【作者】 王冠；

【导师】 王荣国；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2017， 博士

【摘要】 为了满足于新一代可重复使用航天器(RLV)推进系统燃料贮箱(液氧)的减重设计要求,液氧贮箱用材料逐步采用树脂基碳纤维复合材料(CFRP)取代原有的金属材料,而CFRP中树脂基体与液氧相容性是CFRP能否应用在液氧环境中的关键因素,要求树脂基体具有良好的低温力学强度,热稳定性、优阻燃性和优异的液氧相容性。现今通用的环氧树脂因其结构缺陷,液氧相容性较差,无法满足液氧环境使用要求。近年来出现的双酚A型氰酸酯树脂(CE)由于固化物具有独特的三嗪结构,因而具有优异的耐温性、较好的抗氧化性,并且其工艺性优异,具备用于制备CFRP液氧贮箱材料的潜质,但是其低温韧性差、阻燃性不足,需要改性应用。目前关于改性后的氰酸酯树脂在低温液氧环境下应用的研究工作尚未深入开展。针对上述问题,本文采用了氰酸酯树脂为主体,通过引入不同改性组分的方式,制备了两种改性氰酸酯树脂体系及其CFRP,研究了其树脂结构组成与力学性能、液氧相容性、阻燃性等性能的关系,并分析CFRP界面失效机理。本文采用低粘度环氧树脂(EP)和高性能耐温塑料(PES-C)共增韧改性双酚A型氰酸酯树脂(CE),合成了改性CYEP氰酸酯树脂。研究结果表明,EP和PES-C能促进CE自聚反应,提高CE树脂的低温(-196℃)韧性,但是对CE树脂的热稳定性有一定影响。18wt%的EP和6wt%的PES-C共混合加入到CE中制备得到的CYEP matrix(CYEP6)兼具良好的低温韧性、工艺性、耐热性和粘接稳定性等综合性能。-196℃下,CYEP matrix的冲击韧性比纯CE树脂提高了近200%,而模量下降仅为约6%,其经过15次冷热循环交变(-196℃~50℃)后表面无裂纹。CYEP matrix经177℃/4h+200℃/2h固化后,单体转化率>95%,80℃树脂黏度仅为734 cp,并维持4h工艺黏度无明显变化。CYEP matrix粘接双马树脂基CFRP剪切试样,在空气中经200℃/1000h老化后,剪切强度保持率大于80%,然而CYEP matrix阻燃测试为V1级,需进一步改进阻燃性。本文自制了含苯醚键双马树脂(BMPB)和耐高温活性稀释剂(DABDGE)加入到CYEP matrix树脂,制备了具有阻燃性的改性氰酸酯树脂(CEBM)。实验结果表明,BMPB中加入5wt%的DABDGE后,体系的黏度明显降低,而IDT温度下降不足10%。7wt%的BMPB改性CYEP matrix,得到了阻燃性提和低温韧性均较优异的CEBM7(CEBM matrix)基体,但过多的BMPB加入体系的冲击韧性和工艺黏性变差。在-196℃下,CEBM matrix冲击韧性CYEP matrix树脂的提高了20%,30次冷热循环后冲击强度保持率大于85%。CEBM matrix的阻燃性达到V0级别,具有自熄性,其工艺黏性和贮存稳定性与CYEP matrix树脂相当。本文对合成的CYEP树脂和CEBM树脂的(液)氧相容性及失效机理进行分析。研究结果表明,BMPB的含量和环氧基团的含量是影响基体树脂与液氧相容性的关键因素,尤其是BMPB与CE共聚形成的氮双杂环结构对基体的(液)氧相容性提升有明显效果。BMPB的含量超过5wt%时,其氧增重的起始温度提高近40℃,IRS值下降到4%以下,相反,当环氧树脂含量超过15wt%,其IRS值急速增加;不同的基体树脂中,分散相粒子的微观形貌和氧增重量不受热氧老化过程影响,但是在液氧冲击过程中,相界面明显展示出氧不相容。CEBM matrix液氧连续浸泡30天后,基体力学强度保持率>80%。采用动态接触角测试和微滴脱粘法测试等方法对不同基体与碳纤维界面性能进行了评价。结果表明,基体树脂的低黏度和增大极性在有利于提高其与碳纤维浸润性。提高基体自身强度、增加纤维表面粗糙程度和浸润性,能提高基体与纤维的界面剪切强度(IFSS)和断裂韧性Gdc。在Tg±50℃成形温度范围内,成形温度温度每升高10℃,IFSS值提高约3%。基体树脂中DABDGE稀释剂的加入有利于基体和纤维的界面过渡层的形成,分散应力并阻止裂纹扩展,其中CEBM基体与纤维表面形成约200nm的界面过渡层。考察了两种基体碳纤维复合材料的宏观力学性能和液氧相容性。研究结果表明,CEBM matrix基复材具有优异的低温力学强度,层间剪切强度(ILSS)为102.5MPa(-196℃),轴向拉伸强度可达2602MPa(-196℃)。树脂中增韧材料的过多加入对复合材料的整体性能提高不明显。CEBM matrix基层合板试样经过40次冷热循环后,复材表面无明显的微裂纹产生。复合材料试样表面缺陷是影响其液氧浸泡失效的关键因素,其浸泡后的IRS值比无缺陷试样的IRS值大5倍。更多还原

