷基复合材料，比较分析了两种涂层复合材料的力学性能和断裂模式。结果表明：具预先涂覆PyC的复合材料中纤维与基体直接接触，发生烧结形成强结合界面，复合材料脆性断裂，三点抗弯强度仅56MPa。PyC／SiC涂层则演化为间隙／SiC复合界面层，SiC成为阻滞纤维与基体接触的阻挡层，间隙保证了纤维拔出，复合材料韧性断裂且三点抗弯强度高达267．2MPa。

EFFECT OF DIFFERENT INTERFACES ON THE MECHANICAL PROPERTIES OF 3D NEXTEL 720/MULLITE COMPOSITES

PyC and PyC/SiC interface layers were coated on the surface of Nextel 720 fibers by chemical vapor infiltration. The 3D Nextel 720/mullite composites were fabricated by precursor infiltration and pyrolysis using TEOS- AIP as precursor. The mechanical properties and rupture model of the 3D Nextel 720/mullite composites with PyC and PyC/SiC coating were analyzed. Results indicate that the rupture model is brittle rupture for the 3D Nextel 720/mullite composites with PyC coating, and the flexural strength is 56 MPa only, due to the forming of strong bonding interfaces between fibers and matrix in the 3D Nextel 720/mullite composites during the pyrolysis process. But gap/SiC composite interfaces resulted from PyC/SiC interface layers lead to a weak bonding between fibers and matrix. As an obstruct layer, SiC prevents fibers from contacting to matrix, and the gap results in the pulling-out of fibers. The rupture model of the 3D Nextel 720/mullite composites with PyC/SiC coating is toughness failure and the flexural strength reaches to 267.2 MPa.