The design idea of layered composite ceramics is to add soft and high-temperature materials to brittle ceramics to make layered composite ceramics. Although its composition is simple, the fine composite structure ensures the excellent mechanical properties of materials. Layered composite is a kind of bionic design. The characteristics of these bionic materials can not only improve the toughness of ceramics from the component design, but also design new materials from the macroscopic structure, forming the synergistic effect of multistage toughening mechanism of different scales, which is a new idea of reinforcing and toughening ceramics. At present, the commonly used bionic structure has bamboo and wood structure, shell structure and so on.

Different from traditional methods to improve material properties, such as eliminating defects, the toughening mechanism of layered composite ceramics is independent of strength and defects, and is a defect resistance mechanism of energy absorption and dissipation mechanism. According to the strength of interface, layered composite ceramics can be divided into weak interface, strong interface and ductile interface materials. Different interface combinations correspond to different toughening mechanisms.

A weak interlayer is introduced between two layers of high-strength ceramic substrates. When the stress of layered composite ceramics with a weak interface reaches a certain intensity, the crack grows to form a micro crack, and the micro crack will deflect or laminate along the weak interface, releasing energy in the process of crack growth and achieving the effect of material toughening.

This kind of layeredcomposite ceramics is characterized by a large increase in fracture toughness and no sudden fracture of the material. However, due to the existence of weak interlayers, the overall strength of the material is reduced.

Strong interfacial bond is a kind of interfacial binding force to form mutual restraint between layers, which is beneficial to form strong residual stress in the material. If the residual stress is artificially designed, it becomes prestressed. Strong toughening mechanism of interfacial residual stress by the use of layered composite ceramic substrate layer and interlayer between the thermal expansion coefficient, shrinkage rate does not match, or a layer of phase transformation, adjust their respective layer, layer thickness, the surface layer to produce appropriate compressive stress, thus inhibiting the occurrence and spread of cracks, the material strength, toughness, surface microhardness increase method.

This kind of layered composite ceramics has strong - strong multilayer interface characteristics, which is usually obtained by interlacing and layer by layer superposition of two kinds of strong monomers or composite ceramics.

Ductile interlayer crack toughening is to use the plastic deformation of ductile layer to consume and absorb energy, and form a bridge at the end of the crack to prevent the crack expansion, so as to improve the fracture toughness of the material. Ductility layer can exist in the state of continuous layer and choose organics such as metal or resin with strong plastic deformation ability.

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