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通过湿热老化研究了F-12纤维在60、80℃相对湿度90%环境条件下的吸湿行为,并研究了此条件下拉伸强度、断裂伸长率以及弹性模量随老化时间的变化规律.结果表明:F-12纤维的吸湿行为符合Bagley和Long提出的两阶段吸湿模型;拉伸强度、断裂伸长率以及弹性模量在老化过程中并非呈持续下降趋势,而是起伏波动的,弹性模量与拉伸强度总体上有相同的波动规律;湿热老化中温度对拉伸强度影响较为明显,拉伸强度随着温度升高而降低,但温度对模量、断裂伸长率变化的影响规律不明显. 相似文献
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为了探究铺放工艺参数的变化对复合材料厚度方向力学行为的影响,通过面外拉伸实验分析了铺放压力与铺放温度对复合材料厚度方向面外拉伸强度与拉伸模量的影响,并对不同铺放工艺的试件失效模式进行了分析。试验结果表明,增大铺放压力会减小层间富树脂区厚度,使复合材料面外拉伸强度不断增大,当铺放压力为0.225 MPa时取得实验组最大值,与铺放压力0.075 MPa相较强度提升约13.1%,失效模式由纤维断裂与纤维层剥离的组合转变为纤维断裂;铺放压力的进一步增大会挤压层间树脂,改变树脂富集形态,使面外拉伸强度下降,剥离失效模式再度出现。实验用复合材料的适宜铺放温度为30℃,过高的铺放温度会导致孔隙率的上升,使复合材料的面外拉伸强度严重下降,裂纹扩展失去规律性;与铺放温度25℃相比,铺放温度为45℃时复合材料面外拉伸强度下降达19.2%,失效模式由纤维断裂与纤维层剥离的组合失效转化为单一的纤维层剥离失效。 相似文献
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通过拉伸实验获得碳纤维增强聚醚醚酮复合材料(CF/PEEK)拉伸性能随温度的变化关系,并利用扫描电子显微镜观察断口形貌,研究分析了材料高温损伤机理。结果表明,随着环境温度的升高,碳纤维/PEEK的弹性模量与拉伸强度显著降低,在温度达到220℃时,分别下降89.20%和71.18%;断裂伸长率持续上升,在220℃时达到8.84%。弹性模量与断裂伸长率在T_g附近变化显著,主要原因是高温下纤维/树脂界面脱粘和树脂由玻璃态转化为高弹态后拉伸性能的显著变化。借助有限元方法计算由该材料制成的驾驶舱方向舵踏板在不同温度下的疲劳寿命,得出疲劳寿命随温度的升高而下降。在Coffin-Manson方程和通用斜率方程的基础上总结得出该材料疲劳寿命与温度的关系。 相似文献
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本文研究了HTPB/AP推进剂中过氯酸铵(AP)含量对丁羟推进剂老化性能的影响。实验是在90℃的空气中进行的,老化性能以推进剂的拉伸性能、邵氏硬度、失重%、燃烧速度等项目为判据。实验结果表明:随着老化时间的增长,推进剂的最大强度增加;最大强度下的伸长率减小;邵氏硬度增加;失重%有缓慢的增多;而燃烧速度少量降低。推进剂中氧化剂AP含量的增多,或多或少有减轻推进剂性能老化变化的趋势,因而对HTPB推进剂老化性能的提高是有益处的。 本文对老化期间HTPB推进剂失重%所显现出来的特殊情况,作了理论上的解释。 相似文献
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NING Guo-dong ZHANG Shu-guang FANG Zhen-ping 《中国航空学报》2007,20(1):1-8
A method for the implementation of integrated three-degree-of-freedom constrained entry guidance for reusable launch vehicle is presented. Given any feasible entry conditions, terminal area energy management interface conditions, and the reference trajectory generated onboard then, the method can generate a longitudinal guidance profile rapidly, featuring linear quadratic regular method and a proportional-integral-derivative tracking law with time-varying gains, which satisfies all the entry corridor constraints and meets the requirements with high precision. Afterwards, by utilizing special features of crossrange parameter, establishing bank-reversal corridor, and determining bank-reversals according to dynamically adjusted method, the algorithm enables the lateral entry guidance system to fly a wide range of missions and provides reliable and good performance in the presence of significant aerodynamic modeling uncertainty. Fast trajectory guidance profiles and simulations with a reusable launch vehicle model for various missions and aerodynamic uncertain-ties are presented to demonstrate the capacity and reliability of this method. 相似文献
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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 总被引:1,自引:0,他引:1
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。 相似文献
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The effect of inlet conditions on the flow and heat transfer in multiple rotating cavity with axial throughflow 总被引:1,自引:0,他引:1
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. 相似文献
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Abnormal Shape Mould Winding 总被引:1,自引:0,他引:1
Fu Hongya Wang Xianfeng Han Zhenyu Fu Yunzhong 《中国航空学报》2007,20(6):552-558
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。 相似文献
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FU Hong-jun MA Chong-qi KUANG Nai-hang LUAN Shi-lin 《中国航空学报》2007,20(2):124-128
This work was dedicated to performing surface oxidation and coating treatments on carbon fibers (CF) and investigating the changes of fiber surface properties after these treatments, including surface composition, relative volume of functional groups, and sur- face topography with X-ray photoelectron spectroscopy (XPS) and atom force microscopy (AFM) technology. The results show that, after oxidation treatments, interfacial properties between CF and non-polar polyarylacetylene (PAA) resin are remarkably modified by removing weak surface layers and increasing fiber surface roughness. Coating treatment by high char phenolic resin solution after oxida- tion makes interface of CF/PAA composites to be upgraded and the interfacial properties further bettered. 相似文献
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Xu Chenghai Meng Songhe Zhang Mingfu Zuo Hongbo Wang Guigen 《中国航空学报》2007,20(5):475-480
本文利用有限元法对冷心放肩微量提拉法(SAPMAC)生长大尺寸蓝宝石单晶过程中的热应力进行了模拟计算,应用临界缺陷理论解释了裂纹的萌生与扩展机理。研究表明,晶体内的热应力主要与晶体生长速率,环境温度和结晶取向有关;较大热应力多出现在结晶界面,放肩、收尾以及直径急剧变化等位置;最大热应力总是出现在籽晶与新生晶体的界面附近。裂纹将在临界缺陷位置产生,并在应力作用下沿a或m面扩展。计算结果与实验结果基本吻合,通过晶体生长系统和生长工艺的改进,对晶体的开裂问题得到了有效的抑制。 相似文献
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CHENG Wen-yuan CHANG Yan CUI De-gang XIE Xiang-hui 《中国航空学报》2007,20(1):55-59
To solve the topology optimization of complicated multi-objective continuous/discrete design variables in aircmit structure design, a Parallel Pareto Genetic Algorithm (PPGA) is presented based on grid platform in this paper. In the algorithm, the commercial finite element analysis (FEA) software is integrated as the calculating tool for analyzing the objective functions and the filter of Pareto solution set based on weight information is introduced to deal with the relationships among all objectives. Grid technology is utilized in PPGA to realize the distributed computations and the user interface is developed to realize the job submission and job management locally/remotely. Taking the aero-elastic tailoring of a composite wing for optimization as an example, a set of Pareto solutions are obtained for the decision-maker. The numerical results show that the aileron reversal problem can be solved by adding the limited skin weight in this system. The algorithm can be used to solve complicated topology optimization for composite structures in engineering and the computation efficiency can be improved greatly by using the grid platform that aggregates numerous idle resources. 相似文献