Tensile and Compressive Test on Thickness-Reduced Steel Plate Repaired by CFRP Strand Sheet and Underwater Epoxy with Bond Defects

There are a significant number of marine steel structures suffering severe corrosion damage, and they are seriously in need of repair or strengthening to prevent structural failure. This study is focused on a repair technique using carbon fiber reinforced polymer (CFRP) sheet, especially, CFRP sheet bonding in the underwater environment. Underwater bonding of CFRP sheets is not yet a matured technique, and its repair performance for corroded steel structures is not fully understood. One of the issues is the effect of bond defects on the repair performance. Air bubbles are often found to be trapped in the adhesive layer. To examine an effect of bond defects on the repair performance, uniaxial loading tests are
performed on thickness-reduced steel plates with CFRP strand sheets bonded by using underwater epoxy as adhesive. In total, sixteen CFRP strand sheet bonded steel plates are prepared, where test parameters are loading directions of tension and compression and the location of bond defects. The effect of bond defects on the repaired performance is examined in terms of yield strength, initial stiffness, and failure mode. As a result of experiment, it is found that two types of defects considered in this study do not affect repair performance significantly. However, when a CFRP bonded steel plate is under compression, buckling of CFRP strand sheet may control its compression strength, resulting in a smaller strength than the tensile strength.