Yu Zhang,Xu Shen,Qin Ma,Shuang Mu,Shaoming Dong,Jinshan Yang
In this work, the mechanical behavior of NITE-SiC f /SiC composites, accompanied by the damage mechanisms of SiC fibers and BN interphase during NITE process, are investigated. The results show that the fracture characteristic of NITE-SiC f /SiC composite is transformed from quasi-ductile mode to brittle mode with the elevating temperature, as well as severe damage of SiC fiber and BN interphase. The damage of SiC fibers is originated from high temperature, sintering aids corrosion and matrix compression. High temperature and sintering aids diffusion lead to the grain growth and strength degradation of SiC fibers. The damage of BN interphase is caused by the sintering aids corrosion, mainly the reaction of Al 2 O 3 , and matrix compression. The stress distribution is simulated via finite element analysis proving that up to 17.5 GPa and 17.0 GPa stress originated from matrix shrinkage during sintering process is applied to the fiber and interphase respectively, making the fiber deformation and interphase fragmentation. The degraded fiber strength and destroyed interphase structure weaken the load-bearing capacity and crack deflection ability, causing degradation of mechanical properties and reliability of composites. This work helps to comprehensively understand and optimize the properties of SiC f /SiC composites prepared by NITE process.
Zahoor Ahmad,Jianjun Chen,Hafsa,Zaheer Hussain,Muhammad Arfan,Tauseef Shahid,Fakhr e Alam
Chopped carbon fiber (CC f ) reinforced SiC ceramic matrix composites (CC f /SiC CMCs) hold potential as thermal structural materials. In this work, we investigated the impacts of dual protective interphases (pyrolytic carbon/boron nitride (PyC/BN)) deposited via chemical vapor deposition (CVD), along with the incorporation SiC whiskers (SiC w ) contents (20 wt%) on the structure and properties of as-fabricated CC f /SiC CMCs by NITE route. Structural and mechanical characteristics were explicated by the relevant advanced characterization tools. The introduction of PyC/BN dual protective interphase effectively preserved its integrity at elevated temperature and improved the toughness significantly via fiber pull-out and interfacial debonding mechanisms. Furthermore, incorporating 20 wt% SiC whiskers (SiCw) as secondary reinforcement yielded a synergistic toughening effect, promoting both the crack bridging and fiber pull-out behavior. This dual toughening mechanism led to a notable enhancement in mechanical performance, revealing an optimum bending strength of ∼356 ± 9.089 MPa, and toughness of ∼5.31 ± 0.194 MPa m 1/2 . Additionally, the inclusion of SiCw contributed to the creation of spatial network structure, potentially reducing the thermal expansion. The insights from this study advance the understanding of microstructural engineering in CC f /SiC composites, enabling future low-cost design and manufacturing of high-performance composites for extreme environments.
危险品化学品经营许可证（带存储）