New advances in fiber-reinforced composite honeycomb materials

In sandwich structures, lightweight cellular materials as the core hold the face sheets far away from the neutral axis to maximize the bending performance of the structure. Honeycomb materials as a major type of lightweight cellular materials have been widely applied in various fields, including aerospace, vehicle, marine, architecture and mechanical engineering, due to reliable mechanical properties and excellent designability. Using fiber-reinforced composites is an efficient method to develop ultralight honeycomb materials with superior mechanical behaviors. In recent years, fiber-reinforced composite honeycomb materials possessing lightweight and excellent mechanical performances have attracted noticeable attention to replacing traditional aluminum honeycombs and Nomex honeycombs. Compared to metal, polymer and Nomex paper, fiber-reinforced composites possess various merits, such as high specific stiffness and specific strength, excellent fatigue property, corrosion resistance and high-temperature resistance. Thus, the applications of fiber-reinforced honeycomb material for sandwich core have unlimited potential in hypersonic vehicles, long-range rockets, cargo vessels and protective systems. Although the fact that attention has been rapidly increasing, there is a lack of comprehensive reviews of new advances in the field of fiber-reinforced composite honeycomb materials. In this review, new advances reported by different scientists in the field of fiber-reinforced honeycomb materials have been reviewed and analyzed to provide an in-depth overview and knowledge for beginners in the field of ultralightweight and high-performance composite sandwich architectures. The challenges and prospects for the development of fiberreinforced honeycomb materials have also been presented.     

低能电子点源显微镜的研制及初步实验结果

研制了一台集低能电子点源显微镜和场发射显微镜于一体的设备。研制的过程中，解决了包括超高真空的获得，外界振动的隔离，爬行器及其控制电路的设计，场发射电流-电压自动测量，超高真空换样等一系列问题。利用该设备，获得了放大倍数大于10^4的投影像，并且测量了单根多壁碳纳米管的场发射特性。     

Thickness evolution of commercial Li-ion pouch cells with silicon-based composite anodes and NCA cathodes

It is significant to monitor the thickness change of commercial Li-ion pouch cells that are assembled from Si-based electrodes and layered cathodes since the volume variation is critically linked with kinetic reaction mechanism and chemomechanical degradation. In this work, the single-point and full-field measurements are conducted on the thickness evolution of Si Ox/Cgraphite/lithium nickel-cobalt-aluminum oxide(Si Ox-G/NCA) batteries. It is found that an abnormal overshoot that has been rarely observed in the previous studies appears at the beginning of discharge, which is believed to be the combined results between the rapid expansion of NCA and the contraction of graphite related to the state of charge(SOC). Compared with the results of single-point measurement, the spatial displacement distribution obtained from three-dimensional(3D) scanning suggests the full-field thickness evolution of the entire cell scale, which is more feasible and efficient to provide full-field information for supporting pouch cell design and pack integration.     

Electrochemomechanical coupled behaviors of deformation and failure in electrode materials for lithium-ion batteries

The growing demands of lithium-ion batteries with high energy density motivate the development of high-capacity electrode materials. The critical issue in the commercial application of these electrodes is electrochemomechanical degradation accompanied with the large volume change, built-in stress, and fracture during lithiation and delithiation. The strong and complex couplings between mechanics and electrochemistry have been extensively studied in recent years. The multi-directional couplings, e.g.,(de)lithiation-induced effects and stress-regulated effects, require cooperation in the interdisciplinary fields and advance the theoretical and computational models. In this review, we focus on the recent work with topics in the electrochemomechanical couplings of deformation and fracture of conventional and alloying electrodes through experimental characterization, theoretical and computational models. Based on the point of view from mechanics, the strategies for alleviating the degradation are also discussed, with particular perspectives for component-interaction patterns in the composite electrodes. With interdisciplinary principles, comprehensive understanding of the electrochemomechanical coupled mechanism is expected to provide feasible solutions for low-cost, high-capacity, high-safety and durable electrodes for lithium-ion batteries.     

某型航空发动机涡轮盘低循环疲劳寿命分析

确定发动机零部件的最大应力应变循环是进行零部件寿命研究的重要内容之一.弹塑性有限元分析常用于计算最大应力应变循环,但是由于各种载荷、约束等条件考虑不全面,得到的应力应变循环往往偏大.同时,某些零部件的瞬态温度场是决定其疲劳强度和使用寿命的重要因素,而获得准确的瞬态温度场是非常困难的.文中对某型发动机的高压涡轮盘进行疲劳试验条件下弹塑性有限元分析,对一台涡轮盘的残余应力进行测试,利用稳态温度场计算涡轮盘危险点最大应力应变循环,并根据弹塑性有限元分析和通过残余应力测试得到的最大应力应变循环进行低循环疲劳寿命预测.研究结果表明,弹塑性有限元分析法预测的寿命偏低,由残余应力可以较准确地确定最大应力应变循环.     

战神传说

本刊曾经在7月号介绍过RPG游戏《幻想传说》，今天介绍给大家的《战神传说》则是《幻想传说》的续作，在剧情上虽然与前作有所传承，不过完全是一个全新的故事。因此即使没玩过《幻想传说》的玩家，也不会存在任何的问题。作为制作方雅讯天地的重点作品，《战神传说》画面继承了前作《幻想传说》生动细腻的卡通风格，不仅剧情更为丰富精彩，整体游戏性也有所提升，是一款值得我们期待的游戏[编者按]     

High-value Applications of Nanocellulose

Nanocelluloses, obtained from the biopolymer cellulose, are a class of renewable functional nanomaterials with excellent properties and a broad range of applications. This review mainly illustrates practical and advanced applications of nanocellulose-based materials in the following categories. ① Fire-resistant materials: in the section on these types of materials, the fire-protection property of nanocellulose/clay hybrid composites (clay nanopaper) is illustrated; oriented montmorillonite (MTM) provides barrier properties and low thermal conductivity whereas cellulose nanofibers (CNFs) impart favorable charring. ② Thermal insulation materials: the best way to obtain materials with good heat insulation performance is to decrease the thermal conductivity of such materials. ③ Template materials: nanocellulose can direct the deposition and patterning of materials to form nanoparticles, nanowires, or nanotubes with improved properties.     

涡轴发动机综合飞行载荷剖面研究

根据疲劳、蠕变、热冲击损伤以及高周振动环境等效的原则,保证飞行载荷总谱和综合飞行剖面主循环数、次循环数、各载荷状态、各载荷状态持续时间相同,编制某涡轴发动机综合飞行剖面,为编制该发动机模拟任务持久试车谱、加速任务试车谱以及发动机零部件强度、寿命考核试验研究提供技术依据.首先根据飞行载荷总谱和使用环境确定三种飞行类别,选定综合飞行剖面的发动机工作参数,分别得到三种飞行类别主、次循环矩阵,进行归一化圆整处理.由时间分配谱统计各载荷状态的持续时间,进而编制综合飞行剖面.最后根据综合飞行剖面进行疲劳、蠕变和热冲击等损伤的误差分析.