ASTM D7028-07(2024)
(Test Method)Standard Test Method for Glass Transition Temperature (DMA Tg) of Polymer Matrix Composites by Dynamic Mechanical Analysis (DMA)
Standard Test Method for Glass Transition Temperature (DMA Tg) of Polymer Matrix Composites by Dynamic Mechanical Analysis (DMA)
SIGNIFICANCE AND USE
5.1 This test method is designed to determine the glass transition temperature of continuous fiber reinforced polymer composites using the DMA method. The DMA Tg value is frequently used to indicate the upper use temperature of composite materials, as well as for quality control of composite materials.
SCOPE
1.1 This test method covers the procedure for the determination of the dry or wet (moisture conditioned) glass transition temperature (Tg) of polymer matrix composites containing high-modulus, 20 GPa (> 3 × 106 psi), fibers using a dynamic mechanical analyzer (DMA) under flexural oscillation mode, which is a specific subset of the Dynamic Mechanical Analysis (DMA) method.
1.2 The glass transition temperature is dependent upon the physical property measured, the type of measuring apparatus and the experimental parameters used. The glass transition temperature determined by this test method (referred to as “DMA Tg”) may not be the same as that reported by other measurement techniques on the same test specimen.
1.3 This test method is primarily intended for polymer matrix composites reinforced by continuous, oriented, high-modulus fibers. Other materials, such as neat resin, may require non-standard deviations from this test method to achieve meaningful results.
1.4 The values stated in SI units are standard. The values given in parentheses are non-standard mathematical conversions to common units that are provided for information only.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7028 − 07 (Reapproved 2024)
Standard Test Method for
Glass Transition Temperature (DMA Tg) of Polymer Matrix
Composites by Dynamic Mechanical Analysis (DMA)
This standard is issued under the fixed designation D7028; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method covers the procedure for the determi-
D3878 Terminology for Composite Materials
nation of the dry or wet (moisture conditioned) glass transition
D4065 Practice for Plastics: Dynamic Mechanical Proper-
temperature (T ) of polymer matrix composites containing
g
ties: Determination and Report of Procedures
high-modulus, 20 GPa (> 3 × 10 psi), fibers using a dynamic
D4092 Terminology for Plastics: Dynamic Mechanical
mechanical analyzer (DMA) under flexural oscillation mode,
Properties
which is a specific subset of the Dynamic Mechanical Analysis
D5229/D5229M Test Method for Moisture Absorption Prop-
(DMA) method.
erties and Equilibrium Conditioning of Polymer Matrix
1.2 The glass transition temperature is dependent upon the
Composite Materials
physical property measured, the type of measuring apparatus
E177 Practice for Use of the Terms Precision and Bias in
and the experimental parameters used. The glass transition
ASTM Test Methods
temperature determined by this test method (referred to as
E691 Practice for Conducting an Interlaboratory Study to
“DMA Tg”) may not be the same as that reported by other
Determine the Precision of a Test Method
measurement techniques on the same test specimen.
E1309 Guide for Identification of Fiber-Reinforced
Polymer-Matrix Composite Materials in Databases (With-
1.3 This test method is primarily intended for polymer
drawn 2015)
matrix composites reinforced by continuous, oriented, high-
E1434 Guide for Recording Mechanical Test Data of Fiber-
modulus fibers. Other materials, such as neat resin, may require
Reinforced Composite Materials in Databases (Withdrawn
non-standard deviations from this test method to achieve
2015)
meaningful results.
E1471 Guide for Identification of Fibers, Fillers, and Core
1.4 The values stated in SI units are standard. The values
Materials in Computerized Material Property Databases
given in parentheses are non-standard mathematical conver-
(Withdrawn 2015)
sions to common units that are provided for information only.
E1640 Test Method for Assignment of the Glass Transition
Temperature By Dynamic Mechanical Analysis
1.5 This standard does not purport to address all of the
E1867 Test Methods for Temperature Calibration of Dy-
safety concerns, if any, associated with its use. It is the
namic Mechanical Analyzers
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
3. Terminology
mine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accor- 3.1 Definitions—Terminology D3878 defines terms relating
dance with internationally recognized principles on standard- to polymer matrix composites. Terminology D4092 defines
ization established in the Decision on Principles for the terms relating to dynamic mechanical property measurements
Development of International Standards, Guides and Recom- on polymeric materials.
mendations issued by the World Trade Organization Technical
3.2 Symbols: E’ = storage modulus
Barriers to Trade (TBT) Committee.
E” = loss modulus
1 2
This test method is under the jurisdiction of ASTM Committee D30 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Composite Materials and is the direct responsibility of Subcommittee D30.04 on contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Lamina and Laminate Test Methods. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Jan. 1, 2024. Originally approved in 2007. Last the ASTM website.
