Cyclodextrin as sizing for carbon fibers: new bonding mechanism improves adhesion in carbon fiber reinforced epoxy resin

In this study, β-cyclodextrin was covalently bonded on carbon fibers and its influence through host-guest complex formation was analyzed. Since cyclodextrins act as host molecules for aromatic compounds, complex formations can be performed in carbon fiber reinforced epoxy resins, between the carbon fiber surface and the aromatic compounds of the surrounding plastic. This interface design leads to improved adhesion between fiber and plastic. An increase of the interfacial shear strength from 12 MPa to 38 MPa was detected. It was possible to increase the interfacial shear strength even further, to 41 MPa, through a prior complex formation with one of the plastics components. In addition to the micromechanical analysis, energy-dispersive x-ray spectroscopy and contact angle measurements were performed to confirm the covalent coating of cyclodextrin on the carbon fiber surface.