ASTM D7750-12(2017)

Standard Test Method for Cure Behavior of Thermosetting Resins by Dynamic Mechanical Procedures using an Encapsulated Specimen Rheometer

SIGNIFICANCE AND USE
5.1 This method provides a simple means of characterizing the cure behavior of a thermosetting resin specimen that is a representation of a composite part. The diameter of the specimen is approximately 38 mm and the thickness ranges from 2.6 to 3.2 mm. This corresponds to a sample volume of approximately 3 to 4 cm3. The data may be used for quality control, research and development, and verifying the cure within processing equipment including autoclaves.  
5.2 Dynamic mechanical testing provides a sensitive method for determining cure characteristics by measuring the elastic and loss moduli as a function of temperature or time, or both. Plots of cure behavior and tan delta of a material provide graphical representation indicative of cure behavior under a specified time-temperature profile. The presence of fibers within the resin may change the dynamic properties measured within a material. However, it is still possible to compare different resins with the same fiber structure and obtain the relative difference due to the resin cure properties.  
5.3 This method can be used to assess the following:  
5.3.1 Cure behavior, as well as changes as a function of temperature or time, or both,  
5.3.2 Processing behavior, as well as changes as a function of temperature or time, or both,  
5.3.3 The effects of processing treatments,  
5.3.4 Relative resin behavioral properties, including cure behavior, damping and impact resistance,  
5.3.5 The effects of reinforcement on cure.  
5.3.6 The effects of materials used to bond the resin and reinforcement,  
5.3.7 The effect of formulation additives that might affect processability or performance.  
5.4 This provides a method to assess the cure properties of a thermosetting resin containing woven fiber or other reinforcing materials.  
5.5 This method is valid for a wide range of oscillation frequencies typically from 0.002 to 50 Hz.
Note 1: It is recommended that low-frequency test conditions, generally 1 to 2 Hz, be...
SCOPE
1.1 This method covers the use of dynamic mechanical instrumentation for determination and reporting of the thermal advancement of cure behavior of thermosetting resin on an inert filler or fiber in a laboratory. It may also be used for determining the cure properties of filled resins and resins without reinforcements. These encapsulated specimens are deformed in torsional shear using dynamic mechanical methods.  
1.2 This method is intended to provide means for determining the cure behavior of thermosetting resins on fibers over a range of temperatures from room temperature to 250°C by forced-constant amplitude techniques (in accordance with Practice D4065). Plots of complex modulus, complex viscosity, and damping ratio or tan delta as a function of time or temperature, or both, quantify the thermal advancement or cure characteristics of a resin or a resin on fiber.  
1.3 Test data obtained by this method is relevant and appropriate for optimizing cure cycles.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4.1 Exception—The fahrenheit temperature measurement in 10.1 is provided for information only and is not considered standard.  
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 and health 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

• Status: Historical
• Publication Date: 31-Jul-2017
• ICS: 83.080.10 - Thermosetting materials
• Technical Committee: D30 - Composite Materials
• Drafting Committee: D30.03 - Constituent/Precursor Properties

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D7750 − 12 (Reapproved 2017)
Standard Test Method for
Cure Behavior of Thermosetting Resins by Dynamic
Mechanical Procedures using an Encapsulated Specimen
Rheometer
This standard is issued under the fixed designation D7750; 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 Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
1.1 This method covers the use of dynamic mechanical
Barriers to Trade (TBT) Committee.
instrumentation for determination and reporting of the thermal
advancement of cure behavior of thermosetting resin on an
2. Referenced Documents
inert filler or fiber in a laboratory. It may also be used for
determining the cure properties of filled resins and resins
2.1 ASTM Standards:
without reinforcements. These encapsulated specimens are
D3878 Terminology for Composite Materials
deformed in torsional shear using dynamic mechanical meth-
D4000 Classification System for Specifying Plastic Materi-
ods.
als
1.2 This method is intended to provide means for determin-
D4065 Practice for Plastics: Dynamic Mechanical Proper-
ing the cure behavior of thermosetting resins on fibers over a
ties: Determination and Report of Procedures
range of temperatures from room temperature to 250°C by
D4092 Terminology for Plastics: Dynamic Mechanical
forced-constant amplitude techniques (in accordance with
Properties
Practice D4065). Plots of complex modulus, complex
D4473 Test Method for Plastics: Dynamic Mechanical Prop-
viscosity, and damping ratio or tan delta as a function of time
erties: Cure Behavior
or temperature, or both, quantify the thermal advancement or
D6507 Practice for Fiber Reinforcement Orientation Codes
cure characteristics of a resin or a resin on fiber.
