ASTM D3531/D3531M-16

Standard Test Method for Resin Flow of Carbon Fiber-Epoxy Prepreg

SIGNIFICANCE AND USE
5.1 This test method is used to obtain the resin flow of carbon fiber-epoxy prepreg tape or sheet material. It is suitable for comparing lots of material of supposedly the same characteristics and also for comparative evaluation of materials produced by different vendors using different resin-fiber combinations.  
5.2 Composite parts are laminated from prepreg material at various pressures and temperatures. Production process design will require a flow test be run at a temperature and a pressure close to that of the actual molding conditions. All methods of measuring resin flow are dependent on the size and geometry of the specimen. This test method uses the smallest quantity of tape that will give reproducible results.  
5.2.1 The percent resin flow of a single fiber and resin system at a temperature and pressure varies with the volatile content, degree of advancement of epoxy resin, and with the resin content of the prepreg tape or sheet.  
5.2.2 As volatile content and degree of resin cure (advancement) change with time, this test method is useful in comparing the life of prepreg tape and sheet.
SCOPE
1.1 This test method covers the determination of the amount of resin flow that will take place from prepreg tape or sheet under given conditions of temperature and pressure.  
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.  
1.2.1 Within the text, inch-pound units are shown in brackets.  
1.3 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.

General Information

• Status: Published
• Publication Date: 31-Oct-2016
• ICS: 83.120 - Reinforced plastics
• Technical Committee: D30 - Composite Materials
• Drafting Committee: D30.03 - Constituent/Precursor Properties

Relations

• Replaces: ASTM D3531/D3531M-11 - Standard Test Method for Resin Flow of Carbon Fiber-Epoxy Prepreg
• Effective Date: 01-Nov-2016
• Refers: ASTM D883-24 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2024
• Refers: ASTM D883-23 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2023
• Refers: ASTM D883-20 - Standard Terminology Relating to Plastics
• Effective Date: 01-Jan-2020
• Refers: ASTM D3878-19a - Standard Terminology for Composite Materials
• Effective Date: 15-Oct-2019
• Refers: ASTM D883-19c - Standard Terminology Relating to Plastics
• Effective Date: 01-Aug-2019
• Refers: ASTM D3878-19 - Standard Terminology for Composite Materials
• Effective Date: 15-Apr-2019
• Refers: ASTM D883-19a - Standard Terminology Relating to Plastics
• Effective Date: 15-Apr-2019
• Refers: ASTM D883-19 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2019
• Refers: ASTM D883-18a - Standard Terminology Relating to Plastics
• Effective Date: 01-Dec-2018
• Refers: ASTM D883-18 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2018
• Refers: ASTM D3878-18 - Standard Terminology for Composite Materials
• Effective Date: 01-Apr-2018
• Refers: ASTM D883-17 - Standard Terminology Relating to Plastics
• Effective Date: 15-Aug-2017
• Refers: ASTM D3878-16 - Standard Terminology for Composite Materials
• Effective Date: 01-Aug-2016
• Refers: ASTM D3878-15 - Standard Terminology for Composite Materials
• Effective Date: 01-Jul-2015

Overview

ASTM D3531/D3531M-16: Standard Test Method for Resin Flow of Carbon Fiber-Epoxy Prepreg establishes a procedure for determining the resin flow characteristics of carbon fiber-epoxy prepreg tapes and sheets. This method is essential for quality control in composite manufacturing, ensuring consistency in material properties and performance across production lots and suppliers. By specifying standard test conditions, the method allows for accurate comparison and evaluation of prepreg resin flow under controlled temperature and pressure, which are critical for effective composite part fabrication.

Key Topics

• Purpose and Significance

  • Measures the resin flow from carbon fiber-epoxy prepreg tape or sheets under defined temperature and pressure.
  • Enables comparison between different material lots, fiber-resin combinations, and vendor products.
  • Assesses changes in prepreg properties due to storage conditions or aging, supporting shelf-life and processability evaluations.

• Standard Test Procedure

  • Uses a minimum of two plies of prepreg, arranged in a cross-ply configuration, sandwiched with bleeder and separator materials.
  • The assembly is pressed at a specified temperature and pressure, simulating composite molding conditions.
  • The resin flow is quantified as a percentage of the original specimen weight, reflecting the material’s behavior during processing.

