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  本文選題：碳粘結(jié)碳纖維復(fù)合材料 + 纖維取向�。� 參考：《哈爾濱工業(yè)大學(xué)》2015年碩士論文

【摘要】：碳粘結(jié)碳纖維復(fù)合材料(carbon bonded carbon fiber composites CBCF),是一種低密度的短纖維碳/碳復(fù)合材料,具有高孔隙率、低密度、優(yōu)異的耐高溫特性以及較好的結(jié)構(gòu)穩(wěn)定性,被廣泛用作氣氛熱解爐以及通用熱源燃料倉的隔熱材料。同時,利用該材料為增強相,通過浸漬酚醛樹脂氣凝膠得到新型超輕質(zhì)燒蝕型熱防護復(fù)合材料,可廣泛應(yīng)用于航空航天飛行器的熱防護領(lǐng)域。本文采用低熱導(dǎo)率的粘膠基碳纖維,通過水性漿料壓濾成型、干燥、固化、碳化等工藝流程,制備了碳粘結(jié)碳纖維復(fù)合材料,這是一種是由裂解碳粘結(jié)相互獨立的短切纖維構(gòu)成的高孔隙率碳/碳復(fù)合材料。材料表面及內(nèi)部纖維分布均勻,沒有團聚,成束,分層等缺陷,碳纖維在高溫處理后保持其原有的長直結(jié)構(gòu)特點。在加壓過程中短切碳纖維趨向垂直于壓力方向的面內(nèi)排布,纖維在垂直于壓力的方向形成層狀結(jié)構(gòu)而在平行于壓力方向的平面內(nèi)隨機分布。這種微觀結(jié)構(gòu)的各向異性決定了其力學(xué)和熱物理性能的各向異性。短切碳纖維骨架材料的壓縮性能具有各向異性特點。在壓力平行于材料成型時加壓排水方向的平行壓縮過程,材料中表現(xiàn)出一定的“假”塑性特點,在與之垂直方向進行橫向壓縮過程中材料表現(xiàn)出與塑性材料類似的特征。材料的平行壓縮強度S和彈性模量E隨纖維長度的增加而降低,隨材料密度增大而增加,并且密度越高受材料密度變化的影響越大;橫向壓縮時材料的屈服強度和能量密度基本不受纖維長度影響,隨材料密度增加而增大。針對短切碳纖維骨架材料沿不同方向簡化的二維模型、材料整體的三維模型計算其熱導(dǎo)率,分析各項異性特點。改變纖維取向和密度,通過隨機生長-生成方法建立了二維條件下的材料模型,并利用格子Boltzmann方法求解材料熱導(dǎo)率。結(jié)果顯示纖維取向角的限值為90°時,纖維在平面內(nèi)呈隨機分布,材料導(dǎo)熱呈現(xiàn)各向同性特點,隨著纖維取向角限值θ的減小,材料沿溫度梯度方向熱導(dǎo)率逐漸增大,垂直于溫度梯度方熱導(dǎo)率逐漸減小,其各項異性程度顯著增加;材料熱導(dǎo)率隨著纖維體積分數(shù)的增加呈近似線性的增長趨勢。利用Geo Dict軟件根據(jù)纖維取向張量建立了不同三維層狀模型并計算其熱導(dǎo)率,材料導(dǎo)熱性能仍呈各項異性,隨層狀程度增加其各項異性程度加劇。利用激光脈沖法測試材料室溫條件下的熱導(dǎo)率,結(jié)果與與計算結(jié)果一致,顯示材料在不同方向表現(xiàn)出明顯的各項異性特點。但兩方向熱導(dǎo)率的各向異性比為0.8左右,小于計算值(不高于0.54)。碳粘結(jié)點在x-y方向抑制熱量傳遞而在z向促進熱量傳遞導(dǎo)致材料熱導(dǎo)率呈現(xiàn)的各向異性程度相較于計算結(jié)果偏小。
[Abstract]:Carbon bonded carbon fiber composite (carbon bonded carbon fiber composites CBCF) is a low density short fiber carbon / carbon composite with high porosity, low density, excellent high temperature resistance and good structural stability. It is widely used as heat insulation material for atmosphere pyrolysis furnace and general heat source fuel bunker. At the same time, by impregnating phenolic resin aerogel, a new type of ultra-light ablative thermal protection composite material was obtained by using the material as reinforcement phase, which can be widely used in the thermal protection field of aerospace vehicles. In this paper, carbon bonded carbon fiber composites were prepared by low thermal conductivity viscose based carbon fibers, which were prepared by water slurry pressure filtration molding, drying, curing, carbonization and other processes. This is a kind of high porosity carbon / carbon composite composed of short cut fibers which are independent of cracking carbon bond. The fibers on the surface and inside of the material are uniformly distributed, without agglomeration, bunching, delamination and other defects. The carbon fiber keeps its original long and straight structure after high temperature treatment. During compression, the short cut carbon fibers tend to be arranged in plane perpendicular to the pressure direction, and the fibers are randomly distributed in the cambium structure perpendicular to the pressure direction and in the plane parallel to the pressure direction. The anisotropy of the microstructure determines the anisotropy of its mechanical and thermophysical properties. The compression properties of short cut carbon fiber skeleton are anisotropic. In the process of parallel compression of pressure and drainage direction when the pressure is parallel to the material forming, the material shows certain "pseudo-plastic" plastic characteristics, and the material exhibits similar characteristics to the plastic material in the process of transverse compression in the vertical direction. The parallel compressive strength S and elastic modulus E decrease with the increase of fiber length and increase with the increase of material density, and the higher the density is, the greater the change of material density is. The yield strength and energy density of the material under transverse compression are not affected by the fiber length, but increase with the increase of the material density. According to the simplified two-dimensional model of short cut carbon fiber skeleton material in different directions, the three-dimensional model of the material is used to calculate its thermal conductivity and analyze the heterogeneity. By changing the orientation and density of the fibers, the material model under two dimensional conditions was established by random growth-generation method, and the thermal conductivity of the materials was calculated by the lattice Boltzmann method. The results show that when the limiting value of the fiber orientation angle is 90 擄, the fiber is randomly distributed in the plane, and the heat conduction of the material is isotropic. With the decrease of the limiting value 胃 of the orientation angle, the thermal conductivity of the material increases along the temperature gradient. The thermal conductivity perpendicular to the temperature gradient decreases gradually and the heterogeneity increases significantly, and the thermal conductivity increases linearly with the increase of fiber volume fraction. Geo strict software was used to establish different three-dimensional layered models based on fiber oriented Zhang Liang and calculate their thermal conductivity. The thermal conductivity of the material is still different, and the heterogeneity of the material increases with the increase of the laminar degree. The laser pulse method is used to measure the thermal conductivity of the materials at room temperature. The results are in agreement with the calculated results and show that the materials show obvious heterogeneity in different directions. However, the anisotropy ratio of the two directions is about 0.8, which is less than the calculated value (not more than 0.54). Carbon bond point inhibits heat transfer in x-y direction and promotes heat transfer in z direction. The anisotropy of thermal conductivity of the material is smaller than that of the calculated results.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TB332

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本文編號：2063373