碳纤维增强环氧树脂基复合材料的制备及力学性能研究
发布时间：2018-09-19 14:52
【摘要】：碳纤维增强环氧树脂基复合材料因其比重轻、比强度高、比刚度大、热膨胀系数小、可设计性强,同时还兼备耐腐蚀和抗疲劳等诸多优点,在许多领域应用时很好地起到减轻结构重量、降低成本、节约资源以及优化工艺的作用。但是目前,碳纤维增强环氧树脂基复合材料在实际工程应用中仍然存在界面结合弱、易发生脆性断裂等问题。因此,如果能够通过简单、经济、有效的方法对碳纤维表面进行改性,并对树脂基体进行增韧改性,这些都必将有效改善复合材料容易分层和脆断等问题,这对提升碳纤维增强环氧树脂基复合材料在多种载荷作用下的力学性能和稳定性等具有十分重要的现实意义。本研究首先采用去离子水超声、浓硝酸浸泡、浓硝酸超声等不同方式对碳纤维表面改性的效果进行了考察,最后优选出了浓硝酸-超声协同改性的方法,对碳纤维表面进行了成功有效的改性,并对改性后碳纤维及其环氧树脂基复合材料的结构和性能进行了详细研究。其次,通过设计碳纤维平纹布的铺层角度和顺序,考察了不同铺层方式下复合材料的力学性能,得到了力学性能较佳的复合材料铺层设计方法。最后,我们用成本较低、简单易操作和效果显著的液体丁腈橡胶(LNBR)和纳米二氧化硅作为增韧剂,对复合材料增韧改性的效果进行了研究。论文的主要研究内容和创新点如下:(1)用去离子水超声、浓硝酸浸泡、浓硝酸超声等对碳纤维进行表面处理,研究了表面处理对碳纤维表面微结构、表面化学组成、相结构、复丝拉伸强度以及改性碳纤维增强环氧树脂复合材料的结构和力学性能的影响。研究结果表明:硝酸氧化和超声处理对碳纤维表面进行了有效改性,其中硝酸处理使碳纤维表面粗糙度和含氧官能团数量显著增大,超声处理使碳纤维获得了良好的分散性并使碳纤维比表面积和含氧官能团增加。而硝酸-超声协同处理使得碳纤维中的微晶尺寸变小,碳纤维表面活性增大。硝酸氧化与超声空化相结合强化了碳纤维表面的氧化和刻蚀作用,从而增强了碳纤维与树脂基体界面之间的“机械锚定”和“化学键合”作用,使碳纤维与树脂之间的界面结合强度得以有效提高,从而显著改善了复合材料的力学性能。(2)详细考察了浓硝酸-超声协同改性碳纤维过程中,处理温度、超声时间对改性后碳纤维的失重率、表面微观形貌、表面化学结构及元素含量、润湿性、复丝拉伸强度等的影响效果。研究结果表明:随着硝酸-超声处理温度的升高和处理时间的延长,碳纤维表面变得更加粗糙、失重率逐渐增加而复丝拉伸强度不断降低。同时,碳纤维表面的含氧官能团数量、活性基团含量逐渐增加,从而使得碳纤维与环氧树脂间的浸润性、反应性、机械锚合作用和结合力增大,最终使改性碳纤维增强复合材料的力学性能得以显著提高。综合考虑不同条件改性后碳纤维及其增强复合材料的各方面性能,本研究确定了用硝酸-超声协同改性碳纤维的最佳工艺条件为60℃/2h。(3)通过改变碳纤维平纹布的铺层角度和铺层顺序,制备了五种不同铺层方式的复合材料,并对它们的力学性能进行了考察和对比分析。结果表明:随着纤维铺层角度和铺层顺序的变化,制备的复合材料力学性能各异,含有(±45)平纹布铺层的复合材料,它们的拉伸断裂伸长率有一定幅度的提高,但它们的拉伸强度和拉伸模量明显下降,复合材料的弯曲强度和弯曲模量也有较为明显地下降,(±45)平纹布层数越多下降越明显。最终综合考虑,确定了拉伸和弯曲性能最佳时的铺层方式为[(0,90)]4。(4)分别使用LNBR和纳米二氧化硅对复合材料进行了增韧改性研究,通过对比增韧剂在不同添加量时复合材料的力学性能,确定出各自的最佳添加量,并结合它们各自的增韧改性机理对实验数据进行了深入分析。研究结果表示:这两种增韧剂都可以对复合材料起到增韧补强的作用,二者在改善复合材料力学性能方面又有着各自突出的一面。我们发现,适宜的LNBR对复合材料的弯曲性能改善效果显著,复合材料的弯曲强度有了较大的提升,而适宜的纳米二氧化硅对复合材料的拉伸性能提高较为突出,可以使复合材料的拉伸断裂伸长率、拉伸强度和拉伸模量得到较明显的提高。
[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.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ327.3;TB332
本文编号：2250451
[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.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ327.3;TB332
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