【作者】 程群峰；

【导师】 方征平； 益小苏；

【作者基本信息】 浙江大学 ， 高分子化学与物理， 2007， 博士

【摘要】 双马来酰亚胺树脂(Bismaleimide,BMI)具有良好的的流动性和可模塑性,以及良好的耐高温、耐湿热等优良特性,在很多领域得到了迅速发展和应用。但是,BMI抗冲击损伤能力较差、冲击后压缩强度低,限制了以其为基体的复合材料层合板在飞机的主承力结构件上的应用。为了改善BMI树脂基复合材料的抗冲击损伤能力,传统的增韧方法是在树脂基体中引入增韧剂形成两相结构,提高树脂基体的韧性,达到增韧复合材料的目的。但是这种做法增加了树脂基体的粘度,改变了树脂基体的固化工艺;同时树脂基体韧性虽可以大幅度提高,但是复合材料的韧性提高幅度较小。鉴于这种情况,Aemrican Cyanamid公司提出了Interleaf层间增韧技术。Interleaf增韧方法针对复合材料薄弱的层间实施有目的的选择性增韧。。Interleaf增韧效果明显,但由于Interleaf增韧树脂的刚度和强度比较低,在保证复合材料的设计强度要求下,需要增加额外的纤维层,从而导致复合材料的减重效果大大降低。针对以上情况,本文将离位增韧技术应用到BMI树脂基复合材料中。复合材料的制备工艺包括预浸料/热压罐工艺和树脂传递模塑(resin transfer molding,RTM)工艺。离位(Ex-situ)增韧思想是益小苏教授在2001年申请国家973项目时提出的。离位思想的基本原理是:区分原有过程中的各个物理、化学过程,从结构、功能等方面将原来统一的过程分解为若干小问题,分别加以解决。具体来讲就是从热固性树脂相、热塑性树脂相两种纯组分相的叠层结构开始,利用固化反应诱导相分离,通过相反转,形成热塑/热固双连续相的层状结构。其中热固性单相部分保持复合材料原有的静态力学性能和湿/热性能,而热塑/热固双连续相则用来提高复合材料层间分层阻抗和损伤容限。目前,离位增韧技术在环氧预浸料复合材料中得到成功的应用。本文将离位增韧技术引入到BMI树脂基复合材料的增韧中去,其中BMI树脂基复合材料的制备工艺包括预浸料/热压罐工艺和RTM工艺。首先分别研究了用于预浸料/热压罐工艺和RTM工艺的BMI树脂体系的固化动力学,绘制出了表征BMI树脂固化工艺特性的时间-温度-转变图(Time-Temperature-Transformation diagram)。其次,针对离位增韧中增韧剂与BMI树脂之间的相分离行为,研究了增韧剂与BMI树脂的反应诱导相分离机理、相形貌演化和力学性能。利用离位增韧技术增韧预浸料/热压罐工艺BMI树脂基复合材料,使得BMI树脂基复合材料的冲击后压缩强度提高近61%,同时复合材料的静态力学性能保持良好。为了验证离位增韧技术的普适性,将离位增韧技术应用于RTM工艺BMI树脂基复合材料中。实验结果表明,RTM工艺BMI树脂基复合材料经过离位增韧后,Ⅰ型断裂能释放率从增韧前的210J/m~2,提高到增韧后的627J/m~2,提高了近1倍:Ⅱ型断裂能释放率由增韧前的510J/m~2提高到971J/m~2,提高了近1倍。而RTM工艺BMI树脂基复合材料的冲击后压缩强度,由原来的155MPa提高到277MPa,同时复合材料的静态力学性能保持良好,并且离位增韧技术对BMI树脂基复合材料的RTM制备工艺没有影响。。本论文进一步对离位增韧RTM工艺BMI树脂基复合材料的力学性能进行了系统研究,其中包括复合材料在低温环境、高温环境、湿热环境等不同环境下的力学性能。发现离位增韧后,室温干态条件下RTM工艺BMI树脂基复合材料的静态力学性能有所提高:-55℃干态条件下,RTM工艺BMI树脂基复合材料的静态力学性能基本保持在室温干态水平,没有发生大幅的降低。另外,RTM工艺BMI树脂基复合材料的开孔拉伸性能经过离位增韧后有所提高。通过对离位增韧RTM工艺BMI树脂基复合材料静态力学性能的系统研究,得出离位增韧技术在大幅度提高复合材料韧性的同时,并不影响复合材料原来的静态力学性能,某些性能还有小幅度的提高,这为离位增韧技术的工程化应用提供了重要的参考意义。更多还原

