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Title: Internal strain analysis of ceramics using scanning laser acoustic microscopy. Final report

Abstract

Quantitative studies of material behavior characteristics are essential for predicting the functionality of a material under its operating conditions. A nonintrusive methodology for measuring the in situ strain of small dimeter (to 11 microns) ceramic fibers under uniaxial tensile loading and the local internal strains of ceramics and ceramic composites under flexural loading is introduced. The strain measurements and experimentally observed mechanical behavior are analyzed in terms of the microstructural development and fracture behavior of each test specimen evaluated. Measurement and analysis of Nicalon silicon carbide (SiC) fiber (15 microns diameter) indicate that the mean elastic modulus of the individual fiber is 185.3 GPa. Deviations observed in the experimentally determined elastic modulus values between specimens were attributed to microstructural variations which occur during processing. Corresponding variations in the fracture surface morphology were also observed. The observed local mechanical behavior of a lithium alumino-silicate (LAS) glass ceramic, a LAS/SiC monofilament composite, and a calcium alumino-silicate (CAS)/SiC fully reinforced composite exhibits nonlinearities and apparent hysteresis due to the subcritical mechanical loading. Local hysteresis in the LAS matrices coincided with the occurrence of multiple fracture initiation sites, localized microcracking, and secondary cracking. The observed microcracking phenomenon was attributed to stress relaxation of residualmore » stresses developed during processing, and local interaction of the crack front with the microstructure. The relaxation strain and stress predicted on apparent mechanical hysteresis effects were defined and correlated with the magnitude of the measured fracture stress for each specimen studied. This quantitative correlation indicated a repeatable measure of the stress at which matrix microcracking occurred for stress relief of each material system.« less

Authors:
Publication Date:
Research Org.:
Dayton Univ., OH (United States)
OSTI Identifier:
6326032
Report Number(s):
N-93-25451; NASA-CR-191118; E-7308; NAS-1.26:191118
CNN: NCC3-81; RTOP 510-01-50
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CERAMICS; FRACTURE PROPERTIES; REINFORCED MATERIALS; ALUMINIUM SILICATES; CALCIUM; COMPOSITE MATERIALS; CRACK PROPAGATION; FIBERS; GLASS; HYSTERESIS; LITHIUM; MICROSTRUCTURE; SILICON CARBIDES; STRAINS; STRESS RELAXATION; ALKALI METALS; ALKALINE EARTH METALS; ALUMINIUM COMPOUNDS; CARBIDES; CARBON COMPOUNDS; ELEMENTS; MATERIALS; MECHANICAL PROPERTIES; METALS; OXYGEN COMPOUNDS; RELAXATION; SILICATES; SILICON COMPOUNDS; 360203* - Ceramics, Cermets, & Refractories- Mechanical Properties; 360603 - Materials- Properties

Citation Formats

Kent, R M. Internal strain analysis of ceramics using scanning laser acoustic microscopy. Final report. United States: N. p., 1993. Web.
Kent, R M. Internal strain analysis of ceramics using scanning laser acoustic microscopy. Final report. United States.
Kent, R M. Mon . "Internal strain analysis of ceramics using scanning laser acoustic microscopy. Final report". United States.
@article{osti_6326032,
title = {Internal strain analysis of ceramics using scanning laser acoustic microscopy. Final report},
author = {Kent, R M},
abstractNote = {Quantitative studies of material behavior characteristics are essential for predicting the functionality of a material under its operating conditions. A nonintrusive methodology for measuring the in situ strain of small dimeter (to 11 microns) ceramic fibers under uniaxial tensile loading and the local internal strains of ceramics and ceramic composites under flexural loading is introduced. The strain measurements and experimentally observed mechanical behavior are analyzed in terms of the microstructural development and fracture behavior of each test specimen evaluated. Measurement and analysis of Nicalon silicon carbide (SiC) fiber (15 microns diameter) indicate that the mean elastic modulus of the individual fiber is 185.3 GPa. Deviations observed in the experimentally determined elastic modulus values between specimens were attributed to microstructural variations which occur during processing. Corresponding variations in the fracture surface morphology were also observed. The observed local mechanical behavior of a lithium alumino-silicate (LAS) glass ceramic, a LAS/SiC monofilament composite, and a calcium alumino-silicate (CAS)/SiC fully reinforced composite exhibits nonlinearities and apparent hysteresis due to the subcritical mechanical loading. Local hysteresis in the LAS matrices coincided with the occurrence of multiple fracture initiation sites, localized microcracking, and secondary cracking. The observed microcracking phenomenon was attributed to stress relaxation of residual stresses developed during processing, and local interaction of the crack front with the microstructure. The relaxation strain and stress predicted on apparent mechanical hysteresis effects were defined and correlated with the magnitude of the measured fracture stress for each specimen studied. This quantitative correlation indicated a repeatable measure of the stress at which matrix microcracking occurred for stress relief of each material system.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1993},
month = {3}
}

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