Microstructures and mechanical properties of three-dimensional ceramic filler modified carbon/carbon composites

A three-dimensional needled carbon fiber integrated felt was used as the preform for SiC or B₄C modified carbon/carbon (C/C) composite: C/C-B₄C or C/C-SiC which was prepared through unidirectional pressure slurry infiltration-filtration followed by chemical vapor infiltration. There were four kinds of interface microstructure modes between ceramic filler particles and pyrolytic carbon (PyC) matrix: enwrapping, encircling, embedding and infilling. For C/C-B₄C, enwrapping, encircling and embedding were the main modes. For C/C-SiC, embedding was the main one. The addition of ceramic filler complicated some fiber/matrix interfaces, forming composite interface layers and dual interface layers. There were three kinds of characteristic fiber/matrix interfaces: (fiber/filler/PyC)_n/PyC, fiber/(filler/PyC)/PyC, fiber/filler/PyC. The flexure strength of C/C was 98 MPa, whereas those of C/C-B₄C and C/C-SiC were 200 and 140 MPa, respectively. The addition of ceramic filler not only increased the bonding strength of some fiber/matrix interface, but also toughened the PyC matrix.