【作者】 李莹；

【导师】 姜波；

【作者基本信息】 哈尔滨工业大学 ， 化学工程与技术， 2022， 博士

【摘要】 碳纤维复合材料由于具有耐磨、耐腐蚀、轻质高强等优点而被广泛地应用于航空航天、运动器械和武器装备三大领域,随着应用范围的扩大,人们对其性能也提出更高的要求。然而碳纤维复合材料目前仍存在一些问题,表面光滑、惰性的碳纤维表面与树脂基体的界面浸润性较差从而限制材料本身力学性能的发挥。目前,主要通过对碳纤维表面改性的方式提高碳纤维与基体树脂的界面性能,即使二者间的界面结合较好,在受到较大的外力后界面区域会产生微裂纹导致界面失效从而影响材料的使用寿命。因此,本文通过在碳纤维表面引入金属有机框架（MOF）提高碳纤维与树脂界面性能,分析了碳纤维复合材料的界面增强机制。进一步研究了在热和光的刺激下以MOF为载体的界面自修复行为。通过在碳纤维表面引入UiO-66-M构筑了基于Diels-Alder（DA）热可逆动态化学键的界面自修复体系。通过水热法和后合成改性法（PSM）制备了Ui O-66-M@CF。Ui O-66-M在纤维表面以纳米颗粒的状态均匀分布,能够提升纤维表面的粗糙度、改善纤维的微观形貌。结果表明PSM并没有破坏MOF的形貌与晶体结构。与未改性碳纤维相比,改性后碳纤维的界面剪切（IFSS）与层间剪切（ILSS）分别提高了39.53%和16.62%。而且,引入MOF的过程并没有对纤维造成破坏。同时,研究了基于DA反应的界面自修复行为,环氧树脂中添加了Ui O-66-M和含有呋喃结构的缩水呋喃糠醚（FGE）。当改性后的纤维与树脂体系间的界面发生失效后,纤维表面Ui O-66-M所含有的马来酰亚胺基团与树脂基体中的呋喃结构形成的共价键断裂,加热后发生DA反应而再次成键使破坏的界面得到修复。三次界面自修复的修复率分别为89.96%、90.6%和80.94%。为了克服DA反应对温度的要求,在碳纤维表面引入能够光响应的Cu₂（F₂Azo BDC）₂Dabco,这种MOF不但能够改善碳纤维的界面性能还能作为外援型修复剂载体实现光响应自修复。合成了带有偶氮苯结构的F₂Azo BDC,并以此为配体通过水热的方式在碳纤维表面引入了能够在530 nm和400 nm光刺激下发生构型转化的Cu₂（F₂Azo BDC）₂Dabco。经过水热方式改性12小时的纤维界面性能最佳,相对于未处理的碳纤维,改性后的IFSS和ILSS分别提高了51.70%和25.44%。Cu₂（F₂Azo BDC）₂Dabco能在绿光和紫光的照射下实现顺式-反式的构型转化,这两种构型的MOF极性差异较大。因此,以MOF作为载体来负载修复剂可以通过光照控制MOF的构型来达到控制修复剂负载和释放的目的。纤维与树脂微滴的界面受到破坏后,利用紫光控制负载吸附剂的MOF释放修复剂来修复界面,光的控制能够实现修复剂的精准、多次释放,修复率分别为96.31%、80.71%、75.28%。层层自组装法（LbL）在基体材料引入MOF能够抑制晶体过度成核有利于得到均匀的MOF结构。因此,为了克服水热反应制备的MOF在碳纤维表面聚集的问题,利用Lb L在碳纤维表面引入能够紫外光响应的Zn（Az DC）（4,4-BPE）_0.5。作为对比也通过水热法在纤维表面引入这种MOF。结果表明通过Lb L法改性后MOF呈纳米片状均匀分布在碳纤维表面,Lb L法沉积10层MOF纤维（Zn ABCN-10）的IFSS相对于原丝提高了38.71%,其值为75.46 MPa,相对于未处理碳纤维提高了70.3%。单丝拉伸、IFSS结果表明Lb L法制备的纤维性能更好。由于MOF中的两种配体均具备光响应效应,所以MOF也能够在光的刺激下发生顺-反异构。因此该MOF可以作为修复剂载体,最佳修复率分别为97.01%。更多还原

