Carbon Fiber-reinforced Silicon Carbide Composites Research Articles

Additive manufacturing of continuous carbon fiber-reinforced silicon carbide composite by fused filament fabrication and precursor infiltration pyrolysis

Continuous fiber reinforced silicon carbide composites (Cf/SiC) are known for their advantages such as high strength, high modulus, high thermal conductivity, and low density. In this paper, we propose an integrated Cf/SiC preparation and processing process. The continuous carbon fiber-reinforced resin matrix composite green parts were processed by fused filament fabrication, and then ceramicized by precursor infiltration pyrolysis process. The processing parameters of the green parts, the performance of the green-part specimens, the phase evolution in the post treatment, and the performance of Cf/SiC samples were investigated. The infill line distance (ILD) had a huge influence on the mechanical properties of green parts and Cf/SiC. The bending strength of the green parts and the Cf/SiC specimens increased with the decrease in ILD. The maximum bending strength of 169.48 MPa and 155.83 MPa was achieved for the carbon fiber/polyethylene terephthalate glycol (Cf/PETG) and polylactic acid (Cf/PLA) green parts, respectively. The highest bending strength of 47.73 MPa of the Cf/SiC material was obtained with the Cf/PLA green parts, while the bending strength of 93.79 MPa was obtained for the Cf/SiC with Cf/PETG green parts. The increase in mechanical properties was believed to result from the pyrolyzed carbon brought by PETG and the increase of the equivalent fiber density within the single layer after a larger nozzle size was used.

Transition of in-plane compressive strength and failure mechanism of 2D-C/SiC: Influence of off-axis loading angle and loading rate

In this study, the in-plane compressive behavior of two-dimensional plain-woven carbon fiber-reinforced silicon carbide composite (2D-C/SiC) was investigated using on- and off-axis compression experiments under both quasi-static and dynamic loading conditions. The failure mechanisms were elucidated through in-situ observations and microanalysis-based methods. As the loading angle increased from 0 to 45°, stress–strain curves exhibited stronger nonlinearity, and the in-plane compressive strength decreased by 50.2% and 41.1% under quasi-static and dynamic loading conditions, respectively. The failure mechanism shifted from fiber-dominant to interface- and matrix-dominant as the loading angle increased, which was responsible for the strength degradation and intensified nonlinearity in curves. A positive strain rate effect on the in-plane compressive strength attributed to the interface enhancement and multiple crack propagation was identified. Additionally, owing to the competition between the dynamic strengthening and damage aggravation effects, the strain-rate sensitivity factors increased with the loading angle up to 30° and then decreased at 45°.

Experimental investigation on interlaminar and in-plane shear damage evolution of 2D C/SiC composites using acoustic emission and X-ray computed microtomography

Carbon fiber-reinforced silicon carbide composites (C/SiC) are widely used in lightweight aerospace structures for thermal protection due to its excellent mechanical properties. The low interfacial shear strength of the composites decreases its performance and limits its application. To investigate the shearing performance of C/SiC composite, interlaminar shear and in-plane shear tests were conducted. Real-time X-ray micro-computed tomography (XCT) non-destructive testing technology is an effective method for damage analysis of composite materials. The damage mechanisms of 2D plain weave C/SiC composites prepared by chemical vapor infiltration process under interlaminar shear loading are investigated using the combination of XCT and acoustic emission detection system. The in-situ XCT results reveal the damage visualization mechanisms of the composites and the damage evolution process including matrix damage, interfacial debonding and fiber fracture. The failure mechanisms and morphology of the shear effect for 2D plain weave C/SiC were analysed.

