Fabrication of C/C-SiC composites using high-char-yield resin

Carbon fiber reinforced ceramic matrix composites (C/C-SiC composites) were fabricated using a type of high-char-yield phenolic resin with the char yield of 81.17 wt.%. Firstly, the fabric prepreg was prepared by spreading the phenolic resin solution onto the two dimensional carbon fiber plain weave fabric and dried consequently. Afterward, the resin was cured and then the carbon fiber reinforced polymer (CFRP) was pyrolyzed to get amorphous carbon. Finally, C/C-SiC composites were obtained through liquid silicon infiltration (LSI) process. SEM micrographs showed that the Si/SiC area was homogeneously dispersed in the matrix, and during the siliconization process, a layer of SiC was formed along the surface of carbon fibers or carbon matrix. The fiber volume of CFRP was about 40 vol.%, which was much lower than other studies. XRD result indicated that only β-SiC type was formed. The result of X-ray computed tomography clearly showed the structure changes before and after the melt infiltration process. Mechanical property test showed that the composites had fracture strength of 186 ± 23 MPa, and a flexural modulus of 106 ± 8 GPa.     

Evaluation of the moulding process for production of short-fibre-reinforced C/C-SiC composites

For the production of C/C-SiC brake discs via the liquid silicon infiltration method (LSI), the hot pressing process is the state of art technique for the moulding of the CFRP composites. This technique consists of several manual steps which increase production cost. The overall cost can be reduced by implementing injection moulding process.In this paper the influence of the moulding process (hot pressing, injection moulding) on the properties of semi-finished and final products during the production of short-fibre-reinforced C/C-SiC composites by means of the LSI process are examined. The starting polymer is chemically characterised. Carbon-fibre-reinforced plastic (CFRP) composites are fabricated by hot pressing, as well as injection moulding process. The CFRP composites are converted into porous C/C composites by pyrolysis. Liquid silicon is infiltrated to form dense C/C-SiC composites, which are further investigated during the course of this paper. Significant differences in properties of the composites are discussed.     

Electrical properties of C/C and C/C-SiC ceramic fibre composites

The electrical properties of carbon/carbon (C/C) and carbon/carbon-silicon carbide (C/C-SiC) ceramic composites were measured. The results show that the capacitance decreases rapidly with an increase in frequency and it becomes constant above a frequency of 500 kHz, whereas the dissipation factor increases with increasing frequency. C/C-SiC composites give higher value than C/C composites due to the presence of microcracks.     

Thermoset IM-LSI-based C/C-SiC: Influence of flow direction and weld lines on microstructure and mechanical properties

The production of ceramic matrix composites (CMC) based on C/C-SiC is still very cost-intensive and therefore only economical for a few applications. The fabrication of the preforms involves many costs that need to be reduced. In this work, the shaping of the CFRP-preforms is realized by thermoset injection molding, which enables large-scale production. The polymeric matrix used is a multi-component matrix consisting of novolak resin, curing agent and lubricant. Six millimeter chopped carbon fiber with a proportion of 50 wt.% were used as a reinforcement. These ingredients are processed by an industrial equipment for compounding and injection molding in order to manufacture a CFRP demonstrator representing a brake disc. Test specimens are cut out of the demonstrator in different directions in order to investigate influences of flow direction and weld lines on microstructural and mechanical properties. Afterward, the CFRP samples were converted to C/C-SiC composites by the liquid silicon infiltration process. The article addresses the flow behavior of the compound during the injection molding and the building of the weld lines in the demonstrator. In addition, results of the directional dependence of the microstructural and mechanical properties within the fabricated disc in the different production steps are presented.     

