Glass transition evaluation of commercially available epoxy adhesives for strengthening of steel structures with bonded CFRP plates

In the current study, the glass transition and tensile behavior of three different cold-curing two-component epoxies, commercially available as structural adhesives for carbon fiber reinforced polymer (CFRP) strengthening of concrete and steel structures, has been investigated. A set of dynamic mechanical thermal analysis (DMTA) tests have been performed, through which the glass transition behavior of two high toughness epoxies, suitable for steel strengthening, was compared to a typical high stiffness adhesive for concrete applications. In addition to DMTA tests, a set of tensile tests was also performed on dogbone specimens to evaluate and compare the tensile mechanical behavior of the selected epoxy adhesives. Furthermore, the influence of two different curing scenarios (i.e., room temperature curing (RTC), and accelerated curing (AC) by heating) on the glass transition temperature as well as tensile mechanical properties of all the three epoxy adhesives was investigated. Based on the experimental results of the current study, certain recommendations are proposed to select a proper epoxy adhesive for strengthening of steel structures with bonded CFRP composites.