Real-time high-temperature 3D imaging of the fracture behaviours in an aerospace-grade ceramic-matrix composite

Abstract

SiC_m/SiC_f ceramic-matrix composites (CMCs) are considered as potential candidates in aerospace applications because of their thermostability, low density and high strength. Various toughening mechanisms result from various structural architectures were adopted to overcome the inherent brittleness of monolithic SiC ceramic. Thus, it is essential to have a better understanding of the relationship between mechanical behaviours and complex microstructure of SiC_m/SiC_f CMCs. In this study, in situ X-ray synchrotron computed micro-tomography was utilized to obtain an insightful view of the progressive fracture processes of the 2.5 dimensional SiC_m/SiC_f CMC samples under three-point bending test at room temperature (RT) and 1250 ℃ in Air. 2.5D SiC_m/SiC_f CMC displayed a decrease of average flexural strength from 470 ± 44.65 MPa at RT to 365 ± 30.39 MPa at 1250 ℃ which is ~77.5% of RT values. At loading steps, load drops were identified on the load-displacement curves of the in situ three-point bending tests. Crack growth corresponding to load drops was observed by analysing X-ray scanned images. Samples tested at RT displayed a graceful and gradual fracture process- the toughening mechanisms granted by complex microstructure have prominently improved the resistance of the material to damage by arresting and deflecting crack propagation. Meanwhile, samples tested at 1250 ℃ displayed a rather more abrupt fracture process compared with RT specimen. In situ three-point bending tests combined with synchrotron X-ray computed microtomography has proven to be a powerful tool in studying the relationship between the mechanical behaviour and the microstructure of the 2.5D SiC_m/SiC_f CMC.

Date of Award	9 Aug 2023
Original language	English
Awarding Institution	University of Bristol
Supervisor	Matthew D Smith (Supervisor) & Dong Liu (Supervisor)