Microstructure, thermal-expansion, and tensile properties of M55J-type carbon fiber–reinforced, SiC and Si₃N₄ multilayered matrix composites

M55J-type carbon fiber–reinforced, SiC and Si₃N₄ multilayered matrix composites are fabricated through chemical vapor infiltration to achieve near-zero thermal expansion. The microstructure, interfacial regions, and thermal residual stresses (TRSs) of these composites are studied. The SiC matrix exhibits a high modulus, a high coefficient of thermal expansion (CTE), and strong bonding with carbon fibers, whereas the Si₃N₄ matrix features a low modulus, a low CTE, and weak bonding with carbon fibers. The C_f/SiC composite exhibits long penetrating cracks under the influence of TRS. However, in the fabricated multilayered (SiC-Si₃N₄)₅ matrices, only dispersive microcracks exist, providing space for matrix expansion. These multilayered matrices effectively constrain carbon fibers. The CTE of the C_f/(SiC-Si₃N₄)₅ composite can be as low as 0.10 × 10⁻⁶ K⁻¹ in absolute value. Meanwhile, cracks are repeatedly deflected at the interface of the multilayered matrix. The C_f/(SiC-Si₃N₄)₅ composite exhibits a tensile strength of 286 ± 3 MPa. With its near-zero thermal expansion and good tensile strength, this material demonstrates potential for spacecraft applications requiring high precision and stability.