【作者】 王春齐；

【导师】 江大志；

【作者基本信息】 国防科学技术大学 ， 材料科学与工程， 2012， 博士

【摘要】 本文采用实验测试和有限元数值分析相结合的方法，研究玻璃纤维增强环氧树脂复合材料（GF/CYD-128层合板）在深海环境中的吸湿行为，揭示复合材料在深海环境下的吸湿机理及吸湿对复合材料力学性能的影响规律；通过纤维界面处理和基体纳米填料改性提高复合材料本体耐湿性；通过在GF/CYD-128层合板表面构建超疏水表面层提高复合材料结构整体阻湿性。主要研究内容包括：聚合物基复合材料深海环境吸湿行为研究。设计并制备了圆柱形压力容器，内装海水并充入0-3.0MPa的高压氮气，模拟0-300米的深海环境。采用称量法表征复合材料的吸湿量，采用试件排水法表征复合材料吸湿溶胀率，研究GF/CYD-128层合板在深海环境中的吸湿规律。结果表明，复合材料在深海环境中吸湿量的变化规律符合Langmuir吸湿模型，采用该模型预测GF/CYD-128层合板在3.0MPa水压下的吸湿数据与实测数据吻合较好。深海环境吸湿对聚合物基复合材料力学性能影响研究。通过复合材料试样吸湿后力学性能的测试和表征，揭示吸湿后GF/CYD-128层合板力学性能的变化规律；采用有限元分析方法，分别建立了常规吸湿和界面优先吸湿细观力学分析模型，得到复合材料吸湿后的内应力分布，揭示复合材料吸湿破坏的细观机制。结果表明，界面优先吸湿细观力学分析模型的预测结果与实验结果较为吻合，表明界面脱粘是复合材料吸湿后破坏的主要控制模式。在深海环境吸湿后，GF/CYD-128层合板力学性能下降的主要原因是吸湿溶胀产生的内应力促使复合材料界面脱粘和基体开裂。复合材料界面吸湿改性研究。本文采用纤维表面处理方法，研究硅烷类偶联剂（RSiX3）表面处理对复合材料吸湿前后力学性能的影响规律。结果表明，采用预处理法比添加法的改性效果更好，与未经偶联剂处理的试件相比，KH550预处理使GF/CYD-128层合板的平均吸湿速率下降了31.8%，但对其饱和吸湿量基本没有影响；层间剪切强度提高了16.9%；在去离子水中浸泡79天后的层间剪切强度提高了10.3%；R基可与基体树脂反应的偶联剂其界面改性效果更好；水解后，X基团位阻较小的偶联剂其界面改性效果更明显。复合材料基体吸湿改性研究。提出了在基体中添加纳米颗粒的改性方法，进一步提高复合材料的耐湿性。通过对纳米SiO2填料改性树脂及其玻璃纤维增强复合材料吸湿前后的静态力学性能和疲劳性能测试，研究纳米填料改性对环氧树脂及其GF/CYD-128层合板耐湿性能的影响。结果表明，与饱和吸湿后未改性复合材料相比，纳米SiO2改性GF/CYD-128层合板饱和吸湿后的最大溶胀率降低了61.5%；饱和吸湿后，未改性GF/CYD-128层合板的弯曲强度比干态试样的下降了约15.3%，而纳米SiO2改性GF/CYD-128层合板的弯曲强度却上升了约5%；未改性GF/CYD-128层合板的短梁剪切强度比干态的下降了约31%，而纳米SiO2改性GF/CYD-128层合板的短梁剪切强度仅下降了约12%；与未改性试样相比，纳米SiO2改性复合材料试件的拉-拉疲劳寿命提高了142.8%。复合材料结构整体阻湿方法研究。提出了在聚合物基复合材料表面构建超疏水表面层的方法，提高复合材料结构的整体阻湿性。利用复合材料组元材料特性，设计了复合材料结构超疏水表面层的组元材料，通过化学刻蚀和表面修饰获得具有超疏水表面的纤维增强环氧树脂复合材料结构，对超疏水表面进行了微观结构表征，对具有超疏水表面的GF/CYD-128层合板的耐湿性进行了实验研究。结果表明，本文在GF/CYD-128层合板表面上制备的CaCO3/环氧树脂和ZnO/环氧树脂超疏水表面层的水滴接触角大于150°，且具有长期的室温稳定性和在10-80℃范围内的热稳定性，该超疏水表面能有效降低复合材料结构的吸湿速率和吸湿量。更多还原

