Effect of metal as part of fillet on the tensile shear strength of adhesively bonded single lap joints

The effect of fillet containing metallic components on the strength of adhesively bonded single lap joints has been undertaken by alternating the shape and size of metallic components as a part of fillet or whole fillet at the end of the joints. Mild carbon steel and epoxy structural adhesive were used to prepare single lap-shear joints. Three types of steel components or fillets were embedded in the joints. Two of them were in shapes of wire and the remaining was a column in section of an isosceles right-angled triangle. After their failure, all specimens were analyzed by the electron probe microanalysis (EPMA) meter to explain the failing procedure of single lap joints. The results obtained from experiments show that the shear strength increased about 45% by embedding steel wire in the fillets. Its EPMA image also gives more fine toughness pits on the fracture surface and other tracks of adhesion failure while in the cases of fillets without metallic component or with a thorough metal column as fillets show the micro-appearance of being torn off. It is evident that the existence of the metallic component in the shape of round bars may improve the action of the fillets in the process of shear strength testing and failure.