碳纤维/环氧树脂超薄预浸料成型工艺及胶膜匹配性研究

采用DSC分析了超薄碳纤维预浸料CF832/T700所用树脂体系的固化反应动力学参数,通过正交试验研究了预吸胶工艺参数及固化工艺参数对超薄碳纤维复合材料层合板力学性能的影响规律,选用EA9696NW、LWF–2B和FM73M 3种不同胶膜对超薄预浸料面板与蜂窝芯共固化以确定最匹配的胶膜。结果表明,CF832/T700预浸料的固化反应活化能为85.98k J/mol,反应级数为一级反应,固化反应较慢,前固化温度、固化温度和后固化温度分别为115℃、135℃、171℃;通过弯曲及拉伸性能确定出的最佳预吸胶工艺参数为预吸胶温度60℃、预吸胶压力0.3MPa、预吸胶时间10min,最佳固化工艺参数为固化温度130℃、固化压力0.4MPa、固化时间2.5h;EA9696NW胶膜对超薄预浸料面板及蜂窝芯的共固化效果最好。     

非等温DSC 研究低共熔点芳胺/ 环氧E44 固化动力学

采用非等温DSC法对低共熔点芳胺固化剂/环氧E44体系进行了固化动力学研究,通过Kissinger、Ozawa和Crane方法获得了该体系固化动力学参数:表观活化能E=49.2 kJ/mol,固化反应级数n=0.95,频率因子A=2.60×105s-1.固化动力学方程可表示为:((dα)/(dt))=2.60×105(1-α)0.95exp(-(49200/RT)).初步确定了该体系固化工艺条件为50℃/2 h、140℃/2 h、200℃后处理2h.填料B4C加入量对该体系固化过程的DSC曲线几乎无影响.     

苯并噁嗪/ BMI/ 环氧树脂的固化动力学

制备了苯并噁嗪树脂/BMI/环氧树脂三元体系,采用动态DSC分析了三元体系的固化反应过程。并用Kissinger和Ozawa方法分别求得三元体系的反应活化能为89.5 kJ/mol。由Crane理论计算得到该体系的固化反应级数n=0.93级反应;根据计算的动力学参数,建立了三元体系的固化动力学模型。利用所建立的固化动力学模型分别预测了等温和动态条件下,三元体系的固化反应特性。得到了三元体系的固化工艺为180℃/1 h+200℃/2 h+230℃/2 h,后处理工艺为250℃/2 h。     

PBT/N100黏合剂体系固化流变性能北大核心CSCD

为深入研究黏合剂3,3-双(叠氮甲基)氧丁环-四氢呋喃共聚醚(PBT)与固化剂多异氰酸酯N100的固化反应过程,使用流变仪研究了PBT/N100黏合剂体系固化过程中的模量变化和凝胶化之前的黏度变化。结果表明:PBT/N100黏合剂体系的等温固化过程遵循自催化动力学模型。根据模量随时间的变化,PBT/N100黏合剂体系的固化过程可分为反应控制阶段、凝胶化阶段和扩散控制阶段。其中,反应控制阶段的黏度变化符合双Arrhenius模型,计算得到该阶段的粘流活化能和反应活化能分别为36.271 kJ/mol和54.882 kJ/mol。通过Eyring模型,计算出PBT/N100黏合剂体系固化过程的热力学参数∆H和∆S,分别为52.07 kJ/mol和-125.55 J/(mol·K),由此基本确定,PBT/N100黏合剂体系比较理想的等温固化温度为60℃,固化时间约为160 h。     

NY9200G树脂体系非等温DSC法固化动力学研究

通过非等温DSC法测试研究热熔法预浸料用NY9200G树脂体系的固化动力学,讨论了升温速率对固化特征温度的影响;用kissinger公式以及Crane公式计算得到了表观活化能、固化反应级数以及频率因子等固化动力学参数,为模拟固化反应动力学模型奠定了基础。     

镁酚醛树脂的固化特性

文摘采用差示扫描量热法和傅里叶红外光谱法研究了镁酚醛树脂的固化反应特性,包括反应动力学和固化反应机理,热失重研究树脂固化后的耐热性能。研究表明:镁酚醛树脂表观活化能约为82.42 kJ/mol,反应级数为0.913,和普通酚醛树脂固化过程相比反应中有新的结构变化,热失重测试结果表明其耐热性能优异、残碳率较高,在以升温速率为10℃/m in条件下升温至800℃时残碳率可达到58.57%。镁酚醛树脂加热可快速固化,最佳固化成型温度控制在150~160℃。     

