关键词： Flame resistance  

摘要： The inherent flammability of polyethylene terephthalate (PET) poses a considerable threat to human lives and property, yet conventional flame retardants fail to adequately address both flame resistance and melt-drop concerns. To effectively enhance both the flame retardancy and melt-drop resistance of PET, a novel nanocarbon-method. The morphology structure and thermal stability of CNSs-BA were characterized. The flame retardancy of based composite flame retardant, CNSs-BA, was prepared by grafting aromatic Schiff bases (BA) on the surface of carbon nanospheres (CNSs), and the composite was prepared by introducing CNSs-BA into PET via melt blending CNSs-BA/PET composites and its flame retardant mechanism were investigated. The results show that the CNSs-BA with the addition of just 2.0wt% of CNSs-BA, the limiting oxygen index (LOI) of the CNSs-BA/PET composite increased significantly from 21.0% to 28.1%, achieving a UL-94 V-0 flame retardant grade. Furthermore, the peak heat exhibit a spherical shape with a particle size approximating 50 nm and possess remarkable thermal stability. Notably, release rate was reduced by an impressive 46.3%. The investigation into the flame retardant mechanism revealed that the CNSs-BA/PET composite exhibits a typical condensed-phase flame retardant behavior. The introduction of CNSs-BA greatly enhances the char formation of PET, with the high-temperature char residual of the composite increasing by 55.4% compared to pure PET, and the actual value of char formation exceeds the theoretical value. Moreover, the addition of CNSs-BA flame retardant triggers high-temperature crosslinking in PET after melting, leading to a substantial improvement in the density, continuity and thermal stability of the char layer formed during the combustion of the CNSs-BA/PET composite. © 2025 Beijing University of Aeronautics and Astronautics (BUAA). All rights reserved.

关键词： Tensile testing  

摘要： Flexible resistive strain sensors, as an important category of flexible sensors, have been widely applied across various fields due to their good flexibility, simple structure, and easy data readout. In existing studies, conductive fillers used in composite materials for filled strain sensors mainly consist of metallic conductive powders and carbon-based conductive powders, with few reports on the use of conductive polymers alone. Polypyrrole nanotubes (PPy-N) were synthesized by chemical oxidation polymerization using methyl orange (MO) as a dopant and anhydrous ferric chloride (FeCl3) as an oxidant, with a high conductivity of up to 121.70 S·cm−1. PPy-N were used as conductive fillers and thickeners, and polydimethylsiloxane (PDMS) was used as the matrix to prepare printing ink by mechanical blending. The printability and rheological properties of the ink were characterized using a direct-writing 3D printer and an intelligent rheometer. The 3D printed samples were characterized and tested using SEM, intelligent tensile tester, digital multimeter, DSC and other instruments to investigate the effect of PPy-N concentration on the microstructure, electrical properties, mechanical properties, differential thermal properties, dynamic thermodynamic properties, and strain sensing properties of PPy-N/PDMS composite materials. The results show that the ink exhibits good printability when the concentration of PPy-N reaches 5.98wt%~7.56wt%. The ink with 5.98wt% shows superior performance in 20-layer continuous printing tests, with the printed dumbbell-shaped tensile specimens achieving a tensile strength of 3.02 MPa and an elongation at break of 178.64%, and a high gauge factor (GF) of 36.14. In 100-cycle tensile tests, the ink shows low resistance signal peak stability coefficient (α=1.714) and shoulder peak proportion (Psp=9.8%). It also exhibits good durability and stability in 1 000-cycle tensile tests. The skin sensor patches made from this ink exhibit good signal stabil

关键词： Creep  

摘要： The composite cylindrical grid structures exhibit quite a few features and complex structural characteristics, and its precision in manufacturing is restricted due to the curing deformation. Based on the viscoelasticity of the bismaleimide resin, high temperature creep tensile testing of the aerospace 802 bismaleimide resin was performed, confirming the existence of unrecoverable viscous flow strain after the unloading of the bismaleimide resin creep. The micro component material mechanism was revealed to reduce the process curing deformation of large composite grid structures through hot sizing. The deformation energy increment theory for composite grid structures was derived and established. The process of hot sizing load application, relaxation, and rebound of composite grid structures was simulated. The correction rebound profile of grid structures was determined, comparing with experimental results to verify the effectiveness of the deformation energy increment theory. The failure of internal stress, number of correction points and process conditions based on time temperature equivalence of hot sizing composite grid structure was analyzed. A complete process for the deformation simulation method of hot sizing deformation control for composite grid structures formed. © 2025 Beijing University of Aeronautics and Astronautics (BUAA). All rights reserved.

