“…Besides, during the preparation process, the oxidation of BN interfacial layer starts at a temperature of 800°C and remains passivated during the oxidation process, so that a protective condensed oxide B 2 O 3 can be formed to repair the cracks. 37,38 Figure 6.Pore distribution in SiC f /SiC composites extracted by Micro-CT (a–b) P/S-SiC f /SiC PCS ; (b–c) P/S-SiC f /SiC VHPCS ; (e–f) B/S-SiC f /SiC PCS ; (g–h) B/S-SiC f /SiC VHPCS .…”
Section: Resultsmentioning
confidence: 99%
“…Besides, during the preparation process, the oxidation of BN interfacial layer starts at a temperature of 800°C and remains passivated during the oxidation process, so that a protective condensed oxide B 2 O 3 can be formed to repair the cracks. 37,38 When preparing the composites with PCS matrix, a large number of small molecules escape from PCS during the cracking process. Forming a porous foam-like matrix, this results in higher porosity in the specimens with PCS matrix.…”
Section: Porosity Characteristics Of 25d Woven Sic F / Sic Compositesmentioning
This paper presents the effects of matrix and interface on the fracture toughness and progressive damage mechanisms of 2.5D woven SiCf/SiC composites. Third-generation SiC fibers were selected. 2.5D woven SiCf/SiC composites with four interfacial layers PyC, PyC/SiC, BN, BN/SiC and two matrix polycarbosilane (PCS) and liquid hyperbranched polycarbosilane with vinyl groups (VHPCS) were prepared by a combination of chemical vapour deposition (CVD), chemical vapor infiltration (CVI), and precursor infiltration pyrolysis (PIP) processes, respectively. Single edge notch bending (SENB) tests were carried out to investigate the fracture toughness. Moreover, acoustic emission (AE) and X-ray micro-computed tomography (Micro-CT) techniques were employed to analyze the progressive mechanical properties and failure mechanism. Results showed that the matrix and interface have significant effects on the fracture toughness. Moreover, 2.5D woven composites with PyC/SiC interfacial layers and VHPCS matrix have the highest fracture toughness (16.93 ± 1.20 Mpa • m1/2). Furthermore, during progressive damage, the pores can influence the crack expansion path, and effectively regulate the stress concentration and increase the toughness of the composites.
“…Besides, during the preparation process, the oxidation of BN interfacial layer starts at a temperature of 800°C and remains passivated during the oxidation process, so that a protective condensed oxide B 2 O 3 can be formed to repair the cracks. 37,38 Figure 6.Pore distribution in SiC f /SiC composites extracted by Micro-CT (a–b) P/S-SiC f /SiC PCS ; (b–c) P/S-SiC f /SiC VHPCS ; (e–f) B/S-SiC f /SiC PCS ; (g–h) B/S-SiC f /SiC VHPCS .…”
Section: Resultsmentioning
confidence: 99%
“…Besides, during the preparation process, the oxidation of BN interfacial layer starts at a temperature of 800°C and remains passivated during the oxidation process, so that a protective condensed oxide B 2 O 3 can be formed to repair the cracks. 37,38 When preparing the composites with PCS matrix, a large number of small molecules escape from PCS during the cracking process. Forming a porous foam-like matrix, this results in higher porosity in the specimens with PCS matrix.…”
Section: Porosity Characteristics Of 25d Woven Sic F / Sic Compositesmentioning
This paper presents the effects of matrix and interface on the fracture toughness and progressive damage mechanisms of 2.5D woven SiCf/SiC composites. Third-generation SiC fibers were selected. 2.5D woven SiCf/SiC composites with four interfacial layers PyC, PyC/SiC, BN, BN/SiC and two matrix polycarbosilane (PCS) and liquid hyperbranched polycarbosilane with vinyl groups (VHPCS) were prepared by a combination of chemical vapour deposition (CVD), chemical vapor infiltration (CVI), and precursor infiltration pyrolysis (PIP) processes, respectively. Single edge notch bending (SENB) tests were carried out to investigate the fracture toughness. Moreover, acoustic emission (AE) and X-ray micro-computed tomography (Micro-CT) techniques were employed to analyze the progressive mechanical properties and failure mechanism. Results showed that the matrix and interface have significant effects on the fracture toughness. Moreover, 2.5D woven composites with PyC/SiC interfacial layers and VHPCS matrix have the highest fracture toughness (16.93 ± 1.20 Mpa • m1/2). Furthermore, during progressive damage, the pores can influence the crack expansion path, and effectively regulate the stress concentration and increase the toughness of the composites.
