2024 Volume 50 Issue 4 Pages 120-126
Moisture absorption significantly affects the quality and strength of epoxy adhesives containing hardeners. These adhesives must be refrigerated to prevent curing reactions during storage, which leads to the inevitable water buildup. This study aims to elucidate the effect of moisture on the crack resistance of an epoxy adhesive and delineate the underlying mechanisms. The effectiveness of vacuum freeze-drying as a technique for reducing the moisture content of the adhesive was explored to assess its impact on improving adhesive toughness. Tests were conducted on carbon fiber reinforced plastic (CFRP) joints using adhesives with varying moisture contents to evaluate their toughness. The results showed that an increase in the moisture content of the adhesive resulted in weaker bonds and greater variability in its strength. Additionally, removing moisture via vacuum freeze-drying significantly enhanced the reliability of the adhesive. Furthermore, surface morphology analysis revealed that moisture primarily damages the adhesive itself rather than the adhesive-CFRP bond, leading to a shift in the failure mode from bond splitting to internal adhesive breaking.
