ASTM D5229/D5229M-92(1998)e1
(Test Method)Standard Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite Materials
Standard Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite Materials
SCOPE
1.1 This test method covers a procedure (Procedure A) 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 equilibrium in a non-laboratory environment (Procedure B), to equilibrium in a standard laboratory atmosphere environment (Procedure C), or to an essentially moisture-free state (Procedure D). 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 MIL-HDBK-17B (1), which describes the desirable attributes of a conditioning and moisture property determination procedure.
1.6 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
1.7 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text the inch-pound units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.
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e1
Designation: D 5229/D 5229M – 92 (Reapproved 1998)
Standard Test Method for
Moisture Absorption Properties and Equilibrium
Conditioning of Polymer Matrix Composite Materials
This standard is issued under the fixed designation D 5229/D 5229M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
e NOTE—An incorrect Fig. 1 was inadvertently placed in the 1998 reapproval.
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 D 570 and Practices D 618 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 phase matrices such as toughened epoxies may require a
multi-phase moisture absorption model. While the test proce-
1.1 This test method covers a procedure (Procedure A) for
dures themselves may be used for multi-phase materials, the
the determination of moisture absorption or desorption prop-
calculations used to determine the moisture diffusivity constant
erties in the through-the-thickness direction for single-phase
in Procedure A are applicable only to single-phase materials.
Fickian solid materials in flat or curved panel form. Also
Other examples of materials and test conditions that may not
covered are procedures for conditioning test coupons prior to
meet the requirements are discussed in Section 1.4.
use in other test methods; either to equilibrium in a non-
1.3 The evaluation by Procedure A of the moisture equilib-
laboratory environment (Procedure B), to equilibrium in a
rium content material property does not assume, and is
standard laboratory atmosphere environment (Procedure C), or
therefore not limited to, single-phase Fickian diffusion behav-
to an essentially moisture-free state (Procedure D). While
ior.
intended primarily for laminated polymer matrix composite
1.4 The procedures used by this test method may be
materials, these procedures are also applicable to other mate-
performed, and the resulting data reduced, by suitable auto-
rials that satisfy the assumptions of 1.2.
matic equipment.
1.2 The calculation of the through-the-thickness moisture
1.5 This test method is consistent with the recommendations
diffusivity constant in Procedure A assumes a single-phase
of MIL-HDBK-17B (1), which describes the desirable at-
Fickian material with constant moisture absorption properties
tributes of a conditioning and moisture property determination
through the thickness of the specimen. The validity of the
procedure.
equations used in Procedure A for evaluating the moisture
1.6 This standard does not purport to address all of the
diffusivity constant in a material of previously unknown
safety concerns, if any, associated with its use. It is the
moisture absorption behavior is uncertain prior to the test, as
responsibility of the user of this standard to establish appro-
the test results themselves determine if the material follows the
priate safety and health practices and determine the applica-
single-phase Fickian diffusion model. A reinforced polymer
bility of regulatory limitations prior to use.
matrix composite material tested below its glass-transition
1.7 The values stated in either SI units or inch-pound units
temperature typically meets this requirement, although two-
are to be regarded separately as standard. Within the text the
inch-pound units are shown in brackets. The values stated in
This test method is under the jurisdiction of ASTM Committee D-30 on High
Composite Materials and is the direct responsibility of Subcommittee D30.04 on
Lamina and Laminate Test Methods. The boldface numbers in parentheses refer to the list of references at the end of
Current edition approved Feb. 15, 1992. Published June 1992. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 5229/D 5229M
each system are not exact equivalents; therefore, each system
where:
must be used independently of the other. Combining values
W = current specimen mass, g, and
i
from the two systems may result in nonconformance with the
W = oven-dry specimen mass, g.
o
standard.
(See also oven-dry.)
