Fatigue behaviour of duplex metal coated SiC fibre reinforced Ti-15-3 matrix composites

Duplex metal (Cu/Mo and Cu/W) coated SiC(SCS-6) fibre reinforced Ti-15-3 ma trix composites have been prepared using a hot isostatic pressing process. The effect of the duplex metal coatings on the fatigue behaviour of unnotch ed SiC(SCS-6) fibre reinforced Ti-15-3 matrix composite has been studied. T he fatigue resistance of this fibre reinforced composite is improved by use of the duplex metal coatings. The Cu/Mo and Cu/W duplex metal coating laye rs prevent debonding of the SCS coating layer from the SiC fibre surface, t hus also effectively preventing a reduction in strength of the fibre. Durin g the fatigue test, fibre bridging behind the matrix crack tip reduces the crack growth rate of the matrix; this mechanism is difficult to achieve wit h the pristine fibre composite. Evolution of the fatigue damage can be quan titatively evaluated by means of a fatigue damage parameter. Matrix crack p ropagation is the dominant factor responsible for the increase in damage pa rameter of the composites.