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

Abstract

In many engineering applications, the integrity of adhesive bonds must be ensured over service life when exposed to mechanical stresses. In order to assess the structural integrity of adhesive bonds numerically, there is an increasing need to efficiently model and simulate the strength, damage and failure behavior of adhesives. This includes i) structural adhesives (e.g. curable epoxy-, acrylate-, or polyurethane based adhesives which exhibit thermosetting behavior) but also ii) pressure-sensitive adhesives (adhesive tapes) which behave more elastomeric-like. Pressure-sensitive adhesives, in particular, typically exhibit a highly nonlinear elastic-viscoelastic material behavior including strains at failure of up to 500% or more. This makes a numerical treatment using conventional continuum finite elements difficult if not completely infeasible. One approach to circumvent these deficiencies is cohesive zone modeling. Cohesive zone models make use of constitutive traction-separation laws which enable to incorporate damage and failure mechanisms for adhesives straightforwardly and do not render mesh-dependent results as it would be the case for continuum-based techniques. In particular, the incorporation of the strong nonlinear and rate-dependent response seems to be challenging, because the conventional bilinear traction-separation laws which are available in basically all commercially available finite element software packages are not sufficient to model such complex material behavior. On the other hand, self-implemented user-subroutines which may be used as an alternative are mostly not feasible to be used in an industrial environment due to the high implementation effort, inferior robustness and higher computational cost which mostly prohibits straightforward usage for large-scale simulation problems. This presentation gives an overview of accurate but yet efficient nonlinear cohesive zone modeling techniques suitable for modeling damage and failure for i) structural adhesives and ii) pressure-sensitive adhesives (adhesive tapes) without the need for user subroutines. Suitable testing and characterization methods for both adhesive categories will be presented and compared to each other. Material model calibration and parameter identification techniques based on these tests for cohesive zone models will be discussed for rate-independent and rate-dependent use cases. Verification and validation test cases will be discussed to underline the applicability of these models. Finally, a variety of different application cases ranging from quasi-static to impact scenarios will be presented.