An efficient water-uptake-based prediction framework for long-term performance of seawater aged polymer-matrix composites

The mechanical properties of polymer-matrix composites may degrade during long-term seawater exposure, which is closely associated with water uptake and can affect structural durability. This study proposes a long‑term performance prediction framework for resin-matrix composites, considering the correlation between water uptake and strength degradation. A medium–high-temperature (MHT) cured epoxy resin (EP‑MHT) and carbon-fiber epoxy-matrix composite (CFRP‑MHT) were investigated under seawater immersion, to characterize the water uptake behavior and the evolution of their mechanical properties. A modular water uptake simulation method is proposed to rapidly predict water uptake behavior of the material, only depending on the volume fraction of different modules. Further, we propose a simple formula linking strength retention and water uptake by defining a normalized water uptake parameter, which is verified by experimental results with relative error less than 1.5 %. The long-term performance predictions for CFRP-MHT agree well with those obtained using the Arrhenius model, with relative errors below 1.5 %. This framework provides a prediction strategy for long-term performance with a short test period and reduced experimental workload, and is particularly efficient for low‑temperature seawater environments.