In fuel cell hybrid systems, the degradation processes of fuel cells and power batteries are highly inconsistent. The excessive consumption and premature end of life of one power source can disrupt the balance of the power system, deplete the performance of the other power source, accelerate the aging of the entire power system, and negatively affect vehicle economy and system durability. Consequently, it becomes challenging to achieve optimal fuel economy and system durability simultaneously. To address this issue, an optimization strategy based on condition prediction and coordinated power source life degradation is proposed.
Firstly, to improve prediction accuracy, operating conditions are categorized into three typical states: low-speed, medium-speed, and high-speed. An upper-level Markov Chain Monte Carlo (MCMC) prediction model is established based on historical conditions to predict the tram's operating conditions. This prediction provides more information for the lower-level energy management strategy to optimize system energy distribution. Secondly, in the lower-level energy management strategy, the hydrogen consumption of the fuel cell and the equivalent hydrogen consumption of the auxiliary power source are analyzed. A continuous degradation model for the fuel cell and power battery is established, introducing optimization objectives and adaptively adjusting the weights of each objective online to optimize the multi-objective function. Finally, the proposed strategy is compared with the traditional equivalent consumption minimization strategy (ECMS) and the external energy maximization strategy (EEMS).
Results show that at the end of the entire operating condition, the proposed strategy's hydrogen consumption is 99.61 g, the degradation rate difference between the dual power sources is 0.000 66%, the system efficiency is 81.66%, the power fluctuation range is -800 W to 800 W, and the stress on the power battery and supercapacitor is 117.5 and 176.4 respectively. Compared to the ECMS strategy, with a hydrogen consumption of 115.1 g and system efficiency of 77.64%, the proposed strategy improves fuel economy and system efficiency by 15.6% and 5.2% respectively. Compared to the EEMS strategy, with a dual power source degradation rate difference of 0.014 4% and system efficiency of 79.77%, the proposed strategy reduces the degradation rate difference by 21.82 times and improves system efficiency by 2.4%. Additionally, the power fluctuation range under the proposed strategy is significantly reduced compared to the -1 000 W to 1 000 W range under both the ECMS and EEMS strategies, resulting in a smoother power source power curve. Under the ECMS strategy, the stress on the power battery and supercapacitor is 156.6 and 215 respectively, while under the EEMS strategy, the stress is 156.8 and 226.6 respectively. The proposed strategy reduces the stress on the auxiliary power source compared to the ECMS and EEMS strategies, decreasing excessive consumption and resulting in a more reasonable power distribution.
Comprehensive simulation analysis reveals the core advantages of the proposed strategy: (1) Establishing an MCMC prediction model for condition prediction improves the adaptability of the energy management strategy to operating conditions, achieving more reasonable, precise, and efficient energy control and reducing damage to the hybrid power system. (2) Overcoming the poor fuel economy of traditional ECMS and the high inconsistency in power source degradation of EEMS. (3) Achieving superior fuel economy and system durability, thereby extending the lifecycle of fuel cell hybrid systems.

Addressing the issues of inadequate exploitation of hydrogen energy collaboration potential and the challenge in balancing accuracy and efficiency of probabilistic solution algorithms, this paper proposes a calculation method for the probabilistic optimal energy flow of electricity-hydrogen systems based on compressed sparse arbitrarily polynomial chaos expansions (CS-aPCE).
Firstly, to harness the spatial-temporal collaboration potential of hydrogen energy, a modeling approach for electricity-hydrogen optimal energy flow is introduced incorporating peer-to-peer (P2P) hydrogen collaboration between on-site and off-site hydrogen refueling stations (HRSs). Considering the P2P coupling of inter-station hydrogen flows and bidirectional electricity flows, a P2P collaboration mechanism is proposed for between on-site and off-site HRSs and the power distribution network. Based on Nash bargaining theory, a probabilistic optimal electricity-hydrogen energy flow model is constructed, which incorporates time-delay and discreteness constraints for inter-station hydrogen P2P transactions. This model coordinates multi-stakeholder benefit allocation and electricity-hydrogen price decisions, enhancing feasibility and fairness.