【Abstract】 Bismaleimdes(BMIs)with distinguished processing characteristics,excellent heat resistance and hot/wet properties is developed quickly and applied in many fields. However,the application of graphite laminates based on BMI matrix in the primary structure has been limited to some degree by their poor damage resistance and the reduction in compression strength after impact(CAI).A traditional method to improve the toughness of composites is to incorporate toughener component into the matrix system to form a two-phase structure.Unfortunately,many problems such as the low efficiency of toughening,the changing original process of matrix resin are followed by this method.According to the problems of composites,the interlaminar toughening technology-interleaf-is proposed by American Cyanamid company.The concept of interleaved composites is selectively toughening the interlaminar region of composites and the efficiency shows perfect.However,the major disadvantage of interleaved composites is a weight penalty.The tough layers of resin have low stiffness and strength which proportionately reduce the stiffness and strength of the laminate,requiring additional plies to maintain design properties.To this question,the Ex-situ concept is firstly proposed by Prof.Xiaosu Yi in national 973 program application in 2001.The principle of Ex-situ concept is to distinguish all kinds of physical and chemical process and break up the unitive process into some little issues based on structure and functions and solve them respectively.Further explanation is to start from the laminated structure of thermoplastic(TP)/thermosetting(TS)resin and the TP/TS co-continuous phase structure is formed by phase decomposition and phase inversion induced by curing reaction.The basic static mechanical properties and hot/wet properties of composites are kept by single thermosetting phase and the impact resistance and damage tolerance of composites is improved by the TP/TS co-continuous phase structure.The Ex-situ toughening technique has been successfully applied in prepreg/autoclave composites based on epoxy matrix. In this dissertation,The Ex-situ toughening technique will be introduced into composites based on BMI matrix,including prepreg/autoclave and resin transfer molding process.Firstly,the cure kinetics of BMI resin system suitable for autoclave and RTM process was investigated respectively,then the time-temperature-transformation diagrams were built,which standed for the characteristics of curing process.Secondly,the phase separation mechanism,phase evolution and mechanical properties of toughener/BMI diphase system were investigated to prepare for toughening composite with Ex-situ technique.The Ex-situ toughening technique was applied to toughen the T700/BMI composites manufactured with prepreg/autoclave process.The CAI(compression after impact)strength was improved by 61%,and the static mechanical properties of T700/BMI composites were well kept.The Ex-situ toughening technique was also transferred to RTM process to further validate the applicability of Ex-situ toughening technique.The experimental results showed that the process of RTM was not influenced by Ex-situ toughening technique. The ModeⅠfracture toughness of composites toughened with Ex-situ technique was improved from the 215J/m~2 to 627J/m~2,nearly two times improvement.The ModeⅡfracture toughness of composites toughened with Ex-situ technique was improved from 510J/m~2 to 905J/m~2,nearly one times improvement.The CAI strength increased from 155MPa to 277MPa,nealy 80%improvement.The basic static mechanical properties of composites were well kept,Finally,the mechanical properties of RTM composites toughened with Ex-situ technique was systemically investigatied,including the cryogenic temperature,high temperature and hot/wet properties.The experimental results showed that the mechanical properties of composites toughened with Ex-situ technique were well kept. Some properties such as open hole tension,open hole compression were significantly improved.更多还原