Size effect of carbon fiber-reinforced silicon carbide composites (C/C-SiC): Part 2 - tensile testing with alignment device

The appropriate assessment of mechanical properties is essential to design ceramic matrix composites. The size effect of strength plays a key role for the material understanding and the transfer from lab-scale samples to components. In order to investigate the size effect for carbon fiber-reinforced silicon carbon (C/C-SiC) under tensile load, a tensile testing with a minimum of deviation from the pure tensile loading is necessary. Hence, a hybrid edge/face-loading test device for self-alignment and centering of C/C-SiC tensile samples was developed, evaluated and proved to ensure pure tensile load. The mechanical analysis of more than 190 samples with two different cross-sections fabricated from the same material population revealed no significant difference in tensile strength. Although the volume under load was increased from 129 to 154 mm3, the tensile strengths of 162 ± 7 and 164 ± 6 MPa did not change. These results are discussed regarding the weakest link and energetic size effect approaches.

Design and material selection of optomechanical systems for the extreme environment on Mars

Mars surface composition detector (MarSCoDe) is a scientific instrument suite onboard the Mars rover of the “Tianwen-1” mission, which uses laser-induced breakdown spectroscopy and shortwave infrared spectroscopy to detect the composition of soils and rocks at the surface of Mars. The optical head unit (OHU) is the core hardware of MarSCoDe, containing a Cassegrain telescope and other optical modules for lasers generation and signals transmission. The unit lacks thermal control resources and is located outside the rover’s cabin, which will directly face the Martian surface drastic temperature changes. We introduce the optomechanical designs that realize the lightweight and high thermal stability of the OHU optical system, especially the designs and implementations of the semiopen primary mirror based on silicon carbide and the fully closed optical bench based on carbon fiber-reinforced polymer. Meanwhile, the advantages and difficulties of silicon carbide, long carbon fiber-reinforced silicon carbide composites, and carbon fiber-reinforced polymer materials used for small and compact optomechanical systems are discussed. Subsequently, the environmental adaptability of the telescope system of OHU was studied through analytical and experimental methods, which show that it can achieve the required optical performance over a temperature range of approximately 100°C.

Size effect of carbon fiber-reinforced silicon carbide composites (C/C-SiC): Part 1 – bending load and statistical effects

This study analyzed the influence of the sample volume, number of tested specimen, and testing method on the flexural strength of fabric-reinforced ceramic matrix composites. For this purpose, seven different batches of C/C-SiC were prepared with four different sample thicknesses to determine the flexural strengths and Weibull moduli by three- and four-point flexural tests. The result showed that C/C-SiC exhibits a size effect of strength under bending load because a decrease of measured flexural strength with increased specimen size was observed. This size effect was discussed regarding the Weibull weakest link approach and the concept of quasi-brittle materials.The determined Weibull moduli were comparable for the same load condition but dissimilar for the identical material if the load condition were changed from three- to four-point bending. Hence, the Weibull modulus was found to be not an inherent material constant for C/C-SiC and the Weibull weakest link approach seems not appropriate.

2D exhaust nozzle with multiple composite layers for IR signature suppression

The IR (Infrared) signature generated from hot sections of the aircraft increases potential to be traced by IR detection system and severely reduces aircraft survivability during the mission. Main sources of IR signature are high temperature parts of the aircraft and the engine such as exhaust nozzle, jet pipe, rear-fuselage, and exhaust gas plume above 400 °C, and they generate detectable 3 to 5 um wavelength IR signature. The novel 2D engine exhaust nozzle with multiple composite layers is proposed to suppress high temperature IR signature from behind, in this study. The 2D exhaust nozzle with ellipse-shaped cross-sections with high aspect ratios can disperse high temperature core gas flow, and can enhance mixing performance with bypass air flow. Thus, this reduces the exhaust gas plume temperature and masks the engine hot sections from behind. In order to suppress high temperature IR signature from the nozzle surface, this study constructs a ceramic insulator between the outermost surface layer and the innermost surface layer. The innermost surface layer is constituted by C-SiC (carbon fiber reinforced silicon carbide composite) with excellent erosion performance for high speed and high temperature gas above 1400 °C, and the outermost layer is formed of CFRP (Carbon Fiber Reinforced Plastic) that can maintain structural strength even with the axial thrust and inner pressure. In this study, the 2D-shape C-SiC nozzle was fabricated through melting Si infiltration process, and the nozzle was completed by stacking ceramic insulator and CFRP above it. The engine application test confirmed that the outermost temperature of the proposed exhaust nozzle was kept below 100 °C, and the IR signature was also reduced by 20% compared to the coaxial exhaust nozzle. The 2D exhaust nozzle proposed in this study can be applied to aircraft that requires stealth capability through structural optimization in the future works.

