Efficient Models for Simulating the Flow of Highly Viscous Adhesives and Sealants in Manufacturing Processes

• Applicants: Professor Dr. Bernd Mayer, since 11/2020; Professor Dr.-Ing. Michael Müller
• Subject Area: Production Automation and Assembly Technology
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 445254897

Fibre-reinforced polymers, high-strength steels, and modern multi-material lightweight construction are leading to vastly increased usage of adhesive bonding technology. Proper filling of the adhesive layer is decisive for the quality of the end product. Trapped air bubbles and under-filling of the gap lead to performance issues such as diminished joint strength and durability. It is currently a complex technical challenge to optimize the adhesive layer with the aim of completely filling the gap using minimized amounts of adhesive material. Adequate guidelines for a targeted approach and efficient numerical tools for predicting gap filling have yet to be developed. In order to avoid insufficient gap filling, especially in applications with safety concerns or environmental loading, a significant (30-50%) overfilling of the gap is currently implemented in the manufacturing process. In such cases, the excess adhesive spills out of the gap, which has both ecological and economic drawbacks. Additionally, a second decisive factor is the joining process of positioning the second adherent onto the first. This results in a squeezing flow between the parts to be joined in what is usually a narrow gap. Only by controlling the resulting squeeze flow can the desired gap filling be attained within the predefined tolerances; this is a core objective of this research project. Explicit methods for describing the squeezing flow are not yet available. Current simulations usually describe multiphase flows based on the Navier-Stokes equations. The geometric proportions of an adhesive joint, often with thicknesses on the order of tenths of a millimetre but sometimes metres long, often lead to numerical instabilities and excessive calculation times. Well established modelling methods are available for tribological applications. These were developed specifically for systems with known thickness-to-length ratios and only consider the variables relevant for a squeezing flow in a narrow gap. Such methods have not yet been transferred to bonding and sealing applications. In a preliminary joint study, the applicants were able to show that these techniques known from tribology are, in principle, very well adapted for describing joining processes.The methods developed at the IDS of the TU Braunschweig towards the effective description of tribological squeeze flows are utilized as the basis of this research project. The immediate goal is to adapt and extend these methods for modelling adhesive bonding, and to validate them experimentally at the Fraunhofer IFAM in Bremen on academic and practical systems. In this context, this modelling technique will also be applied to adhesive processes with an injected adhesive, which is a mathematical special case of this methodology.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Dr. Till Vallée, until 11/2020