A review on bi-adhesive joints: Benefits and challenges

Over the last decades, adhesively bonded joints have been employed extensively in various industries due to their prominent advantages in comparison with other traditional fastening approaches. The remarkable capability of bi-adhesive joints in enhancing the mechanical properties of structures has attracted the attention of several researchers. According to this survey, changing the configuration of adhesive joints from single-adhesive to bi-adhesive not only leads to a substantial strength improvement in bonded components but also leads to a considerable weight reduction of the structures. There are various effective parameters that have considerable influence on the mechanical properties of this type of bonding. Hence, numerous experimental and numerical investigations have been carried out in order to investigate the effect of each parameter for different types of joints, different loading conditions, and for different adhesives. This paper reviews the benefits of bi-adhesive joints and their manufacturing challenges. The effects of the aforementioned variables and their interactions on the mechanical properties of bi-adhesive joints are described. Beginning with demonstrating the procedures and manufacturing challenges of bi-adhesive joints, various joint configurations are then evaluated including single lap, double lap, plates, double-strap, and T bi-adhesive joints. In each category, various parameters such as the adhesives length ratio, adhesive properties, bonding thickness, overlap length, etc. have been reviewed and analyzed. According to the analyses, it was concluded that the strength of the structure significantly improves using bi-adhesive compared to the single adhesive joints. However, careful analysis should be carried out to select the right pair of the stiff and ductile adhesives and to set the geometries of the joint.