Research progress on toughening mechanism and interphase property testing methods of SiC_f/SiC ceramic matrix composites

As a typical ceramic matrix composite （CMC）, SiC_f/SiC composite has enormous potential for application in the aerospace field because of the excellent properties such as high specific strength, high temperature resistance, oxidation resistance and good thermal shock resistance. The interphase between fiber and matrix plays a crucial role for protecting fibers, transmitting load and deflecting cracks, resulting in the pseudo-plastic fracture characteristics of SiC_f/SiC composites. The design scheme of interphase significantly affects its microstructural properties, thereby affecting the macroscopic mechanical properties and damage failure modes of SiC_f/SiC composites. In recent years, nano/micro fabrication techniques based on the focused ion beam （FIB）and nano/micro mechanical testing methods based on the nanoindentation are the effective methods to analyze and extract the interphase properties of SiC_f/SiC composites. The existing design schemes of interphase and the influence of interphase properties on toughening mechanism are reviewed. And also the application conditions, advantages and disadvantages of small-scale mechanical testing techniques including single fiber push-out/push-in and micropillar compression are summarized. Finally, the development trend for the research of CMC interphase properties are prospected: further standardizing the testing methods, building a high-temperature testing platform and modeling of testing data.