Ceramic Matrix Composites Research Articles

Analysis of damage mechanisms in fiber-reinforced ceramic matrix composites under thermomechanical loading at intermediate and high temperatures

Analysis of damage mechanisms in fiber-reinforced ceramic matrix composites under thermomechanical loading at intermediate and high temperatures

Reaction bonding of oxide/oxide ceramic matrix composites using aluminum nitride as an alumina precursor

AbstractThe reaction bonding technique offers a promising approach for controlling matrix sintering shrinkage in oxide/oxide ceramic matrix composites (OCMCs), thereby reducing the sintering cracks and enhancing mechanical properties. In this study, aluminum nitride (AlN) was used as an alumina precursor to fabricate OCMCs via reaction bonding. The results indicated that the mechanical properties of the OCMCs could be greatly improved due to the volume expansion induced by AlN oxidation, which reduced sintering cracks, and the high sintering activity of AlN, which enhanced the particle bonding strength in the matrix. However, the strong bonding between the matrix and fibers, attributed to the high sintering activity of AlN, resulted in the decrease of toughness. These findings confirm that the reaction bonding can effectively improve the mechanical properties of OCMCs, but careful control of matrix‐fiber bonding is essential to optimize overall performance.

A statistical representation of bond coating oxidation under environmental barrier coatings

AbstractEnvironmental barrier coatings (EBCs) protect SiC‐based ceramic matrix composites (CMCs) in turbine hot sections from high‐temperature volatilization in combustion gases. The formation of a SiO2 thermally grown oxide (TGO) is expected under the EBC after long‐term operation. The oxidation resistance of the EBC is understood as a life‐limiting factor for the CMC, and this work predicts long‐term oxidation behavior under EBCs through a simple statistical approach. Specimens were exposed to 1350°C isothermal conditions for 100‐h thermal cycles in flowing steam for up to 1000 h. The EBC morphology, SiO2 thickness, and SiO2 cracking behavior were assessed. Using thousands of SiO2 thickness measurements across many millimeters of the interface, a realistic representation of the entire TGO was captured via a lognormal distribution. The lognormal fit parameters were extrapolated out to 25 000 h to assess the degree of SiO2 growth, the spread of SiO2 thicknesses related to the rough oxidizing interface, and percentages of the intermediate bond coating consumed. Local interfacial defects from the coating deposition process are identified as local failure points for EBC—CMC systems.

Improvement of Micro-Hole Processing in SiCf/SiC Ceramic Matrix Composite Using Efficient Two-Step Laser Drilling

SiCf/SiC ceramic matrix composite (CMC), a hard and brittle material, faces significant challenges in efficient and high-quality processing of small-sized shapes. To address these challenges, the nanosecond laser was used to process micro-holes in the SiCf/SiC CMC using a two-step drilling method, including laser pre-drilling in air and laser final-drilling with a water jet. The results of the single-parameter variation and optimized orthogonal experiments reveal that the optimal parameters for laser pre-drilling in air to process micro-holes are as follows: 1000 processing cycles, 0.7 mJ single-pulse energy, −4 mm defocus, 15 kHz pulse-repetition frequency, and 85% overlap rate. With these settings, a micro-hole with an entrance diameter of 343 μm and a taper angle of 1.19° can be processed in 100 s, demonstrating high processing efficiency. However, the entrance region exhibits spattering slags with oxidation, while the sidewall is covered by the recast layer with a wrinkled morphology and attached oxides. These effects are primarily attributed to the presence of oxygen, which enhances processing efficiency but promotes oxidation. For the laser final-drilling with a water jet, the balanced parameters for micro-hole processing are as follows: 2000 processing cycles, 0.6 mJ single-pulse energy, −4 mm defocus, 10 kHz pulse-repetition frequency, 85% overlap rate, and a 4.03 m/s water jet velocity. Using these parameters, the pre-drilled micro-hole can be finally processed in 96 s, yielding an entrance diameter of 423 μm and a taper angle of 0.36°. Due to the effective elimination of spattering slags and oxides by the water jet, the final micro-hole exhibits a clean sidewall with microgrooves, indicating high-quality micro-hole processing. The sidewall morphology could be ascribed to the different physical properties of SiC fiber and matrix, with steam explosion and cavitation erosion. This two-step laser drilling may provide new insights into the high-quality and efficient processing of SiCf/SiC CMC with small-sized holes.

