Effect of moderately elevated temperatures on bond behaviour of CFRP-to-steel bonded joints using different adhesives

The bond behaviour of CFRP-to-steel bonded joint considerably depends on the properties of adhesives, and is significantly influenced by temperature. Meanwhile, different adhesives behave differently at elevated temperatures. Therefore, an in-depth understanding of the effect of temperature on CFRP-to-steel bonded joints with different adhesives is crucial. In this study, a total of 24 single-lap shear joints with four different types of adhesives, were investigated to examine the bond behaviour of CFRP-to-steel bonded joints at a temperature of 23 degrees C, at 15 degrees C below the glass transition temperature T-g-15 degrees C, and at 15 degrees C above the glass transition temperature T-g + 15 degrees C. The results indicate that 1) the failure mode of specimens was transformed from cohesive failure or CFRP delamination failure at room temperature to adhesive-steel interface failure with an increase in temperature, 2) the bond strength of all specimens was reduced by approximately 10% at T-g-15 degrees C, and 70% at T-g + 15 degrees C. Based on a literature review, an analytical model was proposed to predict the bond strength of the CFRP-to-steel bonded joints at elevated temperatures, 3) the bond-slip relationship of the joints with linear adhesive was changed from a trapezoidal to a triangular with an increase in temperature; However, the bond-slip relationship of the joints with a nonlinear adhesive didn't change, and 4) the stiffness of the joints decreased with temperature owning to the degradation of the elastic modulus of adhesive. (C) 2020 Elsevier Ltd. All rights reserved.