for Composite Materials
D7028 Test Method for Glass Transition Temperature (DMA
1.3 Test data obtained by this method is relevant and
Tg) of Polymer Matrix Composites by Dynamic Mechani-
appropriate for optimizing cure cycles.
cal Analysis (DMA)
1.4 The values stated in SI units are to be regarded as
E380 Practice for Use of the International System of Units
standard. No other units of measurement are included in this
(SI) (the Modernized Metric System) (Withdrawn 1997)
standard.
1.4.1 Exception—The fahrenheit temperature measurement
3. Terminology
in 10.1 is provided for information only and is not considered
standard.
3.1 Definitions: For most definitions applicable to this
1.5 This standard does not purport to address all of the method refer to Terminology D4092.
safety concerns, if any, associated with its use. It is the
3.2 Definitions of Terms Specific to This Standard:
responsibility of the user of this standard to establish appro-
3.2.1 Encapsulated Sample Parallel Plate Rheometer—
priate safety and health practices and determine the applica-
Dynamic Mechanical Analyzer apparatus that holds the speci-
bility of regulatory limitations prior to use.
men under pressure within a confined cavity. The apparatus is
1.6 This international standard was developed in accor-
designed to contain the resin within the specimen throughout
dance with internationally recognized principles on standard-
the progress of the cure.
ization established in the Decision on Principles for the
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 D30.03 on contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Constituent/Precursor Properties. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Aug. 1, 2017. Published September 2017. Originally the ASTM website.
approved in 2012. Last previous edition approved as D7750–12. DOI: 10.1520/ The last approved version of this historical standard is referenced on
D7750-12R17. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7750 − 12 (2017)
NOTE 1—It is recommended that low-frequency test conditions, gener-
4. Summary of Test Method
ally 1 to 2 Hz, be used to generate more definitive cure-behavior
4.1 A small circular specimen is assembled from uncured
information. Slower frequencies will miss important cure properties.
thermoset resin materials that correspond to a representation of Faster frequencies will reduce sensitivity to cure.
a composite part. This specimen is placed in mechanical
oscillation at a fixed frequency at either isothermal conditions, 6. Interferences
a linear temperature increase or a time-temperature relation
6.1 Apparent discrepancies in results may arise when using
simulating a processing condition. The lower plate oscillates
different experimental conditions. These apparent differences
and transmits torque from the lower plate through the sample
from results observed in another study can usually be recon-
into the upper plate. The resulting torque measured at the upper
ciled without changing the observed data, by reporting in full
plate is converted to shear modulus using equations that
(as described in this method) the conditions under which the
compensate for the shape and size of the sample. The shear
data were obtained. One essential condition within this method
modulus is separated into a component that is in phase with the
that must be noted is the presence of pressure within the
applied strain or elastic shear modulus and a component that is
specimen chamber which ensures good precision.
90° out of phase with the applied strain or loss shear modulus.
6.2 In many cases, the specimens made with this method
The elastic and loss modulus of the specimen are measured as
will be significantly smaller than the parts in production. It is
a function of time. During cure, the elastic shear modulus will
essential that specimens be made from representative samples
initially decrease as the temperature is increased due to a
of uncured material used to make parts. This will ensure that
decrease in the viscosity of the resin in the sample. When cure
the data is representative of the part cure.
occurs in the sample, the elastic shear modulus increases.
6.3 The result is a response to the thermal advancement or
5. Significance and Use
cure behavior of the resin. The cure behavior is also influenced
5.1 This method provides a simple means of characterizing by the reinforcement and materials used to enhance the bond
the cure behavior of a thermosetting resin specimen that is a
between the resin and reinforcement. The reinforcement can be
representation of a composite part. The diameter of the a fiber or a filler.
specimen is approximately 38 mm and the thickness ranges
6.4 The data will represent the cure of the system at the
from 2.6 to 3.2 mm. This corresponds to a sample volume of
measured temperature. Parts are often significantly thicker than
approximately 3 to 4 cm . The data may be used for quality
the specimen. There may be a significant difference between
control, research and development, and verifying the cure
the temperature versus time profile on the inside and the
within processing equipment including autoclaves.
