【摘要】：形狀記憶聚合物較形狀記憶金屬和形狀記憶陶瓷具有許多突出優(yōu)點,例如密度低、形狀凍結(jié)率高、易制備、轉(zhuǎn)變溫度可調(diào)等,可降解特性更是令其在生物醫(yī)療領(lǐng)域具有廣闊的應(yīng)用前景。但形狀記憶聚合物材料的固有缺陷也限制了其發(fā)展,如實驗研究不系統(tǒng)等。軟物質(zhì)科學(xué)近年來得到迅速發(fā)展,其中基于膜/基結(jié)構(gòu)表面失穩(wěn)自組裝實現(xiàn)復(fù)雜微結(jié)構(gòu)生成,在平面制圖技術(shù)、功能表面制備、柔性電子器件等領(lǐng)域均具有重要應(yīng)用前景,近年來得到廣泛關(guān)注。但目前所研究報道的膜/基結(jié)構(gòu)失穩(wěn)基本都是單向不可逆的,無法實現(xiàn)雙向形狀改變。結(jié)合兩個領(lǐng)域各自的特點和遇到的問題,為此本文提出了一種雙向表面形貌力學(xué)自組裝功能實現(xiàn)方法,并開展相應(yīng)的熱力學(xué)實驗和特征參數(shù)表征及形貌調(diào)控。 利用高臨界轉(zhuǎn)變溫度的SMP膜和低臨界轉(zhuǎn)變溫度的SMP基體原位復(fù)合,并凍結(jié)初始軸向壓縮變形,在隨后的形狀恢復(fù)過程中膜/基體系發(fā)生從光滑結(jié)構(gòu)到表面失穩(wěn),再恢復(fù)光滑結(jié)構(gòu)的雙向可逆形狀記憶效應(yīng)。從本質(zhì)上說,膜/基體失穩(wěn)是由于結(jié)構(gòu)受到外界某種刺激(如溫度場、電場、生物組織生長等),其表面膜和下面軟基體由于變形不匹配而造成膜受壓屈曲,其后進一步刺激使變形不匹配產(chǎn)生的殘余應(yīng)力得到釋放從而得到變形恢復(fù)。 本文首先介紹了穩(wěn)定性問題的基本概念,以最基本的圓柱模型為例,推導(dǎo)了膜／基結(jié)構(gòu)的失穩(wěn)特征的理論框架,分析了幾何和材料參數(shù)對屈曲特征參數(shù)(如極限屈曲模數(shù)、臨界薄膜厚度)的影響。隨后進行了以SMP膜/基復(fù)合管結(jié)構(gòu)材料制備、熱力學(xué)實驗和變形場實時檢測為主,經(jīng)過多種加載方式的實驗研究,確定了以加入圓柱芯作為內(nèi)部支撐的加載方式。經(jīng)過多種荷載下的屈曲效果對比,確定出較為理想的荷載數(shù)值,獲得了較好的膜/基結(jié)構(gòu)屈曲效果并實現(xiàn)了完整的雙程自組裝制備過程。有限元模擬部分在現(xiàn)有邊界條件基礎(chǔ)上做出一定的簡化,將有限元模擬與理論解的結(jié)果進行對比,定性的分析了各種幾何和材料參數(shù)對屈曲形態(tài)的影響,為深入進行膜／基復(fù)合管結(jié)構(gòu)屈曲行為的定量化控制提供了重要依據(jù)。 上述研究結(jié)果揭示出SMP膜／基復(fù)合管結(jié)構(gòu)的雙程自組裝是可行的,也是可控制的。
[Abstract]:Shape memory polymers have many outstanding advantages over shape memory metals and shape memory ceramics, such as low density, high shape freezing rate, easy preparation, adjustable transition temperature, etc. The biodegradable property makes it have a broad application prospect in biomedical field. However, the inherent defects of shape memory polymer materials also limit their development, for example, the experimental study is not systematic. The science of soft matter has been developed rapidly in recent years, in which complex microstructure can be generated based on surface instability self-assembly of membrane / base structure. It has important application prospects in plane mapping, functional surface fabrication, flexible electronic devices and so on. In recent years, wide attention has been paid. However, the instability of membrane / substrate structure reported at present is basically unidirectional irreversible and can not realize bidirectional shape change. According to the characteristics of the two fields and the problems encountered, this paper proposes a method to realize the self-assembly function of bidirectional surface morphology mechanics, and carries out corresponding thermodynamic experiments, characterization of characteristic parameters and morphology regulation. The SMP film with high critical transition temperature and SMP substrate with low critical transition temperature are in situ composite, and the initial axial compression deformation is frozen. During the subsequent shape recovery process, the film / base system is unstable from smooth structure to surface. The two-way reversible shape memory effect of smooth structure is restored. Essentially, the instability of the film / matrix is due to a certain external stimulus (such as temperature field, electric field, biological tissue growth, etc.), and the film buckles under pressure due to the mismatch between the surface film and the underlying soft substrate. After further stimulation, the residual stress caused by deformation mismatch is released and the deformation recovery is obtained. In this paper, the basic concept of stability problem is first introduced. Taking the most basic cylindrical model as an example, the theoretical framework of instability characteristics of membrane / base structures is derived, and the effects of geometry and material parameters on buckling characteristic parameters, such as ultimate buckling modulus, are analyzed. Critical film thickness). Then, the SMP membrane / base composite pipe structure material was prepared, thermodynamics experiment and deformation field real time detection were mainly carried out. Through the experimental study of various loading modes, the loading mode with cylindrical core as internal support was determined. Through the comparison of buckling effects under various loads, the ideal load values are determined, and a better buckling effect of membrane / base structure is obtained, and a complete two-way self-assembly process is realized. Based on the existing boundary conditions, the finite element simulation is simplified, the results of finite element simulation and theoretical solution are compared, and the influence of various geometry and material parameters on buckling shape is analyzed qualitatively. It provides an important basis for the quantitative control of the buckling behavior of membrane / base composite pipe structures. The results show that the two-way self-assembly of SMP membrane / base composite tube is feasible and controllable.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TB381

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本文編號：2219865