Carbon Fiber Reinforced Silicon Carbide Research Articles

Effect of pyrocarbon interphase texture and thickness on tensile damage and fracture in T‐700™ carbon fiber–reinforced silicon carbide minicomposites

AbstractIn this paper, T‐700™ carbon fiber–reinforced silicon carbide (C/SiC) minicomposites with pyrocarbon (PyC) interphase with different textural microstructure and thickness were fabricated using the chemical vapor infiltration method. The interface properties (i.e., textural microstructure, thickness, hardness, and modulus) were obtained through multiple testing methods (i.e., Raman spectroscopy, X‐ray diffraction, scanning electron microscopy, and nanoindentation tests). Relationships between the deposition temperature and residence time with the texture type (i.e., low, medium, and high texture) were established. Uniaxial tensile experiments were conducted for C/SiC minicomposites with different PyC interphases to characterize the composite's internal damage evolution and fracture. Relationships between the composite's tensile nonlinear damage evolution, fracture strength and strain, PyC interphase texture, and thickness were established. The composite's tensile strength and fracture strain were the highest for the C/SiC minicomposite with medium‐high texture PyC interphase. For the C/SiC minicomposite with the same texture interphase, the composite's tensile strength and fracture strain were affected by the coating thickness. The higher the thickness of the coating, the lower the composite's tensile strength and fracture strain.

Heat Insulation Performance of Lattice Thermal Protection Structure with Reinforced Plate

A lightweight lattice structure is proposed, which can be applied to the thermal protection system of high speed aircraft. The structure uses carbon fiber reinforced silicon carbide ceramic matrix composite as the framework, and the inner cavity can be filled with heat insulation materials with small thermal conductivity. In order to study the heat insulation performance of the structure, the three-dimensional finite element heat transfer model of the lattice structure with and without heat insulation material was established. Abaqus software was used to calculate the temperature distribution and change of the lattice structure under different temperature boundary conditions. The equivalent thermal conductivity of the lattice structures under different temperature boundary conditions is defined and calculated. The results show that the heat insulation effect of the lattice structure is improved obviously with the addition of heat insulation materials, but the time required to reach the stable state is increased. Without heat insulation materials, the strength of cavity radiation is greatly affected by the temperature boundary conditions on the top surface and positively correlated. Increasing heat insulation materials can effectively block the generation of cavity radiation, thus enhancing the heat insulation effect. The conclusion provides a foundation for further application of the lattice structure in thermal protection system of high speed aircraft.

Insights into fracture mechanisms and strength behaviors of two-dimensional carbon fiber reinforced silicon carbide composites at elevated temperatures

Carbon fiber reinforced silicon carbide (C/SiC) composites are usually subjected to thermal-mechanical-oxidation-coupled loads during service. However, their mechanical properties at ultra-high temperatures in oxidizing environments have rarely been reported. In this paper, a method based on the induction heating technology is proposed for testing the ultra-high-temperature mechanical properties of materials in air. The flexural behaviors of a 2D plain-weave C/SiC material prepared via chemical vapor infiltration are investigated in air up to 1800 °C for the first time. Inverse temperature dependences of the flexural modulus and strength are observed. New fracture mechanisms that are responsible for the mechanical behaviors at elevated temperatures are elucidated. Fracture modes at different temperatures are proposed. A high-temperature fracture strength model for oxidizing environments is developed, which is in good agreement with the experimental results. The factors affecting the fracture strength behaviors of the C/SiC in air at elevated temperatures are characterized quantitatively.

