Effect of CVD-BN coating on mechanical properties of continuous silicon carbide fiber

Toughness of ceramic-matrix composites can be optimized through coatings the reinforcing fibers. Chemical vapor deposition (CVD) process is a key technology for fiber coatings. The mechanical properties of continuous silicon carbide fibers (Hi-Nicalon) have been studied as a function of the thickness of the pyrolytic boron nitride (P-BN) coating by CVD process. The compressive residual stress at the P-BN coating layer decreases slightly with increasing the coating thickness. It is considered that, with including the residual stress effect, cracking of the 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.