Key role of interphase in continuous fiber 3D printed ceramic matrix composites

During the continuous fiber (CF) 3D printing process, the high viscosity of the printing materials makes it difficult to penetrate into the fiber bundles, resulting in the lack of matrix and poor interfacial bonding. In this paper, the interfacial bonding of CF 3D printed ceramics was controlled by chemical vapor infiltration (CVI). A thermoplastic ceramic precursor and continuous carbon fibers were used as printing materials, and complex lightweight structures were printed. After cross-linking and pyrolysis, the ceramic precursor was converted into amorphous SiOC. Then CVI process was carried out to control the interphase and fill the fiber bundles with ceramic matrix. The flexural strength and modulus increased with the increase of CVI time. When the PyC interphase thickness was 150–250 nm, the flexural strength increased by about 203%. Each fiber was surrounded by the interphase and dense ceramic matrix, which was the reason for the improvement of mechanical properties.