ASTM D5229/D5229M-20

Standard Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite Materials

SIGNIFICANCE AND USE
5.1 Procedure A is designed to produce moisture diffusion material property data that may be used as follows:  
5.1.1 To determine approximate exposure times for coupon conditioning in Procedures B-E, Y, and Z;  
5.1.2 As input to moisture prediction analysis computer codes; or  
5.1.3 For making qualitative decisions on material selection or performance under environmental exposure to various forms of moisture.  
5.2 Procedures B-E are designed to condition test coupons to a specified environmental condition or equilibrium state prior to other material property testing (including, but not limited to, mechanical testing).  
5.3 Procedures Y-Z are designed to determine the loss of moisture content due to removal of a test coupon from the conditioning chamber (such as for strain gauge bonding) or due to heating of the test coupon prior to and during mechanical loading.  
5.4 A single pair of tests on thin and thick specimens using Procedure A provides the moisture diffusivity constant, Dz, and the moisture equilibrium content, Mm, at the given moisture exposure level and temperature. Multiple tests at differing temperatures are required to establish the dependence of Dz on temperature. Multiple tests at differing moisture exposure levels are required to establish the dependence of Mm on moisture exposure level.
Note 1: For many polymer matrix composites, the moisture diffusivity is usually only weakly related to relative humidity and is often assumed to be a function only of temperature, usually following an Arrhenius-type exponential relation with inverse absolute temperature. For many of these materials, moisture equilibrium content is only weakly related to temperature and is usually assumed to be a function only of relative humidity (1).  
5.5 Vapor-exposure testing shall be used to condition the specimen when the in-service environmental condition is a vapor such as humid air. Immersion in a liquid bath should be used to simulate vapor exposure only whe...
SCOPE
1.1 This test method covers a procedure for the determination of moisture absorption or desorption properties in the through-the-thickness direction for single-phase Fickian solid materials in flat or curved panel form. Also covered are procedures for conditioning test coupons prior to use in other test methods; either to an essentially moisture-free state, to equilibrium in a standard laboratory atmosphere environment, or to equilibrium in a non-laboratory environment. Also included are procedures for determining the moisture loss during elevated temperature testing, as well as moisture loss resulting from thermal exposure after removal from the conditioning environment, such as during strain gauge bonding. While intended primarily for laminated polymer matrix composite materials, these procedures are also applicable to other materials that satisfy the assumptions of 1.2.  
1.2 The calculation of the through-the-thickness moisture diffusivity constant in Procedure A assumes a single-phase Fickian material with constant moisture absorption properties through the thickness of the specimen. The validity of the equations used in Procedure A for evaluating the moisture diffusivity constant in a material of previously unknown moisture absorption behavior is uncertain prior to the test, as the test results themselves determine if the material follows the single-phase Fickian diffusion model. A reinforced polymer matrix composite material tested below its glass-transition temperature typically meets this requirement, although two-phase matrices such as toughened epoxies may require a multi-phase moisture absorption model. While the test procedures themselves may be used for multi-phase materials, the calculations used to determine the moisture diffusivity constant in Procedure A are applicable only to single-phase materials. Other examples of materials and test conditions that may not meet the requirements are discussed in Sec...

General Information

• Status: Published
• Publication Date: 29-Feb-2020
• ICS: 83.140.20 - Laminated sheets
• Technical Committee: D30 - Composite Materials
• Drafting Committee: D30.04 - Lamina and Laminate Test Methods

Relations

• Replaces: ASTM D5229/D5229M-14e1 - Standard Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite Materials
• Effective Date: 01-Mar-2020
• 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 D2734-23 - Standard Test Methods for Void Content of Reinforced Plastics
• Effective Date: 01-Oct-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 D883-19a - Standard Terminology Relating to Plastics
• Effective Date: 15-Apr-2019
• Refers: ASTM D3878-19 - Standard Terminology for Composite Materials
• 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 D2584-18 - Standard Test Method for Ignition Loss of Cured Reinforced Resins
• Effective Date: 15-Sep-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

Overview

ASTM D5229/D5229M-20 is the Standard Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite Materials, developed by ASTM International. This standard establishes procedures for determining how polymer matrix composite materials absorb and retain moisture, as well as for conditioning specimens to equilibrium moisture states before further testing. The guidance is essential for industries where the performance and durability of composite materials are affected by varying environmental moisture.

Key Topics

• Moisture Absorption Testing: The standard outlines gravimetric methods for monitoring the change in average moisture content over time in composite material specimens exposed to controlled conditions.
• Equilibrium Conditioning: Procedures are provided to bring test coupons to uniform through-the-thickness moisture profiles, ensuring accurate and consistent material property evaluations.
• Moisture Diffusivity and Equilibrium Content: Procedure A allows calculation of the through-the-thickness moisture diffusivity constant (Dz) and the maximum equilibrium content (Mm) at specific conditions, enabling prediction of moisture behavior in composite materials.
• Material Applicability: Although primarily intended for laminated polymer matrix composites behaving according to single-phase Fickian diffusion, the procedures can be adapted for other solid materials under certain assumptions.
• Multiple Conditioning Procedures: The standard details several procedures (B–E, Y, Z) to address non-ambient conditioning, drying, sequential exposure, and quantification of moisture loss during post-conditioning handling or testing.

Applications

ASTM D5229/D5229M-20 has broad relevance across industries that use polymer matrix composites, including aerospace, automotive, marine, and civil engineering. Practical uses include:

• Material Selection and Design: Engineers use the test data to compare candidate materials' resistance to environmental moisture, guiding selection based on expected in-service conditions.
• Pre-conditioning for Mechanical Testing: Conditioning to established moisture equilibrium states ensures that subsequent mechanical property tests (such as strength or fatigue) provide robust, comparable results.
• Predictive Modelling: The material property data generated feeds into moisture prediction analysis software, supporting life-cycle, durability, and maintenance planning for composite structures.
• Quality Assurance: Manufacturers employ these procedures as part of quality control to verify that composites conform to moisture absorption specifications.
• Failure Analysis: Quantifying moisture uptake and its impact on physical properties helps attribute material failures to environmental causes.

Related Standards

For comprehensive moisture characterization and proper specimen preparation, ASTM D5229/D5229M-20 is often used in conjunction with:

• ASTM D570: Standard Test Method for Water Absorption of Plastics
• ASTM D618: Practice for Conditioning Plastics for Testing
• ASTM D3878: Terminology for Composite Materials
• ASTM D2344/D2344M: Test Method for Short-Beam Strength of Polymer Matrix Composites

Adhering to these linked standards ensures consistency in terminology, conditioning, and test methodology, which is critical for verifiable and comparable results in research, product development, and compliance documentation.

---

Keywords: ASTM D5229, moisture absorption in composites, polymer matrix composites, equilibrium conditioning, moisture diffusivity, composite material testing, material conditioning, environmental effects on composites, ASTM standards for composites, gravimetric moisture testing.

