【作者】 陈磊；

【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， 2015， 博士

【摘要】 近年来,PBO纤维因具有优异的力学性能、热学性能以及化学稳定性而被广泛地用作先进复合材料的增强体。然而,由于PBO纤维表面光滑且呈化学惰性,与树脂基体之间的相容性较差,致使两者之间的界面结合强度较低,严重影响复合材料综合性能的发挥。当航天器在低地球轨道(Low earth orbit,LEO)运行时,用作结构材料的PBO纤维/环氧复合材料极易受到原子氧(Atomic oxygen,AO)的侵蚀,尤其是当表面的防护层失效之后,原子氧会与底层的环氧树脂发生相互作用,氧化形成大量缺陷,并通过这些缺陷进一步渗透到复合材料的界面区域,造成纤维增强体与树脂基体脱粘,从而导致复合材料的力学性能大幅下降。本文分别采用化学镀、低温水热法及化学接枝法,有针对性的在PBO纤维/环氧复合材料中引入镍磷合金、氧化锌纳米线(Zinc oxide nanowires,Zn O NWs)、有机硅-氧化石墨烯三种界面相,旨在同时有效解决界面结合强度较差和原子氧防护两大难题。采用化学镀法对PBO纤维进行改性处理,从而在复合材料中引入镍磷合金界面相。通过改变施镀温度和时间,系统地研究了施镀工艺参数、表面形貌以及界面性能三者之间的关系。镀镍PBO纤维表面的镀层由镍和磷两种元素组成,为典型的非晶态结构。镀镍层表面的刚性镍颗粒极大地提高了纤维表面的粗糙度,增加了其与树脂之间的接触面积,还会对外载荷产生强烈的阻碍作用,从而使复合材料的界面性能得到改善。当施镀温度为80℃、施镀时间为20min时,PBO纤维复合材料的界面剪切强度提高幅度最大,达到38.6%。与此同时,镀镍PBO纤维复合材料的耐湿热老化性能得到了较为明显的改善。随着热处理温度的升高,镀镍PBO纤维复合材料的界面剪切强度呈下降趋势。结合PBO纤维表面羧基功能化技术和低温水热法对PBO纤维进行改性处理,从而在复合材料中引入Zn O NWs界面相。经过羧基功能化处理后,纤维表面的羧基官能团相对含量大幅提高,保证了纤维与Zn O NWs之间结合的牢固程度,能够最大幅度地提高PBO纤维复合材料的界面剪切强度。Zn O NWs在界面区域形成的强大机械锁合作用和良好浸润性是复合材料界面性能得到改善的主要原因。与未处理PBO纤维相比,生长有Zn O NWs的PBO纤维(PBO-Zn O NWs)的拉伸强度并未出现明显下降。通过改变Zn O种子溶液与生长溶液浓度的比例([S]/[G])和生长时间,控制纤维表面Zn O NWs的形貌,系统地研究了生长工艺参数、表面形貌以及界面性能三者之间的关系。当[S]/[G]比例为2、生长时间为4h时,PBO-Zn O NWs杂化纤维复合材料的界面剪切强度提高幅度最大,达到50.7%。与此同时,杂化纤维复合材料的耐湿热老化性能得到了小幅度的改善。结合PBO纤维表面羟基功能化技术和化学接枝法对PBO纤维进行改性处理,从而在复合材料中引入有机硅-氧化石墨烯二元界面相。PBO纤维表面官能团的变化证实3-氨丙基-三甲氧基硅烷(APTMS)和氧化石墨烯(GO)通过化学键合作用先后成功地引入到了纤维表面,制备了一种二元接枝的多尺度增强体(PBO-APTMS-GO)。化学接枝工艺未对PBO纤维的本体强度带来明显的负面影响。与未处理PBO纤维相比,PBO-APTMS-GO二元接枝纤维复合材料的界面剪切强度提高了61.6%。氧化石墨烯表面独特的褶皱结构和丰富的极性官能团提高了纤维表面的粗糙度、浸润性及化学反应活性,因而复合材料的界面性能得到显著改善。与此同时,二元接枝纤维复合材料的耐湿热老化性能得到了极大改善。采用扫描电子显微镜(SEM)、X射线衍射(XRD)、傅里叶红外光谱(FTIR)以及X射线光电子能谱(XPS)等测试手段,首次探讨了原子氧对PBO纤维的侵蚀行为。研究发现,随着原子氧暴露时间的延长,PBO纤维的表面形貌、结晶结构及化学组分均发生明显变化,纤维和树脂基体由于受到原子氧的轰击和氧化作用,损伤程度逐渐增加。三种界面相对PBO纤维及其复合材料均取得了较好的原子氧防护效果。经过原子氧暴露8h后,PBO-APTMS-GO二元接枝纤维及其复合材料保持了最高的拉伸强度和界面剪切强度。更多还原