3.2.3 Fickian diffusion, n—a model of material moisture
2. Referenced Documents
absorption and desorption that follows Fick’s second law, as
2.1 ASTM Standards:
follows in one-dimension:
D 570 Test Method for Water Absorption of Plastics
]c ] c
D 618 Practice for Conditioning Plastics for Testing
5D
z 2
]t
]z
D 792 Test Methods for Specific Gravity (Relative Density)
3.2.4 glass transition temperature, T [Q], n—the approxi-
of Plastics by Displacement
g
mate midpoint of the temperature range over which a reversible
D 883 Terminology Relating to Plastics
change takes place between a viscous or rubbery condition and
D 2584 Test Method for Ignition Loss of Cured Reinforced
a hard, relatively brittle condition, in an amorphous polymer, or
Resins
in amorphous regions of a partially crystalline polymer.
D 2734 Test Methods for Void Content of Reinforced Plas-
3.2.4.1 Discussion—The glass transition temperature of
tics
many polymer matrix composites is lowered by the presence of
D 3171 Test Method for Fiber Content of Resin-Matrix
absorbed moisture.
Composites by Matrix Digestion
3.2.5 moisture, n—liquid (water, jet fuel, salt water, or any
D 3878 Terminology of High-Modulus Reinforcing Fibers
other liquid) that is either diffused in relatively small quantity
and Their Composites
and dispersed through a gas as a vapor, condensed on a surface
2.2 Military Standard:
as visible dew, or present in quantity sufficient for immersion
MIL-B-131 Barrier Materials, Watervaporproof,
of an object.
Greaseproof, Flexible, Heat-Sealable
3.2.5.1 Discussion—The dictionary definition of moisture
3. Terminology
for this test method is extended to include not only the vapor
3.1 Definitions—Terminology D 3878 defines terms relat- of a liquid and its condensate, but the liquid itself in large
ing to high-modulus fibers and their composites. Terminology quantities, as for immersion.
−3
3.2.6 moisture concentration, c [ML ], n—the absolute
D 883 defines terms relating to plastics. In the event of a
conflict between terms, Terminology D 3878 shall have prece- amount of absorbed moisture in a material expressed as the
mass of moisture per unit volume.
dence over the other terminology standards.
2 −1
3.2 Definitions of Terms Specific to This Standard—If the 3.2.7 moisture diffusivity constant, D [L T ], n—the prop-
z
erty of a material that describes the rate at which the material
term represents a physical quantity, its analytical dimensions
are stated immediately following the term (or letter symbol) in absorbs or desorbs moisture.
3.2.7.1 Discussion—In Fickian materials this property is
fundamental dimension form, using the following ASTM
standard symbology for fundamental dimensions, shown relatively independent of the moisture exposure level (and thus
the moisture equilibrium content material property). However,
within square brackets: [M] for mass, [L] for length, [T] for
time, [Q] for thermodynamic temperature, and [nd] for non- the moisture diffusivity constant is strongly influenced by
temperature. Moisture diffusivity can be anisotropic; the sub-
dimensional quantities. Use of these symbols is restricted to
analytical dimensions when used within square brackets, as the script z indicates the value in the through-the-thickness direc-
symbols may have other definitions when used without the tion for anisotropic diffusion behavior.
brackets. 3.2.8 moisture equilibrium, n—the condition reached by a
3.2.1 accuracy criterion, n—the maximum amount of material when there is essentially no further change in its
change in average moisture content for a test coupon, over the average moisture content with the surrounding environment.
span of the reference time period, which is allowable for the Moisture equilibrium can be either absolute or effective.
establishment of effective moisture equilibrium. (See also Absolute moisture equilibrium requires no measurable change
average moisture content, moisture equilibrium, and reference in moisture content, while effective moisture equilibrium
time period.) allows a specified small change in the average moisture content
3.2.2 average moisture content, M (%), n—the average of a material (the accuracy criterion) over a specified time span
(the reference time period). (See also accuracy criterion,
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 average moisture content, and reference time period.)
3.2.8.1 Discussion—Effective moisture equilibrium is a sat-
oven-dry material and expressed as a percentage, as follows:
isfactory definition for most engineering applications. Unless
W 2W
i o
M,%5 3100 (1)
otherwise specified, references to moisture equilibrium in this
W
o
test method mean effective moisture equilibrium, as quantified
in 10.2. Moisture equilibrium can also be either static, when
Annual Book of ASTM Standards, Vol 08.01.
there is no moisture transport at all across the surfaces, or
Annual Book of ASTM Standards, Vol 08.02.
dynamic, when moisture transport exists, but the net sum for
Annual Book of ASTM Standards, Vol 15.03.
the material is zero. This test method is not capable of
Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700
Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS. discerning between these two types of moisture equilibrium.
