As a typical ceramic matrix composite (CMC), carbon fiber-reinforced silicon carbide matrix composites (C/SiC) exhibit outstanding properties, including high specific strength, high specific stiffness, and high-temperature resistance, making them widely applicable in aviation, aerospace, automotive, and other advanced engineering fields. To investigate the surface damage forms of C/SiC composites under different energy fields, this study conducted conventional scratching (CS), laser-assisted scratching (LAS), and laser-ultrasonic hybrid scratching (L-UHS) on three typical fiber orientations. The scratching forces and surface morphologies under these three scratching methods were systematically compared to analyze the influence of laser-ultrasonic hybrid energy fields on surface damage of the material. The results show that, compared with CS and LAS, L-UHS can effectively reduce scratching forces and improve machinability. L-UHS demonstrates distinct fracture mode transitions across different fiber orientations: In the parallel orientation, fiber bending fracture is significantly reduced, and the primary failure mode is interlaminar fracture; In the inclined and perpendicular orientations, the fiber failure mode transitions from bending fracture to shear fracture. This study provides theoretical guidance for laser-ultrasonic hybrid machining of C/SiC composites.

Ceramic matrix composites (CMC) are internationally recognized as the next generation of thermal structural materials. CMC material designation standards have been established and modular design methods have been developed. CMC have been widely applied and validated in high-temperature end components in multiple aerospace fields. As ceramic matrix composites transition from laboratory research and development to engineering application and mass production, joining and repair technologies have become key to driving the application of these composites. Given the interconnection between joining and repair technologies, this paper systematically reviews the research progress and development trends in the joining and repair technologies for ceramic matrix composites. For joining technologies, which need to address both chemical and physical compatibility, this review summarizes the research progress on active brazing, metallic diffusion bonding, nano-Infiltration and transient eutectic bonding, reaction infiltration siliconization, and adhesive bonding. For the rapid and effective repair of surface damage in ceramic matrix composites, this review also covers the application progress of self-healing technologies, chemical vapor deposition, slurry coating, and laser cladding. Finally, the development trends of an integrated design approach for joining and repair of ceramic matrix composites are prospected.

The C/C–Ti₃SiC₂ composites were prepared by reactive melt infiltration (RMI) using TiC powder, Ti powder, Si powder, and Al powder as raw materials. The effects of different molar ratios of raw materials on the phase composition, microscopic morphology, flexural strength, thermophysical properties, and electromagnetic shielding effectiveness of the composites were investigated. The results show that the composites prepared with the ratio 1.8TiC/1.2Ti/1.4Si/0.2Al have a higher Ti₃SiC₂ content and exhibit better mechanical properties, thermal conductivity, and electromagnetic shielding performance: the flexural strength increases from 103.02 MPa ± 8 MPa to 150.50 MPa ± 7 MPa; the thermal conductivity ranges from 12.651 W/(m·K) to 15.193 W/(m·K) at temperatures from room temperature to 1000 ℃; and the electromagnetic shielding effectiveness increases from 21.40 dB to 26.68 dB in the 8.2–12.4 GHz frequency range. Analysis of the phase composition and microscopic morphology of three groups of samples reveals that as the TiC to Ti molar ratio decreases, the difficulty in forming Ti₃SiC₂ gradually increases, mainly because the Ti content plays a key role in both the formation of the liquid phase during the reaction and the extent of the reaction.

Alumina/alumina ceramic matrix composites (Al₂O₃/Al₂O₃ CMCs) have demonstrated broad application prospects in aerospace, energy, and other high-temperature fields due to their low cost, short fabrication cycles, and excellent oxidation resistance. This review systematically summarizes the key challenges and recent advances in the preparation of Al₂O₃/Al₂O₃ CMCs, focusing on core technical issues such as low-temperature sintering, homogeneous densification, and microstructure control. A comparative analysis of fabrication techniques, including sol-gel, slurry infiltration, and automated fiber placement, highlights their respective advantages and limitations. Furthermore, practical applications in aircraft engine combustors, exhaust components, aerospace thermal protection systems, high-temperature parts in automotive and low-altitude unmanned aerial vehicle, and industrial kilns are discussed, demonstrating the material’s superior thermal stability and lightweight potential. Future research should prioritize process optimization, strengthen automated production, and expand application scenarios to further advance the development of high-temperature structural materials.

High-temperature oxidation-induced degradation is a critical factor limiting the application of C/SiC ceramic matrix composites in aerospace thermal-structural components. To accurately predict the oxidation damage evolution and mechanical property degradation of such materials, a systematic numerical study is conducted in this work. First, based on Fick’s diffusion law and the characteristics of oxidation reactions, chemical consumption terms and damage factors are introduced to establish a coupled diffusion–reaction oxygen concentration equation and an oxidation state evolution model. Using the COMSOL platform, the oxygen concentration field and oxidation damage factor distributions of a two-dimensional woven C/SiC composite subjected to oxidation at 650 ℃ for 2 h, 4 h, and 6 h are simulated, revealing the spatial-temporal distribution and evolution of oxygen in different structural regions. Subsequently, by integrating continuum mechanics with progressive damage theory, a coupled stiffness-degradation model incorporating limited and continuous degradation is developed, and the post-oxidation tensile response is predicted using the ABAQUS platform. The simulation results show good agreement with experimental data in terms of stress–strain behavior and residual strength, with a maximum error below 10%. This study provides theoretical support and numerical tools for evaluating the postoxidation mechanical performance of C/SiC composites under high-temperature service conditions.