Secondly, a probabilistic optimal energy flow solution algorithm for on-site and off-site HRSs and power distribution networks is proposed based on CS-aPCE, aiming to improve the efficiency and accuracy of high-dimensional probability calculations. The core of this algorithm lies in leveraging historical data to drive the collocation points, subsequently calculating key statistical metrics such as expectations and standard deviations through analytical methods, without reliance on prior probabilistic information. To further optimize computational performance, the CS-aPCE algorithm integrates Gaussian quadrature rules to construct high-frequency collocation points and incorporates compressed sparse grid techniques. Effective compression criteria are proposed, and the dimensionality reduction effect and computational accuracy of the algorithm are theoretically proven, ensuring its efficiency and robustness under high-dimensional randomness.
The effectiveness of the proposed method is validated through numerical examples, leading to the following conclusions: firstly, the CS-aPCE algorithm presented in this paper can solve high-dimensional and probabilistic electricity-hydrogen energy flow problems rapidly and with high precision. The computation time is merely 10% of that required by the Monte Carlo simulation method, while the errors in expected values and standard deviations are below 4.21%. Furthermore, the computational accuracy for higher-order moments is improved by 60.28% to 156.98% compared to the traditional aPCE method. Secondly, the stationarity threshold exerts a certain influence on the accuracy and efficiency of the CS-aPCE algorithm. A reasonable threshold should be selected by comprehensively considering the stationarity distribution characteristics of random variables. Finally, the electricity-hydrogen optimal energy flow model considering P2P hydrogen collaboration between stations can mobilize the coordination potential of flexible resources within the distributed hydrogen supply network, coordinate the distribution of inter-station hydrogen flows, and achieve fair allocation of benefits among multiple stakeholders.

Applying the vacuum switch in the more-electric aircraft intermediate frequency (IF 360~800 Hz) power system is a new application field, which can solve the difficulties caused by the increase of current frequency and the limited breaking ability of electrical appliances. The anode activity of the vacuum arc determines the post-arc state and interruption ability of the vacuum switchgear, especially at high current, and the anode can actively emit metal vapor, plasma and metal droplets. Because of the special environment of the vacuum chamber, it is difficult to directly measure the physical quantity of the post-arc state, such as arc pressure, by using the sensor, so non-contact measurement means is generally adopted. To gain a more comprehensive understanding of the post-arc characteristics of intermediate frequency vacuum arcs, the visual tracking techniques such as object detection and Intersection over Union Tracker were utilized to analyze arc images in this paper. The splatter trajectories of post-arc metal droplets were reconstructed in three dimensions. Based on the reconstruction, the spatial pressure gradient inside the arc was determined.
Firstly, an intermediate frequency vacuum arc experimental system was established, along with a dual high-speed camera stereoscopic arc imaging system. Secondly, the experimental results of the intermediate frequency vacuum arc were analyzed, revealing post-arc voltage oscillations and metal droplet ejection phenomena during interruption failure. Thirdly, utilizing visual tracking techniques such as Canny edge detection, connected component analysis, and IoU, along with the mapping relationship from arc plane to three-dimensional space, a method for analyzing the pressure gradient of the post-arc vacuum arc was developed. The detection and tracking performance of arc images were evaluated using metrics such as precision, recall, MOTA, and MOTP, achieving values of 91.69%, 84.28%, 87.19%, and 82.63%, respectively, indicating excellent visual tracking results. Finally, using the aforementioned theories and methods, a comprehensive analysis of the post-arc characteristics of the intermediate frequency vacuum arc was conducted.
