Astm D638-14 Pdf Free Download

This standard is issued under the fixed designation D638; 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.

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Designation: D638 −14

Standard Test Method for

Tensile Properties of Plastics

This standard is issued under the ﬁxed designation D638; 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 This test method covers the determination of the tensile

properties of unreinforced and reinforced plastics in the form

of standard dumbbell-shaped test specimens when tested under

deﬁned conditions of pretreatment, temperature, humidity, and

testing machine speed.

1.2 This test method is applicable for testing materials of

any thickness up to 14 mm (0.55 in.). However, for testing

specimens in the form of thin sheeting, including ﬁlm less than

1.0 mm (0.04 in.) in thickness, ASTM standard D882 is the

preferred test method. Materials with a thickness greater than

14 mm (0.55 in.) shall be reduced by machining.

1.3 This test method includes the option of determining

Poisson's ratio at room temperature.

NOTE 1—This standard and ISO 527-1 address the same subject matter,

but differ in technical content.

NOTE 2—This test method is not intended to cover precise physical

procedures. It is recognized that the constant rate of crosshead movement

type of test leaves much to be desired from a theoretical standpoint, that

wide differences may exist between rate of crosshead movement and rate

of strain between gage marks on the specimen, and that the testing speeds

speciﬁed disguise important effects characteristic of materials in the

plastic state. Further, it is realized that variations in the thicknesses of test

specimens, which are permitted by these procedures, produce variations in

the surface-volume ratios of such specimens, and that these variations may

inﬂuence the test results. Hence, where directly comparable results are

desired, all samples should be of equal thickness. Special additional tests

should be used where more precise physical data are needed.

NOTE 3—This test method may be used for testing phenolic molded

resin or laminated materials. However, where these materials are used as

electrical insulation, such materials should be tested in accordance with

Test Methods D229 and Test Method D651.

NOTE 4—For tensile properties of resin-matrix composites reinforced

with oriented continuous or discontinuous high modulus >20-GPa

(>3.0 × 10

-psi) ﬁbers, tests shall be made in accordance with Test

Method D3039/D3039M.

1.4 Test data obtained by this test method have been found

to be useful in engineering design. However, it is important to

consider the precautions and limitations of this method found

in Note 2 and Section 4 before considering these data for

engineering design.

1.5 The values stated in SI units are to be regarded as

standard. The values given in parentheses are for information

only.

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 appro-

priate safety and health practices and determine the applica-

bility of regulatory limitations prior to use.

2. Referenced Documents

2.1 ASTM Standards:

D229 Test Methods for Rigid Sheet and Plate Materials

Used for Electrical Insulation

D412 Test Methods for Vulcanized Rubber and Thermoplas-

tic Elastomers—Tension

D618 Practice for Conditioning Plastics for Testing

D651 Test Method for Test for Tensile Strength of Molded

Electrical Insulating Materials (Withdrawn 1989)

D882 Test Method for Tensile Properties of Thin Plastic

Sheeting

D883 Terminology Relating to Plastics

D1822 Test Method for Tensile-Impact Energy to Break

Plastics and Electrical Insulating Materials

D3039/D3039M Test Method for Tensile Properties of Poly-

mer Matrix Composite Materials

D4000 Classiﬁcation System for Specifying Plastic Materi-

als

D4066 Classiﬁcation System for Nylon Injection and Extru-

sion Materials (PA)

D5947 Test Methods for Physical Dimensions of Solid

Plastics Specimens

E4 Practices for Force Veriﬁcation of Testing Machines

This test method is under the jurisdiction of ASTM Committee D20 on Plastics

and is the direct responsibility of Subcommittee D20.10 on Mechanical Properties.

Current edition approved Dec. 15, 2014. Published March 2015. Originally

approved in 1941. Last previous edition approved in 2010 as D638 - 10. DOI:

10.1520/D0638-14.

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.

The last approved version of this historical standard is referenced on

www.astm.org.

*A Summary of Changes section appears at the end of this standard

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.

E83 Practice for Veriﬁcation and Classiﬁcation of Exten-

someter Systems

E132 Test Method for Poisson's Ratio at Room Temperature

E691 Practice for Conducting an Interlaboratory Study to

Determine the Precision of a Test Method

2.2 ISO Standard:

ISO 527-1 Determination of Tensile Properties

3. Terminology

3.1 Deﬁnitions— Deﬁnitions of terms applying to this test

method appear in Terminology D883 and Annex A2.

4. Signiﬁcance and Use

4.1 This test method is designed to produce tensile property

data for the control and speciﬁcation of plastic materials. These

data are also useful for qualitative characterization and for

research and development.

4.2 Some material speciﬁcations that require the use of this

test method, but with some procedural modiﬁcations that take

precedence when adhering to the speciﬁcation. Therefore, it is

advisable to refer to that material speciﬁcation before using this

test method. Table 1 in Classiﬁcation D4000 lists the ASTM

materials standards that currently exist.

4.3 Tensile properties are known to vary with specimen

preparation and with speed and environment of testing.

Consequently, where precise comparative results are desired,

these factors must be carefully controlled.

4.4 It is realized that a material cannot be tested without also

testing the method of preparation of that material. Hence, when

comparative tests of materials per se are desired, exercise great

care to ensure that all samples are prepared in exactly the same

way, unless the test is to include the effects of sample

preparation. Similarly, for referee purposes or comparisons

within any given series of specimens, care shall be taken to

secure the maximum degree of uniformity in details of

preparation, treatment, and handling.

4.5 Tensile properties provide useful data for plastics engi-

neering design purposes. However, because of the high degree

of sensitivity exhibited by many plastics to rate of straining and

environmental conditions, data obtained by this test method

cannot be considered valid for applications involving load-time

scales or environments widely different from those of this test

method. In cases of such dissimilarity, no reliable estimation of

the limit of usefulness can be made for most plastics. This

sensitivity to rate of straining and environment necessitates

testing over a broad load-time scale (including impact and

creep) and range of environmental conditions if tensile prop-

erties are to suffice for engineering design purposes.

NOTE 5—Since the existence of a true elastic limit in plastics (as in

many other organic materials and in many metals) is debatable, the

propriety of applying the term "elastic modulus" in its quoted, generally

accepted deﬁnition to describe the "stiffness" or "rigidity" of a plastic has

been seriously questioned. The exact stress-strain characteristics of plastic

materials are highly dependent on such factors as rate of application of

stress, temperature, previous history of specimen, etc. However, stress-

strain curves for plastics, determined as described in this test method,

almost always show a linear region at low stresses, and a straight line

drawn tangent to this portion of the curve permits calculation of an elastic

modulus of the usually deﬁned type. Such a constant is useful if its

arbitrary nature and dependence on time, temperature, and similar factors

are realized.

