Influence of temperature and humidity curing environments on the bonding performance of CFRP-steel plate interfaces

To investigate the impact of combined temperature and humidity curing conditions on the failure modes and delamination mechanisms of CFRP-bonded steel interfaces, this study conducted double-shear bonding tests on CFRP-steel composites, considering multiple factors such as temperature, humidity, bonding length, and adhesive layer thickness. The influence on the interfacial bonding performance of CFRP-steel interfaces was analyzed comprehensively, and the axial strain distribution of CFRP during static tensile processes was monitored using 3D-DIC technology. The findings reveal that peak bonding load is higher under curing conditions of 60℃ and 60% relative humidity, whereas low temperature and high humidity environments are more prone to cause failure at the steel-adhesive interface. Both increased temperature and humidity resulted in a reduction in interfacial shear stress peak values and an increase in slip, illustrating the impact of temperature and humidity on the ductility and adhesive properties of the interface. Additionally, it was found that an increase in bonding length helps disperse stress across a wider area, and a thinner adhesive layer contributes to higher interfacial shear stress peaks and improved stress distribution. Lastly, based on the experimental data, a simplified trilinear shear-slip model was derived using the smoothing method, providing theoretical support and design reference for the engineering application of CFRP-reinforced steel structures.