Carbon Fiber Reinforced Silicon Carbide Research Articles

High-precision CTE measurement of hybrid C/SiC composite for cryogenic space telescopes

This paper presents highly precise measurements of thermal expansion of a “hybrid” carbon-fiber reinforced silicon carbide composite, HB-Cesic® – a trademark of ECM, in the temperature region of ∼310–10 K. Whilst C/SiC composites have been considered to be promising for the mirrors and other structures of space-borne cryogenic telescopes, the anisotropic thermal expansion has been a potential disadvantage of this material. HB-Cesic® is a newly developed composite using a mixture of different types of chopped, short carbon-fiber, in which one of the important aims of the development was to reduce the anisotropy. The measurements indicate that the anisotropy was much reduced down to 4% as a result of hybridization. The thermal expansion data obtained are presented as functions of temperature using eighth-order polynomials separately for the horizontal ( XY-) and vertical ( Z-) directions of the fabrication process. The average CTEs and their dispersion (1 σ) in the range 293–10 K derived from the data for the XY- and Z-directions were 0.805 ± 0.003 × 10 −6 K −1 and 0.837 ± 0.001 × 10 −6 K −1, respectively. The absolute accuracy and the reproducibility of the present measurements are suggested to be better than 0.01 × 10 −6 K −1 and 0.001 × 10 −6 K −1, respectively. The residual anisotropy of the thermal expansion was consistent with our previous speculation regarding carbon-fiber, in which the residual anisotropy tended to lie mainly in the horizontal plane.

Reaction Sintering of Carbon Fiber Reinforced Silicon Carbide Composite by Gel-Casting Method with Water Soluble Epoxy Resin as Gel Former

Reaction-bonding sintering silicon carbide (RB-SiC) toughened by 10vol% short carbon fibers were produced by Gel-casting method using water soluble epoxy as gel former and then reaction sintering at 1750°C under vacuum atmosphere for 2 h . SEM showed that short carbon fibers could disperse uniformly in the preforms and sintered carbon fiber reinforced silicon carbide composites (Cf/SiC). The mechanical test results showed that the strength decrease from 286 MPa for RB-SiC to 231 MPa for Cf/SiC, however, the fracture toughness of Cf/SiC increased from 3.65 MPa m1/2 to 5.28 MPa m1/2 compared with RB-SiC. The strength decrease of the Cf/SiC should be ascribed to the chemical reaction between the addition of short fibers and matrix, and the increase of the fracture toughness could be attributed to fiber debonding, fiber pull-out and crack deflection .

Damage Mechanism of Short Carbon Fiber Reinforced SiC-Based Composite

Short carbon fiber reinforced silicon carbide (SiC)composites were prepared with boron (B) and carbon (C) as sintering additives via pressureless sintering at 2150°C. The damage mechanism of fiber was investigated as following: (1) The carbon fiber was seriously physically damaged in the process of material mixing; (2) The chemical damage of the carbon fiber was happened in the reaction with matrix as the high sintering temperature; (3) Numerous cavities exist between the carbon fiber and the matrix leads to the weak interfacial strength.

서로 다른 밀도를 갖는 탄소섬유강화 탄화규소 복합재료의 압흔응력에 의한 기계적 거동

In this study, we investigated the mechanical behavior of carbon fiber reinforced silicon carbide composites by indentation stress. Relatively porous and dense fiber reinforced ceramic composites were fabricated by liquid silicon infiltration (LSI) process. Densification of fiber composite was controlled by hardening temperature of preform and consecutive LSI process. Load-displacement curves were obtained during indentation of WC sphere on the carbon fiber reinforced silicon carbide composites. The indentation damages at various loads were observed, and the elastic modulus were predicted from unloading curve of load-displacement curve.

Effect of PyC Content in C/C Greenbody on Structure and Properties of 3D-C/SiC Composite Fabricated by Gas Silicon Infiltration

