ASTM D7750-12
(Test Method)Standard Test Method for Cure Behavior of Thermosetting Resins by Dynamic Mechanical Procedures using an Encapsulated Specimen Rheometer
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 use...
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.
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Designation: D7750 − 12
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 2. Referenced Documents
2.1 ASTM Standards:
1.1 This method covers the use of dynamic mechanical
D3878 Terminology for Composite Materials
instrumentation for determination and reporting of the thermal
D4000 Classification System for Specifying Plastic Materi-
advancement of cure behavior of thermosetting resin on an
als
inert filler or fiber in a laboratory. It may also be used for
D4065 Practice for Plastics: Dynamic Mechanical Proper-
determining the cure properties of filled resins and resins
ties: Determination and Report of Procedures
without reinforcements. These encapsulated specimens are
D4092 Terminology for Plastics: Dynamic Mechanical
deformed in torsional shear using dynamic mechanical meth-
Properties
ods.
D4473 Test Method for Plastics: Dynamic Mechanical Prop-
1.2 This method is intended to provide means for determin-
erties: Cure Behavior
ing the cure behavior of thermosetting resins on fibers over a
D6507 Practice for Fiber Reinforcement Orientation Codes
range of temperatures from room temperature to 250°C by
for Composite Materials
forced-constant amplitude techniques (in accordance with
D7028 TestMethodforGlassTransitionTemperature(DMA
Practice D4065). Plots of complex modulus, complex
Tg) of Polymer Matrix Composites by Dynamic Mechani-
viscosity, and damping ratio or tan delta as a function of time
cal Analysis (DMA)
or temperature, or both, quantify the thermal advancement or
E380 Practice for Use of the International System of Units
cure characteristics of a resin or a resin on fiber.
(SI) (the Modernized Metric System) (Withdrawn 1997)
1.3 Test data obtained by this method is relevant and
3. Terminology
appropriate for optimizing cure cycles.
3.1 Definitions: For most definitions applicable to this
1.4 The values stated in SI units are to be regarded as
method refer to Terminology D4092.
standard. No other units of measurement are included in this
standard. 3.2 Definitions of Terms Specific to This Standard:
1.4.1 Exception—The fahrenheit temperature measurement 3.2.1 Encapsulated Sample Parallel Plate Rheometer—
in 10.1 is provided for information only and is not considered Dynamic Mechanical Analyzer apparatus that holds the speci-
standard. men under pressure within a confined cavity. The apparatus is
designed to contain the resin within the specimen throughout
1.5 This standard does not purport to address all of the
the progress of the cure.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4. Summary of Test Method
priate safety and health practices and determine the applica-
4.1 A small circular specimen is assembled from uncured
bility of regulatory limitations prior to use.
thermoset resin materials that correspond to a representation of
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This test method is under the jurisdiction of ASTM Committee D30 on contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Composite Materials and is the direct responsibility of Subcommittee D30.03 on Standards volume information, refer to the standard’s Document Summary page on
Constituent/Precursor Properties. the ASTM website.
Current edition approved Nov. 15, 2012. Published January 2013. DOI: 10.1520/ The last approved version of this historical standard is referenced on
D7750-12.
www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7750 − 12
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
simulating a processing condition. The lower plate oscillates
6.1 Apparent discrepancies in results may arise when using
and transmits torque from the lower plate through the sample
different experimental conditions. These apparent differences
intotheupperplate.Theresultingtorquemeasuredattheupper
from results observed in another study can usually be recon-
plate is converted to shear modulus using equations that
ciled without changing the observed data, by reporting in full
compensate for the shape and size of the sample. The shear
(as described in this method) the conditions under which the
modulus is separated into a component that is in phase with the
data were obtained. One essential condition within this method
applied strain or elastic shear modulus and a component that is
that must be noted is the presence of pressure within the
90° out of phase with the applied strain or loss shear modulus.
specimen chamber which ensures good precision.
The elastic and loss modulus of the specimen are measured as
6.2 In many cases, the specimens made with this method
a function of time. During cure, the elastic shear modulus will
will be significantly smaller than the parts in production. It is
initially decrease as the temperature is increased due to a
essential that specimens be made from representative samples
decrease in the viscosity of the resin in the sample. When cure
of uncured material used to make parts. This will ensure that
occurs in the sample, the elastic shear modulus increases.
the data is representative of the part cure.
5. Significance and Use
6.3 The result is a response to the thermal advancement or
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
from 2.6 to 3.2 mm. This corresponds to a sample volume of
6.4 The data will represent the cure of the system at the
approximately 3 to 4 cm . The data may be used for quality
measuredtemperature.Partsareoftensignificantlythickerthan
control, research and development, and verifying the cure
the specimen. There may be a significant difference between
within processing equipment including autoclaves.
the temperature versus time profile on the inside and the
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.Themeasuredtemperatureversustimedatacanbeusedto
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
relative difference due to the resin cure properties.