【Abstract】 Carbon fiber(CF)is used to prepare carbon fiber composites due to its excellent mechanical properties,good heat resistance and corrosion resistance,and light weight.CF composite materials are widely used in aerospace,cycling and civil applications.With the development of application,people also put forward higher requirements for its performance.However,there are still some problems in carbon fiber composite materials.Because of smooth and chemical inertness of CF,the interface between the fiber and resin matrix is poor which limit the mechanical property of composites.Even if the interface between them is well combined,the interface will still produce micro-cracks after receiving external force over loaded,which will lead to interface failure and affect the service life of the material.Therefore,it is very necessary to modify the surface of carbon fiber to improve the interfacial properties of carbon fiber and matrix resin and to further realize self-healing of the interface.In this thesis,MOF were introduced on the fiber surface to improve the interfacial properties with resin,and the mechanism of interfacial enhancement was analyzed and investigated.The interfacial self-healing behavior with MOF as platform was further studied.An interfacial self-healing system based on Diels-Alder(DA)thermoreversible dynamic chemical bonds was constructed by introducing Ui O-66-M on the surface of carbon fibers.Ui O-66-M was prepared by hydrothermal synthesis and post-synthetic modification(PSM)and uniformly distributed in the state of nanoparticles on the fiber surface.Ui O-66-M can improve the roughness of the fiber surface and improve the microscopic morphology of the fiber.The results showed that PSM did not destroy the morphology and crystal structure of MOF.Compared with the unmodified carbon fiber,the IFSS and ILSS of the modified carbon fiber were increased by 39.53% and 16.62%,respectively.Meanwhile,the interfacial self-healing behavior based on DA reaction was studied,Ui O-66-M and furfuryl glycidyl ether(FGE)which containing furan structure were added to epoxy resin.When the interface between the modified fiber and the resin system fails,the covalent bond formed by the maleimide group contained in Ui O-66-M on the fiber surface and the furan structure in the resin matrix is broken,which occurs after heating.DA reacts to bond again so that the damaged interface is repaired.The healing efficiency of the three interface self-healing were 89.96%,90.6% and 80.94%,respectively.To overcome the temperature requirement of DA reaction,Cu2(F2Azo BDC)2Dabco,which can respond to light,was introduced on the surface of carbon fiber.This MOF can not only improve the interface properties of carbon fiber,but also can be used as an external repair agent carrier to realize light-responsive self-healing.F2 Azo BDC with an azobenzene structure was synthesized,and Cu2(F2Azo BDC)2Dabco,which can undergo isomerization under530 nm and 400 nm light stimulation,was introduced on the surface of carbon fiber by hydrothermal method.Compared with the untreated carbon fiber,the modified IFSS and ILSS increased by 51.70% and 25.44%,respectively.Cu2(F2Azo BDC)2Dabco can occur cis-trans isomerzation under the irradiation upon green light and violet light,and the MOF polarities of two isomer are significantly different.Therefore,using MOF as a carrier to load healing agent can control the isomer of MOF by light to control the loading and releasing of healing agent.After the interface between the fiber and the resin droplet was damaged,the MOF loaded healing agent was trigered by violet light to release the repair agent to repair the interface.The light control can realize the precise and multiple release of the repair agent,and the repair rates are 96.31%,80.71%,75.28%.The layer-by-layer self-assembly method(Lb L)can limit the crystal formation and is beneficial to obtain a uniform MOF structure.Therefore,in order to overcome the aggregation phenomenon of MOF prepared by hydrothermal reaction on the surface of carbon fiber,Lb L was used to introduce Zn(Az DC)(4,4-BPE)0.5,which can induce by UV light,on the surface of carbon fiber.The results show that the MOF porducted by Lb Lwere uniformly distributed on the CFsurface as nanosheets.As a comparison,this MOF was also introduced on the fiber surface by a hydrothermal method.The surface energy of fibers prepared by Lb L method after 10 cycles was 38.71% higher than that of the fiber prepared by hydrothermal method,and its IFSS is 75.46 MPa.Compared with the pristine CF,it increased by 70.3%.The results of single fiber tensile strenth and IFSS show that the properties of fibers prepared by Lb L method have a better performance.The photo-responsive ligands lead to MOFs can also undergo cis-trans isomerism under the stimulation of light.Therefore,MOF can be used as a repair agent carrier,and multiple interface self-healing can be achieved by light control,and the healing efficiency were 97.01% and 81.4%,respectively.更多还原