(2) It is difficult to check the bonding quality. At present, there are only some methods to detect defects, but there is no satisfactory nondestructive testing method for bonding strength.
(3) The surface treatment of the adherend and other process control requirements of the bonding process are very strict. Some adhesives also require special fixing devices and heating and pressurizing equipment.
(4) Although many adhesives have been proved to be reliable in practical application, the research on mechanical properties and aging of bonded joints is not as mature as that of metal materials, so the use of adhesives in some aspects is limited. In addition, adhesives are mainly polymers, and the mechanical properties of polymers are sensitive to temperature changes, so the application temperature range of adhesives is limited.