High-temperature compressive performance of the pre-impacted 2D-C/SiC composites: Coupling effect of pre-impact energy, temperature, temperature-keeping duration, and strain rate

Two-dimensional carbon fiber reinforced silicon carbide (2D-C/SiC) composites are well-known for the high-temperature performance in aeronautical and aerospace fields, but they are susceptible to foreign object damage in service. Therefore, the high-temperature performance of pre-impacted 2D-C/SiC is closely connected with flight security. In this study, the pre-impact testing was conducted using a stress-reversal split Hopkinson bar, and the pre-impact energies were set from 0.1J to 0.9J. Subsequently, the pre-impacted specimens were heated for a period in the temperature-keeping procedure from 20 °C to 1600 °C. Oxidation kinetics of the pre-impacted 2D-C/SiC specimens were obtained based on the weight loss-temperature trends. Finally, the specimens were compressed under high temperatures at the strain rates from 10−4/s to 1000/s, so the residual compressive strength (RCS)-temperature trends were achieved. Hence, the correlation between the weight loss and the RCS was established. Interestingly, the pre-impact strengthening effect on the compressive strength was found. The results revealed that the RCS of 2D-C/SiC is affected by various parameters, providing new sights into the high-temperature damage tolerance of ceramic matrix composites.

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.

Snap-through response of thermally buckled C/SiC plates considering boundary elasticity and initial imperfections under progressive wave loading

In this paper, the snap-through response of a rectangular clamped carbon fiber reinforced silicon carbide composites (C/SiC) plate is studied under a high-temperature field and progressive wave acoustic load with considering the boundary elasticity and initial imperfections. The dynamic model of the plate is established, and the boundary stiffnesses and imperfection coefficients are updated with experimental results. Results show a significant correlation between the snap-through occurrence and the response spectra evolution. The progressive wave acoustic load promotes the antisymmetric modes and leads to the inhibition of snap-through compared to the uniform sound pressure load. It is found that the thickness and initial imperfection have significant influences on the snap-through boundary. It is indicated that those parameters shall be considered during the prediction of the snap-through. This study provides a well reference for the design of the structure for the hypersonic aircraft.

Thermal shock response behaviour of carbon fibre reinforced silicon carbide matrix composites prepared by chemical vapour infiltration at different heating rates

The present work investigated the effects of thermal cycles in air on the tensile properties of a two-dimensional carbon fibre reinforced silicon carbide composite (2D C/SiC) prepared by chemical vapour infiltration at different heating rates. The composite was exposed to different cycles of thermal shock between 20 °C and 1300 °C in air. The damage mechanisms were investigated by AE online monitoring and fractured morphology offline analysis. The tensile strength of 2D-C/SiC decreases with increasing thermal cycles. However, the modulus only decrease within 40 cycles. Due to oxidation, with the decrease in heating rate, the residual properties of the material decrease more obviously. Meanwhile, the results of AE online monitoring and fracture analysis show that the matrix damage is more serious at higher heating rate and that more delamination occours in tensile fractures. The above results indicate that for the thermal shock of 2D C/SiC composites in air, oxidative damage plays a key role in the residual properties.

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.

Multiple nonlinear regression model of cutting force for C/SiC composites by laser‐assisted micromachining

AbstractBased on the response surface methodology (RSM), laser‐assisted micromachining (LAMM) experiments of carbon fiber reinforced silicon carbide matrix(C/SiC) composites have been carried out to obtain the data of three‐direction cutting forces Fx, Fy, Fz, and result‐force F in the cutting process. A stepwise regression method is used to screen out the factors that significantly affected the cutting force, and hence a multivariate nonlinear mathematical regression model has been established. Through the analysis of variance and regression analysis, the R2 of the regression model is the cutting force Fx: 0.975, the cutting force Fy: 0.970, the cutting force Fz: 0.972, the resultant force F: 0.987, and the probability p > F‐values are all less than 0.001. The model analysis results show that the main effects and interactions of the three factors of laser power, cutting speed, and cutting depth significantly influence the cutting force. The main effect of the most considerable influence on the resultant F is cutting depth, followed by cutting speed and laser power, and the interactive effect is cutting speed and cutting depth. The experimental results show that the model prediction results are in good agreement with the experimental results.