7.1 Thefunctionoftheapparatusistoholdaresinspecimen
5.3 This method can be used to assess the following: with inert reinforcement, such as fibers, under pressure and yet
5.3.1 Cure behavior, as well as changes as a function of prevent the escape of resin.Thereby, the fiber to resin ratio will
temperature or time, or both, remain constant throughout the test. The material acts as the
5.3.2 Processing behavior, as well as changes as a function elastic and dissipative element in a mechanically driven
of temperature or time, or both,
oscillatory shear system. This dynamic mechanical instrument
5.3.3 The effects of processing treatments, operates in torsional shear using one of the following modes
5.3.4 Relative resin behavioral properties, including cure for measuring cure behavior:
behavior, damping and impact resistance,
7.1.1 Forced, constant amplitude, fixed frequency,
5.3.5 The effects of reinforcement on cure.
7.1.2 Forced, variable amplitude, fixed frequency.
5.3.6 The effects of materials used to bond the resin and
7.2 The apparatus shall consist of the following:
reinforcement,
7.2.1 Parallel plates with serrated or radial grooved sur-
5.3.7 The effect of formulation additives that might affect
faces. The diameter of the dies shall be 40 6 2 mm. The depth
processability or performance.
of the grooves shall be limited to 1.0 mm or less to keep a
5.4 This provides a method to assess the cure properties of
constant fiber to resin ratio.
a thermosetting resin containing woven fiber or other reinforc-
7.2.2 Encapsulated Specimen Cavity—The specimen shall
ing materials.
be encapsulated by the two parallel plates and a series of
5.5 This method is valid for a wide range of oscillation
mechanical components at the outer plate diameter designed to
frequencies typically from 0.002 to 50 Hz.
contain the specimen under pressure without loss of resin.
These components shall include an O-ring inserted at the outer
NOTE 1—It is recommended that low-frequency test conditions, gener-
diameter of the specimen (Fig. 1). The O-ring meets ASTM
ally 1 to 2 Hz, be used to generate more definitive cure-behavior
information. Slower frequencies will miss important cure properties. International size No. 2-127.
D7750 − 12
FIG. 1 Encapsulated specimen parallel plate rheometer plate system designed to keep a constant fiber to resin ratio during a test.
7.2.3 Plate Gap—The thickness of the sample shall range 7.2.6 Detectors—A device or devices for determining de-
from 2.6 to 3.2 mm. The calculation of the sample modulus pendent and independent experimental parameters, such as
will include corrections to the actual sample thickness. torque, frequency, strain amplitude and temperature. Tempera-
7.2.4 Plate Closing Mechanism—The system shall apply a ture shall be measurable with a precision of 6 0.3°C at the
pressure of at least 4200 kPa to the sample to prevent slippage.
outer diameter of the plate, frequency to 60.1 % and torque to
7.2.5 Plate Oscillating System (Strain Device)—The plate 6 0.001 Nm.
oscillating system shall consist of a direct drive motor that
7.2.7 Temperature Controller—Adevice for directly heating
imparts a torsional oscillating movement to the lower plate in
and cooling the plates with the ability to control the tempera-
the cavity plane. The movement shall produce a continuous
ture of the plates. The temperature can increase in steps or a
oscillatory deformation (strain) on the specimen.The deforma-
linear ramp or cool in steps or a linear ramp. Fig. 2 illustrates
tion (strain) shall be sinusoidal and shall be applied and
a typical time-temperature profile for measuring cure proper-
releasedcontinuouslyasinaforced-vibrationdevice(seeTable
ties.Atemperature control system shall be sufficiently stable to
1 of Practice D4065) to provide a continuous measurement of
permit measurement of plate temperature to within 6 0.3°C
material state. The preferred amplitude ranges shall be from 6
during heating and 6 1°C during cooling. Fig. 2 also shows
0.005 to 6 0.060°. The resulting strain at the nominal
that the temperature in the part often deviates from the
specimen thickness will range from 6 0.07 to 6 0.8 %.
recommended temperature profile. The apparatus shall process
a specimen using either the recommended temperature profile
NOTE 2—The preferred strain for measuring the cure properties of
thermoset resins is 6 0.7 %. or the actual temperature profile in the part depending on the
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.
D7750 − 12
specification of the test requestor. The report shall contain a cured sample thickness is within the acceptable range. Also,
comment indicating which type of temperature profile was any shape imparted by the plate surface such as grooves must
used. match the corresponding shape on the cured specimen.
7.3 The system must have instrument compliance compen-
9. Calibration and Standardization
sation to ensure a good measure for the final modulus values
9.1 Torque calibration shall be performed in accordance
during cure.
with apparatus manufacturer’s recommendations.
8. Sampling and Test Specimens 9.1.1 Calibrate the torque measurement system of the appa-
ratus whenever the plate seals are changed.
8.1 The neat resin or the resin with reinforcement should be
9.1.2 Torque Calibration Procedure—A reference torque
representative of the polymeric material being tested.
device is required to calibrate the torque measuring system
8.2 The recommended specimen diameter for this apparatus
(Fig. 4).The torque standard is inserted between the oscillating
is 38 6 0.5 mm (Fig. 3) or a diameter recommended by the
and the measuring plate. The reference values for angular
apparatus manufacturer. Several 38-mm disks of uncured
displacement and the corresponding torque shall be established
material shall be laid up to produce a specimen for testing.The
by the manufacturer of the apparatus for each torque standard.
reinforcement type and lay-up shall be recorded in accordance
9.2 Temperature accuracy of the plates shall be verified
with the laminate orientation code of Practice D6507. The
using the apparatus manufacturer’s recommendations.
number of disks required to produce a specimen will vary with
the type of fiber and fiber architecture.Agood initial value for
10. Conditioning
thethicknessbeforecompressingthesampleis4mm.Thefinal
10.1 Store the uncured resin or prepreg material at low
cured specimen should have a thickness of 2.6 to 3.2 mm after
temperatures, approximately –18°C (0°F) or in accordance
a test is complete. The apparatus will often compress or reduce
with the material manufacturer’s instructions, to prolong the
the initial thickness into the preferr
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