These slides were presented at the NAFEMS World Congress 2025, held in Salzburg, Austria from May 19–22, 2025.

Abstract

Adhesives are commonly used in various engineering applications, providing bonding solutions in industries such as automotive and aerospace. Accurate modeling of adhesives is essential for predicting the performance and reliability of bonded structures. Finite Element Analysis (FEA) has become a valuable tool for simulating the behavior of adhesive joints under different loading conditions. Depending on the aim of the analysis, different types of material models are more or less suitable for different applications. Additionally, access to testing capabilities, costs, and the effort of the calibration process can influence the choice of material model. Common modeling approaches include viscoelastic models, elastic-plastic models, and cohesive zone models, each with different capabilities and limitations. Viscoelastic models can be built based on Dynamic Mechanical Analysis (DMA) data, making them very efficient for the calibration process. These models are used to capture the time-dependent behavior of adhesives and generally include strain-rate and temperature dependency, as well as creep and stress relaxation to some extent. The accuracy of viscoelastic models is typically limited by the degree of deformation. Elastic-plastic models can predict the behavior of adhesives under finite strains, accounting for both elastic (reversible) and plastic (irreversible) deformation. While these models are generally cost-effective and efficient to generate, the experimental effort can increase significantly when incorporating temperature or strain-rate dependency. Although failure cannot be predicted explicitly, these models can provide an indication of failure based on local stresses and strains. Cohesive Zone Models (CZMs) are widely used to simulate the initiation and propagation of cracks in adhesive layers. CZMs represent the adhesive layer as a continuum with a predefined traction-separation law that characterizes the material's response to loading. This approach allows for detailed analysis of fracture processes, including the prediction of crack initiation and growth. Although CZMs offer excellent predictive capabilities, the calibration process requires a range of different experiments. Additionally, incorporating strain-rate and temperature dependency is only supported by a few commercial FEA software packages. In conclusion, the modeling of adhesives within the context of Finite Element Analysis involves several techniques, each suited to different aspects of adhesive behavior. Viscoelastic, elastic-plastic, and cohesive zone models provide comprehensive tools for simulating the performance of adhesive joints. By leveraging these techniques, engineers can enhance the design and reliability of bonded structures across various industries.