ASTM D6109-24

Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastic Lumber and Related Products

SIGNIFICANCE AND USE
5.1 Flexural properties determined by these test methods are especially useful for research and development, quality control, acceptance or rejection under specifications, and special purposes.  
5.2 Specimen depth, temperature, atmospheric conditions, and the difference in rate of straining specified in Test Methods A and B are capable of influencing flexural property results.
SCOPE
1.1 These test methods are suitable for determining the flexural properties for any solid or hollow manufactured plastic lumber product of square, rectangular, round, or other geometric cross section that shows viscoelastic behavior. The test specimens are whole “as manufactured” pieces without any altering or machining of surfaces beyond cutting to length. As such, this is a test method for evaluating the properties of plastic lumber as a product and not a material property test method. Flexural strength cannot be determined for those products that do not break or that do not fail in the extreme outer fiber.
Note 1: This test method was developed for application to plastic lumber materials, but it is generic enough that it would be equally applicable to other plastic composite materials, including wood-plastic composite materials.  
1.2 Test Method A, designed principally for products in the flat or “plank” position.  
1.3 Test Method B, designed principally for those products in the edgewise or “joist” position.  
1.4 Plastic lumber currently is produced using several different plastic manufacturing processes. These processes utilize a number of diverse plastic resin material systems that include fillers, fiber reinforcements, and other chemical additives. The test methods are applicable to plastic lumber products where the plastic resin is the continuous phase, regardless of its manufacturing process, type or weight percentage of plastic resin utilized, type or weight percentage of fillers utilized, type or weight percentage of reinforcements utilized, and type or weight percentage of other chemical additives.  
1.4.1 Alternative to a single resin material system, diverse and multiple combinations of both virgin and recycled thermoplastic material systems are permitted in the manufacture of plastic lumber products.  
1.4.2 Diverse types and combinations of inorganic and organic filler systems are permitted in the manufacturing of plastic lumber products. Inorganic fillers include such materials as talc, mica, silica, wollastonite, calcium carbonate, and so forth. Organic fillers include lignocellulosic materials made or derived from wood, wood flour, flax shive, rice hulls, wheat straw, and combinations thereof.  
1.4.3 Fiber reinforcements used in plastic lumber include manufactured materials such as fiberglass (chopped or continuous), carbon, aramid and other polymerics; or lignocellulosic-based fibers such as flax, jute, kenaf, and hemp.  
1.4.4 A wide variety of chemical additives are added to plastic lumber formulations to serve numerous different purposes. Examples include colorants, chemical foaming agents, ultraviolet stabilizers, flame retardants, lubricants, anti-static products, biocides, heat stabilizers, and coupling agents  
1.5 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
1.6 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.
Note 2: There is no known ISO equivalent to this standard.  
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of...

General Information

• Status: Published
• Publication Date: 31-Jan-2024
• ICS: 83.140.01 - Rubber and plastics products in general
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.20 - Plastic Lumber

Relations

• Replaces: ASTM D6109-19 - Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastic Lumber and Related Products
• Effective Date: 01-Feb-2024
• 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 E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM E456-13a(2022) - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Referred By: ASTM D7031-11(2019) - Standard Guide for Evaluating Mechanical and Physical Properties of Wood-Plastic Composite Products
• Effective Date: 01-Feb-2024
• Referred By: ASTM D6662-22 - Standard Specification for Polyolefin-Based Plastic Lumber Decking Boards
• Effective Date: 01-Feb-2024
• Referred By: ASTM D7568-23 - Standard Specification for Polyethylene-Based Structural-Grade Plastic Lumber for Outdoor Applications
• Effective Date: 01-Feb-2024
• Referred By: ASTM D7258-23 - Standard Specification for Polymeric Piles
• Effective Date: 01-Feb-2024
• Referred By: ASTM D7032-21 - Standard Specification for Establishing Performance Ratings for Wood-Plastic Composite and Plastic Lumber Deck Boards, Stair Treads, Guards, and Handrails
• Effective Date: 01-Feb-2024

Overview

ASTM D6109-24: Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastic Lumber and Related Products provides comprehensive methods to determine the flexural properties-such as strength and modulus of elasticity-of both solid and hollow plastic lumber and related products. Applicable to a range of cross-sectional shapes and composite material formulations, these test methods are essential for performance evaluation, quality control, product development, and specification compliance within the plastic lumber industry.

