Effects of Machining on the Uniaxial and Equibiaxial Flexure Strength of CAP3 AD-995 Al2O3

Abstract

The effect of surface condition on the uniaxial and equibiaxial flexure strength of CoorsTek's CAP3 AD-995 alumina was examined. (Note that this material was found not to be the same as CoorsTek's AD-955 alumina-a comparison and discussion of the differences are provided in this report.) The following four surface conditions were considered: as-fired (i.e., unmachined) surfaces; the condition produced by CoorsTek's standard surface-grinding procedures (i.e., the condition they will provide on tiles unless otherwise specified); the condition resulting from uniaxial surface grinding with 320-grit diamond machining (i.e., that surface machining method specified for ASTM C1161-94 ceramic flexure bars); and rotary surface grinding with 320-grit diamond machining. Equibiaxial flexure strengths were ~20% less than uniaxial flexure strengths for all of the four investigated surface conditions. This amount correlates very well with predicted strength-size scaling between the two geometries using the Weibull theory. Because this failure stress is lower, and probably more representative of on-center ballistic loading of ceramic tiles, its use is conservative and perhaps better suited as input for ballistic models that consider such deflections. The results from this study show that machining practices can be employed to increase flexure strength which may have beneficial ramifications on ballistic performance. Issues of flexure-strength dependence on surface conditioning are likely to be more relevant under certain combinations of the tile thickness and impact load. Similar testing should be conducted on the stronger, finer-grained SiC armor ceramics, since the affect of machining on flexure strength may be more pronounced.

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Document Details

Document Type
Technical Report
Publication Date
Sep 01, 2005
Accession Number
ADA441313

Entities

People

  • Andrew A Wereszczak
  • Jeffrey J. Swab
  • Reuben H Kraft

Organizations

  • United States Army Research Laboratory

Tags

Communities of Interest

  • Energy and Power Technologies
  • Human Systems
  • Space
  • Weapons Technologies

DTIC Thesaurus Topics

  • Ceramic Materials
  • Composite Materials
  • Elastic Properties
  • Failure Mode And Effect Analysis
  • Geometry
  • Materials
  • Materials Processing
  • Materials Science
  • Materials Testing
  • Mechanical Working
  • Military Research
  • Modulus Of Elasticity
  • Standards
  • Surface Properties
  • Technical Ceramics
  • Test Methods
  • Two Dimensional

Readers

  • Manufacturing Engineering.
  • Powder metallurgy of Titanium alloys.
  • Surface Coatings Technology.