本文選題：復(fù)合材料　切入點(diǎn)：結(jié)構(gòu)　出處：《華東理工大學(xué)》2017年博士論文

【摘要】：聚合物基復(fù)合材料的結(jié)構(gòu)設(shè)計(jì)和制造技術(shù)是目前關(guān)注的兩大主要方向。本文通過不同的工藝制備了兩種新型的熱塑性復(fù)合材料,并對(duì)他們的結(jié)構(gòu)-性能關(guān)系進(jìn)行研究,以滿足對(duì)汽車復(fù)合材料輕質(zhì)高強(qiáng)的需求。同時(shí)本文將數(shù)值模擬技術(shù)應(yīng)用到熱塑性復(fù)合材料的制造過程,對(duì)雙鋼帶壓機(jī)的傳熱和浸漬兩大工程問題進(jìn)行了研究。本文分別采用預(yù)混粉體浸漬工藝和在線混合工藝制備長(zhǎng)纖維增強(qiáng)熱塑性復(fù)合材料(LFT),并與單向連續(xù)纖維帶(EF)層合,最終得到E-LFT,并研究其多尺度結(jié)構(gòu)對(duì)力學(xué)性能的影響。在宏觀上,EF層對(duì)強(qiáng)度、模量以及韌性的貢獻(xiàn)不同,對(duì)韌性的貢獻(xiàn)最大;在微觀上,纖維長(zhǎng)度的增加有利于E-LFT力學(xué)性能的提高,而分布的纖維長(zhǎng)度優(yōu)于均一的纖維長(zhǎng)度;介觀上,纖維束能夠起到增韌的作用。E-LFT能夠在保證強(qiáng)度和剛度的基礎(chǔ)上,大幅提高韌性,而分層破壞是高韌性的重要原因。然后通過對(duì)比不同的增強(qiáng)體分布形式對(duì)力學(xué)性能的影響,探討層合及分布對(duì)熱塑性復(fù)合材料的意義。層合過程不僅比傳統(tǒng)混雜容易,而且能夠充分體現(xiàn)復(fù)合材料的可設(shè)計(jì)性。本文分別采用薄膜浸漬和混合纖維兩種浸漬工藝制備GMT實(shí)心坯料,經(jīng)過充分膨化和有限壓縮得到LWRT,并研究其多相結(jié)構(gòu)對(duì)力學(xué)性能的影響。其中孔隙率對(duì)LWRT力學(xué)性能的影響很大,它可以通過面密度和厚度進(jìn)行調(diào)控。必須有足夠的纖維長(zhǎng)度才能提供較高的力學(xué)性能。界面對(duì)LWRT的力學(xué)性能影響非常顯著,相容劑的加入不僅提高了纖維和基體的界面剪切強(qiáng)度,而且提高了基體在纖維表面的分散性,這可以通過界面自由能理論解釋。本文對(duì)雙鋼帶壓機(jī)中的傳熱過程進(jìn)行了數(shù)值計(jì)算。采用離散坐標(biāo)(DO)模型模擬紅外加熱管對(duì)鋼帶的預(yù)熱過程,得到鋼帶的升溫曲線,并研究了加熱系統(tǒng)的結(jié)構(gòu)對(duì)輻射傳熱的影響,其中包括紅外加熱管的位置、直徑和數(shù)量、保溫層的厚度、鋼帶和輥筒的接觸熱阻,最終得到優(yōu)化的結(jié)構(gòu)。除了輻射作用,空氣的自然對(duì)流也會(huì)對(duì)鋼帶的預(yù)熱產(chǎn)生影響。物料層中的相變傳熱則是雙鋼帶壓機(jī)中的另一個(gè)重要問題�？紤]相變潛熱的基礎(chǔ)上,模擬物料在雙鋼帶壓機(jī)運(yùn)行過程中的傳熱過程,并得到鋼帶運(yùn)行速度對(duì)預(yù)熱和冷卻過程的影響,最終選擇合適的鋼帶運(yùn)行速度。本文又通過CFD模擬了纖維織物代表體積單元的浸漬過程。結(jié)合有限體積法和VOF方法對(duì)氣-液兩相界面進(jìn)行追蹤,求解多孔介質(zhì)兩相流問題。該方法能夠清晰地捕捉到氣泡的形成和排除,獲得樹脂體積分?jǐn)?shù)隨時(shí)間的變化,從而預(yù)估完成浸漬所需的時(shí)間。本文考察了壓力、粘度以及纖維束孔隙率等參數(shù)對(duì)浸漬速率的影響。
[Abstract]:The structure design and manufacturing technology of polymer matrix composites are two main directions of attention.At the same time, the numerical simulation technology is applied to the manufacturing process of thermoplastic composite material, and the heat transfer and impregnation of double steel strip press are studied.In macroscopically, the contribution of EF layer to strength, modulus and toughness is different, but the increase of fiber length is beneficial to the improvement of mechanical properties of E-LFT, while the distributed fiber length is better than that of homogeneous fiber length.Then the significance of lamination and distribution to thermoplastic composites is discussed by comparing the effect of different reinforcement distribution on mechanical properties.The lamination process is not only easier than the traditional hybrid process, but also can fully reflect the design of composite materials.In this paper, GMT solid billets were prepared by film impregnation and mixed fiber impregnation, and the effects of multiphase structure on mechanical properties were studied.The porosity has a great influence on the mechanical properties of LWRT, which can be controlled by surface density and thickness.Sufficient fiber length is required to provide higher mechanical properties.The influence of interface on the mechanical properties of LWRT is very significant. The addition of compatibilizer not only improves the interfacial shear strength of fiber and matrix, but also improves the dispersion of matrix on the surface of fiber, which can be explained by the theory of interfacial free energy.In this paper, the heat transfer process in double steel strip press is numerically calculated.The preheating process of infrared heating tube to steel strip was simulated by using discrete coordinate DOA model, and the heating curve was obtained. The influence of heating system structure on radiation heat transfer was studied, including the position, diameter and quantity of infrared heating pipe.The thickness of the insulation layer, the contact thermal resistance between the steel strip and the roller is finally optimized.In addition to radiation, the natural convection of air also affects the preheating of the strip.Phase change heat transfer in material layer is another important problem in double steel strip press.Considering the latent heat of phase change, the heat transfer process of the material in the operation of the double strip press is simulated, and the influence of the running speed of the strip on the preheating and cooling process is obtained. Finally, the suitable running speed of the strip is selected.In this paper, the impregnation process of fiber fabric representing volume unit is simulated by CFD.The gas-liquid two-phase interface was traced by the finite volume method and VOF method to solve the two-phase flow problem in porous media.This method can clearly capture the formation and removal of bubbles and obtain the change of resin volume fraction with time, thus predicting the time required to complete the impregnation.The effects of pressure, viscosity and fiber bundle porosity on the impregnation rate were investigated.
【學(xué)位授予單位】：華東理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：TB332

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