Ultrasonic nondestructive testing for composite bonded structures based on convolutional neural network and bidirectional gated recurrent unit (CNN-BiGRU) optimized by attention mechanism.

New ceramic matrix composites (CMCs) are commonly used as thermal protection materials bonded to the surfaces of aircraft substrates. Defects in composite bonded structures can cause the protective layer to detach from the airframe, seriously endangering aircraft safety. Ultrasonic nondestructive testing is a promising method for detecting defects in multilayer bonded structures. However, the porous nature and strong sound absorption of CMC result in severe attenuation and scattering of ultrasonic detection signals, reducing the signal-to-noise ratio. This makes it challenging to accurately identify real defect signals. Therefore, a novel method combining a convolutional neural network and a bidirectional gated recurrent unit (CNN-BiGRU) optimized by an attention mechanism, along with ultrasonic inspection, is proposed to identify defects in composite bonded structures. The method learns time and frequency domain features of original signals through convolution, applies an attention mechanism to determine the importance of these features, and delivers weighted results to the bidirectional gated recurrent unit network. Then, time and frequency domain features are fused, and a one-dimensional global average pooling layer is employed to reduce model parameters and prevent network overfitting. A nonlinear support vector machine is utilized as the final classifier instead of the traditional softmax classifier. The results indicated that the proposed CNN-BiGRU model surpasses traditional classifiers that require manual feature extraction, achieving an accuracy of 97.70%. The method addresses the limitations of traditional techniques and provides a valuable reference for defect identification in composite bonded structures for practical engineering applications.

Ceramic Repair Agents for Damaged CMC: Assessing Repair Performance

Ceramic Repair Agents for Damaged CMC: Assessing Repair Performance

Improved Thin-Kerf Processing in Cf/SiC Composite by Waterjet-Guided Nanosecond Laser Decreases Oxidation and Thermal Effect

As a hard and brittle material, the processing of Cf/SiC ceramic matrix composites (CMCs) faces significant challenges, especially in the processing of small-sized shapes. To address this challenge, laser processing with gas-assisted nanosecond laser (GNL) and waterjet-guided nanosecond laser (WNL) modes were applied to fabricate thin kerfs in the Cf/SiC composite. The surface morphology, microstructure, and chemical composition of the processed Cf/SiC composite were investigated comparatively. The results revealed that the coupling of helium in the GNL mode laser processing could make full use of the laser energy, but resulted in spattering in the kerf margin and a recast layer in the kerf surface, accompanied by obvious oxidation, while the coupling of the waterjet in the WNL mode laser processing decreased the oxidation significantly and removed the remelting debris, which produced a clear and flat kerf surface. Due to the taper caused by laser energy dissipation, the single-path laser processing in the Cf/SiC composite had a limited depth. The maximum depth of the kerf prepared by single-path laser processing with the GNL mode was about 328 μm, while that with the WNL mode was about 302 μm. The multi-path laser processing with the GNL and WNL modes could fabricate a through kerf in the Cf/SiC composite, but the coupling medium obviously influenced the surface morphology and microstructure of the underlying region. The kerf surface prepared by the GNL mode had a varied surface morphology, which transited from the top layer, covered with oxide particles and some cracks, to the bottom layer, featured with micro-grooves and small oxides. The kerf surface prepared by the WNL mode had a consistently smooth and clean morphology featured with broken carbon fiber and residual SiC matrix. The slow laser energy dissipation and open environment in the GNL mode resulted in a bigger HAZ and relatively serious oxidation, which caused local phase transformation and microstructure degradation. The isolation condition and rapid cooling in the WNL mode decreased the HAZ and restrained the oxidation, almost keeping the original microstructure. The thicknesses of the HAZ in the GNL- and WNL-processed Cf/SiC composite were about 200 μm and 100 μm, respectively. The WNL-processed Cf/SiC composite had a lower oxidation and thermal damage surface, which is instructive for the processing of the Cf/SiC composite.