【Abstract】 In recent years, PBO fibers have been widely used as reinforcements of advanced composite materials because of the excellent mechanical properties, thermal properties and chemical stability. However, due to the surface smoothness and chemical inertness, PBO fibers have poor compatibility with resin matrix, leading to low interfacial adhesion between them, which seriously affected the whole performance of composites. When spacecraft flies in low earth orbit(LEO), PBO fiber/epoxy composites used as structural materials are highly vulnerable to atomic oxygen(AO) erosion. When the protective layer of composites surface fails, AO will interact with the epoxy resin underneath and further generate a lot of defects. AO can penetrate into the interfacial region of the composites through these defects, which leads to the debonding between fiber reinforcements and resin matrix, and further degrades the mechanical properties of composites. In this paper, to simultaneously enhance the interfacial properties and AO erosion resistance, nickel phosphorus alloy, Zinc oxide nanowires(Zn O NWs) and silicon-graphene oxide were introduced into PBO fiber/epoxy composites as interphases by using a electroless plating method, low temperature hydrothermal method and chemical grafting method, respectively.The surface of PBO fibers was modified by electroless plating method, and then nickel phosphorus alloy was introduced into composites as interphase. The relationship among process parameters, surface morphology and interfacial properties was systematically studied by changing the plating temperature and time. Nickel-plated PBO fiber surface consisted of nickel and phosphorus, and nickel coating was typically amorphous. Rigid nickel particles on the coating can significantly increase the surface roughness and the contact area between fiber and resin matrix, and generate reacting force to external load. Thus, the interfacial properties of composites were enhanced. When the plating temperature was 80℃ and plating time was 20 min, the interfacial shear strength of composites increased by 38.6%. Meanwhile, the hygrothermal aging resistant properties of the nickel-plated PBO fiber composites were greatly improved. With the increase of heat treatment temperature, the interfacial shear strength of the nickel-plated PBO fiber composites decreased.Carboxyl functionalization technique and low-temperature hydrothermal method were combined to modify the surface of PBO fiber, and then Zn O NWs were introduced into composites as interphase. After the functionalization process, the relative content of carboxyl groups on the fiber surface greatly increased, which ensured the high adhesive durability between fiber and Zn O NWs. Strong mechanical interlocking and good wettability were the main contributors for the enhanced interfacial properties of composites. Compared with the untreated PBO fiber, the tensile strength of PBO fiber after growth of Zn O NWs(PBO-Zn O NWs) had no discernable decrease. The surface morphology of Zn O NWs were controlled by changing the seed-to-growth solution concentration ratio([S]/[G]) and growth time, and the relationship among process parameters, surface morphology and interfacial properties was systematically studied. When [S]/[G] was 2 and growth time was 4h, the interfacial shear strength of composites increased by 50.7%. Meanwhile, the hygrothermal aging resistant properties of the PBO-Zn O NWs composites were slightly improved.Hydroxyl functionalization technique and chemical grafting method were combined to modify the surface of PBO fiber, and then silicon-graphene oxide was introduced into composites as binary interphase. The variation of functional groups on the surface of PBO fiber confirmed that 3-aminopropyltrimethoxysilane silane(APTMS) and graphene oxide(GO) were introduced onto the fiber surface successfully via chemical bonding, and a binary grafted multi-scale reinforcement(PBO-APTMS-GO) has been prepared. The tensile strength of PBO fiber was not affected by the chemical grafting process. Compared with the untreated PBO fiber composites, the interfacial shear strength of PBO-APTMS-GO composites increased by 61.6%. The unique fold structure and numerous polar functional groups of GO improved the surface roughness, wettability and chemical reactivity of fiber surface, hence, the interfacial properties of composites were significantly enhanced. Meanwhile, the hygrothermal aging resistant properties of PBO-APTMS-GO composites were remarkably improved.Scanning electron microscopy(SEM), X-ray diffractometer(XRD), fourier transform infrared spectroscopy(FTIR) and X-ray photoelectron spectroscopy(XPS) were employed to investigate the AO erosion behavior of PBO fibers for the first time. Experimental results indicated that the surface morphology, crystal structure and chemical composition of PBO fibers changed obviously with the increase of AO exposure time. Meanwhile, PBO fibers and resin matrix were damaged with the increase of AO exposure time due to its sputtering and oxidation. The three kinds of interphases can effectively protect the PBO fibers and their composites. After 8h AO accelerated aging, PBO-APTMS-GO and its composites maintained the highest tensile strength and interfacial shear strength.更多还原