Fiber-reinforced SiC Research Articles

Multi-scale Modeling and Finite Element Analyses of Thermal Conductivity of 3D C/SiC Composites Fabricating by Flexible-Oriented Woven Process

Thermal conductivity is one of the most significant criterion of three-dimensional carbon fiber-reinforced SiC matrix composites (3D C/SiC). Represent volume element (RVE) models of microscale, void/matrix and mesoscale proposed in this work are used to simulate the thermal conductivity behaviors of the 3D C/SiC composites. An entirely new process is introduced to weave the preform with three-dimensional orthogonal architecture. The 3D steady-state analysis step is created for assessing the thermal conductivity behaviors of the composites by applying periodic temperature boundary conditions. Three RVE models of cuboid, hexagonal and fiber random distribution are respectively developed to comparatively study the influence of fiber package pattern on the thermal conductivities at the microscale. Besides, the effect of void morphology on the thermal conductivity of the matrix is analyzed by the void/matrix models. The prediction results at the mesoscale correspond closely to the experimental values. The effect of the porosities and fiber volume fractions on the thermal conductivities is also taken into consideration. The multi-scale models mentioned in this paper can be used to predict the thermal conductivity behaviors of other composites with complex structures.

Hoop tensile properties of SiC fiber-reinforced SiC matrix composite tubes with/without CVD-SiC coating

Continuous SiC fiber-reinforced SiC ceramic matrix (SiCf/SiC) composite tubes with/without external CVD-SiC coating were mechanically tested with a C-ring sample geometry. The hoop tensile strength of the tubes with the coating (∼169 MPa) was higher than those without coating (∼108 MPa). SEM observation showed the propagation of cracks in SiCf/SiC composite materials led to the debonding of fibers from the matrix and resulted in the delamination of fiber bundles. The propagation direction of the crack initiated in the CVD-SiC coating moved toward the center of the C-ring, deflected and extended along the boundary between the coating and SiCf/SiC composite. The CVD-SiC coating and the interface between the coating and SiCf/SiC composite could effectively protect the SiCf/SiC composite, thereby improving the hoop tensile strength and maintaining the integrity of the cladding tube.

Mechanical properties and tensile failure behavior of SiCnf/SiC composites with multilayer interphases

SiC fiber-reinforced SiC ceramic matrix composites (SiCf/SiC CMCs) hold potential as thermal structural materials. In this work, SiC nanofibres were coated with multilayer interfaces by magnetron sputtering with the aim to tailor the fiber-matrix interface of SiC nanofibre reinforced SiC composites for superior mechanical properties. The influence of multilayer interface coating and sintering temperature on the density, microstructure, and mechanical properties of SiCnf/SiC CMCs fabricated via a hot-press technique employing ultra-long single-crystal SiC nanofibers as reinforcement were investigated. The composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and a universal testing machine. The prepared CMCs were toughened and strengthened by the observed fiber pull-out and bridging. The multilayered SiCnf/SiC CMCs with multiple interface coatings display an identifiable saw-tooth-like pattern in the load-displacement test, suggesting a significant improvement in the toughness of prepared materials through a laminated structure with weaker interface binding brought on by the thicker, denser coating. In comparison to the SiCnf/SiC composites without interface coating, the prepared SiCnf/SiC CMCs with PyC/SiAlC/ZrC interface layers revealed optimum flexural strength (520 ± 28.88 MPa, ↑46.5 %) and fracture toughness (9.95 ± 0.44 MPa m1/2, ↑94.7 %) after an hour of hot pressing at 1800 °C under pressure of 30 MPa. Besides an increase in relative density at high sintering temperatures (1850 °C), further grain coarsening deteriorated mechanical properties.

Fabrication of bamboo-inspired continuous carbon fiber-reinforced SiC composites via dual-material thermally assisted extrusion-based 3D printing

Ceramic matrix composites (CMCs) structural components encounter the dual challenges of severe mechanical conditions and complex electromagnetic environments due to the increasing demand for stealth technology in aerospace field. To address various functional requirements, this study integrates a biomimetic strategy inspired by gradient bamboo vascular bundles with a novel dual-material 3D printing approach. Three distinct bamboo-inspired structural configurations Cf/SiC composites are designed and manufactured, and the effects of these different structural configurations on the CVI process are analyzed. Nanoindentation method is utilized to characterize the relationship between interface bonding strength and mechanical properties. The results reveal that the maximum flexural strength and fracture toughness reach 108.6 ± 5.2 MPa and 16.45±1.52 MPa m1/2, respectively, attributed to the enhanced crack propagation resistance and path caused by the weak fiber-matrix interface. Furthermore, the bio-inspired configuration enhances the dielectric loss and conductivity loss, exhibiting a minimum reflection loss of −24.3 dB with the effective absorption band of 3.89 GHz. This work introduces an innovative biomimetic strategy and 3D printing method for continuous fiber-reinforced ceramic composites, expanding the application of 3D printing technology in the field of CMCs.

