Fiber-reinforced Ceramic Matrix Composites Research Articles

Theoretical model to predict the fracture strength of fiber-reinforced ceramic matrix composites at elevated temperatures

The mechanical properties of ceramics and their composites in extreme environments, especially the fracture strength under high-temperature conditions, are key factors in assessing the safety and reliability of equipment. In this study, a temperature-dependent theoretical model is proposed with the aim of predicting the fracture strength for fiber-reinforced ceramic matrix composites at elevated temperature environments. This model encompasses not just the collective effects of various factors, including the Young's modulus of both fibers and matrix, the fiber volume fraction, and the melting point of the matrix, but also integrates the evolution of the Young's modulus of the fiber and matrix with temperature. Through the validation of multiple sets of experimental results, it is shown that the proposed model is able to predict the fracture strength of composites at elevated temperatures more accurately without conducting any high-temperature destructive tests. This model can help engineers and scientists to evaluate the mechanical properties of fiber-reinforced ceramic matrix composites at high temperatures more conveniently, thus guiding the optimal design and practical application of the materials, and thus improving the reliability and safety of the materials.

Multi-physics coupling numerical simulation of variable porosity in reactive melt infiltration process

Abstract The hypersonic craft necessitates significant advancements in thermal shielding to safeguard against the extreme aero-thermal environments encountered during flight at hypersonic speeds in near space or upon reentry from space. Carbon fiber-reinforced ceramic matrix composites (FRCMCs) have attracted increasingly interesting attention as advanced structural materials for application in thermal protection. The reactive melt infiltration (RMI) process is preferred for the preparation of FRCMCs because of its low cost and short processing time. However, the RMI process includes the complex interplay of melt flow, reaction dynamics, and thermal fields, with existing models failing to accurately predict these processes due to their uncoupled nature and neglect of pore structure changes. This study introduces a coupled model that integrates mass transfer flow, chemical reaction, and heat transfer, incorporating variable pore structures to more accurately evaluate the RMI process. This approach allows for a comprehensive assessment of internal pressure, temperature, and porosity changes during silicon infiltration into porous media, marking an improvement over the previous model. The model has been validated for use in predicting the exotherm of RMI processes. In conclusion, this coupled model presents a promising avenue for enhancing the fabrication of FRCMCs, either considering the melt infiltration from multiple locations in the RMI process or adjusting the pore structure at the infiltration location to larger pores.

Material removal and damage formation mechanisms induced by periodic indentation during ultrasonic vibration-assisted scratching of SiCf/SiC composites

Fiber-reinforced ceramic matrix composites (CMCs) exhibit high hardness, brittleness, heterogeneity, and anisotropy. This study explores the material removal and damage formation mechanisms during ultrasonic vibration-assisted scratching of SiCf/SiC composites through experimental and micro-finite element simulations. The research reveals that high-frequency periodic indentation-separation of abrasive grain influences stress transfer and crack propagation, which are affected by the interfacial layer and fiber orientation. Crack deflection plays a crucial role in material removal and determines the amplitude of normal scratching force. Stress transfer interference primarily governs damage formation, with more severe damage occurring along the longitudinal and transverse fiber directions due to secondary stress concentration and crack deflection. In contrast, scratching along the perpendicular fiber direction requires higher normal forces due to residual adjacent phase materials, but results in more controlled material removal and less damage. The study provides insights into optimizing the ultrasonic vibration-assisted machining of CMCs to minimize damage.

Study on ultrasonic elliptical vibration-assisted grinding mechanism and surface quality of C/SiC composite material

2.5D C/SiC composites have excellent mechanical properties and broad application prospects in the aerospace field. This study investigates the ultrasonic elliptical vibration-assisted grinding mechanism of 2.5D C/SiC composites in different structural directions. A surface roughness prediction model considering abrasive grain protrusion height, brittle-plastic transition of materials and the influence of ultrasonic vibration is established. Experimental results show that material removal involves matrix and fiber fracture, fiber pullout and interface debonding. Ultrasonic vibration causes intermittent cutting, producing finer chip particles and numerous cross microgrooves, reducing subsurface damage. The roughness prediction model is in good agreement with the experimental trend. When the grinding speed is increased from 1 m/s to 8.9 m/s, the surface roughness Ra is reduced by 30.1 %. When the feed speed is increased from 50 mm/min to 650 mm/min, the surface roughness Ra is increased by 47.6 %. When the grinding depth is increased from 0.01 mm to 0.04 mm, the surface roughness Ra is increased by 53.2 %. This study provides a reference for efficient and low-damage processing of fiber-reinforced ceramic matrix composites.

