復(fù)合材料RTM工藝充模過程數(shù)值仿真與缺陷預(yù)測研究
本文選題:復(fù)合材料 + RTM工藝; 參考:《哈爾濱工業(yè)大學(xué)》2015年博士論文
【摘要】:樹脂轉(zhuǎn)移模塑(Resin Transfer Molding,RTM)已經(jīng)發(fā)展成為纖維增強(qiáng)樹脂基復(fù)合材料的主導(dǎo)工藝技術(shù)之一,該工藝的成型質(zhì)量很大程度上取決于充模階段樹脂對預(yù)成型體的浸潤程度。為解決目前RTM模具和充模工藝參數(shù)的設(shè)計需要進(jìn)行大量試驗(yàn)而帶來的高成本、低效率以及質(zhì)量難以保證的問題,本文在分析國內(nèi)外有關(guān)RTM工藝數(shù)字化技術(shù)及相關(guān)領(lǐng)域研究成果的基礎(chǔ)上,對影響RTM工藝的預(yù)成型體幾何結(jié)構(gòu)、滲透率、充摸過程和缺陷形成進(jìn)行了深入研究,并針對計算機(jī)輔助工藝過程分析的實(shí)際需要,將本文的研究成果應(yīng)用于開發(fā)的RTMSimu系統(tǒng)中。預(yù)成型體的幾何結(jié)構(gòu)是影響RTM工藝參數(shù)的主要因素,建立預(yù)成型體幾何模型是進(jìn)行工藝仿真和成型缺陷預(yù)測的基礎(chǔ)。本文在詳細(xì)分析RTM織物預(yù)成型體多尺度結(jié)構(gòu)特性的基礎(chǔ)上,建立了三個尺度下的幾何模型。在微觀尺度,基于Monte Carlo隨機(jī)運(yùn)動法獲得了纖維束前后兩個截面不同的單絲分布,通過拉伸操作建立了纖維束初步模型,采用Bezier曲線理論對單絲中心線進(jìn)行校正后,建立了同時包含軸向和徑向隨機(jī)性的微觀纖維束模型。在細(xì)觀尺度,分析了單胞內(nèi)紗線的截面及彎曲狀態(tài),采用最小勢能原理求解了單胞的幾何參數(shù),分析了單胞剪切和壓縮變形過程,建立了預(yù)成型體單胞不同變形狀態(tài)的幾何模型。在宏觀尺度,提出了基于幾何信息的鋪覆仿真算法,基于曲面切向量、法曲率等幾何信息進(jìn)行織物節(jié)點(diǎn)位置的求解,建立了二維織物在復(fù)雜曲面上的鋪覆模型。預(yù)成型體滲透率是RTM充模過程仿真的關(guān)鍵參數(shù),表達(dá)樹脂在預(yù)成型體內(nèi)流動的難易程度。本文以上述預(yù)成型體多尺度幾何模型為基礎(chǔ),研究了微觀纖維束和細(xì)觀單胞的滲透率仿真預(yù)報方法。通過對纖維單絲間樹脂流動進(jìn)行仿真,預(yù)報了纖維束滲透率,結(jié)果表明,單絲的隨機(jī)性分布對微觀滲透率有一定的影響。建立了單胞內(nèi)樹脂雙尺度流動的數(shù)學(xué)模型,研究了紗線卷曲和相互擠壓對微觀滲透率分布的影響,基于有限差分法建立了樹脂流動控制方程的數(shù)值求解方法,求得了單胞內(nèi)樹脂流動壓強(qiáng)和速度場,進(jìn)而獲得了單胞滲透率預(yù)測值。在正交單胞滲透率預(yù)測方法的基礎(chǔ)上,采用貼體坐標(biāo)法完成了剪切變形后流動控制方程從物理域到計算域的轉(zhuǎn)換,實(shí)現(xiàn)了剪切單胞滲透率的預(yù)報。研究了單胞滲透率隨剪切和壓縮變形的變化規(guī)律。通過與文獻(xiàn)預(yù)測數(shù)據(jù)和實(shí)驗(yàn)值對比,證明了本文預(yù)測模型和求解方法的正確性。針對樹脂空氣兩相流難以直接求解的問題,研究了基于VOF(Volume of Fluid)多相流技術(shù)的RTM工藝充模過程仿真算法。通過在Navier-Stokes方程中增加流固阻力項的方式建立了RTM充模過程樹脂流動的數(shù)學(xué)模型,基于VOF技術(shù)實(shí)現(xiàn)了上述模型的數(shù)值求解,算例表明上述算法具有較高的精度。針對帶有預(yù)成型體變形的RTM工藝,為了避免對樹脂流動/預(yù)成型體變形耦合方程的直接求解,建立了基于動態(tài)網(wǎng)格模型和主從單元法的充模過程全三維仿真算法,實(shí)現(xiàn)了基于黏彈性模型的預(yù)成型體變形計算,提高了仿真精度。算例表明上述算法能夠?qū)崿F(xiàn)充模過程中流場區(qū)域的動態(tài)更新和順序注射策略的仿真。對RTM成型缺陷進(jìn)行預(yù)測是充模過程仿真的一個重要任務(wù)。干斑是RTM工藝的主要缺陷之一,本文對干斑的形成以及演變過程進(jìn)行了分析,基于VOF方法仿真了干斑的形成過程。研究了充模過程中的氣泡產(chǎn)生機(jī)理,建立了氣泡預(yù)測模型,該模型通過對比紗線內(nèi)外的樹脂流動速度來判斷空氣裹入的位置及其尺寸。重點(diǎn)分析了樹脂流動方向和織物剪切變形對單胞浸潤的影響,研究了氣泡位置和尺寸隨流動方向和剪切角的變化規(guī)律。通過實(shí)驗(yàn)驗(yàn)證了上述模型的正確性;诒疚牡难芯砍晒,開發(fā)了RTM充模過程數(shù)值仿真系統(tǒng)(RTMSimu)。在數(shù)據(jù)庫系統(tǒng)的基礎(chǔ)上利用面向?qū)ο缶幊陶Z言完成了原型系統(tǒng)的開發(fā),實(shí)現(xiàn)了RTM工藝預(yù)成型體幾何建模、滲透率預(yù)測、充模過程仿真以及充模缺陷預(yù)測等功能的參數(shù)化驅(qū)動和各模塊的集成。通過某型號汽車引擎蓋的建模與仿真過程為例,展示了RTMSimu系統(tǒng)的主要界面和操作流程,并綜合分析了系統(tǒng)的技術(shù)指標(biāo),初步驗(yàn)證了上述系統(tǒng)的可行性。
[Abstract]:Resin Transfer Molding (RTM) has developed into one of the leading technology of fiber reinforced resin matrix composites. The molding quality of the process depends largely on the infiltration degree of the resin to the preformed body during the mold filling stage. A large number of tests are needed to solve the current design of the RTM mold and mold filling process parameters. The problem of high cost, low efficiency and inability to guarantee the quality is difficult. On the basis of analyzing the domestic and foreign research achievements in the digital technology of RTM technology and related fields, this paper deeply studies the geometry structure, permeability, filling