outside of those composite parts. Thermocouples can be used
5.2 Dynamic mechanical testing provides a sensitive
to measure both temperatures during a cure process of a thick
method for determining cure characteristics by measuring the
part. The measured temperature versus time data can be used to
elastic and loss moduli as a function of temperature or time, or
define temperature versus time profiles for dynamic cure
both. Plots of cure behavior and tan delta of a material provide
specimens using the procedures of this standard. The results
graphical representation indicative of cure behavior under a
can be used to compare the cure response for the inside and the
specified time-temperature profile. The presence of fibers
outside of the composite part.
within the resin may change the dynamic properties measured
within a material. However, it is still possible to compare
7. Apparatus
different resins with the same fiber structure and obtain the
7.1 The function of the apparatus is to hold a resin specimen
relative difference due to the resin cure properties.
with inert reinforcement, such as fibers, under pressure and yet
5.3 This method can be used to assess the following:
prevent the escape of resin. Thereby, the fiber to resin ratio will
5.3.1 Cure behavior, as well as changes as a function of
remain constant throughout the test. The material acts as the
temperature or time, or both,
elastic and dissipative element in a mechanically driven
5.3.2 Processing behavior, as well as changes as a function
oscillatory shear system. This dynamic mechanical instrument
of temperature or time, or both,
operates in torsional shear using one of the following modes
5.3.3 The effects of processing treatments,
for measuring cure behavior:
5.3.4 Relative resin behavioral properties, including cure
7.1.1 Forced, constant amplitude, fixed frequency,
behavior, damping and impact resistance,
7.1.2 Forced, variable amplitude, fixed frequency.
5.3.5 The effects of reinforcement on cure.
7.2 The apparatus shall consist of the following:
5.3.6 The effects of materials used to bond the resin and
7.2.1 Parallel plates with serrated or radial grooved sur-
reinforcement,
faces. The diameter of the dies shall be 40 6 2 mm. The depth
5.3.7 The effect of formulation additives that might affect
of the grooves shall be limited to 1.0 mm or less to keep a
processability or performance.
constant fiber to resin ratio.
5.4 This provides a method to assess the cure properties of
7.2.2 Encapsulated Specimen Cavity—The specimen shall
a thermosetting resin containing woven fiber or other reinforc-
be encapsulated by the two parallel plates and a series of
ing materials.
mechanical components at the outer plate diameter designed to
5.5 This method is valid for a wide range of oscillation contain the specimen under pressure without loss of resin.
frequencies typically from 0.002 to 50 Hz. These components shall include an O-ring inserted at the outer
D7750 − 12 (2017)
diameter of the specimen (Fig. 1). The O-ring meets ASTM 8. Sampling and Test Specimens
International size No. 2-127.
8.1 The neat resin or the resin with reinforcement should be
7.2.3 Plate Gap—The thickness of the sample shall range
representative of the polymeric material being tested.
from 2.6 to 3.2 mm. The calculation of the sample modulus
8.2 The recommended specimen diameter for this apparatus
will include corrections to the actual sample thickness.
is 38 6 0.5 mm (Fig. 3) or a diameter recommended by the
7.2.4 Plate Closing Mechanism—The system shall apply a
apparatus manufacturer. Several 38-mm disks of uncured
pressure of at least 4200 kPa to the sample to prevent slippage.
material shall be laid up to produce a specimen for testing. The
7.2.5 Plate Oscillating System (Strain Device)—The plate
reinforcement type and lay-up shall be recorded in accordance
oscillating system shall consist of a direct drive motor that
with the laminate orientation code of Practice D6507. The
imparts a torsional oscillating movement to the lower plate in
number of disks required to produce a specimen will vary with
the cavity plane. The movement shall produce a continuous
the type of fiber and fiber architecture. A good initial value for
oscillatory deformation (strain) on the specimen. The deforma-
the thickness before compressing the sample is 4 mm. The final
tion (strain) shall be sinusoidal and shall be applied and
cured specimen should have a thickness of 2.6 to 3.2 mm after
released continuously as in a forced-vibration device (see Table
1 of Practice D4065) to provide a continuous measurement of a test is complete. The apparatus will often compress or reduce
the initial thickness into the preferred range of a tested
material state. The preferred amplitude ranges shall be from 6
0.005 to 6 0.060°. The resulting strain at the nominal specimen. The number of disks may vary with the resin and
fiber present in a specimen. The weight of the specimen can be
specimen thickness will range from 6 0.07 to 6 0.8 %.
