Evaluation of the interfacial mechanical properties of fiber reinforced boron nitride matrix composites

Micro-indentation push-in and push-out techniques were used to evaluate the mechanical character of the fiber-matrix interface in boron nitride matrix composites derived from borazine oligomers. Specimens containing various ceramic fibers (including Nicalon^TM, carbon coated Nicalon^TM, PAN-based carbon, and pitch-based carbon) were examined. Fiber sliding was observed with the carbon coated Nicalon fibers (C-Nicalon). For this composite system, the debonding strength, residual axial fiber stress and interfacial friction stress were determined. Auger Electron Spectroscopy was used to compare the interfacial chemistry in the Nicalon and C-Nicalon systems. The carbon fiber/boron nitride matrix composites exhibited superior strengths to the Nicalon and carbon coated Nicalon composites. However, the preliminary micro-indentation analysis did not provide any basis for distinguishing this behavior.