The standard is valuable because it assesses “as manufactured” plastic lumber products, focusing on actual product performance rather than laboratory material specimens. This ensures relevance and reliability for end-user applications and regulatory requirements.

Key Topics

• Flexural Properties Assessment: Specifies procedures for measuring the flexural strength, modulus of elasticity, secant modulus, and related properties using two main test methods:

  • Test Method A for the flat or “plank” position
  • Test Method B for the edgewise or “joist” position

• Specimen Integrity: Requires unmodified, full-size plastic lumber products, cut only to length, preserving as-manufactured surfaces for realistic product evaluation.

• Wide Material Applicability: Suitable for products made from various thermoplastic resin systems containing both virgin and recycled plastics, as well as a range of fillers (organic and inorganic) and fiber reinforcements (e.g., fiberglass, carbon, aramid, cellulose, hemp).

• Test Variables: Recognizes that results are affected by specimen geometry, conditioning, temperature, atmospheric humidity, and loading rates, which are clearly defined for consistency and repeatability.

• Comprehensive Reporting: Outlines required details for test reports, including identification, dimensions, testing conditions, method used, and calculated flexural properties.

Applications

• Product Development: Assists manufacturers in evaluating and comparing the flexural performance of new plastic lumber formulations and construction profiles underpinning research, innovation, and continuous improvement.

• Quality Control: Enables producers to monitor consistency in plastic lumber properties, ensuring products meet internal and marketplace standards for stiffness, strength, and performance.

• Specification Compliance: Facilitates determination of product acceptability under contractual or regulatory specifications, supporting procurement and construction quality assurance.

• Research and Industry Standards: Serves as a benchmark for academic and industry research, providing standardized flexural testing protocols applicable to a broad spectrum of composite plastic building materials, including wood-plastic composites.

• Sustainability: Supports the use of recycled plastics and filler materials, promoting environmentally responsible product development in the construction and landscaping industries.

Related Standards

• ASTM D618: Practice for Conditioning Plastics for Testing
• ASTM D883: Terminology Relating to Plastics
• ASTM D2915: Practice for Sampling and Data-Analysis for Structural Wood and Wood-Based Products
• ASTM D5947: Test Methods for Physical Dimensions of Solid Plastics Specimens
• ASTM E4: Practices for Force Calibration and Verification of Testing Machines
• ASTM E691: Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• ASTM E2935: Practice for Evaluating Equivalence of Two Testing Processes

Note: There is currently no ISO equivalent to ASTM D6109.

---

Keywords: ASTM D6109, flexural properties, plastic lumber, composite plastics, flexural test methods, modulus of elasticity, recycled plastics, quality control, construction materials, structural testing, plastic composites, wood-plastic composites.