• Test Variables and Influences

  • Resin flow is affected by specimen size and geometry, volatile content, resin content, and degree of advance (cure) of the epoxy.
  • Consistent platen pressure and temperature control are crucial for reliable results.
  • Ply orientation, coupon size, and placement of separative materials can impact reported resin flow results.

Applications

• Quality Control in Composite Manufacturing

  • Ensures that carbon fiber-epoxy prepreg materials meet stringent specifications for aerospace, automotive, and industrial applications.
  • Detects material inconsistencies potentially affecting molded part integrity or performance.
  • Supports acceptance criteria for incoming raw materials and release for production use.

• Supplier and Batch Comparison

  • Used to evaluate prepreg batches from multiple vendors or different production runs, ensuring compatibility and uniformity.
  • Aids in vendor qualification and benchmarking.

• Process and Design Validation

  • Helps define molding parameters aligned with the flow characteristics of specific prepreg formulations.
  • Assists engineers in process validation, troubleshooting, and optimization to reduce material waste and improve yield.

• Material Shelf-life Assessment

  • Detects changes in volatile content or resin advancement during storage, contributing to inventory control and material handling best practices.

Related Standards

For comprehensive composite material testing and terminology, ASTM D3531/D3531M-16 references the following ASTM standards:

• ASTM D3878: Terminology for Composite Materials - Definitions specific to composites and high-modulus fibers.
• ASTM D883: Terminology Relating to Plastics - General terms for plastic materials.

Additional related standards:

• Other ASTM D30 composite test methods, addressing wide-ranging constituent and product properties.
• ISO and EN standards for prepreg characterization and composite quality assurance.

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Keywords: resin flow test, carbon fiber-epoxy prepreg, composite material testing, ASTM D3531/D3531M-16, prepreg quality control, resin-fiber evaluation, standard test method, composite manufacturing standards.

