Dissertation > Industrial Technology > General industrial technology > Materials science and engineering > Composite materials > Non-metallic composite materials

Processing of SiC_f /SiC Composites Prepared with LPVCS as Precursor Polymer

Author WangFei
Tutor ZhouXinGui
School National University of Defense Science and Technology
Course Materials Science and Engineering
Keywords SiC_f / SiC Composites Liquid precursor Molded Interface layer Mechanical Properties
Type Master's thesis
Year 2011
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Continuous SiC fiber-reinforced SiC matrix composites (SiC f / SiC) because it has a low density, high strength, high modulus, impact resistance, high temperature and good oxidation resistance and other characteristics, has become one of the structural materials of the most promising high-temperature heat, has a broad application prospects in the field of aerospace. PRECURSOR INFILTRATION cracking process (PIP) is a commonly used SiC f / SiC composites process, using the technology pioneer selection of directly determine the material preparation cycle products porosity size, thereby affecting the performance of the composite. In addition, the fiber - matrix interface has a vital role in improving the composite performance, optimize improve the SiC f / SiC composites mechanical properties of one of the important means of interface. This selection of a liquid containing active Si-H and-CH = CH 2 group of Precursor LPVCS as raw materials, enhance the body select domestic KD-I-type SiC fibers. SiC fibers prepared on the surface of the cleavage of carbon (PyC) coatings by CVD process, the use of the coated fiber preparation SiC f / SiC composites molding the molding process, auxiliary materials taken in the process of cross-linking. The combined impact on the mechanical properties of composites, the analysis and characterization of the microstructure to study the types of precursor, the molding process, as well as the interface layer the SiC f / SiC composite performance. The study showed that: PRECURSOR LPVCS for only 10 cycles to complete SiC f / SiC composites materials prepared opening rate of 5.12%, and the density of 2.11g/cm3; with PCS as a Precursor for 14 cycles required to complete the preparation of the material obtained the SiC f / SiC composites opening rate of 8.80%, and the density of 1.97g/cm3. Therefore, the pioneer body LPVCS the use can effectively improve the material density, reduce production cost. To the LPVCS as a pioneer preparation SiC f / SiC composites, the cross-linking process used in the molding process reduce composites cycle to 9 cycles, while the fiber volume fraction from 40% increased to 50% Preparation of a composite material obtained above density 2.11g/cm3. In addition, the magnitude of the pressure of the molding process and the molding time will also affect the performance of the composite material, through the analysis of the determined optimum molding process: braid member Precursor LPVCS crosslinking starts applying pressure, the temperature was raised immediately after the end of the crosslinked relief The molding pressure control between 1MPa 5 MPa molding time of about five hours. PyC coating, carbon nanotube interface layer and two composite interface layer can play a buffer role in the molding process, avoid fiber damage due to mutual compression; PyC coating on composite interface layer found fiber - matrix interface improvement the best, to achieve enhanced toughening of the composite molding process combined prepared by SiC f / SiC composites flexural strength of 657.88MPa, fracture toughness 26.80MPa The / m 1/2 , the elastic modulus 94.30GPa.

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