Experimental evaluation and theoretical prediction of elastic properties and failure of C/C‐SiC composite

AbstractThe paper presents experimental characterization and theoretical predictions of elastic and failure properties of continuous carbon fiber reinforced silicon carbide (C/C‐SiC) composite fabricated by Liquid Silicon Infiltration (LSI). Its mechanical properties were determined under uniaxial tensile, compression, and pure shear loads in two sets of principal coordinate systems, 0°–90° and ±45°, respectively. The properties measured in the 0°–90° coordinate system were employed as the input data to predict their counterparts in the ±45° coordinate system. Through coordinate transformations of stress and strain tensors, the elastic constants and stress‐strain behaviors were predicted and found to be in good agreement with the experimental results. In the same way, three different failure criteria, maximum stress, Tsai‐Wu, and maximum strain, have been selected for the evaluation of the failure of C/C‐SiC as a type of genuinely orthotropic material. Based on the comparisons with experimental results, supported by necessary practical justifications, the Tsai‐Wu criterion was found to offer a reasonable prediction of the strengths, which can be assisted by the maximum stress criterion to obtain an indicative prediction of the respective failure modes.

Development of C/SiC Fasteners for High-Temperature Applications

Continuous carbon fiber reinforced silicon carbide (C/SiC) ceramic matrix composites are the candidate materials for high-temperature structural applications owing to their high specific strength, low coefficient of thermal expansion, and moderate thermal conductivity. C/SiC based fasteners provide reliability with oxidation resistance up to 1,650°C for joining such C/SiC structural components used in reusable launch vehicles for space applications. The present study describes the methodology to realize C/SiC based M8 fasteners by isothermal-isobaric chemical vapor infiltration process using 2D-stitched carbon fabric preforms. The realized fasteners exhibited a density of 2.10 g/cm3, a tensile strength of 191 ± 3 MPa, a shear strength of 230 ± 69 MPa in non-threaded and 150 ± 86 MPa in threaded regions of shank at room temperature, a high-temperature tensile strength of 170 ± 12 MPa, and a tensile modulus of 70 ± 8 GPa at 1,100°C in the atmospheric conditions. The tensile failure of the C/SiC bolts was observed to depend upon the relative dimensions of fillet radius and thread root radius, wherein a small fillet radius was observed to be detrimental, as it resulted in failure at the head-shank interface of the bolts. The scanning electron microscope images of tensile tested C/SiC bolts indicate extensive fiber pullout, characteristic of quasi-ductile failure of bolts. It is clearly evident from the studies that the C/SiC fasteners are a promising alternative over the currently used molybdenum alloy fasteners.

Investigation of the bulging mechanism of C/SiC coating through in situ optical observation and numerical simulation

Carbon fibre-reinforced silicon carbide composites (C/SiC) are a type of high-temperature structural ceramics that can be widely applied in aerospace, hypersonic aircraft, and military fields. However, the practical application of such materials in some complex high-temperature environments is still limited owing to drawbacks such as the bulging problem. In this study, the bulging of a C/SiC coating in a high-temperature wind tunnel is investigated. The surface data of specimens in the high-temperature arc wind tunnel were obtained using optical visualisation equipment, and the entire process of the formation of coating bulges, and their evolution and fusion is illustrated. Then, a fully coupled thermal fluid-solid simulation model is established, and the influence of defects on the internal heat transfer of materials is analysed. Further, the thermal fluid-solid coupling simulation technology is also used to analyse the bulging process of the coating to understand the mechanism of chemical reactions in defects between the coating and substrate. This work can serve as a guide for the screening and improvement of the material coating process.

Application of VERDI detectors for neutron fluence measurements during the JET 2019 Deuterium-Deuterium campaign

The Novel Neutron Detector for Fusion (VERDI) project aims to develop a passive detector which will provide a robust approach for neutron detection in current and future fusion devices. The detector comprises a low activation capsule, capable to withstand the harsh fusion conditions, containing defined added metallic elements, the activation of which provides neutron fluence and energy spectrum information. In the present work, VERDI detectors were employed for the first time to determine neutron fluence and energy spectra at the Joint European Torus (JET) Long Term Irradiation Station (LTIS) during the 2019 Deuterium-Deuterium (DD) campaign. Two materials, graphite and carbon fibre reinforced silicon carbide composite, were used for the capsule fabrication containing disc-shaped activation foils (Ag, Mn, Nb, Ni, Rh, Ti, Y). Post-irradiation gamma-spectrometry measurements were performed in order to identify the product isotopes and derive the incident neutron fluence. The results were fed into the MAXED code to reconstruct the neutron spectrum. The derived spectrum was in very good agreement with the calculated one using the MCNP code. A difference of 8% was found between the derived and the experimentally determined total integrated neutron flux. This work demonstrates the feasibility of employing VERDI detectors for neutron measurements in real fusion environments.