D 5229/D 5229M
3.2.9 moisture equilibrium content, M (%), n—the maxi- 3.3.3 G(T,t)—moisture absorption or desorption function
m
mum amount of absorbed moisture that a material can contain for materials that follow Fickian diffusion.
at moisture equilibrium for a given moisture exposure level, 3.3.4 h—thickness of a material panel or plate in the
expressed as a percent of dry material mass. (See also moisture through-the-thickness direction for double-sided moisture ex-
saturation content.) posure.
3.2.9.1 Discussion—In polymer matrix composites this 3.3.5 M—average moisture content of a material. The fol-
lowing subscripts denote the average moisture content for
property is relatively independent of temperature (and thus the
moisture diffusivity constant material property), but it is a specific conditions: M , the average moisture content at a
b
baseline time; M , the average moisture content at establish-
function of the moisture exposure level. For the purposes of
f
this test method M is assumed to be equivalent to the average ment of effective moisture equilibrium; M , the average mois-
m i
ture content at a given time; M , the average moisture
moisture content at effective moisture equilibrium, M .
i −1
f
content at the previous time; and M , the moisture equilibrium
3.2.10 moisture exposure level, n—a measure or description
m
content that is reached when a uniform through-the-thickness
of the severity of a conditioning environment in terms of the
moisture profile occurs for a given temperature and moisture
amount of liquid or vapor present. (See also moisture and
exposure level.
relative vapor level.)
3.3.5.1 Discussion—For the purposes of this test method
3.2.11 moisture saturation content, n—the moisture equilib-
M and M are assumed to be equivalent.
rium content at the maximum possible moisture exposure level, m f
3.3.6 t—time.
wherein the material contains the greatest possible amount of
3.3.7 t —the maximum time required for a material to
absorbed moisture. (See also moisture equilibrium content.) m
reach moisture equilibrium under specified conditions of tem-
3.2.12 oven-dry, n—the condition of a material that has
perature and initial moisture content.
been dried in accordance with Procedure D of this test method
3.3.8 T —glass transition temperature.
until moisture equilibrium is achieved. g
3.3.9 w—the width of a nominally square moisture absorp-
3.2.13 reference time period, n—the time interval for mass
tion test coupon.
measurement used to define effective moisture equilibrium in a
3.3.10 W—the mass of a test coupon. The following sub-
material. (See also accuracy criterion, average moisture con-
scripts are used to denote the mass of a test coupon for specific
tent, and moisture equilibrium.)
conditions: W , the mass at the baseline time; W , the mass at
b i
3.2.13.1 Discussion—A small change in the average mois-
a given time; and W , the mass at the previous time.
i−1
ture content (the accuracy criterion) for a material during the
3.3.11 z—the coordinate axis in the through-the-thickness
reference time period indicates effective moisture equilibrium.
direction for a plate or panel.
3.2.14 relative vapor level (%), n—the ratio of the pressure
of a vapor present to the pressure of the saturated vapor, at the
4. Summary of Test Method
same temperature, expressed as a percent. Applicable only to
4.1 This is a gravimetric test method that monitors the
the gaseous form of a fluid. When the vapor is water vapor the
change over time to the average moisture content of a material
term is called relative humidity. (See also moisture exposure
specimen by measuring the total mass change of a coupon that
level.)
is exposed on two sides to a specified environment. There are
3.2.15 standard laboratory atmosphere, n—an atmosphere
four test procedures described by this test method. Procedure A
(environment) having a temperature of 23 6 2°C
covers the determination of the two Fickian moisture diffusion
[73.4 6 3.6°F] and a relative humidity of 50 6 10 %.
material properties, the moisture diffusivity constant and the
3.2.16 standard conditioned specimen, n—the material con-
moisture equilibrium content. The other three procedures cover
dition of a test coupon that has reached effective moisture
material conditioning to a specific moisture environment;
equilibrium at a nominal relative humidity of 50 % in accor-
Procedure B covers general moisture condi
...
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