Shear fixture on an eXpert 2600
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ASTM D6641 | Composites | Compression Testing

ASTM D6641 is a testing specification that determines the compressive strength and stiffness of polymer matrix composite materials using a combined loading compression (CLC) test fixture. This test procedure introduces the compressive force into the specimen through combined shear end loading.

ASTM D6641 includes two procedures; Procedure A: to be used with untabbed specimens such as fabrics, chopped fiber composites, laminates with a maximum of 50% 0˚ plies and Procedure B: to be used with tabbed specimens with a higher orthotropy such as unidirectional composites. The use of tabs is necessary to increase the load-bearing area at the specimen ends. Before conducting ASTM D6641, it is important to read the entire specification in the relevant ASTM publication.

ASTM D6641 | Composites | Compression Testing

  1. Use cutting tools to carve the fabric into a rectangular shape. The longer side should be parallel to the direction that is to be tested. Drawing a line down the long segment of the textile will ease the alignment of the sample into the grips.
  2. Once the specimen is prepared, load and secure it into a pair of clamps. A Manual Vise grip would be the most appropriate fixture for this testing standard.
  3. Start moving the grips apart at the specified rate.
  4. Stop the test once the specimen breaks or ruptures.
  • Laminate Compressive Strength
  • Laminate Compressive Modulus
  • Compressive Poisson’s Ratio

ASTM D6641 | Composites | Compression Testing

ASTM D6641Recommended Equipment
Testing System
  • Combined Loading Compression (CLC) Test Fixture
  • Strain Gauges
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