【摘要】：碳纖維增強環(huán)氧樹脂基復合材料因其比重輕、比強度高、比剛度大、熱膨脹系數小、可設計性強,同時還兼?zhèn)淠透g和抗疲勞等諸多優(yōu)點,在許多領域應用時很好地起到減輕結構重量、降低成本、節(jié)約資源以及優(yōu)化工藝的作用。但是目前,碳纖維增強環(huán)氧樹脂基復合材料在實際工程應用中仍然存在界面結合弱、易發(fā)生脆性斷裂等問題。因此,如果能夠通過簡單、經濟、有效的方法對碳纖維表面進行改性,并對樹脂基體進行增韌改性,這些都必將有效改善復合材料容易分層和脆斷等問題,這對提升碳纖維增強環(huán)氧樹脂基復合材料在多種載荷作用下的力學性能和穩(wěn)定性等具有十分重要的現實意義。本研究首先采用去離子水超聲、濃硝酸浸泡、濃硝酸超聲等不同方式對碳纖維表面改性的效果進行了考察,最后優(yōu)選出了濃硝酸-超聲協同改性的方法,對碳纖維表面進行了成功有效的改性,并對改性后碳纖維及其環(huán)氧樹脂基復合材料的結構和性能進行了詳細研究。其次,通過設計碳纖維平紋布的鋪層角度和順序,考察了不同鋪層方式下復合材料的力學性能,得到了力學性能較佳的復合材料鋪層設計方法。最后,我們用成本較低、簡單易操作和效果顯著的液體丁腈橡膠(LNBR)和納米二氧化硅作為增韌劑,對復合材料增韌改性的效果進行了研究。論文的主要研究內容和創(chuàng)新點如下:(1)用去離子水超聲、濃硝酸浸泡、濃硝酸超聲等對碳纖維進行表面處理,研究了表面處理對碳纖維表面微結構、表面化學組成、相結構、復絲拉伸強度以及改性碳纖維增強環(huán)氧樹脂復合材料的結構和力學性能的影響。研究結果表明:硝酸氧化和超聲處理對碳纖維表面進行了有效改性,其中硝酸處理使碳纖維表面粗糙度和含氧官能團數量顯著增大,超聲處理使碳纖維獲得了良好的分散性并使碳纖維比表面積和含氧官能團增加。而硝酸-超聲協同處理使得碳纖維中的微晶尺寸變小,碳纖維表面活性增大。硝酸氧化與超聲空化相結合強化了碳纖維表面的氧化和刻蝕作用,從而增強了碳纖維與樹脂基體界面之間的“機械錨定”和“化學鍵合”作用,使碳纖維與樹脂之間的界面結合強度得以有效提高,從而顯著改善了復合材料的力學性能。(2)詳細考察了濃硝酸-超聲協同改性碳纖維過程中,處理溫度、超聲時間對改性后碳纖維的失重率、表面微觀形貌、表面化學結構及元素含量、潤濕性、復絲拉伸強度等的影響效果。研究結果表明:隨著硝酸-超聲處理溫度的升高和處理時間的延長,碳纖維表面變得更加粗糙、失重率逐漸增加而復絲拉伸強度不斷降低。同時,碳纖維表面的含氧官能團數量、活性基團含量逐漸增加,從而使得碳纖維與環(huán)氧樹脂間的浸潤性、反應性、機械錨合作用和結合力增大,最終使改性碳纖維增強復合材料的力學性能得以顯著提高。綜合考慮不同條件改性后碳纖維及其增強復合材料的各方面性能,本研究確定了用硝酸-超聲協同改性碳纖維的最佳工藝條件為60℃/2h。(3)通過改變碳纖維平紋布的鋪層角度和鋪層順序,制備了五種不同鋪層方式的復合材料,并對它們的力學性能進行了考察和對比分析。結果表明:隨著纖維鋪層角度和鋪層順序的變化,制備的復合材料力學性能各異,含有(±45)平紋布鋪層的復合材料,它們的拉伸斷裂伸長率有一定幅度的提高,但它們的拉伸強度和拉伸模量明顯下降,復合材料的彎曲強度和彎曲模量也有較為明顯地下降,(±45)平紋布層數越多下降越明顯。最終綜合考慮,確定了拉伸和彎曲性能最佳時的鋪層方式為[(0,90)]4。(4)分別使用LNBR和納米二氧化硅對復合材料進行了增韌改性研究,通過對比增韌劑在不同添加量時復合材料的力學性能,確定出各自的最佳添加量,并結合它們各自的增韌改性機理對實驗數據進行了深入分析。研究結果表示:這兩種增韌劑都可以對復合材料起到增韌補強的作用,二者在改善復合材料力學性能方面又有著各自突出的一面。我們發(fā)現,適宜的LNBR對復合材料的彎曲性能改善效果顯著,復合材料的彎曲強度有了較大的提升,而適宜的納米二氧化硅對復合材料的拉伸性能提高較為突出,可以使復合材料的拉伸斷裂伸長率、拉伸強度和拉伸模量得到較明顯的提高。
[Abstract]:Carbon fiber reinforced epoxy resin matrix composites have many advantages, such as light weight, high specific strength, high specific stiffness, low coefficient of thermal expansion, strong designability, corrosion resistance and fatigue resistance, etc. They play a good role in reducing structural weight, reducing costs, saving resources and optimizing process in many fields. There are still some problems in the application of fiber reinforced epoxy resin matrix composites, such as weak interfacial bonding and brittle fracture. Therefore, if the surface of carbon fiber can be modified by simple, economical and effective methods, and the resin matrix can be toughened, these will effectively improve the easy delamination and fracture of the composites. Brittleness and fracture of carbon fiber reinforced epoxy resin matrix composites have important practical significance for improving the mechanical properties and stability of carbon fiber reinforced epoxy resin matrix composites under various loads. The method of concentrated nitric acid-ultrasonic synergistic modification was optimized, and the surface of carbon fiber was successfully and effectively modified. The structure and properties of the modified carbon fiber and its epoxy resin matrix composites were studied in detail. Secondly, the composite materials under different laying methods were investigated by designing the laying angle and sequence of carbon fiber plain cloth. Finally, the effect of toughening modification of composites was studied by using liquid nitrile-butadiene rubber (LNBR) and nano-silica as toughening agents with low cost, easy operation and remarkable effect. The following: (1) Carbon fibers were