Title page for ETD etd-10012008-063030
|Type of Document
||Herrmann, Rebecca K.
||Tensile behavior of unidirectional and cross-ply ceramic matrix composites
||Master of Science
||Materials Science and Engineering
|Kampe, Stephen L.
|Aning, Alexander O.
|Curtin, William A. Jr.
|Hirschfeld, Deidre A.
- Classical Lamination Theory
- fracture mirrors
|Date of Defense
The tensile behavior of two ceramic matrix composites (CMC's) was observed.
The materials of interest in this study were a glass-ceramic matrix composite (GCMC)
reinforced with Nicalon fibers and a BlackglasTM composite also reinforced with Nicalon
fibers. Both had a symmetric cross-ply layup. Initial observations of the composites
showed significant porosity and some cracking in the Blackglas™ samples. The GCMC
samples showed considerably less damage. From the observed tensile behavior of the
cross-ply composites, a 'back-out' factor for determining the 0° ply data of the composite
was calculated using Classical Lamination Theory (CLT). The predicted behavior of the
0° ply was then compared to actual data supplied by McDonnell Douglas Corporation.
While the Blackglas™ material showed good correlation, the GCMC did not. Analysis
indicates that the applicability of this technique is strongly influenced by the initial
microstructure of the composite, i.e., porosity, cracking.
Fracture mirror measurements were also observed to determine the in-situ strength
of the Nicalon fibers. Resulting characteristic strength and Weibull modulus values
combined with measured fiber pullout lengths were then used to determine material
parameters such as the ultimate tensile strength, strain to failure, work of pullout, sliding
distance at the characteristic strength, and interfacial shear stress. Comparisons of
measured and calculated ultimate tensile strengths and strains to failure showed good
agreement. This research was sponsored by the Naval Surface Warfare Center (NSWC)
in Dahlgren VA.
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