The following conclusions can be drawn from the analysis: (1) According to experimental results, when post-arc breakdown occurs after the intermediate-frequency current crosses zero, the arc voltage exhibits high-frequency oscillations with a frequency of approximately 50 kHz. The voltage stabilizes within about 2 ms. During the post-arc period, dual-view arc images reveal substantial outward ejection of metal droplets. (2) By employing visual tracking algorithms and spatial mapping relations, the three-dimensional ejection process of metal droplets during the post-arc breakdown can be reconstructed. The acceleration in all three directions reaches the order of 10⁵ m/s², with ejection velocities on the order of 10 m/s. The pressure gradient within the arc chamber can reach 1.2 MPa/mm, and the time scale for droplets to travel from the contact edge to the inner wall of the arc chamber is milliseconds. (3) The vapor density of Cu on the surface of the metal droplets is 2.2×10¹⁹ m^-3. Throughout the ejection process of milliseconds scale, the metal droplets continuously evaporate, reducing the Cu mass fraction on the droplet surface from 65% to 10%. A significant amount of Cu vapor enters the arc chamber through diffusion and convection, weakening the dielectric recovery strength post-arc. During this period, post-arc breakdown and high-frequency voltage oscillations occur.

Electric aircraft has become a major development trend in the future aviation industry due to its advantages of low carbon and environmental protection. The air insulation of electric aircraft needs to withstand high-frequency voltage in high altitude. Therefore, this paper qualitatively studies the air discharge characteristics and microscopic mechanisms between needle-plate electrodes under different pulse voltage parameters and different humidity in the low temperature sub-atmospheric pressure environment of high altitude through simulation and experimentation.
Firstly, the pulse power supply was built by a 4-stage half-bridge Marx circuit. Then, the two-dimensional axisymmetric streamer discharge model of low-temperature sub atmospheric air was built, and three sets of Helmholtz equations were coupled to calculate the photoionization. Finally, the images of air streamer discharge under different conditions were captured by intensified charge coupled device (ICCD).
The following conclusions are drawn through simulation and experiment under the condition of low temperature and sub-atmospheric pressure: (1) The simulation outcomes reveal that when the reduced electric field strength remains the same, as the altitude increases, the breakdown voltage drops, the electron density gradually reduces, the electric field strength of the streamer head decreases, and the development speed of the streamer slows down. As the rising edge of the pulse grows, the electron density decreases simultaneously. When the discharge can be accomplished within one pulse, an increase in the pulse width has minimal effect on the discharge. Under the circumstances of low temperature and sub-atmospheric pressure, with the rise in humidity, the electron density increases concurrently, the peak value of the electric field intensity also rises, and the development speed of the streamer becomes faster. (2) The experimental results indicate that when the reduced electric field strength is consistent, with the increase of altitude, the penetration time of the streamer becomes longer, the channel brightness decreases, and the channel radius increases. When the pulse width of the pulse voltage is greater than the discharge time, the increase in the pulse width has no influence on the discharge process; when the frequency of the pulse voltage rises, the brightness of the streamer channel gradually intensifies; under the condition of low temperature and sub-atmospheric pressure, with the increase in humidity, the penetration time of the streamer becomes shorter and the brightness of the streamer channel increases. (3) Under the same conditions, the simulation and experimental results have a consistent conclusion regarding the development speed of the streamer. The influence of the pulse width on the discharge depends on whether the discharge can be completed within one pulse. The brightness of the streamer channel is positively correlated with the electric field intensity of the streamer head.

With the development of wind power research, the factors considered in the simulation model are gradually increasing. The demand for wind turbine models that take into account both electrical and mechanical characteristics is increasing, thus promoting the development and application of co-simulation technology. However, the detailed electrical model has strict requirements on the simulation time step, which reduces the efficiency of co-simulation. Some scholars have properly simplified the electrical model to improve the simulation speed when carrying out co-simulation. But, improper selection of simulation time step has a negative impact on simulation accuracy. Therefore, this paper studies the model optimization and step size selection to solve the problem of the contradiction between simulation accuracy and speed.
