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 stuidy investigates the fatigue response of a cross-ply [0/90]2s Nicalon/Calcium Aluminosillicate (Nicalcc/CAS) ceramic matrix composite at room temperature under strain controlled tension-tension and tension-compression fatigue loading. The primary objectives were to determine strain fatigue limits for both loading cases and to complete a fatigue life diagram (Δe-N) for all tests. Failure mechanisms were also studied. The average initial modulus value for this lay-up was 120 GPa. The ultimate tensile strain was 0.00988 mn/mm (285 MPa). Eight tests were conducted with maximum strains that ranged from 0.00300 mm/mm to 0.00722 mm/mm. The tension-tension fatigue limit was found to be Δe=0.00270 mm/mm. There was no evidence of random fiber failure. Five tension-compression tests were performed at maximum strains that ranged from 0.00135 mm/mm to 0.00325 mm/mm. The fatigue limit for this set of tests was found to be the same as that fatigue limit for the tension-tension tests, Δe=0.00270 mm/mm. Longitudinal cracks formed in all the specimens and were the major cause of failure. The fatigue life diagram for these tests coincided with the tension-tension tests until at the higher strains where the failure mode changed from tensile failure to compressive failure.

AFIT Designator

AFIT-GAE-ENY-93D-17

DTIC Accession Number

ADA275374

Comments

The author's Vita page is omitted.

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