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: D5229/D5229M − 20
Standard Test Method for
Moisture Absorption Properties and Equilibrium
Conditioning of Polymer Matrix Composite Materials
This standard is issued under the fixed designation D5229/D5229M; 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.
INTRODUCTION
Consistent evaluation and comparison of the response of polymer matrix composites to moisture
absorption can only be performed when the material has been brought to a uniform through-the-
thickness moisture profile. The procedures described in Test Method D570 and Practice D618 do not
guarantee moisture equilibrium of the material. A similar, but more rigorous, procedure for
conditioning to equilibrium is described by this test method, which can also be used with fluid
moisture other than water, and which, additionally, can provide the moisture absorption properties
necessary for the analysis of single-phase Fickian moisture diffusion within such materials.
1. Scope single-phase Fickian diffusion model. A reinforced polymer
matrix composite material tested below its glass-transition
1.1 This test method covers a procedure for the determina-
temperature typically meets this requirement, although two-
tion of moisture absorption or desorption properties in the
phase matrices such as toughened epoxies may require a
through-the-thickness direction for single-phase Fickian solid
multi-phase moisture absorption model. While the test proce-
materials in flat or curved panel form. Also covered are
dures themselves may be used for multi-phase materials, the
procedures for conditioning test coupons prior to use in other
calculationsusedtodeterminethemoisturediffusivityconstant
test methods; either to an essentially moisture-free state, to
in Procedure A are applicable only to single-phase materials.
equilibrium in a standard laboratory atmosphere environment,
Other examples of materials and test conditions that may not
or to equilibrium in a non-laboratory environment. Also
meet the requirements are discussed in Section 6.
included are procedures for determining the moisture loss
during elevated temperature testing, as well as moisture loss 1.3 The evaluation by ProcedureAof the moisture equilib-
resulting from thermal exposure after removal from the con- rium content material property does not assume, and is
ditioning environment, such as during strain gauge bonding. therefore not limited to, single-phase Fickian diffusion behav-
While intended primarily for laminated polymer matrix com- ior.
posite materials, these procedures are also applicable to other
1.4 The procedures used by this test method may be
materials that satisfy the assumptions of 1.2.
performed, and the resulting data reduced, by suitable auto-
1.2 The calculation of the through-the-thickness moisture matic equipment.
diffusivity constant in Procedure A assumes a single-phase
1.5 Thistestmethodisconsistentwiththerecommendations
Fickian material with constant moisture absorption properties
of CMH-17 Rev G (1), which describes the desirable attri-
through the thickness of the specimen. The validity of the
butes of a conditioning and moisture property determination
equations used in Procedure A for evaluating the moisture
procedure.
diffusivity constant in a material of previously unknown
1.6 The values stated in either SI units or inch-pound units
moisture absorption behavior is uncertain prior to the test, as
are to be regarded separately as standard. The values stated in
thetestresultsthemselvesdetermineifthematerialfollowsthe
each system are not necessarily exact equivalents; therefore, to
ensure conformance with the standard, each system shall be
used independently of the other, and values from the two
This test method is under the jurisdiction of ASTM Committee D30 on
systems shall not be combined.
Composite Materials and is the direct responsibility of Subcommittee D30.04 on
Lamina and Laminate Test Methods.
Current edition approved March 1, 2020. Published April 2020. Originally
approved in 1992. Last previous edition approved in 2014 as D5229/ Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
ε1
D5229M–14 . DOI: 10.1520/D5229_D5229M-20. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5229/D5229M − 20
1.6.1 Within the text, the inch-pound units are shown in to analytical dimensions when used within square brackets, as
brackets. the symbols may have other definitions when used without the
brackets.
1.7 This standard does not purport to address all of the
3.2.2 accuracy criterion, n—the maximum amount of
safety concerns, if any, associated with its use. It is the
change in average moisture content for a test coupon, over the
responsibility of the user of this standard to establish appro-
span of the reference time period, which is allowable for the
priate safety, health, and environmental practices and deter-
establishment of effective moisture equilibrium. (See also
mine the applicability of regulatory limitations prior to use.
average moisture content, moisture equilibrium, and reference
1.8 This international standard was developed in accor-
time period.)
dance with internationally recognized principles on standard-
3.2.3 average moisture content, M (%), n—the average
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom- amountofabsorbedmoistureinamaterial,takenastheratioof
the mass of the moisture in the material to the mass of the
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee. oven-dry material and expressed as a percentage, as follows:
2. Referenced Documents
W 2 W
i o
3 M,% 5 3100 (1)
2.1 ASTM Standards: W
o
D570Test Method for Water Absorption of Plastics
where:
D618Practice for Conditioning Plastics for Testing
W = current specimen mass, g, and
i
D792Test Methods for Density and Specific Gravity (Rela-
W = oven-dry specimen mass, g.
o
tive Density) of Plastics by Displacement
(See also oven-dry.)
D883Terminology Relating to Plastics
D2344/D2344MTest Method for Short-Beam Strength of
3.2.4 Fickian diffusion, n—a model of material moisture
PolymerMatrixCompositeMaterialsandTheirLaminates
absorption and desorption that follows Fick’s second law, as
D2584Test Method for Ignition Loss of Cured Reinforced
follows in one-dimension:
Resins
D2734TestMethodsforVoidContentofReinforcedPlastics
]c ] c
D3171Test Methods for Constituent Content of Composite 5 D
z 2
]t ]z
Materials
3.2.5 glass transition temperature, T [Θ],n—the approxi-
g
D3878Terminology for Composite Materials
matemidpointofthetemperaturerangeoverwhichareversible
E691Practice for Conducting an Interlaboratory Study to
changetakesplacebetweenaviscousorrubberyconditionand
Determine the Precision of a Test Method
ahard,relativelybrittlecondition,inanamorphouspolymer,or
2.2 Military Standard:
in amorphous regions of a partially crystalline polymer.
MIL-B-131Barrier Materials, Water Vapor-Proof, Grease-
3.2.5.1 Discussion—The glass transition temperature of
Proof, Flexible, Heat-Sealable
manypolymermatrixcompositesisloweredbythepresenceof
absorbed moisture.
3. Terminology
3.2.6 moisture, n—liquid (water, jet fuel, salt water, or any
3.1 Definitions:
other liquid) that is either diffused in relatively small quantity
3.1.1 Terminology D3878 defines terms relating to high-
anddispersedthroughagasasavapor,condensedonasurface
modulus fibers and their composites. Terminology D883 de-
as visible dew, or present in quantity sufficient for immersion
fines terms relating to plastics. In the event of a conflict
of an object.
between terms, Terminology D3878 shall have precedence
3.2.6.1 Discussion—The dictionary definition of moisture
over the other terminology standards.
for this test method is extended to include not only the vapor
3.2 Definitions of Terms Specific to This Standard:
of a liquid and its condensate, but the liquid itself in large
3.2.1 Ifthetermrepresentsaphysicalquantity,itsanalytical
quantities, as for immersion.
dimensionsarestatedimmediatelyfollowingtheterm(orletter
−3
3.2.7 moisture concentration, c [ML ], n—the absolute
symbol) in fundamental dimension form, using the following
amount of absorbed moisture in a material expressed as the
ASTM standard symbology for fundamental dimensions,
mass of moisture per unit volume.
shownwithinsquarebrackets:[M]formass,[L]forlength,[T]
2 −1
3.2.8 moisture diffusivity constant, D [L T ], n—the prop-
for time, [Θ] for thermodynamic temperature, and [nd] for z
erty of a material that describes the rate at which the material
non-dimensional quantities. Use of these symbols is restricted
absorbs or desorbs moisture.
3.2.8.1 Discussion—In Fickian materials, this property is
3 relativelyindependentofthemoistureexposurelevel(andthus
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
the moisture equilibrium content material property). However,
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 moisture diffusivity constant is strongly influenced by
the ASTM website.
temperature. Moisture diffusivity can be anisotropic; the sub-
Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,
script z indicates the value in the through-the-thickness direc-
Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http://
dodssp.daps.dla.mil. tion for anisotropic diffusion behavior.
D5229/D5229M − 20
3.2.9 moisture equilibrium, n—the condition reached by a to be a standard laboratory environment) in accordance with
material when there is essentially no further change in its Procedure C of this test method.
average moisture content with the surrounding environment.
3.2.17 standard laboratory atmosphere, n—an atmosphere
3.2.9.1 Discussion—Moisture equilibrium can be either ab-
(environment) having a temperature of 23 62°C
solute or effective. Absolute moisture equilibrium requires no
[73.4 63.6°F] and a relative humidity of 50 610%.
measurable change in moisture content, while effective mois-
3.2.18 test temperature, n—the environmental temperature
tureequilibriumallowsaspecifiedsmallchangeintheaverage
used in Procedures A-E, Y, and Z.
moisture content of a material (the accuracy criterion) over a
3.2.18.1 Discussion—Thisisdistinguished,forthepurposes
specified time span (the reference time period). (See also
of this test method, from the environmental temperature used
accuracy criterion, average moisture content, and reference
during any subsequent material evaluation testing.
time period.) Effective moisture equilibrium is a satisfactory
3.2.19 traveler coupon, n—a surrogate coupon of the same
definition for most engineering applications. Unless otherwise
material and thickness, and of appropriate size (but without
specified, references to moisture equilibrium in this test
tabs) that is used in a conditioning procedure to determine
method mean effective moisture equilibrium, as quantified in
moisturecontentforspecimenconfigurations(suchasatabbed
10.2.Moistureequilibriumcanalsobeeitherstatic,whenthere
