Prediction of long-term durability of FRP under seawater environment

Abstract

In recent years, applications of fiber-reinforced plastics (FRPs) to large marine structures are expected to improve their performances due to the high specific strength and stiffness and the corrosion resistance. However, the creep lifetime of FRPs in seawater environment has not been made clear so far. Objective of this study is to predict the creep lifetime of FRPs in seawater environment based on the accelerated test results and reveal the fracture mechanism. In this study, creep tests were carried out using the plain-woven GFRP and CFRP laminates under seawater environment and time-temperature superposition principle (TTSP) was used to predict the long-term creep rupture life. It was shown that the rupture time decreased with increase of the seawater temperature and the applied stress, and it was suggested that decrease of the strength was mainly caused by degradation of the interfacial shear strength between the fibers and the matrix. By using Larson-Miller parameter (LMP) as time-temperature parameter, the analytical results showed good agreement with the experimental results. For the GFRP laminates, behavior of the prediction curves varied in the lower applied stress because the glass fibers deteriorated in seawater. On the other hand, deterioration of carbon fibers was not observed in seawater so that the rupture time showed a consistent tendency to decrease for the CFRP laminates.