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: D6109 − 24
Standard Test Methods for
Flexural Properties of Unreinforced and Reinforced Plastic
Lumber and Related Products
This standard is issued under the fixed designation D6109; 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.
1. Scope* 1.4.2 Diverse types and combinations of inorganic and
organic filler systems are permitted in the manufacturing of
1.1 These test methods are suitable for determining the
plastic lumber products. Inorganic fillers include such materi-
flexural properties for any solid or hollow manufactured plastic
als as talc, mica, silica, wollastonite, calcium carbonate, and so
lumber product of square, rectangular, round, or other geomet-
forth. Organic fillers include lignocellulosic materials made or
ric cross section that shows viscoelastic behavior. The test
derived from wood, wood flour, flax shive, rice hulls, wheat
specimens are whole “as manufactured” pieces without any
straw, and combinations thereof.
altering or machining of surfaces beyond cutting to length. As
1.4.3 Fiber reinforcements used in plastic lumber include
such, this is a test method for evaluating the properties of
manufactured materials such as fiberglass (chopped or
plastic lumber as a product and not a material property test
continuous), carbon, aramid and other polymerics; or
method. Flexural strength cannot be determined for those
lignocellulosic-based fibers such as flax, jute, kenaf, and hemp.
products that do not break or that do not fail in the extreme
1.4.4 A wide variety of chemical additives are added to
outer fiber.
plastic lumber formulations to serve numerous different pur-
NOTE 1—This test method was developed for application to plastic
poses. Examples include colorants, chemical foaming agents,
lumber materials, but it is generic enough that it would be equally
ultraviolet stabilizers, flame retardants, lubricants, anti-static
applicable to other plastic composite materials, including wood-plastic
products, biocides, heat stabilizers, and coupling agents
composite materials.
1.5 The values stated in inch-pound units are to be regarded
1.2 Test Method A, designed principally for products in the
as standard. The values given in parentheses are mathematical
flat or “plank” position.
conversions to SI units that are provided for information only
1.3 Test Method B, designed principally for those products
and are not considered standard.
in the edgewise or “joist” position.
1.6 This standard does not purport to address all of the
1.4 Plastic lumber currently is produced using several dif-
safety concerns, if any, associated with its use. It is the
ferent plastic manufacturing processes. These processes utilize responsibility of the user of this standard to establish appro-
a number of diverse plastic resin material systems that include
priate safety, health, and environmental practices and deter-
fillers, fiber reinforcements, and other chemical additives. The mine the applicability of regulatory limitations prior to use.
test methods are applicable to plastic lumber products where
NOTE 2—There is no known ISO equivalent to this standard.
the plastic resin is the continuous phase, regardless of its
1.7 This international standard was developed in accor-
manufacturing process, type or weight percentage of plastic
dance with internationally recognized principles on standard-
resin utilized, type or weight percentage of fillers utilized, type
ization established in the Decision on Principles for the
or weight percentage of reinforcements utilized, and type or
Development of International Standards, Guides and Recom-
weight percentage of other chemical additives.
mendations issued by the World Trade Organization Technical
1.4.1 Alternative to a single resin material system, diverse
Barriers to Trade (TBT) Committee.
and multiple combinations of both virgin and recycled thermo-
plastic material systems are permitted in the manufacture of
2. Referenced Documents
plastic lumber products.
2.1 ASTM Standards:
D618 Practice for Conditioning Plastics for Testing
These test methods are under the jurisdiction of ASTM Committee D20 on
Plastics and are the direct responsibility of Subcommittee D20.20 on Plastic Lumber