OoA成型T800/607复合材料制备及性能

采用非等温DSC对非热压罐(OoA)成型环氧树脂基体607进行了固化动力学研究,确定了树脂的固化动力学方程。制备了T800/607热熔预浸料和复合材料单向板,并比较了热压罐和OoA成型工艺下T800/607复合材料的性能。结果表明:该类预浸料室温储存期大于30 d,OoA成型质量优异,复合材料孔隙率远低于1%。OoA成型复合材料的弯曲强度为1 480 MPa,层剪强度为96.7 MPa,与在热压罐条件下固化的复合材料性能相当。     

结构复合材料用耐高温环氧树脂体系

研制的603耐高温环氧树脂体系的T<,g>约为225℃,热分解温度约为387℃;采用凝胶时间、DSC和流变特性表征了其固化反应特性,确定了固化工艺;603树脂体系可以湿法和热熔法制备预浸料,预浸料铺覆工艺性优异,T700/603和T800/603复合材料可作为高性能复合材料结构件使用.     

基于DSC 法的RTM 工艺用6421 双马树脂固化反应分析

采用DSC方法分析了RTM工艺用6421双马树脂的固化反应,确定了固化度与温度和固化反应速率与时间之间的关系,基于Melak方法分析了固化反应过程,通过数据拟合法得到了n级固化模型、自催化模型及Kamal模型方程中的各个参数值。根据相关系数R2确定了适合的动力学模型。结果表明,6421双马树脂的固化度—温度曲线呈现"S"型,固化反应速率随升温速率的增大而增大;树脂固化反应的表观活化能Ea为105.611 kJ/mol,其固化动力学模型符合Kamal固化模型,模型方程对实验数据拟合结果良好。     

一种高温固化环氧树脂性能研究

研究了BC2526树脂的固化工艺、动力学参数、复合材料耐热性和力学性能。通过热分析确定了树脂的基本固化工艺,采用K issinger和Ozawa方法计算出树脂的表观反应活化能,其平均值为91.86kJ/mol,结合Crane公式求出反应级数为0.940。还讨论了碳纤维复合材料的耐热性和复合材料力学性能。     

基于飞机油箱模型形状特征油量测量切片步长选择方法研究

 在分析飞机数字式油量测量过程中目前广泛使用的切片法油量测量原理的基础上,针对现有的定步长切片法无法得到准确、可靠的燃油质量特性数据库的缺陷,结合对飞机油箱模型形状特征的分析,提出了基于飞机油箱模型形状特征的油量测量切片步长选择方法。此方法包括切片步长整体和局部选择两个过程,整体选择以实现相邻两切片平面所夹油箱模型体积近似相等为目的来确定切片步长,以体现油箱模型截面整体变化规律;局部选择以设计切片平面与截面突变平面重合或尽可能接近的方式,突出油箱截面的局部变化特征。实验结果表明：该切片步长选择方法较定步长方法能够建立更为合理、可靠的燃油质量特性数据库,从而提高了油量测量精度。     

The effect of inlet conditions on the flow and heat transfer in multiple rotating cavity with axial throughflow

This paper discusses experimental results from two different build configurations of a heated multiple rotating cavity test rig.Measurements of heat transfer from the discs and tangential velocities are presented.The test rig is a 70% full scale version of a high pressure compressor stack of an axial gas turbine engine.Of particular interest are the internal cylindrical cavities formed by adjacent discs and the interaction of these with a central axial throughflow of cooling air.Tests were carried out for a range of non-dimensional parameters representative of high pressure compressor internal air system flows(Re up to 5×106 and Rez up to 2×105).Two different builds have been tested.The most significant difference between these two build configurations is the size of the annular gap between the(non-rotating) drive shaft and the bores of the discs.The heat transfer data were obtained from thermocouple measurements of surface temperature and a conduction solution method.The velocity measurements were made using a two component,LDA system.The heat transfer results from the discs show differences between the two builds.This is attributed to the wider annular gap allowing more of the throughflow to penetrate into the cavity.There are also significant differences between the radial distributions of tangential velocity in the two builds of the test rig.For the narrow annular gap,there is an increase of non-dimensional tangential velocity V/Ωr with radial location to solid body rotation V/Ωr=1.For the wider annular gap,the non-dimensional velocities show a decrease with radial location to solid body rotation.      

