A Comprehensive Study on Long-Term Durability of Protective Epoxy Coatings for Electrified Roadways

Underground wireless power transmission (WPT) systems are susceptible to environmental threats such as high temperatures, water ingress, and mechanical impact from above-ground objects. Typical WPT systems electronics are safeguarded with civil-grade epoxy coating, thus it is imperative to assess the coating's durability in these extreme conditions. Among various environmental threats, this study is primarily focused on both experimental and numerical investigations on long-term water diffusion characteristics of civil-grade epoxy materials at various temperatures. A series of water diffusion tests were performed on the specimens made from two commercially available electronics casting epoxy materials at room (23°C) and high (50°C) temperatures. A sequentially coupled, multi-physics finite element (FE) model was developed to predict water diffusion-induced hydrothermal and subsequent mechanical damage in the epoxy materials. The FE model consisted of four sequentially coupled analyses: (1) heat transfer analysis, (2) water diffusion analysis, (3) swelling analysis from long-term water diffusion, and (4) low velocity impact (LVI) analysis. The numerical results show good agreement with in-house experimental findings, indicating that the framework can serve as a baseline for predicting epoxy coating performance on WPT systems.