Special Fixture for ASTM D6641 - Model GD6641-705

ASTM D6641 establishes a procedure for measuring the compressive strength and stiffness properties of polymer matrix composite materials using a combined loading compression (CLC) or comparable test fixture. ASTM D6641 is applicable to general flat laminates that are balanced and symmetric and contain at least one 0 percent ply.

ASTM D6641

During the testing process, compressive force is introduced into the specimen by combined end- and shear-loading. A universal testing machine can be used to test the untabbed, straightsided composite specimen of a rectangular cross section. Testing samples should be around 140 mm [5.5 in.] long and 12 mm [0.5 in.] wide, having an unsupported (gage) length of 12 mm [0.5 in.] when installed in the fixture. A gage length between 12 mm and 25 mm [1.0 in.] is acceptable, considering possible buckling conditions.

ASTM D6641 can be used to obtain the following measurements for your laminate:

  • compressive strength
  • compressive strain
  • compressive (linear or chord) modulus of elasticity
  • Poisson’s ratio in compression

Testing procedure

When testing the laminate, load-strain data should be collected until the specimen fails. Many factors can influence the compressive response during the test, including type of material, methods of material preparation and lay-up, specimen stacking sequence, specimen conditioning, specimen preparation, speed of testing, environment of testing, time at temperature, void content, and volume percent reinforcement.

It is important to remember that the ends of the test sample should be parallel to each other and perpendicular to the long axis of the coupon. Failure to carefully prep your sample can result in premature end-crushing of the specimen during loading, excessive induced bending or buckling, and even invalidation of your test.

A universal testing machine can be used for ASTM D6641. You may also consider looking into a loading compression fixture and an environmental chamber if needed. By means of our testing expertise and modular product design, we will help find the testing solution that is right for you. Give one of our application engineers a call today for help with creating the best budget and testing plan according to ASTM D6641.

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