Shear properties of C/C-SiC sandwich structures

Carbon fiber reinforced carbon-silicon carbide (C/C-SiC) sandwich structures have been developed using the Liquid Silicon Infiltration process and the in situ joining method. They offer high mass-specific stiffness, low thermal expansion, and high environmental stability. Potential application areas are highly precise satellite structures, like optical benches. In this study, sandwich samples were manufactured using prepregs based on 2D carbon fibre fabrics and a phenolic resin precursor. Carbon fibre reinforced polymer preforms for folded and grid-cores, as well as for the skin panels were manufactured using autoclave technique. In the second step, the sandwich components were pyrolyzed, leading to C/C preforms. For the build-up of the sandwich samples, two skin panels were joined to a core structure and subsequently, the resulting C/C sandwich preform was siliconized. C/C-SiC sandwich samples were tested under shear load. Shear strength, modulus, and fracture strain were determined and compared to the results obtained by analytical calculation. The shear properties were dependent on the fiber orientation in the core structure as well as on the core type and orientation. The sandwich shear stiffness obtained in the tests was close to the expected theoretical values, calculated on the basis of the material properties and the core geometry.     

Fabrication and properties of Cf/(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C-SiC high-entropy ceramic matrix composites via precursor infiltration and pyrolysis

In this work, C_f/(Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C-SiC high-entropy ceramic matrix composites were reported for the first time. Based on the systematic study of the pyrolysis and solid-solution mechanisms of (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C precursor by Fourier transform infrared spectroscopy, TG-MS and XRD, C_f/(Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C-SiC with uniform phase and element distribution were successfully fabricated by precursor infiltration and pyrolysis. The as-fabricated composites have a density and open porosity of 2.40 g/cm³ and 13.32 vol% respectively, with outstanding bending strength (322 MPa) and fracture toughness (8.24 MPa m^1/2). The C_f/(Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C-SiC composites also present excellent ablation resistant property at a heat flux density of 5 MW/m², with linear and mass recession rates of 2.89 μm/s and 2.60 mg/s respectively. The excellent combinations of mechanical and ablation resistant properties make the C_f/(Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C-SiC composites a new generation of reliable ultra-high temperature materials.     

Evaluation of dynamic modulus measurement for C/C-SiC composites at different temperatures

The determination of elastic properties at application temperature is fundamental for the design of fibre reinforced ceramic composite components. An attractive method to characterize the flexural modulus at room and high temperature under specific atmosphere is the nondestructive Resonant Frequency Damping Analysis (RFDA). The objective of this paper was to evaluate and validate the modulus measurement via RFDA for orthotropic C/C-SiC composites at the application temperature. At room temperature flexural moduli of C/C-SiC with 0/90° reinforcement were measured under quasi-static 4-point bending loads and compared with dynamic moduli measured via RFDA longitudinally to fibre direction. The dynamic modulus of C/C-SiC was then measured via RFDA up to 1250°C under flowing inert gas and showed an increase with temperature which fitted with literature values. The measured fundamental frequencies were finally compared to those resulting from numerical modal analyses. Dynamic and quasi-static flexural moduli are comparable and the numerical analyses proved that bending modes are correctly modeled by means of dynamic modulus measured via RFDA. The nondestructive RFDA as well as the numerical modeling approach are suitable for evaluation of C/C-SiC and may be transferred to other fibre reinforced ceramic composite materials.     

C/C-SiC梯度基复合材料氧化行为研究

研究比较了Ｃ／Ｃ－ＳｉＣ梯度基复合材料和Ｃ／Ｃ复合材料的氧化行为．实验结果表明：ＳｉＣ通过占据表面活性点提高了共沉积基体的氧化起始温度;由于减少了碳与氧的接触面积,阻挡氧化凹坑的扩展,降低了材料的氧化质量损失速率．利用ＳＥＭ观察了梯度基复合材料微观氧化过程     

Interphase degradation of three‐dimensional Cf/SiC–ZrC–ZrB2 composites fabricated via reactive melt infiltration

