Experimental study and numerical simulation on bonding performance of CFRP strengthened steel plate exposed to marine atmosphere

The bonding performance of CFRP-steel joints between carbon fiber reinforced polymer （CFRP） plate and steel is seriously affected by marine environment. In order to evaluate the bonding strength of CFRP-steel joints exposed to marine environment， a double-lap shear joint on five specinmens with different bonding lengths were corroded for 7 to 21 days in the NaCl solution. The technique of digital image correlation （DIC） was applied to measure the normal strain distribution on the surface of CFRP. Scanning electron microscope （SEM） and energy dispersive spectrometer （EDS） were used to observe microscopic information and monitor element content changes of CFRP surface. The results show that the contents of Na+ and Cl- on the CFRP surface are increased with the increase of corrosion period， which induces charge compensation. Electrolyte penetration into the interface leads to free volume expansion， resulting in a decrease in the interfacial binding strength. The adhesion failure at the interface of adhesive and CFRP is observed in the experiment. The corrosion is aggravated with the increase of time， leading to the decrease of the ultimate load and the ductility. The interface ductility decreases after corroding for 7 to 14 days and the strain softening disappears and exhibits characteristics of the brittle failure after corroding for 21 days. The finite element model was established based on the Fickian theory and bonding-slip constitutive parameters.The diffusion characteristics of seawater between bonding interfaces and the interface typeⅡ delamination process were simulated，and the numenical results are in good agreement with the expermental results.