5. Apparatus

5.1 Testing Machine—A testing machine of the constant-

rate-of-crosshead-movement type and comprising essentially

the following:

5.1.1 Fixed Member—A ﬁxed or essentially stationary

member carrying one grip.

5.1.2 Movable Member—A movable member carrying a

second grip.

5.1.3 Grips— Grips for holding the test specimen between

the ﬁxed member and the movable member of the testing

machine can be either the ﬁxed or self-aligning type.

5.1.3.1 Fixed grips are rigidly attached to the ﬁxed and

movable members of the testing machine. When this type of

grip is used take extreme care to ensure that the test specimen

is inserted and clamped so that the long axis of the test

specimen coincides with the direction of pull through the

center line of the grip assembly.

5.1.3.2 Self-aligning grips are attached to the ﬁxed and

movable members of the testing machine in such a manner that

they will move freely into alignment as soon as any load is

applied so that the long axis of the test specimen will coincide

with the direction of the applied pull through the center line of

the grip assembly. Align the specimens as perfectly as possible

with the direction of pull so that no rotary motion that may

induce slippage will occur in the grips; there is a limit to the

amount of misalignment self-aligning grips will accommodate.

5.1.3.3 The test specimen shall be held in such a way that

slippage relative to the grips is prevented insofar as possible.

Grip surfaces that are deeply scored or serrated with a pattern

similar to those of a coarse single-cut ﬁle, serrations about 2.4

mm (0.09 in.) apart and about 1.6 mm (0.06 in.) deep, have

been found satisfactory for most thermoplastics. Finer serra-

tions have been found to be more satisfactory for harder

plastics, such as the thermosetting materials. It is important that

the serrations be kept clean and sharp. Should breaking in the

grips occur, even when deep serrations or abraded specimen

surfaces are used, other techniques shall be used. Other

techniques that have been found useful, particularly with

smooth-faced grips, are abrading that portion of the surface of

the specimen that will be in the grips, and interposing thin

pieces of abrasive cloth, abrasive paper, or plastic, or rubber-

coated fabric, commonly called hospital sheeting, between the

specimen and the grip surface. No. 80 double-sided abrasive

paper has been found effective in many cases. An open-mesh

fabric, in which the threads are coated with abrasive, has also

been effective. Reducing the cross-sectional area of the speci-

men may also be effective. The use of special types of grips is

sometimes necessary to eliminate slippage and breakage in the

grips.

5.1.4 Drive Mechanism—A drive mechanism for imparting

a uniform, controlled velocity to the movable member with

Available from American National Standards Institute (ANSI), 25 W. 43rd St.,

4th Floor, New York, NY 10036, http://www.ansi.org.

D638 − 14

respect to the stationary member. This velocity is to be

regulated as speciﬁed in Section 8.

5.1.5 Load Indicator— A suitable load-indicating mecha-

nism capable of showing the total tensile load carried by the

test specimen when held by the grips. This mechanism shall be

essentially free of inertia lag at the speciﬁed rate of testing and

shall indicate the load with an accuracy of 61 % of the

indicated value, or better. The accuracy of the testing machine

shall be veriﬁed in accordance with Practices E4.

NOTE 6—Experience has shown that many testing machines now in use

are incapable of maintaining accuracy for as long as the periods between

inspection recommended in Practices E4 . Hence, it is recommended that

each machine be studied individually and veriﬁed as often as may be

found necessary. It frequently will be necessary to perform this function

daily.

5.1.6 The ﬁxed member, movable member, drive

mechanism, and grips shall be constructed of such materials

and in such proportions that the total elastic longitudinal strain

of the system constituted by these parts does not exceed 1 % of

the total longitudinal strain between the two gage marks on the

test specimen at any time during the test and at any load up to

the rated capacity of the machine.

5.1.7 Crosshead Extension Indicator— A suitable extension

indicating mechanism capable of showing the amount of

change in the separation of the grips, that is, crosshead

movement. This mechanism shall be essentially free of inertial

lag at the speciﬁed rate of testing and shall indicate the

crosshead movement with an accuracy of 610 % of the

indicated value.

5.2 Extension Indicator (extensometer)— A suitable instru-

ment shall be used for determining the distance between two

designated points within the gauge length of the test specimen

as the specimen is stretched. For referee purposes, the exten-

someter must be set at the full gage length of the specimen, as

shown in Fig. 1. It is desirable, but not essential, that this

instrument automatically record this distance, or any change in

it, as a function of the load on the test specimen or of the

elapsed time from the start of the test, or both. If only the latter

is obtained, load-time data must also be taken. This instrument

shall be essentially free of inertia at the speciﬁed speed of

testing. Extensometers shall be classiﬁed and their calibration

periodically veriﬁed in accordance with Practice E83.

5.2.1 Modulus-of-Elasticity Measurements—For modulus-

of-elasticity measurements, an extensometer with a maximum

strain error of 0.0002 mm/mm (in./in.) that automatically and

continuously records shall be used. An extensometer classiﬁed

by Practice E83 as fulﬁlling the requirements of a B-2

classiﬁcation within the range of use for modulus measure-

ments meets this requirement.

5.2.2 Low-Extension Measurements—For elongation-at-

yield and low-extension measurements (nominally 20 % or

less), the same above extensometer, attenuated to 20 %

extension, is acceptable. In any case, the extensometer system

must meet at least Class C (Practice E83 ) requirements, which

include a ﬁxed strain error of 0.001 strain or 6 1.0 % of the

indicated strain, whichever is greater.

5.2.3 High-Extension Measurements—For making measure-

ments at elongations greater than 20 %, measuring techniques

with error no greater than 610 % of the measured value are

acceptable.

5.3 Micrometers— Apparatus for measuring the width and

thickness of the test specimen shall comply with the require-

ments of Test Method D5947.

6. Test Specimens

6.1 Sheet, Plate, and Molded Plastics:

6.1.1 Rigid and Semirigid Plastics—The test specimen shall

conform to the dimensions shown in Fig. 1. The Type I

specimen is the preferred specimen and shall be used where

sufficient material having a thickness of 7 mm (0.28 in.) or less

is available. The Type II specimen is recommended when a

material does not break in the narrow section with the preferred

Type I specimen. The Type V specimen shall be used where

only limited material having a thickness of 4 mm (0.16 in.) or

less is available for evaluation, or where a large number of

specimens are to be exposed in a limited space (thermal and

environmental stability tests, etc.). The Type IV specimen is

generally used when direct comparisons are required between

materials in different rigidity cases (that is, nonrigid and

semirigid). The Type III specimen must be used for all

materials with a thickness of greater than 7 mm (0.28 in.) but

not more than 14 mm (0.55 in.).

