ASTM D6641/D6641M-01e1

This test method is designed to produce compressive property data for material specifications, research and development, quality assurance, and structural design and analysis. When specific laminates are tested (primarily of the [90/0]_ns family, although other laminates containing a maximum of 50 % 0° plies can be used), the data are frequently used to “back out” 0° ply strength, using laminate theory to calculate a 0° unidirectional lamina strength (1, 2). Factors that influence the compressive response include: type of material, methods of material preparation and lay-up, specimen stacking sequence, specimen preparation, specimen conditioning, environment of testing, speed of testing, time at temperature, void content, and volume percent reinforcement. Laminate properties, in the test direction, that may be obtained from this test method include:

5.1.1 Ultimate compressive strength,

5.1.2 Ultimate compressive strain,

5.1.3 Compressive (linear or chord) modulus of elasticity, and

5.1.4 Poisson’ratio in compression.

1.1 This test method establishes a procedure for determining the compressive strength and stiffness properties of polymer matrix composite materials using a combined loading compression (CLC) (1) or comparable test fixture. This test method is applicable to general flat laminates that are balanced and symmetric and contain at least one 0^o ply. The standard specimen is untabbed, and, thus, for strength determination, the laminate is limited to a maximum of 50 % 0^o plies, or equivalent (see 6.4).

1.2 The compressive force is introduced into the specimen by combined end- and shear-loading. In comparison, Test Method D3410/D3410M is a pure shear-loading compression test method and Test Method D695 is a pure end-loading test method.

1.3 Unidirectional (0^o ply orientation) composites can be tested to determine unidirectional composite modulus and Poisson's ratio, but not compressive strength.

1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the test the inch-pound units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.

Note 1--Additional procedures for determining the compressive properties of polymer matrix composites may be found in Test Methods D3410/D3410M, D5467, and D695.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.