Structural Modelling of Adhesives : Models for Dynamic Response Analysis

Sammanfattning

Adhesive joining technologies have received great praise within industries such as aerospace, transportation, electronics, and mechanical systems, owing to the benefits of lightweight design and durability. Recently, well-established adhesive manufacturing, application, and testing techniques are experiencing increased demand for reliable and effective modelling methodologies. Polymer-based adhesives, which fall into categories such as elastic-plastic, viscoelastic, hyperelastic, viscoplastic, and thermosensitive materials, present significant challenges to structural modelling due to computational complexity and costs. Currently, novel characterisation methods and modelling techniques for fracture analysis of adhesive joints are readily available. However, in many engineering applications, the precise stress and strain states around propagating cracks within adhesive layers are of lesser importance. Consequently, cohesive zone models have been successfully implemented in most finite element (FE) software, offering cost-efficient methods for simulating the debonding behaviour of adhesive joints. While fracture mechanics and other static/quasi-static analyses of adhesive joints have been extensively studied in recent years, there is an incentive for developing reliable methods for modelling the dynamic response of adhesively bonded structures. In this study, three alternative adhesive layer FE representations for modal-based analyses are discussed and evaluated. Continuum models, phenomenological models, and contact models are described and applied to lap-joint specimens with different adhesive materials and configurations. A vibration testing method for parametric investigation of lap-joints is presented, and all FE models were validated against the test results. Constant material damping and Rayleigh damping are investigated as alternatives to capture the global damping behaviour of the joints. Results suggest that stiff structural adhesives are adequately modelled using constant material damping or bonded contact representations, whereas softer adhesives require alternative representation and damping techniques, likely due to the associated increased damping and viscous effects. Rayleigh damping proved suitable for capturing the response of soft adhesives; however, it faces challenges in generalising to multi-component structures. Additionally, thinlayer phenomenological representations of adhesive layers in lap joints offered significant time savings compared to in-use bonded contact models. Furthermore, thin-layer models offer the flexibility of material-specific damping.