CFRP strengthened pre-cracked steel plates protected with chemical silane exposed to extreme marine environments

Carbon fibre reinforced polymers (CFRP) have been recently investigated to retrofit degrading steel structures. One application being to prevent crack growth in fatigue damaged steel. Unfortunately, despite having the ability to increase the fatigue life of steel, applications have limited studies under industrial conditioning such as elevated temperature and marine exposure. This paper evaluates the durability of adhered CFRP patches design to restrict crack propagation in steel. In particular focussing on the use of epoxy adhesives and silane chemical barriers to restrict environmental ingress and improve fatigue life. CFRP patched pre-cracked steel plates were experimentally tested with combinations of epoxy adhesives and chemical barriers. Samples experienced ongoing static service loading while submerged in 5% NaCl solutions of varying temperatures. After removal, samples were fatigue loaded until failure. Comparing exposed and unexposed samples quantified the impact environmental conditioning has on the fatigue life of CFRP strengthened steel plates. Three layers of CFRP sheeting successfully increased the fatigue life of all specimens, even after environmental exposure. All, except two, double side patched specimens witnessed a run out, suggesting mild levels of degradation caused during submergence. Araldite 420 consistently gave longer fatigue lives due to the ability of the adhesive to saturate fibres easily and consistently. Single sided repairs showed life extensions of 2.29 and 3.85 for Araldite 2014 and Araldite 420 controls tests respectively, with conditioned single sided specimens expected for testing in the coming months.