ASTM D6641/D6641M-23 PDF

Full title and description

Standard Test Method for Compressive Properties of Polymer Matrix Composite Materials Using a Combined Loading Compression (CLC) Test Fixture — designation D6641/D6641M‑23. This test method defines the combined end- and shear-loading (CLC) fixture and procedures used to obtain compressive strength and stiffness properties of polymer‑matrix composite laminates and similar materials. It supports both tabbed (Procedure B) and untabbed (Procedure A) specimens and is intended for material characterization, quality assurance, and structural design inputs.

Abstract

This standard describes the geometry, fixturing, test setup, conditioning, and measurement requirements for performing combined loading compression (CLC) tests on polymer matrix composite materials. Measured outputs include ultimate compressive strength and strain, compressive modulus (linear or chord), and Poisson’s ratio in compression; the method emphasizes prevention of end crushing and control of alignment, and it provides instructions for tabbed and untabbed specimen handling to obtain reproducible results suitable for R&D and specification work.

General information

• Status: Published / Active
• Publication date: 15 November 2023
• Publisher: ASTM International
• ICS / categories: 83.140.10 (Films and sheets / composite materials test methods)
• Edition / version: D6641/D6641M‑23 (replaces D6641/D6641M‑16e2)
• Number of pages: 13

Scope

This test method determines compressive strength and stiffness of polymer‑matrix composite materials using a combined loading compression (CLC) fixture. It applies to balanced, symmetric laminates and may be used for unidirectional (0° ply orientation) and multidirectional laminates, fabric and chopped‑fiber composites, and similar materials. The method explains when untabbed specimens (Procedure A) are acceptable (typically lower‑orthotropy materials or laminates with limited 0° plies) and when tabbed specimens (Procedure B) are required (typically highly orthotropic, unidirectional composites). The compressive force is introduced by combined end‑ and shear‑loading to reduce end crushing and buckling compared with pure end‑ or pure shear‑loading methods.

Key topics and requirements

• Use of a CLC test fixture to introduce combined end and shear loading.
• Two procedures: Procedure A (untabbed specimens) and Procedure B (tabbed specimens) with guidance on when each is appropriate.
• Specimen preparation and tabbing requirements to prevent end crushing and to ensure accurate load transfer.
• Alignment, fixturing, and platen requirements to minimize buckling and localized failure.
• Required measurements: ultimate compressive strength and strain, compressive (linear or chord) modulus, and Poisson’s ratio in compression.
• Specified reporting units in SI or inch‑pound; values in each system are to be regarded separately as standard.
• Environmental conditioning, test speed, and specimen stacking/layup factors that influence results and must be controlled and reported.
• Precision and reproducibility considerations; interlaboratory precision statements have been developed for the method.

Typical use and users

Used widely in aerospace, automotive, marine, and other industries that develop and qualify polymer‑matrix composite materials and laminates. Typical users include composite materials engineers, test laboratories, R&D groups, quality assurance teams, certification authorities, and structural analysts who need reliable compressive property data for design and validation.

Related standards

Closely related ASTM methods used for compressive testing and complementary measurements include Test Method D3410/D3410M (compression by shear‑loading) and Test Method D695 (compressive properties of rigid plastics); D6641/D6641M is often used alongside tensile and interlaminar test methods (for example, D3039 for tensile properties) when characterizing composite laminates.

Keywords

combined loading compression, CLC, compressive strength, compressive modulus, polymer‑matrix composite, tabbed specimen, untabbed specimen, specimen alignment, end crushing, ASTM D6641, D6641/D6641M‑23

FAQ

Q: What is this standard?

A: ASTM D6641/D6641M‑23 is the Standard Test Method for Compressive Properties of Polymer Matrix Composite Materials Using a Combined Loading Compression (CLC) Test Fixture; it defines procedures and fixturing to measure compressive strength and stiffness of composite laminates.

Q: What does it cover?

A: It covers test fixture configuration, specimen preparation (tabbed and untabbed), alignment, test execution, required measurements (ultimate compressive strength and strain, compressive modulus, Poisson’s ratio), conditioning and reporting requirements, and guidance on applicability to various laminate types.

Q: Who typically uses it?

A: Materials and test engineers, composite R&D and QA laboratories, aerospace and automotive qualification teams, certification bodies, and anyone needing standardized compressive property data for composite materials.

Q: Is it current or superseded?

A: Current — the D6641/D6641M‑23 edition was published in November 2023 and replaces the previous D6641/D6641M‑16e2 edition.

Q: Is it part of a series?

A: It is part of the ASTM composite materials test methods administered by Committee D30 (subcommittee D30.04) and is commonly used together with related ASTM test methods such as D3410/D3410M (compression by shear loading) and D3039 (tensile properties) to fully characterize laminate behavior.

Q: What are the key keywords?

A: Combined loading compression (CLC), compressive strength, compressive modulus, polymer matrix composite, tabbed specimen, untabbed specimen, alignment, ASTM D6641/D6641M‑23.