清华大学综合论文训练题目:双稳态复合材料设计及力学行为研究系别:航天航空学院专业:工程力学系姓名:雷一鸣指导教师:姚学峰副教授2007年6月22日I中文摘要近年来双稳态复合材料(Bistablecomposite)的薄壳结构引起了人们的重视,双稳态复合材料由于能够用来制作简单、可靠、轻质的可展开机构(DeployableStructures)而广泛的应用于航天飞行器的设计和制造中,因此对双稳态复合材料的折叠行为和稳态构型的研究具有重要的学术意义和工程背景。本文建立了理论模型来研究双稳态结构折叠与展开过程中的力学变形理论机制,提出了双稳态结构的控制方程,并采用数值法求解方程;发现了具有双稳态性质的复合材料结构,其初始横截面圆心角存在最小临界值;讨论了解的稳定性,给出了两种稳态结构之间的简明关系。同时还制备了碳纤维/玻璃纤维增强的环氧树脂复合材料薄壳结构,并对其折叠行为开展了相关的实验研究。发现了±45°方向铺层的结构在弯曲性能上优于0/90°铺层结构。提出了新的实验方法和数据处理方式得到了双稳态结构弯曲时的弯矩和半径变化情况,实验结果与理论模型吻合的很好。关键词:双稳态;复合材料;可展开机构;薄壳结构IIIABSTRACTThinshellstructuresmadefrombistablecompositematerialarebeingdevelopedinrecentyears.Thereisagrowingtrendintheaerospaceindustrytowardsimpler,lighterandmorereliabledeployablestructures.Thereforethestudiesonthebendingbehaviorofbistablecompositestructuresandtheirstableformsareoffarreachingimportance.Inthisdissertation,atheoreticalmodelisintroducedtostudythebendingprocessofbistablecompositestructures.Anequationisfoundtodescribethestableformofbistablestructures.Thismodelalsoshowsacriticalminimumvalueforinitialcrosssectionangletoexhibitbistability,anditgivesabriefrelationshipbetweentwostableforms.Carbon/glassfibrerefinedepoxyresincompositesarealsomadetodesignbistablestructuresforthefollowingtests.Bendingtestsshowthatstructureswith±45°layuphavebetterperformancethanthosewith0/90°layup.Anewexperimentmethodispresentedtoobtainthetorqueandradiuschangesinthebendingprocess.Theexperimentalresultsfitthetheoreticalmodelwell.Keywords:Bistable;Composite;Deployablestructures;ThinshellstructuresV目录第1章引言........................................................................................................11.1双稳态结构简介............................................................................................................11.2双稳态结构研究状况....................................................................................................21.2.1理论研究进展..........................................................................................................21.2.2实验研究进展..........................................................................................................31.3本文研究的主要内容....................................................................................................31.3.1研究内容..................................................................................................................31.3.2各章内容简介..........................................................................................................4第2章复合材料薄壳结构的双稳态性质研究................................................52.1理论模型及推导............................................................................................................52.1.1模型建立及几何尺寸...............................................................................................52.1.2应变分量..................................................................................................................62.1.3本构关系..................................................................................................................82.1.4径向和横向弯矩....................................................................................................102.1.5平衡方程................................................................................................................102.2双稳态解......................................................................................................................112.2.1材料常数................................................................................................................112.2.2数值解....................................................................................................................132.3本章小结......................................................................................................................16第3章双稳态复合材料薄壳结构的制备......................................................193.1材料及模具..................................................................................................................193.1.1材料体系................................................................................................................193.1.2脱模剂....................................................................................................................213.1.3模具........................................................................................................................213.2制备工艺......................................................................................................................22VI3.2.1铺层方式................................................................................................................223.2.2固化条件................................................................................................................223.3材料常数.....................................................................................................................233.4本章小结.....................................................................................................................26第4章双稳态行为的实验研究...........................................................