The aim of this work is to investigate the effects of wet/dry aging cycles on flax/epoxy composite properties for long-term structural applications. The mechanical performance of flax/epoxy exposed to wet/dry cycles during 104 days was evaluated. The physicochemical changes induced by wet/dry cycles were also studied. Unaged and cyclic aged samples were characterized by tensile test, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The tensile test results showed good aging performance of this composite. FTIR chemical investigation revealed the disappearance of the characteristic peaks of the cyanoethylation treatment at the fiber/matrix interface during cyclic aging. TGA data showed an improvement in thermal properties of the composite after the hydrolysis of cyanoethyl group, as well as the increase of the crystallinity index, as measured from XRD during cyclic wet/dry aging. This explains the limitation of mechanical degradation of this composite despite the severe wetting-drying cycles aging conditions. The results also show the positive effects of the cyanoethylation fiber treatment on the long-term durability of flax/epoxy composite.

这项工作的目的是研究湿/干老化周期对亚麻/环氧复合材料性能的长期影响。评估了亚麻/环氧树脂在104天内暴露于干/湿循环的机械性能。还研究了由干/湿循环引起的理化变化。通过拉伸试验，X射线衍射（XRD），傅立叶变换红外光谱（FTIR）和热重分析（TGA）对未老化和循环老化的样品进行表征。拉伸试验结果表明该复合材料具有良好的老化性能。FTIR化学研究表明，在循环老化过程中，在纤维/基质界面处的氰基乙基化处理的特征峰消失了。TGA数据显示，氰基乙基水解后，复合材料的热性能有所改善，以及通过循环湿/干老化过程中的XRD测得的结晶度指数的增加。这解释了尽管经历了严酷的干湿循环老化条件，该复合材料机械降解的局限性。结果还表明，氰乙基化纤维处理对亚麻/环氧树脂复合材料的长期耐久性具有积极作用。