Advances in the processing of ceramic matrix composites: a review

Advances in the processing of ceramic matrix composites: a review

Feed Cutting Force Analysis Using Discrete Wavelet Transform in Drilling of Aluminium Matrix Composite

This paper presents an analysis of the cutting forces during the drilling of a ceramic fibre-reinforced aluminium matrix composite. The machining was carried out under dry drilling conditions and with minimum lubrication of the cutting zone. The mean values of the feed force and the ratio of this mean to the force amplitude were calculated. This result is the load stability coefficient was thus obtained. The measured force waveforms were decomposed using a discrete wavelet transform in Matlab. An approximation, which is a filtered force waveform, and a detail, i.e. the noise of the measurement, were obtained. The numerical value of noise and interference was calculated from the ratio of load stability after filtration to load stability before filtration. It was found that the use of oil mist lubrication slightly reduces the average value of the feed force during drilling of the tested composite. The interference affecting the force measurement when drilling with MQL is higher, while the type of Daubechies wavelet compactness does not affect the filtration power.

Synergistic enhancement of mechanical properties in silicon carbide composites reinforced with carbon fiber–silicon carbide nanowires

AbstractThis study investigates the synergistic reinforcement effects of carbon fibers (Cf) and silicon carbide nanowires (SiCnw) on the mechanical properties of SiC ceramic matrix composites (CMCs) fabricated via reactive melt infiltration. Cf–SiCnw/SiC composites were prepared by incorporating SiCnw into carbon fiber nonwoven fabrics using a slurry impregnation technique prior to matrix densification. The reinforcement system significantly enhanced mechanical properties through multi‐scale synergistic effects. Compared to conventional Cf/SiC composites without nanowire reinforcement, the optimized composites showed a 24.4% increase in flexural strength (from 327.5 to 407.5 MPa) and a 41.4% improvement in fracture toughness (from 4.13 to 5.84 MPa m1/2). This performance enhancement is attributed to the combined energy dissipation mechanisms of fiber pull‐out and nanowire pull‐out effects, which together establish a multi‐level collaborative reinforcement system. Unlike previous methods of in situ growth for SiCnw incorporation into porous carbon preforms, this work highlights the effectiveness of the slurry impregnation approach in achieving uniform nanowire distribution and demonstrates its potential for optimizing mechanical performance in CMCs.

Woven SiO2f/SiO2 composites quasistatic scratch behavior and damage mechanism considering interface characteristics

AbstractQuasistatic scratch behavior and damage mechanism are basic issues for material removal and damage mechanism for woven SiO2f/SiO2 ceramic matrix composites (CMCs). The single abrasive grain scratching CMC finite element modeling (FEM) is constructed and verified under variable scratch depth by comparing FEM and experimental results. The stress fields for CMC, its matrix, fibers, and interface are analyzed, the stress fields for CMC and its SiO2 matrix continue to expand and are basically consistent as scratch depth increases, and matrix strength field is the main impedance stress field during CMC removal process. Not only is the interface subjected to greater scratching force with increasing scratch depth, but also they extends to other adjacent coupled interfaces and get much greater, microcracks in the matrix diffuse and redirect on the surfaces of fibers and other fibers coupled under the action of scratching force, which results in interface damage and fibers debonding. SiO2 matrix is removed for matrix stress above shear fracture strength, SiO2 fibers are cut off for fibers stress above shear fracture strength. Damage morphology and modes are obviously different in areas between weft‐containing and warp‐containing CMC during scratching process.

