A mortise–tenon joint inspired interface structure design for synergistically enhancing the mechanical properties and thermal shock resistance of Cf/(HfNbTaTiZr)C–SiC composites

Carbon fiber-reinforced high-entropy carbide ceramics (Cf/HECs) are considered promising candidates for ultrahigh-temperature structural applications. The fiber–matrix interface plays a crucial role in determining the overall performance of these materials. This study proposes a novel interface design strategy inspired by the traditional Chinese mortise–tenon joint. In this design, microscale carbon spheres are deposited on the surface of carbon fibers to function as the “tenon”, while the matrix serves as the corresponding “mortise”. Furthermore, a TiC interfacial layer is introduced to improve the interfacial bonding through atomic diffusion. Owing to this distinctive interface structure, the resulting Cf/(TiZrHfNbTa)C–SiC composite exhibits excellent mechanical properties, with a flexural strength of 1053.33 MPa and a fracture toughness of 9.77 MPa·m^1/2. Additionally, the composite demonstrates remarkable thermal shock resistance, with a critical thermal shock temperature difference (ΔT_c) of 802  °C. It also displays superior ablation resistance, characterized by a linear ablation rate of 3.27 μm·s⁻¹ and a mass ablation rate of 0.05 mg·s⁻¹.