ASTM D5323-92(2011)

Standard Practice for Determination of 2 % Secant Modulus for Polyethylene Geomembranes

SIGNIFICANCE AND USE
Where to draw the tangent to determine the modulus of elasticity is often unclear when performing tensile tests with polyethylene geomembranes. This problem results in a wide variation in test results and therefore makes this property unreliable for comparisons.
A secant modulus based on 2 % strain can be useful when making comparisons between materials, in quality control, and in comparing the same sample after being subjected to a nonstandard environment.  
Secant modulus is an approximation of modulus of elasticity and generally results in a lower value than that for the modulus of elasticity.
Although the technique for measuring 2 % secant modulus is described here, other percent secant moduli can be measured by this practice.
SCOPE
1.1 This practice presents a technique for calculating the 2 % secant modulus for polyethylene geomembranes between 0.5 and 5 mm (20 and 200 mil) using Test Method D638.  
1.2 This practice will facilitate modulus comparisons of similar materials by standardizing the method for deriving the points on the stress-strain curve from which the calculations are performed.
1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.  
1.4 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 consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-May-2011
• ICS: 59.080.70 - Geotextiles
• Technical Committee: D35 - Geosynthetics
• Drafting Committee: D35.10 - Geomembranes

Relations

• Replaces: ASTM D5323-92(2006) - Standard Practice for Determination of 2 % Secant Modulus for Polyethylene Geomembranes
• Effective Date: 01-Jun-2011
• Replaced By: ASTM D5323-92(2018) - Standard Practice for Determination of 2 % Secant Modulus for Polyethylene Geomembranes
• Effective Date: 01-Jul-2018
• Referred By: ASTM D4439-23b - Standard Terminology for Geosynthetics
• Effective Date: 01-Jun-2011
• Referred By: ASTM D5747/D5747M-21 - Standard Practice for Tests to Evaluate the Chemical Resistance of Geomembranes to Liquids
• Effective Date: 01-Jun-2011
• Referred By: ASTM D6434-12(2018) - Standard Guide for the Selection of Test Methods for Flexible Polypropylene Geomembranes
• Effective Date: 01-Jun-2011

Standards Content (Sample)

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: D5323 − 92 (Reapproved 2011)
Standard Practice for
Determination of 2 % Secant Modulus for Polyethylene
Geomembranes
This standard is issued under the fixed designation D5323; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope modulus of elasticity (or elastic modulus). Since the existence
ofatrueproportionallimitinpolyethyleneisquestionable,and
1.1 This practice presents a technique for calculating the
with the impracticality of measuring it reliably, the use of
2% secant modulus for polyethylene geomembranes between
secant modulus for comparative evaluations is preferred.
0.5 and 5 mm (20 and 200 mil) using Test Method D638.
3.1.2 secant modulus, n—the ratio of stress (nominal) to
1.2 This practice will facilitate modulus comparisons of
corresponding strain at any specified point on the stress-strain
similar materials by standardizing the method for deriving the
curve.
points on the stress-strain curve from which the calculations
3.1.2.1 Discussion—The measurement units for secant
are performed.
modulus may change, depending on the standard used. For the
1.3 The values stated in SI units are to be regarded as the
purposes of this practice, the measurement units shall be force
−2
standard. The values given in parentheses are for information
per unit area (FL ), such as megapascals (pounds-force per
only.
square inch).
1.4 This standard does not purport to address all of the
4. Significance and Use
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to consult and
4.1 Where to draw the tangent to determine the modulus of
establish appropriate safety and health practices and deter-
elasticity is often unclear when performing tensile tests with
mine the applicability of regulatory limitations prior to use.
polyethylene geomembranes. This problem results in a wide
variation in test results and therefore makes this property
2. Referenced Documents
unreliable for comparisons.
2.1 ASTM Standards:
4.2 A secant modulus based on 2% strain can be useful
D638Test Method for Tensile Properties of Plastics
when making comparisons between materials, in quality
control, and in comparing the same sample after being sub-
3. Terminology
jected to a nonstandard environment.
3.1 Definitions:
4.3 Secant modulus is an approximation of modulus of
−2
3.1.1 modulus of elasticity, MPa (FL ),n—the ratio of
elasticityandgenerallyresultsinalowervaluethanthatforthe
stress(nominal)tocorrespondingstrainbelowtheproportional
modulus of elasticity.
limit of a material, expressed in force per unit area, such as
4.4 Althoughthetechniqueformeasuring2%secantmodu-
megapascals (pounds-force per square inch).
lus is described here, other percent secant moduli can be
3.1.1.1 Discussion—The stress-strain relations of many
measured by this practice.
plastics do not conform to Hooke’s law throughout the elastic
range, but rather deviate therefrom even at strains well below
5. Procedure
the elastic limit. For such materials, the slope of the tangent to
the stress-strain curve at a low strain is usually taken as the
5.1 Follow the test procedure described in Test Method
D638.
5.1.1 A cross-head speed of 50 mm/min (2 ipm) is recom-
This practice is under the jurisdiction of ASTM Committee D35 on Geosyn-
mendedfordeterminingsecantmodulus,regardlessofthetype
thetics and is the direct responsibility of Subcommittee D35.10 on Geomembranes.
of geomembrane being evaluated. Faster cross-head speeds
CurrenteditionapprovedJune1,2011.PublishedJuly2011.Originallyapproved
reduce resolution of the points on the curve.
in 1992. Last previous edition approved in 2006 as D5323–92(2006). DOI:
10.1520/D5323-92R11.
5.1.2 High resolution of load and cross-head movement is
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
important for obtaining accurate and reproducible values.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Where possible, use settings on the testing equipment that will
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. magnify this region.
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D5323 − 92 (2
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