Microstructure and mechanical properties of continuous carbon fiber-reinforced SiC ceramic composite fabricated by direct ink writing

The direct ink writing (DIW) technique is considered efficient for manufacturing complex-shaped Cf/SiC composites. However, the SiC slurry with high load has poor flow ability and covering-fibers properties, resulting in numerous gaps between the ceramic matrix and fibers. This study utilized DIW to manufacture Cf/SiC composites and improved the slurry's printing ability by adjusting the binder content. Moreover, the printing parameters, such as the angle between the fiber nozzle and slurry nozzle and the slurry nozzle size, were optimized to enhance the accuracy of the body structure and the filling effect of the slurry on the fiber gaps. The results showed that a binder content of 0.4 wt% produced excellent thixotropic, viscoelastic, and shear thinning behavior in the slurry. By using a fiber nozzle angle of 60° and a nozzle diameter of 1.55 mm, the slurry effectively filled the gaps between the fiber bundle and matrix, reducing the number and size of pores in the SiC matrix. These improvements greatly enhance the density, strength, and fracture toughness of the Cf/SiC composites. Therefore, this research demonstrated that optimizing the printing parameters not only improved the structural accuracy of the printed bodies but also greatly enhanced the properties of the ceramic matrix composites.

Al2O3 fiber-reinforced MAX phase ceramic matrix composite

In the aerospace industry, lightweight can reduce the weight of the engine and improve the thrust-weight ratio of the engine. Ceramic matrix composites have attracted widespread attention in the industry due to their much lower density compared to high-temperature alloys and excellent high-temperature performance. SiC fiber-reinforced SiC ceramic matrix composites are the most outstanding representatives, but their long manufacturing cycle and high manufacturing costs limit their widespread use. Ti2AlC is a new type of ceramic material with the characteristics of low density, high melting point, high-temperature resistance, oxidation resistance, and corrosion resistance of ceramic materials, as well as the conductivity and machinability of metals. However, its mechanical properties are slightly inadequate. The use of chopped fibers for toughening can compensate for these deficiencies to a certain extent and improve mechanical properties. This article first explored the influence of various process parameters on the mechanical properties of pure-phase Ti2AlC ceramic materials in SPS preparation technology and then prepared Ti2AlC composites reinforced with 10 vol%, 20 vol%, and 30 vol% Al2O3 chopped fibers. The results showed that the samples prepared at 1300 °C, 40 MPa, and 10 min had a flexural strength of 697 MPa and a fracture toughness of 9.83 MPa m1/2 when the volume ratio of the reinforcement phase was only 10 vol%, which was the same as that of the continuously fiber-reinforced SiCf/SiC composites. This study showed that the MAX phase matrix composites reinforced with chopped fibers have the potential to become high-temperature structural materials by adjusting the composite composition and optimizing the preparation process.

Experimental investigation of probabilistic failure of SiC/SiC composite tubes under multiaxial loading

This paper presents an experimental investigation of the failure behavior of SiC fiber-reinforced SiC matrix (SiC/SiC) composite tubes under multiaxial loading. A new testing apparatus is designed to independently apply axial stress and internal pressure to SiC/SiC tubes. Acoustic emission (AE) is used to monitor the damage growth in the specimen. Based on the measured stress–strain response, a strain-based criterion is proposed to determine the proportional limit stress (PLS). The proposed strain-based criterion is compared with the PLS determined by the AE measurement. The PLS is determined for different loading ratios to form a multiaxial failure surface. By testing multiple replicates, the statistical variations of the PLS are determined. Based on the experimental results, a mathematical model is developed to characterize the probability distribution of the PLS of SiC/SiC composites under multiaxial loading.