Layer‐structured interphase, existing between carbon fiber and ultrahigh‐temperature ceramics (UHTCs) matrix, is an indispensable component for carbon fiber reinforced UHTCs matrix composites (C_f/UHTCs). For C_f/UHTCs fabricated by reactive melt infiltration (RMI), the interphase inevitably suffers degradation due to the interaction with the reactive melt. Here, C_f/SiC–ZrC–ZrB₂ composite was fabricated by reactive infiltration of ZrSi₂ melt into sol‐gel prepared C_f/B₄C–C preform. (PyC–SiC)₂ interphase was deposited on the fiber to investigate the degradation mechanism under ZrSi₂ melt. It was revealed that the degraded interphase exhibited typical features of Zr aggregation and SiC residuals. Moreover, the Zr species diffused across the interphase and formed nanosized ZrC phase inside the fiber. A hybrid mechanisms of chemical reaction and physical melting were proposed to reveal the degradation mechanism according to characterization results and heat conduction calculations. Based on the degradation mechanism, a potential solution to mitigate interphase degradation is also put forward.     

Preparation,ablation behavior and mechanism of C/C-ZrC-SiC and C/C-SiC composites

ZrC precursor was synthesized by a solution approach using ZrOCl₂·8H₂O, acetylacetonate, glycerol and boron-modified phenolic resin. A ZrC yield of ~ 40.56 wt% was obtained at 1500 °C in the C/Zr molar ratio of 1:1. C/C-ZrC-SiC composites were fabricated by a combined processes of chemical vapor infiltration (CVI) and precursor infiltration and pyrolysis (PIP) using the synthesized ZrC precursor. For comparison, C/C-SiC composites were prepared by CVI. Thermogravimetric analysis showed that C/C-ZrC-SiC composites exhibited better oxidation resistance than C/C-SiC composites. After oxyacetylene torch ablation, the mass ablation rate of C/C-ZrC-SiC composites was 9.23% lower than that of C/C-SiC composites. The porous ZrO₂ skeleton in the ablation center was prone to be peeled off by the flame flow, resulting in the higher linear ablation rate of C/C-ZrC-SiC composites. The oxide layers of ZrO₂ and SiO₂ were formed on the transition and brim region of C/C-ZrC-SiC composites and acted as effective heat and oxygen barriers. For C/C-SiC composites, the C-SiC matrix was severely depleted in the ablation center and the formed SiO₂ layer in the brim region could protect the matrix against further ablation.     

C/C-SiC component for metallic phase change materials

Thanks to their high energy density and thermal conductivity, metallic Phase Change Materials (mPCM) have shown great potential to improve the performance of thermal energy storage systems. However, the commercial application of mPCM is still limited due to their corrosion behavior with conventional container materials. This work first addresses on a fundamental level, whether carbon-based composite-ceramics are suitable for corrosion critical components in a thermal storage system. The compatibility between the mPCM AlSi₁₂ and the Liquid Silicon Infiltration (LSI)-based carbon fiber reinforced silicon carbide (C/C-SiC) composite is then investigated via contact angle measurements, microstructure analysis, and mechanical testing after exposure. The results reveal that the C/C-SiC composite maintains its mechanical properties and microstructure after exposure in the strongly corrosive mPCM. Based on these results, efforts were made to design and manufacture a container out of C/C-SiC for the housing of mPCM in vehicle application. The stability of the component filled with mPCM was proven nondestructively via computer tomography (CT). Successful thermal input- and output as well as thermal storage ability were demonstrated using a system calorimeter under conditions similar to the application. The investigated C/C-SiC composite has significant application potential as a structural material for thermal energy storage systems with mPCM.     

Short fiber-reinforced oxide fiber composites

This paper presents a novel fiber spraying process for the manufacturing of short fiber bundle-reinforced Nextel™ 610/Al₂O₃-ZrO₂ oxide fiber composites (SF-OFC) and its characterization. First, the influence of varying fiber lengths (7, 14, and 28 mm, continuous fibers) and fiber orientations (unidirectional 0°, quasi-isotropic, ±45°) was investigated using hand-laid SF-OFC. Due to the weak matrix, the hand-laid material exhibited a strongly fiber-dominated material behavior, that is, variations in fiber length and orientation had a strong influence on the material properties. Second, the automated sprayed SF-OFC, however, exhibited a random orientation of the fiber bundles, which resulted in in-plane isotropic material properties. Average bending strengths of up to 177 MPa, strains of .39%, and a quasi-ductile fracture behavior were achieved. The strain was, therefore, in the range of fabric-reinforced OFC. While the bending strength of the SF-OFC was somewhat lower than that of fabric-reinforced OFC with the fiber orientation parallel to the loading direction, it was more than two times higher than the strength in 45° direction relative to the fabric reinforcement. Combined with good drapability and lower material costs compared to fabric-reinforced OFC, SF-OFC is, therefore, a promising material for industrial applications.     

