ELASTIC-MODULI, THERMAL-EXPANSION AND MICROSTRUCTURE OF COPPER-MATRIXCOMPOSITE REINFORCED BY CONTINUOUS GRAPHITE FIBERS

Copper-matrix composites reinforced by continuous graphite fibres (C(g )) were processed by hot-pressing layers of metallic prepregs, each fi bre within the yarns having previously been coated with copper by elec troplating. The electrodeposition and consolidation conditions were op timized to minimize the residual porosity, which could be considered a s negligible. One-dimensional (1 D) and two-dimensional composites wer e obtained by this technique. In addition to the good metallurgical qu ality of the matrix, examination of the fibre/matrix interphase by Aug er electron spectroscopy confirmed the excellent chemical compatibilit y between copper and graphite. As a consequence, the ultimate tensile strength of fibres extracted from the matrix remained nearly unchanged . The thermal expansion coefficients of 1 D C(g)/Cu composite material s were determined between 100 and 300-degrees-C, along the two orthogo nal directions. Values ranging from 8 to 9 x 10(-6)degrees-C-1 in the composite plane and from 16 to 18 X 10(-6)-degrees-C-1 in the orthogon al direction were obtained. These results, which are related to the st rong anisotropy of the ex-pitch graphite fibre, are correlated to the theoretical values found with the rule of mixtures. The poor Young's m odulus and the tensile strength values are correlated to the microstru cture of the fibre/matrix interphase.