Effect of dispersion and alignment of graphite fibers on thermal expansion induced fracture of graphite fiber/copper composite

Abstract

To investigate the effect of the dispersion and alignment of the graphite fibers (GFs) on the thermal expansion induced fracture of GF/copper composites, composite test specimens were fabricated by the mechanical mixing, wet powder mixing, and chemical mixing (CM) methods at various GF volume fractions. The coefficient of thermal expansion (CTE) and mechanical properties of the fabricated composites were measured in the in-plane and through-plane directions, and their variations were investigated as functions of the dispersion and alignment of the GFs, which are key to reinforcement. From the measured CTE and the mechanical properties, the maximum temperature that the composite can withstand without fracture due to thermal expansion (i.e., fracture temperature) was estimated. The highest fracture temperature was observed in the in-plane direction of the composite fabricated by the CM method. Furthermore, with increasing GF volume fraction, the fracture temperature increased even though the maximum compressive strength decreased, because of the very small CTE of the composite.