“…Similarly, if the bonding strength of the interface is too low, the matrix cannot transfer the external load to the ceramic fiber through the interface, which is challenging to play the role of strengthening. In recent years, the interfacial layer systems used for the preparation of composite materials mainly fall into the following three categories: Pyrolytic carbon (PyC) interfacial layer 19–22 : PyC interfacial layer has a typical layered structure, which is conducive to multiple deflections of cracks in the interfacial layer and expansion of crack diffusion path and plays a role in stress release and toughness enhancement. PyC is the most common interfacial layer system in ceramic matrix composites due to its advantages of stable interlayer structure and simple preparation process.…”
Section: Introductionmentioning
confidence: 99%
“…(1) Pyrolytic carbon (PyC) interfacial layer [19][20][21][22] : PyC interfacial layer has a typical layered structure, which is conducive to multiple deflections of cracks in the interfacial layer and expansion of crack diffusion path and plays a role in stress release and toughness enhancement. PyC is the most common interfacial layer system in ceramic matrix composites due to its advantages of stable interlayer structure and simple preparation process.…”
Boron nitride (BN) interfacial layer with controlled thickness and structure was prepared on the surface of near stoichiometric ratio SiC fiber preforms by a chemical vapor deposition process, and the SiC/SiC composites were obtained by polymer precursor infiltration and pyrolysis process. The microstructure of the BN interfacial layer and SiC/SiC composites was tested by scanning electron microscopy, and the mechanical behavior of SiC/SiC composites was characterized by a mechanical properties test. Results showed that BN interfacial layer was evenly distributed in the fiber preforms with excellent thickness consistency. As the thickness of the BN interfacial layer increased, the deflection path of the crack increased gradually, resulting in the flexural strength first increasing and then decreasing. The mechanical behavior mentioned above was mainly attributed to the dual effects of load transfer and crack propagation of the BN interfacial layer; that was, the crack propagation of ceramic matrix under external load lengthened the path of load transfer and formed a large number of fibers bridging and pulling out successively, which contributed to the energy dissipation mechanism.
“…Investigations of improvements in the properties of C/SiBCN composites after high-temperature treatment should focus on the interphase between carbon fibers and the matrix, because this interphase has a greatly influence on the properties of the composites [10]. Carbon fibers are typically coated with C [13,14], SiC [8,15], BN [16,17], etc as the interphase. The most common coating for optimizing the interphase are pyrocarbon (PyC).…”
C/SiBCN composites are expected to have widespread application in aerospace applications due to the excellent high-temperature stability. However, the interfacial reactions between the carbon fibers and the SiBCN matrix at high temperatures have significantly limited the practical application of these composites in the aerospace field. In this paper, different thicknesses of pyrocarbon (PyC) interphase (0.1 μm, 0.25 μm, and 0.5 μm) were introduced by chemical vapor deposition (CVD) process. The interface bonding of C/SiBCN composites with 0.1 μm and 0.25 μm interphase was relatively weak and the composites with 0.5 μm interphase exhibited strong interface bonding strength. After heat treatment at 1600 °C, the mechanical properties of the C/SiBCN composites with the 0.5-μm-thick interphase was maintained at 131 MPa, and at 105 MPa even after heat treatment at 1900 °C, which indicated their excellent high-temperature mechanical properties. In short, 0.5-μm-thick PyC interphase can effectively improve the interfacial reaction of the C/SiBCN composites, which contributed to the application of the composites in high temperature environment.
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