mechanical coupon, or a coupon that does not meet the
is no moisture transport at all across the surfaces, or dynamic,
minimummassrequirement)thatcannototherwisebeproperly
whenmoisturetransportexists,butthenetsumforthematerial
measured by this test method.
is zero. This test method is not capable of discerning between
these two types of moisture equilibrium.
3.3 Symbols:
3.3.1 c—moisture concentration.
3.2.10 moisture equilibrium content, M (%), n—the maxi-
m
mum amount of absorbed moisture that a material can contain
3.3.2 D —moisture diffusivity constant in the through-the-
z
at moisture equilibrium for a given moisture exposure level,
thickness direction.
expressedasapercentofdrymaterialmass.(Seealsomoisture
3.3.3 G(T,t)—moistureabsorptionordesorptionfunctionfor
saturation content.)
materials that follow Fickian diffusion.
3.2.10.1 Discussion—In polymer matrix composites, this
3.3.4 h—thickness of a material panel or plate in the
property is relatively independent of temperature (and thus the
through-the-thickness direction for double-sided moisture ex-
moisture diffusivity constant material property), but it is a
posure.
function of the moisture exposure level. For the purposes of
thistestmethod,M isassumedtobeequivalenttotheaverage 3.3.5 M—average moisture content of a material. The fol-
m
moisture content at effective moisture equilibrium, M. lowing subscripts denote the average moisture content for
f
specific conditions:
3.2.11 moisture exposure level, n—a measure or description
M , the average moisture content at a baseline time;
b
of the severity of a conditioning environment in terms of the
M , the average moisture content at establishment of effec-
e
amount of liquid or vapor present. (See also moisture and
tive moisture equilibrium;
relative vapor level.)
M , the average moisture content at establishment of
ed
3.2.12 moisture saturationcontent,n—themoistureequilib-
effective moisture equilibrium as a delta from the average
riumcontentatthemaximumpossiblemoistureexposurelevel,
moisture content at a baseline time;
wherein the material contains the greatest possible amount of
M , the average moisture content at establishment of effec-
et
absorbed moisture. (See also moisture equilibrium content.)
tivemoistureequilibriumasatotalvaluefromtheconditionof
3.2.13 oven-dry,n—theconditionofamaterialthathasbeen
zero moisture content;
dried in accordance with Procedure D of this test method until
M, the final moisture content at the end of conditioning for
f
moisture equilibrium is achieved.
a fixed time;
M, the average moisture content at a given time;
3.2.14 reference time period, n—the time interval for mass
i
measurementusedtodefineeffectivemoistureequilibriumina M , the average moisture content at the previous time;
i−1
M , the moisture loss from the state of effective equilibrium
material. (See also accuracy criterion, average moisture
L
content, and moisture equilibrium.) due to subsequent heating; and
M , the moisture equilibrium content that is reached when a
3.2.14.1 Discussion—A small change in the average mois-
m
ture content (the accuracy criterion) for a material during the uniform through-the-thickness moisture profile occurs for a
given temperature and moisture exposure level.
reference time period indicates effective moisture equilibrium.
3.3.5.1 Discussion—Procedures A-H of this test method
3.2.15 relative vapor level (%), n—the ratio of the pressure
condition specimens to M . Except for the use of a thin
e
of a vapor present to the pressure of the saturated vapor, at the
specimen in Procedure A, conditioning specimens to M is
m
same temperature, expressed as a percent.
generally not practical. See also the discussion in Appendix
3.2.15.1 Discussion—Applicable only to the gaseous form
X2.
of a fluid. When the vapor is water vapor, the term is called
3.3.6 t—time.
relative humidity. (See also moisture exposure level.)
3.2.16 standard conditioned specimen, n—the material con- 3.3.7 t —themaximumtimerequiredforamaterialtoreach
m
dition of a test coupon that has reached effective moisture moistureequilibriumunderspecifiedconditionsoftemperature
equilibriumatanominalrelativehumidityof50%(considered and initial moisture content.
D5229/D5229M − 20
3.3.8 T —glass transition temperature. 4.3 In Procedure B, a general test coupon (not necessarily
g
the coupon of Procedure A) is maintained, similarly to Proce-
3.3.9 w—the width of a nominally square moisture absorp-
dureA, in a steady-state environment at specified temperature
tion test coupon.
and environmental exposure levels until the material reaches
3.3.10 W—the mass of a test coupon. The following sub-
effective moisture equilibrium.
scriptsareusedtodenotethemassofatestcouponforspecific
4.4 In Procedure C, a general test coupon is maintained in a
conditions:
steady-state environment at a specified temperature and a
W , the mass at the baseline time;
b
relative humidity of 50% until the material reaches effective
W, the mass at a given time; and
i
moisture equilibrium.
W , the mass at the previous time.
i−1
4.5 In Procedure D, a general test coupon is maintained in
3.3.11 z—the coordinate axis in the through-the-thickness
an air-circulating oven at a prescribed elevated temperature
direction for a plate or panel.
environment until effective moisture equilibrium is reached.
4. Summary of Test Method 4.6 In Procedure E, a general test coupon is conditioned in
two or more sequential non-ambient steady-state environ-
4.1 This is a gravimetric test method that monitors the
ments.
change over time to the average moisture content of a material
4.7 InProcedureY,ageneraltestcouponisfirstconditioned
specimen by measuring the total mass change of coupons that
to equilibrium using Procedure B, then is exposed to room
areexposed on twosidestoaspecifiedenvironment.Thereare
temperature ambient followed by an elevated temperature for
a number of test procedures described by this test method.
defined times, then again conditioned to equilibrium.
4.1.1 Procedure A covers the determination of the two
Fickian moisture diffusion material properties, the moisture
4.8 InProcedureZ,ageneraltestcouponisfirstconditioned
diffusivity constant and the moisture equilibrium content. The
to equilibrium using Procedure B, then is exposed to the same
other procedures cover material conditioning to a specific
testing environment (nominal ramp and soak time and an
moisture environment.
additionalholdtimetomimicthetesttime)asthespecimensit
4.1.2 Procedure B covers non-ambient moisture condition- represents.
ing of material coupons at a prescribed constant conditioning
environment prior to other types of testing. Sub-procedure
5. Significance and Use
codes are used to specify the conditioning environment,
5.1 Procedure A is designed to produce moisture diffusion
conditioning time, and mass change monitoring procedure.
material property data that may be used as follows:
4.1.3 Procedure C covers the ambient conditioning of ma-
5.1.1 To determine approximate exposure times for coupon
terial coupons to a nominal relative humidity level of 50 %,
conditioning in Procedures B-E, Y, and Z;
prior to other types of testing.
5.1.2 As input to moisture prediction analysis computer
4.1.4 Procedure D covers the conditioning (drying) of
codes; or
material coupons to an essentially moisture-free condition.
5.1.3 For making qualitative decisions on material selection
4.1.5 Procedure E covers conditioning in two or more
orperformanceunderenvironmentalexposuretovariousforms
sequential steps using Procedure Bxxx.
of moisture.
4.1.6 ProcedureYcoversthedeterminationoftheamountof
5.2 Procedures B-E are designed to condition test coupons
moisture loss in conditioned material coupons when removed
to a specified environmental condition or equilibrium state
from the conditioning environment (such as due to heating
prior to other material property testing (including, but not
during cure of strain gauges).
limited to, mechanical testing).
4.1.7 ProcedureZcoversthedeterminationoftheamountof
5.3 Procedures Y-Z are designed to determine the loss of
moisturelossinconditionedmaterialcouponsduetoheatingto
moisture content due to removal of a test coupon from the
the mechanical test temperature and holding at the test tem-
conditioningchamber(suchasforstraingaugebonding)ordue
perature for the duration of the mechanical test.
to heating of the test coupon prior to and during mechanical
4.2 In Procedure A, the percent moisture mass gain versus
loading.
time is monitored for thin material specimen(s) that are
5.4 Asingle pair of tests on thin and thick specimens using
maintained in a steady-state environment at a known tempera-
ProcedureAprovidesthemoisturediffusivityconstant,D ,and
z
ture and moisture exposure level until the material reaches
the moisture equilibrium content, M , at the given moisture
m
effective moisture equilibrium, and thick material specimen(s)
exposure level and temperature. Multiple tests at differing
that are maintained in a steady-state environment at a known
temperatures are required to establish the dependence of D on
z
temperature and moisture exposure level until the material is
temperature. Multiple tests at differing moisture exposure
conditioned past the point of linear moisture gain. From the
levels are required to establish the dependence of M on
m
data obtained from these two specimen thicknesses, the mois-
moisture exposure level.
ture equilibrium content, M , and the one-dimensional mois-
m
NOTE1—Formanypolymermatrixcomposites,themoisturediffusivity
ture absorption rate of the coupon may be determined and the
isusuallyonlyweaklyrelatedtorelativehumidityandisoftenassumedto
through-the-thickness moisture diffusivity constant, D , calcu-
z be a function only of temperature, usually following an Arrhenius-type
lated. exponential relation with inverse absolute temperature. For many of these
D5229/D5229M − 20
materials,moistureequilibriumcontentisonlyweaklyrelatedtotempera-
6.3.2 Materials with a significant amount of surface crack-
ture and is usually assumed to be a function only of relative humidity (1).
ing;
5.5 Vapor-exposure testing shall be used to condition the
6.3.3 Material systems that have been shown to behave in a
specimen when the in-service environmental condition is a
non-Fickian manner, or that have multi-phase moisture diffu-
vapor such as humid air. Immersion in a liquid bath should be
sion mechanisms as discussed by Bonniau and Bunsell (5);
used to simulate vapor exposure only when apparent absorp-
6.3.4 Material systems that are known to have a moisture
tion properties are desired for qualitative purposes. Properties
diffusivity constant that is strongly dependent upon moisture
determined in the latter manner shall be reported as apparent
concentration;
properties.
6.3.5 Material systems that are known to have a moisture
NOTE 2—For many polymer matrix composites, the moisture absorp-