process and defect formation of the preformed body which affects the RTM process, and aims at the computer aided process. The actual needs of the process analysis are applied to the developed RTMSimu system. The geometric structure of the preformed body is the main factor affecting the parameters of the RTM process. The establishment of the preformed geometric model is the basis for the process simulation and the prediction of the forming defects. In this paper, the multi-scale structure characteristics of the RTM fabric preform are analyzed in detail. On the basis of this, a geometric model under three scales is established. On the microscale, the distribution of monofilament in two sections of the fiber bundle before and after the fiber bundle is obtained on the basis of the Monte Carlo random motion method. The initial model of the fiber bundle is established through the stretching operation. The axial and diameter of the single filament is established by using the theory of Bezier curve to correct the single wire center line. On the microscale, the cross section and bending state of the single cell yarn are analyzed on the meso scale. The geometric parameters of the single cell are solved by the principle of minimum potential energy. The process of the single cell shear and compression deformation is analyzed, and the geometric model of the different deformation state of the preformed single cell is established. The geometry based on the macroscopic scale is based on the geometry. The embedding simulation algorithm of information is based on the geometric information such as curved surface tangent vector, normal curvature and other geometric information to solve the location of fabric nodes. The overlay model of two-dimensional fabric on complex surfaces is established. The permeability of the preformed body is the key parameter of the simulation of RTM filling process, and the difficulty of the flow of the resin in the preformed body is expressed. On the basis of the multi-scale geometric model of the body, the permeability simulation prediction method of the micro fiber bundle and the meso cell is studied. The fiber beam permeability is predicted by the simulation of the flow of the fiber monofilament resin. The results show that the random distribution of the monofilament has a definite effect on the microscopic permeability. The double scale flow of the single cell resin is established. In the mathematical model, the effect of the yarn crimp and mutual extrusion on the micropermeability distribution is studied. Based on the finite difference method, the numerical solution of the flow control equation of the resin is established. The flow pressure and velocity field of the resin in the single cell are obtained. Then the prediction value of the single cell permeability is obtained. On the basis of the orthogonal cell permeability prediction method, the method of predicting the permeability of the single cell is obtained. The transfer of the flow control equation from the physical domain to the computational domain after the shear deformation is completed by the body fitted coordinate method, and the prediction