Civil aircraft health management technology serves as an effective means to ensure aviation safety and enhance operation and maintenance efficiency. The implementation of health management technology is inseparable from efficient and advanced fault diagnosis technology. Based on the development needs of fault diagnosis technology for typical system health management of civil aircraft, this paper systematically reviews the fault diagnosis technology methods for civil aircraft health management, conducts in-depth analysis from three dimensions: Model-driven, knowledge-driven, and data-driven, summarizes the advantages, disadvantages, and applicable scenarios of each dimension’s technology methods, provides an application framework for the integration of technologies from each dimension, and looks forward to the overall development trend of civil aircraft health management, offering theoretical references and optimization paths for the engineering application of domestic civil aircraft health management technology.
Carbon Fiber Reinforced Polymer (CFRP) has become a core material for the lightweight design of primary load-bearing components in next-generation aircraft, owing to its high specific strength and stiffness, corrosion resistance, and structural tailorability. However, due to the intrinsic anisotropic mechanical behavior and weak interlaminar strrength, CFRP components are prone to non-uniform deformation and stress distribution during assembly, resulting from accumulated manufacturing tolerances and assembly coordination requirements. In severe cases, this can lead to irreversible damage modes such as fiber/matrix interface debonding, interlaminar shear failure, and matrix microcrack propagation. Focusing on the need for stress control during the assembly of aircraft composite panels, this study comprehensively considers key process steps including clamping and positioning, gap compensation, and mechanical joining. It reviews the current state of research and application of related technologies domestically and internationally—from the optimization and online adjustment of positioning layouts, gap measurement and compensation, to process control in mechanical joining. Future development directions for stress control technology in composite panel assembly are proposed, providing a reference for low- or no-stress assembly of flexible composite components.
Aimed at low-frequency noise in aerospace applications, a micro-perforated plate (MPP) and a triply periodic minimal Surface (TPMS) was combined as a MPP–TPMS sandwich structure. This structure achieves efficient mid-to-low frequency sound absorption while maintaining advantages in lightweight design and compactness. The Primitive structure in the TPMS structure was selected as the structural core material, and a Helmholtz resonator array can be formed by designing a perforated plate-cavity unit. Based on microperforated plate sound absorption theory and Johnson-Champoux-Allard equivalent fluid theory, a theoretical sound absorption model of the MPP–Primitive sandwich structure was established to explore the coupling effect of local resonance effect and thermal viscous dissipation mechanism in sound wave attenuation. Samples were fabricated by fused deposition modeling (FDM) technology. The effects of MPP, unit cell size of Primitive, cavity thickness, and MPP aperture on the acoustic properties of the sandwich structure were systematically investigated through acoustic impedance tube tests and finite element simulations. The results demonstrate that the combination of MPP and TPMS activates the sound absorption mechanism of the Helmholtz resonance cavity and greatly improves the sound absorption characteristics, and the sound absorption frequency band moves towards the lowfrequency region, and the sound absorption peak is close to 1. Increasing the size of the Primitive effectively expands the volume of the resonance cavity, reduces the low-frequency acoustic impedance, and enhances the acoustic impedance matching with low-frequency sound waves, thereby improving the absorption efficiency of low-frequency sound waves. Reducing the MPP’s aperture and increasing the surface acoustic resistance of the structure effectively broadens the bandwidth of the sound absorption peak, greatly improving the peak value of the sound absorption and migrating it to low frequencies. Increasing the thickness of the primitive cavity, extending the sound wave propagation path, and migrating the Helmholtz resonance peak to low frequencies by enhancing viscous dissipation and heat conduction effects. This work provides support for the design of sub-wavelength low-frequency sound-absorbing MPP–TPMS composite sound-absorbing metamaterials.
As structural materials with intelligent responsive characteristics, 4D printed mechanical metamaterials achieve dynamic regulation of mechanical properties and environmental adaptability through programmable microstructures and multi-material composite design. 4D printed mechanical metamaterials demonstrate unique advantages in terms of performance dimensions, yet their engineering application in the complex service environment of aerospace still faces numerous challenges. This paper reviews the current applications and technological advancements of 4D printed mechanical metamaterials in the aerospace domain. The article articulates the basic concepts of 4D printing and mechanical metamaterials, examines the research progress of 4D printed mechanical metamaterials and their applications in the aerospace field. The current scientific and technological challenges lie in achieving multi-scale manufacturing precision, realizing complex structural architectures, and ensuring performance stability. Looking ahead, future research should focus on the development of high-performance intelligent materials, as well as the establishment of computational simulation and optimization design methodologies, highlighting the interdisciplinary nature of 4D printed mechanical metamaterials. Such materials are expected to advance aerospace technologies toward higher efficiency, reliability, and intelligence, thereby providing strong support for technological innovation in related fields.
