Subcritical Debonding Characterization of GFRP-Concrete Bonded Interface Using Modified Single Cantilever Beam Specimens

Abstract

Subcritical debonding of glass fiber reinforced polymer (GFRP)-concrete bonded interface in both the air (room environment) and water is characterized using the modified single cantilever beam specimens. A modified specimen design is uniquely proposed to overcome the potential large deformation of the GFRP substrate; i.e., a thin aluminum beam is glued to the top of GFRP strip to form a stiffer composite beam. A two-parametric elastic foundation model is employed to calculate the compliance and energy release rate (ERR) of the modified specimens, and it is then used to indirectly calculate the crack length, which is verified by the direct experimental strain measurements. Experimental programs using the modified specimens are conducted to characterize the subcritical debonding behavior of the GFRP-concrete bonded interface, and the effect of moisture condition on the subcritical debonding rate is evaluated. Meanwhile, the water-based epoxy primer promoting the interface bonding is explored. In particular, the relationship between the applied ERR and measured debonding growth rate is established. The test results demonstrate that the subcritical debonding growth occurs at slow loading rate and the failure mode shifts from the cohesive failure within concrete to the adhesive failure along the bonded interface. The subcritical debonding test method developed and the modified specimen proposed can better reveal the actual degradation mechanism of bimaterial bonded interface under different environments and loading rates.