Experimental characterisation and numerical modelling of the influence of bondline thickness, loading rate, and deformation mode on the response of ductile adhesive interfaces

Abstract

A new method for characterising the rate-dependent failure of elasto-plastic adhesively bonded structures has been developed and used to investigate the different modes of loading of representative interfaces. Furthermore, experimental observations enabled a newly developed cohesive zone model that captures all critical aspects of the observed and quantified behaviour of the adhesive under consideration. In particular, the model is capable of reproducing the conducted experiments by incorporating both the dependence of the deformation rate and the adhesive thickness. For that, computed tomography of the adhesive interface was used to resolve three-dimensionally the adhesive volume. The volume fraction of microscopic voids in the adhesive was introduced into the model to rationalise the observed dependence of the mechanical response of the adhesive upon its thickness. Finally, the cohesive zone model was proven with mixed-mode fracture experiments which demonstrate the model's ability to simulate more complex deformation regimes.

On the dynamic response of adhesively bonded structures

“…Moreover, Figure 10 also compares the measured values of this study against those measured by the authors using butt joint, single lap joint and scarf joint experiments [15]. The difference between these characterisation experiments and the fracture mechanics experiments are rationalised in a later section.…”

“…One of the objectives of the present work is to employ fracture mechanics experiments to validate a cohesive zone model (CZM) -which was calibrated using butt joint, single lap joint and scarf joint experiments [15] (also named characterisation experiments from here onwards). Models of this kind are often used in finite element analysis to simulate and predict the behaviour of complex adhesively bonded structures.…”

“…Moreover, optical analysis also reveals the existence of voids and carrier fibres. These have been considered previously [15] as important features that contribute to the failure behaviour of the adhesive interface. Finally, the higher fracture energy observed in ENF specimens is believed due to multiple micro-crack creation ahead the crack tip, subsequent coalescence, and increase in friction of the surfaces resulting in additional energy absorption.…”

“…Other studies have employed the SHB with SLJ [15], pin-collar-specimens [3], torsion specimens [7] and cubic specimens [13,14] to investigate the adhesive strength under shear deformation.…”

“…The models employ a cohesive zone model developed previously by the authors [15]. Experimental results are used to validate the cohesive zone model and to compare; (i) the ability of the model to predict failure; and (ii) the validity of the developed experimental technique to measure adhesively bonded structures under different rate-and mode-dependent environments.…”