Mechanical metastructures, owing to their exceptional mechanical performance and structural adaptability, have shown broad application potential in fields such as aerospace and advanced engineering. However, most existing metastructures are fabricated using additive manufacturing (AM), which often results in fixed mechanical properties and limited tunability. To overcome these limitations, this study proposes a programmable discrete assembly approach based on L-shaped modular elements. The proposed module exhibits geometric compatibility, allowing the construction and topological transformation of three representative lattice architectures—Octet, FCC, and Cuboctahedra—through variations in spatial configuration, thereby overcoming the structural singularity inherent in conventional assembly methods. A hybrid fabrication process combining 3D printing and mechanical fastening was adopted, achieving support-free printing while maintaining high fabrication efficiency and cost-effectiveness for metastructures. Finite element simulations were employed to systematically investigate the mechanical responses of the three discretely assembled lattices, elucidating the intrinsic relationships between lattice topology, stiffness, strength, and energy absorption characteristics. Furthermore, two performance modulation strategies—soft-hard layered hybridization and local lattice hardening—were proposed to enable programmable control of global and local mechanical properties. This study establishes a new design framework for tunable mechanical metastructures, providing an effective pathway for customized performance and lightweight design in large-scale aerospace and multifunctional structural applications.
Conventional electromagnetic (EM) absorbing materials exhibit fixed EM properties, limiting their ability to adapt to spatiotemporal variations in the ambient EM environment. With the advancement of high-resolution radar imaging systems such as synthetic aperture radar (SAR), the EM reflection differences between targets and their surroundings can be precisely identified, significantly increasing the risk of target exposure. To achieve effective camouflage under imaging conditions, it is imperative to develop dynamically tunable EM absorbing materials operating in the microwave band that can modulate their EM responses to match the environment, thereby reducing detectability. Recent progress in novel material and device systems, as well as deformation-driven modulation mechanisms, has enabled the realization of broadband EM absorption with large modulation depth. This review summarizes research advances in representative material systems including graphene, diodes, and fluidic media, alongside mechanical deformation-based modulation approaches. The EM modulation mechanisms of various technologies are analyzed, and design strategies for extending modulation bandwidth and enhancing modulation depth are discussed. Finally, future development directions of dynamically tunable EM absorbing materials are proposed.
Low-frequency noise control has consistently been a key focus and challenge in the field of noise control. Due to the limited effectiveness of traditional duct silencing materials in absorbing low-frequency noise, acoustic metamaterials have emerged as a prominent research topic. Previous designs of acoustic metamaterials often overlooked the structural load-bearing performance requirements imposed by practical application environments. Lattice-enhanced structures, as a significant branch of mechanical metamaterials, can be integrated into acoustic metamaterials to enhance their mechanical properties, thereby increasing the feasibility of applying acoustic metamaterials. This study introduces the plate-lattice structure from lattice-enhanced structures into a Helmholtz resonator, designing ventilated acoustic attenuationbearing metamaterials (VAABM). VAABM samples were fabricated using fused deposition modeling (FDM) technology. Their low-frequency sound attenuation performance was calculated using the transfer matrix method (TMM) and validated through finite element (FE) simulation and acoustic impedance tube testing. The results demonstrate that the transmission loss (TL) reaches 21.3 dB at 674 Hz and 33.8 dB at 1078 Hz, with a TL greater than 10 dB across the frequency band of 642–1600 Hz. Furthermore, the study investigates the influence of key geometric parameters of the metamaterial structure on the sound attenuation performance of VAABM, which is shown to primarily originate from the resonance effect. Additionally, the mechanical performance of VAABM is discussed and compared with that of two classic triply periodic minimal surface (TPMS) structures. The results indicate that VAABM exhibits superior load-bearing capacity and dimensional stability. The multifunctionality of VAABM endows it with broad application prospects in the field of duct noise control.
Due to the low thermal conductivity of traditional resin-based composite materials, the thermal resistance of composite casing is large, the heat dissipation is slow, and there are bottleneck problems such as difficult heat transfer, too high local temperature, material softening and structural failure, which seriously restrict the further application of composites in helicopter transmission casing. In view of this, this paper carried out the optimization research on the thermal performance of metal-reinforced resin-based thermoplastic composite casing, which shows that compared with the traditional aluminum alloy casing, the metal-filled composite casing maintains good heat dissipation and reduces the weight by about 15%; compared with the pure resin casing, the maximum temperature performance is reduced by 69.4%, effectively improving the heat dissipation performance.
