Environmental effects on elevated temperature subcritical crack growth of SiC/SiC composites.

摘要

Time-dependent crack growth measurements of ceramic composites in varying environments were conducted on materials consisting of chemical vapor infiltrated SiC reinforced with Nicalon fibers having C-interfaces. Crack velocities are determined as a function of applied stress intensity and time for varying O(sub 2) levels. Results are presented for crack velocity/stress intensity relationships in pure Ar and in Ar plus 2000-, 5000-, 10,000-, and 20,000-ppM O(sub 2) atmospheres at 1100C. A 2D micromechanics model is used to represent the time-dependence of observed crack bridging events and to rationalize the observed phenomena.