Papers by Keyword: C/C-SiC Composite

Abstract: Because of the excellent fracture toughness and oxidation resistance, carbon fiber reinforced silicon carbide (C/C-SiC or C/SiC) exhibits a sound potential in various application areas such as aerospace technology and high-performance braking systems. For the composite’s reliable design, production, examination, quality assurance and verification, however, the statistical distribution of mechanical properties is of crucial interest and has not been investigated in detail yet. In this work, the strength values of C/C-SiC composite, which was developed via Liquid Silicon Infiltration at the Institute of Structures and Design of German Aerospace Center (DLR), were measured under tensile, bending and compression load. The results were analyzed by normal and Weibull distribution statistics and verified by Kolmogorov–Smirnov-test (KS-test) and Anderson–Darling-test (AD-test). Based on the statistical analysis, the 4PB-strength of C/C-SiC composite can be better described by Weibull distribution. In comparison, normal distribution is more suitable for the compression strength. The influence of different numbers of coupons on the mechanical properties has been identified. A scanning electron microscope (SEM) was employed to analyze the fracture surface, which confirmed that the different statistical distribution of strength values was caused by various failure mechanisms.

Abstract: This article focuses on the development of phenolic resin moulding materials for the production of new carbon fibre-reinforced ceramic composite materials based on C/C-SiC by utilising the LSI (liquid silicon infiltration) production method. The production of these moulding materials is being accomplished by combining phenolic resin and carbon fibres with the addition of a few selected parts of processing aids, during which the influence of the used lubricants on the processability of the moulding materials is examined. The starting materials, microstructures and mechanical properties of the materials were characterised at every step of the entire process (CFRP and C/C composites) as well as the end of the whole production (C/C-SiC composites). During this investigation a link between the portions of the lubricant used, the forming of the porosity and the impact on the mechanical properties was discovered. In regards to the optimisation of the process the involved parties were able to determine an optimal lubricant ratio.

Abstract: C/C-SiC composites were prepared by reactive melt infiltration process at different temperatures. The composition, microstructures and mechanical properties of the composites were investigated. The results showed that infiltration temperature could affect composite’s properties through regulating the chemical composition and interfacial bonding strength of the composites. The C/C-SiC composite prepared at 1650°C exhibited the relatively highest performance with density of 2.24 g·cm^-3 and SiC content of 31.44 vol.%. The flexural strength and the fracture toughness were 238MPa and 10.04 MPa·m^1/2, respectively.

Abstract: The C/C-SiC composites are prepared by the reaction molten infiltration process of silicon powders, using porous C/C composites as preform. C/C composite frameworks with various bulk densities are prepared by the chemical vapor infiltration (CVI) combined with the resin impregnation-pyrolysis methods, using needled-carbon fiber felts as preform. Characterization of the microstructure was conducted with a digital microscope (VHX-500) and a polarized light microscopy, respectively. The hardness (H) and the elastic modulus (E) of the composites are measured using a nano indentor. The results show that the indentation behaviors of the pyrolytic carbon and resin carbon are elastic while silicon and silicon carbide show a plastic deformation behavior. The hardness of the resin carbon as well as the pyrolytic carbon is 2.1GPa and 1.3~1.6GPa, respectively. E of SiC varied from 360 to 259GPa and H from 36 to 21GPa. For Si, the value of E and H are 155-170GPa and 11.7GPa, respectively. The relationship between microstructure and mechanical properties of C/C-SiC composites were analyzed.

Abstract: This study focuses on the conditions of preparation of C/C-SiC composites through polymer infiltration and pyrolysis method using hydrogen-containing polysiloxane as the precursor and divinylbenzene as cross-linking agent. The densities of different C/C composites (ρ=1.02, 1.21, 1.60, 1.78g·cm^-3) increased to 1.24, 1.36, 1.69, 1.84g·cm^-3 respectively after infiltration and pyrolysis four times. The appropriate ratio of hydrogen-containing polysiloxane and divinylbenzene was 1/0.5. The appropriate cross-linking temperature was 250°C. In pyrolysis process, the appropriate increasing rate of pyrolysis temperature should be 50°C/h in the range of 300-800°C. SiC was formed when pyrolysis temperature reached 1550°C.The linear ablation rate and mass ablation rate of C/C-SiC composites were much lower than those of C/C composites.