【Abstract】 The paper focuses on the water absorption behaviors and failure mechanism ofglass fiber reinforced epoxy resin composites (GF/CYD-128) in deep-seawaterenvironment. Methods to improve mechanical properties of the composites immersed inthe deep-seawater environment were investigated. The methods are based onmodification of the inter-phase of fiber/matrix by using coupling agents, enhancedproperties of the matrix by using nano-particles and isolating moisture from thecomposite structures by forming a superhydrophobic surface layer on it. The mainresearch work is as follows:Experimental investigation on water absorption of the glass fiber reinforced epoxymatrix composites immersed in the deep-seawater environment was conducted. The0-300meters deep-seawater environment was simulated by using a self-madecylindrical pressure vessel filled with seawater and0.1-3.0MPa high-pressure nitrogengas. The moisture contents and saturated swelling of specimens of the GF/CYD-128composites immersed in the deep-seawater environment were obtained. Results showthat the Langmuir-model can be used to describe the water absorption behavior of theGF/CYD-128composites, and the predicted data with Langmuir-model were agreedwith the experimental data of GF/CYD-128under pressures of0.1-3MPa.Investigation on effects of water absorption on mechanical properties of thecomposites was conducted. Flexural strength, inter-laminate shear strength (ILSS) andfatigue life of the GF/CYD-128specimens with different contents of absorbed seawaterwere test. Finite element models for ordinary and interphase precession waterabsorption of fiber reinforced polymer matrix composites were developed and stressdistribution in the composites were obtained. Results show that the interface debondingwas a dominating mechanism for the failure of the composites absorbed water underexternal loadings. Degradation of the mechanical properties of the composites absorbedwater was due to the internal stresses induced by swelling of the composites afterabsorbed water which results in the interface debonding and matrix cracking of thecomposites.In order to improve the interface bonding property of the composite materialsduring water absorbed process, silicic-alkyl coupling agents of RSiX3were used tomodify the glass fiber/epoxy matrix interphase. Effects of treatment method andmolecular structures of the coupling agents on the moisture absorption behavior of thecomposite material were investigated. Results show that the fiber pretreatment with thecoupling agents was better than the mixing of the coupling agents with epoxy resin toimprove the mechanical properties of the composites. Comparing to the original composites, the rate of moisture absorption of the GF/CYD-128composites with fiberpretreatment of KH550coupling agents decreased31.8%, while the saturated water inthe composites has no significant changes. With fiber pretreatment of KH550couplingagents, ILSS of the dry and wet composites immersed in water for79days increased16.9%and10.3%, respectively. And the same effect can be benefit from more reactiveR-group and less resistance of X-group in the RSiX3.To improve moisture resistance of resin matrix in the composites the nano-SiO2particles were added into the resin matrix of the GF/CYD-128composites. The moistureabsorption and mechanical properties of GF/CYD-128composites were tested. Resultsshow that the maximum swelling rate of the GF/CYD-128with nano-SiO2modifieddecreased61.5%. Compared with dry specimens, the flexure strength of the saturatedunmodified GF/CYD-128decreased15.3%, while the saturated modified GF/CYD-128increased5%. The ILSS of the saturated unmodified GF/CYD-128decreased31%,while that of the saturated modified GF/CYD-128decreased only12%. Fatigue life ofthe nano-SiO2modified composites with saturated moisture under tension-tensioncycling loading was increased142.8%than that of the saturated unmodifiedGF/CYD-128.A method for protecting the whole composite structures from moistureenvironment was proposed and tested. The idea for the method is try to form an outersuperhydrophobic surface on the composite structures by isolating the moistureenvironment from contacting with the composite structures. Through material design forthe superhydrophobic surface layer, chemical etching, surface modification andparameter optimization, a superhydrophobic surface on the GF/CYD-128compositeswas successful fabricated. It was showed that the superhydrophobic surface layer ofCaCO3/CYD-128and ZnO/CYD-128with contact angle of larger than150°weresuccessfully formed by chemical etching with50wt%acetic acid and surface modifiedwith1wt%stearic acid. The prepared superhydrophobic surfaces have long-termstability at room temperature and thermal stability in rang of10to80℃. In addition, theprepared superhydrophobic surface can effectively reduce the hygroscopic rate andsaturated moisture content of GF/CYD-128composites in the moisture environment.更多还原