treated by ultrasonic wave in deionized water, soaked in concentrated nitric acid and ultrasonic wave in concentrated nitric acid. The effects of surface treatment on the surface microstructure, surface chemical composition, phase structure, tensile strength of carbon fibers and the structure and mechanical properties of carbon fiber reinforced epoxy resin composites were studied. The surface of carbon fibers was effectively modified by acid oxidation and ultrasonic treatment. Nitric acid treatment significantly increased the surface roughness and the number of oxygen-containing functional groups of carbon fibers. Ultrasonic treatment made carbon fibers disperse well and increased the specific surface area and oxygen-containing functional groups of carbon fibers. The combination of nitric acid oxidation and ultrasonic cavitation strengthens the oxidation and etching on the surface of carbon fibers, thus enhancing the "mechanical anchoring" and "chemical bonding" between the interface between carbon fibers and resin matrix, and effectively improving the bonding strength between carbon fibers and resin. (2) The effects of temperature and ultrasonic time on the weight loss, surface micro-morphology, surface chemical structure and element content, wettability and tensile strength of carbon fibers were investigated in detail. With the increase of nitric acid-ultrasonic treatment temperature and treatment time, the surface of carbon fiber becomes more rough, the weight loss rate increases gradually, and the tensile strength of composite fiber decreases continuously. The mechanical properties of the modified carbon fiber reinforced composites were improved significantly with the increase of the combination and binding force. Considering the properties of the modified carbon fiber and its reinforced composites under different conditions, the optimum technological conditions for the modification of carbon fiber by nitric acid-ultrasonic synergism were determined to be 60 C/2h. (3) By changing the carbon fiber. The results show that the mechanical properties of the composites are different with the change of the fiber laying angle and the laying sequence, and the composites containing (+45) plain cloth layers have different mechanical properties. Their tensile elongation at break increased to a certain extent, but their tensile strength and modulus decreased obviously. The bending strength and modulus of the composites also decreased significantly. The more the number of layers of (+45) plain weave, the more obvious the decrease was. Finally, the optimum laying mode for tensile and bending properties was determined to be [(0,90). (4) The composites were toughened with LNBR and nano-silica respectively. The mechanical properties of the composites with different toughening agents were compared and the optimum addition was determined. The experimental data were analyzed in detail according to their toughening mechanism. Both of the toughening agents can play a toughening and reinforcing role in the composite, and both of them have their own prominent aspects in improving the mechanical properties of the composite. The tensile strength and modulus of the composites can be improved obviously by increasing the tensile properties of the composites.
【學位授予單位】：蘭州交通大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ327.3;TB332

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本文編號：2250451