Mechanical and thermal shock properties of Cf/SiBCN composite: Effect of sintering densification and fiber coating
Mechanical and thermal shock properties of Cf/SiBCN composite: Effect of sintering densification and fiber coating
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DOI：
10.1111/jace.18364
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发表时间：
2022-02-11
影响因子：
3.9
通讯作者：
Zhou, Yu
中科院分区：
文献类型：
--
作者：
Niu, Zi-bo;Wang, BingZu;Zhou, Yu
采用聚合物浸渍热解法在碳纤维表面制备树脂衍生碳涂层，然后采用机械合金化法制备碳氮化硅硼粉体，最后采用热压法制备碳纤维增强碳氮化硅硼复合材料。研究了烧结致密化和纤维涂层对复合材料显微组织、力学性能、抗热震性能和失效机理的影响。纤维桥接阻碍了烧结致密化，导致纤维致密区缺陷增多，强度降低。然而，较高的烧结温度（1800-2000℃）可以显著改善材料的力学性能，包括抗弯强度、维氏硬度和弹性模量，因为进一步烧结致密化提高了基体强度和纤维/基体结合强度，而断裂韧性的变化不明显（2.24-2.38 MPa中心点m(1/2)），这是由于较高的脱粘阻力和较小的拉出长度的相互作用。然而，纤维涂层通过保护碳纤维免受化学腐蚀和热应力和外部应力的破坏，大大提高了断裂韧性。由于较低的热膨胀系数、较低的纤维加载比、较低的纤维/基体界面应力集中和较好的缺陷修复效果，较低的烧结温度有利于复合材料的抗热冲击性能，热冲击消退机制是界面损伤。
In this work, resin-derived carbon coating was prepared on carbon fibers by polymer impregnation pyrolysis method, then silicoboron carbonitride powder was prepared by mechanical alloying, and finally carbon fiber-reinforced silicoboron carbonitride composites were prepared by hot-pressing process. The effects of sintering densification and fiber coating on microstructure, mechanical properties, thermal shock resistance, and failure mechanisms of the composites were studied. Fiber bridging hinders the sintering densification, causing more defects in fiber-dense area and lower strength. However, higher sintering temperature (1800-2000 degrees C) can improve mechanical properties significantly, including bending strength, vickers hardness, and elastic module, because further sintering densification enhances matrix strength and fiber/matrix bonding strength, while the change of fracture toughness is not obvious (2.24-2.38 MPa center dot m(1/2)) due to counteraction of higher debonding resistance and less pull-out length. However, fiber coating improves fracture toughness greatly via protecting carbon fibers from chemical corrosion and damage of thermal stress and external stress. Due to lower coefficient of thermal expansion, lower fiber loading ratio, less stress concentration at the fiber/matrix interface, and better defect healing effect, lower sintering temperature favors thermal shock resistance of composites, and thermal shock recession mechanisms are the damage of interface.