本文選題：三維打印 + 仿生復(fù)合材料　； 參考：《中國科學(xué)技術(shù)大學(xué)》2015年碩士論文

【摘要】：在自然界中,許多生物復(fù)合材料都具有精確的微結(jié)構(gòu)和不可思議的力學(xué)性能。貝殼珍珠層正是由于其獨(dú)特的碳酸鈣與有機(jī)質(zhì)交替的多級(jí)“磚——泥”結(jié)構(gòu)以及高強(qiáng)度、高韌性的力學(xué)特性被研究人員廣泛關(guān)注。貝殼珍珠層作為仿生復(fù)合材料的熱點(diǎn)問題,研究其高度有序的微觀結(jié)構(gòu)和增韌機(jī)理對(duì)許多應(yīng)用領(lǐng)域具有指導(dǎo)意義。 與復(fù)合材料領(lǐng)域的貝殼珍珠層研究相似,三維打印也是快速成型領(lǐng)域的熱門技術(shù)。隨著三維打印技術(shù)的快速發(fā)展,研究和開發(fā)人員能夠通過三維打印技術(shù)將靈感方便快捷地變成現(xiàn)實(shí)。本文受天然貝殼珍珠層高強(qiáng)度、高韌性的啟發(fā),利用三維打印技術(shù)制備仿生復(fù)合材料,結(jié)合復(fù)合材料力學(xué)剪切遲滯理論、拉伸試驗(yàn)、有限元分析和粗�；嘧兡M研究復(fù)合材料幾何結(jié)構(gòu)與整體彈性模量、斷裂模式和斷裂韌性的關(guān)系。 我們首先根據(jù)復(fù)合材料細(xì)觀力學(xué)中短纖維復(fù)合材料單元的應(yīng)力傳遞機(jī)制推導(dǎo)了Cox經(jīng)典剪切遲滯理方程。為了符合貝殼珍珠的天然結(jié)構(gòu),在經(jīng)典剪切遲滯理論基礎(chǔ)上,我們又引入了Begley帶有磚塊端部軟膠層粘結(jié)作用的二維貝殼仿生單元模型,該模型能夠用于描述仿生復(fù)合材料單元內(nèi)部的應(yīng)力分布、彈性模量和三種不同的斷裂模式。隨后,我們利用朗道連續(xù)相變自由能理論和Muller的雙穩(wěn)定性理論理解拉伸曲線的水平波動(dòng)階段。 在本文的實(shí)驗(yàn)部分,我們根據(jù)貝殼珍珠層的天然結(jié)構(gòu)制備不同幾何尺寸的“磚——泥”結(jié)構(gòu)復(fù)合材料拉伸試樣和裂紋擴(kuò)展試樣。通過拉伸試驗(yàn),我們詳細(xì)地觀察了拉伸試樣在三個(gè)主要拉伸階段內(nèi)的受力形變形狀態(tài)。通過改變拉伸試樣的幾何參數(shù),我們獲得了拉伸試樣的三種最終破壞模式、拉伸試樣彈性模量、幾何尺寸對(duì)整體力學(xué)特性的影響趨勢、帶預(yù)制裂口拉伸試樣的裂紋擴(kuò)展特性等。 本文的模擬工作主要分為三個(gè)部分,第一部分是利用有限元方法分析周期性的仿貝殼單元的應(yīng)力分布,得到彈性模量與微結(jié)構(gòu)尺寸之間的影響關(guān)系,分析了仿生復(fù)合結(jié)構(gòu)的三種斷裂模式,預(yù)測了磚塊端部軟膠的裂紋形核區(qū)域。第二部分是利用有限元方法進(jìn)行了仿貝殼整體模型的拉伸模擬,得到了仿貝殼結(jié)構(gòu)整體從外到內(nèi)逐漸開裂的破壞機(jī)制。第三部分是采用雙穩(wěn)定性理論建立粗粒化模型,詳細(xì)探討了仿貝殼整體拉伸曲線的水平波動(dòng)機(jī)制。 總之,本文探索了利用立體光固化成型三維打印技術(shù)制備并研究仿生復(fù)合材料的科研模式,研究了仿貝殼復(fù)合材料的料彈性模量、斷裂模式和斷裂韌性,對(duì)于復(fù)合材料的結(jié)構(gòu)設(shè)計(jì)具有借鑒意義。
[Abstract]:In nature, many biological composites have precise microstructures and unimaginable mechanical properties. The shell pearl layer is due to its unique multi-stage "brick - mud" structure alternating with organic matter and high strength. The mechanical properties of high toughness are widely paid attention to by the researchers. The shell pearl layer is a biomimetic composite. The hot issues of materials, studying their highly ordered microstructure and toughening mechanisms are of guiding significance to many applications.
Similar to the study of shell nacre in the field of composite materials, three-dimensional printing is also a hot technology in the field of rapid prototyping. With the rapid development of 3D printing technology, the researchers and developers can turn the inspiration into reality conveniently and quickly through three-dimensional printing technology. This paper is inspired by the high strength and high toughness of natural shell pearls. The bionic composite material was prepared by three-dimensional printing technology. The relationship between the geometrical structure of the composite and the overall elastic modulus, the fracture mode and the fracture toughness was studied with the mechanical shear lag theory, the tensile test, the finite element analysis and the coarse-grained phase transition simulation.
According to the stress transfer mechanism of the short fiber composite element in the micromechanics of composite materials, we derive the classical Cox shear hysteresis equation. In order to conform to the natural structure of shell pearls, we introduce a two-dimensional shell biomimetic sheet with the binding action of Begley with the end of the brick end soft layer on the basis of the classical shear lag theory. The model can be used to describe the stress distribution, modulus of elasticity and three different fracture modes in the bionic composite element. Then, we use Landau's theory of continuous phase transition free energy and the double stability theory of Muller to understand the stage of the horizontal fluctuation of the tensile curve.
In the experimental part of this article, we prepare the tensile specimens and crack propagation specimens of "brick mud" composite materials with different geometric sizes based on the natural structure of the shell nacre. Through the tensile test, we observe the deformation state of the tensile specimen in three main stretching stages in detail. By changing the tensile specimen, the tensile specimen is changed. The three ultimate failure modes of the tensile specimen, the elastic modulus of the tensile specimen, the influence trend of the geometric size to the overall mechanical properties, and the crack propagation characteristics of the prefabricated crack tensile specimens are obtained.
The simulation work of this paper is divided into three parts. In the first part, the finite element method is used to analyze the stress distribution of the periodic shell element, and the relationship between the elastic modulus and the microstructural size is obtained. Three kinds of fracture modes of the bionic composite structure are analyzed, and the crack nucleation area of the soft rubber at the end of the brick is predicted. Second parts are predicted. The finite element method is used to simulate the tensile model of the shell integral model, and the failure mechanism of the shell structure to crack gradually from outside to inside is obtained. The third part is a coarse grain model based on the double stability theory, and the water flat wave mechanism of the whole drawing curve of the shell is discussed in detail.
In conclusion, this paper explored the research mode of preparing and studying the biomimetic composite materials by three-dimensional printing technology, and studied the modulus of elasticity, fracture mode and fracture toughness of the shell composite material, which is of reference to the structure design of the composite.
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TB391

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