EFFECT OF CVD-BN COATING ON MECHANICAL-PROPERTIES OF CONTINUOUS SILICON-CARBIDE FIBER

Toughness of ceramic-matrix composites can be optimized through coatin gs the reinforcing fibers. Chemical vapor deposition (CVD) process is a key technology for fiber coatings. The mechanical properties of cont inuous silicon carbide fibers (Hi-Nicalon) have been studied as a func tion of the thickness of the pyrolytic boron nitride (P-BN) coating by CVD process. The compressive residual stress at the P-BN coating laye r decreases slightly with increasing the coating thickness. It is cons idered that, with including the residual stress effect, cracking of th e P-BN coating layer occurs first in a monotonic tensile fracture test , In addition no degradation of the silicon carbide-fiber in ultimate tensile strength is observed regardless of the P-BN coating thickness.