In order to fabricate high perform carbon fiber reinforced silicon carbide matrix composite (C/SiC). SiC interphase of three dimensional(3D) braided carbon fiber performs was prepared by polymer infiltration pyrolysis(PIP) using polycarbosilane(PCS) as precursor. Then, C/SiC composites were fabricated by gas silicon infiltration(GSI) at 1400～1700°C to C/C greenbody, which was prepared by PIP based on precursor of phenolic resin from one to four cycles. The influence of pyrocarbon(PyC) content in C/C greenbody on the composition, microstructure and mechanical properties of C/SiC composites was investigated via X-ray diffraction(XRD), scanning electron microscope (SEM), physical and chemical methods. The results indicate that there were β-SiC, residual Si ,C and closed pores in C/SiC, and the different pyrocarbon(PyC) content influenced C/SiC mechanical properties via the variable content of β-SiC, residual Si, C and closed pores. The C/SiC composites with 2 cycles of PIP-C, which had fitting relative content of β-SiC, residual Si and C, possessed the best mechanical properties. The flexure strength and flexure modulus were 187.3MPa and 66.5GPa. The β-SiC generated from PCS wrapped the carbon fiber bundles, protecting them from reacting with gaseous silicon. The phenomenon of ‘fibers pull-out’ was observed in all four groups of C/SiC composites, which manifested the mechanism of toughness fracture.

The Machinability of 3D-C/SiC Composites

Carbon fiber reinforced silicon carbide (C/SiC) composites are considered as one of the most potential thermal structure materials. However, the non-machinability of the three dimension woven fabric restrict the wide application of the c/sic composites. In this paper, we discuss the effect of machinability on the properties of 3D-c/sic composites, such as the modulus, mechanical properties, and so on. The results show that c/sic composites exhibit excellent mechanical properties after machinability, an extensive microstructure study is also carried out to understand the properties of the composites.

A Database for Material Design of C/SiC Composites

Continuous carbon fiber reinforced silicon carbide composite material (C/SiC) is one of the most effective candidate materials for hot structures in aeronautic and aerospace applications. Its performances in the complicated service environments are widely concerned. A database, aiming at optimized design of C/SiC, was developed. The database collected original data on the fabrication, microstructure of C/SiC, as well as abundant data on performance experiments including tension, compression, shear, fatigue, creep, oxidation, high-temperature fatigue, and so on. The logic structure of the database, modeled by unified modeling language, provides a data link that connecting the processing, microstructure and performance of C/SiC, so that users can conveniently create a test result set to build the mathematical model of material design. Efficient software was developed to realize management, browsing and extension of the database.

Fabrication and Properties of Cf/SiC Composites Derived from Polysiloxane Precursor

Carbon fiber reinforced silicon carbide composites (Cf/SiC) were derived through precursor infiltration pyrolysis route (PIP) at 1600°C in vacuum atmosphere using polysiloxane as precursor. The matrix of Cf/SiC was characterized by X-ray diffraction and elemental analysis. The results show that crystalline β-SiC can be derived at 1600°C in vacuum from polysiloxane. The flexural strength and fracture toughness of polysiloxane derived from Cf/SiC can reach up to 70 MPa and 2.3MPa·m respectively1/2.

Dynamic tensile behavior of two-dimensional carbon fiber reinforced silicon carbide matrix composites

An investigation has been undertaken to determine the dynamic and quasi-static tensile behavior of two-dimensional carbon fiber reinforced silicon carbide matrix (2D-C/SiC) composites by means of the split Hopkinson tension bar and an electronic universal test machine respectively. The results indicate that the tensile strength of 2D C/SiC composites is increased at high strain rate. Furthermore, coated specimens show not only a 15% improvement in tensile strength but heightened strain rate sensitivity compared with uncoated ones. It is also shown that the tensile failure strain is strain rate insensitive and remains around 0.4%. Optical macrograph of failed specimens under dynamic loading revealed jagged fracture surfaces characterized by delamination and crack deviation, together with obvious fiber pull-out/splitting, in contrast with the smooth fracture surfaces under quasi-static loading. Scanning electron microscopy micrograph of fracture surface under dynamic loading clearly displayed integrated bundle pull-out which implies suppressed in-bundle debonding and enhanced in-bundle interfacial strengthening, in contrast with extensive in-bundle debonding under quasi-static loading. Thus we conclude that, with 2D C/SiC composites, the strain rate sensitivity of in-bundle interface is mainly responsible for the strain rate sensitivity of the tensile strength.

Failure and strength of 2D-C/SiC composite under in-plane shear loading at elevated temperatures

In-plane shear strength (IPSS) of a two-dimensional carbon fiber reinforced silicon carbide composite (C/SiC) was measured by compression of double-notched specimens (DNS) from room temperature to 1873 K. The result indicates that the compression of DNS is an effective method to measure IPSS of C/SiC. A significant dependence of IPSS on temperature was found for C/SiC. IPSS increases with increasing temperature up to 1273 K, and then decreases when the temperature was higher. The main failure modes under the shear loading contain matrix cracking, delamination and pullout of fibers and fiber bundles.