ε1 3
previous edition approved in 2015 as D7028 – 07 (2015). Published January 2024. The last approved version of this historical standard is referenced on
DOI: 10.1520/D7028-07R24. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7028 − 07 (2024)
thermomechanical analysis (TMA). For greatest precision, it has been
tan δ = E”/E’ = tangent delta
recommended that heating rates be 2 °C ⁄min or less. Test Method E1640
DMA Tg = glass transition temperature defined from dy-
specifies a heating rate of 1 °C ⁄min. However, in many cases 5 °C ⁄min is
namic mechanical analysis measurement
recommended as a compromise between Tg measurement accuracy and
L = length of specimen
test method convenience, especially for wet laminate measurements, since
W = width of specimen
the slower heating rate will cause specimen drying that will itself bias the
results.
T = thickness of specimen
T = peak temperature from tangent delta curve
t
6.4 Purge gas type and flow rate and the position of the
thermocouple can affect the DMA Tg test result and shall be
4. Summary of Test Method
noted and reported. The same conditions shall be used for both
calibration and testing runs. Instrumentation manufacturer
4.1 A flat rectangular strip of laminate is placed in the DMA
recommendations should be followed.
equipment and oscillated at a nominal frequency of 1 Hz. The
specimen is heated at a rate of 5 °C ⁄min (9 °F ⁄min). The same
6.5 It is standard in this test method that one of the major
loading frequency and heating rate is used for both dry and wet
fiber directions shall be parallel to the length of the specimen.
specimens (moisture conditioned) to allow for comparison.
The span-to-depth ratio, ply orientation, and ply stacking
The temperature at which a significant drop in storage modulus
sequence of a specimen with respect to the testing fixture have
(E’) begins is assigned as the glass transition temperature
a profound effect on the DMA Tg result. A meaningful
(DMA Tg). The peak temperature of the tangent delta curve
comparison of data requires that the specimen configuration be
(T ) is identified along with DMA Tg for comparison purposes.
t
the same. A non-standard specimen configuration shall be
described in the report and the result recorded as non-standard.
5. Significance and Use
6.6 The standard definition in this test method for DMA Tg
5.1 This test method is designed to determine the glass
is based on intersecting two tangent lines from a semi-
transition temperature of continuous fiber reinforced polymer
logarithmic plot of the storage modulus versus temperature.
composites using the DMA method. The DMA Tg value is
Other T definitions typically produce different test results. For
g
frequently used to indicate the upper use temperature of
example, a linear plot scale will result in a lower value of DMA
composite materials, as well as for quality control of composite
Tg. A non-standard DMA Tg definition shall be described in
materials.
the report and the result recorded as non-standard. For com-
parison purposes the peak temperature of the tangent delta
6. Interferences
curve (T ) is identified along with DMA Tg.
t
6.1 The standard testing machine shall be of the Dynamic
Mechanical Analysis (DMA) type of instrument that operates
7. Apparatus
with forced oscillation and applies a flexural loading mode
7.1 Micrometer, suitable for reading to 0.025 mm (0.001 in.)
(either three-point bend or dual cantilever) to the test specimen.
accuracy for measuring the specimen thickness and width.
Refer to Practice D4065 for a summary of various other DMA
practices. Other loading modes (such as tensile, torsion or
7.2 Caliper, suitable for reading to 0.025 mm (0.001 in.)
shear) may produce different test results. If another equipment
accuracy for measuring the specimen length and instrument
type or loading mode is used the non-standard approach shall
clamping distance.
be described in the report and the test result recorded as
7.3 Dynamic Mechanical Analyzer (DMA), with oven ca-
non-standard.
pable of heating to above the glass transition temperature and
6.2 A fixed frequency of 1 Hz is standard in this test method.
of controlling the heating rate to the specified value.
In general, for a given material, a higher testing frequency
produces a higher DMA Tg value than this standard, while use
8. Sampling and Test Specimens
of the resonance mode will yield a different DMA Tg that may
8.1 Two specimens shall be tested for each sample. If the
be either higher or lower than the standard. If a non-standard
testing is part of a designed experiment, other sampling
frequency, or the resonance mode, is used, the non-standard
techniques may be used if described in the test plan.
approach shall be described in the report and the test result
recorded as non-standard.