Damage Evolution and Fracture Behavior of C/SiC Minicomposites with Different Interphases under Uniaxial Tensile Load.

In this paper, the tensile damage and fracture behavior of carbon fiber reinforced silicon carbide (C/SiC) minicomposites with single- and multiple-layer interphases are investigated. The effect of the interphase on the tensile damage and fracture behavior of C/SiC minicomposites is analyzed. The evolution of matrix cracking under the tensile load of the C/SiC minicomposite with a notch is observed using the digital image correlation (DIC) method. The damage evolution process of the C/SiC minicomposite can be divided into four main stages, namely, (1) an elastic response coupled with partial re-opening of thermal microcracking; (2) multiple matrix microcracking perpendicular to the applied loading; (3) crack opening and related fiber/matrix, bundle/matrix, and inter-bundle debonding; and (4) progressive transfer of the load to the fibers and gradual fiber failure until composite failure/fracture. On the fracture surface, a large number of fibers pulling out of the samples with both single-layer and multi-layer interphases can be clearly observed.

Fabrication of Core-Shell Chopped Cf-Phenolic Resin Composite Powder for Laser Additive Manufacturing of Cf/SiC Composites.

Laser additive manufacturing is a promising technique for the preparation of complex-shaped SiC composites. High-quality powders are critical for high-precision laser printing. In this work, core-shell Cf @phenolic resin (PR) composites for selective laser sintering of carbon fiber reinforced silicon carbide (Cf/SiC) composites were fabricated by surface modification using 3-aminopropyltriethoxy silane coupling agent (KH550) in combination with planetary ball milling. PR coated uniformly on the fiber surface to form a core-shell structure. The effects of PR on the morphology, elemental composition, interfacial interactions, and laser absorption of the core-shell composite powder were investigated in detail. Results indicated that the composite powder exhibited good laser absorption within the infrared band.

3DN C/SiC composites with different porosities for tunable lubrication performance

Three-dimensional needled carbon fiber reinforced silicon carbide (3DN C/SiC) composites are potential candidates for lubrication systems because of their great lubrication and wear resistance performance. In this paper, different thicknesses of SiC were deposited by chemical vapor infiltration (CVI) method to prepare 3DN C/SiC composites with controllable porosities, aiming to investigate the effect of different porosities on their lubrication performance under the various load-bearing conditions. Results showed that the friction coefficients of 3DN C/SiC composites decreased with increasing porosity, and the wear rate of the sample with a porosity of 60% was much higher than that of samples with porosity of 30% and 15%. Specifically, the 3DN C/SiC sample with a porosity of 30% exhibited ideal lubricating performance under the load of 10 N, with a lowest friction coefficient of 0.230 and favorable wear rate of 2.20 × 10−4 mm3/(N·m). As for the effect of load, the friction coefficient and wear rate of the sample with a porosity of 30% decreased with increasing load. The lubrication mechanism is mainly the formation of friction film. Therefore, this study presented an effective way to enhance the lubrication performance of 3DN C/SiC composites, which makes it practically applicable in lubrication systems.

