The results of quasi-static tensile experiments on the 20%(volume fraction) SiCp/2009Al composite show a significant dispersion of the mechanical properties such as failure strain. The effects of two uncertainties on macroscopic mechanical properties of the composite were investigated using a multiscale finite element approach. The distribution characteristics of failure strain and fracture energy, and their correlations were obtained from FE simulations of a series of mesoscale RVE models. Then combined with the macroscale model, the randomness of mechanical properties in various regions within the actual material can be characterized. The results of the quasi-static tensile simulations of the macroscale model show good agreement with the experimental results, and are also able to simulate the dispersion behavior of failure strain very well due to the introduction of material stochasticity.

The high-temperature compressive properties are indispensable mechanical performance parameters for the structural design of composites, but it is difficult to be measured effectively by traditional techniques. In this study, the high temperature compressive experiment of carbon fiber reinforced plastics (CFRP) laminates was conducted in high-temperature experimental system based on digital image correlation (DIC) method. And the compressive properties, stress-strain curves and the evolution of axial full-field strain of CCF300/5228A with 0 degrees and 90 degrees ply-ups at 130 degrees C were obtained. Moreover, they were compared with those obtained at room temperature. Furthermore, the fracture analysis of the compressed specimens was carried out through scanning electron microscopy (SEM), meanwhile the effects of high temperature and lay-up on the compressive properties were discussed combining with the experimental results. Finally, an experimental verification was carried out and the results obtained demonstrated the feasibility and reliability of the experimental system and relevant experimental methods. The results show that the retention rate of 0 degrees and 90 degrees compressive strength at 130 degrees C are 70.5% and 62.6%, respectively, while the retention rate of compressive modulus are 88.0% and 75.4%, respectively, indicating that the strength and modulus of the laminates which are controlled by the matrix are more sensitive to high temperature.

拉伸性能是复合材料层合板的基本力学性能,研究湿热环境对玻璃纤维复合材料拉伸性能的影响可以为复合材料工程应用提供重要参考.开展了不同湿热环境下的AC318/S6C10-800复合材料拉伸性能研究,分析了环境对AC318/S6C10-800复合材料弹性模量及拉伸强度的影响.研究结果表明,低温干态环境下强度性能数据相对室温环境略高,70℃湿态环境下强度性能最低,随着试验温度的升高,0.拉伸强度、90.拉伸强度基本呈线性下降趋势.研究结果为AC318/S6C10-800复合材料工程应用提供参考.

主要开展了AC318/S6C10-800复合材料的面内剪切和吸湿状态处理后面内剪切性能试验.试验环境为低温干态、室温干态、高温80℃干态和70℃、85％RH条件下平衡吸湿后55℃高温和70℃高温.采用ASTM D3518《聚合物基复合材料面内剪切性能标准试验方法》对AC318/S6C10-800复合材料进行面内剪切试验,测量面内剪切强度和模量等力学常数.研究结果为AC318/S6C10-800复合材料结构设计及工程应用提供参考.

制备了一批AC318/S6 C10-800玻璃纤维复合材料压缩试样,并根据ASTM D6641《聚合物基复合材料压缩性能标准试验方法》对AC318/S6 C10-800复合材料进行压缩试验,测量了压缩强度和压缩模量等力学常数.采用DOT/FAA/AR-03/19《聚合物基复合材料体系的材料认证(取证)和等价性:已更新程序》对AC318/S6 C10-800玻璃纤维复合材料压缩试样进行吸湿状态处理,分析了湿热环境对AC318/S6 C10-800玻璃纤维复合材料压缩力学性能影响.研究结果表明,低温干态环境下强度性能数据相对室温环境略高,70℃湿态环境下强度性能最低,为AC318/S6 C10-800玻璃纤维复合材料结构设计及工程应用提供重要参考.

The relationship between the direction cosine matrix (DCM) in the space field and DCM in the aeronautics field is derived,to meet the demand of hardware-in-the-loop (HWIL) simulation of near space hypersonic vehicle flight control system.Firstly,the coordinate transformation (CT) theory is introduced,and the conversion method between two cartesian coordinate system is Introctuced.As well as the relationship of DCMs between the matrix transformation under two different reference systems is presented.Then,the analyzes the relationship of coordinate frames between the space field and the aeronautics field.How to convert the coordinate frame in the space field to the coordinate frame in the aeronautics field is researched.Finally,the HWIL simulation indicates that the method is correct and feasible.It ensures the HWIL simulation of navigation system of near space hypersonic vehicle.

In this paper,the mathematic model of the permanent magnet synchronous motor(PMSM)was analyzed first,and then the simulation model of the non-salient-pole PMSM was established in the simulink of the Matlab based on the mathematic model of the PMSM.The control system adoped the classical three-close-loop structure.In this control system,the id=0 control strategy in current loop and PI control were used in speed loop,and also the fuzzy PI control in position loop which was realized by programming in the Matlab.Given the way of establishing the simulink model of every module in the Matlab given in this paper,and the transient processes of position,speed and torque were simulated and analyzed for the actual parameters of system project at the time of sudden load-add/unload.The simulation results,show the system is of good anti-interference and able to track the given position and speed quickly and accurately.

