Impact of sea-water on the quasi static and fatigue flexural properties of GFRP

Glass fiber reinforced plastic (GFRP) composite material is often utilized in marine applications for the construction of boats and ships. In this application it is a usual procedure to protect the material with a layer of gel-coat, but if the gel-coat breaks the material would be in direct contact with a humid environment. The main objective of this study was to understand the degradation that sea-water causes on GFRP mechanical properties. The article deals with two common resin systems in marine applications, i.e. polyester and vinylester, and reports the results of quasi-static and vibration tests at different sea-water exposure times, and fatigue tests in dry and wet environments of unexposed specimens and specimens aged in sea water for 22-weeks. The results show degradation of the material in terms of ultimate stress in the case of quasi-static loading, and no appreciable degradation on the fatigue loading case. Vibration tests demonstrated a stable flexural modulus during the water exposure period.