Thermal expansion behaviour of unidirectional carbon-fibre-reinforced copper-matrix composites

Continuous carbon-fibre-reinforced copper-matrix composites prepared by diffusion bonding technology have been used for investigation of the coefficient of thermal expansion. For reasons of economy and ease of availability, continuous Torayca T300 fibres have been used for sample preparation. They were coated continuously with copper (galvanically and then chemically) and unidirectional composites were prepared by diffusion bonding in vacuum at 873 K for 30 min. The linear coefficient of thermal expansion (CTE) of samples with different volume fractions of carbon fibres was measured in directions parallel and perpendicular to the fibre direction. The samples were heat-treated for one temperature cycle in the range 293–573 K or cycled three times in a temperature range from 253 to 573 K. Measured CTE values are compared with those predicted by the well-known Schapery model and the model derived by Kural and Min. Better agreement was achieved with the predictions of the longitudinal CTE of the composite. Prediction of the transverse CTE was more difficult because of a lack of knowledge of the transverse CTE of carbon fibres. Models including the transverse CTE of carbon fibres (Kural–Min) gave better results for prediction of the transverse CTE of the unidirectional composite.