Tensile fracture mechanism for SiCf(SCS-6)/Ti alloy based mono-composites

Continuous fiber reinforced titanium alloy matrix composites are attractive for structural applications such as gas turbine engines, aerospace engines, space crafts, and so on. In order to discuss the fracture process of mono-composites fabricated by titanium matrix coated on the SiC fiber (SCS-6) by PVD method, tensile test was performed for the mono-composites and the fracture surfaces and the surface of the mono-composites were examined. The SCS-6 fiber was coated by Ti-6Al-4V, IMI834, and Ti-6-2-4-2 titanium alloys. Ti-coated layer thickness on the SCS-6 fiber was about 30μm. Two types of relationship between load and displacement were observed. The one is linear relationship, and the other is non-linear relationship. For the mono-composites having the non-linear load-displacement relationship the second load-displacement curves after first unloading were the same as that for mono-composite having linear relationship. The load-displacement curves for the dissolved fiber of matrix alloys from the mono-composites had linear relationship between load-displacement. On the surface of two mono-composites having non-linear relationship many fine cracks were seen and after loaded mono-composites many cracks been extended to the interface between SiC fiber and matrix alloys and debondings were seen at the interfaces. On the other hands, on the surface having linear relationship the crack and debonding were not observed.