Effect of fiber coating on the fatigue crack initiation and multiplication of unnotched SCS-6/Ti3Al composites

Abstract

Abstract The effect of fiber coating on the fatigue crack initiation and multiplication of an unnotched SCS-6 fiber-reinforced titanium aluminide (Ti 3 Al) matrix composite was investigated. The initiation and growth of each individual matrix crack, the evolution of matrix crack density and stiffness degradation of the composite with Ag/Ta-coated fibers were characterized quantitatively, and compared with those of the composite with uncoated fibers. The results showed that the composite with Ag/Ta-coated fibers exhibited a shorter crack initiation life, higher number of matrix cracks, and higher crack growth rate than the composite with uncoated fibers. Therefore, a higher matrix crack density and a lower residual stiffness were found in the composite with coated fibers during fatigue loading. The high interfacial cracking density and high interfacial bond strength in the Ag/Ta-coated SCS-6/Ti 3 Al composite is believed to be responsible for its poor fatigue damage resistance. Finally, an interface-controlled fatigue cracking model is used to predict the evolution of matrix crack density and residual stiffness of the composite under fatigue loading.