Polymer systems for liquid silicon infiltrated ceramic matrix composites

This work investigated the suitability of different commercially available polymers for manufacturing ceramic matrix composites (CMC) based on the liquid silicon infiltration (LSI) process. Carbon fiber reinforced composites based on thermoplastic PEEK, phenolic novolak resin and three polyaddition curing cyanate ester resins were produced and characterized using DMA, TGA and dilatometry. The composite samples were pyrolyzed and infiltrated using liquid silicon to obtain the desired CMC. The manufactured CMC were characterized through light-microscopy, three-point bending tests, SEM analysis and X-ray diffraction with phase composition analysis. Interactions between the properties in the polymer and ceramic state were revealed. The pyrolysis mechanism and char yield clearly determine the microstructure, the delamination tendency during pyrolysis and the phase composition in the ceramic state and ultimately define the mechanical properties of the CMC. It was shown that high char yield cyanate ester resins are well suited for the LSI process. Damage-tolerant C/C-SiC ceramics with a bending strength of more than 130 MPa were obtained for all resin systems. Overall, cyanate ester resin based CMC displayed a unique combination of favorable processing properties such as low-viscosity, polyaddition cure, high char yield and exceptional fiber-protection qualities and present a promising resin system for future CMC development.