关键词： Wetting  

摘要： Currently, the pollution of global water resources and the scarcity of fresh water are increasingly severe. The pressing need for research on purifying and reusing unconventional water resources such as seawater, brackish water, industrial wastewater, and domestic sewage necessitates an effective, environmentally friendly, and low-carbon solution strategy that harnesses the synergistic effect of specialized wetting materials and photothermal conversion. This paper begins by summarizing the research status of conventional water purification materials while highlighting their advantages, disadvantages, and challenges in current technology. Subsequently, it systematically discusses the action mechanism and research progress of individual specialized wetting materials and photothermal conversion materials in the field of water purification. Furthermore, it thoroughly analyzes the synergistic mechanism and working principle between specialized wetting effects and photothermal effects at an application level in water purification. The analysis includes examining their advantages in solar energy utilization, benefits to water purification processes, sustainability performance aspects as well as application scenarios. Additionally summarized is an analysis of the current application status of super-wetted photothermal composites within the field of water purification. Finally, this paper expounds upon existing limitations while prospecting future prospects for super-wetted photothermal composites within the realm of water purification. © 2025 Beijing University of Aeronautics and Astronautics (BUAA). All rights reserved.

关键词： Strain hardening  

摘要： Ni/SiC ceramic metal-based nanocomposites exhibit outstanding mechanical properties and radiation resistance, making it a promising candidate for essential structural materials in molten salt reactors. This study utilized molecular dynamics simulation to investigate the influence of uniaxial tensile rate and volume fraction (VF) of SiC on the tensile mechanical properties of Ni/SiC nanocomposites, as well as to reveal the deformation mechanism during uniaxial tensile. The results demonstrate a semi-logarithmic relationship between the Young's modulus and strain rate of Ni/SiC composites, with the yield strength being correlated to the tensile rate. When the tensile rate was less than 1×109/s, the yield strength remained essentially unchanged. However, when the tensile rate exceeded this threshold, the yield strength increased with the increase in tensile rate. Additionally, the VF of SiC significantly influenced the tensile mechanical properties of Ni/SiC nanocomposites, with critical volume fraction (CVF) of SiC calculated to be 0.299±0.04. When VF of SiC was below the CVF, the uniaxial tensile properties of Ni/SiC nanocomposites were mainly determined by the properties of the Ni matrix, and strain hardening was not observed. The deformation mechanism was attributed to the release a large number of dislocations at the Ni-Ni interface, demonstrating excellent plasticity. Conversely, when the VF of SiC exceeds the critical value, the mechanical behavior of Ni/SiC nanocomposites was primarily affected by SiC, leading to increased strain hardening and brittleness. The initial cracks formed at the Ni-Ni interface and propagated with increasing strain, with the slip of the Ni-Ni interface and the rotation of SiC grains are identified as the main reasons for the plastic deformation of Ni/SiC. These findings contribute to a better understanding of the mechanical properties of Ni/SiC composites and their potential applications, offering valuable guidance for the selection o

关键词： Topology optimization   Fiber-reinforced composite structure   Generative and adversarial networks   Additive manufacturing  

摘要： This paper presents a deep learning-based topology optimization method for the joint design of material layout and fiber orientation in continuous fiber-reinforced composite structure (CFRCS). The proposed method mainly includes three steps: (1) a ResUNet-involved generative and adversarial network (ResUNet-GAN) is developed to establish the end-to-end mapping from structural design parameters to fiber-reinforced composite optimized structure, and a fiber orientation chromatogram is presented to represent continuous fiber angles;(2) to avoid the local optimum problem, the independent continuous mapping method (ICM method) considering the improved principal stress orientation interpolated continuous fiber angle optimization (PSO-CFAO) strategy is utilized to construct CFRCS topology optimization dataset;(3) the well-trained ResUNet-GAN is deployed to design the optimal structural material distribution together with the corresponding continuous fiber orientations. Numerical simulations for benchmark structure verify that the proposed method greatly improves the design efficiency of CFRCS along with high design accuracy. Furthermore, the CFRCS topology configuration designed by ResUNet-GAN is fabricated by additive manufacturing. Compression experiments of the specimens show that both the stiffness structure and peak load of the CFRCS topology configuration designed by the proposed method have significantly enhanced. The proposed deep learning-based topology optimization method will provide great flexibility in CFRCS for engineering applications.