二维翼段颤振的μ控制

 采用超声电机作为作动器来实现含控制面的翼段颤振鲁棒抑制。针对作者设计的二维翼段颤振主动抑制系统，通过理论与实验相结合的方法，建立了考虑沉浮方向阻尼和作动器模型参数不确定性的控制系统模型，设计了μ控制器，并对控制器做了降阶处理。数值仿真和风洞试验表明，μ控制器可有效地抑制颤振的发生，将颤振临界速度提高23.4%。相对于H_∞控制器，μ控制器的控制效果和鲁棒性更好。     

Abnormal Shape Mould Winding

为解决网格化芯模的缠绕问题,本文提出了复合材料面片缠绕机理;接着详细分析了面片缠绕过程中的芯模凹曲面上纤维滑线和架空现象,应用微分几何曲面理论和空间几何理论,提出判据及其解决方案;最后,针对飞机发动机进气道的缠绕成型,编制缠绕控制程序并进行相应的实验,验证了面片缠绕方法的可行性。     

基于H∞性能指标的质量矩拦截弹鲁棒控制

 以所建立的质量矩拦截弹数学模型为基础，利用微分几何的反馈线性化理论，得到一个解耦线性系统，考虑到拦截弹的鲁棒性要求和3个滑块的协调控制问题，提出采用双回路的设计方法，内回路采用线性二次调节器（LQR），外回路采用考虑混合灵敏度问题的H_∞控制设计。仿真结果证明了该方法动态性能满足设计要求，同时对系统参数的不确定性具有较强的鲁棒性。     

航天器返回地球的气动特性综述

航天器返回地球的飞行过程中,气动特性是实现将宇宙飞行速度减到落地前速度、保证再入飞行得到有效控制以及再入防热安全可靠的关键因素。针对简单旋成体气动外形、半弹道式再入控制、烧蚀防热类返回航天器,综述了返回地球过程中变化的空气流域特性、航天器周围的气体绕流环境、空气与航天器作用产生的动力学与热效应等。系统地给出了该类航天器的再入气动特性参数与飞行性能的共性规律,包括:气动阻力与再入减速、气动升力与再入轨迹控制、配平攻角与飞行稳定性、气动加热与防热,以及再入过程中不同气动特性航天器、气象条件变化等对再入飞行性能的影响规律。为航天器开展返回飞行过程的跨流域气动性能工程研制提供设计参考。     

Research on Auto-detection for Remainder Particles of Aerospace Relay Based on Wavelet Analysis

Aerospace relay is one kind of electronic components which is used widely in national defense system and aerospace system. The existence of remainder particles induces the reliability declining, which has become a severe problem in the development of aerospace relay. Traditional particle impact noise detection (PIND) method for remainder detection is ineffective for small particles, due to its low precision and involvement of subjective factors. An auto-detection method for PIND output signals is proposed in this paper, which is based on direct wavelet de-noising (DWD), cross-correlation analysis (CCA) and homo-filtering (HF), the method enhances the affectiv-ity of PIND test about the small particles. In the end, some practical PIND output signals are analysed, and the validity of this new method is proved.     

Effects of Mo on the Microstructure and Hydrogen Sorption Properties of Ti-Mo Getters

The effects of Mo on the microstructure evolution, porosity and hydrogen sorption properties of Ti-Mo getters are investigated in this work. The results show that the addition of Mo prolongs the densification process of Ti-Mo getters and results in a significant amount of sintered pores. With the Mo content increasing, the porosity of getters firstly increases reaching the maximum value as it at- tains about 7.5wt.%, and then drops. At the room temperature, the hydrogen sorption property of getters increases progressively with the Mo content increasing, but the tendency is not very clear before its content lies below 2.5wt.%. When the Mo content achieves about 7.5wt.%, the hydrogen sorption property proves to be the best. The discussion is made about the above mentioned phenomena inclusive of hydrogen sorption properties of getters under different activation conditions (from 500-750 ℃).     

Preparation of Highly Dispersed Antimony-doped Tin Oxide Nano-powder via Ion-exchange Hydrolysis of SnCl4 and SbCl3 and Azeotropic Drying

Antimony-doped tin hydroxide colloid precipitates have been synthesized by hydrolysis of SnCl4 and SbCl3 using: (1) an ion-exchange hydrolysis to remove chlorine ions, and (2) isoamyl acetate as an azeotropic solvent to obviate water. The obtained dried powder is of high dispersivity without any need for further grinding. The size and dispersivity of the final particles are investigated with the aid of TG-DTA, BET, XRD and TEM. After having calcined, the antimony-doped tin oxide nanopowder possesses a tetragonal rutile structure with high dispersivity, uniform particles and low hard agglomeration.