Evaluation of aluminum to composite bonded lap joints

Adhesive bond is one of the best suitable joining technique for fiber reinforced polymer (FRP) composite structures used in aerospace applications. The weight of the composite structure greatly reduces by using structural adhesives for the joining processes. The surface preparation plays a major role for achieving the better bond strength. The present work deals with the validation of the bond strength of single lap joint(SLJ) with dissimilar adherends. The Al adherend has been considered for the surface treatments such as sand paper, NaOH and Resin pre-coating (RPC) for SLJs. The angle of contacts for the different surface treated specimens has been measured using the Young-Laplace method. X-Ray radiography and ultrasonic testing has been carried to verify the internal defects of bonded joint. The bonding strength was evaluated using a tensile and flexural test rig in polymer UTM. The bond strength of the RPC surface treated bonded joints showed better performance in terms of peak load and shear strength. The maximum shear strength has been increased up to 154.63 percentage when compared to untreated surface specimens, similar trend was observed in flexural strength. A numerical simulation model has been developed for validating the results. The comprehensive analysis for the de-bonded joints at maximum loading conditions has been done with morphological studies.