航空用国产碳纤维/双马树脂复合材料湿热特性

Hygrothermal property of domestic carbon fiber/bismaleimide resin composites for aeronautic application

针对1种航空用国产T700级碳纤维和4种双马树脂(QY9611、5429、QY9512、QY8911-4),采用3种湿热条件(100℃水煮、70℃水浸、70℃/85%相对湿度)对其复合材料单向层板进行湿热处理,通过研究吸湿量、扩散系数、显微结构、化学成分、耐热温度及力学性能,分析了复合材料的湿热特性。结果表明,4种复合材料在3种湿热条件下的吸湿行为均符合Fick第二扩散定律,100℃水煮时平衡吸湿量和扩散系数最大,70℃/85%相对湿度时两者最小。4种复合材料吸湿速度有明显区别,这与其原材料形式和成型工艺不同有关。湿热处理未导致复合材料内部产生损伤和化学变化,主要引起增塑效应,导致玻璃化转变温度降低。复合材料的90°拉伸性能测试结果表明,高温和吸湿耦合作用下复合材料力学性能衰减更为明显,破坏模式由基体开裂转变为界面脱黏和开裂。

For a kind of domestic T700-grade carbon fiber and four types of bismaleimide resin(QY9611,5429,QY9512,QY8911-4)used in aeronautic field,three hydrothermal conditions,including100℃boiling water,70℃water immersion and 70℃/85%relative humidity,were adopted to treat these unidirectional composite laminates.Moisture absorption content,diffusion coefficient,microstructure,chemical groups,resistance to temperature and mechanical property were studied to evaluate hydrothermal property of composite.The results show that the moisture absorption of the four types of composites under the three conditions all follows Fick’s second law.Moisture equilibrium content and diffusion coefficient are the largest under boiling water condition,while they are the least under the condition of 70℃/85%relative humidity.Obvious differences on the speeds of moisture absorption among the four bismaleimide composites have the relationship with material type and molding method.Hydrothermal treatment does not result in damage inside composite and chemical change,and the resulting plasticization effect results in decrease in glass transition temperature.The test results of 90°tensile properties of the composites show that the coupling of elevated temperature and moisture absorption causes more serious degradation in composite’s mechanical property,and its failure mode transforms from matrix cracking to debonding and fracture at interface region.