Mechanical performances of GFRP-steel specimens bonded with different epoxy adhesives, before and after the aging treatments

In this paper, the stiffness increase obtained by coupling steel laminates to GFRP pultruded profiles is investigated, three different epoxy adhesives were used and compared. The objective is to verify the applicability of this hybrid system in structural members for curtain walls. Three types of test were used to investigate different properties of the system: shear tests on GFRP-steel single lap joints to verify the compatibility of the bonding system; puncture tests on GFRP-steel squared tubular short profiles to evaluate the response to localized stresses; three-point bending tests on GFRP-steel squared tubular long profiles to study the resistance to flexural loads. The effects of two environmental aging, continuous condensation and UV radiations, were also analyzed. The results demonstrated the compatibility of the bonding system and the stiffness increase of GFRP profiles when the steel reinforcements are applied. The experiments also show a good agreement with analytical models of the tests, confirming the advantageous method of hybridization. With regard to artificial aging, the continuous condensation produces the worst effects on the specimens, while better results were observed after the UV radiations. The results are discussed in details in the paper.