Experimental assessment of bonded FRP-to-steel interfaces

The use of bonded fibre-reinforced polymer (FRP) materials for the repair of civil infrastructure is becoming well established. The majority of applications are ‘bond critical'; that is, the dominate limit state is affected by the FRP debonding from the substrate. Considerable research has been conducted on the behaviour of FRP bonded to a concrete substrate; however, there is a growing interest in using FRP bonded to a steel substrate. In the former case, bond behaviour is dominated by cohesive failure in the concrete substrate; in the latter, bond is dominated by adhesive behaviour. As a result of not needing to consider substrate failure in the case of FRP-to-steel applications, the FRP may be utilised much more efficiently, provided bond can be maintained. This paper briefly reviews factors affecting bond of FRP-to-steel and presents a relatively simple laboratory test method for assessing bond performance. The method is well suited to comparing performance of different applications, surface preparations, environmental exposures and so on, but also yields quantitative data in the form of the steady-state energy release rate useful for modelling and designing FRP-to-steel bonded interfaces.