(Section D20.20.01). For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Feb. 1, 2024. Published February 2024. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1997. Last previous edition approved in 2019 as D6109 – 19. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D6109-24. 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
D6109 − 24
D883 Terminology Relating to Plastics
D2915 Practice for Sampling and Data-Analysis for Struc-
tural Wood and Wood-Based Products
D5033 Guide for Development of ASTM Standards Relating
to Recycling and Use of Recycled Plastics (Withdrawn
2007)
D5947 Test Methods for Physical Dimensions of Solid
Plastics Specimens
E4 Practices for Force Calibration and Verification of Test-
ing Machines
E456 Terminology Relating to Quality and Statistics
FIG. 1 Loading Diagram
E691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
E2935 Practice for Evaluating Equivalence of Two Testing
5. Significance and Use
Processes
5.1 Flexural properties determined by these test methods are
especially useful for research and development, quality control,
3. Terminology
acceptance or rejection under specifications, and special pur-
3.1 Definitions:
poses.
3.1.1 Definitions of terms applying to these test methods
5.2 Specimen depth, temperature, atmospheric conditions,
appear in Terminology D883 and Guide D5033. For terms
and the difference in rate of straining specified in Test Methods
relating to precision and bias and associated issues, the terms
A and B are capable of influencing flexural property results.
used in this test method are in accordance with the definitions
in Terminology E456.
6. Apparatus
3.1.2 plastic lumber, n—a manufactured product made pri-
6.1 Testing Machine—A properly calibrated testing machine
marily from plastic materials (filled or unfilled), typically used
that is capable of operation at a constant rate of motion of the
as a building material for purposes similar to those of tradi-
movable head and has the accuracy of 61 % of maximum load
tional lumber, which is usually rectangular in cross-section.
expected to be measured. It shall be equipped with a deflection
(Terminology D883)
measuring device. The stiffness of the testing machine shall be
3.1.2.1 Discussion—Plastic lumber is typically supplied in
such that the total elastic deformation of the system does not
sizes similar to those of traditional lumber board, timber and
exceed 1 % of the total deflection of the test specimen during
dimension lumber; however the tolerances for plastic lumber
testing, or appropriate corrections shall be made. The load
and for traditional lumber are not necessarily the same.
indication mechanism shall be essentially free from inertial lag
(Terminology D883)
at the crosshead rate used. The accuracy of the testing machine
3.1.3 resin, n—solid or pseudosolid organic material often
shall be verified in accordance with Practice E4.
of high molecular weight, that exhibits a tendency to flow
6.2 Loading Noses and Supports—The loading noses and
when subjected to stress, usually has a softening or melting
supports shall have cylindrical surfaces. In order to avoid
range, and usually fractures conchoidally. (Terminology D883)
excessive indentation, of the failure due to stress concentration
3.1.3.1 Discussion—In a broad sense, the term is used to
directly under the loading noses, the radius or noses and
designate any polymer that is a basic material for plastics.
supports shall be at least 0.5 in. (12.7 mm) for all specimens.
If significant indentation or compressive failure occurs or is
4. Summary of Test Method
observed at the point where the loading noses contact the
4.1 A specimen of rectangular cross section is tested in specimen, then the radius of the loading noses shall be
flexure as a beam either in a flat, or “plank,” mode (Method A) increased up to 1.5 times the specimen depth (see Fig. 2).
or edgewise, or “joist,” mode (Method B) as follows:
NOTE 3—Test data have shown that the loading noses and support
4.1.1 The beam rests on two supports and is loaded at two
dimensions are capable of influencing the flexural modulus values.
points (by means of two loading noses), each an equal distance
Dimensions of loading noses and supports must be specified in the test
report.
from the adjacent support point. The distance between the
