Mechanical and thermal shock properties of C_f/SiBCN composite: Effect of sintering densification and fiber coating

Abstract

In this work, resin-derived carbon coating was prepared on carbon fibers by polymer impregnation pyrolysis method, then silicoboron carbonitride powder was prepared by mechanical alloying, and finally carbon fiber-reinforced silicoboron carbonitride composites were prepared by hot-pressing process. The effects of sintering densification and fiber coating on microstructure, mechanical properties, thermal shock resistance, and failure mechanisms of the composites were studied. Fiber bridging hinders the sintering densification, causing more defects in fiber-dense area and lower strength. However, higher sintering temperature (1800-2000 • C) can improve mechanical properties significantly, including bending strength, vickers hardness, and elastic module, because further sintering densification enhances matrix strength and fiber/matrix bonding strength, while the change of fracture toughness is not obvious (2.24-2.38 MPa⋅m 1/2 ) due to counteraction of higher debonding resistance and less pull-out length. However, fiber coating improves fracture toughness greatly via protecting carbon fibers from chemical corrosion and damage of thermal stress and external stress. Due to lower coefficient of thermal expansion, lower fiber loading ratio, less stress concentration at the fiber/matrix interface, and better defect healing effect, lower sintering temperature favors thermal shock resistance of composites, and thermal shock recession mechanisms are the damage of interface.

Application of 3D Printing Technology and Porous Nano-Ceramic Decorative Sheet in Interior Landscape Design

“…The traditional method of preparing ceramics is to mix, shape, and sinter various raw material powders to obtain ceramic parts. However, due to the high temperature required for ceramic sintering, the shape, size, and properties are easily affected by the sintering process, and the ceramic itself is brittle and difficult to reprocess after sintering; therefore, some ceramics with high surface quality and precision are difficult to obtain by traditional preparation techniques [ 11 ]. 3D printing technology plays an important role in solving this problem.…”

Effect of material parameters on thermal shock crack of ceramics calculated by phase‐field method

“…where u, T, T 0 , G c , c, and ρ are displacement, temperature, critical energy release rate, reference temperature, specific heat, and density, respectively; ε e = ε−ε T is the elastic strain tensor, where ε and ε T are total strain and thermal strain; 2 + δ is the degradation function, and δ is a parameter chosen to be as small as possible to ensure the problem converges; 𝜓 + 0 (𝜺 𝑒 ) and 𝜓 − 0 (𝜺 𝑒 ) are the tensile and compressive parts of the elastic energy density 23 :…”

“…It is because changing α or E to x times and changing K IC to 1/x times will get the same phase-field evolution Equation (3). For example, when K IC becomes 1/x times, the energy release rate G c becomes 1/x 2 times the original value from 𝐺 𝐶 = 𝐾 2 𝐼𝐶 ∕𝐸, and the strain energy  remains unchanged. That is, G c :  = 1: x 2 .…”

“…Ceramics are extensively used in the aerospace industry instead of metals because of their excellent hightemperature properties. [1][2][3][4] However, due to the brittleness of ceramics, it is easy to fail due to thermal shock when the ambient temperature changes sharply, which is the inherent disadvantage of ceramic materials. 3,4 Due to the complexity of the multi-field coupling fracture in thermal shock, the simulation analysis of fractureinduced failure plays an important role in designing materials or structures.…”

Tailoring layered Csf/SiBCN composites with pseudoplastic fracture behavior: Strengthening and toughening mechanisms

“…Compared with continuous carbon fiber reinforced polymer-derived SiBCN (PDCs-SiBCN) ceramic matrix composites (CMCs), [18][19][20][21] short carbon fibers are more suitable for the reinforcement of SiBCN ceramics prepared by mechanical alloying of mixed powders followed by sintering, 4,22,23 because short carbon fibers can be dispersed into mechanically alloyed SiBCN powders by a special sintering technique to obtain short carbon fiber reinforced mechanically alloyed SiBCN (MA-SiBCN) CMCs, denoted as C sf /SiBCN. [24][25][26][27] Zhu et al 26 fabricated C sf /SiBCN containing Zr by sintering under hot-pressing (HP) conditions at 1900 • C. The fracture surface (FS) showed limited fiber pull-out length due to severe interface reaction at high sintering temperatures, and the flexural strength decreased compared with the pure ceramics because of agglomeration and degradation of the carbon fibers. Niu et al 25 also adopted a similar method to obtain C sf /SiBCN and the results showed that many defects, such as pores and cracks, were formed due to uneven dispersion of the short fibers in the matrix as well as due to severe degradation of the fibers caused by interface reaction at high sintering temperatures.…”