X-ray tomography applied to the void/defect measurement of hybrid CFRC/SiC composites

Carbon fiber reinforced carbon composites (CFRC) and carbon fiber reinforced silicon carbide composites (CFRC/SiC) are materials of wide interest in the aerospace industry due mainly to their outstanding thermo-mechanical properties at high temperature. The control of the process of obtaining these composites, carried out non-destructive processes, such as x-ray tomography, are of great interest to the industry, since they are able to present not only information concerning density and porosity, but also 3D vision with identification of closed and open pores, as well as a precise location of these defects in the sample. In this study a CFRC/SiC hybrid matrix composite obtained by employing carbon-silicon reaction by direct impregnation of silicon powder and phenolic resin, followed by heat treatment at 1600 °C under inert atmosphere is monitored step by step, in its preparation stages, using x-ray computed tomography techniques compared with optical microscopy techniques to detect voids in its microstructure. The three methods presented were satisfactory for structural analysis of the steps of obtaining the CFRC/SiC composite, considering the resolution and sample preparation restrictions applied to each of them, under the working conditions described in this study.

Research Progress on Joining of C<sub>f</sub>/SiC to Metals

Carbon fiber reinforced silicon carbide composite (Cf/SiC) is the new high temperature ceramic composite developed in recent years, widely used in the aviation, aerospace and other high-tech fields. In this paper, a variety of joining methods of Cf/SiC composite to metallic materials, including active filler brazing, solid phase diffusion welding, liquid infiltration joining, as well as chemical vapor deposition of niobium transition joining technology were introduced. At the same time, the features and disadvantages of each technique were evaluated. This review is intended to provide a comprehensive guide to the design and application of Cf/SiC composite joining to metals.

Improvement of the electromagnetic shielding properties of C/SiC composites by electrophoretic deposition of carbon nanotube on carbon fibers

The current study reports on the improvement of electromagnetic interference (EMI) shielding properties of carbon fiber-reinforced silicon carbide composites by introduction of carbon nanotubes on carbon fiber cloths through the electrophoretic deposition (EPD) route and subsequent densification by chemical vapor infiltration. Findings demonstrate that the electrical conductivity of the composites increased with EPD durations up to 10 min, while the skin depth remained, in all case, one order on magnitude less than the specimen thickness, hence rendering multiple internal reflection issues negligible. The EMI absorption shielding effectiveness of the specimens was found to increase significantly with EPD duration, while absorption effectiveness reached a maximum of 38.2 dB at an EPD duration of 10 min, an increase of 56.5% over plain C/SiC composites. The achieved indices meet the specifications for effective EMI shielding of materials targeted for commercial and military field applications.

V-containing-active high-temperature brazes for ceramic joining

V-containing-active high-temperature brazing alloys were designed for ceramic joining, including PdCo–V, AuPdCoNi–V, AuCuPd–V, and CuPd–V system alloys. The joined ceramics or ceramic composites include Si3N4 ceramic, AlN ceramic, carbon fiber-reinforced silicon carbide composite (Cf/SiC), and C/C composite. The dynamic wettability of the V-containing brazes on ceramic or composite was studied with the sessile drop method. Based on the wetting experiment results, several alloys were chosen as the brazing filler metal. It was verified that during the brazing process, the reactions between the filler metal and the Si3N4 or AlN ceramic caused the formation of V–N layer at the interface close to the ceramic surface. The V–C compound was detected at the reaction interface between the V-containing-active filler metal and C/C composite or Cf/SiC composite. The formation of V–N or V–C layer played an important role in the joining of the ceramic or the ceramic composite. Both of the Si3N4–Si3N4 and Cf/SiC–Cf/SiC joints brazed with V-containing-active braze exhibited stable high-temperature property, and this should be attributed to the presence of refractory Pd2Si compounds within the joints. The newly developed V-containing-active brazes should have a potential to meet service temperatures of 973~1073 K, about 300 K higher than the AgCu–Ti brazing filler metals.

