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

An experiment was designed and constructed to perform fiber pushout tests a t elevated temperatures in a controlled environment. Preliminary pushout te sts on both a pristine and a transversely fatigued SiC/Ti-6-4 composite wer e conducted in atmospheric conditions to assess the capabilities of this ap paratus and to study the interfacial behavior of SiC/Ti-6-4 at elevated tem perature. At room temperature, the force-displacement behavior for the two types of samples was similar. The frictional portion of the load-displaceme nt curve following total debond indicated that the interface could carry a greater load due to increasing friction and interlocking of the fiber and m atrix surfaces. At 400 degrees C, significant changes in the load-displacem ent pushout curves were observed. At this elevated temperature, the interfa cial friction produced by radial clamping was significantly reduced due to the relaxation of residual stresses, and significantly lower forces were re quired for pushout. The peak load for pushout of the fatigued samples at 40 0 degrees C was almost negligible, indicating that the fiber-matrix bond wa s broken by the fatigue loading. Due to varying compliance in the test fixt ure, it was not possible to identify progressive debonding. (C) 1999 Kluwer Academic Publishers.