Certification of adhesively bonded structures: Review and outlook

There is increasing interest in achieving unprecedented levels of eco-efficiency. Consequently, many industries, including the aircraft, construction, automotive, naval, offshore, and wind energy sectors, aim to lighten structures by combining or replacing metals with composites. Adhesive bonding is the most promising joining technology regarding weight and performance, but its application remains largely limited to secondary, non-safety-critical structures in many industries. The main reasons for this limited acceptance of adhesive bonding are our restricted knowledge of the associated key manufacturing parameters, non-destructive inspection techniques, damage tolerance methodologies, and tools for diagnosis and prognosis of structural integrity. Certification of a product, service, or system is the provision, by an independent body, of a written assurance that the product, service, or system under consideration meets specific requirements. The present paper reviews for the first time, the relatively unexplored topic of the certification of adhesively bonded structures in the four broader industrial sectors: civil aviation, construction, maritime, and automotive. After highlighting the goals of this study, we discuss several elements involved in the certification process: material compatibility, bonding process, component design, manufacturing, physical tests, and simulation. This work is intended to serve as a roadmap for developing certification schemes for primary adhesively bonded structures to increase the acceptance level of adhesive bonding in various industries.