Performance Optimization of SiO2f/SiO2 Composites Derived from Polysiloxane Ceramic Precursors.

In this paper, polymethylhydrosiloxane (PMHS) and ethanol were used as raw materials to synthesize the ceramic precursor of side ethoxy polysiloxane (PESO) using dehydration and a dealcoholization reaction, which had a ceramic yield of 87.15% and a very low residual carbon content. With the quartz fiber as a reinforcer, the silica matrix composites (SiO2f/SiO2) with a double-layer interface (PyC-SiO2/BNNSs) coating were manufactured using precursor impregnation pyrolysis (PIP). The as-prepared SiO2f/SiO2 possessed an excellent mechanical property, which exhibited obvious fiber pull-out and debonding phenomena from a fracture morphology. The flexural strength and fracture toughness of SiO2f/SiO2 reached 63.3 MPa and 2.52 MPa·m1/2, respectively. Moreover, the SiO2f/SiO2 had suitable dielectric properties, with a dielectric constant of about 2.5 and a dielectric loss of less than 0.01. This work provides an important concept for the enhancement of the dielectric properties and mechanical properties of quartz fiber-reinforced ceramic matrix composites, as well as in the preparation of wave-transmissivity composites.

A Finite Element Analysis Framework for Assessing the Structural Integrity of Aero-Engine Ceramic Matrix Composite Component Coatings

Ceramic Matrix Composites (CMCs), and, in particular, SiC/BN/SiC, are currently being investigated to replace Nickel alloys in the manufacturing of aero-engine high-pressure turbine system components. Although superior to traditional metallic solutions in terms of resistance to high temperatures, CMCs are prone to oxidation and environmental degradation. For this reason, a multi-layer coating system is used to protect the CMC substrate. The aim of this paper is to define a Finite Element (FE) thermo-mechanical procedure to assess the integrity of the multi-layer coating. Among the four main failure mechanisms, vertical transverse cracking (denoted as “mud cracking”) and the thermally grown oxide (TGO) formation were numerically investigated. The FE (Finite Elements) procedure described in this paper, fully automated with the auxilium of MATLAB and Abaqus, is holistic and offers a simplified tool for the preliminary lifing of coating systems. TGO growth in the bond layer leads to the failure of the coating after 15,200 h, when its thickness reaches 0.02 mm, circa 20% of the bond layer (BND), and the stiffness and the strength of the BND drop to zero. The procedures and outcomes from the work are relevant for aero-engine designers and system engineers.

Growth rate of crack opening displacement in ceramic-matrix composites: Theory and analytical prediction

In this paper, the growth rate of crack opening displacement (COD) in ceramic-matrix composites (CMCs) was investigated using the micromechanical approach. Two damage states of interface partial and complete debonding were considered in determining the CODs and growth rate of CODs considering synergistic effects of fiber bridging and broken. Experimental CODs and growth rate of CODs in SiC/SiC minicomposites with low and high fiber contents were predicted using the developed micromechanical model. Effects of composite constitutive properties, e.g., fiber volume fraction, interface properties and fibers properties, and damage state (i.e., the matrix crack spacing) on the growth rate of CODs and internal damages (e.g., interface debonding ratio and fibers failure probability) were discussed. Relationships between the CODs, growth rate of CODs, and interface debonding ratio were established.

Anomalous Temperature-Dependent Interfacial Thermal Resistance Due to Melting.

