On loading, there is a more uniform distribution of stresses over the bonded area. The local concentrations of stresses present in spot welded or mechanically fastened joints are avoided. Bonded structures can consequently offer a longer life under load. The bonded joint being continuous produces a stiffer structure. Alternatively, if increased stiffness is not needed, the weight of the structure can b decreased while maintaining the required stiffness.
Adhesives form a continouus bond between the joint surfaces.
Rivets and spot welds pin the surfaces together only at localised points. The riveted joint on the left is highly stressed in the vicinity of the rivets. Failure tends to initiate in these areas of peak stress. A similar distribution of stress occurs with spot welds and bolts. The bonded joint on the right is uniformaly stressed.