Effect of preform structure on mechanical and thermal properties of SiCf/SiC composites

In this paper, SiCf/SiC composites with three kinds of preform structures, namely 2D multilayered, 3D angle-interlock and multiaxis 3D braided, were prepared by chemical vapor infiltration. The influences of preform structure on mechanical and thermal properties of SiCf/SiC composites were discussed in detail, on the basis of comprehensive analyses of fiber arrangement, SiC matrix and pore distribution, and so on. The results show that the mechanical properties and thermal conductivity are comprehensively affected by the fiber arrangement and the density of composites, while the coefficient of thermal expansion is mainly influenced by the fiber arrangement. In addition, the thermal conductivity of 2D multilayered, 3D angle-interlock and multiaxis 3D braided composites could be explained by series model and parallel model, respectively. The continuous three-dimensional network structure of SiC matrix layer inside multiaxis 3D braided composites could be regarded as a fast channel for heat flow, resulting in a higher thermal conductivity. As the temperature increases, the scattering between phonons gradually increases and becomes the main factor affecting the thermal conductivity. In this case, the role of the SiC matrix layer as a fast channel for phonon propagation in multiaxis 3D braided composites gradually weakens.