Aeronautical flared tube fittings are widely used in aircraft hydraulic, fuel and pneumatic systems for pipeline connections and sealing. These fittings frequently experience fluid leakage under vibration conditions, with transversal vibration being the primary cause of thread loosening and seal failure. This paper establishes a coupled analysis framework integrating vibration behavior, microscopic contact characteristics, and leakage rate calculation for flared tube fittings. The study systematically reveals the contact stress distribution and leakage evolution at sealing interfaces under transversal vibration. Results indicate that transversal vibration transforms uniform circumferential contact pressure into non-uniform distribution, reduces contact area, and expands leakage channels on the vibration-direction side. After 10 vibration cycles, leakage rate increases to 2.68 times initial value. The research quantifies leakage variations under different bolt preloads, vibration amplitudes, surface roughness levels, and medium pressures. Design recommendations propose minimum preload force of 4180 N, maximum surface roughness of 1.6 μm, and clamp installation near fitting connections to mitigate vibration effects.
Nickel-based superalloys GH3030 and GH4648 were joined using the B–Ni73CrSiB–40Ni–S brazing filler metal. The effects of varying brazing temperatures on the microstructure and mechanical properties of the GH3030/GH4648 brazed joints were systematically investigated. The hardness of the base material, along with the microscopic morphology, composition, and tensile strength of the joints, was analyzed. The results indicate that the use of B–Ni73CrSiB–40Ni–S brazing filler metal can achieve an effective connection between GH3030 and GH4648 brazing joints. The four elements—Cr, Si, Fe, and Ni— enhance the bonding between the brazing filler metal and the honeycomb structure. The brazing temperature significantly affects the microstructure and mechanical properties of the joint. When the brazing temperature is low, the fracture surface will exhibit plastic deformation. When the brazing temperature reaches 1080 ℃ , the fracture exhibits a notable ability for plastic deformation, and the tensile strength of the joint is at its peak during this phase. As the brazing temperature rises, the formation of brittle compounds increases, significantly diminishing the mechanical properties of the joint. The fracture morphology results indicate that two fracture modes were observed: quasi-cleavage fracture and a mixed mode of quasi-cleavage fracture with micropore aggregation fracture.
The microstructure evolution and endurance and creep deformation behavior of TiBw/TA15 composites during solution–aging heat treatment were studied. The results demonstrate that the silicide morphology, size and precipitation location are affected by temperature, time, crystal defects and endurance and creep deformation process during the heat treatment. High aging temperature, long aging time and the existence of crystal defects such as dislocations after heat treatment are the main causes for the precipitation and aggregation of large-grained silicide. Properly increasing the aging temperature will help to achieve fine dispersion and precipitation of the α2 phase, and the α2 phase tends to coarsen and aggregate when the aging time is prolonged. After heat treatment, the endurance and creep properties are affected by the silicide and α2 phase, among which, the silicide with large amount of precipitation and large size shortens the endurance time of fracture of the composite. The dislocations occurring in the durable deformation process mainly occurs in α layer, which would be impeded by the intragranular α2 phase and its whiskers. The crack propagation caused by whisker fracture during durable deformation process is the main reason why the general endurance time of fracture of the composite is short. At the testing conditions of 650 ℃ /100 MPa/100 h, the creep process of TiBw/TA15 composite is mainly affected by dislocations exiting in intragranular α and β phases and the interactions between precipitations and dislocations.
To reduce drilling temperatures and improve the machining quality of CFRP/Ti6Al4V laminates, this study proposed a cryogenic minimum quantity lubrication (CMQL) technique, utilizing the high solubility of lubricant in supercritical carbon dioxide (ScCO2). Tests were conducted on the droplet atomization performance and output temperature of the CMQL system, followed by low-frequency vibration drilling experiments under CMQL conditions for CFRP/Ti6Al4V laminates. The influence of CO2 pressure on laminate drilling was analyzed. The results demonstrate that increasing CO2 pressure enhances the atomization and cooling capability of the CMQL system. When the pressure increases to 8 MPa, CO2 presents as supercritical state, and the output temperature drops to below –80 ℃. As the system pressure rises from 5 MPa to 9 MPa, the drilling temperatures of CFRP and Ti6Al4V layers decrease by 15.91% and 50.78%, axial forces increase by 65.22% and 20.26%, and torques decrease by 23.33% and 16.77%, respectively. Moreover, the burr height at the Ti6Al4V layer exit decreases by 42.04%, the delamination factor at the CFRP layer exit is reduced by 5.41% and a low roughness of borehole wall of CFRP/Ti6Al4V laminates is achieved at pressures of 7 MPa, 8 MPa and 9 MPa.
