This paper aims to investigate the relationship between local moisture concentration and mesoscale mechanical properties of epoxy adhesive under elevated temperature. Araldite® 2015 was chosen as the target adhesive due to its curing stability and possible validation with previously published literatures. The specimens were aged at 60 ^oC in deionised water and 5%wt NaCl solution, separately, with the water ingress evaluated by Fickian diffusion model. Nanoindentation was utilised to characterise the mesoscale modulus and hardness distribution along the water diffusion path. Then Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were conducted to investigate the variation of functional groups and microstructure, respectively. The results show that mechanical properties degrade as ageing duration increases, with higher degradation observed in the edge region where higher moisture concentration exists. Besides, higher ageing temperature leads to larger decrease in mechanical properties of saturated specimens. An empirical relation between local mechanical properties and moisture concentration was established. Chemical and morphology performance of adhesives also exhibited variations with hygrothermal ageing. The obtained local moisture-mechanical relationship can then be used to improve the accuracy of numerical simulation on the environmental durability of structural adhesive in future work.

本文旨在研究高温下环氧胶粘剂的局部水分含量与中尺度力​​学性能之间的关系。Araldite®2015之所以被选为目标粘合剂，是因为其固化稳定性和先前发表的文献中可能的证实。标本在60 ^o时效分别在去离子水和5％wt的NaCl溶液中吸收C，并通过Fickian扩散模型评估进水量。纳米压痕用于表征沿水扩散路径的中尺度模量和硬度分布。然后进行了傅里叶变换红外光谱（FTIR）和扫描电子显微镜（SEM），分别研究了官能团和微观结构的变化。结果表明，机械性能随着老化时间的增加而降低，在存在较高水分浓度的边缘区域观察到更高的降解。此外，较高的时效温度导致饱和试样的机械性能下降幅度更大。建立了局部机械性能与水分浓度之间的经验关系。粘合剂的化学和形态学性能也随着湿热老化而表现出变化。然后，在以后的工作中，所获得的局部水分-机械关系可以用来提高数值模拟对结构胶粘剂环境耐久性的准确性。