碳纤维/环氧树脂单向复合材料的吸湿残余应力研究

Study on Residual Stresses Induced by Moisture Absorption in Unidirectional Carbon Fiber/Epoxy Resin Composites

对碳纤维增强环氧树脂基(CFL/EP)单向复合材料在湿热环境下吸湿残余应力进行了研究。首先,采用ABAQUS有限元软件计算了环境温度T=37℃及T=80℃条件下随时间变化的材料中水分分布,该结果和材料吸湿实验结果吻合较好,同时也发现碳纤维随机分布模型能更好地模拟复合材料吸湿行为;随后,根据获得的水分分布对随时间变化的吸湿残余应力进行了研究。结果表明:树脂基体长时间吸湿导致的残余应力能够达到很高的水平(30MPa以上),其中纤维间距较小的基体区域以及基体和纤维界面处的应力水平明显高于其他区域,而在界面处应力值最高。这种高水平的残余应力在吸湿、脱湿循环下可能导致材料发生疲劳损伤及失效。

The residual stresses induced by the moisture absorption in unidirectional carbon fiber reinforced epoxy composites （CFL/EP） were investigated. First, with the mass diffusion module of the ABAQUS package,the moisture absorption behavior of the CFL/EP was simulated both at 37 ℃ and 80℃ and the results coincided well with the experimental results. Also, the simulations showed that the random spaced fiber distribution model was better than the regularly spaced hexagonal model adopted in the simulations. Then, the residual stresses induced by the moisture absorption varying with time were calculated on the basis of the moisture distribution in the composites obtained through the simulations. The calculation results showed that the residual stresses induced by the absorption reached very high levels （30MPa and above）. The higher stresses developed especially at the locations between neighboring fibers of smaller space and the interfaces between the fibers and the matrix, in which, the stress value at the interfaces was the maximum. Those high level of residual stresses led to the composites fatigue damage and failure possibly during the cycles of moisture absorption and desorption.