Long-term exposure to moisture leads to a gradual deterioration of performance and reduced service life of glass fibre-reinforced epoxy resin (GFRP) material in composite insulators. Therefore, it is necessary to analyse the moisture absorption characteristics of GFRP material and the evolution of damage to their internal interface properties. Moisture absorption tests on GFRP rod material used in composite insulators to obtain their three-dimensional diffusion coefficients are conducted. Atomic force microscopy was then employed to obtain the composite material system's fibre/matrix interfacial phase parameters. Furthermore, a finite element model incorporating representative volume elements with interfacial phases and a mesoscale transient moisture absorption finite element model for the composite material was established. Finally, the moisture absorption characteristics of GFRP material and the evolution of damage to the interfacial phase under thermal-humidity cycling conditions were investigated. The results showed that the diffusion coefficient along the fibre direction in GFRP material was higher than that in the perpendicular direction. The moisture diffusion finite element model, incorporating an anisotropic interfacial phase, fitted the anisotropic diffusion coefficients of GFRP material more accurately. As moisture invaded the GFRP material, the mismatch stresses continuously increased during the moisture absorption. Moreover, the non-uniform arrangement of fibres resulted in uneven distribution of moisture-induced stresses inside the material, leading to higher mismatch stresses in areas with dense fibre arrangements in the matrix. Prolonged high and low humidity cycles led to the development of micro-cracks, micro-porosity, and interface debonding along the fibre direction at the GFRP material interfaces, thereby affecting the anisotropic moisture absorption characteristics of the material. The findings of this study provide valuable insights into the mechanisms underlying the deterioration of GFRP material in composite insulator rods due to moisture degradation.

中文翻译：

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基于3D-Fick模型的复合绝缘子用玻璃纤维增​​强环氧树脂材料吸湿特性研究

复合绝缘子中的玻璃纤维增​​强环氧树脂（GFRP）材料长期暴露在潮湿环境下，其性能会逐渐恶化，使用寿命也会缩短。因此，有必要分析GFRP材料的吸湿特性及其内部界面性能损伤的演变过程。对复合绝缘子用GFRP棒材进行吸湿试验，获取其三维扩散系数。然后采用原子力显微镜来获得复合材料系统的纤维/基体界面相参数。此外，建立了包含界面相的代表性体积单元的有限元模型和复合材料的介观瞬态吸湿有限元模型。最后，研究了GFRP材料的吸湿特性以及热湿循环条件下界面相损伤的演变过程。结果表明，GFRP材料沿纤维方向的扩散系数高于垂直方向的扩散系数。水分扩散有限元模型结合了各向异性界面相，更准确地拟合了 GFRP 材料的各向异性扩散系数。当湿气侵入GFRP材料时，失配应力在吸湿过程中不断增加。此外，纤维的不均匀排列导致材料内部湿气引起的应力分布不均匀，导致基体中纤维排列密集的区域产生更高的失配应力。长时间的高低湿度循环导致GFRP材料界面处沿纤维方向产生微裂纹、微孔隙和界面脱粘，从而影响材料的各向异性吸湿特性。这项研究的结果为了解复合绝缘子棒中 GFRP 材料因水分降解而劣化的机制提供了宝贵的见解。