Analysis of adhesive joints between fibre-reinforced polymer laminates and structural steel members

Over the past three decades, fibre-reinforced polymer (FRP) materials have gained a lot of attention in construction especially in the field of infrastructure. The attractiveness of FRP materials is mainly due to their superior mechanical properties such as high specific strength and stiffness, light weight and good fatigue and durability characteristics. The most common applications of FRP materials have been in strengthening and repair of existing structures. Using FRP composites for concrete strengthening and repair has been well researched and documented. However, when it comes to steel structures, the application of FRP materials is somewhat limited. One of the main reasons is the lack of accurate design models for adhesive joints between FRP and steel members. Issues such as the complexity of failure modes and the lack of knowledge of the force transfer mechanism are obstacles that contribute to the difficulty associated with developing accurate design models. This paper deals with analysis of adhesive joints used to bond carbon FRP laminates to steel substrates using a numerical and experimental approach. A numerical model of the studied joint configuration has been developed utilising the finite element method, while, an optic measurement technique has been used to experimentally verify the numerical results. Several classical failure criteria used for design of adhesive joints have been studied to examine their applicability and accuracy in predicting the failure load of the specimens. Different aspects of joint behaviour, such as strain distribution along the bond line and through the thickness of the adhesive layer and failure mechanisms are discussed and conclusions with regard to design of such joints are presented.