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Multi-Scale Mechanical Properties of Three-Dimensional Braided Composite Structures
LUO Haibo;WANG Qian;YANG Yanchu;WU Jun;LI Tao;FENG Tao;HE Xiaohui;GONG Wentao;The mechanical properties of three-dimensional(3D)braided pre-embedded licker-in connecting tubular structures were investigated to provide a basis for near-space engineering applications.First, the meso-structure of a 3D braided unit cell was designed and analyzed to obtain fundamental mechanical parameters, such as elastic modulus and Poisson's ratio. Subsequently, tensile and compressive mechanical tests were conducted on 3D five-directional(3D5D)braided composite tubes with pre-embedded licker-in connections. The structural design parameters influencing load-bearing performance were analyzed, including the effects of the braiding angle, thickness, and configuration on the tube's load capacity.Finally, the failure mechanisms of the tubular structures were examined through damage morphology analysis, and macroscopic structural damage mechanisms were investigated using scanning electron microscopy.The results indicate that under the same outer diameter, 3D5D braided tubes exhibit higher tensile failure loads than 3D5D fully braided tubes. For tubes with identical braiding configurations and outer diameter,the wall thickness enhances compressive failure load, with the φ30t3-C tube achieving the highest compressive failure load and the failure mode being manifested as licker-in joint slippage. Meanwhile, both the-φ25t3-T and φ30t2.5-T tubes demonstrate high failure loads, with average tensile loads exceeding 120 kN and the failure mode involves licker-in joint pull-out and fiber bursting at the tube ends. The φ 30t3-T tube exhibits an average tensile failure load of over 105 kN. The findings serve as an important sci-entific reference for light-weight, high-strength load-bearing design and flight applications of near-space aerostats.
Ground-and Nearspace-Based Pseudolites Network Geometry Configuration Planning in Regional Navigation by Cooperation
QU Yi;WANG Sheng;FENG Hui;LUO Haibo;LIU Qiang;LI Cuichun;A nearspace-based cooperation pseudolite network geometry configuration planning algorithm was proposed to improve the regional navigation service performance provided by the cooperation of ground-and high altitude balloon(HAB)-based pseudolites. First, a pseudolite network geometry configuration performance indicator was designed based on geometric and horizontal dilations of precision in application scenarios of regional navigation by nearspace-based cooperation. Subsequently, the kinematic characteristics of HAB-based pseudolites and environmental wind field characteristics of nearspace were analyzed, and a HAB-based pseudolite trajectory adjustment strategy of actively changing flight altitudes and utilizing environmental wind field was constructed. Finally, a pseudolite network geometry configuration planning algorithm based on sine-cosine algorithm was proposed, with its constraints discussed and verified through simulations. The simulation results show that the proposed algorithm can effectively exploit the variation of environmental wind field with spatio-temporal conditions, and reasonably plan the flight trajectory of HAB-based pseudolites, thereby extending the service duration. It improves the geometric and horizontal accuracy factors of nearspace-based cooperation pseudolite networks, thereby optimizing the navigation service performance of pseudolite networks and providing technical references for the application of HAB-based pseudolites in navigation.
Post-Buckling Optimization of Composite-Stiffened Cylindrical Shells Incorporating Progressive Damage
WANG Yue;WANG Zhixiang;LI Daokui;To explore the load-bearing potential and failure modes of composite-stiffened cylindrical shells under axial compression, post-buckling analysis and optimization design were conducted by incorporating progressive damage. The ultimate load and failure modes were analyzed using the explicit dynamics method and Hashin failure criterion. On this basis, the influence of skin layup sequence on the ultimate load of three typical composite stiffened cylindrical shells was investigated. Furthermore, the sequential approximate optimization method was adopted to obtain the optimized structures of the three typical composite-stiffened cylindrical shells. The results demonstrate that under axial compression, the composite transverse hexagonal stiffened cylindrical shell structure shows significant advantages in both load-bearing capacity and efficiency, with improvements of 37.5% and 31.8%, respectively, compared with the initial design, and an increase in ultimate load by 10.6% and 4.4%, respectively,with respect to the other two configurations. Under axial compression, the sequential damage and failure of fibers and matrices are the main mechanisms of crushing failure of stiffened cylindrical shells. Therefore, post-buckling analysis should be carried out by comprehensively considering material damage and structural stability to obtain the ultimate load of composite-stiffened cylindrical shells.
Research Progress on the Preparation, Evaluation, and Optimal Design of Ablation-Resistant High-Entropy Coatings
LI Huidong;YUAN Xiaojing;LIU Haoyu;JIANG Nan;ZHANG Min;XU Dongsheng;LUO Weipeng;The reliable service performance of hot-end components has long been a research focus in the aerospace field, as key components of aerospace equipment are subjected to rigorous tests under complex conditions involving high thermal and loads. Under extreme enviroments, such as high-thermal and high-speed gas flow erosion, and ablation caused by high-energy weapons, thermal protective coatings are required to maintain stable high-thermal service capabilities. In recent years, high-entropy materials, characterized by excellent mechanical properties, thermal and chemical stabilities, have attracted significant attention in the aerospace material field. Accordingly, the design, preparation, and evaluation progress of ablation-resistant high-entropy coatings were reviewed to address the need for ablation-resistant components of hypersonic vehicles in long-duration flights. The optimization strategies for multi-component high-entropy materials and advanced preparation processes for thermal protective coatings were analyzed, and the performance control machanisms were explored, providing support for the preparation and performance enhancement of high-performance ablation-resistant high-entropy coatings.
