Abstract: Ball milling-liquid phase oxidation method was adopted to obtain the surface modified short carbon fibers (SCF). The modified SCFs with different dimensions are used to fabricate the short carbon fiber/ epoxy resin composites (SCF/ EP) by extrusion process. The surface morphology and wettability of the modified SCFs are characterized by atomic force microscope (AFM) and contact angle measuring method. Scanning electron microscope (SEM), tensile and impact test characterization are used to study their microstructures and mechanical properties. In addition, the reinforcing mechanisms of the short carbon fibers are elucidated. The results show that the surface wettability of fibers and epoxy is improved using the ball milling-liquid phase oxidation method. The maximum values of tensile and impact strength of SCF/ EP are up to 71-2 MPa and 27-75 kJ/ m2, respectively, which are increased by 103-4% and 63-9% compared with pure epoxy, respectively. The reinforcing mechanisms involved are mainly fiber debonding and pull-out, crack deflection and fiber bridging.

Key words: composite material, ball milling-liquid phase oxidation method, extrusion process, surface modified, SCF/ EP composites, reinforcing mechanism