MaTestLab > Test Standards > ASTM D7028 Standard Test Method for Glass Transition Temperature (DMA Tg) of Polymer Matrix Composites
Last updated 9th October 2025
ASTM D7028 Standard Test Method for Glass Transition Temperature (DMA Tg) of Polymer Matrix Composites
ASTM D7028, also known as the Standard Test Method for Glass Transition Temperature (DMA Tg) of Polymer Matrix Composites by Dynamic Mechanical Analysis (DMA), is a widely used test method. The glass transition temperature of polymer matrix composites is a critical parameter in understanding their mechanical behavior. The ASTM D7028 method describes how to determine the dry or wet glass transition temperature (Tg) of polymer matrix composites with high-modulus fibers using a dynamic mechanical analyzer (DMA) in flexural oscillation mode. DMA involves subjecting a sample to oscillating stress or strain while simultaneously measuring its response in terms of storage modulus (stiffness) and loss modulus (damping). The resulting Tg, known as DMA Tg, may vary from other measurement techniques. It's mainly for composites with continuous, oriented, high-modulus fibers, but adjustments may be necessary for materials like neat resin.
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ASTM D7028 Introduction
ASTM D7028 outlines a procedure for assessing the dry and wet transition temperatures (Tg) of polymer matrix composites. These composites feature high modulus, 20 GPa fibers, and are analyzed using a dynamic mechanical analyzer. Various experimental parameters, apparatus, and physical properties measured influence the glass transition temperature. ASTM D7028 is designed for polymer matrix composites reinforced by continuous, oriented, high modulus fibers. The measurements made using this procedure are of paramount importance to ascertain the thermal performance and longevity of composite materials under operational conditions. The knowledge of the glass transition temperature aids product designers, material scientists, and engineers in decision-making during product development, quality assurance, and structural design. The standard is extensively used in the aerospace, automobile, marine, and building industries where composite materials are exposed to different thermal and mechanical loads. It guarantees uniform material behavior, performance reliability, and safety under a variety of environments and applications.
ASTM D7028 Test Method
DMA Analysis
In ASTM D7028-07, specimen dimensions and weight are recorded. A flat laminate strip is placed in the dynamic mechanical analyzer and oscillated at 1 Hz. Heating occurs at 5 °C/min. Identical parameters are used for both dry and wet specimens to ensure direct comparison.
Glass Transition Temperature Measurement
The DMA Tg is determined by observing a significant drop in the storage modulus during the test. It begins either at room temperature or 50 °C below the estimated DMA Tg and ends at least 50 °C above DMA Tg but below the decomposition temperature.
Recording Data
Load and displacement data are collected as temperature varies. After completing the test, the specimen is visually inspected for anomalies such as blisters or cracks.
ASTM D7028 Equipment and Sample Preparation
Specimen Details
ASTM D7028 aims to ascertain the glass transition temperature of continuous fiber-reinforced polymer composites through the DMA technique. Each sample requires the testing of two specimens.
Specimen Size
The specimen size may vary depending on the analyzer, typically ranging from 56 ± 4 × 12 ± 1 × 2.0 ± 0.5 mm (L × W × T) to 22 ± 1 × 3 ± 1 × 1.0 ± 0.5 mm.
ASTM D7028 Test Results and Interpretation
ASTM D7028 accurately identifies DMA Tg as the intersection point of two tangent lines drawn from the storage modulus. The Tg identified with the tan d peak tends to be larger than that of the onset of the decrease in storage modulus. To ensure quality control, the same technique should be applied to compare it. The resultant Tg is susceptible to frequency, heating rate, moisture content, and composite layup; therefore, these factors should be controlled and reported.
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Tests related to ASTM D7028
ASTM D7028 is related to specifications, including ASTM D5229 for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite Materials, ASTM E177 Practice for Precision and Bias in ASTM Test Methods, ASTM E691 Practice for Conducting Interlaboratory Study for Test Method Precision, and ASTM E1309 Guide for Identification of Fiber-Reinforced Polymer-Matrix Composite Materials in Databases.
Use of ASTM D7028 in Various Industries
It is an important test in the aerospace, automotive, and electronics industries for the determination of glass transition temperature in polymer matrix composites to ensure structural integrity, material selection for circuit boards, and improvement in lightweight composite materials.
Common Challenges and Troubleshootingin ASTM D7028
ASTM D7028 testing can encounter several challenges that can impact the accuracy and reliability of Tg determination. The subject of moisture sensitivity is a serious concern, as the presence of moisture in composite specimens may lower the measured Tg. Therefore, it is essential to condition specimens before testing. The geometry of the specimen is also a significant issue; a variation in thickness or poor machining may cause irregular measurements of modulus and distorted results.
Safety and Best Practices in ASTM D7028 Testing
Testing requires proper handling of specimens and equipment, regular calibration of the dynamic mechanical analyzer, and clean environments to ensure accuracy. Proper ventilation and specimen preparation are also important to avoid unexpected breakage.
Importance of ASTM D7028
It is an important means of evaluating the thermal behavior of polymer matrix composites, which enables an accurate assessment of glass transition temperature or Tg. The quality product, prediction of material’s behavior, reliability, and safety in high-tech applications were assured.
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Where can I get the astm d7028 tested?
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