Electrical conductivity of discontinuous filament-reinforced unidirectional composites

The electrical conductivity of discontinuous filament-reinforced unidirecti onal composites was investigated. The discontinuous reinforcement used was copper filament, and the matrix materials included solder and epoxy. It was found that the composite conductivity increases with filament length and e ventually becomes a constant. Such behavior is described by introducing an interface impedance and the principle of rule of mixture. It was found both experimentally and theoretically that there exists a critical filament len gth that must be exceeded so the composites will exhibit conductivity as co mposites having continuous reinforcing filaments.