Microstructure and mechanical properties of milled fibre/SiC multilayer composites prepared by tape casting and pressureless sintering

In the present work, milled carbon fibre with high mechanical properties was used to reinforce silicon carbide, and Csf/SiC multilayer composites were prepared by tape casting and pressureless sintering. The milled C fibres were firstly dispersed in solvents with the aid of dispersant (Triton X-100) and then mixed with SiC slurry to make green Csf/SiC tapes to limit fibre breakage. The average length of C fibres slightly decreased with the increase of mixing time in the present duration, indicating that mixing the SiC slurry with the fibre-predispersed solution is an effective method for adding fibres with limited breakage. Fibres were homogeneously distributed in the tapes and tended to align fairly well along the tape casting direction. The relative density of the composite containing milled C fibres decreased with the fibre amount. The Csf/SiC multilayer composites demonstrated significant anisotropic shrinkage behaviour in different directions, while the addition of short C fibres hindered the shrinkage in the plane containing the fibres during sintering. Elastic modulus and bending strength decreased with increased porosity, which implies that bending properties are affected more significantly by residual porosity rather than fibres' properties.