AFM Characterization of Interphase Properties of Silver-Coated Carbon Fibre Reinforced Epoxy Composites

Carbon fibre (CF) surfaces were silver-coated using an electroless deposition technique. Atomic force microscopy (AFM) was used to measure the topography and roughness of the silver-coated carbon fibre surfaces after various deposition times before forming a composite. The height images showed that the surface coverage of silver (Ag) islets after 2 min was the most complete and uniform. AFM in the force modulation mode probed the local mechanical properties within the interphase regions in a CF/epoxy composite system. The results showed that the stiffness of the Ag coating was similar to that of the carbon fibres, and higher than that of the epoxy matrix. The interphase thickness varied from 50 nm to 200 nm, depending on the silver deposition time. The interphase morphology revealed the interaction mechanisms between the silver layers and the carbon fibres. The interfacial adhesion properties were evaluated by microbond testing. The interfacial shear strengths (IFSS) of the microcomposites were improved after Ag plating. Due to the increase in roughness and the small volume of the Ag particles compared with the epoxy resin, the Ag plating layers promoted mechanical interlocking between the carbon fibres and the epoxy resin. At a deposition time of 2 min, the maximum IFSS was 36.2 MPa, 17.9% higher than that of the uncoated specimens.