Robust Fiber Coatings
Abstract
The highly desired ceramic matrix composite is the one in which the high strength and strain-to-failure is achieved through judicious selection of a fiber coating that can survive the high-temperature oxidizing use environment that is envisioned for these engineered structural materials. Scheelite (CaWO4) had been identified as a promising oxidation-resistant fiber coating, but its functionality within a CMC having a dense matrix had remained to be proven. The objective of this program was to verify that scheelite coatings provide for high strains-to- failure, nonlinearity in the stress-strain curves and the corresponding fiber pullout expected in CMC fracture. It was important under this program to evaluate CMCs with as high of a matrix density as possible to insure that the fiber coating was duly tested rather than having the fracture behavior being influenced by damage of a weak matrix phase, typical for the porous matrix class of CMCs. Nextel 610 alumina fibers were chosen as the reinforcement because of its higher strength compared to the Nextel 720 mullite-alumina fiber that is also a candidate for scheelite coatings. Unidirectional CMC were fabricated and tested throughout the program to examine the functionality of the scheelite coatings.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 2002
- Accession Number
- ADA407946
Entities
People
- Richard W. Goettler