Chapter 3. Techniques for Measuring Interfacial Recession in CFCC's and the Implications on Subcritical Crack Growth

Summary

Interfacial properties play a significant role in determining the mechanical response of continuous fiber reinforced, ceramic composites. Increases in fracture toughness, relative to the monolithic matrix material, and non-catas trophic failure modes are dependent on fiber matrix debonding during crack propagation. The most common method employed to promote debonding at the fiber matrix interface is to incorporate an interphase material. Unfortunately, most interphase materials are susceptible to degradation when exposed to oxidizing environments. Degradation of the interphase also degrades the composite properties and may influence the failure mode. In many cases, oxidation may result in the loss of interphase material. Development of composites with degradation-resistant interphases requires a technique to measure the extent of interphase recession. This paper will demonstrate the use of a fiber push-in technique to determine interphase recession distances for carbon interphases and will compare the relative advantages of this method with optical measurements and TGA.