Influence of acrylic- and epoxy-based adhesives on the mechanical performance of joggle and single lap bonded joints with composite, metallic, and dissimilar adherends

This study investigates the impact of acrylic- and epoxy-based adhesives on the mechanical performance of the joggle and single lap joints of CFRP-CFRP, aluminium-aluminium, and CFRP-aluminium. Experimental testing and failure mode analysis were conducted to evaluate the shear strength and failure mechanisms of the joints. Araldite 420 adhesive demonstrated superior mechanical properties for both CFRP-CFRP and aluminium-aluminium bonded joints, outperforming other epoxy and acrylic adhesives. The joggle lap joint (JLJ) of CFRP-aluminium is stiffer than the single lap joint (SLJ) of CFRP-aluminium. However, the ultimate shear strength of dissimilar JLJ is similar to that of SLJ. The SEM and macroscopic observations on the fracture region exhibited a mixed-mode failure between adhesive and cohesive failure in bonded CFRP-CFRP and aluminium-aluminium joints. The failure mode transforms into fibre tear failure in bonded CFRP-aluminium dissimilar joints. The findings highlight the importance of selecting adhesives and the differences in the mechanical behaviour of bonded joints with CFRP, aluminium, and CFRP-aluminium dissimilar materials in optimising CFRP joint performance.