Silicon carbide ceramic matrix composites (SiC–CMC), characterized by low density and hightemperature resistance, show broad application prospects in hot-section components of aero-engines. However, hightemperature wet-oxygen corrosion remains a key challenge restricting their applications. This article provides a comprehensive review of the wet-oxygen corrosion resistance, microstructure, mechanical properties and primary preparation methods when rare earth compounds: Including rare earth phosphates, rare earth silicates, rare earth oxides, rare earth silicide carbides, and Si–Y eutectic alloys, are incorporated into the SiC–CMC matrix, interphase and coatings. Furthermore, it presents the critical challenges and prospects for rare earth compound-modified SiC–CMC technology.

High-power linearly polarized narrow linewidth fiber lasers hold broad application prospects in wavelength beam combining, coherent detection, and other fields. In such lasers, transverse mode instability (TMI) is one of the main factors limiting their power scaling. In this paper, the influence of the TMI effect on the output power of high-power linearly polarized narrow linewidth fiber lasers is analyzed, and a TMI suppression method is proposed. The experiment employs multi-wavelength pumping technology, using 100 mW single-frequency laser as the seed source. The linewidth of the seed source is broadened to 23 GHz via a phase modulator, and after three-stage amplification, a linearly polarized narrow linewidth laser output is finally achieved with the following parameters: power of 2.54 kW, linewidth of 23 GHz, central wavelength of 1064 nm, extinction ratio of 98%, and beam quality factors M_x² = 1.21 and M_y² = 1.23. The influence of pump wavelength on the TMI effect is further analyzed. Due to the small core diameter of the fiber (20 μm) and the high absorption coefficient of the gain fiber for pump light (1.8 dB/m@976 nm), the core temperature increases significantly. Additionally, the heat introduced by the pump photon quantum defect causes a variation in the refractive index of the fiber core, leading to the occurrence of TMI at relatively low power levels. When the pump wavelength is shifted to longer wavelengths, both the quantum defect of the pump light and the pump absorption coefficient decrease, resulting in reduced heat distribution across the entire fiber length as well as per unit length. This thus increases the TMI threshold and effectively improves the output power of the linearly polarized narrow linewidth fiber laser.

Currently, unmanned aerial vehicles (UAVs) primarily rely on the global navigation satellite system (GNSS) for navigation and localization. However, in scenarios where satellite signals are weak or interfered with, the completion of UAV missions is severely affected, and the safe flight of UAVs could even be jeopardized. To address this issue, this paper proposes a visual localization algorithm to ensure the safe and long-term flight of UAVs in GNSS-denied environments. The algorithm calculates the UAV's geographic coordinates by matching aerial images captured by the UAV with geotagged satellite maps. Firstly, a satellite map preprocessing method is designed to reduce the computational load during UAV flights. Secondly, the learned perceptual image patch similarity (LPIPS) metric is used for initial retrieval. Finally, image matching and offset estimation are performed by combining the deep learning-based SuperPoint sparse feature extraction algorithm and the LightGlue feature matching algorithm, thus finally achieving UAV visual localization. The proposed method is tested on the ALTO dataset, achieving a 17.2% improvement over the current state-of-the-art methods in terms of the R@1 metric, which demonstrates its feasibility and advancement.

This study investigates the effect of cold rolling pre-deformation with different reductions on the microstructure and mechanical properties of a novel polycrystalline nickel-based superalloy with low stacking fault energy and precipitation strengthening. The results indicate that cold rolling pre-deformation introduces microscopic substructures in the alloy, including dislocations, anti-phase boundaries (APBs), stacking faults (SFs), and Lomer–Cottrell (L–C) locks. The content of these substructures is positively correlated with the pre-deformation reduction. When the predeformation reaches 15%, a small amount of deformation twins are introduced near the grain boundaries, and the content of deformation twins in the 25% pre-deformation specimen further increases. With increasing pre-deformation reduction, the room-temperature tensile strength and yield strength gradually increase, while the plasticity gradually decreases. Due to the presence of nano-twins and grain refinement in the 25% pre-deformation specimen, its strength is further improved compared to the 15% pre-deformation specimen, while its plasticity remains roughly consistent.

The high noise and low resolution of ultrasonic testing images of large-thickness honeycomb sandwich composite components bring challenges to quality evaluation and defect identification. In this study, image denoising and super-resolution reconstruction methods are investigated using ultrasonic C-scan images of the C919 inner door for the main landing gear. An efficient edge-preserving filter denoising scheme based on a gradient descent algorithm is proposed, effectively removing speckle noise while preserving image details. After denoising, the peak signal-to-noise ratio reaches 37.53 dB and the structural similarity is 0.92, outperforming the digital morphological filter by 12.99 dB and 0.04, respectively. The images reconstructed by the improved super-resolution residual network (ISRResNet) model have high resolution, rich content details, and clear edges. Furthermore, an image with Φ11 mm delamination defects is processed, the signal-to-noise ratio of defects is improved by 6.25 dB on average. Results show that the proposed denoising method and super-resolution model can effectively remove speckle noise, improve the image resolution, and enhance the accuracy of defect quantification. It can support high-quality ultrasonic testing of large-thickness honeycomb sandwich composite components.