关键词： Self assembly  

摘要： The weak interface strength between carbon fiber (CF) and polymer matrix severely limits their practical application in fields such as automotive lightweighting. To address this issue, a series of boehmite/graphene with different contents were prepared by hydrothermal method and successfully introduced to the surface of CF via self-assembly method to modify the interface of carbon fiber/epoxy resin composites (CF/EPs). A series of tests were conducted to investigate the mechanical properties of the composites before and after modification and the results showed that the best performance was achieved when the boehmite/graphene mass ratio was 2∶1 (BG-2). Compared with CF/EP, the modified BGCF/EP-2 showed significant enhancements in interfacial shear strength (116.1%), interlaminar shear strength (56.0%), tensile strength (61.1%), and flexural strength (30.4%). Finally, the schematic diagrams of the possible multiscale interfacial modification mechanism in the CF/EPs were further analyzed based on the results of SEM images and contact angle tests. © 2025 Beijing University of Aeronautics and Astronautics (BUAA). All rights reserved.

关键词： Carbon nitride  

摘要： Carbon nitride (CN) is one of the most promising non-metal catalysts currently, but its photocatalytic activity is not ideal due to its poor carrier separation efficiency within molecules caused by its unique electronic structure. In order to improve its photocatalytic performance, N-doped g-C3N4 (NCN) was firstly prepared by high temperature condensation method using urea and citric acid as raw materials. Then, the CoS2-modified NCN composites (NCN/CoS2) were successfully prepared by photodeposition. The introduction of CoS2 effectively enhances the photogenerated carrier separation efficiency of carbon nitride. At the same time, N doping effectively regulates the band gap of carbon nitride and broadens the visible light response range of carbon nitride. The photocatalytic hydrogen production results show that under visible light irradiation (λ>420 nm), the NCN/10CoS2 presents the best photocatalytic hydrogen production performance (73.8 μmol·g−1·h−1), which is 4.9 and 10.4 times higher than that of NCN (15.0 μmol·g−1·h−1) and g-C3N4/10CoS2 (7.1 μmol·g−1·h−1), respectively. © 2025 Beijing University of Aeronautics and Astronautics (BUAA). All rights reserved.

关键词： wave-absorbing SiC fibers   fiber surface coating   stacking structure   computational optimization  

摘要： Structure modulation at multiscale is crucial for optimizing the electromagnetic wave absorption (EWA) properties of fiber-reinforced composites. Here we selected two types of wave-absorbing SiC fibers as reinforcements. The L-fiber had a relatively low resistivity of similar to 3 Omegacm and the H-fiber had a high resistivity of similar to 7x10(5)Omegacm. To adjust the impedance, BN single coating and SiO2/BN dual-coating were prepared respectively on the L-fibers. Unidirectional prepregs with different fibers were stacked in different rules to obtain the final composites. It showed that both the fiber coatings and stacking structure significantly influence the EWA performance of the composites. Guided by computational optimization, the stacked composites exhibited superior reflection loss (RL) lower than -10 dB across the whole X (8.2-12.4 GHz) and Ku (12.4-18.0 GHz) bands. It is interesting to find that the introduction of the surface coatings on the L-fibers significantly widens the available thickness range of the stacked composite for possessing excellent performance. In particular, dual-coating perform better in terms of broadening the available thickness range of the stacked composites.

关键词： 钨纤维增强金属玻璃复合材料   斜侵彻   穿甲   自锐   弹道特征   有限元模拟  

摘要： 基于钨纤维和金属玻璃基体的实际分布特性,建立复合材料弹体的细观有限元几何模型,采用修正的热力耦合本构模型来描述金属玻璃基体的高强度和高剪切敏感性,结合相关的斜侵彻/穿甲试验,开展复合材料长杆弹斜侵彻/穿甲钢靶的三维有限元模拟,与钨合金弹进行对比分析,讨论弹靶变形和破坏特征,分析了撞击倾角、撞击速度等因素对复合材料弹体侵彻/穿甲"自锐"行为以及弹道特征的影响.结果表明,在斜侵彻/穿甲条件下,由于弹体头部受力的非对称特征,弹头逐渐锐化为非对称的尖头构型,同时弹道偏转,复合材料弹体的"自锐"性能以及侵彻/穿甲能力下降.撞击速度对斜侵彻/穿甲条件下弹体的"自锐"特征及弹道行为有显著影响,低速撞击条件下,撞击倾角越大,弹体侵彻性能越弱;当倾角增大到50°时,撞击速度小于900m/s的弹体均难以有效侵彻靶板;倾角进一步增大时,弹体容易跳飞.