Properties of carbon nano-tubes–C f/SiC composite by precursor infiltration and pyrolysis process

Carbon nanotubes (CNTs) were introduced into the precursor infiltration and pyrolysis (PIP) carbon fiber reinforced silicon carbide matrix (C f/SiC) composite via the infiltration slurry. The weight fraction of CNTs in the composite was 0.765‰. The fiber–matrix interface coating was prepared through chemical vapor deposition (CVD) process using methyltrichlorosilane (MTS). Effects of the CNTs on mechanical and thermal properties of the composite were evaluated by three-point bending test, single-edge notched beam (SENB) test, and laser flash method. Attributed to the introduction of the small quantity of CNTs, flexural strength and fracture toughness of the C f/SiC composite both increased by 25%, and thermal conductivity at room temperature increased by 30%.

Damage Mechanism of Plain Weave C/SiC Composites Subjected to Quasi-Static Indentation Loading

Quasi-static indentation (QSI) tests on plain weave carbon fiber reinforced silicon carbide (C/SiC) ceramic matrix composites (CMC) have been performed to study the damage evolution law and damage modes. Acoustic emission (AE) and Ultrasonic C-scan techniques are creatively used to monitor the damage process and detect the indented damage, respectively. The damage development process could be described by three evidently different stages: initial crack tips spreading along within the matrix, matrix cracking and delamination as well as fiber bundles breakage of different layers. The AE activity indicated that the main damage modes are matrix cracking and delamination in the first two stages, once the pressing force exceeds the peak load the damage mode will change into fiber bundles breakage. Moreover, the damage procured in the QSI test is slightly lower than that produced in the low velocity impact (LVI) test under the equivalent energy, the correspondence between the two test methods is reasonably good.

ZrC-Zr<sub>2</sub>Si Coating on Carbon Fiber Reinforced Silicon Carbide Matrix Composites Prepared by Pack Cementation Method

ZrC-Zr2Si coating was prepared on carbon fiber reinforced silicon carbide matrix composites (C/SiC) by pack cementation method to prevent these composites from oxidation. SEM, EDS and XRD were applied to analyze the surface and cross-section morphologies, element distribution and phase composition of the coating, respectively. The results show that the coating made by the technique exhibits excellent oxidation resistance. The optimizing infiltration composition and process was: 60wt.%Zr-Si, 30wt.%PCS-DVB, 10wt.%Al2O3, holding 8 hours at 1400°C in Ar protecting atmosphere, ZrC-Zr2Si coating is obtained, homogeneous and density. The weight loss percentage of the coated C/SiC is only 1.52％after oxidation in air at 1500°Cfor 30min.

Effects of high-temperature annealing on the microstructures and mechanical properties of C f/SiC composites using polycarbosilane

Three-dimensional carbon fiber reinforced silicon carbide (3D C f/SiC) composites were fabricated by precursor infiltration and pyrolysis with polycarbosilane as the matrix precursor, and effects of high-temperature annealing on the microstructures and mechanical properties of the C f/SiC composites were investigated. It was found that the high-temperature annealing had a great effect on the mechanical properties of C f/SiC composites. When the annealing time was 1 h, the flexural strength of C f/SiC composites gradually decreased with the elevation of annealing temperature, but the flexural modulus slightly changed within the range of 44.9–50.7 GPa; and the brittle fracture behavior was shown after 1700 °C annealing. When the annealing temperature was 1600 °C, the flexural strength of C f/SiC composites decreased with the increasing annealing time, but the flexural modulus kept around 46 GPa; and the brittle fracture behavior appeared after 5 h annealing.

Investigation of effect of siliconization conditions on mechanical properties of 3D-stitched C–SiC composites

Three-directional carbon fiber reinforced silicon carbide composites were fabricated using liquid silicon infiltration. Siliconization was carried out at nine different conditions to achieve best mechanical properties. Flexural strength, tensile strength and fracture toughness of the composites were determined at each condition. Flexural and tensile strengths increase with siliconization time and temperature. At 1650°C and 120min mechanical properties are found to be the best. Arithmetic mean average flexural and tensile strength values were found to be 177 and 90MPa, respectively. The flexural strength data were also analyzed by the Weibull modulus approach; it was found to be the highest (13.28) for composites siliconized at 1550°C, 120min and the least (7.01) at 1450°C, 10min. The fracture toughness of the composite blocks was found be in the range 5–6 MPam. The strength data were also correlated with chemical composition of the composites and the microstructure obtained during processing.