First, the complex electrical model is optimized by ignoring the power electronic switching model and reducing the order of the higher-order model, so that the computational complexity is reduced and the application range of the simulation step size is increased. GH Bladed and Matlab/Simulink are selected to build the co-simulation platform. Then, a comprehensive evaluation method based on residual similarity and feature selection verification is proposed, which takes into account simulation accuracy and speed. The evaluation of simulation accuracy is divided into two aspects: global and transient difference. The comprehensive evaluation index is formed by combining the evaluation index of simulation accuracy and simulation speed in a weighted way to guide the selection of simulation time step. Finally, the co-simulation is carried out to verify the effect of the optimization model on the simulation efficiency under the conditions of wind speed disturbance, frequency disturbance and fault crossing disturbance. According to the simulation results and the comprehensive evaluation method, the reference suggestions for the selection of simulation step size are put forward.
Through simulation results and analysis, the following conclusions are drawn: (1) Through the optimized model, the co-simulation model can be run at a larger simulation time step, and the co-simulation efficiency is improved. (2) According to the proposed comprehensive evaluation method, the simulation results are evaluated from two dimensions of simulation accuracy and speed, which solves the problem of quantitative evaluation of the accuracy and speed of the model simulation results. (3) Through the co-simulation of various working conditions and the quantitative evaluation of simulation accuracy and speed, the following conclusions are drawn: Under the background of the simulation in this paper, under the condition of wind speed fluctuation, the simulation time step of co-simulation is chosen to be around 0.05 s; under the condition of frequency disturbance, the simulation time step of co-simulation is chosen to be around 0.01 s; under the condition of fault ride-through disturbance, the simulation time step of co-simulation is chosen to be around 0.005 s. (4) Based on the evaluation results of multi-condition simulation, the factors such as time scale of simulation condition and mutation characteristics of observed parameters should be fully considered in the selection of simulation time step. When the time scale is large and the observed parameters do not have mutation characteristics, the larger simulation time step can be selected. When the time scale is small and the observed parameters have mutation characteristics, the selection of simulation time step should be reduced appropriately.

Internal short circuit is one of the most serious faults in transformers, which can lead to a rapid increase in fault energy in a short period of time and easily cause high-energy discharge and explosion inside the equipment. However, there are many potential combinations of internal short circuit conditions in transformers. The analysis method of field-circuit coupling commonly used by transformer manufacturing enterprises has the problems of excessive time and resource consumption. And it is difficult to model jointly with the external power grid. Existing circuit models face difficulties in multi-scale coupling characterization and parameter calculation of windings.
This article focused on the urgent need for transformer short circuit fault analysis. A construction method of multi-scale fault analysis model for single-phase transformer with internal short circuit was proposed. Firstly, based on the multi-scale characteristics of transformer windings and internal short circuit faults, the transformer windings were virtually divided into several sub-windings using axial segmentation. By parametrically scanning the finite element model of the transformer, the self-mutual inductance matrix and resistance matrix of sub-windings was calculated. Secondly, an calculation method was proposed to transform the self-mutual inductance matrix into the coupled leakage inductance matrix, which could effectively characterize the leakage magnetic characteristics between sub-windings. This parameter calculation method could be carried without port short circuit tests, which solved the problem of parameter calculation for existing multi-winding transformer models. Finally, a multi-scale circuit model for transformers was established based on the coupled leakage inductance matrix. By connecting the terminals of each sub-winding based on the electromagnetic connection relationship and the physical process of internal short circuit, transformer fault analysis models for different internal short circuit conditions could be obtained. The problems of low efficiency and poor circuit adaptability in the fault analysis model based on field-circuit coupling were solved.