Fatigue behaviour of Kevlar/carbon/basalt fibre-reinforced SiC nanofiller particulate hybrid epoxy composite

Abstract It is vital to conduct research on the behaviour of natural fibre composites under cyclic loading in order to have confidence in the mechanical durability. During this study, the fabrication of composite laminates will be carried out by the hybridization effect of natural and synthetic fibres. Quantifying the impact that the SiC filler (10, 20, and 30 g) has when combined with the fibre reinforcement and epoxy matrix (275 g) under cyclic loading circumstances and determining the significant sequence of hybrid composites are the goals of this research. The results of the tensile mode were used to determine the input parameters, and based on the tensile strength of the hybrid composite, 70% of the tensile strength was fixed at 3 Hz frequency as the input for fatigue analysis. The life span was then determined for the hybrid composite. The results of this fatigue test showed that increasing the amount of SiC nanofillers produced a very high potential output for the fatigue test. As a result of increasing the amount of silicon carbide fillers from 10 to 30 g, sample S3 was able to significantly tolerate 65% more life. Failure mode can be identified from scanning electron microscope analysis revealing the major porosity, matrix crack, and laminate bonding strength that causes the failure during fatigue analysis.

Influence of fiber surface properties of SiCf/SiC composites on the interfacial debonding behavior

SiC fiber-reinforced SiC matrix composites (SiCf/SiC) containing BN interphase were fabricated via CVI and MI. For fiber-treated SiCf/SiC composites, cracks that initiate in the matrix tend to deflect between the fiber and the BN interphase when it reaches the fiber/matrix region, and the interface debonding and sliding occurs between the BN interphase and the matrix when fibers are pulled out. The mechanical properties of fiber-treated SiCf/SiC composites are significantly improved. The roughness and chemical properties are analyzed for the treated and as-received SiC fibers. The relationship between the surface chemical composition and roughness of fibers and the fiber/interphase adhesion force is discussed. The composites prepared from the treated fibers are confirmed to have stronger fiber/interphase adhesion force, which is caused by the improvement of surface roughness, the decrease of SiO2 on the fiber surface, and the interinfiltration of BN and excess C on the treated fiber surface.

Investigations on the oxidation behavior and removal mechanism of SiC/SiC composites by multi-pulse femtosecond laser ablation

SiC/SiC (SiC fiber-reinforced SiC matrix) composites have superior performance, making them promising candidates as one of the best materials for high-temperature components in aerospace applications. This investigation analyzed the morphology, structure, composition, and plasma state of multi-pulse femtosecond laser ablated SiC/SiC composites from multiple perspectives using various static and in situ characterization methods. Further, the oxidation behavior and removal mechanism of SiC/SiC composites were studied qualitatively and quantitatively. The results indicated that the ablation products of multi-pulse femtosecond laser ablation of SiC/SiC composites were mainly SiO2 and plasma deposits. The heat accumulation effect and oxidation degree at the ablation locations were enhanced accordingly as the effective ablation number or energy density increased, and the main shape of the products also changed regularly. At the same time, the material removal mechanism changed from non-thermal removal dominated to the equilibrium stage and then to thermal removal dominated. The detailed analysis of the oxidation behavior of each component in SiC/SiC composites enabled the controlled ablation of femtosecond lasers targeting the oxidation process of SiC/SiC composites. Besides, 1 MPa N2 could improve the processing efficiency of femtosecond laser for the depth and width of the groove by a maximum of about 90.40% and 104.02% in this study, respectively. Ultimately, the range of laser process parameters corresponding to multi-pulse femtosecond laser ablation of SiC/SiC composites without thermal removal as dominant was determined.

Microstructure and mechanical properties of C/SiC-niobium alloy (C103) joint brazed with TiCuAg alloy for aerospace applications

In this study, niobium-based alloy C103 is joined to carbon fibre-reinforced SiC (C/SiC) composite utilising commercially available Ticusil® and Cusil® alloy braze filler material. Various characterisation techniques are employed to investigate the interfacial microstructures and evolution mechanism of C/SiC–C103 junctions. Lap shear strength (LSS) is used to evaluate the mechanical performance of the brazed joints. The results show that adding Ti promotes the growth of “nails”, a phenomenon favourable for robust joint quality. However, high Ti content deteriorates the bond strength due to the formation of significant brittle intermetallic phases, causing premature delamination of the joints. The response surface methodology (RSM) is employed to examine the interactions among various operating parameters. To attain the high LSS value, the high temperature, intermediate reaction time, and low cooling rate are necessary for a Ticusil-based joint, whereas high temperature, low reaction time, and increased cooling rate are preferred for a Cusil-based joint.

