Experimental parametric investigation on the behavior of adhesively bonded CFRP/steel joints

This paper presents an extensive experimental and numerical study on the behavior of CFRP/Steel adhesively bonded double strap joints (DSJ). A total of 50 DSJ specimens were tested under static tensile loading. The digital image correlation (DIC) was used to measure the backface deformation. A total of six adhesives that feature different stiffness, strength, ductility, and toughness were analyzed. A parametric study including several variants was carried out. The influencing parameters considered are the following: the adhesive type, adhesive thickness, CFRP elastic modulus, CFRP length, surface treatment, and steel thickness. The results revealed that rigid adhesives commonly used in the construction industry do not provide the best performance for the CFRP/steel joints, instead, tough adhesives which combine high strength and ductility are more suitable for strengthening metallic infrastructures. Steel plastic yielding has a significant influence on the strength, behavior, and failure modes of the CFRP/steel adhesive joint. A numerical model validated with experimental data was developed in ABAQUS. The experimental observations including failure modes, joint strengths, and ductility were discussed using the numerical model. The joint strength efficiency is highly recommended as a design criterion for bonded joints.