ASTM D2734-16

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D2734 − 09 D2734 − 16
Standard Test Methods for
1
Void Content of Reinforced Plastics
This standard is issued under the fixed designation D2734; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
1.1 These test methods cover the void content of reinforced plastics or “composites.” The test methods are applicable to
composites for which the effects of ignition on the materials are known. Most plastics, glass, and reinforcements fall into this class.
These test methods are not applicable to composites for which the effects of ignition on the plastics, the reinforcement, and any
fillers are unknown. This class may include silicone resins, which do not burn off completely, reinforcements consisting of metals,
organic materials, or inorganic materials which may gain or lose weight, and fillers consisting of oxides, carbonates, etc., which
may gain or lose weight. Note that separate weight loss tests of individual materials will usually, but not necessarily, give the same
result as when all the materials are combined.
NOTE 1—There is no known ISO equivalent to these test methods.
1.2 The values stated in SI units are to be regarded as standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2
2.1 ASTM Standards:
D618 Practice for Conditioning Plastics for Testing
D792 Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement
D1505 Test Method for Density of Plastics by the Density-Gradient Technique
D2584 Test Method for Ignition Loss of Cured Reinforced Resins
3. Summary of Test Methods
3.1 The densities of the resin, the reinforcement, and the composites are measured separately. Then the resin content is measured
and a theoretical composite density calculated. This is compared to the measured composite density. The difference in densities
indicates the void content. A good composite may have 1 % voids or less, while a poorly made composite can have a much higher
void content. Finite values under 1 % should be recognized as representing a laminate density quality, but true void content level
must be established by complementary tests or background experience, or both.
4. Significance and Use
4.1 The void content of a composite may significantly affect some of its mechanical properties. Higher void contents usually
mean lower fatigue resistance, greater susceptibility to water penetration and weathering, and increased variation or scatter in
strength properties. The knowledge of void content is desirable for estimation of quality of composites.
5. Interferences
5.1 The density of the resin, in these test methods, is assumed to be the same in the composite as it is in a large cast mass.
Although there is no realistic way to avoid this assumption, it is nevertheless not strictly correct. Differences in curing, heat and
1
These test methods are under the jurisdiction of ASTM Committee D20 on Plastics and are the direct responsibility of Subcommittee D20.18 on Reinforced Thermosetting
Plastics.
Current edition approved Sept. 1, 2009Sept. 1, 2016. Published September 2009September 2016. Originally approved in 1968. Last previous edition approved in 20032009
as D2734 – 94D2734 – 09.(2003). DOI: 10.1520/D2734-09.10.1520/D2734-16.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D2734 − 16
pressure, and molecular forces from the reinforcement surface all change the composite resin density from the bulk resin density.
The usual change is that bulk density is lower, making void content seem lower than it really is.
5.
...

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D2734 − 16
Standard Test Methods for
1
Void Content of Reinforced Plastics
This standard is issued under the fixed designation D2734; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* D2584 Test Method for Ignition Loss of Cured Reinforced
Resins
1.1 These test methods cover the void content of reinforced
plastics or “composites.” The test methods are applicable to
3. Summary of Test Methods
composites for which the effects of ignition on the materials are
3.1 The densities of the resin, the reinforcement, and the
known. Most plastics, glass, and reinforcements fall into this
composites are measured separately. Then the resin content is
class. These test methods are not applicable to composites for
measured and a theoretical composite density calculated. This
which the effects of ignition on the plastics, the reinforcement,
is compared to the measured composite density. The difference
and any fillers are unknown. This class may include silicone
in densities indicates the void content. A good composite may
resins, which do not burn off completely, reinforcements
have 1 % voids or less, while a poorly made composite can
consisting of metals, organic materials, or inorganic materials
have a much higher void content. Finite values under 1 %
which may gain or lose weight, and fillers consisting of oxides,
should be recognized as representing a laminate density
carbonates, etc., which may gain or lose weight. Note that
quality, but true void content level must be established by
separate weight loss tests of individual materials will usually,
complementary tests or background experience, or both.
but not necessarily, give the same result as when all the
materials are combined.
4. Significance and Use
NOTE 1—There is no known ISO equivalent to these test methods.
4.1 The void content of a composite may significantly affect
1.2 The values stated in SI units are to be regarded as
some of its mechanical properties. Higher void contents
standard.
usually mean lower fatigue resistance, greater susceptibility to
1.3 This standard does not purport to address all of the
water penetration and weathering, and increased variation or
safety concerns, if any, associated with its use. It is the
scatter in strength properties. The knowledge of void content is
responsibility of the user of this standard to establish appro-
desirable for estimation of quality of composites.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. 5. Interferences
5.1 The density of the resin, in these test methods, is
2. Referenced Documents
assumed to be the same in the composite as it is in a large cast
2
mass. Although there is no realistic way to avoid this
2.1 ASTM Standards:
D618 Practice for Conditioning Plastics for Testing assumption, it is nevertheless not strictly correct. Differences in
D792 Test Methods for Density and Specific Gravity (Rela- curing, heat and pressure, and molecular forces from the
tive Density) of Plastics by Displacement reinforcement surface all change the composite resin density
D1505 Test Method for Density of Plastics by the Density- from the bulk resin density. The usual change is that bulk
Gradient Technique density is lower, making void content seem lower than it really
is.
5.2 For composites with high void contents, this error will
1
These test methods are under the jurisdiction of ASTM Committee D20 on lower the true value an insignificant amount, from a true 7 %
Plastics and are the direct responsibility of Subcommittee D20.18 on Reinforced
down to a calculated 6.7 %, for example. For composites with
Thermosetting Plastics.
low and void contents, the value may be lowered from a true
Current edition approved Sept. 1, 2016. Published September 2016. Originally
0.2 % to a calculated − 0.1 %. This would indicate an obvious
approved in 1968. Last previous edition approved in 2009 as D2734 – 09. DOI:
10.1520/D2734-16.
error, and illustrates that as the void content gets lower the
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
constant error in resin density gets progressively more impor-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
tant. Note that these values are for example only, that different
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. resin systems can give different errors, and that it is left to the
*A Summary of Changes section ap
...