Multi-scale Progressive Damage and Failure Behavior Analysis of Three-Dimensional Winding SiC Fiber-Reinforced SiC Matrix Composite Tube

Multi-scale Progressive Damage and Failure Behavior Analysis of Three-Dimensional Winding SiC Fiber-Reinforced SiC Matrix Composite Tube

Influence of post heat treatment on the high-temperature performances of multi-layered thermal/environmental barrier coatings on SiC-based composites

Multi-layered LaMgAl11O19/Yb2Si2O7/Yb2Si2O7–Si/Si (LMA/YbDS/YbDS–Si/Si) thermal/environmental barrier coatings (T/EBCs) on SiC fibre-reinforced SiC ceramic matrix composites (SiCf/SiC–CMCs) were subjected to post heat treatment at 1200 or 1350 °C for 5 h. The thermal cycling and water-vapour/oxygen corrosion of the multi-layered T/EBCs after annealing at different temperatures were studied. The results showed the thermal cycling lifetime of the 1350 °C-annealed T/EBCs was shorter than those of the 1200 °C-annealed and as-sprayed T/EBCs, while the 1350 °C-annealed T/EBCs exhibited relatively outstanding resistance to steam corrosion. The degraded thermal cycling lifetime may be associated with horizontal cracks generated at the interfaces of the LMA and YbDS layers after annealing at 1350 °C, which weakened the bonds between the coating layers. The outstanding resistance to steam corrosion of the 1350 °C-annealed T/EBCs could be attributed to the formation of a Yb3Al5O12 reaction layer with low-oxygen permeability on the upward sides of the YbDS layers in the 1350 °C-annealed T/EBCs. This could reduce the oxidation of Si inclusions within the YbDS layers, leading to less silica volatilisation.

Thermally assisted extrusion-based 3D printing of continuous carbon fiber-reinforced SiC composites

A novel method for the three-dimensional (3D) printing of continuous carbon fiber-reinforced SiC composites is proposed. A thermally assisted extrusion-based 3D printing system was developed to simultaneously print a thermoplastic SiC ink, which exhibited shear-thinning properties at high temperatures and underwent rapid solidification at room temperature, and continuous carbon fiber bundles. The viscosity, thixotropy, and printability of the thermoplastic ink were optimized by varying the content of SiC whiskers. Furthermore, the established correlation between the ink composition, nozzle structure, and printability demonstrated that fiber deviations in filaments could be minimized by selecting an appropriate whisker content and coaxial nozzle. A trade-off between the dimensional accuracy and mechanical properties of the printed materials was achieved by optimizing the ink composition and nozzle structure. Finally, PIP was combined for composite densification; the final specimens exhibited a maximum bending strength of 149.1 ± 8 MPa and fracture toughness of 5.32 ± 0.4 MPa·m1/2.

Characterization of BN interface and its effect on the mechanical behavior of SiCf/SiC composites

The boron nitride (BN) interface of SiC fiber-reinforced SiC matrix (SiCf/SiC) composites was fabricated by chemical vapor infiltration (CVI) using BCl3 and NH3 as precursor. The microstructure and chemical composition of the BN interface were characterized. The influence of the coating thickness on the tensile behavior of SiCf/SiC composites was then evaluated. The BN interface synthesized at 800 °C has a low degree of crystallization and displays a quasi-isotropic microstructure. The ratio of element B to element N is near 1 and the oxygen content is about 10%. Meanwhile, the electron structure of B, N atoms near the SiC fiber surface have more sp2 hybridization state. Increasing the BN interface thickness exerts a critical role in decreasing the interfacial sliding stress which improves the tensile strength and toughness of SiCf/SiC composites. The optimal thickness of the BN interface is about 670 nm and further increasing the thickness exhibits little improvement on the mechanical properties of SiCf/SiC composites.

Compression and thermophysical properties of carbon fiber-reinforced high textured pyrocarbon and SiC dual matrix composites

C/C–SiC composites with high textured pyrocarbon (HT PyC) were fabricated by isothermal chemical vapor infiltration and reactive melt infiltration. The evolution of HT PyC before and after heat treatment at 2100 °C as well as the internal defects of the composites, such as pores and cracks, were characterized. The compression and thermophysical properties of the C/C–SiC composites with 2100 °C heat-treated HT PyC (C–S-21) and C/C composites with 2100 °C heat-treated HT PyC (C–C-21) were studied. The results showed that the compression strength and modulus of C–S-21 were 323.19 ± 11.52 MPa and 4.49 ± 0.13 GPa, which were increased by 58.94% and 125.63%, respectively, compared with those of C–C-21 owing to the smaller number of pores and the higher modulus of SiC and Si, respectively. However, fewer pores and strong interfacial adhesion resulted in the brittle fracture of C–S-21. The thermal conductivity of C–S-21 was 73.56 W/(m·K) and 44.94 W/(m·K) in the XY and Z directions, respectively, which was attributed to the fewer defects and better orientation of the graphitized layer in HT PyC as well as the smaller number of pores.