Fatigue Damage Evolution Model for NEPE Solid Propellant Based on Dissipated Pseudo-Strain Energy
WU Fanji;ZHANG Wenqin;ZHANG Dapeng;LEI Yongjun;Cyclic tensile tests were conducted under stress-controlled conditions to address the issue of fatigue damage characterization in high-energy nitrate ester plasticized polyether(NEPE)solid propellants after long-term highway transportation. The dissipated pseudo-strain energy was adopted as the damage factor for the fatigue damage process of NEPE solid propellants. The fatigue damage evolution process was regarded as a superposition of the damages from creep, tensile-compressive fatigue, and fracture. A fatigue damage evolution model for NEPE solid propellants was constructed, and parameter analyses were conducted. The results indicate that NEPE solid propellants exhibit a significant stress-strain hysteresis characteristic, with strain lagging behind stress under stress-controlled cyclic loading, accompanied by energy dissipation phenomena. The defined damage factor can effectively quantify the damage evolution process. The fatigue damage evolution model can precisely characterize the three growth stages of NEPE solid propellants under cyclic loading, namely decay, steady-state, and accelerated growth. The maximum loading stress plays a decisive role in fatigue damage evolution. When the maximum loading stress decreases, the dominant factor in damage evolution gradually shifts from creep damage to tensile-compressive fatigue damage.
Review on Dehazing Algorithm for Degraded Images in Complex Scenes
LI Qinghui;CUI Zhigao;CHEN Yuqiang;LAN Yunwei;CAI Yanping;SU Yanzhao;To address the issue of performance degradation in advanced visual tasks, such as object detection, semantic segmentation, and person re-identification caused by complex degraded images under haze weather conditions, an overview of dehazing techniques for degraded images in complex scenes was provided. First, the formation mechanism of haze images and the degradation models were introduced. Second, the evolution from conventional physical model-based image dehazing methods to current deep learning-based approaches was reviewed, providing a detailed analysis of the characteristics, advantages, and limitations of each method. Finally, common datasets and evaluation metrics in the field were presented and future development trends were discussed to provide valuable references for researchers in related fields and jointly promote image dehazing technologies towards a more intelegent and practical direction.
Construction of an Aircraft Multimodal Time-Sensitive Object-Detection Dataset
SHEN Tong;WANG Siyu;YANG Xiaogang;LU Ruitao;Rocket Force University of Engineering;To address the problems of existing multimodal object detection datasets, such as single target category, insufficient scene coverage, and image perspective mismatch with aircrafts, a multimodal time-sensitive object-detection dataset specifically designed for aircraft applications was constructed. This dataset aimed to provide data support for the training and evaluation of target detection algorithms. First,diverse time-sensitive target images were acquired by integrating real-scene shooting and remote sensing image platform generation. Second, spatial alignment among multimodal images was achieved using the SuperPoint and SuperGlue algorithms to ensure the positional consistency of targets across modalities. Furthermore, image synthesis and style transfer techniques were employed for data augmentation to balance the inter-modal distribution and expand the dataset scale. Finally, automatic annotation of time-sensitive targets was accomplished through a semantic segmentation algorithm. The experimental results demonstrate that compared with other multimodal target monitoring datasets, the constructed dataset is substantial in volume, diverse in target categories, and extensive in scene coverage.
Review of Simulation-Based Evaluation of Weapons and Ammunition Damage Effectiveness
XU Hengwei;LU Yonggang;LU Zhengcao;LI Junrun;FENG Xiaowei;LYU Xiao;Driven by the demands for intelligent and precision-based warfare, simulation-based evaluation technologies for weapons and ammunition damage effectiveness have become critical support tools in operational decision-making and equipment system optimization. This study provided a systematic review of evaluation methodologies, models, and software, tracing the development trajectory and representative research achievements in these areas. Particular emphasis was placed on simulation-based evaluation methods, represented by virtual model-based target vulnerability and explosive warhead evaluation methods. A comprehensive review of the research progress and existing challenges in warhead lethality, target vulnerability, ammunition-target interaction models, as well as overall damage assessment frameworks was provided. By comparing the technical characteristics of typical domestic simulation evaluation software, the key technological bottlenecks were identified in terms of adaptability to diversified combat needs and system interoperability. In view of future combat evolution trends, the study proposed key research directions for the standardization of warhead effect field modeling, refinement of damage effect analysis methods, and deep incorporation of artificial intelligence into evaluation frameworks, aiming to provide theoretical support and strategic guidance for future technological breakthroughs and system development.