Manufacture and thermomechanical characterization of wet filament wound C/C-SiC composites

The paper presents manufacture of C/C-SiC composite materials by wet filament winding of C fibers with a water-based phenolic resin with subsequent curing via autoclave as well as pyrolysis and liquid silicon infiltration (LSI). Almost dense C/C-SiC composite materials with different winding angles ranging from ±15° to ±75° could be obtained with porosities lower than 3% and densities in the range of 2 g/cm³. Thermomechanical characterization via tensile testing at room temperature and at 1300°C revealed higher tensile strength at elevated temperature than at room temperature. Thus, C/C-SiC material obtained by wet filament winding and LSI-processing has excellent high-temperature strength for high-temperature applications. Crack patterns during pyrolysis, microstructure after siliconization, and tensile strength strongly depend on the fiber/matrix interface strength and winding angle. Moreover, calculation tools for composites, such as classical laminate and inverse laminate theory, can be applied for structural evaluation and prediction of mechanical performance of C/C-SiC structures.     

Additive manufacturing of continuous carbon fiber reinforced high entropy ceramic matrix composites via paper laminating,direct slurry writing,and precursor infiltration and pyrolysis

In this study, continuous carbon reinforced C_f/(Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C–SiC high entropy ceramic matrix composites were additively manufactured through paper laminating (PL), direct slurry writing (DSW), and precursor infiltration and pyrolysis (PIP). (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C high entropy ceramic (HEC) powders were synthesized by pressureless sintering and ball milling. A certain proportion of HEC powder, SiC powder, water, binder, and dispersant were mixed to prepare the HEC-SiC slurry. Meanwhile, BN coating was prepared on the 2D fiber cloth surface by the boric acid-urea method and then the cloth was cut into required shape. Additive manufacturing were conducted subsequently. Firstly, one piece of the as-treated carbon fiber cloth was auto-placed on the workbench by paper laminating (PL). Then, the HEC-SiC slurry was extruded onto the surface of the cloth by direct slurry writing (DSW). PL and DSW process were repeated, and a C_f/HEC-SiC preform was obtained after 3 cycles. At last, the preform was densified by precursor infiltration and pyrolysis (PIP) and the final C_f/HEC-SiC composite was prepared. The open porosity of the C_f/HEC-SiC composites, with the HEC volume fractions of 15, 30 and 45%, were 7.7, 10.6, and 11.3%, respectively. And the density of the C_f/HEC-SiC composites, with the HEC volume fractions of 15, 30 and 45%, were 2.9, 2.7 and 2.3 g/cm³, respectively. The mechanical properties of the C_f/HEC-SiC composites increased firstly and then decreased with the HEC content increase, reaching the maximum value when the HEC volume fraction was 30%. The mechanical properties of the C_f/HEC-SiC composites containing 45, 30 and 15% HEC were as follows: flexural strength (180.4 ± 14 MPa, 183.7 ± 4 MPa, and 173.9 ± 4 MPa), fracture toughness (11.9 ± 0.17 MPa m^1/2, 14.6 ± 2.89 MPa m^1/2, and 11.3 ± 1.88 MPa m^1/2), and tensile strength (71.5 ± 4.9 MPa, 98.4 ± 12.2 MPa, and 73.4 ± 8.5 MPa). From this study, the additive manufacturing of continuous carbon fiber reinforced high entropy ceramic matrix composites was achieved, opening a new insight into the manufacturing of ceramic matrix composites.     