used in place of the thickness as an alternate method to ensure
NOTE 2—The preferred strain for measuring the cure properties of
that the final specimen has the preferred thickness at the end of
thermoset resins is 6 0.7 %.
a test. The weight will have to be determined for each
7.2.6 Detectors—A device or devices for determining de-
resin/fiber combination. In all cases, equal weight or thickness
pendent and independent experimental parameters, such as
should be used when comparisons are made.
torque, frequency, strain amplitude and temperature. Tempera-
8.3 An elastomeric O-ring shall be placed at the outer
ture shall be measurable with a precision of 6 0.3°C at the
diameter of the specimen to help prevent the loss of resin
outer diameter of the plate, frequency to 60.1 % and torque to
during a test. The specimen shall also be placed between two
6 0.001 Nm.
sheets of release film to eliminate or reduce clean up after a
7.2.7 Temperature Controller—A device for directly heating
test. The film prevents the contamination of the plate surface
and cooling the plates with the ability to control the tempera-
with resins or other materials that can diffuse out of the
ture of the plates. The temperature can increase in steps or a
specimen. The film must be capable of the applied temperature
linear ramp or cool in steps or a linear ramp. Fig. 2 illustrates
profile. Different films can be used at different temperature
a typical time-temperature profile for measuring cure proper-
ranges.
ties. A temperature control system shall be sufficiently stable to
permit measurement of plate temperature to within 6 0.3°C
8.4 Low viscosity neat resins can be measured under pres-
during heating and 6 1°C during cooling. Fig. 2 also shows
sure either with or without reinforcement.
that the temperature in the part often deviates from the
8.5 A valid result is obtained when the elastomeric O-ring
recommended temperature profile. The apparatus shall process
remains intact at the outer diameter of the specimen and the
a specimen using either the recommended temperature profile
cured sample thickness is within the acceptable range. Also,
or the actual temperature profile in the p
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7750 − 12 D7750 − 12 (Reapproved 2017)
Standard Test Method for
Cure Behavior of Thermosetting Resins by Dynamic
Mechanical Procedures using an Encapsulated Specimen
Rheometer
This standard is issued under the fixed designation D7750; 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
1.1 This method covers the use of dynamic mechanical instrumentation for determination and reporting of the thermal
advancement of cure behavior of thermosetting resin on an inert filler or fiber in a laboratory. It may also be used for determining
the cure properties of filled resins and resins without reinforcements. These encapsulated specimens are deformed in torsional shear
using dynamic mechanical methods.
1.2 This method is intended to provide means for determining the cure behavior of thermosetting resins on fibers over a range
of temperatures from room temperature to 250°C by forced-constant amplitude techniques (in accordance with Practice D4065).
Plots of complex modulus, complex viscosity, and damping ratio or tan delta as a function of time or temperature, or both, quantify
the thermal advancement or cure characteristics of a resin or a resin on fiber.
1.3 Test data obtained by this method is relevant and appropriate for optimizing cure cycles.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4.1 Exception—The fahrenheit temperature measurement in 10.1 is provided for information only and is not considered
standard.
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 and health 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.
2. Referenced Documents
2.1 ASTM Standards:
D3878 Terminology for Composite Materials
D4000 Classification System for Specifying Plastic Materials
D4065 Practice for Plastics: Dynamic Mechanical Properties: Determination and Report of Procedures
D4092 Terminology for Plastics: Dynamic Mechanical Properties
D4473 Test Method for Plastics: Dynamic Mechanical Properties: Cure Behavior
D6507 Practice for Fiber Reinforcement Orientation Codes for Composite Materials
D7028 Test Method for Glass Transition Temperature (DMA Tg) of Polymer Matrix Composites by Dynamic Mechanical
Analysis (DMA)
E380 Practice for Use of the International System of Units (SI) (the Modernized Metric System) (Withdrawn 1997)
This test method is under the jurisdiction of ASTM Committee D30 on Composite Materials and is the direct responsibility of Subcommittee D30.03 on
Constituent/Precursor Properties.
Current edition approved Nov. 15, 2012Aug. 1, 2017. Published January 2013September 2017. Originally approved in 2012. Last previous edition approved as D7750–12.
