Directing helical CNT into chemically-etched micro-channels on aluminum substrate for strong adhesive bonding with carbon fiber composites

This study presents a simple technique for positioning helical carbon nanotubes (CNTs) into chemically-etched vertical micro-channels on an aluminum (Al) substrate for strong adhesive bonding with carbon fiber composites. Helical CNTs with diameter up to 100 nm and length up to 10 μm were dispersed evenly in an acetone-diluted resin pre-coating (RPC) solution consisting of 90 wt% acetone + 10 wt% resin (without hardener), then applied onto the chemically etched Al substrate with vertical micro-channels. CNTs were dragged into those vertical micro-cavities through the capillary action during the evaporation process of acetone. The shear bond strength was more than doubled by the quasi-Z-directional CNTs, confirming the critical role of CNT bridging across the interface between the epoxy adhesive and Al substrate. Scanned electron microscope (SEM) and focused ion beam (FIB) were used to reveal micro-channels on the Al substrate. RPC on the surface of carbon fiber composites is also beneficial.