Ceramic composites are essential materials for high-performance applications in aerospace, defense, and other industries requiring high-temperature structural components and thermal barrier coatings. However, the understanding of heat transport processes at elevated temperatures, particularly at heterogeneous interfaces, remains in its early stages. In this study, we simulate the thermal transport properties of SiC/Si interfaces at various temperatures and uncover an unexpected anomaly. At high temperatures, the interfacial thermal resistance initially remains stable (consistent with the Acoustic Mismatch Model, AMM) but then decreases anomalously as temperature rises, which finally reaches a plateau as temperature further increases. This behavior results from the interplay between two factors: the gradual melting of Si, which increases the phonon density of states overlap between SiC and Si at the interface, and the gradual reduction in the structure factor of Si due to loss of long-range order. These effects together drive the reduction and subsequent plateau in thermal resistance at the heterogeneous interface in extreme high-temperature conditions. Our findings provide new insights into the complex role of interfacial melting in ultrahigh-temperature heat transfer and offer a theoretical foundation for the design and optimization of ceramic matrix composites for next-generation thermal management solutions in extreme environments.

Fabrication of AlMgB 14 nanoparticles by high energy ball milling of bulk compound prepared by spark plasma sintering

Aluminum Magnesium Boride (BAM), an intermetallic compound, exhibits exceptional hardness, a low coefficient of friction, low density, high electrical conductivity, and outstanding thermoelectric properties. These characteristics make it a promising candidate for applications in semiconductors, as a reinforcing agent in metal and ceramic matrix composites, and as a wear-resistant coating across a wide range of temperatures. In this work, BAM nanoparticles were prepared by high-energy ball milling of constituent as a solid-state route. BAM was synthesized by spark plasma sintering of Al 12 Mg 17 intermetallic and B powders. The powders with a stoichiometric ratio were mechanically milled and sintered by SPS (40 MPa/ 1400 °C/ 5 min). It was found that the use of Al 12 Mg 17 intermetallic compound as a precursor (in comparison to the use of elemental Al and Mg) gives a high efficiency (≈92%) to synthesize BAM material with a hardness (27.98 ± 0.9 GPa) and density (2.68 ± 0.002 g/cm 3 ) close to the theoretical values. Finally, the BAM nanoparticles (the mean diameter of 32.4 nm) were successfully obtained by mechanical milling of the bulk sample, for the first time.

Processing and Characterization of Dual Metallic Dual Carbide Ceramic Matrix Composites

Processing and Characterization of Dual Metallic Dual Carbide Ceramic Matrix Composites

Interface Engineering for High Strength and High Toughness Ceramic Matrix Composites.

Ceramics exhibit exceptional strength, hardness, and structural stability, rendering them indispensable as aerospace, national defense, and biomedical applications. However, the presence of robust covalent or ionic bonds within the ceramic leads to its inherent poor fracture toughness. The incorporation of toughening phases into ceramics is widely recognized as an optimal toughening strategy for ceramic matrix composites (CMCs) based on chemical means, with the interplay between toughening phase and ceramic at the interface playing a crucial role in achieving superior mechanical properties. In this review, we briefly delineate the evolution of ceramic matrix composites, emphasizing that interface engineering constitutes an efficacious approach to augmenting the fracture toughness of these composites. Furthermore, we meticulously explore the structure-activity relationship between the composition and structure of the toughening phase and the mechanical attributes of CMCs. Additionally, we comprehensively summarize the impact of innovative biomimetic structures on the mechanical properties of these composites, unveiling the beneficial effects of interface regulation on energy dissipation. Ultimately, we systematically consolidate the mechanisms underpinning the influence of interface engineering on the mechanical properties of CMCs and propose solutions to existing interface challenges, paving the way for the development of next-generation CMCs that exhibit unparalleled strength and toughness.

Optimizing electrochemical removal of perfluorooctanoic acid in landfill leachate using ceramic carbon foam electrodes by coupling CFD simulation and reactor design.

Optimizing electrochemical removal of perfluorooctanoic acid in landfill leachate using ceramic carbon foam electrodes by coupling CFD simulation and reactor design.

Zirconium diboride-based slurries with readily controlled viscosity for preparing ceramic matrix composites

Zirconium diboride-based slurries with readily controlled viscosity for preparing ceramic matrix composites