【作者】 于祺；

【导师】 陈平；

【作者基本信息】 大连理工大学 ， 高分子材料， 2011， 博士

【摘要】 碳纤维增强双马来酰亚胺树脂基复合材料以其良好的耐高温、耐辐射、耐湿热、热膨胀系数小以及优异的工艺性等一系列优良特性,正在逐步代替传统的碳纤维／环氧树脂复合材料成为新一代航天器的结构用材,在航天领域得到迅速的发展和广泛的应用。空间环境因素对在轨航天器的正常运行和可靠性有着十分重要的影响,是导致航天器结构材料尤其是树脂基复合材料性能退化的主要原因之一。空间环境因素主要包括：高真空、热循环、带电粒子辐照、真空紫外辐照、原子氧及空间碎片等环境因素。各种空间环境因素对航天器材料的影响各不相同,它们不仅能够引起航天器材料性能的变化,决定着航天器材料的损伤与失效机制,甚至对航天器在轨运行的安全与寿命造成严重威胁。基于此,本文通过地面模拟试验装置模拟空间环境因素真空热循环、质子辐照和电子辐照,研究了CF/BMI复合材料在不同空间环境因素作用下的性能演化及其损伤机理。预期研究成果将为CF/BMI复合材料在新型长寿命航天器结构中的应用以及对其在空间环境下的服役性能和服役寿命的评估和预测研究提供必要的理论依据。利用真空热循环试验装置模拟空间环境中的高真空和冷热交替环境对CF/BMI复合材料进行处理,采用动态力学分析(DMA)、热重分析(TGA)、热膨胀分析、质损率测试、原子力显微镜(AFM)和力学性能测试等分析方法研究了真空热循环次数对CF/BMI复合材料性能的影响。结果表明真空热循环能够使树脂基体的交联度和热稳定性得到一定程度的提高,并引发树脂基体的放气行为以及循环热应力,导致复合材料的质量损失和界面脱粘破坏。横向拉伸强度主要受到基体放气效应和界面脱粘效应的联合影响,下降幅度约为9%；弯曲强度和层间剪切强度的变化主要受到树脂基体的固化交联和界面脱粘之间竞争效应的影响,呈现出先升高后降低的变化趋势,并于198次热循环后趋于稳定；质损率在95次循环后趋于稳定值0.35%。利用有限元分析方法模拟热循环过程中CF/BMI复合材料的热应力分布规律,采用抛物线屈服准则分析真空热循环过程中复合材料的潜在破坏区域,并结合生死单元分析方法揭示复合材料在热应力作用下的微裂纹分布情况。结果表明复合材料自由端处的热应力要大于其内部区域,其中在自由端处应力集中的区域位于沿纤维表面,能够引发自由端处纤维与树脂基体间的界面形成微裂纹从而导致界面脱粘破坏,进而使热应力在进一步的热循环作用下得到一定程度的缓解并重新分布。重新分布的热应力逐步由复合材料自由端向内部区域延伸,有可能导致微裂纹的进一步扩展而使界面脱粘程度加重。利用空间综合辐照模拟器分别模拟170 keV的质子辐照和电子辐照环境对CF/BMI复合材料进行处理,分别采用傅里叶变换红外衰减全反射光谱(ATR-FTIR)、X射线光电子能谱(XPS)、原子力显微镜(AFM)、DMA、TGA、力学性能和质量损失测试等方法系统地研究了不同束流量的质子辐照和电子辐照对CF/BMI复合材料表面性能、热性能、力学性能和质损率的影响及其损伤机理。研究结果表明质子辐照能够引发材料表面层化学键的断裂和碳化,并在注入材料的过程中参与化学反应生成新键,导致材料表面分子结构和化学成分的改变,并最终导致材料热性能和力学性能的退化。电子辐照能够引发CF/BMI复合材料表面同时发生辐照交联和辐照降解反应,哪一种作用占主导地位主要依赖于电子辐照束流量的大小。尽管电子的辐照交联作用能够使复合材料的性能得到一定程度的改善,但是随着辐照束流量的持续增加,电子的辐照降解将最终成为导致材料性能退化的决定因素。由于电子在材料中的射程要远大于质子,因此电子辐照与质子辐照对材料表面的损伤形式不同。更多还原

