ASTM D3171-99
(Test Method)Standard Test Methods for Constituent Content of Composite Materials
Standard Test Methods for Constituent Content of Composite Materials
SCOPE
1.1 This test method covers the determination of the fiber content of resin-matrix composites. The technique used is based on the digestion of the matrix resin by liquid media, which do not attack the fibers excessively.
1.2 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems 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. For specific hazard statements see Section 7.
1.3 The values in SI units are to be regarded as the standard.
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Designation: D 3171 – 99
Standard Test Methods for
Constituent Content of Composite Materials
This standard is issued under the fixed designation D 3171; 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 (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. See Section 9 for
1.1 These test methods determine the constituent content of
additional information.
composite materials by one of two approaches. Method I
physically removes the matrix by digestion or ignition by one
2. Referenced Documents
of seven procedures, leaving the reinforcement essentially
2.1 ASTM Standards:
unaffected and thus allowing calculation of reinforcement or
D 792 Test Methods for Density and Specific Gravity (Rela-
matrix content (by weight or volume) as well as percent void
tive Density) of Plastics by Displacement
volume. Method II, applicable only to laminate materials of
D 883 Terminology Relating to Plastics
known fiber areal weight, calculates reinforcement or matrix
D 1505 Test Method for Density of Plastics by the Density
content (by weight or volume) based on the measured thickness
Gradient Technique
of the laminate. Method II is not applicable to the measurement
D 3878 Terminology of High-Modulus Reinforcing Fibers
of void volume.
and Their Composites
1.1.1 These test methods are primarily intended for two-part
D 5229/D 5229M Test Method for Moisture Absorption
composite material systems. However, special provisions can
Properties and Equilibrium Conditioning of Polymer Ma-
be made to extend these test methods to filled material systems
trix Composite Materials
with more than two constituents, though not all test results can
E 12 Terminology Relating to Density and Specific Gravity
be determined in every case.
of Solids, Liquids, and Gases
1.1.2 The procedures contained within have been designed
E 171 Specification for Standard Atmospheres for Condi-
to be particularly effective for certain classes of polymer or
tioning and Testing Flexible Barrier Materials
metal matrices. The suggested applications are discussed in
E 177 Practice for Use of Terms Precision and Bias in
Section 4, as well as at the start of each procedure.
ASTM Test Methods
1.1.3 Method I assumes that the reinforcement is essentially
E 1309 Guide for the Identification of Composite Materials
unaffected by the digestion or ignition medium. A procedure
in Computerized Material Property Databases
for correction of the results for minor changes in the reinforce-
ment is included. Procedures A through F are based on
3. Terminology
chemical removal of the matrix while Procedure G removes the
3.1 Definitions—Terminology D 3878 defines terms relating
matrix by igniting the matrix in a furnace.
to composite materials. Terminology D 883 defines terms
1.1.4 Method II assumes that the fiber areal weight of the
relating to plastics. Terminology E 12 defines terms relating to
reinforcement material form is known or controlled to an
specific gravity. Practice E 177 defines terms relating to
acceptable tolerance. The presence of voids is not measured.
statistics. In the event of a conflict between terms, Terminology
Eq 9 and 10 assume zero void content to perform the
D 3878 shall have precedence over other documents.
calculation.
3.1.1 fiber content, n—the amount of fiber present in a
1.2 The SI units shown are considered standard.
composite or prepreg expressed either as percent by weight or
1.3 This standard does not purport to address all of the
percent by volume. This is sometimes stated as a fraction. If no
safety concerns, if any, associated with its use. It is the
fillers exist, this is equivalent to reinforcement content.
responsibility of the user of this standard to establish appro-
Annual Book of ASTM Standards, Vol 08.01.
1 3
These test methods are under the jurisdiction of ASTM Committee D30 on Annual Book of ASTM Standards, Vol 15.03.
Composite Materials and are the direct responsibility of Subcommittee D30.04 on Discontinued; see 1995 Annual Book of ASTM Standards, Vol 15.05. Replaced
Lamina and Laminate Test Methods. by Terminology E 1547.
Current edition approved Oct. 10, 1999. Published February 2000. Originally Annual Book of ASTM Standards, Vol 15.09.
e1 6
published as D 3171 – 73. Last previous edition D 3171 – 76 (1990) . Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D3171–99
D 3878 4.1.1 A correction for weight change of the reinforcement or
retention of the matrix may be made (13.3 and 13.4), if this
3.1.2 matrix content, n—the amount of matrix present in a
change is sufficiently reproducible under the conditions of the
composite or prepreg expressed either as percent by weight or
test and has the same value for the reinforcement or matrix
percent by volume. For polymer matrix composites this is resin
content. D 3878 alone as for the constituents in the composite.
