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ASTM D6272 | Plastics and Elastomers | Bend Testing

ASTM D6272 is a testing specification that determines the flexural properties of unreinforced and reinforced rigid and semi rigid plastics. A bar of rectangular cross section is mounted on a four point bend fixture and is loaded at two points. The specimen is deflected until failure or until maximum fiber strain of 5% is reached.

Flexural properties vary with factors such as specimen depth, temperature and the difference in rate of straining. This test method covers two procedures:

  • Procedure A: Designed for materials that break at comparatively small deflections and used for measuring the flexural modulus.
  • Procedure B: Designed for materials that undergo large deflections during testing and used for measuring the flexural strength.

Results from each procedure should not generally be expected to yield comparable results due to difference in rate of straining. Before conducting ASTM D6272, it is important to read the entire specification in the relevant ASTM publication.

ASTM D6272 | Plastics and Elastomers | Bend Testing

Test Procedure A

  1. Prepare at least five specimens as specified by the standard. For all tests the support span must be 16 times the depth of the beam.
  2. Measure and record the specimen dimensions at the center of the support span.
  3. Rate of crosshead displacement (R) must be calculated using the equations in the standard.
  4. Mount the specimen on the four point bend fixture, making sure it is centered on the supports.
  5. Apply flexural load at calculated crosshead displacement rate (R). Monitor the load-deflection data.
  6. Stop the test at specimen break. If no break occurs by the time the maximum strain has reached 0.05 mm/min, discontinue the test.

Test Procedure B

  1. Prepare the specimens as described in Procedure A, above.
  2. Set the rate of straining as specified by the standard.
  3. Mount the specimen on the four point bend fixture, making sure it is centered on the supports.
  4. Apply flexural load. Monitor the load-deflection data.
  5. Stop the test at specimen break. If no break occurs by the time the maximum strain has reached 0.05 mm/min, discontinue the test.
Calculations:
  • Maximum Fiber Stress
  • Flexural Strength
  • Flexural Yield Strength
  • Flexural Offset Yield Strength
  • Stress at a Given Strain
  • Maximum Strain
  • Tangent Modulus of Elasticity
  • Secant Modulus of Elasticity

ASTM D6272 | Plastics and Elastomers | Bend Testing

ASTM D6272 Recommended Equipment
Testing System
Fixturing
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