THE ROLE OF FIBER COATING ON SIC FIBER-REINFORCED ALUMINA COMPOSITE

The effect of fiber coating on the residual thermal stresses, interface, and mechanical properties of CVD-(C, SiC) coated Nicalon fiber-reinforced alumina matrix composite were studied. Using a tri-cylindrical model, the residual thermal stresses caused by the mismatch of their thermal expansion coefficients and the mechanical behavior were calculated. The results indicated that when the fibers coated with carbon, which has lower Young's modulus, the residual thermal stresses at fiber-coating interface and coating-matrix interface were reduced compared with uncoated fiber reinforced composite materials, and these stresses decrease with increase in the thickness of carbon coating. In the CVD-(C,SiC) coated fiber-reinforced alumina composite, the reduction of the residual interfacial stress decreased the shear strength required for fiber pullout, so that the work of fracture was increased compared with that of uncoated Nicalon fiber-reinforced alumina composite.