In-plane thermal expansion behavior of dense ceramic matrix composites containing SiBC matrix

In order to reveal the effect of matrix cracks resulted from thermal residual stresses (TRS) on the thermal expansion behavior of ceramic matrix composites, SiBC matrix was introduced into Cf/SiC and SiCf/SiC by liquid silicon infiltration. The TRS in both two composites were enlarged with incorporating SiBC matrix which has higher coefficients of thermal expansion (CTEs) than SiC matrix. Due to the relatively high TRS, matrix cracks and fiber/matrix (f/m) debonding exist in Cf/SiC-SiBC, which would provide the space for the expansion of matrix with higher CTEs. For SiCf/SiC, no matrix cracking and f/m debonding took place due to the close CTEs between fiber and matrix. Accordingly, with the incorporation of SiBC matrix, the in-plane CTE of Cf/SiC between room temperature to 1100 °C decreases from 3.65 × 10−6 to 3.19 × 10−6 K-1, while the in-plane CTE of SiCf/SiC between room temperature to 1100 °C increases slightly from 4.97 × 10−6 to 5.03 × 10−6 K-1.