3.1.3 reinforcement content, n—the amount of nonmatrix 4.1.1.1 Procedure A, for matrices such as epoxy resin, steel,
material (fiber and filler) in a composite or prepreg expressed
copper, or others digestible by concentrated nitric acid.
either as percent by weight or percent by volume. D 3878
NOTE 1—Many reinforcements are attacked by nitric acid. If reinforce-
3.1.4 resin content, n—See matrix content. D 3878
ment is attacked, an alternative method is recommended, depending on the
3.1.5 void volume, n—the volume in the specimen without
matrix. See Annex A1.
mass, that is identified as neither matrix nor reinforcement.
4.1.1.2 Procedure B, for matrices such as epoxy, phenolic,
D 3878
polyamide, or thermoplastic resin, or others digestible by an
3.2 Definitions of Terms Specific to This Standard:
23°C
aqueous mixture of sulfuric acid and hydrogen peroxide. See
3.2.1 density, r —the weight per unit volume measured
Annex A2.
in air, of the impermeable portion of a material at 23°C.
4.1.1.3 Procedure C, for matrices such as epoxy resin and
3.2.1.1 Discussion—The definition of specific gravity and
others digestible by a mixture of ethylene glycol and potassium
density are essentially equivalent to the definitions of apparent
hydroxide. See Annex A3.
specific gravity and apparent density in Terminology E 12,
because no correction is made for buoyancy of the material in
NOTE 2—Procedure C is especially applicable to anhydride-cured
air. However, this difference is insignificant for most engineer-
epoxy systems containing aramid or carbon reinforcement.
ing purposes.
23°C
4.1.1.4 Procedure D, for matrices such as aluminum, brass,
3.2.2 specific gravity, SG —the ratio of the weight in air
or others digestible by sodium hydroxide solution. See Annex
of a unit volume of the impermeable portion of a material at
A4.
23°C referenced to the standard unit volume weight of water at
4.1.1.5 Procedure E, for matrices such as steel, titanium,
23°C.
copper, aluminum, or others digestible by hydrochloric acid.
3.3 Symbols:
See Annex A5.
4.1.1.6 Procedure F, a version of Procedure A for
A = area of the specimen.
microwave-aided heating. See Annex A6.
A = calculated mass of one layer of reinforcement/unit
r
4.1.1.7 Procedure G, for reinforcements such as glass, or
area.
ceramic that are not affected by high-temperature environ-
r = density of the composite specimen.
c
ments, or reinforcements such as carbon where temperature is
r = density of the cured matrix.
m
adequately controlled so that reinforcement does not char. See
r = density of the reinforcement or fiber.
r
Annex A7.
h = thickness of the specimen.
M = mass of the dry crucible or sintered glass filter.
4.2 Test Method II—The thickness of a relatively flat panel
c
M = mass of the dry crucible or sintered glass filter with
cr made with reinforcement of known and consistent areal weight
reinforcement residue.
is measured. By the thickness of the panel, the reinforcement
M = initial mass of specimen before digestion or com-
i and matrix content is calculated.
bustion.
M = final mass of specimen after digestion or combus-
f
5. Significance and Use
tion.
5.1 A constituent content of a composite material must be
V = volume percent of matrix in specimen.
m
known in order to analytically model the material properties
V = volume percent of reinforcement in the specimen.
r
(mechanical, physical, thermal, or electrical) of the composite
V = void volume percent in the specimen.
v
W = weight percent of matrix in the specimen. which are affected by the reinforcement or matrix. Also,
m
W = weight percent of reinforcement in the specimen. knowledge of the constituent content is required for evaluation
r
of the quality of a fabricated material and the processes used
4. Summary of Test Method during fabrication.
5.2 The void volume of a composite material may signifi-
4.1 Test Method I—The matrix portion of a material speci-
cantly affect some of its mechanical properties. Higher void
men of known mass is removed in a hot liquid medium (for
volumes usually mean lower fatigue resistance, greater suscep-
dissolution) or furnace (for combustion). When dissolving in a
tibility to moisture penetration and weathering, and increased
hot liquid medium,the remaining residue, containing the rein-
variation or scatter in strength properties. Knowledge of the
forcement, is then filtered, washed, dried, cooled, and weighed.
void volume of a composite material is desirable as an
The weight percent of the reinforcement is calculated, and
indication of the quality of a composite.
from this value, and if densities of both the composite and the
reinforcement are known, the volume percent is calculated. An 5.3 Reinforcement content may be used to normalize me-
additional calculation for void volume may be made if the chanical properties affected by amount of reinforcement in the
density of the matrix is known or determined. coupon.
