Tensile behavior of carbon nano-fiber-reinforced Cu composite using the liquid infiltration process

A carbon nano-fiber (CNF)-reinforced Cu composite was fabricated by the liquid infiltration process, and the tensile behavior of the fabricated composite was evaluated. For the unidirectional alignment of the severely entangled CNFs, the mechanical drawing process was utilized. The bundle of drawn Cu tubes, compacted with unidirectionally aligned CNFs, was placed on the specially designed mold. The mold was subsequently canned, degassed, evacuated, heated at 1100 °C for 10 minutes in the electric furnace to liquefy the Cu, and, finally, transferred to the press. The optical and scanning electron microscope (SEM) micrographic observations of the final product demonstrated that, even though the CNFs were not uniformly distributed throughout the specimen due to the molten metal flow during the melting process, the local unidirectionality was preserved in those areas where CNFs were densely packed. Tensile test results showed that a twofold increase in tensile strength was obtained with an approximately 13 pct CNF reinforcement, despite there being no known bonding between CNFs and Cu. The transmission electron microscope (TEM) observations demonstrated that the C atoms in the CNF were forced into the Cu matrix, which caused the roughening of the CNF surface and the supersaturated solutionization of the Cu matrix in the vicinity of the CNF during liquid processing. A strong mechanical interlocking was believed to exist between the CNF and Cu due to the roughened surface of the CNF and the stress field developed around the CNF as a result of the supersaturated solutionization of the Cu matrix. This mechanical bonding mechanism appeared to be unique in the composite system reinforced with nano fibers produced by the liquid infiltration process.