Adhesive Bonding

Adhesive bonding is the pioneering joining process of the 21st century. It enables the reliable bonding of identical as well as dissimilar materials with an adhesive and is thus essential for the advancing multi-material lightweight construction. Unlike welding or riveting, adhesive bonds do not weaken the mechanical properties of the parts to be joined. In addition to mechanics, bonded joints integrate specific requirements: They can conduct heat, electrically insulate, seal or bridge tolerances. Professionally designed adhesive bonding processes integrate into series production without interference. Adhesive bonds can be assured of high quality through process design. For these reasons, adhesive bonding has become established across all industries in recent decades.

Adhesive bonding at Fraunhofer IFAM

Fraunhofer IFAM is the internationally leading independent research institute in the field of "adhesive bonding". For 50 years, highly qualified, multidisciplinary teams have been working on the development of this multifaceted joining technology. The many years of experience, the high level of diversification of the more than 200 employees in the divisions, and the comprehensive equipment allow rapid and high-quality processing of services as well as research and development orders. The supplier-independent solutions range from one-day consultations to the detailed design and implementation of tested production concepts and can cover the entire bonding process chain.

Adhesive bonding in manufacturing

The integration of adhesive bonding into industrial manufacturing requires an approach tailored to the specific application. Adhesive selection must take into account the requirements for the end product and for the manufacturing process. The design of bonded joints is based on analytical or numerical calculation. This is based on experimental characteristic values of materials, joints and components. At the same time, the flow and curing properties are characterized in order to design the manufacturing process. For demanding bonded joints or for difficult surfaces, pretreatment of the component surfaces is often necessary. The materials are cleaned and activated or modified so that adhesives can adhere to them for a long time. The aging behavior must be analyzed and thus the service life estimated. The dispensing and application technology are part of the automated joining process. Rapid curing processes are often used to reduce cycle times. Reliable production integrates quality assurance procedures and requires qualified personnel.

Adhesive bonding applied

Bonding processes have to be designed individually: In the transportation industry's body-in-white bonding of automotive construction, windscreen bonding of rail vehicle construction and sandwich bonding of aviation differ greatly from each other. Micro-bonding in electronics requires special adhesives and boundary conditions, as the adhesive quantities are millions of times lower than those for bonding in civil engineering. Medical technology places new demands on the safety and biocompatibility of adhesives. In the aerospace sector, it must be noted that adhesives can be used at extremely high and extremely low temperatures. In the packaging industry, on the other hand, manufacturing costs and speeds play a decisive role.

Consulting around adhesive bonding

The range of services covers the entire bonding process chain and adhesive selection, characterization of the mechanical as well as the processing properties of adhesives, design and validation of bonded structures, thermoanalytical, spectroscopic, rheological, physical characterization, development and application of dispensing and application processes, consulting on quality assurance of bonding processes, customer-specific design of industrial processes, testing and production of adhesive tapes, analysis of damage cases and elimination of production faults.

The range of services is complemented by many years of experience in the polymer-chemical formulation of adhesives and by the diverse possibilities of surface pretreatment and surface analysis. The long-established, comprehensive and globally offered portfolio of further training in adhesive bonding technology, with versatile courses and globally recognized qualifications, completes the range of services. The verification of the standard-compliant implementation of industrial bonding technology based on DIN 2304 "Adhesive Bonding Technology - Quality Requirements for Adhesive Bonding Processes" and DIN 6701 " Adhesive Bonding of Rail Vehicles and Vehicle Parts" is also part of the range of services. Fraunhofer IFAM also provides approved auditors for both standards.

Current research goals in the field of adhesive bonding

Download the Institute Profile (PDF)

The latest updates about adhesive bonding at Fraunhofer IFAM can also be found on our LinkedIn page.

Marvin Kaufmann wins award "Best Oral Presentation" at AB2023

Marvin Kaufmann of Fraunhofer IFAM received the award "Best Oral Presentation" from the "Scientific Committee" of the "7th International Conference on Structural Adhesive Bonding AB2023" for his presentation "How adhesives flow during joining". He received a certificate and a book prize from Lucas F. M. da Silva, the chairman and organizer of the conference. The conference is held every two years in Porto.

The topic "How adhesives flow during joining" represents a combination of great experimental work and modeling, involving process development and systematic analysis to address a significant problem in adhesive technology. His work is very innovative because the new method clearly shows how adhesives flow during joining. This novel and more comprehensive approach will certainly save costs, but more importantly will improve sustainability as less "trial & error" is required to determine the ideal application pattern, and as overfilling is completely avoided, which in turn reduces waste and cleaning.

Presentation "Simulation of adhesive bonding manufacturing technology"

Our colleague Holger Fricke opened this year's conference "Adhesive Bonding - AB2023" in Porto with the presentation "Simulation of adhesive bonding manufacturing technology". The importance of adhesive bonding manufacturing technology for the quality of industrial products is increasingly taken into account. A complete testing of bonded joints is technically not possible, therefore the quality of each produced bonded joint still depends on the correct execution of the manufacturing process. For more than 20 years, Fraunhofer IFAM has been developing specific simulations to understand in detail the manufacturing steps of dosing, applying, joining, fixing, hybrid joining, and curing, thereby minimizing sources of error. In his overview presentation, he briefly outlined the thematically related presentations by Marvin Kaufmann, Till Vallée, Jonas Wirries, Moritz Huf, Koichi Yokozeki, Michael Müller and Florian Flaig. 

Presentation "Adhesive bonding works - even with few joining points"

Hybrid joining in automotive body-in-white combines adhesive bonding with mechanical joining points or spot welds. It combines the high crash energy absorption capacity and stiffness of bonded joints with the fast process speed and peel strength of mechanical/thermal joining. The hybrid joining points are usually placed at a constant spacing to hold the bond in place until curing of the adhesive. However, the mechanical joining points and welding spots interfere with the formation of an optimally dimensioned and uniform adhesive layer. As a result, they significantly reduce the load-bearing capacity of the adhesive.
In the presentation "Adhesive Bonding works - even with few joining points" at the "Joining in Car Body Engineering" conference of the "Automotive Circle", Moritz Huf from BMW and Holger Fricke from Fraunhofer IFAM addressed the question of what spacing should ideally be maintained for a given hybrid joint? Using the results of fluid structure simulations, they were able to significantly reduce the number of joining points while increasing the quality of the bonded joints. The presenters showed examples in which they were able to increase the joining point distance from 50mm to over 150mm.

Understanding and optimizing adhesive bonding production

In adhesive bonding, the manufacturing process is a key for improving the quality of the final product. Fraunhofer IFAM in Bremen has been researching the flow behavior of adhesives for two decades to understand industrial dispensing, application, and squeezing with the aim to improve adhesive manufacturing. A recent publication investigates the flow during the squeezing of an adhesive bead during the joining process. The industrial squeezing of the bead is modeled experimentally by "squeeze flow tests" and characterized with high accuracy. Research is conducted into how the surface of an adherend affects adhesive flow. The article "Do surface pretreatments for adhesives influence the squeeze flow?" can now be downloaded here.