Abstract: A novel curable liquid polysilane (CLS) containing reactive unsaturated bond and Si-H was synthesized from dichloromethylvinylsilae, methyldichlorosilae and Na in presence of 18-crown-6 under sonication at relatively lower temperature and its structure was characterized by FT-IR, 1H-NMR. The cure behavior of CLS was investigated by DSC,FTIR. Thermal stability of cured CLS was examined by TGA. The results showed that the cured polysilane exhibits good anti-oxidation performance under high temperature. And the sinted CLS exhibited high temperature resistance and good ceramic formability.

Abstract: Porous C/C composite with certain porosity prepared by Chemical vapor infiltration (CVI) was chosen as the preforms to develop the C/C-SiC composites through precursor infiltration and pyrolysis(PIP), using PCS (polycarbosilane) as the precursor and divinylbenzene as solvent and cross-linking reagent for PCS. The effect of the infiltration solution with different PCS/DVB ratio on the final density, microstructure, and mechanical properties of composites was investigated and the proper PCS/DVB ratio to prepare the C/C-SiC composites was suggested. The experimental results showed that the final densities and the mechanical properties of the composites were close related to the PCS/DVB ratio. Higher PCS/DVB ratio resulted in higher final density and better mechanical properties, but not the highest PCS/DVB ratio could get the best mechanical properties. The main reason is that too high PCS/DVB ratio will make the infiltration process become difficult and lead to the formation of lots of pores in the final composite, at last lowers the mechanical properties. It is believed that the 50% PCS content is proper to prepare the C/C-SiC composites. The composite from 50% PCS infiltration solution could get the final density of1.696g/cm3, the flexural strength of 171Mpa, and shearing strength of 21.6Mpa, which are the best mechanical results among the obtained materials.

Abstract: A series of carbon fiber reinforced C-SiC dual matrix composites (C/C-SiC composites) were developed through precursor infiltration of polycarbosilane (PCS) and pyrolysis (PIP), using porous C/C composites with different density from chemical vapor infiltration (CVI) as the preform. The density, mechanical properties, and microstructure of the composites were investigated and the effects of the preform density and the PCS concentration of the infiltration solution on the final density and the mechanical properties of the composites were discussed in detail. The results show that the final density of the C/C-SiC composites prepared at the infiltration concentration of 50% is the highest, indicating that 50% is the proper PCS concentration of the PCS/ Xylene solution to prepare the C/C-SiC composites. The final densities of C/C-SiC composites were closely related to the preform density and the highest final density corresponds to the highest original preform density. For the composites prepared using infiltration solution of 50% PCS, the C/C-SiC composite whose preform density is 1.23 g/cm3 possesses the best mechanical properties while that whose preform density is 1.49 g/cm3 the worst mechanical properties.

Abstract: C/C-SiC composites, namely carbon fiber reinforced silicon carbide and pyrocarbon matrices, were fabricated in two steps in this study. Firstly, C/C composites were prepared by a rapid economical densification process of chemical liquid-vaporized infiltration. PAN based felt and 2-Dimensional carbon fibers were chosen as preform, respectively. A liquid hydrocarbon, kerosene, was used as a precursor. The C/C composites were processed in a temperature range of 900-1100°C for 150 minutes. Subsequently, C/C-SiC composites were fabricated from the C/C composites and silicon powder by reactive melt infiltration method. Densities, open porosities of the C/C and the C/C-SiC composites were investigated. Structural properties of the C/C-SiC composites were studied by optical microscopy. X-ray diffraction was used to identify the element and the crystal phase of the composites. It was shown that the density of C/C composite reached to 1.72 g/cm3 based on the 2D carbon fibers by CLVI method. Microstructure observation of the C/C composite revealed that the pyrocarbon is layer concentric around the fibers. It was found that during the RMI processing β-SiC was formed through the reaction only between liquid silicon and pyrocarbon, while carbon fiber was not damaged. Free silicon remains in the C/C-SiC composites because of insufficient reaction with the pyrocarbon.

Abstract: Two different types of carbon fibre bundles were used for filament winding to obtain C/C preforms. C/C-SiC composites were produced from the C/C preforms by a silicon melt infiltration technique. The effect of the type of carbon fibre bundle on the mechanical and thermal properties of the resultant C/C-SiC composites was compared. The spun fiber preform yields C/C-SiC composites of better mechanical properties than the unidirectional continuous fiber preform. The strength of the composites from the SFP was 1.8 times higher than that from the CFP. The flexural strength and the O-ring strength of the composites from the SFP with a density of 2.35 g/cm3 were about 160 MPa and 170 MPa, respectively.