DOI: 10.1520/D7750-12.10.1520/D7750-12R17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7750 − 12 (2017)
3. Terminology
3.1 Definitions: For most definitions applicable to this method refer to Terminology D4092.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 Encapsulated Sample Parallel Plate Rheometer—Dynamic Mechanical Analyzer apparatus that holds the specimen under
pressure within a confined cavity. The apparatus is designed to contain the resin within the specimen throughout the progress of
the cure.
4. Summary of Test Method
4.1 A small circular specimen is assembled from uncured thermoset resin materials that correspond to a representation of a
composite part. This specimen is placed in mechanical oscillation at a fixed frequency at either isothermal conditions, a linear
temperature increase or a time-temperature relation simulating a processing condition. The lower plate oscillates and transmits
torque from the lower plate through the sample into the upper plate. The resulting torque measured at the upper plate is converted
to shear modulus using equations that compensate for the shape and size of the sample. The shear modulus is separated into a
component that is in phase with the applied strain or elastic shear modulus and a component that is 90° out of phase with the
applied strain or loss shear modulus. The elastic and loss modulus of the specimen are measured as a function of time. During cure,
the elastic shear modulus will initially decrease as the temperature is increased due to a decrease in the viscosity of the resin in
the sample. When cure occurs in the sample, the elastic shear modulus increases.
5. Significance and Use
5.1 This method provides a simple means of characterizing the cure behavior of a thermosetting resin specimen that is a
representation of a composite part. The diameter of the specimen is approximately 38 mm and the thickness ranges from 2.6 to
3.2 mm. This corresponds to a sample volume of approximately 3 to 4 cm . The data may be used for quality control, research
and development, and verifying the cure within processing equipment including autoclaves.
5.2 Dynamic mechanical testing provides a sensitive method for determining cure characteristics by measuring the elastic and
loss moduli as a function of temperature or time, or both. Plots of cure behavior and tan delta of a material provide graphical
representation indicative of cure behavior under a specified time-temperature profile. The presence of fibers within the resin may
change the dynamic properties measured within a material. However, it is still possible to compare different resins with the same
fiber structure and obtain the relative difference due to the resin cure properties.
5.3 This method can be used to assess the following:
5.3.1 Cure behavior, as well as changes as a function of temperature or time, or both,
5.3.2 Processing behavior, as well as changes as a function of temperature or time, or both,
5.3.3 The effects of processing treatments,
5.3.4 Relative resin behavioral properties, including cure behavior, damping and impact resistance,
5.3.5 The effects of reinforcement on cure.
5.3.6 The effects of materials used to bond the resin and reinforcement,
5.3.7 The effect of formulation additives that might affect processability or performance.
5.4 This provides a method to assess the cure properties of a thermosetting resin containing woven fiber or other reinforcing
materials.
5.5 This method is valid for a wide range of oscillation frequencies typically from 0.002 to 50 Hz.
NOTE 1—It is recommended that low-frequency test conditions, generally 1 to 2 Hz, be used to generate more definitive cure-behavior information.
Slower frequencies will miss important cure properties. Faster frequencies will reduce sensitivity to cure.
6. Interferences
6.1 Apparent discrepancies in results may arise when using different experimental conditions. These apparent differences from
results observed in another study can usually be reconciled without changing the observed data, by reporting in full (as described
in this method) the conditions under which the data were obtained. One essential condition within this method that must be noted
is the presence of pressure within the specimen chamber which ensures good precision.
6.2 In many cases, the specimens made with this method will be significantly smaller than the parts in production. It is essential
that specimens be made from representative samples of uncured material used to make parts. This will ensure that the data is
representative of the part cure.
6.3 The result is a response to the thermal advancement or cure behavior of the resin. The cure behavior is also influenced by
the reinforcement and materials used to enhance the bond between the resin and reinforcement. The reinforcement can be a fiber
or a filler.
6.4 The data will represent the cure of the system at the measured temperature. Parts are often significantly thicker than the
specimen. There may be a significant difference between the temperature versus time profile on the inside and the outside of those
D7750 − 12 (2017)
composite parts. Thermocouples can be used to measure both temperatures during a cure process of a thick part. The measured
temperature versus time data can be used to define temperature versus time profiles for dynamic cure specimens using the
procedures of this standard. The results can be used to compare the cure response for the inside and the outside of the composite
part.