loading noses (that is, the load span) is one-third of the support
7. Test Specimens
span (see Fig. 1; use of other distances for the load spans are
7.1 The specimens shall be full size as manufactured, then
addressed in Appendix X1).
cut to length for testing. The original outside surfaces shall be
4.1.2 The specimen is deflected until rupture occurs in the
unaltered. The support span to depth ratio shall be nominally
outer fibers or until a maximum outer fiber strain of 3 % is
16:1.
reached, whichever occurs first.
7.2 For Test Method A, flatwise or “plank” tests, the depth
of the specimen shall be the thickness, or smaller dimension, of
the product. For Test Method B, edgewise or “joist” tests the
The last approved version of this historical standard is referenced on
www.astm.org. width becomes the smaller dimension and depth the larger. For
D6109 − 24
10.1.4 Calculate the rate of crosshead motion as follows,
and set the machine as near as possible to that calculated rate
for a load span of one-third of the support span:
R 5 0.185ZL /d (1)
where:
R = rate of crosshead motion, in./min (mm/min),
L = support span, in. (mm),
d = depth of the beam, in. (mm), and
Z = rate of straining of the outer fibers, in./in./min (mm/mm/
min). Z shall be equal to 0.01.
In no case shall the actual crosshead rate differ from that
calculated from Eq 1, by more than 610 %.
10.1.5 Align the loading noses and supports so that the axes
of the cylindrical surfaces are parallel and the load span is
one-third of the support span. Check parallelism by means of a
plate containing parallel grooves into which the loading noses
and supports will fit when properly aligned. Center the speci-
NOTE 1—(A) = minimum radius = 12.7 mm; (B) = maximum radius =
1.5 times the specimen depth. men on the supports, with the long axis of the specimen
FIG. 2 Four Point Loading and Support Noses at Minimum and
perpendicular to the loading noses and supports. The loading
Maximum Radius
nose assembly shall be of the type which will not rotate.
10.1.6 Apply the load to the specimen at the specified
crosshead rate, and take simultaneous load-deflection data.
all tests, the support span shall be 16 (tolerance +4 and −2)
Measure deflection at the common center of the spans. Perform
times the depth of the beam. The specimen shall be long
the necessary toe compensation (see Annex A1) to correct for
enough to allow for overhanging on each end of at least 10 %
seating and indentation of the specimen and deflections in the
of the support span. Overhang shall be sufficient to prevent the
machine. Stress-strain curves shall be plotted to determine the
specimen from slipping through the supports.
flexural yield strength, modulus of elasticity and secant modu-
lus at 1 % strain.
8. Number of Test Specimens
10.1.7 If no break has occurred in a specimen by the time
8.1 Five specimens shall be tested for each sample.
the maximum strain in the outer fibers has reached 0.03 in./in.
(mm/mm), discontinue the test (see Note 4 and Note 5). The
9. Conditioning
deflection at which this strain occurs shall be calculated by
letting r equal 0.03 in./in. (mm/mm) as follows for a load span
9.1 Specimen Conditioning—Condition the test specimens
of one-third of the support span:
at 73.4 6 3.6°F (23 6 2°C) and 50 6 5 % relative humidity for
not less than 40 h prior to testing in accordance with Procedure 2
D 5 0.21 rL /d (2)
A of Practice D618 for those tests where conditioning is
where:
required. In cases of disagreement, the tolerances shall be
D = midspan deflection, in. (mm),
61.8°F (61°C) and 62 % relative humidity.
r = strain, in./in. (mm/mm), and
9.2 Test Conditions—Conduct the tests in the Standard
d = depth of the beam, in. (mm).
Laboratory Atmosphere of 73.4 6 3.6°F (23 6 2°C) and 50 6
NOTE 4—For some products the increase in strain rate provided under
5 % relative humidity, unless otherwise specified in the refer-
Test Method B is capable of inducing the specimen to yield or rupture, or
enced test methods or in these test methods. In cases of both, within the required 3 % strain limit.
NOTE 5—If the product does not fracture at a maximum of 3 % strain,
disagreement, the tolerances shall be 61.8°F (61°C) and
these test methods do not reveal true flexural str
...