In this paper,introduced a kind of aviation actuation system made up of brushless DC motor(BLDCM)and mechanism of worm and gear.For the requirement of performance,the strategy of three closed loops control including position loop,speed loop and current loop were adopted.The control system was modelled and simulated in Matlab/Simulink.And the simulation results show that the time of response characteristic is shorter and precision is higher in the whole control system.The method of three closed loop control is feasible in aviation actuation system based on BLDCM.

A precise speed control system of brushless DC motor(BLDCM) is presented.The proposed system uses high performance digital signal processor(DSP) and complex programmable logic device(CPLD) as its core control component,software phase-locked loop technique is adopted to obtain precise control of motor speed.According to the measurement,the motor can get into phase-locked state in a wide speed range,and its speed feedback pulse which produced by rotor sensor can trail reference pulse stably and accurately,to achieve the same frequency and nearly the same phase.The experimental result shows that the system is practical and valuable in engineering.

A simulation model of a 6/4 poles switched reluctance generator(SRG) system was built to study the fault-tolerance performance of SRG System for More-Electric Aircraft(MEA).On the basis of this model,several fault conditions such as,converter switch fault,load fault,prime motor fault,phase windings fault and so on,were simulated,and the simulation results including output voltage and phase current were presented.This paper analyzed the mechanism of the fault running and presented some methods to avoid the destructive faults.The research results indicate that SRG has a better fault-tolerant capability and is applicable to the main source of electrical power of MEA.The modeling method and simulation results of fault have certain reference value to fault diagnosis and fault-tolerant research of SRG systems.

The paper tensile experiment and FEA methods were used to study the damage propagation and failure properties of stiffened composite panels with discrete-source damage.The research results indicate that a notched composite panel is suitable to simulate the discrete-source damage of the stiffened composite panels with discrete-source damage,and there is high strain concentration at the notch end.Break-through of the stringer made the load path changed.Based on the Hashin failure criterion,the FEA method with progressive failure procedure can be used to simulate the notched stiffened composite panels' damage progression and failure procedure effectively.The analytical results have a good correlation with the experimental data.

Systematic studies of purity and structural changes disorder carbon nanotubes, which were produced by a catalytic chemical vapor deposition method, with heat treatment from 1362 degrees C to 2100 degrees C were carried out. Energy dispersive spectrometry (EDS) spectra of MWNTs specimens before and after annealed showed that the greatest change of compositions of the specimens was observed after annealing at 1600 degrees C and impurities were efficiently removed at 1800 degrees C. Transmission electron microscopy (TEM) and Raman spectroscopy (Raman) analysis shows that impurities have been efficiently removed and some defects have been healed and graphitization of annealed MWNTs is high. With increasing heat treatment temperature, the structure of the carbon nanotubes changes from a relatively smooth surface to a rugged surface and forms energetically stable loops between adjacent active end planes both on the inner and outer surfaces.

以N2作载气,二茂铁作催化剂,高温催化裂解无水乙醇溶液,制备出纯度较高,管径分布在30 nm~40 nm的纳米碳管。利用SEM和TEM对纳米碳管的结构进行了表征。根据纳米碳管的微观形貌,给出了一种可能的生长机制。该制备过程不使用任何有毒有害物质,工艺简单,这对实现纳米碳管的规模生产具有重要意义。

Based on the frequency-hopping communications principle,a kind of underwater frequency-hopping communication plan(FH-MFSK) and the feasibility of applying frequency-hopping technology in underwater acoustic communication system are analyzed,and some effects of the underwater environment on frequency-hopping communications system are also discussed in this paper.Variable filter banks controlled by the frequency-hopping sequence as well as the spectrum estimation based on periodogram are presented in demodulation part,and verification is further made with simulation.The results show that this kind of underwater communication system has higher data rate under bad underwater conditions.

Carbon nanotubes (CNTs) grown on the carbon fiber/matrix interface can improve the interface bonding and accordingly increase the mechanical properties of carbon/carbon composites. Here we report the investigation of preparing CNTs by pyrolizing natural gas on carbon cloth using Ni powder (∼74 μm) and sulphur as catalysts. Multi-walled CNTs with 70–100 nm in diameter were obtained at 1050–1200 °C in a CVD system with flowing Ar. The as-obtained CNTs were of a good crystallinity and high purity, characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy (Raman). In situ catalytic growth mechanism was discussed.

提出了一种基于DSP实时处理的水下个人语音水声通信系统的设计方案,构建了通信系统的结构模型,方案中采用CELP码激励线性预测编码,差分MPSK调制,卷积信道编码,以及判决反馈均衡技术,并对其关键技术进行了性能仿真和分析比较.结果表明,该系统可满足语音信息在水下信道的传输,有良好的原始语音恢复性能,误码率在10-3以下,具有较好的开发潜力.