Pore defects repair of CCF/SiC composites fabricated by additive manufacturing

This work presents the pore defects repair of additively manufactured chopped carbon fibre reinforced silicon carbide (CCF/SiC) composites using a combination of chemical vapour deposition (with methyltrichlorosilane and hydrogen as the precursor material) and reactive melt infiltration. The in-situ generation of silicon carbide nanowires (SiC nws ) in the CCF/SiC composites significantly reduced the initial pore defects size, while the secondary SiC and free Si filled and closed the pore defects. The X-CT shows that the CCF/SiC composite after pore defects repair was internally dense and no significant pore geometry was observed. The incorporation of micron-sized CCF and nano-sized SiC nws as reinforcing phases resulted in a synergistic toughening effect. Specifically, the CCF enhances toughness through fibre debonding and pull-out mechanisms, while the SiC nws contribute to toughening through nanowire bridging and pull-out mechanisms. This dual toughening mechanism significantly improved bending strength from 210.7 to 274.5 MPa and elevated the fracture toughness from 3.2 to 3.6 MPa m 1/2 . Another notable advantage of the SiC nws is their ability to form a space network and reduce the thermal expansion coefficient. Consequently, this novel microstructural pore defects repair approach further enhanced the overall performance and reliability of the CCF/SiC composites based on additive manufacturing. This innovative approach holds great promise for the development of high-performance complex-structure CCF/SiC composites with wide-ranging applications across various industries.