Krauklis, Andrey E.Andrey E.KrauklisStarkova, OlesjaOlesjaStarkovaGibhardt, DennisDennisGibhardtKalinka, GerhardGerhardKalinkaAouissi, Hani AmirHani AmirAouissiBurlakovs, JurisJurisBurlakovsSabalina, AlisaAlisaSabalinaFiedler, BodoBodoFiedler2023-10-052023-10-052023-08-29Composites Part C: Open Access 12: 100395 (2023)https://hdl.handle.net/11420/43562Epoxy R-Glass Fiber-Reinforced Polymer (GFRP) composite plates were hydrothermally aged at 60 °C for 23, 75, and 133 days. The water content reached 0.97 wt%, 1.45 wt% and 1.63 wt%, respectively. The studied GFRP matrix was inert to hydrolysis or chain scission, allowing for investigation of irreversible changes in the fiber-matrix interphase due to hydrothermal aging upon re-drying. During each period, a subset of the specimens was removed from the water bath and dried in a chamber. The weight loss upon drying was explained with epoxy leaching (impurities), sizing-rich interphase hydrolysis, glass fiber surface hydrolysis, accumulated degradation products escaping, and water changing state from bound to free. The influence of hydrothermal aging on the fiber-matrix interfacial properties was investigated. Lower interfacial strength of hydrothermally aged (wet) samples was attributed to plasticization of the epoxy, plasticization and degradation of the sizing-rich interphase (including formation of hydrolytic flaws), and hydrolytic degradation of the glass fiber surface. The kinetics of epoxy-compatible epoxysilane W2020 sizing-rich interphase hydrolysis provided an estimate of ca. 1.49%, 4.80%, and 8.49% of the total composite interphase degraded after 23, 75, and 133 days, respectively. At these conditions, the interface lost 39%, 48%, and 51% of its strength. Upon re-drying the specimens, a significant part of the interfacial strength was regained. Furthermore, an upward trend was observed, being 13%, 10% and 3% strength, respectively; thus, indicating a possibility of partial recovery of properties.en2666-68202023Elsevierhttps://creativecommons.org/licenses/by/4.0/DesorptionGFRPHydrothermal agingInterfacial strengthInterphaseWater diffusionChemical EngineeringJournal Article10.15480/882.867710.1016/j.jcomc.2023.10039510.15480/882.8677Journal Article