The Influence of the Interface on the Micromechanical Behavior of Unidirectional Fiber-Reinforced Ceramic Matrix Composites: An Analysis Based on the Periodic Symmetric Boundary Conditions

The long-term periodicity and uncontrollable interface properties during the preparation process for silicon carbide fiber reinforced silicon carbide-based composites (SiCf/SiC CMC) make it difficult to thoroughly investigate their mechanical damage behavior under complex loading conditions. To delve deeper into the influence of the interface strength and toughness on the mechanical response of microscopic representative volume element (RVE) models under complex loading conditions, in this work, based on numerical simulation methods, a microscale representative volume element (RVE) with periodic symmetric boundary conditions for the material is constructed. The phase-field fracture theory and cohesive zone model are coupled to capture the brittle cracking of the matrix and the debonding behavior at the fiber/matrix interface. Simulation analysis is conducted for tensile, compressive, and shear loading as well as combined loading, and the validity of the model is verified based on the Chamis theory. Further investigation is conducted into the mechanical response behavior of the microscale RVE model under complex loading conditions in relation to the interface strength and interface toughness. The results indicate that under uniaxial loading, increasing the interface strength leads to a tighter bond between the fiber and matrix, suppressing crack initiation and propagation, and significantly increasing the material’s fracture strength. However, compared to the transverse compressive strength, increasing the interface strength does not continuously enhance the strength under other loading conditions. Meanwhile, under the condition of strong interface strength of 400 MPa, an increase in the interface toughness significantly increases the transverse compressive strength of the material. When it increases from 2 J/m2 to 20 J/m2, the transverse compressive strength increases by 28.49%. Under biaxial combined loading, increasing the interface strength significantly widens the failure envelope space under σ2-τ23 combined loading; with the transition from transverse compressive stress to tensile stress, the transverse shear strength shows a trend of first increasing and then decreasing, and when the ratio of transverse shear displacement to transverse tensile/compressive displacement is −1, it reaches the maximum. This study provides strong numerical support for the investigation of the interface properties and mechanical behavior of SiCf/SiC composites under complex loading conditions, offering important references for engineering design and material performance optimization.

Phase stability of W-containing high-entropy carbide with silicon addition at high temperatures

Reactive melt infiltration (RMI) is a typical method to produce carbon fiber-reinforced ultra-high temperature ceramic matrix composites (Cf/UHTCs), for which the molten Si is a very general and practical infiltrator. High-entropy carbide (HE-carbide) is a newly developed promising matrix phase of Cf/UHTCs. Understanding the phase equilibrium relation in the HE-carbide and Si reaction system can provide accurate guidance on designing the RMI process for preparing HE-carbide matrix composites with controlled phases and microstructure. This study systematically investigates W-containing HE-carbide and Si addition reactions at high temperatures. Samples with nominal starting compositions of (Ti0.2Zr0.2Hf0.2Ta0.2W0.2)C-xSi (HEC-xSi, x = 2.5, 5 and 10 wt%) are prepared by spark plasma sintering technique at 1500 °C and 1700 °C with an axial pressure of 40 MPa for 10 min. The results show that adding 2.5 wt% or 5 wt% Si removes carbon from the HEC matrix, forming SiC and stable equimolar (Ti0.2Zr0.2Hf0.2Ta0.2W0.2)C1-x phase with carbon deficiency at high temperatures. In contrast, besides the SiC phase, the addition of 10 wt% Si in the HEC matrix may form unstable transient phases of (Ti0.2Zr0.2Hf0.2Ta0.2W0.2)C1-x with supersaturated carbon deficiencies at high temperatures, which finally decomposes into non-equimolar HE-carbide (Ti0.2Zr0.2Hf0.2Ta0.2W0.2-y)C1-z and metal silicide WSi2 phases. The effects of the HEC and Si reactions on the microstructure evolution of the samples during sintering are discussed. Meanwhile, the mechanical properties of the samples with the reaction resulting microstructure are measured and briefly discussed.

In-plane shear failure behavior and mechanical properties of SiC/SiC Composites

Fiber-reinforced ceramic matrix composites, especially SiC/SiC composites, have the characteristics of lightweight, high strength, high-temperature resistance, etc., which are ideal structural candidates for aerospace vehicle components, in-plane shear performance is one of the important indicators to characterize the mechanical properties of materials and component assessment, this paper designs and processes the in-plane shear test pieces and test devices and methods to study the shear mechanical behavior under the mechanical properties and failure behavior of SiC/SiC ceramic-based fiber bundle composites are studied under shear mechanical behavior. The results show that matrix cracking and fiber fracture are the main failure modes, and there are two obvious phases in the specimen shear force-displacement curves, and fiber fracture is the main cause of strain in the specimen.

