Viscous fingering in adhesive bonding

Due to the adoption of multi-material construction methods in modern lightweight design, along with the use of adhesive bonding technology, thermally induced relative displacements between the joining components arise during the curing process. As a result, the original bond area is significantly reduced and exhibits a meandering structure. This structure, once cured, can lead to increased stress buildup in the joint due to the reduced adhesive area and the notch effect. This work focuses on the experimental characterization and numerical description of a problem known as “viscous fingering”. To investigate this, adhesive surface reduction is experimentally investigated using a butt-bonded joint specimen (BJS) and an LWF–KS2 specimen at various displacements. Additionally, two-phase fluid simulations are carried out using computational fluid dynamics (CFD) to predict the formation of the adhesive surface. The finite element (FE) method is also used to analyze the adhesive surface reduction and simulate the mechanical properties of the bonded joint.