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: D3531/D3531M − 16
Standard Test Method for
Resin Flow of Carbon Fiber-Epoxy Prepreg
This standard is issued under the fixed designation D3531/D3531M; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope 3.2.2 W —weight of the prepreg specimen prior to flow test
1.1 Thistestmethodcoversthedeterminationoftheamount
3.2.3 W —weightofthespecimenassemblypriortoheating
of resin flow that will take place from prepreg tape or sheet
3.2.4 W —weight of the specimen assembly after heating
under given conditions of temperature and pressure.
3.2.5 W —weight of the prepreg specimen after flow test
1.2 The values stated in either SI units or inch-pound units
are to be regarded separately as standard. The values stated in
4. Summary of Test Method
each system may not be exact equivalents; therefore, each
system shall be used independently of the other. Combining
4.1 Aweighed specimen consisting of two plies a minimum
values from the two systems may result in non-conformance size of 50-mm [2.0-in.] square, oriented in a 0°/ 90° crossply
with the standard.
configuration, and sandwiched between bleeder material and
1.2.1 Within the text, inch-pound units are shown in brack- release film.The sandwich is placed in a platen press heated to
ets.
either temperatureA, 120°C [250°F], or temperature B, 175°C
[350°F]oranotherspecifiedtemperature.Thepressisclosedto
1.3 This standard does not purport to address all of the
provide a pressure of 700 kPa [100 psi]. The pressure is held
safety concerns, if any, associated with its use. It is the
for 15 min or until the resin gels. The cooled sandwich
responsibility of the user of this standard to establish appro-
assembly is removed and the resin that has flowed to the edges
priate safety and health practices and determine the applica-
of the specimen is removed and the specimen reweighed. The
bility of regulatory limitations prior to use.
change in weight is expressed as a percent of the original
weight and reported as percent flow.
2. Referenced Documents
2.1 ASTM Standards:
5. Significance and Use
D883Terminology Relating to Plastics
D3878Terminology for Composite Materials 5.1 This test method is used to obtain the resin flow of
carbon fiber-epoxy prepreg tape or sheet material. It is suitable
3. Terminology
for comparing lots of material of supposedly the same charac-
teristics and also for comparative evaluation of materials
3.1 Definitions—Terminology D3878 defines terms relating
produced by different vendors using different resin-fiber com-
to high-modulus fibers and their composites. Terminology
binations.
D883 defines terms relating to plastics. In the event of a
conflict between terms, Terminology D3878 shall have prece-
5.2 Composite parts are laminated from prepreg material at
dence over other standards.
various pressures and temperatures. Production process design
will require a flow test be run at a temperature and a pressure
3.2 Symbols:
close to that of the actual molding conditions. All methods of
3.2.1 RF—resin flow
measuring resin flow are dependent on the size and geometry
of the specimen.This test method uses the smallest quantity of
1 tape that will give reproducible results.
This test method is under the jurisdiction of ASTM Committee D30 on
Composite Materials and is the direct responsibility of Subcommittee D30.03 on
5.2.1 The percent resin flow of a single fiber and resin
Constituent/Precursor Properties.
system at a temperature and pressure varies with the volatile
Current edition approved Nov. 1, 2016. Published November 2016. Originally
content, degree of advancement of epoxy resin, and with the
approved in 1976. Last previous edition approved in 2011 as D3531–11. DOI:
10.1520/D3531_D3531M-16. resin content of the prepreg tape or sheet.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
5.2.2 As volatile content and degree of resin cure (advance-
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
ment)changewithtime,thistestmethodisusefulincomparing
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. the life of prepreg tape and sheet.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3531/D3531M − 16
6. Interferences 7.6 TFE-Fluorocarbon Coated, Woven Separator
Cloth, porous.
6.1 Thistestmethoddependsonplatenforcebeingsupplied
7.7 Release Film of 0.03 to 0.06 mm [0.001 to 0.002 in.]
evenly to the specimen. For this to be done, the platen must
thickness polyester, aluminum, etc.
load evenly across its surface and not point load to the point of
initial contact. When bleeder materials are used on the top and
7.8 PlatenPress,capableofbeingheatedto175 63°C[350
bottom of the specimen, the effect of uneven pressure applica-
6 5°F] and capable of applying 4000 N [900 lbf].
tion is less pronounced than if no bleeder materials are used.
Bleeders tend to minimize pressure effects, since if resin flows
8. Test Specimen
into the bleeder it will do so within a broad pressure range.
8.1 Aminimum of three specimens shall be tested for each
Sometimes, platen pressure needs to be increased gradually to
sample.
assure even loading.
8.2 The test specimen shall consist of two plies, one at 0°
6.2 Theplatenflatnessmustbesufficientforthespecimento
and the other at 90° of 50-mm [2-in.] square minimum size
load evenly. For this reason the specimen thickness should be
prepreg sheet.
at least five times the tolerance of platen flatness. Specimens
that do not meet this requirement should have additional ply
9. Conditioning
layers oriented as a repeating unit of the first two plies.
9.1 Store carbon fiber-epoxy prepreg tape at low
6.3 Ply orientation and coupon size directly affects reported
temperatures, approximately−18°C [0°F], to prolong the use-
flow. A sample cut with a ply orientation of 45° will not have
fulness of the material. Allow the sealed packages of material
the same reported flow as a sample cut with a ply orientation
to warm to ambient temperature before the seal is opened to
of 0°. This is because flow paths are hindered to a different
ensure that the material does not absorb moisture from the
degree based on the different coupon size and orientation.
atmosphere.
6.4 Temperature should be even across the specimen and 9.2 Do not expose the material, which usually has some
within the tolerance specified. Temper
...