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: D6109 − 19 D6109 − 24
Standard Test Methods for
Flexural Properties of Unreinforced and Reinforced Plastic
Lumber and Related Products
This standard is issued under the fixed designation D6109; 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.
1. Scope*
1.1 These test methods are suitable for determining the flexural properties for any solid or hollow manufactured plastic lumber
product of square, rectangular, round, or other geometric cross section that shows viscoelastic behavior. The test specimens are
whole “as manufactured” pieces without any altering or machining of surfaces beyond cutting to length. As such, this is a test
method for evaluating the properties of plastic lumber as a product and not a material property test method. Flexural strength
cannot be determined for those products that do not break or that do not fail in the extreme outer fiber.
NOTE 1—This test method was developed for application to plastic lumber materials, but it is generic enough that it would be equally applicable to other
plastic composite materials, including wood-plastic composite materials.
1.2 Test Method A, designed principally for products in the flat or “plank” position.
1.3 Test Method B, designed principally for those products in the edgewise or “joist” position.
1.4 Plastic lumber currently is produced using several different plastic manufacturing processes. These processes utilize a number
of diverse plastic resin material systems that include fillers, fiber reinforcements, and other chemical additives. The test methods
are applicable to plastic lumber products where the plastic resin is the continuous phase, regardless of its manufacturing process,
type or weight percentage of plastic resin utilized, type or weight percentage of fillers utilized, type or weight percentage of
reinforcements utilized, and type or weight percentage of other chemical additives.
1.4.1 Alternative to a single resin material system, diverse and multiple combinations of both virgin and recycled thermoplastic
material systems are permitted in the manufacture of plastic lumber products.
1.4.2 Diverse types and combinations of inorganic and organic filler systems are permitted in the manufacturing of plastic lumber
products. Inorganic fillers include such materials as talc, mica, silica, wollastonite, calcium carbonate, and so forth. Organic fillers
include lignocellulosic materials made or derived from wood, wood flour, flax shive, rice hulls, wheat straw, and combinations
thereof.
1.4.3 Fiber reinforcements used in plastic lumber include manufactured materials such as fiberglass (chopped or continuous),
carbon, aramid and other polymerics; or lignocellulosic-based fibers such as flax, jute, kenaf, and hemp.
1.4.4 A wide variety of chemical additives are added to plastic lumber formulations to serve numerous different purposes.
These test methods are under the jurisdiction of ASTM Committee D20 on Plastics and are the direct responsibility of Subcommittee D20.20 on Plastic Lumber (Section
D20.20.01).
Current edition approved April 1, 2019Feb. 1, 2024. Published May 2019February 2024. Originally approved in 1997. Last previous edition approved in 20132019 as
D6109 - 13.D6109 – 19. DOI: 10.1520/D6109-19.10.1520/D6109-24.
*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
D6109 − 24
Examples include colorants, chemical foaming agents, ultraviolet stabilizers, flame retardants, lubricants, anti-static products,
biocides, heat stabilizers, and coupling agents
1.5 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
1.6 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.
NOTE 2—There is no known ISO equivalent to this standard.
1.7 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:
D618 Practice for Conditioning Plastics for Testing
D883 Terminology Relating to Plastics
D2915 Practice for Sampling and Data-Analysis for Structural Wood and Wood-Based Products
D5033 Guide for Development of ASTM Standards Relating to Recycling and Use of Recycled Plastics (Withdrawn 2007)
D5947 Test Methods for Physical Dimensions of Solid Plastics Specimens
E4 Practices for Force Calibration and Verification of Testing Machines
E456 Terminology Relating to Quality and Statistics
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E2935 Practice for Evaluating Equivalence of Two Testing Processes
3. Terminology
3.1 Definitions:
3.1.1 Definitions of terms applying to these test methods appear in Terminology D883 and Guide D5033. For terms relating to
precision and bias and associated issues, the terms used in this test method are in accordance with the definitions in Terminology
E456.
3.1.2 plastic lumber, n—a manufactured product made primarily from plastic materials (filled or unfilled), typically used as a
building material for purposes similar to those of traditional lumber, which is usually rectangular in cross-section. (Terminology
D883)
3.1.2.1 Discussion—
Plastic lumber is typically supplied in sizes similar to those of traditional lumber board, timber and dimension lumber; however
the tolerances for plastic lumber and for traditional lumber are not necessarily the same. (Terminology D883)
3.1.3 resin, n—solid or pseudosolid organic material often of high molecular weight, that exhibits a tendency to flow when
subjected to stress, usually has a softening or melting range, and usually fractures conchoidally. (Terminology D883)
3.1.3.1 Discussion—In a broad sense, the term is used to designate any polymer that is a basic material for plastics.
4. Summary of Test Method
4.1 A specimen of rectangular cross section is tested in flexure as a beam either in a flat, or “plank,” mode (Method A) or edgewise,
or “joist,” mode (Method B) as follows:
4.1.1 The beam rests on two supports and is loaded at two points (by means of two loading noses), each an equal distance from
the adjacent support point. The distance between the loading noses (that is, the load span) is one-third of the support span (see Fig.
1; use of other distances for the load spans are addressed in Appendix X1).
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.
