The effect of gamma irradiation on carbon fibre properties

Abstract Carbon fibres heat treated to temperatures in the range 1000-2600°C have been irradiated in the spent fuel pond to gamma doses between 1-1000 Megarads (MI). The mechanical properties of the irradiated fibres have been determined by single filament tests. There is a reduction in strength and modulus for fibres irradiated in air, probably due to radiation enhanced oxidation effects. This produces an increase in fibre diameter (≲10%) for fibre originally heat treated to 1000 and 1500°C. This is probably due to fine scale voidage (∼20 A) for which there is some evidence in thin sections prepared from regions close to the surface of these fibres (irradiated to 1000 Mr). The mechanical properties of fibres irradiated to 1000 Mr in argon were unaffected by the irradiation showing that the displacement damage from the irradiation has had little effect on the processes controlling modulus and strength.