diffusivity constant that is significantly time-dependent;
tion properties under atmospheric humid conditions are generally not
6.3.6 Material systems that are known to have a moisture
equivalent to exposure either to liquid immersion or to pressurized steam.
diffusivity constant that is significantly stress-dependent, and
These latter environments may have different material diffusion charac-
teristics. that are used in a laminate containing significant amounts of
residual stress;
6. Interferences
6.3.7 Material systems containing an abnormal amount of
6.1 The calculation of the through-the-thickness moisture voids (porosity), or with a non-uniform void distribution, as
discussed by Harper et al. (6). Moisture (in liquid or gaseous
diffusivity constant in Procedure A assumes a single-phase
Fickian material that possesses constant moisture diffusivity form) can fill the voids, resulting in an incorrect measurement
properties through the thickness of the specimen. The validity of the amount of moisture absorbed into the material, and can
of ProcedureAfor evaluating the moisture diffusivity constant result in removal of specimens from the conditioning environ-
in a material of previously unknown moisture absorption
ment at a premature time;
behavior will be uncertain prior to the test, as the test results
6.3.8 Test apparatus that produces a significant temperature
themselves determine whether the material follows the single-
gradient in the specimen, either through-the-thickness or in-
phase Fickian diffusion model. As discussed by Shirrell (2),
plane,asthematerialmoisturediffusionconstantisgenerallya
previous investigators have shown that for diffusion to be
strong function of temperature;
rigorously classified as Fickian, it must satisfy the following
6.3.9 Testing above the glass transition temperature of any
three conditions:
constituentorphase-componentwithinthecompositematerial,
6.1.1 Both absorption and desorption curves must be essen-
which generally results in non-Fickian or multiphase moisture
tially linear up to 60% of M ;
m
diffusion behavior, or both;
6.1.2 Beyond the initially linear portion, both absorption
6.3.10 Materials that lose mass during moisture condition-
and desorption curves must be concave to the abscissa axis
ing (for example, materials that have water or fluid soluble
until M is reached; and
m
components); or
6.1.3 For the same environmental exposures, absorption
6.3.11 Materials that advance their cure state during expo-
curves resulting from different specimen thicknesses of the
sure to water or water vapor (for example, some phenolic
same material must be essentially super-imposable if each
resins).
curve is plotted in the form of a normalized sorption curve in
~= ! =
which the abscissa is time ⁄h, instead of time.
6.4 For materials with a very high moisture diffusion rate, a
low moisture equilibrium content, or both, the time scales
6.2 These conditions are rigorous, and may not be fully met
requiredforperiodicweighingsmaybeveryshort(ontheorder
by many engineering materials. In fact, these conditions may
of minutes or hours), and extreme care must be taken with the
be difficult to experimentally verify for certain materials, and
mass measurements and with the calibration and control of the
forthisreason,thedecisiononhowrigorouslytheseconditions
environmental chamber, in order to avoid large measurement
must be met for a given test material is left to the user. For
errors. The most convenient solution for reducing the test
example, a severe complete absorption/desorption cycle may
sensitivityofthesematerialsistosimplyincreasethethickness
cause damage to a given material, causing cracking and
of the test specimen.
providing a non-Fickian diffusion path, making evaluation of
these conditions impossible.
6.5 Thedefinitionofeffectiveequilibriumallowsforasmall
6.3 However, there are a number of material forms or test continual increase in moisture absorption at test termination.
conditions that are known to have the potential to violate one Consequently,themoisturecontentoftheconditionedcoupons
or more of the assumptions used by this test method, or to may not be truly representative of the effects of long term
potentiallycausenon-Fickianmaterialbehavior.Manyofthese exposure. Examples of materials that may exhibit significant
issuesarediscussedbyseveralofthepapersinASTMSTP658 continual moisture uptake after effective equilibrium include
(3) or in the paper by Blikstad et al. (4). They include: those with excessive porosity, concentrated resin pockets, and
6.3.1 Materials with fibers that are distributed in three wrinkled fibers. If prolonged exposure is a concern, condition-
dimensions, and that affect the moisture diffusion mechanism ing to a real world exposure lifetime is recommended, or at
bymeanssuchaswickingalongthefiber/matrixinterface,such least moisture uptake should be interrogated in a timeframe
as: materials stitched through-the-thickness, or some injection- significantly after reaching effective equilibrium, as defined in
molded materials; this standard.
D5229/D5229M − 20
7. Apparatus For typical specimen geometries, an instrument with an accu-
racy of 60.0025mm [60.0001in.] is adequate for the thick-
7.1 Balance—An analytical balance is required that shall be
ness measurement, while an instrument with an accuracy of
capable of the appropriate accuracy shown in Table 1.
60.025mm [60.001in.] is adequate for the width and length
NOTE 3—These accuracy requirements are derived from the definition
measurements.
of effective moisture equilibrium (Eq 6) and the specimen mass of 8.2.2,
as discussed in X2.10. 7.5 Desiccator—Aclean,drydesiccatorinwhichspecimens
being oven-dried shall be brought to laboratory temperature
7.2 Oven or Vacuum Drying Chamber—An air-circulating
following removal of the specimens from the oven.
oven is required that shall be capable of maintaining the
required temperatures to within 63°C [65°F]. A vacuum
7.6 Specimen Bag—Asealable, flexible, moisture-proof bag
drying chamber or a vacuum oven may also be used.
(or other suitable sealable container) made of material suitable
for exposure to specimens that have been removed from the
7.3 Conditioning Chamber—A conditioning chamber is re-
conditioning chamber for cooling prior to weighing. Bags that
quired that shall be capable of maintaining the required
meet the requirements of MIL-B-131 have been found satis-
temperature to within 63°C [65°F]. The chamber shall be
monitored either on an automated continuous basis or on a factory for use in standard applications.
manual basis at regular intervals. The chamber shall consist of
7.7 AbsorbentCloth—Clean,non-lintingabsorbentclothfor
either of the following:
use in wiping exuded or condensed moisture from test speci-
7.3.1 For Absorption by Vapor Exposure—A temperature
mens.
and vapor-level controlled vapor exposure chamber that is
7.8 Gloves—Clean, non-linting gloves for use when han-
capable of maintaining the required relative vapor level to
dling specimens.
within 63%,or
7.3.2 ForAbsorption by Liquid Immersion—Atemperature-
controlled liquid bath. 8. Test Specimen
NOTE 4—While many newer models have solid-state controls, a great 8.1 Sampling of Test Specimens:
many environmental chambers control the chamber humidity via moni-
8.1.1 Procedure A—Test a minimum of one "thin" coupon
toring of “dry-bulb” (actual) and “wet-bulb” (moisture depressed)
and one "thick" coupon. Testing of three (3) replicates of each
temperatures, which are converted to equivalent relative humidity via a
coupon thickness is recommended when sufficient material is
table or algorithm supplied by the manufacturer. The ability of these
chambers to control relative humidity is dependent on the accuracy of the available.
thermometer readings. Particularly important in these chambers is regular
8.1.2 Procedures B-E—When a group of test specimens of
cleaning of the water reservoir, replacement of the wick, and maintenance
the same material and thickness for subsequent material
of a proper contact between the wick and the wet-bulb thermometer.
evaluation are to be conditioned at the same time, and periodic
Chambers that control the dry-bulb temperature and the differential
betweenthedry-bulbandwet-bulbtemperaturesgenerallyhaveimproved weighing of the specimens is required by the procedure, a
control of chamber relative humidity over those that control the dry-bulb
minimumofthree(3)specimensorthreetravelercouponsfrom
and wet-bulb temperatures.
the group shall be weighed. See 8.2.5 for a discussion of when
NOTE 5—Since loss of the water supply to a humidity chamber results
travelercouponsshouldbeused.Ifthegroupoftestspecimens
intheconditioningenvironmentchangingtoadryingconditionwithoften
are not "dried" prior to moisture conditioning, the initial
a significant delay to the desired moisture conditioning, the use of a real
time power and water supply monitoring and alarm system for the
moisturecontent,M ,ofthematerialpriortoconditioningmay
b
chamber is recommended. The alarm system should be able to contact
be determined by either (a) drying the traveler coupons using
off-site lab personnel in the event of an anomaly.Afurther recommenda-
Procedure D after moisture conditioning has been completed,
tion is to use a system to shut off the chamber heat when a water supply
(b) drying using Procedure D an additional three traveler
or humidity fault is detected.
coupons,or(c)ifthematerialdiffusivityconstantandeffective
7.4 Micrometers and Calipers—A micrometer witha4to
moisture equilibrium content are known, by using the proce-
7mm[0.16to0.28in.]nominaldiameterballinterfaceshallbe
dures in Appendix X3.
used to measure the specimen thickness when at least one
surface is irregular (such as the bag-side of a laminate). A
NOTE6—Insomecases,the "dry"weightpriortomoistureconditioning
to equilibrium may not be equal to the "dry" weight when subsequently
micrometer witha4to7mm [0.16 to 0.28in.] nominal
driedaftermoistureconditioning(seeSection6),inwhichcase(a)and(b)
diameter ball interface or with a flat anvil interface shall be
above may not be equivalent. If this situation is suspected and determi-
usedtomeasurethespecimenthicknesswhenbothsurfacesare
nation of an accurate initial moisture content is required, then tests using
smooth(suchastooledsurfaces).Amicrometerorcaliper,with
both approaches are recommended.
a flat anvil interface, shall be used to measure the width and
8.1.3 Procedure Y—In cases where specimens are required
length of the specimen. The accuracy of the instruments shall
to be removed from the conditioning environment prior to
be suitable for reading to within 1% of the sample dimensions.
testing (such as the case where elevated temperature testing
requires the use of high temperature cures (190°C [375°F])
for the strain gauge adhesive and the strain gauges are bonded
TABLE 1 Balance Accuracy
