Using adhesives for connection technology has many benefits. It is cost-efficient, fast, and allows homogeneous stress distribution between the bonded surfaces. This paper gives an overview on the current state of knowledge regarding the technologically important area of adhesive materials, as well as on emergent related technologies. It is expected to fill some of the technological gaps between the existing literature and industrial reality, by focusing at opportunities and challenges in the adhesives sector, on sustainable and eco-friendly chemistries that enable bio-derived adhesives, recycling and debonding, as well as giving a brief overview on the surface treatment approaches involved in the adhesive application process, with major focus on metal and polymer matrix composites. Finally, some thoughts on the connection between research and development (R&D) efforts, industry standards and regulatory aspects are given. It contributes to bridge the gap between industry and research institutes/academy. Examples from the aeronautics industry are often used since many technological advances in this industry are innovation precursors for other industries. This paper is mainly addressed to chemists, materials scientists, materials engineers, and decision-makers.

Steel bridges with orthotropic decks are a common construction method for long-span bridges. The type of construction was developed in the 1960s, and the early structures in particular show increasing crack damage. The reasons for this are, on the one hand, design deficiencies and, on the other hand, massively increased traffic loads. Therefore, there is a need for rehabilitation methods that neither weaken the cross-section, like bolted solutions, nor introduce thermal stresses, like welds, but so far there are no reliable and economic alternatives. This paper summarizes the state of the art on possible damage categories of orthotropic bridge slabs and presents a new rehabilitation alternative using bonded steel patches for crack rehabilitation. It is reported from an ongoing research project how to determine numerically the effectiveness of the bonded steel patches. For this purpose, simple analytical calculations are first used to determine the determining factors and to record their influence. Subsequently, nonlinear numerical calculations with the Drucker-Prager material model are used to identify the stress distributions in the bonded joints in order to optimise the patch geometries. To this end a stiffness factor is presented that can be used to classify such patch bonds and categorize them in terms of their effectiveness.

Despite much advancement of typical joining techniques in steel construction, fundamental problems, like residual stresses for welds as well as weakening of the cross section for bolts and screws, still remain. The application of bonded joints could improve the situation. The automotive industry shows the potential of this certain joining technique since years. Even in civil engineering and especially in steel construction, researchers are continuously establishing the bonding technology as a structural element. On the one hand bonded joints mean a challenge, but on the other hand an innovation, what is shown in this paper.