Experimental study, finite element numerical simulation and modified mathematical models for bonding relationship between ECC and CFRP strip

In this paper, twenty specimens were prepared for the double shear test in order to investigate the key parameters influencing the bonding behavior between externally bonded CFRP and ECC. The studied parameters included the bonding length, shear modulus of the adhesive layer, CFRP width and thickness, ECC tensile strength, and surface polishing treatment. A three-dimensional analytical model was developed using ABAQUS software, followed by a comprehensive parametric analysis. The results showed that ECC surface polishing significantly improved the bonding performance, and the thickness of the ECC attached to the peeled CFRP increased significantly. When the tensile strength of the ECC (3.0 MPa) is close to the bond strength of the adhesive layer (3.3 MPa), the ultimate load and ultimate slip of the specimen reach their maximum values. However, this phenomenon does not apply to all cases and is only valid when the CFRP thickness (>0.167 mm) and adhesive layer shear modulus (>450 MPa) are within a specific range. Increasing the CFRP thickness enhances the ultimate load, increases the effective bond length, and increases the thickness of the ECC layer adhering to the CFRP during peeling. In contrast, the shear modulus of the adhesive layer has the least influence on the bond relationship between ECC and CFRP. Finally, the prediction model of the ECC-CFRP bonding relationship was established through data regression analysis of finite element simulations. The model predictions showed good agreement with experimental values, The coefficient of determination (R²) is 0.926, and the coefficient of variation (CV) is 3.99 %. And this model is more accurate than the other current models.