【Abstract】 Carbon fiber reinforced bismaleimide composites are gradually taking place of epoxy resin based composites as ideal candidates for construction materials in aerospace applications on account of their excellent performance such as high temperature resistance, radiation .resistance, humidity resistance, low coefficient of thermal expansion, good processing performance, etc.. However, space environment which has a very impartant impact on the safe operation and reliability of in-orbit spacecraft, is one of the main reasons for performance degradation of materials especially polymer matrix composite materials used in the structure of spacecraft. The space environment constituents consist of high vacuum, thermal cycles, charged particles irradiation, ultraviolet radiation, atomic oxygen and man-made debris. Exposure of polymer matrix composites to individual constituents of space environment may result in different detrimental effets via modification of their properties, and determine the damage and failure mechanism of structural materials, even pose a serious threat to the safety and life of in-orbit spacecraft. Therefore, in this article, the ground simulation facilities were used to simulate the space environment constituents including vacuum thermal cycling, proton irradiation and electron irradiation. The properties evolution and its damage mechanisms of CF/BMI composite exposed to different space environment constituents were investigated. The anticipated results will provide a necessary theoretical basis for the application of CF/BMI composite in new long life spacecraft and the evaluation and forecast for its service performance and service life in space environment.The vacuum thermal cycling machine was used to simulate high vacuum and thermal cycling in space environment and the CF/BMI composite was treated. The effets of different thermal cycles on properties of CF/BMI composite were studied by DMA, TGA, thermal expansion analysis, mass loss test, AFM and mechanical tests. The results indicated that the vacuum thermal cycling could improve the crosslinking degree and the thermal stability of resin matrix to a certain extent, and induce matrix outgassing and cyclic thermal stress, thereby leading to the mass loss and the interfacial debonding in the composite. The transverse tensile strength fell by approximately 9%, which was caused by joint effects of the matrix outgassing and the interfacial debonding, while the changes in flexural strength and ILSS were affected by a competing effect between the crosslinking degree of resin matrix and the fiber-matrix debonding, increasing firstly and then falling back to a plateau value after 198 cycles. The mass loss ratio rose to a plateau value of 0.35% after 95 thermal cycles. Finite element analysis was used to analyze thermal stress distribution in CF/BMI composite during thermal cycles. Parabolic failure criterion was used to predict the potential failure zone of the composite, and the birth and death element technique was used to analyze the micro-cracking distribution in composite induced by thermal stress. The results indicated that the thermal stress at composite free end zone which was induced by thermal cycles was higher than that in composite inner zone, and the thermal stress concentration at composite free end zone was located at fiber surface. Thermal stress at composite free end zone caused micro-cracking between fiber and the matrix, thereby leading to the interfacial debonding. As thermal cycles further increased, the thermal stress at composite free end zone was alleviated to some extent and redistributed, and gradually progressed from free end zone to inner zone, which could lead to the increasing degree of interfacial debonding.The space combined irradiation simulator was used to simulate 170 keV proton irradiation and 170 keV electron irradiation, respectively. The ATR-FTIR, XPS, AFM, DMA, TGA, mechanical and mass loss tests were conducted to investigate the effets of different fluence of proton and electron irradiation on the surface properties, thermal properties, mechanical properties and mass loss ratio of CF/BMI composite and their damage mechanisms. The results indicated that the proton irradiation could induce the breakage of chemical bonds and the carbonification in surface layer as well as the formation of new chemical bonds by introducing H+, which result in the changes in molecular structure and chemical composition at composite surface, thereby eventually leading to the degradation in thermal and mechanical properties of the composite. The electron irradiation could induce degradation and cross-linking process in the surface layer of the composite depending on the fluence of electron irradiation. Although the properties of the composite can be improved to a certain extent by cross-linking effect induced by electron irradiation, however, the properties degradation of the composite were eventually determined by a degradation process only at higher fluence of electron irradiation. Because the range of electrons into the materials is deeper than protons, the damage modes occurring in the surface layer of the composite are different between the electron irradiation and the proton irradiation.更多还原