of the shear single cell permeability is realized. The variation of the single cell permeability with the shear and compression deformation is studied. The accuracy of the prediction model and the solution method is proved by comparison with the predicted data and the experimental data. In view of the problem that the resin air two phase flow is difficult to be solved directly, the simulation algorithm of the mold filling process of the RTM process based on the VOF (Volume of Fluid) multiphase flow technology is studied. The mathematical model of the resin flow in the RTM filling process is established by adding the fluid solid resistance term in the Navier-Stokes equation, and the above model is realized based on the VOF technology. Numerical calculation shows that the above algorithm has high accuracy. In order to avoid direct solution to the deformation coupling equation of resin flow / preformed body, a full three dimension simulation algorithm based on dynamic mesh model and master slave unit method is established for the RTM process with preformed body deformation, and the viscoelastic model is realized. The calculation of the deformation of the preformed body improves the simulation accuracy. The calculation example shows that the algorithm can realize the dynamic updating of the flow field and the simulation of the sequential injection strategy during the filling process. It is an important task for the simulation of the mold filling process to predict the defects of the RTM molding. The dry spot is one of the main defects of the RTM process. The evolution process is analyzed. The formation process of the dry spot is simulated based on the VOF method. The bubble generation mechanism in the mold filling process is studied. The bubble prediction model is established. The model determines the position and size of the air wrapped by comparing the flow velocity of the resin inside and outside the yarn. The direction of the resin flow and the shear deformation of the fabric are analyzed. For the influence of the single cell infiltration, the change of the position and size of the bubble with the flow direction and the shear angle is studied. The correctness of the model is verified by the experiment. Based on the research results of this paper, the numerical simulation system of the RTM filling process (RTMSimu) is developed. The prototype is built on the base of the database system and the prototype is used to complete the prototype. With the development of the system, the parameterized driving of the functions of the RTM preform, the permeability prediction, the simulation of the mold filling process and the prediction of the mold filling defect, and the integration of each module are realized. The main interface and operation process of the RTMSimu system are demonstrated by an example of the modeling and Simulation of a type of automobile engine hood, and the comprehensive analysis is made. The technical indicators of the system preliminarily verify the feasibility of the above system.
【學(xué)位授予單位】:哈爾濱工業(yè)大學(xué)
【學(xué)位級別】:博士
【學(xué)位授予年份】:2015
【分類號】:TB33
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