after moisture conditioning), the loss of moisture during the
Specimen Mass, g Balance Accuracy Requirement, mg
time out of the conditioning environment should be quantified
$5 but <50 0.1
by a minimum of three (3) "moisture loss" specimens that
$50 1.0
represent each material and laminate thickness. Mechanical
D5229/D5229M − 20
Aminimum laminate thickness of 10 times the nominal fiber diameter is
testspecimensshouldbere-conditionedforthere-conditioning
recommended.
time duration determined by the "moisture loss" specimens.
8.1.4 Procedure Z—The moisture loss during testing at
8.2.4 Specimen Size and Shape For Use With Procedure A:
elevated temperatures should be quantified by a minimum of
8.2.4.1 Thin Specimen—Since the purpose of the "thin" test
three (3) “moisture loss” specimens that represent each:
specimen is only for moisture equilibrium content
material, laminate thickness, hot/wet specimen geometry
determination, there is no size requirement other than the
(width and length), and test temperature. Separate moisture
minimum mass in accordance with 8.2.2.
loss specimens shall be used for fixtured and non-fixtured
8.2.4.2 Thick Specimen—As edge effects must be mini-
specimens with the same dimensions. Moisture loss specimens
mized in materials with anisotropic moisture diffusivity con-
are not required to be tabbed or notched, even if the specimens
stants in order to accurately determine the through-thickness
they represent are tabbed or notched. When simulating tabbed
diffusion constant, the "thick" test specimen shall consist of
specimens, the moisture loss specimens may be gripped using
either 8.2.4.2(1) or 8.2.4.2(2) below. The "thick" test speci-
un-bonded, simulated tabs to prevent specimen damage and
men for moisture diffusivity constant determination shall be
mimic heat transfer through tabs into grips.
thick enough such that achieving a moisture content of
8.2 Test Specimen Geometry:
approximately70%ofthemoistureequilibriumcontentforthe
8.2.1 Summary—The following requirements are summa-
same exposure conditions shall require a minimum of 35 days
rized in Table 2 for ease of reference.
of exposure (if less time is required, then a repeat of the test
8.2.2 Specimen Mass Requirement—Specimens (including
with a thicker specimen is recommended).
travelers) shall have a mass of at least 5.0 g (see X2.10).
(1) Anominally square plate or curved panel with dimen-
Specimen mass affects the balance accuracy requirement es-
sions that satisfy the relation:
tablished in 7.1.
8.2.3 Specimen Thickness—The specimen thickness shall
w
not vary by more than 65% over the surface of the specimen $ 100 (2)
h
and shall comply with 8.2.2 and Eq 2, as applicable.
where:
NOTE 7—No minimum specimen thickness is required. However, the
w = nominal length of one side, mm [in.], and
specimen thickness has a profound effect on the total time required to
h = nominal thickness, mm [in.].
reach equilibrium, as well as on the reference time period of 10.1.7.1.
Also, when designing a coupon, consideration should be given to the
(2) A 100 6 10mm [4.0 6 0.5in.] square plate with
macrostructure of the composite material in the through-the-thickness
stainless steel foil bonded to the edges such that moisture
direction. If the moisture absorption coupon is substantially thinner than
absorption through the edges is essentially eliminated. When
the material in the end-use form, there should be sufficient number of
this specimen is prepared, care shall be taken to weigh the
fibers through the thickness that the absorption properties of the material
coupon can be considered equivalent to the absorption properties of the coupon both before and after bonding of the foil in order to
same material in a much thicker form, under the same environmental
obtain the mass increase due to the foil and the adhesive. The
conditions. A thin (even one-ply) laminate, if reinforced by a significant
adhesive used shall be incapable of absorbing sufficient mois-
number of fibers that are small in diameter relative to the thickness, could
ture to affect the results.
be acceptable if it met the other specimen geometry requirements of 8.2.
However, a substantially thicker multi-ply laminate, reinforced by fibers NOTE 8—A typical "thin" specimen for the carbon/epoxy material
havingadiameterontheorderoftheplythickness,maynotbeacceptable. describedinX2.2havingdimensionsof1mm[0.040in.]thickby100mm
TABLE 2 Summary of Specimen Geometry Requirements
Property Testing Procedure A–Thick Specimen Conditioning Procedures B-Z
Known Reference Time Period: Known Specimen Thickness:
(1) Determine the reference time period from 10.1.7.1.Ifthisis
(1) Determine the maximum thickness from h5 D t/0.04.Ifa
œ z
unacceptable, then the specimen thickness must be changed.
thicker specimen is required, then the reference time period must be
(2) Estimate the specimen mass from the material density, known
changed. This equation is valid for the 0.02 % moisture change criteria in
thickness, and the configuration. Specimen mass shall be $5g.Ifthe esti-
10.2; if a different value for effective equilibrium moisture change is used,
mated mass is too small, or the specimen has attached tabs or other features
see 10.1.8 and Appendix X2.
that violate the assumptions of this test method, then a traveler coupon must be
(2) Determine the plate size from either Eq 2 (non-sealed edges) or
used.
8.2.4.2 (2) (sealed edges).
(3) Estimate the specimen mass from Mass = w × h × density. The
specimen mass shall be $5 g. If the estimated mass is too small, then
the plate size must be increased (or the specimen made thicker and the
reference time period correspondingly increased).
Known Specimen Thickness:
(1) Determine the reference time period from 10.1.7.1. If the value so
determined is unacceptable, then the specimen thickness must be
changed.
(2) Determine the plate size from either Eq 2 (non-sealed edges) or
8.2.4.2 (2) (sealed edges).
(3) Estimate the specimen mass from Mass = w × h × density. The
specimen mass shall be $5 g. If the estimated mass is too small, then
the plate size must be increased (or the specimen made thicker and the
reference time period correspondingly increased).
D5229/D5229M − 20
[4 in.] square would have a mass of approximately 18 g. If conditioned at
10.1.1 The procedure to be used (A-Z), the sub-procedure
74°C [170°F] and 90 % relative humidity, use of Eq X1.7 (using an
codes Bxxx when using Procedure B (listed in Table 3), the
accuracycriteriaof0.02%andamaximumdifferencebetweenM andM
m f
sequential Procedure B sub-procedure codes when using Pro-
of 0.02 %) predicts that this specimen would reach equilibrium in
cedure E, and whether the specimens shall be dried using
approximately 57 days. The minimum reference time period used to test
Procedure D prior to moisture conditioning. Procedure B
equilibrium is established by 10.1.7.1 as the greater of 0.04 h /D (equal
z
to44h)or24h;roundingtoapracticaleventimegivesareferenceperiod
sub-procedure codes for some common conditioning methods
of 2 days. A typical "thick" specimen for the carbon/epoxy material
are listed in Table 4. If Procedure B is specified without a
described in X2.2 may have dimensions of 3.0 mm [0.120 in.] thick by
sub-procedure code, then conditioning shall be performed per
100 mm [4 in.] square with sealed edges, satisfying 8.2.4.2 (2).If
code BHEE.
conditioned at 74°C [170°F] and 90 % relative humidity, use of Eq X1.7
(using the same criteria) predicts that this specimen would reach 70% of
NOTE 10—If a drying step is included, whether as an initial step prior
the effective moisture equilibrium in approximately 38 days.
to moisture conditioning, or as part of an oven-dry experiment, care
8.2.5 Specimen Size and Shape For Use With Procedures should be taken to avoid excessively high drying temperatures and high
thermal excursions that may induce thermal cracking, oxidation, or mass
B-Z—The specimen size and shape requirement for Procedure
loss, or combinations of the three in the material.
A(8.2.4) is not a requirement for the conditioning procedures
10.1.2 The density and fiber volume sampling method
(B-Z) of this test method. The coupon size and shape used in
(required only for Procedure A), coupon geometry, and test
Procedures B-Z is normally that required for subsequent
method (see Note 11 for guidance).
material evaluation following conditioning, as long as the
couponmeetsthemassandthicknessrequirementsof8.2.2and
NOTE 11—For many polymer matrix composites, the volume percent
8.2.3. When the coupon is of such type or geometry that the
reinforcement can be determined by one of the matrix digestion proce-
duresofTestMethodsD3171,or,forcertainreinforcementmaterialssuch
moisture change in the material cannot be properly measured
as glass and ceramics, by the matrix burn-off technique of Test Method
by weighing the specimen itself, traveler coupon(s) of the
D2584. Test Methods D2734 describe the limitations and use of the
same material and thickness, and of appropriate size (but
calculations required to approximate the void content in the composite.
without tabs, if present) shall be used to determine moisture
The void content equations ofTest Methods D2734 are applicable to both
equilibrium for the specimens being conditioned. Material
Test Methods D2584 and D3171. Test Methods D792 can be used to
determine specific gravity.
evaluation tests that require traveler moisture conditioning
couponsincludemechanicaltestsusingtabbedcoupons,speci-
10.1.3 Themoistureabsorptionspecimensamplingmethod,
mens containing fasteners, specimens with strain gauges, and
type, and geometry (and travelers, if required), from 8.1.
test methods using coupons that do not meet the minimum
10.1.4 The balance measurement accuracy, 1.0 mg or
mass requirement for this test method, such as commonly used
0.1mg, from 7.1.
in thermo-mechanical analysis methods.
10.1.5 Conditioning chamber test temperature (for both the
8.2.6 Preparation—In specimens cut from plates, precau-
initial drying step, if required, and for the moisture condition-
tions shall be taken to avoid notches, undercuts, rough or
ing step(s)).
uneven surfaces, or delaminations due to inappropriate ma-
NOTE 12—Maximum test temperatures are recommended for all Pro-
chining methods. Final dimensions should be obtained by
ceduresinTable5.Keepthetesttemperatureforanymaterialnotlistedin
water lubricated precision milling or grinding, or both, or the
the table at least 25°C [45°F] below the wet T of the material.
g
use of a wet diamond saw. The procedure used shall be
10.1.6 Moisture type (water vapor, liquid water, specified
reported.
fluid,orspecifiedgas)andmoistureexposurelevel(intermsof
8.2.7 Labeling—Label the specimen coupons so as to be
relativehumidityforwatervaporexposure).Forgasexposures,
distinct from each other in a manner that will both be
the gas components, concentrations, and the pressure l
...

