Adhesive layer thickness in hybrid joints

The resurgence of interest in hybrid joints, combining adhesive bonding with mechanical fastening in engineering applications, is driven by the recognition of unique advantages and limitations inherent in each joining method. Unlike conventional bonded joints with precise adhesive thickness control, hybrid joints involving pre-tensioned bolts depend on a process termed squeeze-flow, influenced by joint geometry, adhesive viscosity, and adhesive filler presence. A method for the precise measurements of the adhesive layer thickness, conducted at 5 mm intervals, proved its accuracy and repeatability. The results revealed the significant impact of adhesive viscosity and filler characteristics on adhesive layer thickness. Viscosity, while playing a central role, is not acting in isolation, as filler properties collectively influence adhesive layer thickness distribution and bonding performance. The complexity of this relationship underscores the interplay between adhesive layer thickness, viscosity, filler content, and load-bearing capacity. Smaller-sized fillers result in thinner layers and reduced load capacities, while adhesives with larger particles exhibit higher load capacities. This complexity emphasizes the need for a nuanced approach when selecting adhesives for specific applications, considering not only viscosity but also filler attributes to optimize bonding performance in hybrid joints.