Rate-Dependent Mode I Cohesive Laws for Adhesively Bonded Aluminum Joints

This study investigates the behaviour of adhesive-bonded aluminium joints under mode I loading across various displacement rates. Butt joint specimens, comprising solid aluminium Al606-T6 alloy rods, were bonded using the pressure-sensitive adhesive (PSA) 3M VHB Tape 4930 (F). Tensile testing encompassed displacement rates (v) spanning six displacement rates: 5, 15, 50, 150, 250, and 500 mm/min. An extensometer with a 50 mm gauge measured the local displacement of adhesive bonding throughout testing. The study characterised traction-separation laws based on experimental data, establishing the relationships between cohesive parameters and displacement rates. Parameters included maximum traction, Tmax, signifying bonding strength at damage initiation, δi, final separation of joints, δf, interface stiffness, K, and dissipated energy, GIC. Results indicated that Tmax increased from 5 mm/min to 150 mm/min, with a plateau beyond. In contrast, mean damage initiation, δi, exhibited a decrease up to 150 mm/min, followed by a slight increase up to 500 mm/min. All specimens exhibited a fracture mechanism identified as complete adhesive failure, known as interface failure. Final separation of joints, δf, was rate-independent from 5 mm/min to 150 mm/min but decreased beyond. Interface stiffness, K, significantly increased from 5 mm/min to 150 mm/min, becoming rate-independent at higher loading rates. Dissipated energy, GIC, increased up to 150 mm/min and slightly decreased at higher rates.