ASTM D695 vs D6641 Composites Compressive Test 1

[ctan67]

We were interested in acquiring test fixtures to determine compressive properties of polymer matrix composites, and currently, two different standards have been brought to our attention.

ASTM D695/ Sacma 1R-94 and ASTM D6641-01. The advantage of D6641 is that the fixture specific to this test does not require tabbed specimens for strength tests, a potential time saver. Are there any drawbacks or limitations that I am not aware of with D6641? Does anyone have any additional information in comparison to D695?

Also, which standard is more widely accepted in the industry?

Thank you

 

[SWComposites]

More info on the D6641 test method is in a FAA report, DOT/FAA/AR-00/26, "Verification of the Combined Load
Compression (CLC) Test Method" (at one time you could download FAA Tech Center reports at actlibrary.tc.faa.gov.

The SRM1 method (a highly modified version of the D695 method) has been used in indsutry for a long time. Unfortunately it is prone to high variability unless extreme care is taken in specimen preparation and testing. The ASTM D30 Committee on Composites strongly recommends the use of the D6641 method as it has been shown to have less variability and doesn't require tabs. The only drawback is that it is not recommended for testing [0] layups of unidirectional carbon tape (though it is really no worse than the SRM1 method for uni tape).

The standard D695 test method is designed for unreinforced plastics and should never be used for fiber reinfordced composites.