Date of Award

12-1991

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Aeronautics and Astronautics

First Advisor

Shankar Mall, PhD

Abstract

Static tensile testing conducted at room temperature and 650 C shows notch sensitivity for a quasi-isotropic lay-up of a titanium alloy metal matrix composite. The specific material used was SCS-6/Beta 21S. Some unnotched specimens were tested and then the diameter-to-width ratio was varied from 0.1 to 0.4. The room temperature unnotched strength is 840 MPa, and the strength falls to less than half this value at 650 C. The off-axis plies of the (0, + or - 45, 90)s lay-up exhibit debonding of the fibers from the matrix at only ten percent of failure stress. This debonding is shown with acetate replicas and acoustic emission. By modeling the debonded plies with the Halpin-Tsai equations, a modulus is calculated for the debonded material which correlates very well with the experimental modulus. A fiber dominated failure exists at both temperatures, but the fiber pullout exists only at 650 C. Etching away the matrix from the 0 fibers showed a small area near the hole where fibers were damaged. The size of this damage zone correlated very well with the critical distance for the Whitney-Nuismer Point Stress failure prediction method.

AFIT Designator

AFIT-GAE-ENY-91D-24

DTIC Accession Number

ADA243894

Comments

The author's Vita page is omitted.

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