Evaluation of the bond performance of CFRP–GFRP composite lap joints using single and dual-adhesive configurations

The present investigation explores how different adhesive configurations affect the performance of CFRP–GFRP composite bonded joints. Two bonding strategies were considered: single-adhesive joints and dual-adhesive joints. Single-adhesive joints using brittle (AV138) and ductile (Araldite-2015) adhesives were compared with dual-adhesive joints combining both adhesives. X-ray radiographic inspection was performed to assess the quality of the prepared joints and also to inspect the precise locations where each adhesive was applied in the bond region. Experimental tensile testing coupled with Digital Image Correlation (DIC) was conducted to capture deformation fields, failure behaviour and bond strength. Ductile single-adhesive joints exhibited an 18.19% higher load-carrying capacity than brittle single-adhesive joints while dual-adhesive joints achieved a 26.25% improvement over single brittle-adhesive joints. Finite element simulations of peel and shear stress distributions along the bond-line showed close agreement with the experimental observations. Results show that the dual-adhesive concept effectively restricts interfacial de-bonding and enhances joint performance, offering an effective strategy for bonding dissimilar composite materials.