Chapter 42. Creep Lifetime Predictions on Continuous-Fiber-Reinforced Ceramic Composites
- John B. Wachtman Jr.
Published Online: 28 MAR 2008
Copyright © 1993 The American Ceramic Society
Proceedings of the 17th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 14, Issue 7/8
How to Cite
Chuang, T.-J. (1993) Creep Lifetime Predictions on Continuous-Fiber-Reinforced Ceramic Composites, in Proceedings of the 17th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 14, Issue 7/8 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470314180.ch42
- Published Online: 28 MAR 2008
- Published Print: 1 JAN 1993
Print ISBN: 9780470375266
Online ISBN: 9780470314180
- fiber-reinforced ceramic composites;
- aerospace applications;
- 2-D model;
Because of their high strength and toughness at elevated temperatures, continuous fiber-reinforced ceramic composites (e.g., SiCf/SiC, SiCf/Si3N4) have become the potential candidates for the next generation of turbine engine materials for aerospace applications. A generic model is proposed here for the estimation of service life of this class of materials subjected to long-term creep rupture conditions. This 2-D model consists of interfacial cracks growing along fiber/matrix interfaces and grain boundaries within the polycrystalline fibers in the direction normal to the principal tensile stress axis. Neglecting the transient effects, total lifetime is derived based on the criterion that rupture is due to coalescence of adjacent cracks. It is found that lifetime is inversely proportional to crack growth rate, volume fraction, and aspect ratio of the fibers in a nonlinear fashion, but is extremely sensitive to the applied stress owing to the high exponent of stress in the v-K law. The functional dependence of the predicted lifetime on the temperature and stress will be used to compare with data on a set of continuous SiC-fiber-reinforced Si3N4 matrix composites with varying volume fractions of fibers creep tested at 1200°C in air. Further, TEM performed on the postcrept specimens revealed that creep damage is predominantly in the form of microcracks at matrix/matrix within the fibers and fiber/matrix interfaces, approximately in accord with the model simulation.