Characterization of material degradation mechanism of carbon fiber reinforced epoxy resin composites under ultraviolet radiation and salt-fog synergistic environment

The influence of harsh environment conditions on carbon fiber reinforced polymer composites (CFRP) restricts their popularization and usage in outdoor marine applications. Although many studies have been conducted on the service characteristics of CFRP under different conditions, the effect of ultraviolet (UV) radiation and salt-fog synergistic aging has not been researched in detail. The primary focus of this work is to understand the aging degradation mechanism and mechanical response of CFRP in this harsh environment. The test samples were exposed to UV and salt-fog synergistic environment. Then the physicochemical properties, dynamic/static mechanical behavior of all samples were characterized. The results show that the CFRP exposed to UV and salt-fog environment represent noticeable synergistic aging effects. The matrix plasticization and particle washing caused by UV radiation and water condensation will intensify the erosion effect of chloride ions, thus leading to significant deterioration of the fiber-matrix interface and interlaminar bonding. After aging, the deformation resistance of the material reduces, the molecular chain movement intensifies, the cross-linking density of the resin matrix decreases, and the maximum decline of glass transition temperature reaches 32.36%. Compared with the tensile performance, the degradation of interlaminar shear performance is more serious, of which the interlaminar shear performance are mainly determined by the matrix and interlaminar properties. Besides, for the aged samples, more serious irreversible deformation appears during the loading process. Highlights: The CFRP shows noticeable synergistic aging effects under UV and salt-fog aging, which the matrix plasticization and particle washing caused by ultraviolet radiation and water condensation will intensify the erosion effect of chloride ions. The decrease of the cross-linking density of CFRP materials is the primary cause for the deformation resistance reduction and properties degradation. Compared with the tensile performance, the degradation of interlaminar shear performance is more serious.