【作者】 张艳华；

【导师】 黄玉东；

【作者基本信息】 哈尔滨工业大学 ， 化学工程与技术， 2008， 博士

【摘要】 芳纶纤维/环氧树脂复合材料是理想的火箭发动机壳体材料,然而芳纶纤维表面光滑和化学惰性的缺点使其与环氧树脂之间的界面粘结不良,限制了其在航空航天领域的应用。为此本文采用60Coγ-射线辐照技术,对芳纶(Armos)纤维进行辐照和辐照接枝改性研究,提高纤维与树脂基体的界面粘结性能。通过优化设计辐照工艺参数和辐照接枝单体,在不降低纤维本体强度的前提下实现纤维表面改性,从而全面提高芳纶纤维复合材料的综合性能。采用层间剪切强度(ILSS)测试、界面剪切强度(IFSS)测试、弯曲强度测试和纳米硬度测试等测试方法研究了辐照和辐照接枝对芳纶/环氧树脂复合材料界面性能的影响。确定了对Armos纤维改性效果好的辐照处理方式:即对Armos纤维在氮气中600kGy、空气中600kGy辐照;对Armos纤维分别在环氧氯丙烷中200kGy、5%环氧/丙酮中500kGy和1.5%酚醛/乙醇中500kGy共辐照接枝。Armos纤维单丝拉伸强度测试结果表明,辐照和辐照接枝对纤维的本体强度损伤程度很低。通过X射线衍射(XRD)和碳核磁共振谱(13C-NMR)研究辐照改性前后芳纶纤维结构的变化。XRD分析表明辐照可以使纤维的结晶结构发生微小变化,且在氮气介质中经600kGy辐照处理后纤维的晶面间距最小;13C-NMR研究表明纤维上C=O和C=N官能团的含量明显减少。辐照处理后纤维浓硫酸溶液的比浓粘度增加、复合材料纤维压痕直径变小、复合材料纤维纳米硬度提高和单丝拉伸断口形貌观察结果均表明辐照使得Armos纤维内部发生交联反应。纤维结构的变化导致纤维性能的改善。芳纶纤维钩接强力测试表明,辐照和辐照接枝均能提高芳纶纤维的压缩性能;热失重分析表明,辐照可以改善纤维的耐热性能。采用X-射线光电子能谱(XPS)、扫描电子显微镜(SEM)、原子力显微镜(AFM)、傅立叶红外测试(FT-IR)和浸润性测试(Capillary method)等测试方法研究γ-射线辐照和辐照接枝对Armos纤维表面性能的影响。FT-IR分析表明在γ-射线辐照作用下环氧氯丙烷、环氧和酚醛树脂可以接枝到纤维表面,使得纤维表面接枝上活性官能团;XPS分析表明处理后纤维表面的O/C增加,活性官能团含量均有提高;采用SEM和AFM对纤维表面形貌观察分析发现改性使得纤维表面的粗糙度增加;浸润测试结果表明处理后纤维在环氧树脂中的浸润性能有不同程度的改善,且其表面能都得到了提高。纤维表面的粗糙度增加使得纤维与基体树脂之间的机械啮合作用增强,纤维表面活性官能团含量的提高增强了纤维和树脂间形成的化学键作用,这些改善了纤维在环氧树脂中的浸润性能,最终使得Armos纤维/环氧树脂复合材料的界面粘结性能得到提高。对辐照和辐照接枝处理后的Armos纤维在干燥器中放置6个月后,通过单丝拉伸强度和复合材料ILSS的变化研究芳纶纤维表面活化的退化效应。结果表明放置后的纤维单丝拉伸强度和复合材料的ILSS基本保持不变。更多还原

【Abstract】 Aramid fibers/epoxy resin composite is a preferred candidate material for outer shell of rocket motor. Unfortunately, the adhesion between fibers and the resin matrix is poor because the surface of aramid fibers is chemically inert and smooth. This adhesion problem has to be solved so that the composites can be widely applied in aircraft, aerospace and missile fields. In this thesis, Co60γ-ray irradiation and irradiation grafting techniques were used to modify aramid (Armos) fibers in order to improve the adhesion between aramid fibers and epoxy resin. Irradiation parameters were studied and various grafting monomers were tested to achieve desired modifications of Armos fibers without lowering the strength of fibers. The overall properties including the interface adhesion of aramid fibers composites were significantly improved after modification.The interlaminar shear strength (ILSS) test, interfacial shear strength (IFSS) test, flexural strength test and nanohardness test were adopted to study the effects of irradiation and irradiation grafting on the properties of Aramid fibers/epoxy resin composites. The optimal irradiation doses in various mediums were determined as 600kGy in N2, 600kGy in air, 500kGy in 5% epoxy resin/acetone, 500kGy in 1.5% phenol-formaldehyde resin/acetone, 200kGy in epoxy chloropropane. The quasistatic tensile test of single Armos fiber showed thatγ-ray radiation and irradiation grafting didn’t significantly reduce tensile strength of Armos fibers.X-ray diffraction (XRD) and carbon nuclear magnetic resonance spectroscopy (13C-NMR) were adopted to study the structure change of Armos fibers after irradiation. The crystallinity of Armos fibers after irradiation varied only slightly and the interplanar distance was smallest at 600kGy in N2. 13C-NMR results showed the contents of C=O and C=N groups in Armos fibers were lowered after irradiation. It was found that the cross-linking reaction occurred in the bulk of Armos fibers during irradiation. The in-depth cross-linking reaction was evidenced by higher viscosity of fibers/concentrated H2SO4 solution, smaller indentation diameter and higher nanohardness together with modified fractography of fibers. Therefore, it was the structure change that accounts for the improvement of fiber properties. The loop force test with two single fibers showed that the compression resistance of fibers was increased. The thermogravimetic analyses indicated that the thermal stability of Armos fibers was improved by irradiation and irradiation grafting modification.The effects of irradiation and irradiation grating on the surface properties of fibers have been investigated by X-ray photoelectron spectroscopy (XPS), capillary method, scanning electron microscope (SEM), atomic force microscope (AFM), Fourier transform infrared (FT-IR) technique and viscosity test. FT-IR showed epoxy chloropropane, epoxy resin and phenol-formaldehyde resin all grafted to fibers via active functional groups on the surface of fibers helped by radiation. XPS indicated the atomic ratio of O/C and the contents of polar groups on the surface of fibers were enhanced after irradiation. After modification the surface of Armos fibers was rougher as examined by SEM and AFM. The surface energy increased and the wettability of fibers improved through modification. The higher roughness of fibers’surface led to mechanically stronger interfacial interlocking between the irradiated the fibers and the matrix. Large amount of active functional groups cause chemical binding between fibers and the matrix. Therefore, the improvement of the Armos fibers’wettability in the epoxy resin led to stronger interfacial binding between the fibers and the matrix.The aging test of Armos fibers afterγ-ray irradiation activation was carried out. The tensile strength of fibers and ILSS test of composite showed that the modified fibers were stored in the desiccator for 6 months, the strength of fibers and the ILSS of composites didn’t significantly change.更多还原