考虑温度环境下树脂基复合材料力学性能及模型研究

采用试验的方法研究了T300/QY8911-Ⅳ复合材料不同温度环境(室温、160,200,260℃)下的纵向拉伸、横向拉伸及面内切变力学性能,探讨了材料的模量、强度随温度变化的规律并提出了相应的力学模型.试验结果表明:在室温至200℃复合材料纵向拉伸模量、强度受温度影响较小,拉伸模量最大变幅为2.82%,强度为1.41%;当温度升高到260℃时,由于树脂基体变质,材料纵向拉伸模量与强度均下降,模量下降5.85%,强度下降7.01%(均相对200℃);横向拉伸和面内切变模量、强度受温度的影响较大,在160℃范围内,材料的平均模量分别下降了49.21%和70.34%,强度下降了38.49%和44.85%.当温度升至200℃时,材料的横向拉伸及面内切变模量与强度进一步下降,模量降幅为25.13%和38.30%,强度降幅为0.41%和15.95%.拟合结果表明:3个力学模型均适用于不同温度、载荷类型下的数据分布规律,但模型Ⅱ与模型Ⅲ对数据的拟合更准确.      

4211环氧树脂体系性能研究

对4211环氧树脂体系的化学性能和物理性能进行系统的研究,通过差示扫描量热仪(DSC)测试固化反应特性,利用流变仪分析成型工艺特性,通过动态热机械分析(DMA)研究树脂体系在不同固化工艺下的耐热性能,并通过力学试验机测试固化后树脂体系的力学性能.结果表明:4211环氧树脂体系具有较好的工艺性,固化物具有较高的耐热性能,表现为刚脆特性,断裂伸长率为1.1％;与M40高模量碳纤维的匹配性较好.     

块状RF 有机气凝胶的常压干燥制备及结构控制

以间苯二酚和甲醛为原料,无水碳酸为催化剂,在常压干燥条件下可成功制备出具有良好纳米网络结构的RF气凝胶。采用SEM、比表面测量仪及孔径分布仪(BET)等测试手段对其结构进行了表征与测试。结果表明,通过改变R/C可以实现有机气凝胶的颗粒直径及孔洞由纳米到微米级的连续调节.此外采用常压干燥法所得到的有机气凝胶样品具有321～632 kg/m3的低密度,其中密度为428 kg/m3的样品的比表面积为188 m2/g。     

In orbit performance of butane propulsion system

The present work focuses on the determination of the in orbit performance of the Alsat-1 microsatellite propulsion system. The satellite mass is 90 kg, of which 6.2 kg is the propulsion system dry mass. The system is a butane propulsion system using low power resistojet thruster with 2.3 kg of propellant. The liquefied butane gas was selected due to its higher storage density and safety compared to the other propellants used for microsatellites. The purpose of this paper is the analysis of the firings performed after the launch of the satellite and to evaluate the system specific impulse and thrust level during the system lifetime. A total of 273 firings were performed on the Alsat-1 propulsion system in the period between the end of 2002 and mid 2009, the cumulated firing time is more than 12 h 49 min. The analysis of all the propulsion telemetry data shows that the system provides a total mission delta V of 25.3 m/s which is more than the 10 m/s specified for this mission. Furthermore, the mission average specific impulse and thrust are respectively 99.9 s and 48.8 mN.     

基于湿热老化试验的NEPE推进剂贮存寿命预估

用NEPE推进剂进行湿热加速老化试验获得了推进剂在不同湿热老化条件下抗拉强度和弹性模量随老化时间的变化规律,建立了推进剂湿热老化失效物理模型,并提出了将弹性模量作为失效判据预估推进剂贮存寿命的方法。分别用抗拉强度和弹性模量作为失效判据,对推进剂贮存寿命进行估算。结果表明：将弹性模量作为失效判据预估NEPE推进剂贮存寿命的方法可行。     

民航地空通信干扰抑制系统的设计与实现

在中国民航空管地空通信经常受到无线电干扰,无法保障正常通信。从根本上解决民航地空通信干扰问题,对于有效保障民航安全具有重要的意义。结合民航VHF通信干扰源的特点,将基于恒模阵列的自适应信号处理技术应用于地空通信干扰抑制中,设计并实现了自适应干扰抑制实时系统,取得了很好的干扰抑制效果。     

基于隐马尔科夫模型的故障诊断系统研究

在制造行业中,机械设备的状态检测技术能提供关于设备运行状态的实时信息,为避免生产损失和减少设备的致命故障提供保障。提出了一套基于小波变换和隐马尔科夫模型(Hidden Markov Models,HMMs)的故障检测系统。提出了小波模极大值分布(Wavelet Modulus Maxima Distribution),并将之定义为诊断系统的观察量加以验证。同时该系统采用在线模型参数估计和培训算法,通过选取能最大化对数似然度的HMM模型,确定设备所处状态。     

测力仪校准方法的比较

介绍了中国ＪＪＧ１４４－９２、美国ＡＳＴＭ Ｅ７４－９５、国际标准化组织ＩＳＯ３７６－１９９９检定试验机所用测力仪的主要技术要求,并对此进行了比较。     

计入静位移作用的粘弹阻尼器双线性迟滞模型

在传统的粘弹阻尼器双线性迟滞模型基础上,为了便于参数识别,将滑移迟滞恢复力等效成黏性阻尼力与分段线性弹性力的联合作用,引入指数衰减函数表征弹性力及阻尼力随激振幅值的变化规律,并导出了带静位移的粘弹阻尼器复模量计算模型。提出一种结合复模量及迟滞回线进行参数识别的方法,并通过实例验证了改进模型的准确性及参数识别法的有效性。分析了静位移对迟滞回线及复模量的影响,结果表明:静位移的变化使得迟滞回线沿弹性力曲线移动,并由于非线性刚度的影响,迟滞回线的形状也发生了变化;在模型采用奇次弹性力和线性黏性阻尼力的条件下,储能模量随着静位移的变化成偶次函数的趋势变化,而耗能模量则不受静位移的影响;静位移对储能模量和耗能模量的影响源于粘弹阻尼器刚度和阻尼关于位移的非线性特性。     

Analysis on the Bonding Failure Mechanism of High Modulus Carbon Fiber Composites

In order to explore the bonding failure mechanism of high modulus carbon fiber composite materials, the tensile experiment and finite element numerical simulation for single-lap and bevel-lap joints of unidirectional laminates are carried out, and the stress distributions, the failure modes, and the damage contours are analyzed. The analysis shows that the main reason for the failure of the single-lap joint is that the stress concentration of the ply adjacent to the adhesive layer is serious owing to the modulus difference, and the stress cannot be effectively transmitted along the thickness direction of the laminate. When the tensile stress of the ply exceeds its ultimate strength in the loading process, the surface fiber will fail. Compared with the single-lap joint, the bevel-lap joint optimizes the stress transfer path along the thickness direction, allows each layer of the laminate to share the load, avoids the stress concentration of the surface layer, and improves the bearing capacity of the bevel-lap joint. The improved bearing capacity of the bevel-lap joint is twice as much as that of the single-lap joint. The research in this paper provides a new idea for the subsequent study of mechanical properties of adhesively bonded composite materials.