7. Apparatus
7.1 The function of the apparatus is to hold a resin specimen with inert reinforcement, such as fibers, under pressure and yet
prevent the escape of resin. Thereby, the fiber to resin ratio will remain constant throughout the test. The material acts as the elastic
and dissipative element in a mechanically driven oscillatory shear system. This dynamic mechanical instrument operates in
torsional shear using one of the following modes for measuring cure behavior:
7.1.1 Forced, constant amplitude, fixed frequency,
7.1.2 Forced, variable amplitude, fixed frequency.
7.2 The apparatus shall consist of the following:
7.2.1 Parallel plates with serrated or radial grooved surfaces. The diameter of the dies shall be 40 6 2 mm. The depth of the
grooves shall be limited to 1.0 mm or less to keep a constant fiber to resin ratio.
7.2.2 Encapsulated Specimen Cavity—The specimen shall be encapsulated by the two parallel plates and a series of mechanical
components at the outer plate diameter designed to contain the specimen under pressure without loss of resin. These components
shall include an O-ring inserted at the outer diameter of the specimen (Fig. 1). The O-ring meets ASTM International size No.
2-127.
7.2.3 Plate Gap—The thickness of the sample shall range from 2.6 to 3.2 mm. The calculation of the sample modulus will
include corrections to the actual sample thickness.
7.2.4 Plate Closing Mechanism—The system shall apply a pressure of at least 4200 kPa to the sample to prevent slippage.
7.2.5 Plate Oscillating System (Strain Device)—The plate oscillating system shall consist of a direct drive motor that imparts
a torsional oscillating movement to the lower plate in the cavity plane. The movement shall produce a continuous oscillatory
deformation (strain) on the specimen. The deformation (strain) shall be sinusoidal and shall be applied and released continuously
as in a forced-vibration device (see Table 1 of Practice D4065) to provide a continuous measurement of material state. The
preferred amplitude ranges shall be from 6 0.005 to 6 0.060°. The resulting strain at the nominal specimen thickness will range
from 6 0.07 to 6 0.8 %.
NOTE 2—The preferred strain for measuring the cure properties of thermoset resins is 6 0.7 %.
7.2.6 Detectors—A device or devices for determining dependent and independent experimental parameters, such as torque,
frequency, strain amplitude and temperature. Temperature shall be measurable with a precision of 6 0.3°C at the outer diameter
of the plate, frequency to 60.1 % and torque to 6 0.001 Nm.
7.2.7 Temperature Controller—A device for directly heating and cooling the plates with the ability to control the temperature
of the plates. The temperature can increase in steps or a linear ramp or cool in steps or a linear ramp. Fig. 2 illustrates a typical
time-temperature profile for measuring cure properties. A temperature control system shall be sufficiently stable to permit
measurement of plate temperature to within 6 0.3°C during heating and 6 1°C during cooling. Fig. 2 also shows that the
temperature in the part often deviates from the recommended temperature profile. The apparatus shall process a specimen using
either the recommended temperature profile or the actual temperature profile in the part depending on the specification of the test
requestor. The report shall contain a comment indicating which type of temperature profile was used.
7.3 The system must have instrument compliance compensation to ensure a good measure for the final modulus values during
cure.
8. Sampling and Test Specimens
8.1 The neat resin or the resin with reinforcement should be representative of the polymeric material being tested.
FIG. 1 Encapsulated specimen parallel plate rheometer plate system designed to keep a constant fiber to resin ratio during a test.
D7750 − 12 (2017)
NOTE 1—There is often a discrepancy between the typical temperature program and the actual temperature.
FIG. 2 Typical temperature program to cure components and the actual temperature at the component.
8.2 The recommended specimen diameter for this apparatus is 38 6 0.5 mm (Fig. 3) or a diameter recommended by the
apparatus manufacturer. Several 38-mm disks of uncured material shall be laid up to produce a specimen for testing. The
reinforcement type and lay-up shall be recorded in accordance with the laminate orientation code of Practice D6507. The number
of disks required to produce a specimen will vary with the type of fiber and fiber architecture. A good initial value for the thickness
before compressing the sample is 4 mm. The final cured specimen should have a thickness of 2.6 to 3.2 mm after a test is complete.
The apparatus will often compress or reduce the initial thickness into the preferred range of a tested specimen. The number of disks
may vary with the resin and fiber present in a specimen. The weight of the specimen can be used in place of the thickness as an
alternate method to ensure that the final specimen has the preferred thickness at the end of a test.
...