Mechanical Properties of Aluminum Composites Reinforced with PAN- and Pitch-Based Short Carbon Fibers

Pure aluminum and AC8A aluminum alloy matrix composites, which were reinforced with PAN- and pitch-based short carbon fibers, were fabricated by squeeze casting, then the composites were exposed to a heat treatment. The effects of the fiber types, composition of the matrix, and heat treatment on the mechanical properties of the composites were investigated. The fibers were in a random planar arrangement in the composites. Although the aluminum carbide was formed due to the reaction between the PAN-based fiber and pure aluminum during the casting process, there was no reaction products near the PAN-AC8A, pitch-pure aluminum and pitch-AC8A interfaces. Although the ultimate compressive strength of the PAN-based fiber composite was greater than that of the pitch-based fiber composite under every condition, the strength of the PAN-based fiber composite degraded due to the heat treatment when pure aluminum was used as the matrix. Examination of fracture surface indicated that the lower reinforcing effect of the pitch-based fiber would be due to delamination at the boundary between the highly-developed graphite crystallites in the fiber. A hardness measurement of the fibers in the composites using a nano-indenter revealed that the interfacial bonding strength between the pure aluminum and PAN-based fiber degraded due to the heat treatment.