Additive manufacturing of continuous carbon fiber-reinforced SiC ceramic composite with multiple fiber bundles by an extrusion-based technique

Due to the high cost, complex preparation process and difficulty in structural design, the traditional methods for carbon fiber-reinforced SiC ceramic composite preparation have great limitations. This paper presents a technique for the additive manufacturing multiple continuous carbon fiber bundle-reinforced SiC ceramic composite with core-shell structure using an extrusion-based technique. A conventional nozzle system was modified to print simultaneously a water-based SiC paste with continuous carbon fibers. Different levels of binder contents were investigated to optimize the stickiness, viscosity, thixotropy and viscoelasticity of the paste. After sintering, SiC whiskers were generated on the surface of fiber, which is conjectured to be due to the reaction between SiO and carbon fiber at high temperature. The continuous carbon fiber-reinforced SiC ceramic composite exhibited non-brittle fracture. The flexural strength of the additively manufactured Cf/SiC composites improved from 162 MPa with no fiber bundles to a maximum of 219 MPa with three fiber bundles.

In-situ CT characterization of 2D woven SiCf/SiC composite loading under compression

Abstract SiC fiber-reinforced SiC matrix composites (SiCf/SiC) with 2D woven fabric as preform were tested under compression with in-situ X-ray computed tomography. The microstructure and damage evolution of the material under continuous loading levels were accurately revealed by image reconstruction of CT data. There were inhomogeneous pores in SiCf/SiC composite because of the un-uniform fiber distribution in the preform. The result also showed that 2D woven SiCf/SiC composite had obvious non-linear characteristics by its compressive load–displacement curve, and the damage modes included transverse matrix cracking, interlayer cracking, longitudinal matrix cracking, and fiber bundle fracture. Matrix cracking tended to occur near the pores or holes of the material, and the number of longitudinal cracks was relatively high compared to the number of transverse cracks.

Microstructure and Mechanical Properties of Unidirectional, Laminated Cf/SiC Composites with α-Al2O3 Nanoparticles as Filler.

The effects of an α-Al2O3 nanoparticle filler in the SiC matrix on the mechanical properties and failure mechanism of the unidirectional, laminated carbon fiber-reinforced SiC composites were investigated in this work. First, α-Al2O3 nanoparticles were added to the carbon fiber bundles using a slurry impregnation method, and then the Cf/SiC composite with an α-Al2O3 nanoparticle filler (Cf/SiC-Al2O3) was fabricated using a precursor infiltration and pyrolysis method. The microstructure of the Cf/SiC-Al2O3 composite showed chemical compatibility between the α-Al2O3 and the pyrolysis SiC. The Cf/SiC-Al2O3 composite with a low porosity of ~6.67% achieved a good flexural strength of 629.3 MPa and a good fracture toughness of 25.2 MPa·m1/2. The interlaminar shear strength of the Cf/SiC-Al2O3 composite was 11.7 MPa. The SiC-Al2O3 matrix also presented a considerable Young’s modulus of 138.2 ± 8.66 GPa and hardness of 10.3 ± 1.03 GPa. Further analysis indicated that the good mechanical properties with the addition of an α-Al2O3 filler were not only related to the dense matrix and the improvement of the mechanical properties of the matrix. They also originated from the thermal residual compressive stress in the SiC matrix close to the α-Al2O3 nanoparticles caused by the thermal expansion mismatch, which could reflect and close the cracks in the matrix. The findings of this study provide more methods for designing new composites exhibiting a good performance.

Preparation of carbon fiber-reinforced SiC ceramics by stereolithography and secondary silicon infiltration

Stereolithography is an extremely effective three-dimensional (3D) printing technology for the rapid fabrication of high-precision, complex-shaped, and large-scale SiC-based ceramic composites. The combination of photopolymerization-based additive manufacturing and liquid silicon infiltration (LSI) process has been widely used for fabricating lightweight and high-strength carbon fiber-reinforced SiC (Cf/SiC) ceramic matrix composites. However, the fracture toughness of Cf/SiC ceramics prepared by LSI is generally low due to the erosion of carbon fibers by liquid silicon. In this study, we propose a novel fabrication route for Cf/SiC composites by introducing SiC-protected carbon fibers in the photosensitive SiC slurry to prevent the erosion of carbon fibers during the LSI. The fracture toughness of the composites is significantly improved due to the addition of carbon fibers, and it is also much better than the previously reported value for Cf/SiC ceramics. Overall, this study provides an effective strategy for the refined and mass production of ceramic matrix composites.