Furthermore, a disk-scale circuit model of an 80 MV·A single-phase transformer was constructed. A comparative simulation was conducted with the finite element model. The results indicated that the errors of the short-circuit impedance and the peak value of the port current at rated operating condition were almost zero. And the simulation time was reduced by about 99.98%. After single inter-turn short circuit faults, the errors of the first peak values of the port currents and short-circuit currents did not exceed 2.5%. The simulation efficiency was improved while ensuring simulation accuracy. Then, based on a certain engineering accident, a developmental inter-turn short circuit analogy simulation analysis was carried out. The errors of the first peak values of the port currents and short-circuit currents after the fault, as well as the local peak values during the fault development process, did not exceed 5.5%. And the duration of the second harmonic percentage of fault differential current accounting for more than 15% of the circuit model was calculated to be 49 ms. It was consistent with the finite element model calculation results. The existing method was 14ms. Therefore, the proposed construction method of multi-scale fault analysis model for single-phase transformer with internal short circuit can accurately simulate the transient characteristics of transformers with internal short circuit under multiple scales and operating conditions. This method provides a basic model for research on equipment accident analysis, traceability, and fault defense.

Epoxy resin is widely used in epoxy cast electrical equipment such as dry-type transformers and dry-type reactors due to its good mechanical strength, chemical corrosion resistance, and excellent electrical insulation performance. However, the irreversible cross-linking network formed after curing makes it difficult to degrade and recycle retired electrical equipment. Researchers have developed a series of biodegradable resins with high electrical thermal mechanical properties and degradation characteristics by introducing dynamic covalent bonds. However, epoxy electrical equipment such as dry-type transformers and dry-type reactors that operate in complex environments such as high temperature, high electric field, and mechanical vibration for a long time can experience performance degradation due to resin aging, which affects their service life. The changes in the cross-linking structure of epoxy resin caused by thermal oxidative aging may have a certain impact on the service performance and degradation recovery characteristics of degradable resins. This article used the ester exchange catalyst triethanolamine to construct a degradable epoxy resin system, and conducted accelerated thermal oxidative aging tests on it to analyze the effects of aging time and catalyst on the service performance and degradation characteristics of degradable epoxy resin.
Firstly, this article used ester exchange catalyst triethanolamine to construct a degradable epoxy resin system, and used traditional non degradable epoxy resin as a reference to conduct thermal oxidative aging tests on resins with different triethanolamine contents at three temperatures of 180℃, 200℃, and 220℃. Then, the performance changes of different resin systems after aging were studied through comprehensive analysis of electrical properties, thermogravimetric analysis, dynamic thermomechanical analysis, mechanical properties and microstructure analysis. The bending strength retention rate was used as an aging index to estimate the service life. Finally, this article also explored the influence of thermal oxidative aging on the degradation properties of degradable resins.
From the experimental analysis, the following conclusions can be drawn: (1) The insulation and electrical performance of the degradable epoxy resin system after high-temperature aging is slightly worse than that of traditional resins, but the degradation rate of the insulation performance of degradable resins is slower than that of traditional resins under 200℃ and 220℃ conditions, with V-TEOA-0.05 maintaining better electrical performance. (2) The thermal stability of the degradable epoxy resin system is slightly inferior to traditional resins, but V-TEOA-0.05 has a higher storage modulus and a slightly lower glass transition temperature, and also exhibits good thermal properties. (3) As the aging temperature increases, the difference in flexural strength between degradable epoxy resin and traditional resin after aging gradually narrows, and remains basically unchanged after 49 days of aging at 220℃. The estimated lifespan of the V-TEOA-0.05 system shows a temperature index of 163.13℃, demonstrating excellent heat and oxygen aging resistance. (4) In the mixed solution of EG and TBD, the degradation rate of V-TEOA-0.05 sample decreases with increasing aging time, which may be related to the increase in resin crosslinking density, decrease in free volume, and decrease in ester bonds.

