Prediction of moisture diffusion kinetics during cyclic hygrothermal aging of epoxy resin by an improved finite element modeling approach

Epoxy resins, frequently employed in composite structures in industries like water transport systems, are known for their superior mechanical properties and resistance to chemical degradation. However, their long-term durability and performance are considerably affected by their ability to absorb water under cyclic hygrothermal conditions, resulting in the severe material degradation. Herein, this work aims to elucidate the moisture diffusion mechanisms within an epoxy resin subjected to extreme environmental conditions by incorporating both experimental investigations and Finite Element Modeling (FEM). Experimentally, epoxy resin samples were subjected to two complete cycles of moisture absorption and desorption in a controlled Temperature Humidity Test Chamber. Continuous gravimetric measurements were recorded every 24 h, revealing a transition from complex Dual-Fickian behavior in the initial absorption cycle to typical Fickian behavior in subsequent resorption cycles. To validate these findings, numerical simulations using FEM Analysis were conducted. The results demonstrated the importance of finer meshes, particularly in the initial Dual-Fickian absorption stage, to significantly improve the fidelity of the model to experimental data. Eventually, this study highlights the need for advanced modeling approach to effectively predict moisture diffusion kinetics in epoxy resins, thereby ensuring their long-term durability in industrial applications.