Influence of carbon fibre stiffness and adhesive ductility on CFRP-steel adhesive joints with short bond lengths

Abstract

The use of adhesively-bonded CFRP laminates is a promising technique to strengthen steel structures that have been deteriorated due to corrosion, ageing or increasing loads, as in the case of old metallic riveted bridges. But the relatively short available space between rivets requires the use of adhesively-bonded CFRP laminates with short bond lengths, which needs to be deeply studied as most previous research works have focused on large bond lengths. To study the bond behaviour between CFRP laminates and steel plates in such strengthened structures, a series of tests has been carried out in double-strap joints under tensile loading, evaluating the influence of CFRP stiffness and adhesive ductility on the strength and failure mode of short bond length adhesive joints. Based on the experimental results of the present work, together with a large database collected from literature, a fracture-mechanics model based on interfacial fracture energy in shear GII is calibrated, and a simple expression is developed to be used in design for the strength prediction of such adhesive joints. Finally, double-strap joint specimens are simulated using cohesive zone models (CZM) for the adhesive layers, and the results are compared to the analytical model and experimental tests.