Ice disasters can cause serious damage to power transmission network, it is crucial to enhance the resilience of power transmission network during ice disasters. Unlike extreme natural disasters such as hurricanes or earthquakes, ice disasters develop slowly and last long time. It is difficult to predict the development trend of ice disaster accurately due to the influence of microclimate and terrain on their geographic coverage. Currently, the spatiotemporal evolution patterns of ice disasters are not clear. The existing research on improving the resilience of power transmission networks considering the impact of ice disasters have not involved the temporal modeling of ice disaster scenarios. Therefore, the paper proposes a method for temporal modeling of ice storm scenarios based on multispectral satellite remote sensing. By combining multispectral remote sensing image fusion methods based on Laplacian pyramid decomposition, efficient extraction and analysis of the spatial distribution and temporal changes of ice-covered areas in Sentinel-2 satellite remote sensing images are achieved. Using partial differential convolution, ice-covered areas are predicted dynamically based on the fused images, and an ice disaster temporal model is constructed. Additionally, a conditional variational autoencoder is used to generate a set of ice disaster scenarios, which accurately reflect the spatiotemporal characteristics of "source-network-load" during ice disasters.
Considering the interaction between the disaster development process and resilience enhancement measures, the power transmission system resilience can be simultaneously enhanced through both pre-disaster prevention and in-disaster repair measures. This paper proposes a comprehensive resilience evaluation index and constructs a two-stage robust resilience enhancement planning model for power transmission networks based on the set of ice disaster scenarios. The first stage focuses on pre-disaster fixed energy storage configuration and pre-planning of maintenance resources to find the optimal investment decision. The second stage focuses on in-disaster power supply through fixed energy storage and emergency maintenance considering limited maintenance resources, ensuring rapid response from fixed energy storage and maintenance teams after the occurrence time of the ice disaster, which aims to ensure rapid load recovery, maximize system resilience, and minimize system economic losses. The model is iteratively solved using a parallelizable column-and-constraint generation algorithm.
Finally, case studies are conducted using ice-covered remote sensing data from a region in Yunnan and a modified IEEE RTS-79 power transmission system as the test system. The results show that the coordination of fixed energy storage power supply and emergency maintenance can effectively ensure power supply and transmission during ice disasters, as the system resilience improved by 90.97% and total system losses decreased by 43.19% during the ice disasters. Compared with other resilience enhancement strategies, the proposed strategy in this paper balances both economic efficiency and resilience. What’s more, different ice disaster center locations are set in the case study considering the inherent uncertainty of ice disasters. The results demonstrate that for ice disasters with multiple origins, the proposed method effectively ensures power restoration in the transmission system, enhances system resilience, reduces load shedding losses and total costs.

Electromagnetic pulse welding (EMPW), an advanced solid-phase welding technology for dissimilar metals, has garnered extensive applications across domains such as electric power transmission, automotive manufacturing, and refrigeration equipment due to its distinctive advantages. However, the Al-Cu joints welded by this technique encounter challenges regarding forming an intermediate layer comprising intermetallic compounds and cracks at the weld seam, which reduces the weld's mechanical performance. Based on the formation mechanism of the interface morphology and the necessary conditions for electromagnetic pulse welding, a method to regulate the electromagnetic pulse welding interface using a dual-coil structure was proposed. This method aimed to suppress the generation of the intermetallic compound intermediate layer in the weld seam by diminishing the horizontal component of the movement velocity at the welding interface, thereby reducing the shear effect at the interface. To validate the efficacy of this approach, an electromechanical coupled finite element simulation model was utilized to compare the electromagnetic parameter distribution characteristics during the EMPW process based on single and dual-coil structures. The experimental results from the high-speed camera verified the simulation of the plate movement process and results revealed that the horizontal component of interface velocity decreased by using the dual-coil structure. A scanning electron microscope was employed to analyze the micro-morphology of the welding interface. The results showed that the welding interface based on a dual-coil structure mainly included the wave and straight types, while the interface via single-coil included the vortex type. The findings indicated that joints welded using a single-coil structure EMPW method exhibited a pronounced intermediate layer at the interface. In contrast, those welded using the double-coils structure EMPW method failed to show the formation of an intermediate layer at the interface, exhibiting a reduced shear effect on the interface morphology and superior mechanical properties. Besides, the line scanning results of the welding interface based on a dual-coil structure reflect a monotonic change in elements, while the welding interface of a single-coil structure exhibits regional oscillations in elements. Overall, the effectiveness of this method in suppressing the formation of intermetallic compounds was validated at the interface. Utilization of a dual-coil structure can reduce the shear effect at the interface by controlling the horizontal component of the plastic flow, thereby suppressing the formation of intermetallic compounds and enhancing the tensile performance of the welded joints. This study contributes to understanding the physical mechanisms of the electromagnetic pulse welding process, which is of great significance for the research and development of high-performance, lightweight heterogeneous metal composite materials and the advancement of lightweight manufacturing.

