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  本文選題：復(fù)合材料層合板 + 層間斷裂　； 參考：《西北工業(yè)大學(xué)》2015年博士論文

【摘要】：當(dāng)前復(fù)合材料在航空航天等工程結(jié)構(gòu)中的使用率正處于快速增長階段。與各向同性材料相比,復(fù)合材料具有構(gòu)造復(fù)雜和損傷形式多樣等特點,其失效模式之間相互作用,互為誘因。這種材料構(gòu)成和損傷組合的復(fù)雜特性給復(fù)合材料的強度分析帶來很大挑戰(zhàn)。深入理解復(fù)合材料失效破壞機理,建立反映客觀物理現(xiàn)象的強度分析方法對復(fù)合材料結(jié)構(gòu)設(shè)計和使用維護十分必要,有助于降低結(jié)構(gòu)試驗測試成本,縮短研制周期,提高結(jié)構(gòu)使用效率和安全性。本文以工程應(yīng)用最為廣泛的纖維增強復(fù)合材料層合板為研究對象,在層合板層間界面斷裂、面內(nèi)破壞強度理論和非線性本構(gòu)關(guān)系等方面開展研究工作。論文首先研究了層合板層間斷裂分析問題。針對層間界面斷裂模擬時計算效率低、計算成本高等問題,提出一種適合與板殼單元配合使用,且能夠考慮板殼平動和轉(zhuǎn)動自由度以及板殼厚度的新型組合界面單元,并建立相應(yīng)的三維板殼分層模型。推導(dǎo)了新型組合界面單元的有限元列式,給出雙線性形式下單一型和混合型分層的本構(gòu)關(guān)系,推導(dǎo)出組合界面單元的切線剛度矩陣,并在ABAQUS隱式用戶自定義單元子程序UEL中予以實現(xiàn)。將組合界面單元用于模擬單一型和混合型分層問題。通過雙懸臂梁(DCB)試驗的模擬,重點考察了數(shù)值模擬中幾種參數(shù)的選取及其對計算結(jié)果的影響。對末端缺口三點彎曲試驗(3ENF)、混合模式彎曲試驗(MMB)和單搭接膠接接頭試驗進行了數(shù)值模擬,并推導(dǎo)了解析計算公式,計算結(jié)果與有關(guān)文獻中的試驗結(jié)果及解析計算結(jié)果相吻合,表明組合界面單元能很好的模擬單一型和混合型分層損傷的起始和演化。其次研究了層合板的面內(nèi)強度分析問題。建立了完整的基于復(fù)合材料層合板失效機制的強度理論。首先論述了復(fù)合材料就地效應(yīng)及其重要性,推導(dǎo)了一種基于斷裂力學(xué)假設(shè)的層合板就地強度計算方法。以有關(guān)文獻中纖維壓縮破壞機理的試驗觀察為基礎(chǔ),提出一種改進的纖維壓縮失效預(yù)測模型,在保持LaRC系列強度理論中kink model基本特征的前提下對其進行改進,并增加一個強度準(zhǔn)則來描述剪切驅(qū)動型纖維壓縮破壞模式,使改進模型具有更好的適應(yīng)性。針對樹脂基體在橫向壓縮和面內(nèi)剪切加載下的非線性力學(xué)行為,提出一種利用等效應(yīng)變來考慮二者之間非線性疊加耦合效應(yīng)的方法,并由此得到非線性本構(gòu)關(guān)系。利用建立的強度理論和失效模式預(yù)測方法,對多種單向板和層合板在簡單和復(fù)雜應(yīng)力狀態(tài)下的失效包線和應(yīng)力應(yīng)變曲線進行了理論預(yù)測,并討論了關(guān)鍵參數(shù)選取的影響。結(jié)果表明,本文提出的強度理論全方位表現(xiàn)出較好的預(yù)測精度和適應(yīng)性,能反映真實的試驗現(xiàn)象和趨勢。采用連續(xù)介質(zhì)損傷力學(xué)(CDM)思想,建立一種基于失效機理的非線性損傷本構(gòu)關(guān)系。結(jié)合層合板連續(xù)殼模型的特點,根據(jù)強度理論預(yù)測的不同失效模式特征提出對應(yīng)的損傷退化方法,并針對許多細節(jié)問題給出詳細的因應(yīng)對策,在商業(yè)有限元軟件ABAQUS的顯式用戶材料子程序VUMAT中予以程序?qū)崿F(xiàn)。為了驗證方法的可靠性,首先通過一個受載立方體的模擬進行了網(wǎng)格敏感性測試分析,然后通過模擬單向板偏軸壓縮試驗來驗證非線性本構(gòu)關(guān)系的合理性,再通過模擬文獻中多種層合板的開孔壓縮、開孔拉伸和增高型緊湊拉伸試驗來表現(xiàn)方法的分析精度,分析各自的失效破壞過程和特征。數(shù)值模擬結(jié)果表明,本文方法具有較好的預(yù)測精度,能反映結(jié)構(gòu)的真實力學(xué)行為和破壞形態(tài)。
[Abstract]:Compared with isotropic materials, composite materials have the characteristics of complex structure and various types of damage compared with isotropic materials, and their failure modes interact and cause mutual inducement. The complex properties of this material and damage combination give the strength of the composite material. The analysis brings great challenges. It is necessary to understand the failure mechanism of composite materials and to establish the strength analysis method to reflect the objective physical phenomena, which is very necessary for the design and maintenance of composite materials. It is helpful to reduce the cost of test and test, shorten the development cycle and improve the efficiency and safety of the structure. A wide range of fiber reinforced composite laminates are used as the research object, the interlaminar interface fracture, the theory of in-plane failure strength and the nonlinear constitutive relation are carried out. Firstly, the problem of interlaminar fracture analysis is studied. The problem of low calculation efficiency and high calculation cost is proposed for interlaminar interface fracture simulation. A new type of composite interface unit suitable to the plate and shell elements which can be used in combination with the plate and shell translational and rotational degrees of freedom and the thickness of the plate and shell is taken into account, and a corresponding three-dimension plate and shell stratification model is established. The finite element formula of the new type of composite interface unit is derived, and the constitutive relation of the bilinear form and the mixed type is given. The tangent stiffness matrix of the composite interface unit is derived and