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ASTM D638 Overview | Plastics and Elastomers | Tension Testing

ASTM D638 is one of the most common plastic strength specifications and covers the tensile properties of unreinforced and reinforced plastics.  This test method uses standard “dogbone” shaped specimens under 14mm of thickness.  A universal testing machine (tensile testing machine) is needed to perform this test. Prior to conducting ASTM D638, it is important to read the entire specification in the relevant ASTM publication.

First off, do not perform this test if you have films or elastomers. If you have film under 1mm in thickness use ASTM D882. If you have an elastomer use ASTM D412.

General Overview | How to perform ASTM D638?

  1. To perform ASTM D638, begin by cutting your material into a “dogbone” sample.
  2. Load the sample into a pair of tensile grips and attach your extensometer (if required).
  3. The speed at which you separate your tensile grips depends on the shape of the specimen and can range from 0.05-20 inches per minute.  End the test at sample break (rupture).

Sample Geometries

  • ASTM D638 Type I
  • ASTM D638 Type II
  • ASTM D638 Type III
  • ASTM D638 Type IV
  • ASTM D638 Type V

What results are calculated from ASTM D638?

  • Tensile Strength
  • Elongation at Yield
  • Elongation at Break
  • Nominal Strain at Break (Grip Separation)
  • Modulus of Elasticity
  • Secant Modulus
  • Poisson’s Ratio (Requires Transverse Extensometer)

ASTM D638 System and Fixture Gallery

Recommended Equipment for ASTM D638

ASTM D638 Recommended Equipment
Testing System
Fixturing
Accessories
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