Behaviour of carbon fibre reinforced AI–Si composites after thermal exposure

Abstract

The behaviour of high modulus carbon fibre reinforced Al–Si composites after thermal exposure at 773 K for various times has been investigated. The composites were fabricated via hybridisation of a small volume fraction of SiC particles using a pressure casting process. The longitudinal tensile strength (LTS) of the composites increased to a maximum of 899 MN m⁻² when exposed for 216 h, then decreased as the exposure continued. The transverse tensile strength (TTS) of the composites increased monotonically with increasing treatment time, suggesting that interfacial bond strength was improved by the thermal exposure. It was found that fibre pull-out played an important role in the LTS of the composites and that moderate fibre pull-out resulted in higher values of LTS. The results of single fibre tensile tests show that long term thermal exposure at 773 K only slightly degraded the fibres compared with the fibres in the as cast composites. The fibre pull-out behaviour and the microstructural observations of the fibre surfaces gave some evidence that chemical interactions occurred in the fibre/matrix interfaces.

MST/1528