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: D3531/D3531M − 11 D3531/D3531M − 16
Standard Test Method for
Resin Flow of Carbon Fiber-Epoxy Prepreg
This standard is issued under the fixed designation D3531/D3531M; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope
1.1 This test method covers the determination of the amount of resin flow that will take place from prepreg tape or sheet under
given conditions of temperature and pressure.
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformance with the standard.
1.2.1 Within the text, inch-pound units are shown in brackets.
1.3 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.
2. Referenced Documents
2.1 ASTM Standards:
D883 Terminology Relating to Plastics
D3878 Terminology for Composite Materials
3. Terminology
3.1 Definitions—Terminology D3878 defines terms relating to high-modulus fibers and their composites. Terminology D883
defines terms relating to plastics. In the event of a conflict between terms, Terminology D3878 shall have precedence over other
standards.
3.2 Symbols:
3.2.1 RF—resin flow
3.2.2 W —weight of the prepreg specimen prior to flow test
3.2.3 W —weight of the specimen assembly prior to heating
3.2.4 W —weight of the specimen assembly after heating
3.2.5 W —weight of the prepreg specimen after flow test
4. Summary of Test Method
4.1 A weighed specimen consisting of two plies a minimum size of 50-mm [2.0-in.] square, oriented in a 0°/ 90° crossply
configuration, and sandwiched between bleeder material and release film. The sandwich is placed in a platen press heated to either
temperature A, 120°C [250°F], or temperature B, 175°C [350°F] or another specified temperature. The press is closed to provide
a pressure of 700 kPa [100 psi]. The pressure is held for 15 min or until the resin gels. The cooled sandwich assembly is removed
and the resin that has flowed to the edges of the specimen is removed and the specimen reweighed. The change in weight is
expressed as a percent of the original weight and reported as percent flow.
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 Oct. 1, 2011Nov. 1, 2016. Published November 2011November 2016. Originally approved in 1976. Last previous edition approved in 20092011
as D3531 – 99D3531 – 11.(2009). DOI: 10.1520/D3531_D3531M-11.10.1520/D3531_D3531M-16.
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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3531/D3531M − 16
5. Significance and Use
5.1 This test method is used to obtain the resin flow of carbon fiber-epoxy prepreg tape or sheet material. It is suitable for
comparing lots of material of supposedly the same characteristics and also for comparative evaluation of materials produced by
different vendors using different resin-fiber combinations.
5.2 Composite parts are laminated from prepreg material at various pressures and temperatures. Production process design will
require a flow test be run at a temperature and a pressure close to that of the actual molding conditions. All methods of measuring
resin flow are dependent on the size and geometry of the specimen. This test method uses the smallest quantity of tape that will
give reproducible results.
5.2.1 The percent resin flow of a single fiber and resin system at a temperature and pressure varies with the volatile content,
degree of advancement of epoxy resin, and with the resin content of the prepreg tape or sheet.
5.2.2 As volatile content and degree of resin cure (advancement) change with time, this test method is useful in comparing the
life of prepreg tape and sheet.
4. Apparatus
4.1 Cutting Template, square metal, 50 by 50 mm [2.0 by 2.0 in.], minimum.
4.2 Cutting Template, metal, 100 by 100 mm [4.0 by 4.0 in.], minimum.
4.3 Cutting Knife, single edge.
4.4 Analytical Balance capable of weighing to the nearest 0.001 g [0.000035 oz].
4.5 Glass Bleeder Cloth, Style 1581 or 181.
D3531/D3531M − 16
4.6 TFE-Fluorocarbon Coated, Woven Separator Cloth, porous.
4.7 Release Film of 0.03 to 0.06 mm [0.001 to 0.002 in.] thickness polyester, aluminum, etc.
4.8 Platen Press, capable of being heated to 175 6 3°C [350 6 5°F] and capable of applying 4000 N [900 lbf].
6. Interferences
6.1 This test method depends on platen force being supplied evenly to the specimen. For this to be done, the platen must load
evenly across its surface and not point load to the point of initial contact. When bleeder materials are used on the top and bottom
of the specimen, the effect of uneven pressure application is less pronounced than if no bleeder materials are used. Bleeders tend
to minimize pressure effects, since if resin flows into the bleeder it will do so within a broad pressure range. Sometimes, platen
pressure needs to be increased gradually to assure even loading.
6.2 The platen flatness must be sufficient for the specimen to load evenly. For this reason the specimen thickness should be at
least five times the tolerance of platen flatness. Specimens that do not meet this requirement should have additional ply layers
oriented as a repeating unit of the first two plies.
6.3 Ply orientation and coupon size directly affects reported flow. A sample cut with a ply orientation of 45° will not have the
same reported flow as a sample cut with a ply orientation of 0°. This is because flow paths are hindered to a different degree based
on the different coupon size and orientation.
6.4 Temperature should be even across the specimen and within the tolerance specified. Temperature influences resin viscosity,
which effects flow rate.
6.5 Generally, larger coupon sizes reduce lateral flow since resin has further to travel to the edge of the specimen. Larger coupon
sizes do not greatly influence horizontal flow (with bleeders). However, difficulty in coupon handleability increases with increasing
coupon size. Also small coupon size of 50 mm [2.0 in.] square is felt to be the minimum coupon size. A maximum practical size
is 100 mm [4.0
...