The effect of interfacial strength on the response of Ti MMCs to single fibre push-out and transverse tensile testing

Titanium-based monofilament-reinforced composites have been subjected to single fibre tensioned push-out testing and to transverse tensile testing, at ambient and elevated temperature. The transverse loading tests were carried out on as-received and heat-treated composites. FEM modelling was carried out to predict stress/strain plots for strong and weak interfaces. The push-out testing indicated that, while normal debonding can occur under relatively small normal tensile stresses (provided the graphitic coating remains intact), there is considerable resistance to shear displacement even in the presence of a normal tensile stress. This is correlated with the transvesre testing results, which indicate that, while some interfacial debonding does occur, it is less extensive than predicted by the FEM model with the assumption of complete debonding when the normal stress becomes tensile. The behaviour of the reacted material, on the other hand, is different, with lower ductility and strength. This is apprarently due to embrittlement of the matrix and region immediately around the interface, since the heat treatment was not sufficient to consume the graphitic layer.