6.1.2 Nonrigid Plastics—The test specimen shall conform

to the dimensions shown in Fig. 1. The Type IV specimen shall

be used for testing nonrigid plastics with a thickness of 4 mm

(0.16 in.) or less. The Type III specimen must be used for all

materials with a thickness greater than 7 mm (0.28 in.) but not

more than 14 mm (0.55 in.).

6.1.3 Reinforced Composites—The test specimen for rein-

forced composites, including highly orthotropic laminates,

shall conform to the dimensions of the Type I specimen shown

in Fig. 1.

6.1.4 Preparation— Methods of preparing test specimens

include injection molding, machining operations, or die

cutting, from materials in sheet, plate, slab, or similar form.

Materials thicker than 14 mm (0.55 in.) shall be machined to 14

mm (0.55 in.) for use as Type III specimens.

NOTE 7—Test results have shown that for some materials such as glass

cloth, SMC, and BMC laminates, other specimen types should be

considered to ensure breakage within the gage length of the specimen, as

mandated by 7.3.

NOTE 8—When preparing specimens from certain composite laminates

such as woven roving, or glass cloth, exercise care in cutting the

specimens parallel to the reinforcement. The reinforcement will be

signiﬁcantly weakened by cutting on a bias, resulting in lower laminate

properties, unless testing of specimens in a direction other than parallel

with the reinforcement constitutes a variable being studied.

NOTE 9—Specimens prepared by injection molding may have different

tensile properties than specimens prepared by machining or die-cutting

because of the orientation induced. This effect may be more pronounced

in specimens with narrow sections.

6.2 Rigid Tubes—The test specimen for rigid tubes shall be

as shown in Fig. 2. The length, L , shall be as shown in the table

in Fig. 2. A groove shall be machined around the outside of the

specimen at the center of its length so that the wall section after

D638 − 14

Specimen Dimensions for Thickness, T , mm (in.)

Dimensions (see drawings) 7 (0.28) or under Over 7 to 14 (0.28 to 0.55), incl 4 (0.16) or under Tolerances

Type I Type II Type III Type IV

Type V

C,D

W—Width of narrow section

E,F

13 (0.50) 6 (0.25) 19 (0.75) 6 (0.25) 3.18 (0.125) ±0.5 (±0.02)

B,C

L—Length of narrow section 57 (2.25) 57 (2.25) 57 (2.25) 33 (1.30) 9.53 (0.375) ±0.5 (±0.02)

WO—Width overall, min

19 (0.75) 19 (0.75) 29 (1.13) 19 (0.75) ... + 6.4 ( + 0.25)

WO—Width overall, min

... ... ... ... 9.53 (0.375) + 3.18 ( + 0.125)

LO—Length overall, min

165 (6.5) 183 (7.2) 246 (9.7) 115 (4.5) 63.5 (2.5) no max (no max)

G—Gage length

50 (2.00) 50 (2.00) 50 (2.00) ... 7.62 (0.300) ±0.25 (±0.010)

G—Gage length

... ... ... 25 (1.00) ... ±0.13 (±0.005)

D—Distance between grips 115 (4.5) 135 (5.3) 115 (4.5) 65 (2.5)

25.4 (1.0) ±5 (±0.2)

R—Radius of ﬁllet 76 (3.00) 76 (3.00) 76 (3.00) 14 (0.56) 12.7 (0.5) ±1 (±0.04)

RO—Outer radius (Type IV) ... ... ... 25 (1.00) ... ±1 (±0.04)

Thickness, T , shall be 3.2± 0.4 mm (0.13 ± 0.02 in.) for all types of molded specimens, and for other Types I and II specimens where possible. If specimens are machined

from sheets or plates, thickness, T, shall be the thickness of the sheet or plate provided this does not exceed the range stated for the intended specimen type. For sheets

of nominal thickness greater than 14 mm (0.55 in.) the specimens shall be machined to 14 ± 0.4 mm (0.55 ± 0.02 in.) in thickness, for use with the Type III specimen. For

sheets of nominal thickness between 14 and 51 mm (0.55 and 2 in.) approximately equal amounts shall be machined from each surface. For thicker sheets both surfaces

of the specimen shall be machined, and the location of the specimen with reference to the original thickness of the sheet shall be noted. Tolerances on thickness less than

14 mm (0.55 in.) shall be those standard for the grade of material tested.

For the Type IV specimen, the internal width of the narrow section of the die shall be 6.00 ± 0.05 mm (0.250 ± 0.002 in.). The dimensions are essentially those of Die

C in Test Methods D412.

The Type V specimen shall be machined or die cut to the dimensions shown, or molded in a mold whose cavity has these dimensions. The dimensions shall be:

W=3.18±0.03mm(0.125±0.001in.),

L=9.53±0.08mm(0.375±0.003in.),

G=7.62±0.02mm(0.300±0.001in.),and

R=12.7±0.08mm(0.500±0.003in.).

The other tolerances are those in the table.

Supporting data on the introduction of the L specimen of Test Method D1822 as the Type V specimen are available from ASTM Headquarters. Request RR:D20-1038.

The tolerances of the width at the center W

shall be +0.00 mm, −0.10 mm ( +0.000 in., −0.004 in.) compared with width Wat other parts of the reduced section. Any

reduction in W at the center shall be gradual, equally on each side so that no abrupt changes in dimension result.

For molded specimens, a draft of not over 0.13 mm (0.005 in.) is allowed for either Type I or II specimens 3.2 mm (0.13 in.) in thickness. See diagram below and this

shall be taken into account when calculating width of the specimen. Thus a typical section of a molded Type I specimen, having the maximum allowable draft, could be

as follows:

Overall widths greater than the minimum indicated are used for some materials in order to avoid breaking in the grips.

Overall lengths greater than the minimum indicated are used for some materials to avoid breaking in the grips or to satisfy special test requirements.

Test marks or initial extensometer span.

When self-tightening grips are used, for highly extensible polymers, the distance between grips will depend upon the types of grips used and may not be critical if

maintained uniform once chosen.

