ASTM D6856-03(2008)
(Guide)Standard Guide for Testing Fabric-Reinforced "Textile" Composite Materials
Standard Guide for Testing Fabric-Reinforced "Textile" Composite Materials
SIGNIFICANCE AND USE
This guide is intended to serve as a reference for the testing of textile composite materials.
The use of this guide ensures that proper consideration is given to the unique characteristics of these materials in testing. In addition, this guide also assists the user in selecting the best currently available ASTM test method for measurement of commonly evaluated material properties.
SCOPE
1.1 This guide is applicable to the testing of textile composites fabricated using fabric preforms, such as weaves, braids, stitched preforms, and so forth, as the reinforcement. The purpose of this guide is to:
1.1.1 Ensure that proper consideration is given to the unique characteristics of these materials in testing.
1.1.2 Assist the user in selecting the best currently available ASTM test method for the measurement of commonly evaluated material properties for this class of materials.
1.2 Areas where current ASTM test methods do not meet the needs for testing of textile composites are indicated.
1.3 It is not the intent of this guide to cover all test methods which could possibly be used for textile composites. Only the most commonly used and most applicable standards are included.
1.4 The values stated in SI units are to be regarded as the standard. The values in parentheses are 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 and health practices and determine the applicability of regulatory requirements prior to use.
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Designation:D6856–03 (Reapproved 2008)
Standard Guide for
Testing Fabric-Reinforced “Textile” Composite Materials
This standard is issued under the fixed designation D6856; 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 (ϵ) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
A variety of fabric-reinforced composite materials have been developed for use in aerospace,
automotive, and other applications. These composite materials are reinforced with continuous fiber
yarns that are formed into two-dimensional or three-dimensional fabrics.Various fabric constructions,
such as woven, braided, stitched, and so forth, can be used to form the fabric reinforcement. Due to
the nature of the reinforcement, these materials are often referred to as “textile” composites.
Textile composites can be fabricated from 2-dimensional (2-D) or 3-dimensional (3-D) fabrics.
Stitched preforms and 3-D fabrics contain through-thickness yarns, which can lead to greater
delamination resistance. Textile composites are also amenable to automated fabrication. However, the
microstructure (or fiber architecture) of a textile composite, which consists of interlacing yarns, can
lead to increased inhomogeneity of the local displacement fields in the laminate. Depending upon the
size of the yarns and the pattern of the weave or braid, the inhomogeneity within a textile composite
can be large compared to traditional tape laminates.
Thus, special care should be exercised in the use of the currentASTM standards developed for high
performance composites. In many cases, the current ASTM standards are quite adequate if proper
attention is given to the special testing considerations for textile composites covered in this guide.
However, in some cases, current standards do not meet the needs for testing of the required properties.
This guide is intended to increase the user’s awareness of the special considerations necessary for the
testing of these materials. It also provides the user with recommended ASTM standards that are
applicable for evaluating textile composites. The specific properties for which current ASTM
standards might not apply are also highlighted in this guide.
1. Scope 1.3 It is not the intent of this guide to cover all test methods
which could possibly be used for textile composites. Only the
1.1 This guide is applicable to the testing of textile com-
most commonly used and most applicable standards are
posites fabricated using fabric preforms, such as weaves,
included.
braids, stitched preforms, and so forth, as the reinforcement.
1.4 The values stated in SI units are to be regarded as the
The purpose of this guide is to:
standard. The values in parentheses are for information only.
1.1.1 Ensurethatproperconsiderationisgiventotheunique
1.5 This standard does not purport to address all of the
characteristics of these materials in testing.
safety concerns, if any, associated with its use. It is the
1.1.2 Assist the user in selecting the best currently available
responsibility of the user of this standard to establish appro-
ASTM test method for the measurement of commonly evalu-
priate safety and health practices and determine the applica-
ated material properties for this class of materials.
bility of regulatory requirements prior to use.
1.2 Areas where current ASTM test methods do not meet
the needs for testing of textile composites are indicated.