【Abstract】 CFRPs are gradually used to manufacture the Cryogenic fuel(Liquid Oxygen,LOX)tank in the next generation reusable launch vehicles(RLV)for meeting the weight needs instead of metallic materials.CFRPs must have the good mechanical properties in cryogenic,good thermal ability,and excellent liquid oxygen compatibility.The traditional epoxy resins cannot be used in manufacturing CFRP LOX tank,due to the deficiency of chemical structure.Recently,c yanate ester resins(CE)namely triazine resins are used as the potential matrices for CFRP LOX tank,because of their high-temperature resistance,outstanding mechanical properties,good anti-oxidative capacity and process-ability.However,the CE resins need to be suitability modified,showing the excellent performance before se rving structural functions.The research works are focused on the failure mechanism of CE matrix/composite in the LOX environment.Hence,as concerned as above,two different modified CE resin systems and their CFRP composites were designed and prepared,and the relevant relations of chemical compositions and structures with properties of two resin systems were discussed.Low viscosity epoxy resin(EP)and thermoplastic(PES-C)was applied to modify CE resin,designing a novel modified CE resin system(CYEP)with a good ductility at-196℃.The results show that the ductile and adhesion property of CYEP resins are improved by the introduction of EP and PES-C into CE resins in cryogenic temperature.Exllecnt properties are obtained by co-adding 18 wt% EP and 6 wt% PES-C into the CE.Impact strength of CYEP matrix at-196℃ is increased by 200% than that of neat CE,and the modulus is only decreased by 6%,and there are no micro-crack on the surface of CYEP matrix sample by the 15 cryogenic-hot cycles(-196 ℃ ~50 ℃).The process-ability of neat CE can be optimized by the adding the EP/PES-C blends,and the conversion is near to perfection after cured at 177℃/4h+200℃/2h.The viscosity of CYEP matrix is 734 cp at 80℃ and maintain a constant after 4h at the same temperature.However,the flammability test value of CYEP matrix is only UL94 V1 grade and is not satisfied.A novel bismaleimide resin contained phenyl ether structure(BMPB)and novel active diluents(DABDGE)were added into the CYEP matrix,and a new CEBM resin systems were also prepared.The results show that the viscosity of BMPB resin is obviously decreased with adding 5wt% of DABDGE diluents into them and the temperature of IDT is decreased by 10%.The better flammability and ductile of CEBM resin namely CEBM matrix is obtained by the addition 7wt% of BMPB into the CYEP matrix,but the excessive contents of BMPB might result in the negative impact strength and process-ability.The impact strength of CEBM matrix is increased by 20% more than that of CYEP matrix at-196℃,and its retention rate of impact strength is lager than 80% through the 30 times cycle.The test value of flammability of CEBM matrix is V0 grade and it is of self-extinguish.The process-ability and storage stability of CEBM matrix is as well as that of CEYP matrix.In this thesis,the LOX compatibility and failure mechanism in LOX of prepared resin systems(CEBM and CYEP)were studied.The results show that the contents of BMPB and epoxy are the key factors for the LOX compatibility of resins,especially the structure of nitrogen bis-heterocyclic rings originated from the reaction of BMPB and CE can strongly improve the compatibility of matrix in LOX.When the content of BMPB is more than 5wt%,the temperature of oxidation weight gain is increased by 40℃,the value of IRS go down to 4%.On the contrary,when the content of epoxy group is more than 15wt%,the value of IRS is sharply increase.The morphologies and oxidation weight gain of spherical PES-C domainsare influenced by the course of hot oxygen age,interface between the PES-C phase and continuous resin phase usually show the incompatibility in LOX impact.As well as CEBM matrix,the retention of mechanical strength is more 90% than thatof initial value is almost no change by the relevant durability experiments with LOX environment for 30 days.Using dynamic contact angle test and micro-debond test,the micro properties of two phase interfaces between the composite materials and matrix were estimated.The results show that low viscosity of matrix and polar molecules are all positive to improve the wetting performance.the interfacial shear strength(IFSS)and interfacial fracture toughness(Gdc)can be enhanced by the three effective methods.As follows: first,improving the self-strength of matrix,secondly,increasing the surface roughness of carbon fiber,last,raising the bonding force between the matrix and fiber.The processing temperature of matrix with fiber is raising every 10℃,correspondingly,the IFSS value is increase by 3% in the range of Tg±50℃.The addition of DADBGE is advantageous for forming the interfacial transition layer between matrix and fiber,with utilizing AFM defection,where the width of transition layer is about 200 nm.The transition layer may disperse the stress concentration and inhibit the micro-cracks propagation,The mechanical properties and cryogenic-hot cycle resistance of different resin based CFRP are studied.The results show that the CEBM matrix /T700 composite isof the excellent mechanical strength both at room temperatur e and at-196℃.Specially,it is worth noting that the inter-laminar shear strength(ILSS)of CEBM matrix is 102.5MPa and the axial tensile strength is about 2602 MPa at-196℃.There are no any micro-cracks in the surface of CEBM matrix/T700 laminate by the 40 times cycles.The existence of default in the surface of CFRP CEBM matrix/T700 is fatal to the compatibility in LOX,accordingly the IRS value of it is more than 5 times that of no default samples increased.更多还原