Microstructure, properties and damage characteristics of designed PyC interphase in Cf/SiC mini-composites

Pyrolytic carbon (PyC) interphase plays a crucial role in improving the mechanical properties of fiber-reinforced ceramic-matrix composites (FRCMCs). In this paper, three groups of PyC interphase were prepared: the first group (G1) with a mid-high texture PyC (MT-HT-PyC) interphase, the second group (G2) with a low/high texture combination PyC (LT/HT-PyC), and the third group (G3) with a low texture PyC (LT-PyC). The microstructure, intrinsic properties and interfacial properties of these three groups PyC interphase were characterized by SEM, TEM, Raman spectroscopy, nanoindentation tests, and fiber push-in tests. The result showed the LT-PyC with more amorphous PyC lattice and lattice defects is able to reduce the indentation modulus and interfacial properties of PyC interphase. The uniaxial tensile tests revealed that the Cf/SiC mini-composites containing a LT-PyC interphase could significantly improve their tensile strength, exhibiting a 34 % enhancement in tensile strength compared to those counterparts without LT-PyC interphase. The experimental result of scanning ion beam etching (SIBN) also showed that the interfacial crack propagates primarily within the LT-PyC interphase, rather than along the interface between the fiber and the interphase.

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.

Micromechanical analysis of fiber-reinforced ceramic matrix composites by a geometrically nonlinear hierarchical quadrature element model

The stress fields of fiber-reinforced ceramic matrix composites (CMCs) under longitudinal tension are predicted using a non-linear hierarchical quadrature element method (HQEM) in this work. The HQEM combines the differential quadrature method (DQM) with the hierarchical finite element method (HFEM), which is a typical p-version finite element method (FEM). High-order interpolation functions of the HQEM allow accurate evaluation of stress distribution. Fiber, matrix, and interfaces of the CMCs are modeled as linear elastic materials that may have large displacements. The nonlinear HQEM estimation of CMCs stress distributions are validated by comparing with analytical results obtained using classical BHE shear-lag model. Stress distribution in three characteristic stages in the damage evolution process, namely, interface perfectly bonded, interface debonding, and fiber failure are investigated. It is shown that when fiber failure happens, geometric non-linearity must be considered to avoid excessive stress concentration. Furthermore, the stress distribution within three-dimensional cylindrical CMCs cell is studied, which sheds light on the future exploration of three-dimensional CMCs analyses.

High-temperature transient-induced thermomechanical damage of fiber-reinforced ceramic-matrix composites in supersonic wind tunnel

This article is based on the supersonic directly connected wind tunnel. Through a specially designed experimental chamber, combined with infrared temperature measurement, high-speed camera, etc., in-situ monitoring of composite materials under airflow at Ma 3.0 with a total temperature of 950 ∼ 1473K was carried out. The dimensional analysis method was used to propose dimensionless parameters to characterize the thermal coupling caused by high-speed airflow thermal shock. Research has shown that the thermal coupling effect of supersonic airflow causes uneven temperature inside the material, and the thermal stress caused by temperature gradient changes (including increasing and decreasing processes) is the main reason for material damage. The damage of ceramic matrix composites under thermal shock mainly manifests as a decrease in surface roughness, surface fiber fracture and a decrease in elastic modulus. In addition, the study also found that there are damage thresholds for the thermal shock effect of airflow at different total temperatures, which helps to further understand the thermomechanical damage mechanism and degradation law of composite structure under high-temperature transient conditions.

Fracture mechanism of ultrasound-assisted scratching 2D-SiCf/SiC composite fibers with different fiber orientations

The aim of this paper is to investigate the grinding characteristics and mechanism of 2D- SiC/SiC composites with 0°/90° orthogonal anisotropic structured surfaces under different scratching fiber angles (angle between scratch direction and fiber orientation, SFA). A series of surface single abrasive scratching tests were conducted. The effects of the scratch fiber angle on the grinding force, surface morphology and roughness were investigated. The results show that the scratch force and surface roughness at different scratch fiber angles are in the order of 0° > 30°> 45°; SFA also has an important effect on the surface microstructure. The grinding mechanism of 2D-SiCf/SiC composites was analyzed by single-particle scratching test. The results of the scratch force and surface morphology provide strong evidence of the differences produced during the grinding process. The advantages of ultrasonic vibration over conventional machining were further identified by comparing specific scratch energies. This study elucidates the damage behavior of 2D-Sicf/sic composites in correlation with the influence of angle, and these results provide a new guideline for ultrasonic vibratory grinding of woven fiber-reinforced ceramic matrix composites for machining quality.

