ASTM D7028-07 (2024) PDF

Full title and description

ASTM D7028-07(2024) — Standard Test Method for Glass Transition Temperature (DMA Tg) of Polymer‑Matrix Composites by Dynamic Mechanical Analysis (DMA). This test method defines procedures for determining the DMA glass transition temperature (DMA Tg) of continuous fiber reinforced polymer‑matrix composites using a dynamic mechanical analyzer under flexural oscillation modes.

Abstract

This standard provides a repeatable DMA procedure for reporting a composite material’s glass transition temperature as measured from storage modulus and tanδ responses. It establishes specimen configuration, mounting modes (dual‑cantilever or three‑point bending), test frequency and heating‑rate defaults, calibration and reporting requirements so that dry and moisture‑conditioned (wet) composite laminates can be compared. The method is intended primarily for continuous, high‑modulus fiber reinforced composites and includes guidance on result interpretation (DMA Tg and tangent‑intersection definition).

General information

• Status: Active — designation D7028 − 07 (reapproved 2024).
• Publication date: Effective / reapproval date 01 January 2024 (original adoption 2007).
• Publisher: ASTM International.
• ICS / categories: Reinforced plastics — ICS code reported as 83.120 (reinforced plastics).
• Edition / version: D7028-07 (Reapproved 2024).
• Number of pages: 13–14 pages (published pagination reported as 14 pages in current reapproval listings).

Scope

The test method covers determination of the dry or moisture‑conditioned glass transition temperature (DMA Tg) of polymer matrix composites reinforced with continuous, oriented, high‑modulus fibers (≥ ~20 GPa) using a DMA in flexural oscillation mode. It notes that Tg depends on the measured property and test parameters and that DMA Tg may differ from Tg values measured by other techniques. Non‑standard specimen configurations and deviations must be reported.

Key topics and requirements

• Intended materials: continuous fiber reinforced polymer matrix composites (high‑modulus fibers).
• Typical specimen geometry and orientation requirements; one major fiber direction parallel to specimen length; flat, parallel faces and tight dimensional tolerances.
• Recommended test mode: dual‑cantilever or three‑point bending (flexural oscillation).
• Standard test frequency: 1 Hz (constant strain mode recommended).
• Standard heating rate: 5 °C/min (±1 °C/min) for the default procedure; deviations must be reported as non‑standard.
• DMA Tg definition: temperature where a significant drop in storage modulus begins (tangent‑intersection method on semi‑log storage modulus vs temperature); peak tanδ is also identified for comparison.
• Calibration and instrumentation: temperature calibration per E1867 and equipment calibration in same loading mode as testing; report purge gas, thermocouple location, and all instrument settings.
• Conditioning and moisture effects: drying/conditioning procedures and post‑test weighing are specified because moisture significantly affects DMA Tg.
• Precision and reproducibility: an interlaboratory study and research report exist to support precision statements for the method.

Typical use and users

Used by materials laboratories, composite manufacturers, aerospace and automotive R&D and quality control, and test laboratories to establish upper use temperatures, compare dry vs. moisture‑conditioned performance, verify cure and processing effects, and for material specifications and acceptance testing. The method is frequently cited for Tg determination in composite research and development.

Related standards

References and related procedures commonly cited with D7028 include ASTM E1867 (temperature calibration for DMA), various DMA geometry and terminology standards (such as D4065, D5023), conditioning and moisture standards (e.g., D5229/D5229M), and other DMA‑based cure and rheology standards (for example D7750). The standard is published under committee D30 (composites) and is cross‑referenced by multiple composite specifications.

Keywords

glass transition temperature, DMA Tg, dynamic mechanical analysis, polymer‑matrix composite, reinforced plastics, DMA, tangent delta, storage modulus, three‑point bending, dual‑cantilever.

FAQ

Q: What is this standard?

A: ASTM D7028-07(2024) is a test method that defines how to measure the glass transition temperature of polymer‑matrix composites using dynamic mechanical analysis (DMA) in flexural modes.

Q: What does it cover?

A: It covers specimen preparation and orientation, DMA mounting modes, recommended frequency and heating rate, calibration and reporting requirements, and how to identify DMA Tg (tangent‑intersection on storage modulus and peak tanδ for comparison). It applies primarily to continuous, oriented, high‑modulus fiber composites.

Q: Who typically uses it?

A: Materials test labs, composite manufacturers, aerospace and automotive material engineers, and researchers use this method for product development, acceptance testing and quality control.

Q: Is it current or superseded?

A: The designation shows D7028‑07 reapproved in 2024 (effective 01 January 2024) and is listed as active; users should check the official ASTM catalog for any later revisions.

Q: Is it part of a series?

A: It is part of ASTM’s family of thermal and DMA test methods and was developed by subcommittee D30.04 (composites), so it is commonly used alongside related DMA, thermal‑analysis and composite conditioning standards.

Q: What are the key keywords?

A: Glass transition, DMA Tg, dynamic mechanical analysis, polymer matrix composite, storage modulus, tanδ, reinforced plastics.