High temperature fiber pushout of pristine and transversely fatigued SiC/Ti-6-4

An experiment was designed and constructed to perform fiber pushout tests at elevated temperatures in a controlled environment. Preliminary pushout tests on both a pristine and a transversely fatigued SiC/Ti-6-4 composite were conducted in atmospheric conditions to assess the capabilities of this apparatus and to study the interfacial behavior of SiC/Ti-6-4 at elevated temperature. At room temperature, the force-displacement behavior for the two types of samples was similar. The frictional portion of the load-displacement curve following total debond indicated that the interface could carry a greater load due to increasing friction and interlocking of the fiber and matrix surfaces. At 400 degrees C, significant changes in the load-displacement pushout curves were observed. At this elevated temperature, the interfacial friction produced by radial clamping was significantly reduced due to the relaxation of residual stresses, and significantly lower forces were required for pushout. The peak load for pushout of the fatigued samples at 400 degrees C was almost negligible, indicating that the fiber-matrix bond was broken by the fatigue loading. Due to varying compliance in the test fixture, it was not possible to identify progressive debonding. (C) 1999 Kluwer Academic Publishers.