芳纶纤维复合材料的界面粘接强度表征与多尺度模型研究

Due to potential advantages in wave-transparent structures, advanced aramid fiber composites are widely used for secondary structure of aircrafts. One of the most significant issue is to improve the aramid fiber/resin interfacial adhesion strength. The fibrillation of the aramid fiber are found during the debonding process of the interface, which is different from the carbon fiber. Therefore, to develop appropriate techniques for the characterization interfacial adhesion strength is still urged. This work concentrates on the mechanical tests of aramid fiber bundle composites, including the tensile test of transverse fiber bundle composites (TFBC) and shear test of V-notched fiber bundle composites (VFBC).The fracture strength of fiber bundle composites can be obtained. And the fracture surfaces are examined by the scanning electron microscope (SEM). Afterwards, the macroscopic structural level for the TFB composite is discretized by the FE method using Abaqus/Standard. And the Generalized Method of Cells (GMC) is implemented as a special subroutine to calculate the micro stresses. The multi-scale model can capture the realistic mechanisms of the damage process. The model can be modified using the comparison result of both the experiment and analysis. The damage proportion of interfacial debonding and fiber fibrillation can be finally determined. These testing method and calculation process can be a basis for the accurate characterization of aramid fiber/resin interfacial bonding strength.

先进芳纶纤维复合材料广泛应用于飞行器次承力结构，具备实现结构/透波一体化的潜在优势。关键技术瓶颈之一是提高芳纶纤维与树脂的界面粘接强度。而芳纶纤维/树脂界面的破坏模式与碳纤维不同，容易发生原纤化现象，因此需要建立创新的界面粘接强度表征与分析方法。本项目针对芳纶纤维与环氧树脂，开展横向丝束复合材料（TFBC）拉伸试验和V型缺口丝束复合材料（VFBC）剪切实验研究，获取断裂强度与断口细观形貌信息；同时，构建真实试样的宏观有限元模型和芳纶纤维/界面/树脂的细观通用单胞（GMC）模型，实现多尺度协同分析并且反映真实破坏模式；最终通过预报分析结果与试验结果的综合对比，验证与修正分析模型，确定芳纶纤维/树脂界面粘接强度和原纤化破坏比例，建立芳纶纤维/树脂界面粘接强度表征的新方法。

先进芳纶纤维复合材料具备质轻、高强、可透波等优异特性，被广泛应用于航空航天飞行器的透波结构，实现了功能复合材料结构的轻量化，对于国家重大装备的结构/功能一体化具有重要意义。芳纶纤维复合材料的最关键材料技术瓶颈之一是芳纶纤维与树脂之间的界面结合较弱，其中芳纶纤维突出的皮芯结构和原纤化是最重要的原因，而这与碳纤维有本质的不同。现有界面表征方法多针对碳纤维，有必要发展出一套适用于评价芳纶纤维/树脂之间的界面损伤特性的表征方法。本研究采用了基于芳纶纤维束试样的表征方法，发展了国外近些年提出的横向丝束拉伸方法，首次提出了45°纤维丝束拉伸方法和双纤维丝束紧凑拉伸方法。三种方法分别用于表征芳纶纤维/树脂的界面粘接强度、界面剪切强度和界面韧性，分析了不同载荷条件下芳纶纤维界面失效模式，全面地表征了Kevlar-49,国产芳纶-3和国产芳纶-12等不同芳纶纤维的界面特性。并结合多尺度有限元损伤模型，考虑芳纶纤维特有皮芯结构以及纤维/树脂的界面相，预报了纤维丝束试样的宏细观协同损伤行为，根据宏观试样性能推演得到了细观界面损伤性能。本研究发展的芳纶纤维丝束表征方法，具有可靠、高效、便捷等优点，且测试结果能充分反映芳纶纤维界面损伤特性，具备在学术研究和工程制造方面的双重应用前景。