Date of Award

12-1993

Document Type

Thesis

Degree Name

Master of Science in Aeronautical Engineering

Department

Department of Aeronautics and Astronautics

First Advisor

Shankar Mall, PhD

Abstract

This research, the first load-controlled tension-compression fatigue testing to be performed on a MMC, extends the existing knowledge of MMC fatigue damage mechanisms to include the tension compression loading condition. To accomplish this, a (0/90)2, SCS-6/Ti-15-3 laminate was subjected to tension- tension fatigue at room temperature, and tension-compression fatigue at both room temperature and 427°C. Stress and strain data was taken to evaluate the macro-mechanic behavior of the material. Microscopy and fractography were performed to characterize the damage on a micro-mechanic level. On a maximum applied stress basis, the room temperature tension-tension specimens had longer fatigue lives than the room temperature tension-compression specimens. The room and high temperature tension-compression fatigue lives were nearly identical in the fiber-dominated high stress region of the SN curve. However, the increased ductility and diffused plasticity of the titanium matrix at 427°C delayed the onset and severity of matrix cracking, and thus increased the elevated temperature fatigue lives in the matrix dominated region of the SN curve. In all cases, matrix damage initiated at reaction zone cracks which nucleated both matrix plasticity and matrix cracking.

AFIT Designator

AFIT-GAE-ENY-93D-6

DTIC Accession Number

ADA273731

Comments

The author's Vita page is omitted.

Download

Share

COinS