FIG. 1 Tension Test Specimens for Sheet, Plate, and Molded Plastics

D638 − 14

machining shall be 60 % of the original nominal wall thick-

ness. This groove shall consist of a straight section 57.2 mm

(2.25 in.) in length with a radius of 76 mm (3 in.) at each end

joining it to the outside diameter. Steel or brass plugs having

diameters such that they will ﬁt snugly inside the tube and

having a length equal to the full jaw length plus 25 mm (1 in.)

shall be placed in the ends of the specimens to prevent

crushing. They can be located conveniently in the tube by

separating and supporting them on a threaded metal rod.

Details of plugs and test assembly are shown in Fig. 2.

6.3 Rigid Rods—The test specimen for rigid rods shall be as

shown in Fig. 3. The length, L , shall be as shown in the table

in Fig. 3. A groove shall be machined around the specimen at

the center of its length so that the diameter of the machined

portion shall be 60 % of the original nominal diameter. This

groove shall consist of a straight section 57.2 mm (2.25 in.) in

length with a radius of 76 mm (3 in.) at each end joining it to

the outside diameter.

6.4 All surfaces of the specimen shall be free of visible

ﬂaws, scratches, or imperfections. Marks left by coarse ma-

chining operations shall be carefully removed with a ﬁne ﬁle or

abrasive, and the ﬁled surfaces shall then be smoothed with

abrasive paper (No. 00 or ﬁner). The ﬁnishing sanding strokes

shall be made in a direction parallel to the long axis of the test

specimen. All ﬂash shall be removed from a molded specimen,

taking great care not to disturb the molded surfaces. In

machining a specimen, undercuts that would exceed the

dimensional tolerances shown in Fig. 1 shall be scrupulously

avoided. Care shall also be taken to avoid other common

machining errors.

6.5 If it is necessary to place gage marks on the specimen,

this shall be done with a wax crayon or India ink that will not

affect the material being tested. Gage marks shall not be

scratched, punched, or impressed on the specimen.

6.6 When testing materials that are suspected of anisotropy,

duplicate sets of test specimens shall be prepared, having their

long axes respectively parallel with, and normal to, the

suspected direction of anisotropy.

7. Number of Test Specimens

7.1 Test at least ﬁve specimens for each sample in the case

of isotropic materials.

7.2 For anisotropic materials, when applicable, test ﬁve

specimens, normal to, and ﬁve parallel with, the principle axis

of anisotropy.

7.3 Discard specimens that break at some ﬂaw, or that break

outside of the narrow cross-sectional test section (Fig. 1,

dimension "L"), and make retests, unless such ﬂaws constitute

a variable to be studied.

NOTE 10—Before testing, all transparent specimens should be inspected

in a polariscope. Those which show atypical or concentrated strain

patterns should be rejected, unless the effects of these residual strains

constitute a variable to be studied.

8. Speed of Testing

8.1 Speed of testing shall be the relative rate of motion of

the grips or test ﬁxtures during the test. The rate of motion of

the driven grip or ﬁxture when the testing machine is running

DIMENSIONS OF TUBE SPECIMENS

Nominal Wall

Thickness

Length of Radial

Sections,

2R.S.

Total Calculated

Minimum

Length of Specimen

Standard Length, L ,

of Specimen to Be

Used for 89-mm

(3.5-in.) Jaws

mm (in.)

0.79 (

⁄

) 13.9 (0.547) 350 (13.80) 381 (15)

1.2 (

⁄

) 17.0 (0.670) 354 (13.92) 381 (15)

1.6 (

⁄

) 19.6 (0.773) 356 (14.02) 381 (15)

2.4 (

⁄

) 24.0 (0.946) 361 (14.20) 381 (15)

3.2 (

⁄

) 27.7 (1.091) 364 (14.34) 381 (15)

4.8 (

⁄

) 33.9 (1.333) 370 (14.58) 381 (15)

6.4 (

⁄

) 39.0 (1.536) 376 (14.79) 400 (15.75)

7.9 (

⁄

) 43.5 (1.714) 380 (14.96) 400 (15.75)

9.5 (

⁄

) 47.6 (1.873) 384 (15.12) 400 (15.75)

11.1 (

⁄

) 51.3 (2.019) 388 (15.27) 400 (15.75)

12.7 (

⁄

) 54.7 (2.154) 391 (15.40) 419 (16.5)

For jaws greater than 89 mm (3.5 in.), the standard length shall be increased by

twice the length of the jaws minus 178 mm (7 in.). The standard length permits a

slippage of approximately 6.4 to 12.7 mm (0.25 to 0.50 in.) in each jaw while

maintaining the maximum length of the jaw grip.

FIG. 2 Diagram Showing Location of Tube Tension Test Speci-

mens in Testing Machine

D638 − 14

idle may be used, if it can be shown that the resulting speed of

testing is within the limits of variation allowed.

8.2 Choose the speed of testing from Table 1. Determine

this chosen speed of testing by the speciﬁcation for the material

being tested, or by agreement between those concerned. When

the speed is not speciﬁed, use the lowest speed shown in Table

1for the specimen geometry being used, which gives rupture

within 0.5 to 5-min testing time.

8.3 Make modulus determinations at the speed selected for

the other tensile properties when the recorder response and

resolution are adequate.

9. Conditioning

9.1 Conditioning— Condition the test specimens in accor-

dance with Procedure A of Practice D618 , unless otherwise

speciﬁed by contract or the relevant ASTM material speciﬁca-

tion. Conditioning time is speciﬁed as a minimum. Tempera-

ture and humidity tolerances shall be in accordance with

Section 7 of Practice D618 unless speciﬁed differently by

contract or material speciﬁcation.

9.2 Test Conditions—Conduct the tests at the same tempera-

ture and humidity used for conditioning with tolerances in

accordance with Section 7 of Practice D618 , unless otherwise

speciﬁed by contract or the relevant ASTM material speciﬁca-

tion.

10. Procedure

10.1 Measure the width and thickness of each specimen to

the nearest 0.025 mm (0.001 in.) using the applicable test

methods in D5947.

10.1.1 Measure the width and thickness of ﬂat specimens at

the center of each specimen and within 5 mm of each end of the

gage length.

10.1.2 For injection molded specimens, the actual measure-

ment of only one specimen from each sample will suffice when

it has previously been demonstrated that the specimen-to-

specimen variation in width and thickness is less than 1 %.

10.1.3 For thin sheeting, including ﬁlm less than 1.0 mm

(0.04 in.), take the width of specimens produced by a Type IV

die as the distance between the cutting edges of the die in the

DIMENSIONS OF ROD SPECIMENS

Nominal Diam-

eter

Length of Radial

Sections, 2R.S.

