Theoretical models are developed to predict the nature of the elevated temperature failure behavior in composites containing bridged cracks under small-scale creep conditions both for intermittently (or quasi-statically) and continuously growing matrix cracks that are fully bridged by continuous ceramic fibers. The time-dependence (or rate-dependence) in these models arises as a result of the presence of a viscous fiber/matrix interfacial layer. Under load this layer undergoes shear flow causing time-dependent pull-out of bridging fibers from the crack surfaces. The mechanics of time-dependent bridging is combined with a failure criterion based on secondary failure in a crack-tip creep process zone. The dependence of the matrix creep crack growth rates on flaw size and crack wake parameters as well as on composite microstructure is derived. It is shown that the crack wake plays a predominant role in influencing not only the magnitude of creep crack growth rates but also the relationship of growth rates to the crack sixes. The implications of the results for elevated temperature composite component design are discussed.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:dissertations-8962 |
| Date | 01 January 1994 |
| Creators | Gwo, Tsung-Ju |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Language | English |
| Detected Language | English |
| Type | text |
| Source | Doctoral Dissertations Available from Proquest |
Page generated in 0.0157 seconds