Comparison of Friction and Wear Behavior Between C/C, C/C-SiC and Metallic Composite Materials

The search for suitable friction materials for high-speed train is an attractive but difficult problem. In recent years, a variety of different novel friction materials were fabricated to meet the aims of high loads and speeds under ambient environment. Carbon fiber-reinforced carbon composites (C/C), carbon fiber-reinforced silicon carbide composites (C/C-SiC) and metallic composites fabricated by powder metallurgy are three excellent materials among them. Here a comparison of these three different materials working as brake pads, coupled with high-density C/C-SiC brake disk, was described. All the experiments were conducted using the same procedure with increasing initial braking speed (the rotation speed of brake disk at the beginning of braking process) from 30 to 59 m/s and constant load of 1.25 MPa, simulating the real working condition of high-speed train. The coefficient of friction (COF) and wear rates of three materials were compared and analyzed. During experiments, the COF of metallic and C/C pads remains nearly constant at 0.31 and 0.22, respectively, with increasing braking speed, while that of C/C-SiC exhibits a parabola. These different trends of COF may be attributed to the distinctive forming processes of friction film on the top of contact surfaces. Meanwhile, the wear rates of metallic composites increase rapidly from 683 to 1803 mm3/MJ with initial braking speed, while C/C-SiC presents the highest wear loss of 1887 mm3/MJ at 49 m/s and lowest value of 315 mm3/MJ at 59 m/s. Interestingly, the wear rate of C/C composites, due to the appropriate bonding strength of matrix/fiber and relatively high shear stress, decreases from 3698 to 903 mm3/MJ with increasing initial braking speed, which does not consist with pre-existing paper. Thus, metallic pads presented the lowest wear rates at lower speed (<49 m/s) but the highest at high speed, while C/C-SiC composite pads showed the greatest wear resistance at high speed. This investigation of three different friction materials will enhance our understanding of these friction materials and benefit the selection and safe application of high-speed train friction materials.

Impact behavior of different cross-ply laminated carbon fiber-reinforced silicon carbide composites under the low velocity

Carbon fiber-reinforced silicon carbide composites (C/SiC) were fabricated by a chemical vapor infiltration process using various ply orientations of 2D carbon fabric in the preform. The effect of ply angles (0°/90°, 45°/−45°, and 0°/45°/90°/−45°) on the low-velocity impact damage of the C/SiC composites was investigated externally and internally. Different depths of pits were formed in the impacted side with fibers sheared off, whereas fiber bundles breakage and matrix cracking appeared on the back side. The sample with 0°/90° ply angles experienced a serious fiber fracture and stratification damage, while the other two samples only showed a slight stratification. The samples with 0°/45°/90°/−45° and 0°/90° ply angles had nearly the same strength loss rate, which was smaller than that of the sample with 45°/−45° ply angle. In 45°/−45°, the ply angle had a major influence on the residual strength as the fibers were at 45° to the loading direction. Comparison of compression strength of the samples before and after impact test showed that the quasi-isotropic laminate improved the impact damage resistance due to the prevention of the devastating crack extension.

