Impact Performance Enhancement of Dual-Adhesive Joints Through Adhesive and Geometric Parametric Investigation

Adhesively bonded joints are widely used in engineering structures due to their high strength-to-weight ratio and improved stress transfer. However, stress concentrations near the overlap edges limit their performance. Dual-adhesive joints (DAJs) combine adhesives with different mechanical properties to improve stress distribution and delay failure, but their behavior under impact loads is insufficiently understood. This work investigates the impact performance of steel single-lap DAJs using Cohesive Zone Modelling (CZM). Unlike previous studies that mainly focused on either adhesive selection or geometric parametric investigation separately under static loading conditions, this work provides a combined assessment of adhesive and mixed geometric modifications on the impact response of dual-adhesive joints. The numerical approach was first validated against experimental results, showing good strength predictions. Three adhesive combinations were studied, and the influence of outer chamfers, inner chamfers, and adhesive fillets was evaluated on stress distributions, maximum load (Pm), maximum load displacement (δm), and absorbed energy (E). Adhesive fillets were the most effective geometric modification, significantly reducing peel (σy) and shear stress (τxy) concentrations and improving performance. The DP8005+AV138 and DP8005+XNR6852E-2 adhesive combinations exhibited the best behavior, with the adhesive fillet configuration increasing Pm by up to 40.8% and E by up to 59.7% compared with the reference geometry. Outer chamfers provided moderate improvements, whereas inner chamfers had a limited or negative influence on joint performance. Combining geometric modifications improved stress distributions but did not outperform the best fillet-only configurations.