Pore geometry and permeation characteristic of 3D–Cf/SiC composites fabricated via precursor infiltration and pyrolysis

To investigate the correlation of pore geometry and permeation characteristic, this paper evaluated the three-dimensional braided and/or woven carbon fabrics reinforced silicon carbide (3D–Cf/SiC) composites by mercury intrusion porosimetry, scanning electron microscopy and bubble point measurement. The flowrate–pressure curves of N2 through Cf/SiC panels were measured by pressure apparatus at room temperature, then the flow modes conversion were analyzed, and permeability K was calculated. The pore geometry of 3D–Cf/SiC is supposed to be a three dimensional network composed of multi-sized interconnecting chambers, channels and cracks with sizes from microns to nanometers. The permeability prediction by porosity proves that the contents and sizes of the full open inter-bundle channels are the determinant factors for the intrinsic through-flow capability of the composite. The capillary bundle model displays feasibility to predict K when the actual full-open pore size distribution is obtained by appropriate means, such as bubble point method.