Total Calculated

Minimum

Length of Specimen

Standard Length, L ,of

Specimen to Be Used

for 89-mm (3.5-in.)

Jaws

mm (in.)

3.2 (

⁄

) 19.6 (0.773) 356 (14.02) 381 (15)

4.7 (

⁄

) 24.0 (0.946) 361 (14.20) 381 (15)

6.4 (

⁄

) 27.7 (1.091) 364 (14.34) 381 (15)

9.5 (

⁄

) 33.9 (1.333) 370 (14.58) 381 (15)

12.7 (

⁄

) 39.0 (1.536) 376 (14.79) 400 (15.75)

15.9 (

⁄

) 43.5 (1.714) 380 (14.96) 400 (15.75)

19.0 (

⁄

) 47.6 (1.873) 384 (15.12) 400 (15.75)

22.2 (

⁄

) 51.5 (2.019) 388 (15.27) 400 (15.75)

25.4 (1) 54.7 (2.154) 391 (15.40) 419 (16.5)

31.8 (1

⁄

) 60.9 (2.398) 398 (15.65) 419 (16.5)

38.1 (1

⁄

) 66.4 (2.615) 403 (15.87) 419 (16.5)

42.5 (1

⁄

) 71.4 (2.812) 408 (16.06) 419 (16.5)

50.8 (2) 76.0 (2.993) 412 (16.24) 432 (17)

For jaws greater than 89 mm (3.5 in.), the standard length shall be increased by

twice the length of the jaws minus 178 mm (7 in.). The standard length permits a

slippage of approximately 6.4 to 12.7 mm (0.25 to 0.50 in.) in each jaw while

maintaining the maximum length of the jaw grip.

FIG. 3 Diagram Showing Location of Rod Tension Test Specimen

in Testing Machine

TABLE 1 Designations for Speed of Testing

Classiﬁcation

Specimen Type Speed of Testing,

mm/min (in./min)

Nominal

Strain

Rate at

Start of Test,

mm/mm· min

(in./in.·min)

Rigid and Semirigid I, II, III rods and

tubes

5 (0.2) ± 25 % 0.1

50 (2) ± 10 % 1

500 (20) ± 10 % 10

IV 5 (0.2) ± 25 % 0.15

50 (2) ± 10 % 1.5

500 (20) ± 10 % 15

V 1 (0.05) ± 25 % 0.1

10 (0.5) ± 25 % 1

100 (5)± 25 % 10

Nonrigid III 50 (2) ± 10 % 1

500 (20) ± 10 % 10

IV 50 (2) ± 10 % 1.5

500 (20) ± 10 % 15

Select the lowest speed that produces rupture in 0.5 to 5 min for the specimen

geometry being used (see 8.2).

See Terminology D883 for deﬁnitions.

The initial rate of straining cannot be calculated exactly for dumbbell-shaped

specimens because of extension, both in the reduced section outside the gage

length and in the ﬁllets. This initial strain rate can be measured from the initial slope

of the tensile strain-versus-time diagram.

D638 − 14

narrow section. For all other specimens, measure the actual

width of the center portion of the specimen to be tested, unless

it can be shown that the actual width of the specimen is the

same as that of the die within the specimen dimension

tolerances given in Fig. 1.

10.1.4 Measure the diameter of rod specimens, and the

inside and outside diameters of tube specimens, to the nearest

0.025 mm (0.001 in.) at a minimum of two points 90° apart;

make these measurements along the groove for specimens so

constructed. Use plugs in testing tube specimens, as shown in

Fig. 2.

10.2 Place the specimen in the grips of the testing machine,

taking care to align the long axis of the specimen and the grips

with an imaginary line joining the points of attachment of the

grips to the machine. The distance between the ends of the

gripping surfaces, when using ﬂat specimens, shall be as

indicated in Fig. 1. On tube and rod specimens, the location for

the grips shall be as shown in Fig. 2 and Fig. 3. Tighten the

grips evenly and ﬁrmly to the degree necessary to prevent

slippage of the specimen during the test, but not to the point

where the specimen would be crushed.

10.3 Attach the extension indicator. When modulus is being

determined, a Class B-2 or better extensometer is required (see

5.2.1).

NOTE 11—Modulus of materials is determined from the slope of the

linear portion of the stress-strain curve. For most plastics, this linear

portion is very small, occurs very rapidly, and must be recorded automati-

cally. The change in jaw separation is never to be used for calculating

modulus or elongation.

10.4 Set the speed of testing at the proper rate as required in

Section 8, and start the machine.

10.5 Record the load-extension curve of the specimen.

10.6 Record the load and extension at the yield point (if one

exists) and the load and extension at the moment of rupture.

NOTE 12—If it is desired to measure both modulus and failure

properties (yield or break, or both), it may be necessary, in the case of

highly extensible materials, to run two independent tests. The high

magniﬁcation extensometer normally used to determine properties up to

the yield point may not be suitable for tests involving high extensibility.

If allowed to remain attached to the specimen, the extensometer could be

permanently damaged. A broad-range incremental extensometer or hand-

rule technique may be needed when such materials are taken to rupture.

11. Calculation

11.1 Toe compensation shall be made in accordance with

Annex A1, unless it can be shown that the toe region of the

curve is not due to the take-up of slack, seating of the

specimen, or other artifact, but rather is an authentic material

response.

11.2 Tensile Strength—Calculate the tensile strength by

dividing the maximum load sustained by the specimen in

newtons (pounds-force) by the average original cross-sectional

area in the gage length segment of the specimen in square

metres (square inches). Express the result in pascals (pounds-

force per square inch) and report it to three signiﬁcant ﬁgures

as tensile strength at yield or tensile strength at break,

whichever term is applicable. When a nominal yield or break

load less than the maximum is present and applicable, it is

often desirable to also calculate, in a similar manner, the

corresponding tensile stress at yield or tensile stress at break

and report it to three signiﬁcant ﬁgures (see Note A2.8).

11.3 Elongation values are valid and are reported in cases

where uniformity of deformation within the specimen gage

length is present. Elongation values are quantitatively relevant

and appropriate for engineering design. When non-uniform

deformation (such as necking) occurs within the specimen gage

length nominal strain values are reported. Nominal strain

values are of qualitative utility only.

11.3.1 Percent Elongation—Percent elongation is the

change in gage length relative to the original specimen gage

length, expressed as a percent. Percent elongation is calculated

using the apparatus described in 5.2.