Welding residual stress is a critical factor contributing to the deformation of spacecraft cabin bodies during CNC machining. To mitigate such machining deformation, this paper conducts simulation and experimental studies on ultrasonic vibration-based stress regulation of electron beam welds in 5B70 aluminum alloy cabin bodies. This reveals the influence of the law of amplitude and treatment times on weld residual stress. A stress regulation process scheme for 45 mm thick plate butt welds is proposed: An ultrasonic amplitude of 30 μm, with two repeated treatments on the front side of the weld. After stress regulation, the peak values of transverse residual stress σ_x and longitudinal residual stress σ_y on the back surface of the weld are reduced by 33.94% and 67.05%, respectively. And the corresponding homogenization rates are 22.22% and 22.37%, respectively. Milling tests show that the machining deformation of the stress-regulated specimens in the Z-direction is reduced by 64.48%, which validating the efficacy of ultrasonic vibration-based regulation of welding residual stress in reducing cabin body machining deformation.

This study investigates the effects of shot peening intensity, shot medium (cast steel shot and ceramic shot), and composite shot peening on the fatigue properties of high-strength and high-toughness β-titanium alloy. Characterization techniques, including scanning electron microscopy (SEM) and X-ray diffractometry (XRD), were employed to analyze the influence of shot peening processes on the surface integrity and fatigue fracture behavior of target materials. Experimental results show that shot peening effectively modifies the machined surface profile of target materials. With the increase of shot peening intensity (up to 0.25 mmA), surface roughness increases, yet no delamination or micro-crack defects are observed, indicating excellent plasticity toughness of the target materials. However, the surface of target materials is sensitive to coverage: Local delamination and wrinkling defects occur on the surface after composite shot peening with 400% coverage. Shot peening introduces a residual compressive stress layer approximately 280 μm in depth on the surface of target materials. The residual stress value generally increases with shot peening intensity, but stress relaxation occurs in the near-surface layer (50 μm thickness) when the intensity reaches 0.22 mmA. Shot peening significantly enhances fatigue performance: Under cast steel shot peening conditions, the fatigue life increases by 145.4 times compared to the as-received state, with individual specimens reaching 1×107 cycles. Ceramic shot peening demonstrates more pronounced fatigue improvement at the same intensity. For peening with a single-shot medium, crack initiation sites shift to the subsurface layer, whereas composite shot peening reduces the average fatigue life significantly, with some crack sources appearing on the surface, attributed to surface damage and residual stress relaxation. In conclusion, high-strength and high-toughness β-titanium alloy exhibits favorable shot peening performance, low sensitivity to shot peening intensity (resistant to delamination or microcrack), but high sensitivity to shot peening coverage, making it unsuitable for composite or extended shot peening treatments.

As a critical component of high-performance aerospace engines, the blisk poses significant challenges to manufacturing technology due to its complex structure and poor machinability. To address the wide-path machining demand of blisk blade surfaces, this paper proposes an improved variable chordal trajectory planning method. First, the blade surface was reconstructed. Taking the concave-convex properties of the blade surface and tool machine tool motion constraints as the criteria, the design principles for drum grinding wheels were extended. Then, the reconstructed surface was trimmed according to the actual machining area, and the grinding trajectory of the wheel was planned by considering the influence of blade surface curvature variation in the tool path direction on chord height error. The results show that compared with the drum grinding wheel designed by traditional methods, the one designed based on the extended principles reduces the number of tool paths from 41 to 32 under the same conditions, effectively increasing the machining row width. The improved planning method can also control the chord height error within the allowable range. Simulations with different grinding wheels show that the standard deviation of undercut is reduced from 9.42 μm to 5.27 μm, and from 2.82 μm to 1.98 μm, respectively, resulting in a more uniform undercut distribution.

The microstructure of domestic automated placement dry fibers was characterized and analyzed, with a comparative analysis against imported materials. Using a self-made glass mold and adopting the central injection method, the number of layers of domestic automated placement dry fibers was varied. Based on Darcy’s law, the permeability of domestic dry fibers was calculated, and the factors influencing their permeability were explored. The results indicate that domestic dry fibers share the same three-layer structure in microstructure as the imported dry fiber TX1100. The average diameter of fibers in the mesh layer of domestic dry fibers is 20 μm, three times that of TX1100. At the same layer count, the permeability in the X-direction is approximately twice that in the Y-direction. As the number of layers increases, the permeability in both X and Y directions rises, while penetration in the Z-direction is relatively difficult. Additionally, the permeability of dry fiber brand 231016FH is higher than that of 231227FH, and the fibers in the composite formed by 231016FH are arranged more tightly.