تاثیر رطوبت بر چسبندگی اتصالات فیبر های پلیمری تقویت شده Effect of moisture on the adhesion of CFRP-to-steel bonded joints using peel tests

1 Introduction Nowadays, composite materials are widely used for repair of metallic components in offshore, onshore, oil and gas industries. Adhesive bonding is the most efficient joining technology in terms of weight and performance to join these two materials. Therefore, composite-to-metal bonded joints are nowadays a common practice in such maritime industries. The effect of multimaterial bonding process on joint strength has been investigated by many researchers and found a positive influence on the performance of bonded structure [1–3]. However, limited research is found on the performance of such hybrid joints under the harsh maritime environments. One of the most critical aspects for the long-term durability of bonded joints is the adhesion at the interfaces. With the increasing use of composite-tometal bonded joints, attention should be paid on the adhesion quality in the presence of environmental effect to assure long-term durability of the multimaterial bonded joints. During service, metal structure can be exposed to extreme environmental condition, which impacts their performance. This can be especially severe in offshore and onshore unit, where the metal pipe is always in contact with the salt water [4, 5]. Several works were carried out to assess the influence of environmental parameters on the durability of bonded structures [5–9]. There are many studies carried out on the ageing effect, using the composite–composite bonded joints (mode I, mode II and mixed mode) and only very few carried out with the composite–metal bonded joints [10–14]. Most of the results found a detrimental effect of moisture on the performance of the bonded joints and show that moisture is one of the most problematic factors, when it comes to the durability of adhesive joints with FRP and metallic adherents [15–18]. Salt water immersion is one of the worst ageing conditions to affect the joint performance, because not only the adhesion is affected by the moisture but also the metal gets corrode easily. So, it is of prime importance to assess the interface adhesion between the metal–composite joint in the presence of different environmental conditions.