Stress relaxation in discontinuously reinforced composites

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It has been observed that in discontinuously-reinforced Al{sub 2}0{sub 3}/NiAl composites that as the reinforcement size increases the average density of dislocations generated from the relaxation of the thermal stresses increases, and the corresponding thermal residual stresses slightly decrease. Similar changes result when the reinforcement morphology changes from spheres to short fibers to continuous filaments. The changes of dislocation density and thermal residual stresses with respect to particle size are in contrast to those observed in the SiC/Al counterpart A previously developed simple model used to explain the SiC/Al data, which was based on prismatic dislocation punching, suggested that the ... continued below

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12 p.

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Shi, N. & Arsenault, R.J. May 1, 1995.

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  • Shi, N. Los Alamos National Lab., NM (United States)
  • Arsenault, R.J. Univ. of Maryland, College Park, MD (United States). Dept. of Materials and Nuclear Engineering

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Description

It has been observed that in discontinuously-reinforced Al{sub 2}0{sub 3}/NiAl composites that as the reinforcement size increases the average density of dislocations generated from the relaxation of the thermal stresses increases, and the corresponding thermal residual stresses slightly decrease. Similar changes result when the reinforcement morphology changes from spheres to short fibers to continuous filaments. The changes of dislocation density and thermal residual stresses with respect to particle size are in contrast to those observed in the SiC/Al counterpart A previously developed simple model used to explain the SiC/Al data, which was based on prismatic dislocation punching, suggested that the density of the misfit dislocations decreases when the reinforcement size increases. In this investigation, a simple model is proposed to explain the anomaly in the development of thermal residual stresses and the generation of misfit dislocations as a function of the particle size and shape in Al{sub 2}0{sub 3}/NiAl composites. As a result of a lack of sufficient independent-slip-systems in low symmetry materials such as NiAl, plastic relaxation of the thermal stresses is severely constrained as compared to fcc Al. As such, plastic relaxation requires collaborative slips in an aggregate of grains. This only occurs when the length scale of the varying misfit thermal stress field is much larger than the average grain size. That is, the mechanism of plastic relaxation becomes operative when the reinforcement size increases.

Physical Description

12 p.

Notes

OSTI as DE95010928

Source

  • Micromechanics and constitutive modeling of composite materials, Los Angeles, CA (United States), 28-30 Jun 1995

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  • Other: DE95010928
  • Report No.: LA-UR--95-1168
  • Report No.: CONF-9506181--1
  • Grant Number: W-7405-ENG-36
  • Office of Scientific & Technical Information Report Number: 70790
  • Archival Resource Key: ark:/67531/metadc712125

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Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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Creation Date

  • May 1, 1995

Added to The UNT Digital Library

  • Sept. 12, 2015, 6:31 a.m.

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  • June 23, 2016, 10:35 a.m.

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Shi, N. & Arsenault, R.J. Stress relaxation in discontinuously reinforced composites, article, May 1, 1995; New Mexico. (digital.library.unt.edu/ark:/67531/metadc712125/: accessed January 17, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.