Effects of residual oils on the adhesion characteristics of metal-CFRP adhesive joints

Although proper surface treatment is very important in adhesively bonded joints, perfectly clean surfaces have been considered in previous studies. Making the surface of an adherend clean is generally very difficult in real fields. In order to identify the minimum surface treatment that can achieve the required adhesion strength, we investigated the effects of residual oils on the adhesion characteristics of metal-carbon fiber-reinforced epoxy composites adhesive joints. We found that the amount of residual oils on the metal surfaces should be controlled to be less than 1.0 g/m2, and that enough adhesion strength could be obtained if the flame treatment followed. Experimentation also suggested that three or four cycles of ethanol cleansing and five seconds of flame treatment was the minimum surface treatment easily adoptable in industrial fields.