Characterization and properties of AA6061-based fiber metal laminates with different aluminum-surface pretreatments

Abstract

In this study, an Al/CFRP/Al laminates was prepared with three types of aluminum alloy AA6061 surface treatments (sanding, anodizing, and surface modification) to improve the metal–composite interface (MCI) strengths. The results showed that the shear strengths of Al/CFRP/Al laminates modified by silane coupling agent and pretreated by phosphoric acid anodizing were similar, approximately 50 MPa, which were significantly higher than those subjected to sandpaper-sanding pretreatment (38 MPa). Results of scanning electron microscopy (SEM) revealed that the nanoscale porous anodized film produced on the AA6061 surface after anodizing pretreatment enhanced the wettability of CFRP on AA6061 sheets, leading to strong interfacial bonding. XPS analysis showed that a new chemical bond, AlOEP, appeared at the interface between CFRP and anodized AA6061, which clearly indicated that the anodized layer could enhance the mechanical anchoring effect and promote its chemical reaction. And the chemical bonds of AlOSi and SiC were found at the interface between CFRP and silane-modified AA6061, thereby proving the existence of a silane flexible layer, which enabled the adjustment of the thermal expansion coefficient mismatch between AA6061 and CFRP and the improvement in the stability of the mechanical properties of Al/CFRP/Al laminates.