热氧环境下三向正交碳/玻纤维混杂结构隐身复合材料的损伤效应及机理研究

Carbon fiber/glass fiber hybrid bismaleimide composites (HBCs) possess not only excellent mechanical properties, but also high radar absorption when carbon fiber/glass fibers are properly configured or woven in HBCs. Therefore, HBCs have become a kind of typical structural absorbing composites which are expected to be used for stealth fighter manufacturing. However, the aging damage of HBCs caused by rather severe thermo-oxidative conditions during its service will directly affect the reliability and lifespan of fighter aircraft. Therefore, it is important and necessary to investigate the HBCs’ durability performances under thermo-oxidative conditions for the design and life predication of the composites. In this project, the changes in damage tolerance, interlaminar shear strength, flexural strength and electromagnetic property of the three-dimensionally orthogonal HBCs and the laminated HBCs are to be compared and studied. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), dynamic mechanical analysis (DMA), in-situ interfacial mechanics performance tester, three-dimensional super depth of field microscope system and digital ultrasonic flaw detector are to be employed to explore the thermo-oxidative aging mechanisms of HBCs and the strengthening and toughening mechanisms of the three-dimensionally orthogonal HBCs, as compared with the laminated HBCs. After a full understanding of the thermo-oxidative aging behavior and thermo-oxidative aging mechanism, the strength and life prediction models with high degrees of confidence for the three-dimensional orthogonal HBCs will be established based on the theory of stochastic processes.

碳/玻璃纤维混杂双马树脂复合材料（HBCs）不仅有优异的力学性能，还可以通过碳纤维和玻璃纤维的排布和编织，减少雷达波的反射，是一种典型的结构-隐身一体化复合材料，被期望用于隐形战机中。然而，HBCs长期暴露在恶劣高温有氧环境下的老化损伤会直接影响战机服役的可靠性与寿命。因此，研究HBCs在热氧环境下的老化行为，对于指导结构-隐身复合材料的设计及寿命预测具有重要的实际意义。本项目拟对比研究三向正交HBCs与层合HBCs在热氧环境下的损伤容限能力、层间剪切性能、弯曲性能和电磁性能的变化情况，并采用XPS、FTIR、FESEM、DMA、原位界面力学性能测试仪、超景深三维显微系统、数字型超声波探伤仪等分析手段揭示HBCs的热氧老化机理和三向正交结构相对于层合结构的增强增韧机理。在充分认识老化行为和老化机理的基础上，从随机过程理论出发建立三向正交HBCs在热氧环境下的高置信度强度和寿命预测模型。

碳/玻璃纤维树脂基复合材料是一种结构-隐身一体化材料，被用于隐形战机上，而热氧环境导致的树脂基体性能和界面性能的下降会影响战机的使用寿命。本项目旨在研究三向正交和层合碳/玻璃纤维双马树脂复合材料在200℃和250℃下老化不同时间的性能变化规律及机理。. 热氧老化会导致纤维/基体界面性能的不断下降。扫描电镜观测结果表明，纤维表面黏附的树脂量随着老化时间的延长而减少。横向纤维束拉伸试验结果表明，未老化试样的碳纤维/树脂基体界面强度高于玻璃纤维/树脂基体界面强度。老化后两者的界面强度都明显下降，且前者的界面强度小于后者。一方面，碳纤维与树脂基体的热膨胀系数相差更大，热氧老化过程中会在界面间产生更大的热应力，从而造成界面强度的急剧下降。另一方面，碳纤维表面的上浆剂在高温下易分解，会降低界面强度。. 热氧老化导致的树脂的降解和界面性能的下降共同作用造成了两种复合材料的力学性能下降，而三向正交复合材料的性能保留率都高于层合复合材料的性能保留率。层合复合材料在热氧老化过程中产生的裂纹会沿层间扩展，使其易发生分层破坏。然而，三向正交复合材料具有整体结构优势，能在树脂和界面性能严重退化的情况下使所有纤维成为一个整体来抵抗外力。. 热氧老化后材料的隐身性能变好。热氧老化过程中材料表面由于树脂基体的降解变得凹凸不平，增加了电磁波在表面的漫反射，减少了电磁波的反射。材料内部裂纹的扩展为电磁波在材料内部的传播提供了更多通路。因此，老化后试样的电磁性能优于未老化试样。.采用“改进型随机过程模型”对200℃下老化不同时间后的三向正交复合材料的所有弯曲强度数据进行了预测，预测误差均小于10%。证明了改模型的准确性。. 此研究为碳/玻璃纤维混杂隐身复合材料的结构设计和安全使用提供了理论依据。

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