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.

Effect of interphase layer on matrix cracking in fiber reinforced ceramic matrix composites

The onset of matrix steady-state cracking stands as a pivotal mechanical characteristic in fiber reinforced ceramic matrix composites (FRCMCs), garnering substantial attention and investigations. Experimentally, it has been demonstrated that increasing interphase layer thickness may cause non-monotonic changes in matrix cracking stress. However, the existing models can hardly elucidate this phenomenon thoroughly due to the neglect of interphase thickness. This paper presents a comprehensive analytical model for the matrix cracking incorporating interphase, the Poisson effect, Coulomb friction, fiber asperities, residual thermal stress (RTS), and their coupling effects, along with a modified criterion for interfacial debonding that accounts for the presence of the axial RTS. Based on the proposed model, three distinct cracking domains, i.e., perfectly bonded, debonding with and without interfacial separation, have been identified with the critical conditions deduced analytically. Thereby the mechanism of the non-monotonic influence of interphase thickness is thoroughly revealed as the transition of cracking modes. Meanwhile, the role of interphase on the matrix cracking is systematically studied, and the results indicate that interphase has a notable effect through relieving axial RTS, adjusting interfacial friction, altering interfacial shear modulus, and influencing debonding toughness. The outcomes of this study offer valuable guidance for the interphase design of FRCMCs.

Effect of fiber roughness on interfacial friction of fiber reinforced ceramic matrix composites

Interfacial friction plays a crucial role on mechanical behaviors of fiber reinforced ceramic matrix composites (FRCMCs), such as matrix cracking, damage evolution, and fracture, and the fiber surface roughness has been shown to enhance the interface friction. However, the influence of interphase thickness and residual stress on the friction enhancement of fiber roughness was neglected in previous works. Therefore, in this paper a thoroughly theoretical model is established and the additional radial stress is derived to intuitively reflect the contribution of fiber roughness to the interfacial friction. The results indicate that the interfacial friction can usually be enhanced by increasing the fiber roughness and reducing the interphase thickness, which however is severely overestimated by more than 5 times by the previous models. Moreover, the residual stress and fiber axial stress have a nonnegligible effect on the contribution of fiber roughness. For a given fiber axial stress, the residual stress that is too large or too small will weaken or even eliminate the contribution of fiber roughness, and only when the residual stress is within a proper range, can the fiber roughness play an effective role. On the other hand, for a given target load and ambient temperature, a critical fiber roughness that can enhance the interfacial friction is analytically derived. This work can provide valuable insights into the design of fiber roughness and interphase thickness for FRCMCs.

Effect of thermo-mechanical and low-cycle preloading on the strength of carbon fiber-reinforced ceramic matrix composites

Fiber-reinforced ceramic matrix composites (CMCs) exhibit excellent thermo-mechanical properties including outstanding resistance against damage and fatigue. Some CMCs show occasionally even a strength enhancement after fatigue, often interpreted with relieve of internal stresses and interfacial degradation. This study reports the influence of low-cycle thermo-mechanical preloading on the bending and tensile strength of carbon fiber-reinforced silicon carbon (C/C-SiC). For this purpose two C/C-SiC materials with the same fiber architecture but different assumed internal stress states were subjected to single and cyclic mechanical preloads up to 90% of their ultimate strength level at room temperature and at 350 °C. Statistical evaluations of the experiments show that the ultimate strength values were surprisingly unchanged after preloading. The results are discussed regarding the thermal residual stresses (TRS).

The oxide-layer configuration alteration and pseudo-ductile crack propagation mechanisms in composites induced by different relative thicknesses of CVI HfC-SiC multiphase matrix

Carbon fiber-reinforced HfC-SiC ceramic matrix composites (Cf/HfC-SiC) with different HfC-SiC matrix thicknesses were prepared by the chemical vapor infiltration method. The microstructure, ablation, and pseudo-ductile fracture behaviors of the composites were studied. The results proved that with the change of the HfC-SiC layer relative thickness, the oxide-layer configuration changed to promote its densification, which improved the ablative protection and mechanical properties of Cf/HfC-SiC composites. After ablation, when the relative volume proportion of the HfC-SiC matrix was the utmost (24.7/15.5), the composites had the best ablation resistance due to the tubular lamination configuration HfO2 layer. This caused the composite to have the highest residual bending strength (215.8 MPa) and strength retention rate (79.7%). In addition, a pseudo-ductile crack propagation model was established to determine the influence of the induction of residual stress and the relative HfC-SiC layer thickness on the fracture behavior in the composites. Results suggested that in the real crack deflection mechanism, due to the induction of residual stress, the stress state in the HfC-SiC matrix with the increase of the HfC layer thickness changed to form more ring deflection cracks at the HfC/SiC interface. It provides a way to study the pseudo-ductility behavior of multiphase matrix composites and explain the improvement of its predictability and failure.