implemented in the ABAQUS implicit user custom element subprogram UEL. The combined interface unit is used to simulate the single and mixed stratification problems. The selection of several parameters in the numerical simulation and the shadow of the calculation results are emphatically investigated by the simulation of the double cantilever beam (DCB) test. The three point bending test (3ENF), the mixed mode bending test (MMB) and the single lap joint joint test were numerically simulated, and the analytical formula was deduced. The results were in agreement with the experimental results and the analytical results in the relevant literature. It showed that the combined interface unit could well simulate the single and mixed type. The beginning and evolution of layer damage. Secondly, the internal strength analysis of laminates is studied. A complete strength theory based on the failure mechanism of composite laminates is established. First, the local effect and its importance of composite materials are discussed. A calculation method for the in-situ strength of laminates based on the hypothesis of fracture mechanics is derived. Based on the experimental observation of the failure mechanism of the medium fiber compression, an improved prediction model for the failure of fiber compression is proposed. It is improved on the premise of maintaining the basic characteristics of kink model in the LaRC series strength theory, and a strength criterion is added to describe the compression failure mode of the shear driven fiber, which makes the improved model better. Adaptability. In view of the nonlinear mechanical behavior of the resin matrix under transverse compression and in-plane shear loading, a method of using equal effect to consider the nonlinear superposition coupling effect between the two is proposed, and the nonlinear constitutive relation is obtained. The theoretical prediction of the failure package line and stress strain curve in simple and complex stress state is made, and the influence of the key parameters is discussed. The results show that the strength theory presented in this paper has good prediction accuracy and adaptability, and can reflect the true test phenomenon and trend. The continuous medium damage mechanics (CD M) thought, establish a nonlinear damage constitutive relation based on failure mechanism. Combining the characteristics of the laminates continuous shell model, the corresponding damage degradation method is proposed according to the different failure mode characteristics predicted by the strength theory, and the detailed response strategies are given for many details, and the explicit user material of the commercial finite element software ABAQUS is given. In order to verify the reliability of the material program VUMAT, in order to verify the reliability of the method, the grid sensitivity test is carried out by the simulation of a loaded cube, and then the rationality of the nonlinear constitutive relation is verified by simulating the uniaxial compression test of one way plate, and then the opening of a variety of laminates in the simulated document is compressed and opened. Tensile and elevated compact tensile tests are used to demonstrate the analytical accuracy of the methods and to analyze their failure processes and characteristics. The numerical simulation results show that the proposed method has good prediction accuracy and can reflect the real mechanical behavior and failure mode of the structure.

【學(xué)位授予單位】：西北工業(yè)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TB33;O346

【參考文獻】

相關(guān)期刊論文 前1條

1 林智育;許希武;;復(fù)合材料層板低速沖擊后剩余壓縮強度[J];復(fù)合材料學(xué)報;2008年01期

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本文編號：1847607