11.3.1.1 Percent Elongation at Yield—Calculate the percent

elongation at yield by reading the extension (change in gage

length) at the yield point. Divide that extension by the original

gage length and multiply by 100.

11.3.1.2 Percent Elongation at Break—Calculate the per-

cent elongation at break by reading the extension (change in

gage length) at the point of specimen rupture. Divide that

extension by the original gage length and multiply by 100.

11.3.2 Nominal Strain— Nominal strain is the change in grip

separation relative to the original grip separation expressed as

a percent. Nominal strain is calculated using the apparatus

described in 5.1.7.

11.3.2.1 Nominal strain at break—Calculate the nominal

strain at break by reading the extension (change in grip

separation) at the point of rupture. Divide that extension by the

original grip separation and multiply by 100.

11.4 Modulus of Elasticity—Calculate the modulus of elas-

ticity by extending the initial linear portion of the load-

extension curve and dividing the difference in stress corre-

sponding to any segment of section on this straight line by the

corresponding difference in strain. All elastic modulus values

shall be computed using the average original cross-sectional

area in the gage length segment of the specimen in the

calculations. The result shall be expressed in pascals (pounds-

force per square inch) and reported to three signiﬁcant ﬁgures.

11.5 Secant Modulus—At a designated strain, this shall be

calculated by dividing the corresponding stress (nominal) by

the designated strain. Elastic modulus values are preferable and

shall be calculated whenever possible. However, for materials

where no proportionality is evident, the secant value shall be

calculated. Draw the tangent as directed in A1.3 and Fig. A1.2,

and mark off the designated strain from the yield point where

the tangent line goes through zero stress. The stress to be used

in the calculation is then determined by dividing the load-

extension curve by the original average cross-sectional area of

the specimen.

11.6 For each series of tests, calculate the arithmetic mean

of all values obtained and report it as the "average value" for

the particular property in question.

11.7 Calculate the standard deviation (estimated) as follows

and report it to two signiﬁcant ﬁgures:

(

2nX

n21

(1)

D638 − 14

where:

s= estimated standard deviation,

X= value of single observation,

n= number of observations, and

¯= arithmetic mean of the set of observations.

11.8 See Annex A1 for information on toe compensation.

11.9 See Annex A3 for the determination of Poisson's Ratio.

12. Report

12.1 Report the following information:

12.1.1 Complete identiﬁcation of the material tested, includ-

ing type, source, manufacturer's code numbers, form, principal

dimensions, previous history, etc.,

12.1.2 Method of preparing test specimens,

12.1.3 Type of test specimen and dimensions,

12.1.4 Conditioning procedure used,

12.1.5 Atmospheric conditions in test room,

12.1.6 Number of specimens tested; for anisotropic

materials, the number of specimens tested and the direction in

which they were tested,

12.1.7 Speed of testing,

12.1.8 Classiﬁcation of extensometers used. A description

of measuring technique and calculations employed instead of a

minimum Class-C extensometer system,

12.1.9 Tensile strength at yield or break, average value, and

standard deviation,

12.1.10 Tensile stress at yield or break, if applicable,

average value, and standard deviation,

12.1.11 Percent elongation at yield, or break, or nominal

strain at break, or all three, as applicable, average value, and

standard deviation,

12.1.12 Modulus of elasticity or secant modulus, average

value, and standard deviation,

12.1.13 If measured, Poisson's ratio, average value, stan-

dard deviation, and statement of whether there was proportion-

ality within the strain range,

12.1.14 Date of test, and

12.1.15 Revision date of Test Method D638.

13. Precision and Bias

13.1 Precision— Tables 2-4 are based on a round-robin test

conducted in 1984, involving ﬁve materials tested by eight

laboratories using the Type I specimen, all of nominal 0.125-in.

thickness. Each test result was based on ﬁve individual

determinations. Each laboratory obtained two test results for

each material.

13.1.1 Tables 5-8 are based on a round-robin test conducted

by the polyoleﬁn subcommittee in 1988, involving eight

polyethylene materials tested in ten laboratories. For each

material, all samples were molded at one source, but the

individual specimens were prepared at the laboratories that

tested them. Each test result was the average of ﬁve individual

determinations. Each laboratory obtained three test results for

each material. Data from some laboratories could not be used

for various reasons, and this is noted in each table.

13.1.2 Tables 9 and 10 are based on a round-robin test

conducted by the polyoleﬁn subcommittee in 1988, involving

three materials tested in eight laboratories. For each material,

all samples were molded at one source, but the individual

specimens were prepared at the laboratories that tested them.

Each test result was the average of ﬁve individual determina-

tions. Each laboratory obtained three test results for each

material.

Supporting data are available from ASTM Headquarters. Request RR:D20-

1125 for the 1984 round robin and RR:D20-1170 for the 1988 round robin.

TABLE 2 Modulus, 10

psi, for Eight Laboratories, Five Materials

Mean S

Polypropylene 0.210 0.0089 0.071 0.025 0.201

Cellulose acetate butyrate 0.246 0.0179 0.035 0.051 0.144

Acrylic 0.481 0.0179 0.063 0.051 0.144

Glass-reinforced nylon 1.17 0.0537 0.217 0.152 0.614

Glass-reinforced polyester 1.39 0.0894 0.266 0.253 0.753

TABLE 3 Tensile Stress at Break, 10

psi, for Eight Laboratories,

Five Materials

Mean S

Polypropylene 2.97 1.54 1.65 4.37 4.66

Cellulose acetate butyrate 4.82 0.058 0.180 0.164 0.509

Acrylic 9.09 0.452 0.751 1.27 2.13

Glass-reinforced polyester 20.8 0.233 0.437 0.659 1.24

Glass-reinforced nylon 23.6 0.277 0.698 0.784 1.98

Tensile strength and elongation at break values obtained for unreinforced

propylene plastics generally are highly variable due to inconsistencies in necking

or "drawing" of the center section of the test bar. Since tensile strength and

elongation at yield are more reproducible and relate in most cases to the practical

usefulness of a molded part, they are generally recommended for speciﬁcation

purposes.

TABLE 4 Elongation at Break, %, for Eight Laboratories, Five

Materials

Mean S

Glass-reinforced polyester 3.68 0.20 2.33 0.570 6.59

Glass-reinforced nylon 3.87 0.10 2.13 0.283 6.03

Acrylic 13.2 2.05 3.65 5.80 10.3

Cellulose acetate butyrate 14.1 1.87 6.62 5.29 18.7

Polypropylene 293.0 50.9 119.0 144.0 337.0

Tensile strength and elongation at break values obtained for unreinforced

propylene plastics generally are highly variable due to inconsistencies in necking

or "drawing" of the center section of the test bar. Since tensile strength and

elongation at yield are more reproducible and relate in most cases to the practical

usefulness of a molded part, they are generally recommended for speciﬁcation

purposes.