Creep Behaviors of 3D C/SiC in High Speed Combustion Gas at 1300°C

To understand the creep damage mechanism of a standard 3D Carbon fiber reinforced silicon carbide composite (C/SiC) in high temperature combustion gas at 1300 °C, the creep tests were carried out in a combustion wind tunnel and the mechanisms were investigated by the extension of specimens and the microstructure of fracture section. It was found that the external tensile load was bore by the carbon fibers in the active region during the stressed oxidation process. The oxidation mechanisms of the active region were determined by a normalized threshold stress. Below the normalized threshold stress, the oxidation was controlled by internal diffusion of oxidizing gases through microcracks in SiC matrix. Above the normalized threshold stress, the oxidation was controlled by the reaction of carbon fiber with oxygen and water vapor.

Polymer‐Derived SiOC–barium–strontium aluminosilicate Coatings as an Environmental Barrier for C/SiC Composites

Polysiloxanes polymer coatings were formed on carbon fiber‐reinforced silicon carbide (C/SiC) composites at 100°C in air with barium–strontium aluminosilicate (BSAS) as fillers. After the polymeric coatings were pyrolyzed at 1350°C under argon, a dense SiOC–BSAS‐coated C/SiC composite was obtained. The oxidation test in dry air and the corrosion test in water vapor were carried out on the coated composites at 1250°C, respectively. The results indicated that the polymer‐derived SiOC–BSAS coatings could protect the C/SiC composites well both in dry air and water vapor. Even after corroded for 200 h in water vapor, the coated C/SiC composites showed little weight loss and high residual flexural strength.

Cryogenic optical testing of an 800mm lightweight C/SiC composite mirror mounted on a C/SiC optical bench

We tested the optical performance at cryogenic temperatures of an 800 mm diameter lightweight mirror, consisting of carbon-fiber reinforced silicon carbide and with a mass of 11.2 kg. The ceramic composite of the mirror was HB-Cesic, developed by ECM, Germany, and Mitsubishi Electric Corporation, Japan. The test was carried out while the mirror was mounted, via Invar stress relief supports, on a lightweight optical bench also made of HB-Cesic. During the test, both the mirror and the optical bench were cooled to 18 K in a liquid-helium chamber. The test consisted of measuring the mirror's change of surface figure with an interferometer installed outside the cryo-chamber. The cryogenic deformation of the mirror was 110 nm RMS with no significant residual deformation after cooling, which is very promising for the applicability of the HB-Cesic composite to large lightweight cryogenic space optics.

Progressive Damage Approach to Simulating Low Velocity Impact Response of Plain Weave C/SiC Composites

Based on progressive damage theory, a 3D laminated model with an orthotropic property in plane was established to simulate the response of plain weave carbon fiber reinforced silicon carbide(C/SiC) ceramic matrix composites(CMC) under low velocity impact(LVI). Intra-layer damage and inter-layer damage were taken into account, respectively. Three scalar damage variables, associated with the degradation of warp modulus, weft modulus and shear modulus, respectively, were proposed to characterize intra-layer damage evolutions. The intra-layer constitutive model was implemented into MSC.Dytran, via its user subroutine EXFAIL1. The potential delamination region was considered as a discrete cohesive zone. Three vector spring elements were placed into every two adjacent nodes to simulate the inter-layer joints. A scalar damage variables, associated with the degradation of the three vector spring elements, were brought forward to characterize the inter-layer damage evolutions. The inter-layer constitutive model was implemented into MSC.Dytran, via its user subroutine EXELAS. Damage area, indentation depth of C/SiC composite plates and time history of impact force were obtained to compare with experimental results. The numerical results show overall good agreement with experimental results.

High-temperature tensile properties and oxidation behavior of carbon fiber reinforced silicon carbide bolts in a simulated re-entry environment

The tensile properties and oxidation behavior of 2D C/SiC bolts prepared by chemical vapor infiltration were investigated in a simulated re-entry environment. The results showed that all the tensile strengths of 2D C/SiC bolts at test temperatures of 1300, 1600 and 1800 °C decreased, respectively, retaining 85%, 92%, and 94% of the virgin properties at room temperature. The tensile strengths and times to failure of 2D C/SiC bolts slightly increased with increase of test temperature from 1300 to 1800 °C. Microstructural observations indicated that the C/SiC bolts at lower temperature of 1300 °C were more susceptible to the reaction-controlled oxidation with the blunt fiber ends than those at high temperature of 1800 °C, which resulting in turn in great mechanical degradation and severe oxidation.