In the last two decades, fibre-reinforced SiC ceramic-matrix composites (CMCs) have attracted extensive interests. Owing to the designable multi-scale microstructure feature and the tailorable processing methods such as chemical vapour infiltration and polymer derived ceramics, SiC matrix composites attain great potential as multifunctional composites. Through designing the fibre, interphase, matrix and coating, the composite exhibits a multitude of functionalities which are desirable for various technological applications. Besides strengthening and toughening design of CMCs, three inspiring issues of multifunctional CMCs are receiving increasing attention, including crack self-healing, friction self-lubrication, and electromagnetic shielding and absorption, which are the key mechanisms to promote the application of CMCs in hot structures of engines and aerospace vehicles, braking pads/discs, various electronic devices, etc. The present review covers the main mechanisms on strengthening and toughening, crack selfhealing, friction self-lubrication, and electromagnetic shielding and absorption of CMCs. Key developments and future challenges in this field are summarised.

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A 2D C/SiC-BC x composite was tested under static load in both wet oxygen and dynamic combustion atmospheres. The microstructural evolution and selfhealing mechanisms of the composites were investigated by a scanning electron microscope. The results indicated that the multi-scale deflection of cracks played an important role in improving the performance of 2D C/SiC-BC x in both atmospheres. The glass phase could seal the matrix cracks and flow into the fiber bundles through the cracks. As a result, the fibers and fiber/matrix interface within 2D C/SiC-BC x were protected from oxidation. The retention rate of hightemperature tensile strength of 2D C/SiC-BC x got a significant improvement in wet oxygen atmosphere at 700 8C, compared with 2D C/SiC. The damage rate of 2D C/SiC-BC x remained in a smaller scope in dynamic combustion atmosphere. The damage rates of the 2D C/SiC-BC x were about 80% and 90% lower than that of 2D C/SiC, respectively at 700 and 900 8C.

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Lacking the structural information of crystalline solids, the origin of the relaxation dynamics of metallic glasses is unclear. Here we report the evolution of stress relaxation of high-entropy metallic glasses with distinct 𝛽𝛽-relaxation behavior. The fraction of liquid-like zones, determined at each temperature by the intensity of stress decay, is shown to be directly related to both the aging process and the spectrum of relaxation modes obtained by mechanical spectroscopy. The results shed new light on the intrinsic correlation between the static and dynamic mechanical response in high-entropy and conventional metallic glasses, pointing towards a sluggish diffusion high-entropy effect in the liquid dynamics.