Tensile behavior of unidirectional and cross-ply ceramic matrix composites

• Main Author: Herrmann, Rebecca K.
• Other Authors: Materials Science and Engineering
• Format: Others
• Language: en
• Published: Virginia Tech 2014
• Subjects: ceramics; composites; Classical Lamination Theory; fracture mirrors; LD5655.V855 1996.H477
• Online Access: http://hdl.handle.net/10919/44954; http://scholar.lib.vt.edu/theses/available/etd-10012008-063030/

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. <p>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. === Master of Science