聚酰亚胺纤维增强树脂基复合材料的制备与性能研究

发布时间：2018-06-16 03:38

本文选题：复合材料 + 改性处理　；参考：《江南大学》2017年硕士论文

【摘要】：高性能纤维增强树脂基复合材料在航空卫星、机车动车、电机器件等领域发挥的作用越来越大,近年来树脂基复合材料的综合性能一直是关注的热点。高性能树脂基复合材料的纤维增强体与树脂基体之间良好的界面相容性是决定复合材料性能高低的关键,所以对纤维作适当的改性处理可以改善复合材料的界面结构,进而优化材料的宏观性能。另外,复合材料中纤维的存在形式、分布情况、均匀程度等也影响了材料性能,传统的纤维直接增强树脂存在纤维有效长度低、空洞孔隙多、分布不均、材料性能不稳定等问题。本研究的目的是采用有效的方法对聚酰亚胺纤维表面进行功能化改性,提高纤维表面性能,利用湿法造纸成形技术抄取纤维纸增强体,制备出界面相容性好、力学性能优越的树脂基复合材料。本课题以干法纺二步法聚酰亚胺纤维为原料,NaOH、HCl、H_2O_2为湿化学介质,研究了聚酰亚胺纤维在三种介质中细度、力学性能、热失重性能、化学结构、浸润性能、表面微观形貌及微观聚集态结构的具体变化。结果表明:纤维经三种湿化学介质处理后细度和力学性能下降,且随着湿化学介质浓度和温度提高、处理时间延长,纤维细度变小和力学性能下降趋势加快;纤维在OH~-、H~+作用下,开环水解为聚酰胺酸或其盐,分子链中酰亚胺环的部分C-N键发生断裂,导致纤维热失重性能、化学结构及微观聚集态结构发生改变,SEM表明纤维表面变得不再光滑,粗糙化程度增加,局部被介质刻蚀。采用适当的处理工艺,有助于聚酰亚胺纤维表面进行功能化改性。结合聚酰亚胺纤维在NaOH、HCl、H_2O_2三种湿化学介质中结构及性能的具体变化,采用HNO_3/H_2SO_4混酸对纤维进行改性处理,改性后的聚酰亚胺纤维表面出现刻蚀沟槽,沟槽意味着比表面积增加,表面变得粗糙,当HNO_3/H_2SO_4体积比为1:2、1:1、2:1,氧化25min时,纤维表面O/C比值分别为0.6268、0.4133、0.3497。浸润性能明显改善,随着H_2SO_4配比提高、处理时间延长,浸润性能改善趋势加快,同时,纤维因润胀细度上升,力学性能下降,质量增加,改性后的聚酰亚胺纤维化学结构变化不明显,纤维表层有一部分结晶区转化为非结晶区,转化过程中纤维分子的取向结构和超分子结构受到影响,聚合物分子链变松弛,刚性下降,微观聚集态结构有序性受到破坏,非结晶区比值的上升,对纤维浸润性能也有促进作用。以改性后的纤维为增强体,聚丙烯为基体,采用热压成型法制备聚丙烯树脂基复合材料,对材料的力学性能进行测试。结果表明:纤维表面O/C比值、粗糙度、浸润性能及纤维自身强度等因素共同决定了复合材料的力学性能,其中材料的界面剪切性能分别提高97.74%、25.37%、5.82%;弯曲性能分别提高28.03%、26.26%、24.15%;拉伸性能降低54.39%,提高22.27%,降低2.75%。为了解决目前不连续纤维增强复合材料中存在的纤维束多、孔径分布不匀、有效长度低、材料性能不高等问题,本课题从增强体结构、应力传递、成型方式等角度出发,借助传统的湿法造纸成形技术,将纤维抄造成纤维纸,纤维纸的增强形式有效克服了纤维直接增强的弊端。与短纤维直接增强相比,纤维纸中纤维束少,纤维孔径小并且分布均匀,纤维有效长度提高。纤维纸作为一种疏松多孔的结构材料,有利于基体树脂在热压条件下与纤维复合。采用手糊-热压成型工艺制备纤维、纤维纸增强聚酰亚胺树脂基复合材料,控制纤维质量分数在40%,与纤维增强复合材料相比,纤维纸增强复合材料拉伸性能提高130%,弯曲性能提高108%,层间剪切性能提高34.5%。纤维纸的抄造工艺条件对复合材料的力学性能也会产生影响:6mm未打浆纤维纸力学指标较好,与3mm未打浆纤维纸相比,6mm未打浆纤维纸增强复合材料的拉伸性能提高23.53%,弯曲性能提高47.02%,层间剪切性能变化不大;打浆纤维纸增强复合材料比未打浆纤维纸增强复合材料的拉伸性能提高59.97%,弯曲性能增加39.14%,层间剪切性能下降5.39%;随着纤维纸定量的增加,复合材料弯曲、层间剪切性能一直增加,拉伸性能先上升再下降,在100g/m2时,取得最大值6.9346Mpa。
[Abstract]:High performance fiber reinforced resin matrix composites have been playing a more and more important role in the fields of aero satellites, locomotive motor cars and motor devices. In recent years, the comprehensive properties of the resin matrix composites have been the focus of attention. The good interfacial compatibility between the fiber reinforced body and the resin matrix of high performance resin matrix composites is determined to be complex. The key of material performance is that proper modification of fiber can improve the interface structure of the composite, and then optimize the macroscopic properties of the material. In addition, the existing form, distribution and uniformity of the fiber in the composite also affect the properties of the material. The purpose of this study is to use effective methods to modify the surface of polyimide fibers by functional modification, improve the surface properties of fiber, and use wet paper forming technology to copy fiber paper reinforcement to prepare resin based composites with good properties and superior mechanical properties. Material. In this subject, two step polyimide fibers were used as raw materials, NaOH, HCl and H_2O_2 as wet chemical medium. The details of the fineness, mechanical properties, thermal weight loss, chemical structure, wettability, surface micromorphology and microstructure of the polyimide fibers in three kinds of medium were studied. The results showed that three kinds of wet chemistry of fiber through three kinds of wet chemistry were found. The fineness and mechanical properties of the medium after treatment are decreased, and with the increase of the concentration and temperature of the wet chemical medium, the treatment time is prolonged, the fiber fineness becomes smaller and the trend of mechanical properties is accelerated. Under the action of OH~- and H~+, the open ring is hydrolyzed to polyamide acid or its salt, and the partial C-N bond of the imide ring in the molecular chain breaks down, resulting in the thermal weightlessness of the fiber. The properties, chemical structure and microstructure of microstructure change. SEM shows that the surface of the fiber is no longer smooth, the degree of roughness is increased, and the local medium is etched. The use of appropriate processing technology is helpful