Carbon Fiber–Reinforced Polymer-to-Steel Interfacial Stress Parameter Sensitivity Based on Viscoelastic Constitutive

The viscoelastic constitutive relation for adhesives is described using the modified Maxwell model to study the influences of the viscoelastic constitutive relation of adhesives and of the design parameters of carbon fiber reinforced polymer (CFRP)-strengthened steel beam on CFRP-to-steel interfacial stresses. In view of the fact that the adhesive layer of reinforced beam is mainly shear deformation, the analysis of the viscoelastic constitutive of the adhesive is simplified. The solution to the variables of the modified Maxwell model is given using Laplace transform and inverse Laplace transform. Finite element analysis of a typical simply supported steel beam strengthened by CFRP is conducted using ABAQUS. The variation rule of the interface stress with loading time is analyzed. The effects of CFRP elastic modulus, CFRP thickness, adhesive layer thickness, and distance between the CFRP end and the support on the CFRP-to-steel interfacial stress are discussed in detail. On the basis of the fundamental principle of the sensitivity analysis, the degree of sensitivity of the interfacial stress to the different parameters is investigated through quantitative analysis. Results show that (1) the viscoelasticity of the adhesive causes stress redistribution on the bonding interface, and the peak shear stress and peak normal stress of the interface decrease with time; (2) the thicker the adhesive layer, the thinner the CFRP, and the less the elastic modulus of the CFRP; (3) the closer the CFRP to the bearing, the less the interfacial stress; (4) the parameter that exerts the most influence on the interfacial shear stress at the edge of the CFRP is the distance from the edge of the CFRP to the bearing, with a sensitivity factor of 1.359; and (5) the parameter that exerts the most influence on the interfacial normal stress at the edge of the CFRP is the thickness of the polymer, with a sensitivity factor of 0.956.