Fiber push-out testing apparatus for elevated temperatures

A newly developed apparatus has been designed for performing fiber push-out testing on continuous fiber-reinforced composites at elevated temperatures. This test measures the force at which a fiber resists being pushed by a flat-bottomed indenter moving at a constant speed. The applied load versus time curve characterizes the fiber debonding and sliding behavior. Extending measurements to elevated temperatures required incorporating sample/indenter heating in a nonoxidizing environment. With this new apparatus, fiber push-out tests have been performed up to 1100 δC in a vacuum of 10^-6 Torr. A line-of-sight to the sample is maintained during the test which allows video monitoring of the push-out process. Results are shown for SCS-6 SiC fiber-reinforced Ti-24Al-llNb (at. %) and Ti-15V-3Cr-3Sn-3Al (at. %) matrix composites. The results are discussed in terms of residual stresses, interfacial wear, matrix ductility, and changing modes of interfacial failure. The effect of temperature-dependent interfacial wear on the interfacial roughness contribution to frictional shear stresses during fiber sliding is examined.