本文選題：生物復(fù)合材料 + 納米結(jié)構(gòu)��； 參考：《北京理工大學(xué)》2015年碩士論文

【摘要】：骨骼、牙齒和貝殼等生物材料是多級(jí)納米復(fù)合材料，具有優(yōu)異的力學(xué)性能。在納米尺度上礦物質(zhì)晶體錯(cuò)列鑲嵌在柔軟的蛋白質(zhì)基質(zhì)中，礦物質(zhì)晶體具有很大的長(zhǎng)細(xì)比。本文第一部分通過(guò)基于梁-彈簧模型的有限元研究大尺寸交錯(cuò)結(jié)構(gòu)的屈曲行為。用Euler梁模擬礦物質(zhì)晶體，并用一系列分布彈簧去等效蛋白質(zhì)基質(zhì)，考慮間斷交錯(cuò)模型、鉸接交錯(cuò)模型和連續(xù)梁模型三種情況。當(dāng)長(zhǎng)細(xì)比較短時(shí)，間斷模型中礦物質(zhì)梁端部自由，更容易失穩(wěn)，主要發(fā)生類似剛體旋轉(zhuǎn)的形式，幾乎沒有彎曲，蛋白質(zhì)部分既有剪切又有側(cè)向拉壓變形，模型呈現(xiàn)周期的局部屈曲模式；鉸接模型中礦物質(zhì)梁在鉸接約束作用下，抗屈曲能力較強(qiáng)，不易傳遞屈曲波形，在加載邊界附近區(qū)域呈局部屈曲模式。長(zhǎng)細(xì)比增大后，礦物質(zhì)容易彎曲但不易整體轉(zhuǎn)動(dòng)，兩種交錯(cuò)模型的屈曲模態(tài)變得一致并接近連續(xù)模型的剪切屈曲模式，，臨界載荷結(jié)果驗(yàn)證了我們模態(tài)的分析結(jié)果，并且得出增大礦物質(zhì)長(zhǎng)細(xì)比可提高生物材料的屈曲強(qiáng)度的結(jié)論。第二部分研究基于鉸接模型的生物材料的屈曲問(wèn)題，討論了礦物質(zhì)晶體對(duì)齊排布和交錯(cuò)排布兩種情況。發(fā)現(xiàn)礦物質(zhì)晶體對(duì)齊排布時(shí)，屈曲強(qiáng)度最低；而對(duì)稱交錯(cuò)排布時(shí)，屈曲強(qiáng)度最高；增大礦物質(zhì)的長(zhǎng)細(xì)比或體積分?jǐn)?shù)均能提高屈曲強(qiáng)度，并趨于連續(xù)礦物質(zhì)模型的屈曲強(qiáng)度。由此得出，不論是間斷模型還是鉸接模型，通過(guò)交錯(cuò)排布同時(shí)增加礦物質(zhì)長(zhǎng)細(xì)比，可提高材料的抗屈曲能力并接近完美連續(xù)結(jié)構(gòu)，這對(duì)結(jié)構(gòu)穩(wěn)定性起到至關(guān)重要的作用。第三部分討論含有裂紋的交錯(cuò)結(jié)構(gòu)的斷裂行為，當(dāng)?shù)V物質(zhì)增強(qiáng)相排布方向與裂紋平行時(shí)，增強(qiáng)相對(duì)裂紋尖端的應(yīng)力集中現(xiàn)象不起作用，二者垂直時(shí)，能明顯降低裂紋尖端的應(yīng)力強(qiáng)度因子；同時(shí)，越接近對(duì)稱交錯(cuò)模式、礦物質(zhì)體積分?jǐn)?shù)越高，長(zhǎng)細(xì)比越大，裂紋尖端的應(yīng)力強(qiáng)度因子越低。
[Abstract]:Biomaterials such as bone, teeth and shells are multistage nanocomposites with excellent mechanical properties. The mineral crystals are mislaid in soft protein matrix on nanometer scale, and the mineral crystals have a large aspect ratio. In the first part of this paper, the buckling behavior of large scale staggered structures is studied by finite element method based on beam-spring model. The mineral crystals are simulated by Euler beam, and a series of distributed springs are used to degrade the equivalent protein matrix. Three kinds of cases are considered: the interlaced interleaving model, the hinged interlaced model and the continuous beam model. When the length is relatively short, the end of the mineral beam is free in the discontinuous model, and it is more prone to instability. It mainly occurs in the form of rigid body rotation, almost no bending, and the protein part has both shear and lateral tension and compression deformation. The model presents periodic local buckling mode, and the mineral beam in the hinge model has strong buckling resistance and is not easy to transmit buckling waveform under hinged constraint, and the local buckling mode is found in the region near the loading boundary. When the slenderness ratio increases, the mineral is easy to bend but not to rotate as a whole. The buckling modes of the two staggered models become consistent and close to the shear buckling mode of the continuous model. The critical load results verify the results of our modal analysis. It is concluded that increasing the aspect ratio of minerals can improve the buckling strength of biomaterials. In the second part, the buckling problem of biomaterials based on hinged model is studied, and the alignment and staggered arrangement of mineral crystals are discussed. It is found that the buckling strength is the lowest when the mineral crystals are aligned and the highest when the symmetry is staggered, and the buckling strength can be increased by increasing the aspect ratio or volume fraction of the mineral, and tends to the buckling strength of the continuous mineral model. It is concluded that both the discontinuous model and the hinged model can improve the buckling resistance of the material and approach the perfect continuous structure by staggered arrangement and increase the ratio of mineral slenderness at the same time, which plays an important role in the stability of the structure. In the third part, the fracture behavior of staggered structures with cracks is discussed. When the arrangement direction of the mineral reinforcement phase is parallel to the crack, the stress concentration phenomenon of the enhanced phase relative to the crack tip does not work. When the two phases are perpendicular to each other, The stress intensity factor at the crack tip can be obviously reduced, and the higher the mineral volume fraction and the greater the aspect ratio, the lower the stress intensity factor at the crack tip.
【學(xué)位授予單位】：北京理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TB33;O341

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 唐致遠(yuǎn),耿新,王占良,薛建軍;摻Fe~(3+)MnO_2超級(jí)電容器電極材料的制備[J];應(yīng)用化學(xué);2002年10期

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