Effect of silane treatment on adhesion of adhesive-bonded carbon fiber reinforced nylon 6 composite

In this study, a silane coating, KH560, along with an abrasion pretreatment procedure for carbon fiber reinforced PA 6 composite with 30% mass fiber (C-f/PA6) and AA6061-T4 was developed. Composition and structure of this silane coating and effect of this coating on the strength and water resistance of the adhesive-bonded C-f/PA6 and AA6061 were investigated. Test results revealed that silane pretreatment improved the static strengths of the adhesive-bonded C-f/PA6-C-f/PA6 and C-f/PA6-AA6061 by 23% and 21%, respectively. X-ray photoelectron spectroscopy (XPS) analysis of the adhesive-bonded treated C-f/PA6 indicated that the improvement in strength was primarily attributed to the formation of Si-O-Si and Si-N covalent bonds on the surface of C-f/PA6, which enhanced the bond adhesion between the silane coating, adhesive, and adherends. In addition, abrasion of adherends prior to silane pretreatment further improved the strengths of the adhesive-bonded C-f/PA6-C-f/PA6 by another 20%. While silane and abrasion-silane treatment improved the strength of the adhesive-bonded C-f/PA6-C-f/PA6 and C-f/PA6-AA6061 in ambient conditions, the strength of water immersed silane coated joints with and without abrasion was decreased by about 50% (i.e., immersed in water at 54 degrees C for one week). All tested bare and treated joints with and without water immersion exposure were fractured in adhesive mode. Analyses of the test results revealed that to improve the failure mode and bond strength it is necessary to form a Si-N functional group in the silane coating by thoroughly cleaning and removing the contaminants and weak layers on the surface of C-f/PA6.