to the functional modification of the surface of polyimide fibers. The structure and the structure of the three wet chemical medium of NaOH, HCl, and H_2O_2 are combined with polyimide fiber. The specific changes in performance are modified with HNO_3/H_2SO_4 mixed acid. The surface of the modified polyimide fibers appears etching grooves. The grooves mean that the surface area is increased and the surface becomes rough. When the volume ratio of HNO_3/H_2SO_4 is 1:2,1:1,2:1, the O/C ratio of the surface of the fiber surface is 0.6268,0.4133,0.3497. wettability, respectively. With the increase of the ratio of H_2SO_4, the prolonging of the treatment time and the improvement of the infiltration performance, the strength of the fibers increased, the mechanical properties decreased and the quality was increased. The chemical structure of the modified polyimide fibers was not changed obviously, and some of the crystalline areas of the fiber surface were transformed into non crystalline regions and the fiber molecules in the transformation process were changed. The orientation structure and supramolecular structure are affected, the molecular chain of the polymer becomes relaxed, the rigidity of the polymer is reduced, the order of the microstructure is destroyed, the ratio of the amorphous region is increased, and the infiltration performance of the fiber is also promoted. The modified fiber is the reinforcement, the polypropylene is the matrix, and the polypropylene resin base is prepared by hot pressing. The mechanical properties of the materials are determined by the factors such as O/C ratio, roughness, wettability and fiber strength. The interfacial shear properties of the materials are increased by 97.74%, 25.37%, 5.82%, respectively, and the bending properties are increased by 28.03%, 26.26%, 24.15%, and tensile properties, respectively. The reduction of 54.39% and 22.27%, and the reduction of 2.75%. in order to solve the problems existing in the current discontinuous fiber reinforced composites, such as many fiber bundles, unevenly distributed pore size distribution, low effective length, and low material performance. This topic from the angle of reinforcement structure, stress transfer, molding method and so on, using the traditional wet process paper forming technology to copy the fiber. The reinforcement of fiber paper and fiber paper can effectively overcome the disadvantage of direct fiber reinforcement. Compared with the short fiber direct enhancement, the fiber paper is small, the pore size is small and the effective length of the fiber is improved. As a porous structure material, the fiber paper is beneficial to the matrix resin and the fiber under the hot pressing condition. The fiber, fiber paper reinforced polyimide resin matrix composites were prepared by hand paste hot pressing process, and the fiber mass fraction was 40%. Compared with the fiber reinforced composites, the tensile properties of the fiber paper reinforced composites increased by 130%, the bending properties increased by 108%, and the interlaminar shear properties improved the processing conditions of 34.5%. fiber paper. The mechanical properties of the composite can also be influenced by the mechanical properties of 6mm non beating fiber paper, and the tensile properties of 6mm unbeaten fiber paper reinforced composites increased by 23.53%, the bending properties increased by 47.02%, and the interlaminar shear properties changed little compared with that of 3mm unbeaten fiber paper, and the pulp fiber paper reinforced composites were more than the non beating fiber paper. The tensile properties of the strong composites are increased by 59.97%, the flexural properties are increased by 39.14%, the interlaminar shear properties decrease by 5.39%. With the increase of the fiber paper, the composite materials bend, the interlayer shear properties have been increased and the tensile properties first rise and then decrease, and the maximum value of 6.9346Mpa. is obtained at 100g/m2.
【学位授予单位】：江南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ327;TB332

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