Additive manufacturing of fiber reinforced ceramic matrix composites: Advances,challenges, and prospects

Fiber reinforced ceramic matrix composites (FRCMCs) have been used in various engineering fields. Additive manufacturing (AM) technologies provide new methods for fabricating FRCMCs and their structures. This review systematically reviews the additive manufacturing technologies of FRCMCs. In this review, the progress for additive manufacturing of FRCMCs were summarized firstly. The key scientific and technological challenges, and prospects were also discussed. This review aims to motivate the future research of the additive manufacturing of FRCMCs.     

A Review on Wear and Friction Performance of Carbon–Carbon Composites at High Temperature

Carbon–carbon (C/C) composite is one of the best ceramic matrix composite due to its high mechanical properties and applications at control environments in various sectors. Carbon–carbon composite is made of woven carbon fibers; carbonaceous polymers and hydrocarbons are used as matrix precursors. These composites generally have densities <2.0 g/cm³ even after densification. C/C composites have good frictional properties and thermal conductivity at high temperature. Also C/C composite can be used as brake pads in high‐speed vehicles. In spite of various applications, C/C composites are very much prone to oxidation at high temperature. Therefore, C/C composites must be protected from oxidation for the use at high temperature.     

Effects of Preform Shear on Tensile Properties of a Woven C/SiC Composite

This article addresses effects of weave defects in an angle‐interlock C‐fiber preform on the tensile properties of the resulting fully processed C‐fiber/SiC‐matrix composite. For this purpose, a preform was intentionally sheared in a controlled manner after weaving. The resulting distortions were quantified by analyzing high‐resolution images of the preform surface after the first step of matrix processing, while the tows were still clearly visible. Comparisons are made of tensile test results on specimens cut from this composite panel and from a pristine panel in select loading orientations. Strain maps obtained by digital image correlation are used to identify local strain variations that are attributable to weave defects. The results are discussed in terms of: (i) the shear‐normal coupling that arises in loading orientations of present interest, and (ii) the geometric effects of tow misalignment on tow continuity along the specimen gauge length. The composite is found to perform in a robust manner, in the sense that the tensile properties are not sensitive to the presence of the defects.     

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

The 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.     

SiC/SiC复合材料及其应用

日本开发的Nicalon和Tyranno两种品牌的SiC纤维占有世界上绝对性的市场份额。SiC/SiC复合材料典型的界面层是500 nm厚的单层热解碳(PyC)涂层或多层(PyC-SiC)n涂层,在湿度燃烧环境及中高温条件下界面层的稳定性是应用研究的重点。SiC/SiC复合材料,包括CVI-SiC基体和日本开发的Tyranno hex和NITE-SiC基体等,具有耐高温、耐氧化性和耐辐射性的特点,在航空涡轮发动机部件、航天热结构部件及核聚变反应堆炉第一壁材料等方面正开展工程研制应用。     

C/C多孔体对C/C-SiC复合材料微观结构和弯曲性能的影响

以4种纤维含量相同(32%,体积分数,下同),用化学气相渗透(chemical vapor infiltration,CVI)法制备了4种密度的碳纤维增强碳(carbon fiber reinforced carbon,C/C)多孔体,基体炭含量约20%～50%.利用液相渗硅法(liquid silicon infiltration,LSI)制备了C/C-SiC复合材料,研究了C/C多孔体对所制备的C/C-SiC复合材料微观结构和弯曲性能的影响.结果表明:不同密度的C/C多孔体反应渗硅后,复合材料的物相组成均为SiC,C及单质Si;随着C/C多孔体中基体炭含量的增加,C/C-SiC复合材料中SiC含量逐渐减少而热解炭含量逐渐增加.C/C-SiC复合材料弯曲强度随着材料中残留热解炭含量增加而逐渐增加,热解炭含量为约42%的C/C多孔体所制备的C/C-SiC复合材料的弯曲强度最大,达到320 MPa.