Durability of steel-CFRP structural adhesive joints with polyurethane adhesives

The use of reinforcing materials in steel structures is very widespread today because this combination is capable of bringing great improvements to this type of structures. In this work, a steel-CFRP (carbon fiber reinforced polymer) adhesive joint is proposed, trying to combine the good properties of both materials. Two structural polyurethane adhesives, one conventional and another hybrid, are selected to develop the joint due to the good properties of this material against external environmental agents and the high loads that are capable of resisting. The objective is to verify the suitability of this type of joints for structural applications in aggressive environments. For this purpose shear tests are carried out on specimens subjected to different exposure times in an aggressive environment, evaluating how their mechanical properties vary. Reliability studies are developed using a simplified model of the Weibull distribution, obtaining the distribution of failures of the joints. Microscopy techniques (Scanning Electron Microscope and optical microscope) are used to evaluate the failures of the studied specimens. The reliability of the joints under extreme aggressive conditions is verified in the results. Even having different behavior in the adhesives, both of them are able to maintain adequate strength after the degradation process.