2. Referenced Documents
2.1 ASTM Standards:
This guide is under the jurisdiction of ASTM Committee D30 on Composite
Materials and is the direct responsibility of Subcommittee D30.04 on Lamina and
Laminate Test Methods. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Sept. 1, 2008. Published December 2008. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2003. Last previous edition approved in 2003 as D6856-03. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D6856-03R08. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6856–03 (2008)
D790 Test Methods for Flexural Properties of Unreinforced E251 Test Methods for Performance Characteristics of Me-
and Reinforced Plastics and Electrical Insulating Materials tallic Bonded Resistance Strain Gauges
E456 Terminology Relating to Quality and Statistics
D792 Test Methods for Density and Specific Gravity (Rela-
E1237 GuideforInstallingBondedResistanceStrainGages
tive Density) of Plastics by Displacement
D883 Terminology Relating to Plastics
3. Terminology
D2344/D2344M Test Method for Short-Beam Strength of
3.1 Definitions—Definitions used in this guide are defined
Polymer Matrix Composite Materials andTheir Laminates
by variousASTM methods. Terminology D3878 defines terms
D3039/D3039M Test Method for Tensile Properties of
relating to high-modulus fibers and their composites. Termi-
Polymer Matrix Composite Materials
nologyD883definestermsrelatingtoplastics.TerminologyE6
D3171 Test Methods for Constituent Content of Composite
definestermsrelatingtomechanicaltesting.TerminologyE456
Materials
defines terms relating to statistics. In the event of a conflict
D3410/D3410M Test Method for Compressive Properties
between definitions of terms, Terminology D3878 shall have
of Polymer Matrix Composite Materials with Unsupported
precedenceovertheotherstandards.Termsrelatingspecifically
Gage Section by Shear Loading
to textile composites are defined by Ref (1).
D3479/D3479M Test Method for Tension-Tension Fatigue
3.2 textile unit cell—In theory, textile composites have a
of Polymer Matrix Composite Materials
repeating geometrical pattern based on manufacturing param-
D3518/D3518M Test Method for In-Plane Shear Response
eters.This repeating pattern is often referred to as the materials
of Polymer Matrix Composite Materials by Tensile Test of
“unit cell.” It is defined as the smallest section of architecture
a 645° Laminate
required to repeat the textile pattern (see Figs. 1-4). Handling
D3846 Test Method for In-Plane Shear Strength of Rein-
and processing can distort the “theoretical” unit cell. Param-
forced Plastics
eters such as yarn size, yarn spacing, fabric construction, and
D3878 Terminology for Composite Materials
fiber angle may be used to calculate theoretical unit cell
D4255/D4255M Test Method for In-Plane Shear Properties
dimensions. However, several different “unit cells” may be
of Polymer Matrix Composite Materials by the Rail Shear
defined for a given textile architecture. For example, Fig. 2
Method
shows two different unit cells for the braided architectures.
D5229/D5229M Test Method for Moisture Absorption
Thus, unit cell definition can be somewhat subjective based on
Properties and Equilibrium Conditioning of Polymer Ma-
varying interpretations of the textile architecture. The user is
trix Composite Materials
referred to Refs (1, 2) for further guidance. In this guide, to be
D5379/D5379M Test Method for Shear Properties of Com-
consistent, the term “unit cell” is used to refer to the smallest
posite Materials by the V-Notched Beam Method
unit cell for a given textile architecture. This smallest unit cell
D5528 Test Method for Mode I Interlaminar Fracture is defined as the smallest section of the textile architecture
Toughness of Unidirectional Fiber-Reinforced Polymer required to replicate the textile pattern by using only in-plane
Matrix Composites translations (and no rotations) of the unit cell. Examples of the
smallest unit cells for some of the commonly used textile
D5766/D5766M Test Method for Open-Hole Tensile
composites are shown in Figs. 1-4. For the 3-D weaves in Figs.
Strength of Polymer Matrix Composite Laminates
3and4,thesmallestunitcelllength(asindicated)isdefinedby
D5961/D5961M Test Method for Bearing Response of
the undulating pattern of the warp yarns. The smallest unit cell
Polymer Matrix Composite Laminates
width is the distance between two adjacent warp stuffer yarn
D6115 Test Method for Mode I Fatigue Delamination
columns (in the fill yarn direction) and the smallest unit cell
Growth Onset of Unidirectional Fiber-Reinforced Polymer
height is the consolidated woven composite thickness.
Matrix Composites
D6415 Test Method for Measuring the Curved Beam
4. Significance and Use
StrengthofaFiber-ReinforcedPolymer-MatrixComposite
4.1 This guide is intended to serve as a reference for the
D6272 Test Method for Flexural Properties of Unreinforced
testing of textile composite materials.
and Reinforced Plastics and Electrical Insulating Materials
4.2 The use of this guide ensures that proper consideration
by Four-Point Bending
is given to the unique characteristics of these materials in
D6484/D6484M Test Method for Open-Hole Compressive
testing. In addition, this guide also assists the user in selecting
Strength of Polymer Matrix Composite Laminates
the best currently available ASTM test method for measure-
D6641/D6641M Test Method for Compressive Properties
ment of commonly evaluated material properties.
of Polymer Matrix Composite Materials Using a Com-
bined Loading Compression (CLC) Test Fixture
5. Summary of Guide
D6671/D6671M Test Method for Mixed Mode I-Mode II
5.1 Special testing considerations unique to textile compos-
Interlaminar Fracture Toughness of Unidirectional Fiber
ites are identified and discussed. Recommendations for han-
Reinforced Polymer Matrix Composites
dling these considerations are provided. Special considerations
E6 TerminologyRelatingtoMethodsofMechanicalTesting
E122 Practice for Calculating Sample Size to Estimate,
With Specified Precision, the Average for a Characteristic
The boldface numbers in parentheses refer to the list of references at the end of
of a Lot or Process this standard.
