不同界面SiC/SiC复合材料的断裂行为研究

doi:10.15541/jim20150278

摘要/Abstract

摘要：

碳化硅纤维增强碳化硅复合材料(SiC/SiC)是极具前景的高温结构材料。通过先驱体浸渍裂解(PIP)工艺分别制备了PyC界面和CNTs界面SiC/SiC复合材料, 对两种SiC/SiC复合材料的整体力学性能以及界面剪切强度等进行了测试表征, 并对材料中裂纹的产生与扩展进行了原位观测。结果表明, 两种界面SiC/SiC复合材料弯曲强度相近, 但PyC界面SiC/SiC复合材料的断裂韧性约为CNTs界面SiC/SiC复合材料的两倍。在PyC界面SiC/SiC复合材料中, 裂纹沿纤维-基体界面扩展, PyC涂层能够偏转或阻止裂纹, 材料呈现伪塑性断裂特征; 而在CNTs界面SiC/SiC复合材料中, 裂纹在扩展路径上遇到界面并不偏转, 初始裂纹最终发展为主裂纹, 材料呈现脆性断裂模式。

关键词: SiC/SiC复合材料, 界面, 力学性能, 断裂行为, 原位观测

Abstract:

SiC fiber reinforced SiC matrix composites (SiC/SiC) are promising materials for high temperature structural applications. In this work, SiC/SiC composites with Pyrolytic Carbon (PyC) interface or Carbon Nanotubes (CNTs) interface were fabricated by polymer infiltration and pyrolysis (PIP) process. Overall mechanical properties and interfacial shear strength of the SiC/SiC composites were characterized and crack growth processes were observed in situ by scanning electron microscope (SEM). The results indicate that flexural strengths of two types of SiC/SiC composites are similar, but the fracture toughness of the SiC/SiC composite with PyC interface is twice as much as that of the SiC/SiC composite with CNTs interface. Cracks propagate along the fibre-matrix interface in the SiC/SiC composite with PyC interface, which can be deflected or arrested by the PyC interface, hence the composite exhibits a pseudo-ductile fracture behavior. However, the CNTs interface fails to cease the crack in the SiC/SiC composite with CNTs interface, so the initial crack propagates rapidly through the fibers leading to final main crack, and a brittle fracture mode.

Key words: SiC/SiC composite, interface, mechanical properties, fracture behavior, in situ observation

中图分类号:

TB232

赵爽, 杨自春, 周新贵. 不同界面SiC/SiC复合材料的断裂行为研究[J]. 无机材料学报, 2016, 31(1): 58-62.

ZHAO Shuang, YANG Zi-Chun, ZHOU Xin-Gui. Fracture Behavior of SiC/SiC Composites with Different Interfaces[J]. Journal of Inorganic Materials, 2016, 31(1): 58-62.

图/表 7

图1 PyC(a)和CNTs(b)界面层的微观形貌

Fig. 1 SEM images of (a) PyC coating and (b) CNTs on the SiC fiber surfaces

表1 SiC/SiC复合材料的力学性能

Table1 Mechanical properties of SiC/SiC composites

Composites	P-SiC/SiC	C-SiC/SiC
Interface	PyC	CNTs
Flexural strength /MPa	330.2	324.4
Fracture toughness /(MPa∙m^1/2)	15.6	7.7
Interfacial shear strength /MPa	105.9	72.1

图2 SiC/SiC复合材料的载荷-位移曲线

Fig. 2 Load/displacement curves of the SiC/SiC composites

图3 SiC/SiC复合材料的断口形貌

Fig. 3 Fracture surface of the SiC/SiC composites (a, b) P-SiC/SiC composite, (c, d) C-SiC/SiC composite

图4 双悬臂梁样品压缩加载示意图

Fig. 4 Schematic diagram of the double-cantilever specimen

图5 P-SiC/SiC复合材料的裂纹萌生与扩展

Fig. 5 Crack initiation and propagation in P-SiC/SiC composite

图6 C-SiC/SiC复合材料的裂纹萌生与扩展

Fig. 6 Crack initiation and propagation in C-SiC/SiC composite

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