Description
This literature review investigates the efficacy of toughened epoxy adhesives for structural repair and strengthening of existing structures with FRP composites. Highlighting the limitations of traditional epoxy adhesives, such as susceptibility to fatigue loading and impact actions, the study explores the potential of toughened formulations to mitigate fracture propagation issues. Through the incorporation of additional phases like rubber particles or nanomaterials, toughened adhesives offer increased fracture toughness and improved structural performance. However, this could also lead to trade-offs, including potential reductions in mechanical properties, glass transition temperature reduction and possible health and environmental concerns. This study presents an overview of the main toughening mechanisms occurring in modified epoxy resins. Two toughening techniques are described and discussed, namely the rubber-toughening and nanomaterial-toughening. The study further investigates the effects of the use of toughened adhesives in externally-bonded FRP strengthening/repair applications, involving both steel and concrete substrates. Eventually, the difference in bond-slip behavior of toughened and traditional adhesives is described, with reference to currently available literature studies on the topic. This review paper shed light on the promising advantages of using toughened epoxy adhesives in FRP applications, in terms of higher bond and strain capacity and enhanced bond transfer mechanisms between composite and substrate, if compared to traditional adhesives.
