Hi-Nicalon^TM Fiber-Reinforced CVI-SiC Matrix Composites: II Interfacial Shear Strength and Its Effects on the Flexural Properties

Abstract

The interfacial shear strengths (ISSs) of a series of 2D Hi-Nicalon/SiC composites with various pyrolitic carbon (PyC) or PyC-SiC multiple fiber/matrix interlayers were investigated using the single fiber pushout tests. The influence of the obtained ISS on the proportional limit stress (PLS) of the materials upon bending was discussed based on the experimental results and a thoretical model calculation. The ISS showed close PyC layer thickness dependence. The ISS decreased quickly from 505 MPa to ∼ 100 MPa with increasing the PyC layer thickness up to ∼ 200 nm, beyond which slight decrease of the ISS occurred till 760 nm of the PyC layer. The ISS showed significant influence on the PLS. Good agreement between the model calculations and the experimental results was obtained, when correlating the PLS to the ISS. The comparison between the model calculation and the experimental results may be indicative on further efforts on further improvement of the mechanical performance of SiC/SiC composites.