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.
´1
Designation: D5229/D5229M − 14 D5229/D5229M − 20
Standard Test Method for
Moisture Absorption Properties and Equilibrium
Conditioning of Polymer Matrix Composite Materials
This standard is issued under the fixed designation D5229/D5229M; 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.
ε NOTE—The appearance of some of the section references was updated and other editorial changes were made through-
out in February 2019.
INTRODUCTION
Consistent evaluation and comparison of the response of polymer matrix composites to moisture
absorption can only be performed when the material has been brought to a uniform through-the-
thickness moisture profile. The procedures described in Test Method D570 and PracticesPractice D618
do not guarantee moisture equilibrium of the material. A similar, but more rigorous, procedure for
conditioning to equilibrium is described by this test method, which can also be used with fluid
moisture other than water, and which, additionally, can provide the moisture absorption properties
necessary for the analysis of single-phase Fickian moisture diffusion within such materials.
1. Scope
1.1 This test method covers a procedure for the determination of moisture absorption or desorption properties in the
through-the-thickness direction for single-phase Fickian solid materials in flat or curved panel form. Also covered are procedures
for conditioning test coupons prior to use in other test methods; either to an essentially moisture-free state, to equilibrium in a
standard laboratory atmosphere environment, or to equilibrium in a non-laboratory environment. Also included are procedures for
determining the moisture loss during elevated temperature testing, as well as moisture loss resulting from thermal exposure after
removal from the conditioning environment, such as during strain gauge bonding. While intended primarily for laminated polymer
matrix composite materials, these procedures are also applicable to other materials that satisfy the assumptions of 1.2.
1.2 The calculation of the through-the-thickness moisture diffusivity constant in Procedure A assumes a single-phase Fickian
material with constant moisture absorption properties through the thickness of the specimen. The validity of the equations used
in Procedure A for evaluating the moisture diffusivity constant in a material of previously unknown moisture absorption behavior
is uncertain prior to the test, as the test results themselves determine if the material follows the single-phase Fickian diffusion
model. A reinforced polymer matrix composite material tested below its glass-transition temperature typically meets this
requirement, although two-phase matrices such as toughened epoxies may require a multi-phase moisture absorption model. While
the test procedures themselves may be used for multi-phase materials, the calculations used to determine the moisture diffusivity
constant in Procedure A are applicable only to single-phase materials. Other examples of materials and test conditions that may
not meet the requirements are discussed in Section 6.
1.3 The evaluation by Procedure A of the moisture equilibrium content material property does not assume, and is therefore not
limited to, single-phase Fickian diffusion behavior.
1.4 The procedures used by this test method may be performed, and the resulting data reduced, by suitable automatic equipment.
1.5 This test method is consistent with the recommendations of CMH-17 Rev G (1), which describes the desirable attributes
of a conditioning and moisture property determination procedure.
This test method 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.
Current edition approved May 15, 2014March 1, 2020. Published May 2014April 2020. Originally approved in 1992. Last previous edition approved in 20122014 as
ε1
D5229/D5229M – 12.D5229/D5229M – 14 . DOI: 10.1520/D5229_D5229M-14E01.10.1520/D5229_D5229M-20.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5229/D5229M − 20
1.6 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used
independently of the other, and values from the two systems shall not be combined.
1.6.1 Within the text, the inch-pound units are shown in brackets.
1.7 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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.8 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:
D570 Test Method for Water Absorption of Plastics
D618 Practice for Conditioning Plastics for Testing
D792 Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement
D883 Terminology Relating to Plastics
D2344/D2344M Test Method for Short-Beam Strength of Polymer Matrix Composite Materials and Their Laminates
D2584 Test Method for Ignition Loss of Cured Reinforced Resins
D2734 Test Methods for Void Content of Reinforced Plastics
D3171 Test Methods for Constituent Content of Composite Materials
D3878 Terminology for Composite Materials
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
2.2 Military Standard:
MIL-B-131 Barrier Materials, Watervaporproof, Greaseproof, Water Vapor-Proof, Grease-Proof, Flexible, Heat-Sealable
3. Terminology
3.1 Definitions:
3.1.1 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 the other terminology
standards.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 If the term represents a physical quantity, its analytical dimensions are stated immediately following the term (or letter
symbol) in fundamental dimension form, using the following ASTM standard symbology for fundamental dimensions, shown
within square brackets: [M] for mass, [L] for length, [T] for time, [Θ] for thermodynamic temperature, and [nd] for
non-dimensional quantities. Use of these symbols is restricted to analytical dimensions when used within square brackets, as the
symbols may have other definitions when used without the brackets.
3.2.2 accuracy criterion, n—the maximum amount of change in average moisture content for a test coupon, over the span of
the reference time period, which is allowable for the establishment of effective moisture equilibrium. (See also average moisture
content, moisture equilibrium, and reference time period.)
3.2.3 average moisture content, M (%), n—the average amount of absorbed moisture in a material, taken as the ratio of the mass
of the moisture in the material to the mass of the oven-dry material and expressed as a percentage, as follows:
W 2 W
i o
M,%5 3100 (1)
W
o
where:
W = current specimen mass, g, and
i
W = oven-dry specimen mass, g.
o
(See also oven-dry.)
3.2.4 Fickian diffusion, n—a model of material moisture absorption and desorption that follows Fick’s second law, as follows
in one-dimension:
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.
Available from Standardization Documents Order Desk, DODSSP, Bldg. 4, Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http://dodssp.daps.dla.mil.
D5229/D5229M − 20
]c ] c
5 D
z 2
]t ]z
3.2.5 glass transition temperature, T [Θ],n—the approximate midpoint of the temperature range over which a reversible change
g
takes place between a viscous or rubbery condition and a hard, relatively brittle condition, in an amorphous polymer, or in
amorphous regions of a partially crystalline polymer.
3.2.5.1 Discussion—
The glass transition temperature of many polymer matrix composites is lowered by the presence of absorbed moisture.
3.2.6 moisture, n—liquid (water, jet fuel, salt water, or any other liquid) that is either diffused in relatively small quantity and
dispersed through a gas as a vapor, condensed on a surface as visible dew, or present in quantity sufficient for immersion of an
object.
3.2.6.1 Discussion—
The dictionary definition of moisture for this test method is extended to include not only the vapor of a liquid and its condensate,
but the liquid itself in large quantities, as for immersion.
−3
3.2.7 moisture concentration, c [ML ], n—the absolute amount of absorbed moisture in a material expressed as the mass of
moisture per unit volume.
2 −1
3.2.8 moisture diffusivity constant, D [L T ], n—the property of a material that describes the rate at which the material absorbs
z
or desorbs moisture.
3.2.8.1 Discussion—
In Fickian materials, this property is relatively independent of the moisture exposure level (and thus the moisture equilibrium
content material property). However, the moisture diffusivity constant is strongly influenced by temperature. Moisture diffusivity
can be anisotropic; the subscript z indicates the value in the through-the-thickness direction for anisotropic diffusion behavior.
3.2.9 moisture equilibrium, n—the condition reached by a material when there is essentially no further change in its average
moisture content with the surrounding environment.
3.2.9.1 Discussion—
Moisture equilibrium can be either absolute or effective. Absolute moisture equilibrium requires no measurable change in moisture
content, while effective moisture equilibrium allows a specified small change in the average moisture content of a material (the
accuracy criterion) over a specified time span (the reference time period). (See also accuracy criterion, average moisture content,
and reference time period.) Effective moisture equilibrium is a satisfactory definition for most engineering applications. Unless
otherwise specified, references to moisture equilibrium in this test method mean effective moisture equilibrium, as quantified in
10.2. Moisture equilibrium can also be either static, when there is no moisture transport at all across the surfaces, or dynamic, when
moisture transport exists, but the net sum for the material is zero. This test method is not capable of discerning between these two
types of moisture equilibrium.
3.2.10 moisture equilibrium content, M (%), n—the maximum amount of absorbed moisture that a material can contain at
m
moisture equilibrium for a given moisture exposure level, expressed as a percent of dry material mass. (See also moisture
saturation content.)
3.2.10.1 Discussion—
In polymer matrix composites, this property is relatively independent of temperature (and thus the moisture diffusivity constant
material property), but it is a function of the moisture exposure level. For the purposes of this test method, M is assumed to be
m
equivalent to the average moisture content at effective moisture equilibrium, M .
f
3.2.11 moisture exposure level, n—a measure or description of the severity of a conditioning environment in terms of the amount
of liquid or vapor present. (See also moisture and relative vapor level.)
3.2.12 moisture saturation content, n—the moisture equilibrium content at the maximum possible moisture exposure level,
wherein the material contains the greatest possible amount of absorbed moisture. (See also moisture equilibrium content.)
3.2.13 oven-dry, n—the condition of a material that has been dried in accordance with Procedure D of this test method until
moisture equilibrium is achieved.
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3.2.14 reference time period, n—the time interval for mass measurement used to define effective moisture equilibrium in a
material. (See also accuracy criterion, average moisture content, and moisture equilibrium.)
3.2.14.1 Discussion—
A small change in the average moisture content (the accuracy criterion) for a material during the reference time period indicates
effective moisture equilibrium.
3.2.15 relative vapor level (%), n—the ratio of the pressure of a vapor present to the pressure of the saturated vapor, at the same
temperature, expressed as a percent.
3.2.15.1 Discussion—
Applicable only to the gaseous form of a fluid. When the vapor is water vapor, the term is called relative humidity. (See also
moisture exposure level.)
3.2.16 standard laboratory atmosphere, n—an atmosphere (environment) having a temperature of 23 6 2 °C [73.4 6 3.6 °F]
and a relative humidity of 50 6 10 %.
3.2.16 standard conditioned specimen, n—the material condition of a test coupon that has reached effective moisture
equilibrium at a nominal relative humidity of 50 % (considered to be a standard laboratory environment) in accordance with
Procedure C of this test method.
3.2.17 standard laboratory atmosphere, n—an atmosphere (environment) having a temperature of 23 6 2 °C [73.4 6 3.6 °F]
and a relative humidity of 50 6 10 %.
3.2.18 test temperature, n—the environmental temperature used in Procedures A-E, Y, and Z.
3.2.18.1 Discussion—
This is distinguished, for the purposes of this test method, from the environmental temperature used during any subsequent material
evaluation testing.
3.2.19 traveler coupon, n—a surrogate coupon of the same material and thickness, and of appropriate size (but without tabs)
that is used in a conditioning procedure to determine moisture content for specimen configurations (such as a tabbed mechanical
coupon, or a coupon that does not meet the minimum mass requirement) that cannot otherwise be properly measured by this test
method.
3.3 Symbols:
3.3.1 c—moisture concentration.
3.3.2 D —moisture diffusivity constant in the through-the-thickness direction.
z
3.3.3 G(T,t)—moisture absorption or desorption function for materials that follow Fickian diffusion.
3.3.4 h—thickness of a material panel or plate in the through-the-thickness direction for double-sided moisture exposure.
3.3.5 M—average moisture content of a material. The following subscripts denote the average moisture content for specific
conditions:
M , the average moisture content at a baseline time;
b
M , the average moisture content at establishment of effective moisture equilibrium;
e
M , the average moisture content at establishment of effective moisture equilibrium as a delta from the average moisture content
ed
at a baseline time;
M , the average moisture content at establishment of effective moisture equilibrium as a total value from the condition of zero
et
moisture content;
M , the final moisture content at the end of conditioning for a fixed time;
f
M , the average moisture content at a given time;
i
M , the average moisture content at the previous time;
i − 1
M , the moisture loss from the state of effective equilibrium due to subsequent heating; and