TABLE 5 Tensile Yield Stress, for Ten Laboratories, Eight

Materials

Material

Test

Speed,

in./min

Values Expressed in psi Units

Average S

LDPE 20 1544 52.4 64.0 146.6 179.3

LDPE 20 1894 53.1 61.2 148.7 171.3

LLDPE 20 1879 74.2 99.9 207.8 279.7

LLDPE 20 1791 49.2 75.8 137.9 212.3

LLDPE 20 2900 55.5 87.9 155.4 246.1

LLDPE 20 1730 63.9 96.0 178.9 268.7

HDPE 2 4101 196.1 371.9 549.1 1041.3

HDPE 2 3523 175.9 478.0 492.4 1338.5

D638 − 14

13.1.3 Table 11 is based on a repeatability study involving a

single laboratory. The two materials used were unﬁlled poly-

propylene types. Measurements were performed by a single

technician on a single day. Each test result is an individual

determination. Testing was run using two Type B-1 extensom-

eters for transverse and axial measurements at a test speed of

5 mm/min.

13.1.4 In Tables 2-11, for the materials indicated, and for

test results that derived from testing ﬁve specimens:

13.1.4.1 S

is the within-laboratory standard deviation of the

average; I

= 2.83 S

. (See 13.1.4.3 for application of I

13.1.4.2 S

is the between-laboratory standard deviation of

the average; I

= 2.83 S

. (See 13.1.4.4 for application of I

13.1.4.3 Repeatability— In comparing two test results for

the same material, obtained by the same operator using the

same equipment on the same day, those test results should be

judged not equivalent if they differ by more than the I

value

for that material and condition.

13.1.4.4 Reproducibility— In comparing two test results for

the same material, obtained by different operators using differ-

ent equipment on different days, those test results should be

judged not equivalent if they differ by more than the I

value

for that material and condition. (This applies between different

laboratories or between different equipment within the same

laboratory.)

13.1.4.5 Any judgment in accordance with 13.1.4.3 and

13.1.4.4 will have an approximate 95 % (0.95) probability of

being correct.

13.1.4.6 Other formulations may give somewhat different

results.

13.1.4.7 For further information on the methodology used in

this section, see Practice E691.

13.1.4.8 The precision of this test method is very dependent

upon the uniformity of specimen preparation, standard prac-

tices for which are covered in other documents.

13.2 Bias— There are no recognized standards on which to

base an estimate of bias for this test method.

14. Keywords

14.1 modulus of elasticity; percent elongation; plastics;

Poisson's Ratio; tensile properties; tensile strength

TABLE 6 Tensile Yield Elongation, for Eight Laboratories, Eight

Materials

Material

Test

Speed,

in./min

Values Expressed in Percent Units

Average S

LDPE 20 17.0 1.26 3.16 3.52 8.84

LDPE 20 14.6 1.02 2.38 2.86 6.67

LLDPE 20 15.7 1.37 2.85 3.85 7.97

LLDPE 20 16.6 1.59 3.30 4.46 9.24

LLDPE 20 11.7 1.27 2.88 3.56 8.08

LLDPE 20 15.2 1.27 2.59 3.55 7.25

HDPE 2 9.27 1.40 2.84 3.91 7.94

HDPE 2 9.63 1.23 2.75 3.45 7.71

TABLE 7 Tensile Break Stress, for Nine Laboratories, Six

Materials

Material

Test

Speed,

in./min

Values Expressed in psi Units

Average S

LDPE 20 1592 52.3 74.9 146.4 209.7

LDPE 20 1750 66.6 102.9 186.4 288.1

LLDPE 20 4379 127.1 219.0 355.8 613.3

LLDPE 20 2840 78.6 143.5 220.2 401.8

LLDPE 20 1679 34.3 47.0 95.96 131.6

LLDPE 20 2660 119.1 166.3 333.6 465.6

TABLE 8 Tensile Break Elongation, for Nine Laboratories, Six

Materials

Material

Test

Speed,

in./min

Values Expressed in Percent Units

Average S

LDPE 20 567 31.5 59.5 88.2 166.6

LDPE 20 569 61.5 89.2 172.3 249.7

LLDPE 20 890 25.7 113.8 71.9 318.7

LLDPE 20 64.4 6.68 11.7 18.7 32.6

LLDPE 20 803 25.7 104.4 71.9 292.5

LLDPE 20 782 41.6 96.7 116.6 270.8

TABLE 9 Tensile Stress at Yield, 10

psi, for Eight Laboratories,

Three Materials

Mean S

Polypropylene 3.63 0.022 0.161 0.062 0.456

Cellulose acetate butyrate 5.01 0.058 0.227 0.164 0.642

Acrylic 10.4 0.067 0.317 0.190 0.897

TABLE 10 Elongation at Yield, %, for Eight Laboratories, Three

Materials

Mean S

Cellulose acetate butyrate 3.65 0.27 0.62 0.76 1.75

Acrylic 4.89 0.21 0.55 0.59 1.56

Polypropylene 8.79 0.45 5.86 1.27 16.5

TABLE 11 Poisson's Ratio Repeatability Data for One Laboratory

and Two Polypropylene Materials

Materials Values Expressed as a Dimensionless Ratio

Average S

PP #1 Chord 0.412 0.009 0.026

PP #1 Least

Squares

0.413 0.011 0.032

PP #2 Chord 0.391 0.009 0.026

PP #2 Least

Squares

0.392 0.010 0.028

D638 − 14

ANNEXES

(Mandatory Information)

A1. TOE COMPENSATION

A1.1 In a typical stress-strain curve (Fig. A1.1) there is a

toe region, AC , that does not represent a property of the

material. It is an artifact caused by a takeup of slack and

alignment or seating of the specimen. In order to obtain correct

values of such parameters as modulus, strain, and offset yield

point, this artifact must be compensated for to give the

corrected zero point on the strain or extension axis.

A1.2 In the case of a material exhibiting a region of

Hookean (linear) behavior (Fig. A1.1 ), a continuation of the

linear (CD) region of the curve is constructed through the

zero-stress axis. This intersection (B) is the corrected zero-

strain point from which all extensions or strains must be

measured, including the yield offset (BE ), if applicable. The

elastic modulus can be determined by dividing the stress at any

point along the line CD (or its extension) by the strain at the

same point (measured from Point B, deﬁned as zero-strain).