D3171–99
6. Interferences 6.6 Micrometer Interface—The thickness of the laminate
continuously changes, particularly for surfaces with a release
6.1 Density of Constituents—Calculation of the void vol-
cloth or irregular surface. Test Method II measures the laminate
ume assumes that reinforcement density and matrix density
at certain areas. The micrometer gives an indication of the
obtained on a lot or material basis are held in the laminate
thickness of the material at a point. The micrometer thickness
sample. There is a normal variation in reinforcement and
measure is dependent on (1) variation in thickness of the panel,
matrix densities that is dependent on the constituent material.
(2) type and diameter of thickness measuring device, (3) ability
This assumption used by the void calculation equations is
to hold panel perpendicular to the measurement device, and (4)
typically minor, changing the void calculation by less than
sensitivity of the measurement device.
0.2 %. One indication of this variation is the possibility of
6.6.1 Ball micrometer geometry tends to give a thickness
obtaining a negative void volume in low-void volume compos-
measure for Test Method II that more closely approximates
ites. If procedural errors can be ruled out, then it is reasonable
fiber volume if there is a rough surface texture than a flat-faced
to believe that constituent density variation is responsible.
micrometer that tends to overstate laminate thickness. For
Negative void content is a physical impossibility, but a
some material forms, such as open weaves, the ball geometry
possibility in these calculations. It is useful to report negative
is not practical, so that a flat face micrometer is recommended.
void contents to assess if constituent density values are
incorrect or within a typical range of material variation. The
7. Apparatus
negative void value then sets an upper bound on error of this
test method for any material.
7.1 General Requirements:
6.2 Coupon Size—Ability to estimate void content is also
7.1.1 Thermal Shock—Laboratory equipment, which is sub-
determined by coupon size and limitations of measuring
jected to nonambient temperatures (hot or cold), shall be of
apparatus. For example, with just limitations of the analytical
tempered glass or polytetrafluoroethylene (PTFE) materials.
balance (accurate to 0.2 mg), a coupon of 0.2 g with a void
7.1.2 Post-Test Elemental Analysis—If a post-test elemental
volume of 1.0 % would have an uncertainty of 10 % (reported
analysis of the reinforcement residue is to be performed,
void volume in the range of 0.9 to 1.1 %) on the void volume
laboratory equipment contacting the specimen shall be con-
calculation as a result of possible balance error. A 1-g sample
structed of PTFE, and specimen cutting performed only by
would have an uncertainty of 2 % in the void volume calcula-
diamond-tipped tools.
tion (reported void volume in the range of 0.98 to 1.02 %)
7.2 General Usage:
because of possible balance error for the same 1.0 % void
7.2.1 Analytical Balance—The analytical balance shall be
volume.
capable of reading to within 60.1 mg.
7,8
6.3 Error in Previous Measures —Ability to estimate void
7.2.2 Laboratory Desiccator.
content is also determined by the accuracy of previous mea-
7.3 Test Method I:
sures. Density measures of constituents and laminate have
7.3.1 Heating Equipment:
some limitations. Good measures of these properties should
7.3.1.1 Constant Heat Source—Heating mantle, hot plate,
have an uncertainty of less than 0.0005 g/mL. For a typical
or controlled temperature bath, capable of heating material to
carbon/epoxy laminate, uncertainty in the void volume because
the required temperature for the particular digestion medium
of the limitation of the constituent density measurement would
and shall be capable of maintaining the temperature to 610°C.
be approximately 1 %.
6.4 Mass Change of Reinforcement—Fibers may lose mass 7.3.1.2 Microwave, capable of maintaining a constant power
by any of the techniques in Test Method I. This may be output. The microwave setup shall include an overpressure
investigated by subjecting the reinforcement without matrix to fail-safe device. Used exclusively for Procedure F (see Annex
the test conditions of the composite. Once the technique is A6).
established for a material, no significant changes are expected 7.3.1.3 Drying Oven, air circulating, capable of maintaining
between samples unless the product or test conditions v
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