L
M , the moisture equilibrium content that is reached when a uniform through-the-thickness moisture profile occurs for a given
m
temperature and moisture exposure level.
3.3.5.1 Discussion—
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Procedures A-H of this test method condition specimens to M . Except for the use of a thin specimen in Procedure A, conditioning
e
specimens to M is generally not practical. See also the discussion in Appendix X2.
m
3.3.6 t—time.
3.3.7 t —the maximum time required for a material to reach moisture equilibrium under specified conditions of temperature and
m
initial moisture content.
3.3.8 T —glass transition temperature.
g
3.3.9 w—the width of a nominally square moisture absorption test coupon.
3.3.10 W—the mass of a test coupon. The following subscripts are used to denote the mass of a test coupon for specific
conditions:
W , the mass at the baseline time;
b
W , the mass at a given time; and
i
W , the mass at the previous time.
i − 1
3.3.11 z—the coordinate axis in the through-the-thickness direction for a plate or panel.
4. Summary of Test Method
4.1 This is a gravimetric test method that monitors the change over time to the average moisture content of a material specimen
by measuring the total mass change of coupons that are exposed on two sides to a specified environment. There are a number of
test procedures described by this test method.
4.1.1 Procedure A covers the determination of the two Fickian moisture diffusion material properties, the moisture diffusivity
constant and the moisture equilibrium content. The other procedures cover material conditioning to a specific moisture
environment.
4.1.2 Procedure B covers non-ambient moisture conditioning of material coupons at a prescribed constant conditioning
environment prior to other types of testing. Sub-procedure codes are used to specify the conditioning environment, conditioning
time, and mass change monitoring procedure.
4.1.3 Procedure C covers the ambient conditioning of material coupons to a nominal relative humidity level of 50 %, prior to
other types of testing.
4.1.4 Procedure D covers the conditioning (drying) of material coupons to an essentially moisture-free condition.
4.1.5 Procedure E covers conditioning in two or more sequential steps using Procedure Bxxx.
4.1.6 Procedure Y covers the determination of the amount of moisture loss in conditioned material coupons when removed from
the conditioning environment (such as due to heating during cure of strain gauges).
4.1.7 Procedure Z covers the determination of the amount of moisture loss in conditioned material coupons due to heating to
the mechanical test temperature and holding at the test temperature for the duration of the mechanical test.
4.2 In Procedure A, the percent moisture mass gain versus time is monitored for thin material specimen(s) that are maintained
in a steady-state environment at a known temperature and moisture exposure level until the material reaches effective moisture
equilibrium, and thick material specimen(s) that are maintained in a steady-state environment at a known temperature and moisture
exposure level until the material is conditioned past the point of linear moisture gain. From the data obtained from these two
specimen thicknesses, the moisture equilibrium content, M , and the one-dimensional moisture absorption rate of the coupon may
m
be determined and the through-the-thickness moisture diffusivity constant, D , calculated.
z
4.3 In Procedure B, a general test coupon (not necessarily the coupon of Procedure A) is maintained, similarly to Procedure A,
in a steady-state environment at specified temperature and environmental exposure levels until the material reaches effective
moisture equilibrium.
4.4 In Procedure C, a general test coupon is maintained in a steady-state environment at a specified temperature and a relative
humidity of 50 % until the material reaches effective moisture equilibrium.
4.5 In Procedure D, a general test coupon is maintained in an air-circulating oven at a prescribed elevated temperature
environment until effective moisture equilibrium is reached.
4.6 In Procedure E, a general test coupon is conditioned in two or more sequential non-ambient steady-state environments.
4.7 In Procedure Y, a general test coupon is first conditioned to equilibrium using Procedure B, then is exposed to room
temperature ambient followed by an elevated temperature for defined times, then again conditioned to equilibrium.
4.8 In Procedure Z, a general test coupon is first conditioned to equilibrium using Procedure B, then is exposed to the same
testing environment (nominal ramp and soak time and an additional hold time to mimic the test time) as the specimens it represents.
5. Significance and Use
5.1 Procedure A is designed to produce moisture diffusion material property data that may be used as follows:
5.1.1 To determine approximate exposure times for coupon conditioning in Procedures B-E, Y, and Z;
5.1.2 As input to moisture prediction analysis computer codes; or
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5.1.3 For making qualitative decisions on material selection or performance under environmental exposure to various forms of
moisture.
5.2 Procedures B-E are designed to condition test coupons to a specified environmental condition or equilibrium state prior to
other material property testing (including(including, but not limited to, mechanical testing).
5.3 Procedures Y-Z are designed to determine the loss of moisture content due to removal of a test coupon from the conditioning
chamber (such as for strain gauge bonding) or due to heating of the test coupon prior to and during mechanical loading.
5.4 A single pair of tests on thin and thick specimens using Procedure A provides the moisture diffusivity constant, D , and the
z
moisture equilibrium content, M , at the given moisture exposure level and temperature. Multiple tests at differing temperatures
m
are required to establish the dependence of D on temperature. Multiple tests at differing moisture exposure levels are required to
z
establish the dependence of M on moisture exposure level.
m
NOTE 1—For many polymer matrix composites, the moisture diffusivity is usually only weakly related to relative humidity and is often assumed to
be a function only of temperature, usually following an Arrhenius-type exponential relation with inverse absolute temperature. For many of these
materials, moisture equilibrium content is only weakly related to temperature and is usually assumed to be a function only of relative humidity (1).
5.5 Vapor-exposure testing shall be used to condition the specimen when the in-service environmental condition is a vapor such
as humid air. Immersion in a liquid bath should be used to simulate vapor exposure only when apparent absorption properties are
desired for qualitative purposes. Properties determined in the latter manner shall be reported as apparent properties.
NOTE 2—For many polymer matrix composites, the moisture absorption properties under atmospheric humid conditions are generally not equivalent
to exposure either to liquid immersion or to pressurized steam. These latter environments may have different material diffusion characteristics.
6. Interferences
6.1 The calculation of the through-the-thickness moisture diffusivity constant in Procedure A assumes a single-phase Fickian
material that possesses constant moisture diffusivity properties through the thickness of the specimen. The validity of Procedure
A for evaluating the moisture diffusivity constant in a material of previously unknown moisture absorption behavior will be
uncertain prior to the test, as the test results themselves determine whether the material follows the single-phase Fickian diffusion
model. As discussed by Shirrell (2), previous investigators have shown that for diffusion to be rigorously classified as Fickian, it
must satisfy the following three conditions:
6.1.1 Both absorption and desorption curves must be essentially linear up to 60 % of M ;
m
6.1.2 Beyond the initially linear portion, both absorption and desorption curves must be concave to the abscissa axis until M
m
is reached; and
6.1.3 For the same environmental exposures, absorption curves resulting from different specimen thicknesses of the same
material must be essentially super-imposable if each curve is plotted in the form of a normalized sorption curve in which the
abscissa is =time/h,~=time!⁄h, instead of =time.
6.2 These conditions are rigorous, and may not be fully met by many engineering materials. In fact, these conditions may be
difficult to experimentally verify for certain materials, and for this reason, the decision on how rigorously these conditions must
be met for a given test material is left to the user. For example, a severe complete absorption/desorption cycle may cause damage
to a given material, causing cracking and providing a non-Fickian diffusion path, making evaluation of these conditions impossible.
6.3 However, there are a number of material forms or test conditions that are known to have the potential to violate one or more
of the assumptions used by this test method, or to potentially cause non-Fickian material behavior. Many of these issues are
discussed by several of the papers in ASTM STP 658 (3) or in the paper by Blikstad et alal. (4). They include:
6.3.1 Materials with fibers that are distributed in three dimensions, and that affect the moisture diffusion mechanism by means
such as wicking along the fiber/matrix interface, such as: materials stitched through-the-thickness, or,or some injection-molded
materials;
6.3.2 Materials with a significant amount of surface cracking;
6.3.3 Material systems that have been shown to behave in a non-Fickian manner, or that have multi-phase moisture diffusion
mechanisms as discussed by Bonniau and Bunsell (5);
6.3.4 Material systems that are known to have a moisture diffusivity constant that is strongly dependent upon moisture
concentration;
6.3.5 Material systems that are known to have a moisture diffusivity constant that is significantly time-dependent;
6.3.6 Material systems that are known to have a moisture diffusivity constant that is significantly stress-dependent, and that are
used in a laminate containing significant amounts of residual stress;
6.3.7 Material systems containing an abnormal amount of voids (porosity), or with a non-uniform void distribution, as discussed
by Harper et alal. (6). Moisture (in liquid or gaseous form) can fill the voids, resulting in an incorrect measurement of the amount
of moisture absorbed into the material, and can result in removal of specimens from the conditioning environment at a premature
time;
6.3.8 Test apparatus that produces a significant temperature gradient in the specimen, either through-the-thickness or in-plane,
as the material moisture diffusion constant is generally a strong function of temperature;
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6.3.9 Testing above the glass transition temperature of any constituent or phase-component within the composite material,
which generally results in non-Fickian or multiphase moisture diffusion behavior, or both;
6.3.10 Materials that lose mass during moisture conditioning (for example, materials that have water or fluid soluble
components); or
6.3.11 Materials that advance their cure state during exposure to water or water vapor (for example, some phenolic resins).
6.4 For materials with a very high moisture diffusion rate, a low moisture equilibrium content, or both, the time scales required
for periodic weighings may be very short (on the order of minutes or hours)hours), and extreme care must be taken with the mass
measurements and with the calibration and control of the environmental chamber, in order to avoid large measurement errors. The
most convenient solution for reducing the test sensitivity of these materials is to simply increase the thickness of the test specimen.
6.5 The definition of effective equilibrium allows for a small continual increase in moisture absorption at test termination.
Consequently, the moisture content of the conditioned coupons may not be truly representative of the effects of long term exposure.
Examples of materials that may exhibit significant continual moisture uptake after effective equilibrium include those with
excessive porosity, concentrated resin pockets, and wrinkled fibers. If prolonged exposure is a concern, conditioning to a real world
exposure lifetime is recommended, or at least moisture uptake should be interrogated in a timeframe significantly after reaching
effective equilibrium, as defined in this standard.
7. Apparatus
7.1 Balance—An analytical balance is required that shall be capable of the appropriate accuracy shown in Table 1.
NOTE 3—These accuracy requirements are derived from the definition of effective moisture equilibrium (Eq 6) and the specimen mass of 8.2.2, as
discussed in X2.10.
7.2 Oven or Vacuum Drying Chamber—An air-circulating oven is required that shall be capable of maintaining the required
temperatures to within 63 °C [65 °F]. A vacuum drying chamber or a vacuum oven may also be used.
7.3 Conditioning Chamber—A conditioning chamber is required that shall be capable of maintaining the required temperature
to within 63 °C [65 °F]. The chamber shall be monitored either on an automated continuous basis or on a manual basis at regular
intervals. The chamber shall consist of either of the following:
7.3.1 For Absorption by Vapor Exposure—A temperature and vapor-level controlled vapor exposure chamber that is capable of
maintaining the required relative vapor level to within 63 %, or
7.3.2 For Absorption by Liquid Immersion—A temperature-controlled liquid bath.
NOTE 4—While many newer models have solid-state controls, a great many environmental chambers control the chamber humidity via monitoring of
“dry-bulb” (actual) and “wet-bulb” (moisture depressed) temperatures, which are converted to equivalent relative humidity via a table or algorithm
supplied by the manufacturer. The ability of these chambers to control relative humidity is dependent on the accuracy of the thermometer readings.
