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.

Related Standards

  • ASTM D695 Test Method for Compressive Properties of Rigid Plastics
  • ASTM D883 Terminology Relating to Plastics
  • ASTM D3410/D3410M Test Method for Compressive Properties of Polymer Matrix Composite Materials with Unsupported Gage Section by Shear Loading
  • ASTM D3878 Terminology for Composite Materials
  • ASTM D5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite Materials
  • ASTM D5379/D5379M Test Method for Shear Properties of Composite Materials by the V-Notched Beam Method
  • ASTM D5467/D5467M Test Method for Compressive Properties of Unidirectional Polymer Matrix Composite Materials Using a Sandwich Beam
  • ASTM D5687/D5687M Guide for Preparation of Flat Composite Panels with Processing Guidelines for Specimen Preparation
  • ASTM E4 Practices for Force Verification of Testing Machines
  • ASTM E6 Terminology Relating to Methods of Mechanical Testing
  • ASTM E122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot or Process
  • ASTM E132 Test Method for Poissons Ratio at Room Temperature
  • ASTM E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
  • ASTM E456 Terminology Relating to Quality and Statistics
  • ASTM E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
  • ASTM E1309 Guide for Identification of Fiber-Reinforced Polymer-Matrix Composite Materials in Databases
  • ASTM E1434 Guide for Recording Mechanical Test Data of Fiber-Reinforced Composite Materials in Databases
  • ASTM E1471 Guide for Identification of Fibers, Fillers, and Core Materials in Computerized Material Property Databases

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