Water-Lubricated Friction Properties of C/C-SiC Composites with Different SiC-Phase Contents Fabricated by RMI

Carbon fiber–reinforced silicon carbide matrix (C/C-SiC) composites with different SiC contents were fabricated by reactive melt infiltration of silicon with four types of porous C/C composites prepared by chemical vapor infiltration. Compared to high-density C/C composites and silicified graphite, the C/C-SiC composites demonstrated an excellent balance of mechanical properties, especially impact toughness. The results show that the porosity of C/C composites is a key factor that affects the SiC content in the C/C-SiC composites. A W18Cr4V steel alloy (hardness 55–60 HRC, roughness 0.8 μm) was used as the material for the friction pair. The friction coefficient of the C/C-SiC composites measured by block-on-ring friction tests is mainly influenced by SiC content and test load. The friction coefficient first increases and then decreases as the SiC content and test load increase, reaching a minimum of 0.011 for 44.22 vol% SiC composite under a load of 80 N. Water also plays an important role in decreasing the friction coefficient. Observations of the worn surface and wear debris indicate that the main wear mechanism of C/C-SiC composites is abrasive wear.

Experimental study on cutting force and surface quality in ultrasonic vibration-assisted milling of C/SiC composites

Carbon fiber-reinforced silicon carbide matrix (C/SiC) composites are typical difficult-to-cut materials due to high hardness and brittleness. Aiming at the problem of the serious high cutting force and poor surface quality in conventional milling (CM) C/SiC composite process, ultrasonic vibration-assisted milling (UVAM) and conventional milling tests with a diamond-coated milling cutter were conducted. The results showed that reducing the feed per tooth, cutting depth, or increasing the cutting speed can reduce the average cutting force, and increasing the ultrasonic amplitude, the average cutting force decreases first and then increases. With the assistance of ultrasonic vibration, the maximum reduction rates of average cutting forces Fx, Fy, and Fz were 43.7%, 29.16%, and 68.09%.The ultrasonic vibration assisting effect does not significantly improve the damage of materials such as fiber breakage during processing. The ultrasonic vibration assisting effect improves the quality of processing edges. It is found that reducing feed per tooth, cutting depth, or increasing cutting speed can reduce surface roughness and increasing the ultrasonic amplitude reduces the surface roughness first and then increases. On the whole, the surface roughness of C/SiC ultrasonic vibration milling is slightly smaller than that of conventional machining.

Sustainable Machining of Cf/SiC Ceramic Matrix Composite Using Green Cutting Fluids

Understanding the machinability of carbon fiber reinforced silicon carbide (Cf/SiC) ceramic matrix composite is important due to its large number of applications in defense, aerospace, and automobile industries. Cf/SiC has unique properties like high hardness, low density, high strength to weight ratio, and high oxidative stability even at a higher temperature. However, machining of Cf/SiC is an arduous task owing to its anisotropic and non-homogeneous structure. In this work, sustainable machining of Cf/SiC composite is carried out using inhouse tailored vegetable-based green cutting fluid (GCF) and compared with “Synergy 735”, a petroleum-based commercial mineral oil (MO) with minimum quantity lubrication (MQL) technique. Surface integrity and surface roughness are measured against varying control variables such as cutting speed, depth of cut, and feed rate. After machining experiments, fiber pullout, fiber breakage, matrix cracking, and interfacial debonding of fiber-matrix are observed on the machined workpiece. Results show that GCF reduces up to 17% of surface roughness of machined workpiece over MO. Also, surface integrity is better for GCF compared to MO machined surfaces.

Ultra-high-temperature mechanical behaviors of two-dimensional carbon fiber reinforced silicon carbide composites: Experiment and modeling

Carbon fiber reinforced silicon carbide (C/SiC) composites are enabling materials for components working in ultra-high-temperature extreme environments. However, their mechanical properties reported in the literature are mainly limited to room and moderate temperatures. In this work, an ultra-high-temperature testing method for the mechanical properties of materials in inert atmosphere is presented based on the induction heating technology. The flexural properties of a 2D plain-weave C/SiC are studied up to 2600 °C in inert atmosphere for the first time. The deformation characteristics and failure mechanisms at elevated temperatures are gained. Theoretical models for the high-temperature Young’s modulus and tensile strength of 2D ceramic matrix composites are then developed based on the mechanical mechanisms revealed in the experiments. The factors contributing to the mechanical behaviors of C/SiC at elevated temperatures are thus characterized quantitatively. The results provide significant understanding of the mechanical behaviors of C/SiC under ultra-high-temperature extreme environment conditions.