Date of Award


Document Type


Degree Name

Master of Science in Aeronautical Engineering


Department of Aeronautics and Astronautics

First Advisor

Shankar Mall, PhD


This study investigated the notched and unnotched macromechanical response due to micromechanical behavior of [0/±45/90]S SCS-6/β 21 S and [0/90] 2S Sigma/β 21S subjected to static compressive loads at room temperature. The stress-strain behavior and mechanical response in the presence of a circular hole was examined. A clear description of the progressive nature of damage, which ultimately resulted in failure, was provided. The effect of elevated temperature was shown for SCS-6/β 21S. The ultimate compressive strength and elastic modulus were reported for both MMCs. Sigma/β 21S and SCS-6/β 21S were mildly notch sensitive at room temperature. Notch sensitivity of SCS-6/β 21S was slightly reduced at 650°C. Internal failure mechanisms of fiber debonding, matrix cracking, matrix yielding, fiber failure, and fiber microbuckling were observed in various combinations during the loading. Damage mechanisms were observed similarly in notched and unnotched specimens. Damage initiation in the notched specimens was concentrated in the region adjacent to the hole. Sigma/β 21S and unnotched SCS-6/β 21S at room temperature failed in an extensional mode, while notched SCS-6/β 21S and unnotched SCS-6/β 21S at 650°C failed in a shear mode. The ultimate compressive failure of each depended on the ultimate strength of the fibers.

AFIT Designator


DTIC Accession Number



The author's Vita page is omitted.