Research on the pore structure and flow characteristics of 2D plain-woven and 3D needled preform ceramic matrix composites

Ceramic matrix composites (CMCs) are a typical porous medium, featuring significant advantages of high-temperature resistance, lightweight, low density and high specific strength. Its internal connected pores can be used as flow channels for transpiration cooling of hot-end components of aero-engines. This paper carries out flow characteristics and analysis on the pore structure characteristics of CMCs with two types of preform: plain woven and three-dimensional needled. The mechanism by which the pore structure affects the flow resistance behavior is also examined. Firstly, through flow experiments, flow rate-pressure drop curves are obtained, and combined with the Darcy-Forchheimer equation, the permeability and inertial constant are obtained. Then, schemes such as CT scanning and Archimedes principle are adopted to obtain characteristic parameters such as pore characteristics and porosity of CMCs, and on this basis, the influence of weaving processes on pore morphology is analyzed. Finally, the internal flow mechanism of CMCs is analyzed; in particular, combined with the characteristics of pore structure distribution, the proportions of inertial resistance and viscous resistance in flow resistance are compared, and the influence mechanism of pore structure on flow characteristics is clarified. The results demonstrate that the fluctuation degree of porosity, pore connectivity, and the specific surface area influenced by pore size all exert a critical effect on the formation mechanism of flow resistance sources. Experimental results show that CMCs have good flow characteristics, and their flow resistance are similar to those of metallic sintered materials. The present results provide fundamental data on the pore structure and flow characteristics of CMCs, which can serve as a basis for analyzing the internal flow behavior and guiding the pore-structure design in transpiration-cooling applications.