Polymer insulation materials such as epoxy resins generate micro-scale damage under long-term electrical-thermal aging and mechanical stress, which induces insulation failure and seriously threatens equipment operation safety. Microcapsule technology realizes the independent repair of micro-scale damage of insulating materials, however, most of the existing microcapsule self-repairing technology adopts liquid repairing agent, which has the problems of irreversible curing and only single repairing, and also needs a strong external force to be triggered passively. In this paper, microcapsules with magnetic field targeting effect composed of the phase change material octacosane ware prepared by using Fe₃O₄@SiO₂ nanoparticles as Pickering emulsion stabilizers, which were composited with normal temperature curing epoxy resin to form an insulating material with self-repair function. The solid-liquid transformation of the phase change material octacosane repair agent is reversible, which gives the composite material the property of being able to be repaired repeatedly.
Ultrafine Fe₃O₄@SiO₂ nanoparticles were used as the oil-in-water emulsifier. During the formation of phase change microcapsules, Fe₃O₄@SiO₂ nanoparticles were at the junction of water and oil (melted eicosanoids), and when the eicosanoids were cooled down to room temperature, the Fe₃O₄@SiO₂ nanoparticles were wrapped around and embedded in the outer surface of solid eicosanoids, thus forming phase change microcapsules. The Fe₃O₄@SiO₂ nanoparticles embedded on the surface of the solid eicosanoids reparative material have the dual functions of targeted migration in response to a directional magnetic field and focused infrared targeted heating, which can attract the microcapsules to the damage-prone parts of the composite material under the action of a directional magnetic field. At the same time, an appropriate amount of silane coupling agent-modified Al₂O₃ nanoparticles were introduced into the epoxy resin matrix to enhance the thermal conductivity and insulation strength of the composite material. When microdamage was generated, focused infrared light was applied artificially and conveniently under charged conditions to target heating of the microcapsules, which induced the phase change microcapsules in the damaged area to melt and flowed out rapidly to fill the damaged channels. Upon cooling and solidification, the material realized autonomous repair. In this paper, the microstructure and thermal stability of the microcapsules and the insulating and thermal conductivity of microcapsules/nano-Al₂O₃/epoxy composites were experimentally investigated, and finally the self-repairing performance of the composite insulating material was tested on the surface of the mechanical scratch damage to verify the self-repairing characteristics of the composite material.
The following conclusions can be reached from test analysis: (1) The particle size of the microcapsules is uniformly distributed, and the cumulative 80% frequency range is concentrated in 50.02~138.56 μm. Additionally,they maintain stability and do not decompose thermally below 200℃. (2) The magnetic targeting induction technology can improve the self-repairing efficiency of the material and reduce the doping amount of the microcapsules, so as to maintain the good intrinsic performance of the substrate; The doping of nano-Al₂O₃ particles endows the composite material with excellent thermal response characteristics for targeted infrared radiation heating. (3) The relative dielectric constant of the 2% microcapsules/1% Al₂O₃/EP composites is approximately equal to that of the pure epoxy resin, and the dielectric strength has been improved by 2.32%. The composites are capable of repairing mechanical scratch damage autonomously, and can fully fill the scratch damage channels on the material surface. The insulation strength can be restored to 90.78% of the undamaged one.