8.2 Consult the instrument manufacturer’s manual for speci-
men size. A span-to-thickness ratio greater than ten is recom-
6.3 A heating rate of 5 °C ⁄min 6 1 °C ⁄min (9 °F ⁄min 6
mended. Specimen absolute size is not fixed by this method as
2 °F ⁄min) is standard in this test method. A change in heating
various dynamic mechanical analyzers require different sizes.
rate will affect the glass transition temperature result; the
Depending on the analyzer, typical specimen size can range
standard heating rate is the best available compromise for
from 56 6 4 × 12 6 1 × 2.0 6 0.5 mm (2.21 6 0.16 × 0.47
comparing DMA Tg results of dry and wet laminates. If a
6 0.04 × 0.08 6 0.02 in.) (L × W × T) to 22 6 1 × 3 6 1 ×
different heating rate is used it shall be described in the report
1.0 6 0.5 mm (0.9 6 0.04 × 0.12 6 0.04 × 0.04 6 0.02 in.).
and the result recorded as non-standard.
NOTE 1—Users should be advised that a heating rate of 5 °C ⁄min
8.3 One of the major fiber directions in the specimen shall
represents a compromise between various issues related to Tg measure-
be oriented along the length axis of the specimen. It is standard
ment precision and bias. It is widely known that heat transfer limitations
that one of the major fiber directions shall be parallel to the
are more pronounced in DMA apparatus compared to other thermal
analysis techniques, such as differential scanning calorimetry (DSC) and length of the specimen, and specimens containing only off-axis
D7028 − 07 (2024)
plies shall not be used. Any deviations from the standard 11.2 Specimen Installation—Install the specimen in the
orientation shall be reported and the test results noted as DMA test equipment oven based upon clamping method to be
non-standard. employed.
8.4 The specimen surfaces shall be flat, clean, straight, and 11.3 Positioning of Specimen—Follow the manufacturer’s
dry to prevent slippage in the grips and mitigate any effects due
procedure for positioning the specimen in the clamps.
to moisture. Opposite surfaces must be essentially parallel and Generally, the specimen should be centered between the clamp
intersecting surfaces perpendicular. Tolerances in thickness and faces and be parallel to the base of the instrument. Mount the
width must be better than 62 %. specimen in dual cantilever mode or three-point bending mode.
8.5 The selected sample shall be taken from a representative
11.4 Heating Rate—The standard heating rate is 5 °C ⁄min
portion of the laminate. Laminate edges or other irregularities 6 1 °C ⁄min (9 °F ⁄min 6 2 °F ⁄min). The same heating rate
created in the laminate by mold or bagging techniques should
shall be used for all samples whose results are to be compared.
be avoided. Any deviations from this heating rate shall be noted in the
report and the result shall be reported as non-standard.
9. Calibration
11.5 Frequency—The standard frequency to be used in this
9.1 The DMA equipment shall be calibrated in accordance
standard is 1 Hz, and the instrument should be operated in
with Test Method E1867 for temperature signals and in
constant strain mode.
accordance with the equipment manufacturer’s recommenda-
11.6 Strain Amplitude—The maximum strain amplitude
tion for the storage modulus. The equipment must be calibrated
should be kept within the linear viscoelastic range of the
in the same loading mode as will be used for testing, either dual
material. Strains of less than 0.1 % are standard.
cantilever or three-point bending. The temperature calibration
points must span the DMA Tg result. 11.7 Temperature Range—Program the run to begin at room
temperature or a temperature at least 50 °C (90 °F) below the
10. Conditioning
estimated DMA Tg and to end at a temperature at least 50 °C
(90 °F) above DMA Tg, but below decomposition temperature.
10.1 Moisture has significant effect on DMA Tg. Therefore,
it is recommended that the test specimens should be weighed
11.8 Purge Gas Flow Rate—Follow the manufacturer’s
before and after DMA Tg testing to quantify the moisture
manual or recommendations to set the purge gas flow rate. Five
change in the specimen resulting from the DMA Tg test.
litres/minute (0.2 CFM) is a typical purge gas flow rate setting.
For some types of dynamic mechanical analyzers, a purge gas
10.2 Dry Specimens—To minimize the presence of moisture
flow setting is not required.
in the specimens, dry specimens must be conditioned prior to
testing by using either of the following techniques:
11.9 Thermocouple Positioning—Follow the manufacturer’s
10.2.1 Dry the specimens in an oven in accordance with
manual or recommendations to position the thermocouple.
Test Method D5229/D5229M, Procedure D, then stored until
Typically the thermocouple should be as close to the sample as
test in a desiccator or sealed MIL-PRF-131 (or equivalent)
possible.
aluminized bag, or
11.10 Test—Conduct DMA Tg measurements using the
10.2.2 Store the material in a desiccator or sealed alumi-
instrument settings specified and record the load and displace-
nized bag immediately after material curing (lamination),
ment data as a function of temperature. Allow the oven to cool
where the material shall remain except for the minimum time
before removing the specimen. Weigh the specimen after the
required for removal during specimen preparation and testing.
test to the nearest milligram (0.001 g) after the removal from
The maximum time between cure (lamination) and testing shall
the oven and record.
be 30 days, after which, prior to tes
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