Single-grain scratching of SiCf/SiC composite under minimum quantity lubrication: Force and material removal mechanism study

As one of the most novel fiber-reinforced ceramic matrix composites, SiCf/SiC composites are difficult to be processed machine materials. On top of that, the underlying material removal mechanism not yet completely understood. Along these lines, in this work, single-grain scratching orthogonal tests with different MQL methods were carried out to systematically analyze the influence of the different processing directions and lubrication methods on the material removal lubrication mechanism and the scratching force in the scratched surfaces. From the acquired results, it was demonstrated that the scratch force was the smallest when the processing direction is was 0° to the fiber direction. In addition, the utilization of MQL from vegetable oil can effectively reduce the cutting force. Diamond indenter caused significant damage to the surface of SiCf/SiC composites when the machining direction was 90° to the fiber direction, while narrow but deep grooves on the surface were observed when the angle was 0°. The dominant mode of material removal of SiCf/SiC composites was a brittle fracture, and the damage features mainly included direct fiber breakage, matrix fragmentation, fiber pullout, and fiber outcropping. The increase of the processing ratio of 0° and implementation of vegetable oil for MQL was proven as one of the best methods.

Fine study of hierarchical interphase constructed by Ti3SiC2 and carbon nanotubes in SiCf/SiC composites

The interphase in silicon carbide fiber-reinforced silicon carbide ceramic matrix composites (SiCf/SiC) assumes a significant role in the mechanical properties exhibited at elevated temperatures. The strength, toughness, and chemical stability of a composite is frequently influenced by the optimization of its interphase. In this work, the MAX phase (Ti3SiC2) and carbon nanotubes (CNTs) were successively deposited on the SiCf using the molten salt method and chemical vapor deposition technique, respectively, to create a hierarchical structure. Transmission electron microscopy was employed to undertake a comprehensive investigation of the interfacial component in SiCf/SiC composites. The detailed study of interphases in SiCf/SiC composites has been conducted through the analysis of crystallization, the bonding natures, and the micromorphology, encompassing geometry and constituent characteristics. A bilayer consisting of TiC–Ti3SiC2/Ti5Si3 and a vertical array of carbon nanotubes (CNTs) with a length of 7 μm is fabricated on the surface of SiCf/Ti3SiC2-CNTs. The SiCf/Ti3SiC2/SiC and SiCf/Ti3SiC2-CNTs/SiC composites exhibit lamellar structures of Ti3SiC2, which indicates a further crystallization of Ti3SiC2 resulting from the formation of SiC matrix by PIP procedure. The interphase of SiCf/Ti3SiC2-CNTs/SiC composite may be categorized into four distinct layers: a TiC phase, a TiSi2 phase, a transition phase of TiSi2/TiC, and a Ti3SiC2 phase. This interphase structure is more intricate compared to the interphase structure observed in the SiCf/Ti3SiC2/SiC composite. This research indicates significant value for the future design and optimization of interfaces.

Large-scale material extrusion-based additive manufacturing of short carbon fibre-reinforced silicon carbide ceramic matrix composite preforms

ABSTRACT Large-scale short carbon fibre-reinforced silicon carbide (Csf/SiC) ceramic matrix composites (CMCs) have important applications in the field of aerospace engineering. This study proposed the use of material extrusion based additive manufacturing to fabricate large-scale C sf/SiC CMC preforms. In this paper, we determined how the key material extrusion parameters, including solid loading, nozzle diameter and layer height impact the stability of the additively manufactured C sf/SiC CMCs. The solid loading significantly influenced the stability of the C sf/SiC CMCs, and the slurry with 50 vol.% solid loading was better for additive manufacturing. The layer height played a significant role in the void formation in CMCs. It was appropriate for structure retention to set the layer height as 60–75% of the nozzle diameter. The effect of angle from vertical on the stability of out-of-plane structure was also investigated. When the angle was over 40o, the out-of-plane structure additively manufactured without supports tended to collapse. Large-scale C sf/SiC CMC preforms with out-of-plane structures were finally successfully fabricated. This study is believed to provide some fundamental understanding for the fabrication of large-scale fibre-reinforced ceramic matrix composites.