D6856–03 (2008)
FIG. 1 Smallest Unit Cells for Plain Weave and 5-Harness Satin Weave Architectures
FIG. 2 Smallest Unit Cells for a 2-D Braid and a 232, 2-D Triaxial Braid
FIG. 3 Smallest Unit Cell Length for Through-Thickness Angle-Interlock Weave
covered are included in Section 7 on Material Definition; 5.2 RecommendedASTM test methods applicable to textile
Section 8 on Gage Selection; Section 9 on Sampling and Test composites and any special considerations are provided in
Specimens; Section 10 on Test Specimen Conditioning; Sec- Section 12 for mechanical and physical properties. Section 13
tion 11 on Report of Results; and Section 12 on Recommended identifies areas where revised or new standards are needed for
Test Methods. textile composites.
D6856–03 (2008)
FIG. 4 Smallest Unit Cell Length for Layer-to-Layer Angle-Interlock Weave
6. Procedure for Use 7.3.2 As a minimum the following process conditions
should be documented for each material tested: preform
6.1 Review Sections 7-12 to become familiar with the
thickness, preform tackifier (or resin compatible binder) used,
special testing considerations for textile composites.
molding technique, molding temperature, molding pressure,
6.2 Follow the recommended ASTM test method identified
molding time, and panel dimensions.
inSection12fordeterminingarequiredpropertybutreferback
to this guide for recommendations on test specimen geometry,
8. Strain Gage Selection
strain measurement, and reporting of results.
8.1 The surface preparation, gage installation, lead wire
7. Material Definition
connection,andverificationcheckproceduresdescribedinTest
7.1 Constituent Definition—Variations in type and amount
Methods E251 and Guide E1237 are applicable to textile
of sizing on the fibers can significantly influence fabric quality
composites and should be used in the application of bonded
and subsequently material property test results. Each constitu-
resistance strain gages.
ent, that is, the fiber, fiber sizing type and amount, and resin
8.2 The strain gage size selected for each particular textile
should be carefully documented prior to testing to avoid
composite should take into consideration the size of the unit
misinterpretation of test results.
cell for the particular textile composite architecture. Each
7.1.1 Fiber and resin content should be measured and
different textile architecture has an independent unit cell size,
recordedusingatleastoneunitcellofthematerialfromatleast
which defines the extent of inhomogeniety in the displacement
one location in each panel from which test specimens are
fields. The size of the gage should be large enough relative to
machined. Section 12 covers methods for measuring these
the textile unit cell to provide a reliable measurement of the
values.
average strain magnitude. It is recommended for most textile
7.1.2 The following items should be documented each time
architectures that the gage length and width should, at a
a material is tested: fiber type, fiber diameter, fiber surface
minimum, equal the length and width of the smallest unit cell.
treatment or sizing type and amount, and resin type.
This applies to specimens loaded in the axial fiber direction
7.2 Fabric Definition—Due to the limitless possibilities
(longitudinal direction) and to specimens loaded perpendicular
involved in placing yarns during the weaving and braiding
to the axial fibers (transverse direction). For stitched compos-
operations, it is important to carefully document the yarn
ites, it is recommended that the gage length and width should,
counts (or yarn sizes), yarn spacings, yarn orientations, yarn
at a minimum, equal the stitch spacing and stitch pitch,
contents, weave or braid pattern identification, and yarn
respectively. The user is also referred to Ref (3) for further
interlocking through the preform thickness. Such documenta-
guidance.
tion is required to properly define the textile unit cell and also
to properly identify the textile material that was tested and to
9. Sampling and Test Specimens
avoid any possible misinterpretations of the test results.
9.1 Sampling—It is recommended that at least five speci-
7.3 Process Definition—Processing techniques can affect
mens be tested per series unless valid results can be obtained
fiber orientation, void content, and state of polymerization.
using less specimens, such as by using a designed experiment.
Thesefactorscaninturninfluencematerialpropertytestresults
For statistically significant data, the procedure outlined in
significantly. Each of these items should be defined and
Practice E122 should be used and the method of sampling
documented prior to testing to avoid misinterpretation of the
shoul
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