ASTM C749-15 (2020) PDF

Full title and description

ASTM C749-15 (Reapproved 2020) — Standard Test Method for Tensile Stress‑Strain of Carbon and Graphite. Defines procedures, specimen configurations, fixtures, and measurement methods to obtain tensile stress–strain behavior of carbon and graphite materials to failure, from which ultimate tensile strength, strain at failure, and elastic modulus are derived. The method is adaptable for elevated‑temperature testing and was developed from interlaboratory round‑robin data to provide engineering‑level results rather than only quality‑control checks.

Abstract

This test method specifies how to prepare and test carbon and graphite specimens in tension to measure complete tensile stress‑strain response to failure, plus guidance on grips, load trains, strain measurement (strain gauges, extensometers, optical systems), and parasitic‑stress monitoring. It includes suggested specimen sizes and addresses precision and bias based on multi‑laboratory studies.

General information

• Status: Published / Active.
• Publication date: Current edition approved May 1, 2020 (reapproval of C749‑15); published 2020.
• Publisher: ASTM International.
• ICS / categories: 71.060.10 (Chemical elements) — Committee D02 (Manufactured carbon and graphite products).
• Edition / version: C749 − 15 (Reapproved 2020).
• Number of pages: Listed as 11–12 pages depending on publisher listing (ASTM store lists 12 pages).

Scope

This method covers tensile testing of carbon and graphite to obtain tensile stress‑strain behavior to failure for determination of ultimate strength, strain to failure, and elastic moduli. It provides recommended specimen sizes, fixture designs, and measurement techniques and can be used for a wide range of graphites and carbons; the procedure may be adapted to high‑temperature testing (historically used up to ~2400 °C) by using appropriate high‑temperature load‑train materials.

Key topics and requirements

• Specimen geometry and suggested sizes for different grain sizes and materials to encourage fracture within the gauge section.
• Testing machine requirements (practice E4 referenced) including load cell capacity and calibration.
• Fixture and grip designs (detailed assemblies, chains, yokes, pins) to minimise parasitic stresses; recommended designs illustrated in figures and tables.
• Strain measurement options: strain gauges, mechanical extensometers, Tuckerman gauges, optical systems; use of opposing gauges to compensate bending.
• Parasitic stress monitoring using optional monitors to detect axial bending (<5% target parasitic stress) and guidance for mounting extensometers/gauges to avoid surface damage.
• Precision and bias established from round‑robin testing (hundreds of tests) and guidance on sampling and grain orientation for meaningful comparisons.
• High‑temperature testing adaptation and safety recommendations for containment of load‑train elements at failure.
• Reporting requirements for measured properties and test conditions to ensure repeatability and comparability.

Typical use and users

Used by materials and mechanical testing laboratories, manufacturers of carbon/graphite products, research institutions, and quality‑assurance teams to characterize tensile behavior (strength, ductility/strain, elastic modulus) of carbon and graphite materials for design, failure analysis, and material specification. Engineers using graphite in high‑temperature applications (e.g., thermal, nuclear, refractory) also rely on this method for validated tensile data.

Related standards

Referenced / related ASTM practices and test methods include: Practice E4 (force verification of testing machines), Practice E177 (use of terms precision and bias), Practice E691 (interlaboratory study for precision), and Test Method C565 (other graphite testing guidance). The standard cites these documents for machine verification, statistical interpretation, and interlaboratory precision context.

Keywords

ASTM C749, tensile test, tensile stress‑strain, carbon, graphite, tensile strength, elastic modulus, strain to failure, extensometer, high‑temperature testing, parasitic stress, specimen geometry.

FAQ

Q: What is this standard?

A: ASTM C749‑15 (Reapproved 2020) is the Standard Test Method for Tensile Stress‑Strain of Carbon and Graphite describing how to obtain tensile stress‑strain behavior to failure and calculate strength and modulus.

Q: What does it cover?

A: It covers specimen selection and preparation, fixture and grip assemblies, testing machine requirements and calibration, strain‑measurement techniques, parasitic‑stress monitoring, suggested specimen sizes, and reporting to obtain reliable tensile properties for carbon and graphite materials.

Q: Who typically uses it?

A: Materials testing laboratories, graphite/carbon manufacturers, R&D organisations, and engineers who need validated tensile data for design, qualification, or failure analysis.

Q: Is it current or superseded?

A: The designation is C749‑15 with a 2020 reapproval (current edition approved May 1, 2020). Users should confirm at time of purchase or subscription whether a later revision or reapproval exists.

Q: Is it part of a series?

A: It is part of the suite of ASTM methods and practices for carbon and graphite products under Committee D02 and is cross‑referenced with other ASTM test methods and practices (for example, C565 and E‑series practices used for machine verification and precision assessment).

Q: What are the key keywords?

A: Tensile test, carbon, graphite, tensile strength, elastic modulus, strain to failure, extensometer, high‑temperature testing, specimen geometry, parasitic stress.