Particularly important in these chambers is regular cleaning of the water reservoir, replacement of the wick, and maintenance of a proper contact between
the wick and the wet-bulb thermometer. Chambers that control the dry-bulb temperature and the differential between the dry-bulb and wet-bulb
temperatures generally have improved control of chamber relative humidity over those that control the dry-bulb and wet-bulb temperatures.
NOTE 5—Since loss of the water supply to a humidity chamber results in the conditioning environment changing to a drying condition with often a
significant delay to the desired moisture conditioning, the use of a real time power and water supply monitoring and alarm system for the chamber is
recommended. The alarm system should be able to contact off-site lab personnel in the event of an anomaly. A further recommendation is to use a system
to shut off the chamber heat when a water supply or humidity fault is detected.
7.4 Micrometers and Calipers—A micrometer with a 4 to 7 mm [0.16 to 0.28 in.] nominal diameter ball interface shall be used
to measure the specimen thickness when at least one surface is irregular (such as the bag-side of a laminate). A micrometer with
a 4 to 7 mm [0.16 to 0.28 in.] nominal diameter ball interface or with a flat anvil interface shall be used to measure the specimen
thickness when both surfaces are smooth (such as tooled surfaces). A micrometer or caliper, with a flat anvil interface, shall be used
to measure the width and length of the specimen. The accuracy of the instruments shall be suitable for reading to within 1% of
the sample dimensions. For typical specimen geometries, an instrument with an accuracy of 60.0025 mm [60.0001 in.] is
adequate for the thickness measurement, while an instrument with an accuracy of 60.025 mm [60.001 in.] is adequate for the
width and length measurements.
7.5 Desiccator—A clean, dry desiccator in which specimens being oven-dried shall be brought to laboratory temperature
following removal of the specimens from the oven.
7.6 Specimen Bag—A sealable, flexible, moisture-proof bag (or other suitable sealable container) made of material suitable for
exposure to specimens that have been removed from the conditioning chamber for cooling prior to weighing. Bags that meet the
requirements of MIL-B-131 have been found satisfactory for use in standard applications.
TABLE 1 Balance Accuracy
Specimen Mass, g Balance Accuracy Requirement, mg
$5 but <50 0.1
$50 1.0
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7.7 Absorbent Cloth—Clean, non-linting absorbent cloth for use in wiping exuded or condensed moisture from test specimens.
7.8 Gloves—Clean, non-linting gloves for use when handling specimens.
8. Test Specimen
8.1 Sampling of Test Specimens:
8.1.1 Procedure A—testTest a minimum of one "thin" coupon and one "thick" coupon. Testing of three (3) replicates of each
coupon thickness is recommended when sufficient material is available.
8.1.2 Procedures B-E—whenWhen a group of test specimens of the same material and thickness for subsequent material
evaluation are to be conditioned at the same time, and periodic weighing of the specimens is required by the procedure, a minimum
of three (3) specimens or three traveler coupons from the group shall be weighed. See 8.2.5 for a discussion of when traveler
coupons should be used. If the group of test specimens are not "dried" prior to moisture conditioning, the initial moisture content,
M , of the material prior to conditioning may be determined by either (a) drying the traveler coupons using Procedure D after
b
moisture conditioning has been completed, (b) drying using Procedure D an additional three traveler coupons, or (c) if the material
diffusivity constant and effective moisture equilibrium content are known, by using the procedures in Appendix X3.
NOTE 6—In some cases, the "dry" weight prior to moisture conditioning to equilibrium may not be equal to the "dry" weight when subsequently dried
after moisture conditioning (see Section 6)), in which case (a) and (b) above may not be equivalent. If this situation is suspected and determination of
an accurate initial moisture content is required, then tests using both approaches are recommended.
8.1.3 Procedure Y—In cases where specimens are required to be removed from the conditioning environment prior to testing
(such as the case where elevated temperature testing requires the use of high temperature cures (190 °C [375 °F]) for the strain
gauge adhesive and the strain gauges are bonded after moisture conditioning), the loss of moisture during the time out of the
conditioning environment should be quantified by a minimum of three (3) "moisture loss" specimens that represent each material
and laminate thickness. Mechanical test specimens should be re-conditioned for the re-conditioning time duration determined by
the "moisture loss" specimens.
8.1.4 Procedure Z—The moisture loss during testing at elevated temperatures should be quantified by a minimum of three (3)
“moisture loss” specimens that represent each: material, laminate thickness, hot/wet specimen geometry (width and length), and
test temperature. Separate moisture loss specimens shall be used for fixtured and non-fixtured specimens with the same dimensions.
Moisture loss specimens are not required to be tabbed or notched, even if the specimens they represent are tabbed or notched. When
simulating tabbed specimens, the moisture loss specimens may be gripped using un-bonded, simulated tabs to prevent specimen
damage and mimic heat transfer through tabs into grips.
8.2 Test Specimen Geometry:
8.2.1 Summary—The following requirements are summarized in Table 2 for ease of reference.
8.2.2 Specimen Mass Requirement—Specimens (including travelers) shall have a mass of at least 5.0 g (see X2.10). Specimen
mass affects the balance accuracy requirement established in 7.1.
8.2.3 Specimen Thickness—The specimen thickness shall not vary by more than 65 % over the surface of the specimen and
shall comply with 8.2.2 and Eq 2, as applicable.
NOTE 7—No minimum specimen thickness is required. However, the specimen thickness has a profound effect on the total time required to reach
TABLE 2 Summary of Specimen Geometry Requirements
Property Testing Procedure A–Thick Specimen Conditioning Procedures B-Z
Known Reference Time Period: Known Specimen Thickness:
(1) Determine the reference time period from 10.1.7.1. If this is
(1) Determine the maximum thickness from h5 D t/0.04. If a
œ z
unacceptable, then the specimen thickness must be changed.
thicker specimen is required, then the reference time period must be
(2) Estimate the specimen mass from the material density, known
changed. This equation is valid for the 0.02 % moisture change criteria in
thickness, and the configuration. Specimen mass shall be $5 g. If the esti-
10.2; if a different value for effective equilibrium moisture change is used,
mated mass is too small, or the specimen has attached tabs or other features
see 10.1.8 and Appendix X2.
that violate the assumptions of this test method, then a traveler coupon must be
(2) Determine the plate size from either Eq 2 (non-sealed edges) or
used.
8.2.4.2 (2) (sealed edges).
(3) Estimate the specimen mass from Mass = w × h × density. The
specimen mass shall be $5 g. If the estimated mass is too small, then
the plate size must be increased (or the specimen made thicker and the
reference time period correspondingly increased).
Known Specimen Thickness:
(1) Determine the reference time period from 10.1.7.1. If the value so
determined is unacceptable, then the specimen thickness must be
changed.
(2) Determine the plate size from either Eq 2 (non-sealed edges) or
8.2.4.2 (2) (sealed edges).
(3) Estimate the specimen mass from Mass = w × h × density. The
specimen mass shall be $5 g. If the estimated mass is too small, then
the plate size must be increased (or the specimen made thicker and the
reference time period correspondingly increased).
D5229/D5229M − 20
equilibrium, as well as on the reference time period of 10.1.7.1. Also, when designing a coupon, consideration should be given to the macrostructure of
the composite material in the through-the-thickness direction. If the moisture absorption coupon is substantially thinner than the material in the end-use
form, there should be sufficient number of fibers through the thickness that the absorption properties of the material coupon can be considered equivalent
to the absorption properties of the same material in a much thicker form, under the same environmental conditions. A thin (even one-ply) laminate, if
reinforced by a significant number of fibers that are small in diameter relative to the thickness, could be acceptable if it met the other specimen geometry
requirements of 8.2. However, a substantially thicker multi-ply laminate, reinforced by fibers having a diameter on the order of the ply thickness, may
not be acceptable. A minimum laminate thickness of 10 times the nominal fiber diameter is recommended.
8.2.4 Specimen Size and Shape For Use With Procedure A:
8.2.4.1 Thin Specimen—Since the purpose of the "thin" test specimen is only for moisture equilibrium content determination,
there is no size requirement other than the minimum mass in accordance with 8.2.2.
8.2.4.2 Thick Specimen—As edge effects must be minimized in materials with anisotropic moisture diffusivity constants in order
to accurately determine the through-thickness diffusion constant, the "thick" test specimen shall consist of either 8.2.4.2 (1) or
8.2.4.2 (2) below. The "thick" test specimen for moisture diffusivity constant determination shall be thick enough such that
achieving a moisture content of approximately 70 % of the moisture equilibrium content for the same exposure conditions shall
require a minimum of 35 days of exposure (if less time is required, then a repeat of the test with a thicker specimen is
recommended).
(1) A nominally square plate or curved panel with dimensions that satisfy the relation:
w
$ 100 (2)
h
where:
w = nominal length of one side, mm [in.], and
h = nominal thickness, mm [in.].
(2) A 100 6 10 mm [4.0 6 0.5 in.] square plate with stainless steel foil bonded to the edges such that moisture absorption
through the edges is essentially eliminated. When this specimen is prepared, care shall be taken to weigh the coupon both before
and after bonding of the foil in order to obtain the mass increase due to the foil and the adhesive. The adhesive used shall be
incapable of absorbing sufficient moisture to affect the results.
NOTE 8—A typical "thin" specimen for the carbon/epoxy material described in X2.2 having dimensions of 1 mm [0.040 in.] thick by 100 mm [4 in.]
square would have a mass of approximately 18 g. If conditioned at 74 °C [170 °F] and 90 % relative humidity, use of Eq X1.7 (using an accuracy criteria
of 0.02 % and a maximum difference between M and M of 0.02 %) predicts that this specimen would reach equilibrium in approximately 57 days. The
m f
minimum reference time period used to test equilibrium is established by 10.1.7.1 as the greater of 0.04 h /D (equal to 44 h) or 24 h; rounding to a
z
practical even time gives a reference period of 2 days. A typical "thick" specimen for the carbon/epoxy material described in X2.2 may have dimensions
of 3.0 mm [0.120 in.] thick by 100 mm [4 in.] square with sealed edges, satisfying 8.2.4.2 (2). If conditioned at 74 °C [170 °F] and 90 % relative humidity,
use of Eq X1.7 (using the same criteria) predicts that this specimen would reach 70 % of the effective moisture equilibrium in approximately 38 days.
8.2.5 Specimen Size and Shape For Use With Procedures B-Z—The specimen size and shape requirement for Procedure A
(8.2.4) is not a requirement for the conditioning procedures (B-Z) of this test method. The coupon size and shape used in
Procedures B-Z is normally that required for subsequent material evaluation following conditioning, as long as the coupon meets
the mass and thickness requirements of 8.2.2 and 8.2.3. When the coupon is of such type or geometry that the moisture change
in the material cannot be properly measured by weighing the specimen itself, traveler coupon(s) of the same material and
thickness, and of appropriate size (but without tabs, if present) shall be used to determine moisture equilibrium for the specimens
being conditioned. Material evaluation tests that require traveler moisture conditioning coupons include mechanical tests using
tabbed coupons, specimens containing fasteners, specimens with strain gauges, and test methods using coupons that do not meet
the minimum mass requirement for this test method, such as commonly used in thermo-mechanical analysis methods.
8.2.6 Preparation—In specimens cut from plates, precautions shall be taken to avoid notches, undercuts, rough or uneven
surfaces, or delaminations due to inappropriate machining methods. Final dimensions should be obtained by water lubricated
precision milling or grinding, or both, or the use of a wet diamond saw. The procedure used shall be reported.
8.2.7 Labeling—Label the specimen coupons so as to be distinct from each other in a manner that will both be unaffected by
the test and not influence the test. The coupon must be weighed prior to adding the label (see 10.3.5) when using a marking method
that adds mass to the coupon. Examples of various marking methods include coded wire overwrap and edge marking.
NOTE 9—A coded-wire overwrap is a wire, of a material (such as stainless steel) that is substantially unaffected by the pending environmental exposure.
The wire is wrapped around the specimen tightly enough to prevent loss of the wire, but loosely enough that it does not interfere with the absorption
process. The wire is coded by various means, including, but not limited to, tags, notches, knots, or color.
9. Calibration of Apparatus
9.1 The accuracy of all measuring equipment shall have certified calibrations that are current at the time of use of the equipment.
10. Procedures
10.1 Parameters To Be Specified Prior To Test:
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10.1.
...