Complete recovery of high temperature oxidation resistance in carbon fiber reinforced SiC composites by a recoating repair methodology

The current work reports on the oxidation behavior and residual flexural strength of carbon fiber–reinforced silicon carbide composites (C/SiC) after induction of thermal crack damage by heat treatment (HT) at 1900°C and the effect, therein, of a repair process involving recoating by SiC. As-prepared, heat-treated and heat-treated/recoated specimens, were subjected to static oxidation tests in air at a temperature range of 500–1500°C for 10h and then tested in three-point bending. It was found that composite weight of heat-treated samples decreased dramatically with increasing oxidation temperature with weight loss values of ~30% being systematically observed for oxidation temperatures above 800°C. On the other hand, as-prepared and heat-treated/SiC-recoated specimens reached almost their original weight after oxidation. The residual flexural strength of C/SiC composites with thermally-induced crack damage decreased significantly compared to as-prepared specimens, while SiC recoating was found to efficiently enable strength enhancement. Microstructural analysis showed that HT was associated with increased population and dimensions of micro-cracks on the C/SiC surface while SiC recoating enabled repair of HT-induced thermal crack damage hence leading to oxidation resistance recovery of the material.

Interlaminar shear strength of SiC matrix composites reinforced by continuous fibers at 900 °C in air

To reveal the shear properties of SiC matrix composites, interlaminar shear strength (ILSS) of three kinds of silicon carbide matrix composites was investigated by compression of the double notched shear specimen (DNS) at 900°C in air. The investigated composites included a woven plain carbon fiber reinforced silicon carbide composite (2D-C/SiC), a two-and-a-half-dimensional carbon fiber-reinforced silicon carbide composite (2.5D-C/SiC) and a woven plain silicon carbon fiber reinforced silicon carbide composite (2D-SiC/SiC). A scanning electron microscope was employed to observe the microstructure and fracture morphologies. It can be found that the fiber type and reinforcement architecture have significant impacts on the ILSS of the SiC matrix composites. Great anisotropy of ILSS can be found for 2.5D-C/SiC because of the different fracture resistance of the warp fibers. Larger ILSS can be obtained when the specimens was loaded along the weft direction. In addition, the SiC fibers could enhance the ILSS, compared with carbon fibers. The improvement is attributed to the higher oxidation resistance of SiC fibers and the similar thermal expansion coefficients between the matrix and the fibers.

Preparation of C&lt;sub&gt;f&lt;/sub&gt;/SiC Composites by Chemical Liquid-Vapor Deposition Process

The conversion of the liquid polycabosilane (LPCS) into silicon carbide was investigated by IR, XRD, which indicated the feasibility of the transition from LPCS to SiC ceramics above 900°C. The FTIR spectra and XRD Pattern of the Cf/SiC composites show that the matrix deposited at 1200°C has silicon carbide structure with the crystallite size of β-SiC phase of about 41 nm, while the SiC phase is amorphous at 900°C. The carbon fiber reinforced silicon carbide composites (Cf/SiC) were hereby prepared at 900°C and 1200°C, through chemical liquid-vapor deposition (CLVD) process using LPCS as precursor. Flexural strength of 224 MPa for Cf/SiC specimen with density of 1.81g·cm-3was obtained after being prepared at 1200°C for 30 minutes. The load-deflection curve has shown that the fracture behavior of the Cf/SiC composites is a typical non-brittleness. The results indicate that the CLVD process has a great advantage and prospect to prepare Cf/SiC composites in future.

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 .

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.

Numerical prediction of the effective coefficient of thermal expansion of 3D braided C/SiC composite

This paper is focused on the microstructure modeling and evaluation of effective coefficient of thermal expansion (CTE) of 3D braided carbon fiber-reinforced silicon carbide composites (C/SiC). Regarding the multi-scale characteristics of the composite, the microstructure modeling is carried out sequentially from the fiber scale to tow scale. Effective elastic properties are obtained based on the sequential homogenization from the fiber scale to the tow scale. A stain energy model is developed for the prediction of the effective CTE of composite materials. This model is based on the relationship established between the strain energy of the microstructure and that of the homogenized equivalent model under specific thermo-elastic boundary conditions. Expressions of closed-form are derived for the effective CTE in terms of the strain energy and effective elastic tensor. Numerical results obtained by the proposed model show a good agreement with the results measured experimentally.