Enhancing shear strength and structural stiffness of composite joint with carbon nanotube reinforced adhesive through co-bonding technique

High-performance co-bonded joints are nowadays indispensable to join subcomponents of tails, wings and fuselage in aerospace assemblages. The current study examined the effect of incorporating multiwall carbon nanotube (MWCNTs) on mechanical and free vibrational behaviour, such as natural frequency and resultant damping factor of co-bonded single-lap composite joints. The experimental results indicated 0.25 wt.% MWCNT reinforcement into the epoxy adhesive considerably improved the joint strength of the co-bonded single-lap composite joints by 34.52%. However, the higher loading of MWCNTs reduced the shear strength of co-bonded single-lap composite joints due to agglomeration. Scanning electron microscopy (SEM) affirmed that lower wt.% MWCNT reinforcement improved the interfacial bonding, developed rougher surfaces, shear bands, and deviated crack growth path in the bond-line to an elongated path. Moreover, the comparison of failure surfaces of neat and CNT reinforced specimens confirmed that the effective presence of MWCNTs changed the failure mode failure of co-bonded lap joint from adhesive to cohesive failure mode. The experimental free vibrational analysis affirmed that 0.25 wt.% MWCNT reinforced co-bonded joint has the highest fundamental natural frequency. Results also depicted that higher wt.% MWCNT loading exhibited better damping owing to particle accumulation and higher interaction between adhesive and laminate.