The last approved version of this historical standard is referenced on www.astm.org.
D6109 − 24
FIG. 1 Loading Diagram
4.1.2 The specimen is deflected until rupture occurs in the outer fibers or until a maximum outer fiber strain of 3 % is reached,
whichever occurs first.
5. Significance and Use
5.1 Flexural properties determined by these test methods are especially useful for research and development, quality control,
acceptance or rejection under specifications, and special purposes.
5.2 Specimen depth, temperature, atmospheric conditions, and the difference in rate of straining specified in Test Methods A and
B are capable of influencing flexural property results.
6. Apparatus
6.1 Testing Machine—A properly calibrated testing machine that is capable of operation at a constant rate of motion of the
movable head and has the accuracy of 61 % of maximum load expected to be measured. It shall be equipped with a deflection
measuring device. The stiffness of the testing machine shall be such that the total elastic deformation of the system does not exceed
1 % of the total deflection of the test specimen during testing, or appropriate corrections shall be made. The load indication
mechanism shall be essentially free from inertial lag at the crosshead rate used. The accuracy of the testing machine shall be
verified in accordance with Practice E4.
6.2 Loading Noses and Supports—The loading noses and supports shall have cylindrical surfaces. In order to avoid excessive
indentation, of the failure due to stress concentration directly under the loading noses, the radius or noses and supports shall be
at least 0.5 in. (12.7 mm) for all specimens. If significant indentation or compressive failure occurs or is observed at the point where
the loading noses contact the specimen, then the radius of the loading noses shall be increased up to 1.5 times the specimen depth
(see Fig. 2).
NOTE 3—Test data have shown that the loading noses and support dimensions are capable of influencing the flexural modulus values. Dimensions of
loading noses and supports must be specified in the test report.
7. Test Specimens
7.1 The specimens shall be full size as manufactured, then cut to length for testing. The original outside surfaces shall be unaltered.
The support span to depth ratio shall be nominally 16:1.
7.2 For Test Method A, flatwise or “plank” tests, the depth of the specimen shall be the thickness, or smaller dimension, of the
product. For Test Method B, edgewise or “joist” tests the width becomes the smaller dimension and depth the larger. For all tests,
the support span shall be 16 (tolerance +4 and −2) times the depth of the beam. The specimen shall be long enough to allow for
overhanging on each end of at least 10 % of the support span. Overhang shall be sufficient to prevent the specimen from slipping
through the supports.
8. Number of Test Specimens
8.1 Five specimens shall be tested for each sample.
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NOTE 1—(A) = minimum radius = 12.7 mm; (B) = maximum radius = 1.5 times the specimen depth.
FIG. 2 Four Point Loading and Support Noses at Minimum and Maximum Radius
9. Conditioning
9.1 Specimen Conditioning—Condition the test specimens at 73.4 6 3.6°F (23 6 2°C) and 50 6 5 % relative humidity for not
less than 40 h prior to testing in accordance with Procedure A of Practice D618 for those tests where conditioning is required. In
cases of disagreement, the tolerances shall be 61.8°F (61°C) and 62 % relative humidity.
9.2 Test Conditions—Conduct the tests in the Standard Laboratory Atmosphere of 73.4 6 3.6°F (23 6 2°C) and 50 6 5 % relative
humidity, unless otherwise specified in the referenced test methods or in these test methods. In cases of disagreement, the
tolerances shall be 61.8°F (61°C) and 62 % relative humidity.
10. Procedure
10.1 Test Method A:
10.1.1 Flatwise or “plank” Testing:
10.1.2 Use an untested specimen for each measurement. Measure the width of the specimen to a precision of 1 % of the measured
dimensions at several points along the product’s length and record the average value. Measure the depth of the specimen at several
points and record the average value (see Test Methods D5947 for additional information).
10.1.3 Determine the support span to be used as described in Section 7 and set the support span to within 1 % of the determined
value.
10.1.4 Calculate the rate of crosshead motion as follows, and set the machine as near as possible to that calculated rate for a load
span of one-third of the support span:
R 5 0.185ZL /d (1)
where:
R = rate of crosshead motion, in./min (mm/min),
L = support span, in. (mm),
d = depth of the beam, in. (mm), and
Z = rate of straining of the outer fibers, in./in./min (mm/mm/min). Z shall be equal to 0.01.
In no case shall the actual crosshead rate differ from that calculated from Eq 1, by more than 610 %.
10.1.5 Align the loading noses and supports so that the axes of the cylindrical surfaces are parallel and the load span is one-third
of the support span. Check parallelism by means of a plate containing parallel grooves into which the loading noses and supports
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will fit when properly aligned. Center the specimen on the supports, with the long axis of the specimen perpendicular to the loading
noses and supports. The loading nose assembly shall be of the type which will not rotate.
10.1.6 Apply the load to the specimen at the specified crosshead rate, and take simultaneous load-deflection data. Measure
deflection at the common center of the spans. Perform the necessary toe compensation (see Annex A1) to correct for seating and
indentation of the specimen and deflections in the machine. Stress-strain curves shall be plotted to determine the flexural yield
strength, modulus of elasticity and secant modulus at 1 % strain.
10.1.7 If no break has occurred in a specimen by the time the maximum strain in the outer fibers has reached 0.03 in./in. (mm/mm),
discontinue the test (see Note 34 and Note 45). The deflection at which this strain occurs shall be calcu
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