A1.3 In the case of a material that does not exhibit any

linear region (Fig. A1.2 ), the same kind of toe correction of the

zero-strain point can be made by constructing a tangent to the

maximum slope at the inﬂection point (H'). This is extended to

intersect the strain axis at Point B', the corrected zero-strain

point. Using Point B' as zero strain, the stress at any point (G')

on the curve can be divided by the strain at that point to obtain

a secant modulus (slope of Line B' G'). For those materials with

no linear region, any attempt to use the tangent through the

inﬂection point as a basis for determination of an offset yield

point may result in unacceptable error.

NOTE 1—

Some chart recorders plot the mirror image of this graph.

FIG. A1.1 Material with Hookean Region

NOTE 1—Some chart recorders plot the mirror image of this graph.

FIG. A1.2 Material with No Hookean Region

D638 − 14

A2. DEFINITIONS OF TERMS AND SYMBOLS RELATING TO TENSION TESTING OF PLASTICS

A2.1 elastic limit—the greatest stress which a material is

capable of sustaining without any permanent strain remaining

upon complete release of the stress. It is expressed in force per

unit area, usually megapascals (pounds-force per square inch).

NOTE A2.1—Measured values of proportional limit and elastic limit

vary greatly with the sensitivity and accuracy of the testing equipment,

eccentricity of loading, the scale to which the stress-strain diagram is

plotted, and other factors. Consequently, these values are usually replaced

by yield strength.

A2.2 elongation —the increase in length produced in the

gage length of the test specimen by a tensile load. It is

expressed in units of length, usually millimetres (inches). (Also

known as extension.)

NOTE A2.2—Elongation and strain values are valid only in cases where

uniformity of specimen behavior within the gage length is present. In the

case of materials exhibiting necking phenomena, such values are only of

qualitative utility after attainment of yield point. This is due to inability to

ensure that necking will encompass the entire length between the gage

marks prior to specimen failure.

A2.3 gage length—the original length of that portion of the

specimen over which strain or change in length is determined.

A2.4 modulus of elasticity—the ratio of stress (nominal) to

corresponding strain below the proportional limit of a material.

It is expressed in force per unit area, usually megapascals

(pounds-force per square inch). (Also known as elastic modu-

lus or Young's modulus).

NOTE A2.3—The stress-strain relations of many plastics do not conform

to Hooke's law throughout the elastic range but deviate therefrom even at

stresses well below the elastic limit. For such materials the slope of the

tangent to the stress-strain curve at a low stress is usually taken as the

modulus of elasticity. Since the existence of a true proportional limit in

plastics is debatable, the propriety of applying the term "modulus of

elasticity" to describe the stiffness or rigidity of a plastic has been

seriously questioned. The exact stress-strain characteristics of plastic

materials are very dependent on such factors as rate of stressing,

temperature, previous specimen history, etc. However, such a value is

useful if its arbitrary nature and dependence on time, temperature, and

other factors are realized.

A2.5 necking —the localized reduction in cross section

which may occur in a material under tensile stress.

A2.6 offset yield strength—the stress at which the strain

exceeds by a speciﬁed amount (the offset) an extension of the

initial proportional portion of the stress-strain curve. It is

expressed in force per unit area, usually megapascals (pounds-

force per square inch).

NOTE A2.4—This measurement is useful for materials whose stress-

strain curve in the yield range is of gradual curvature. The offset yield

strength can be derived from a stress-strain curve as follows (Fig. A2.1):

On the strain axis lay off OM equal to the speciﬁed offset.

Draw OA tangent to the initial straight-line portion of the stress-strain

curve.

Through Mdraw a line MN parallel to OA and locate the intersection of

MN with the stress-strain curve.

The stress at the point of intersection ris the "offset yield strength." The

speciﬁed value of the offset must be stated as a percent of the original gage

length in conjunction with the strength value. Example: 0.1 % offset yield

strength = ... MPa (psi), or yield strength at 0.1 % offset ... MPa (psi).

A2.7 percent elongation —the elongation of a test specimen

expressed as a percent of the gage length.

A2.8 percent elongation at break and yield:

A2.8.1 percent elongation at break—the percent elongation

at the moment of rupture of the test specimen.

A2.8.2 percent elongation at yield—the percent elongation

at the moment the yield point (A2.22 ) is attained in the test

specimen.

A2.9 percent reduction of area (nominal)—the difference

between the original cross-sectional area measured at the point

of rupture after breaking and after all retraction has ceased,

expressed as a percent of the original area.

A2.10 percent reduction of area (true)—the difference be-

tween the original cross-sectional area of the test specimen and

the minimum cross-sectional area within the gage boundaries

prevailing at the moment of rupture, expressed as a percentage

of the original area.

A2.11 Poisson's Ratio—The absolute value of the ratio of

transverse strain to the corresponding axial strain resulting

from uniformly distributed axial stress below the proportional

limit of the material.

A2.12 proportional limit —the greatest stress which a mate-

rial is capable of sustaining without any deviation from

proportionality of stress to strain (Hooke's law). It is expressed

in force per unit area, usually megapascals (pounds-force per

square inch).

A2.13 rate of loading—the change in tensile load carried by

the specimen per unit time. It is expressed in force per unit

time, usually newtons (pounds-force) per minute. The initial

rate of loading can be calculated from the initial slope of the

load versus time diagram.

FIG. A2.1 Offset Yield Strength

D638 − 14

A2.14 rate of straining—the change in tensile strain per unit

time. It is expressed either as strain per unit time, usually

metres per metre (inches per inch) per minute, or percent

elongation per unit time, usually percent elongation per minute.

The initial rate of straining can be calculated from the initial

slope of the tensile strain versus time diagram.

NOTE A2.5—The initial rate of straining is synonymous with the rate of

crosshead movement divided by the initial distance between crossheads

only in a machine with constant rate of crosshead movement and when the

specimen has a uniform original cross section, does not "neck down," and

does not slip in the jaws.

A2.15 rate of stressing (nominal)—the change in tensile

stress (nominal) per unit time. It is expressed in force per unit

area per unit time, usually megapascals (pounds-force per

square inch) per minute. The initial rate of stressing can be

calculated from the initial slope of the tensile stress (nominal)

versus time diagram.

NOTE A2.6—The initial rate of stressing as determined in this manner

has only limited physical signiﬁcance. It does, however, roughly describe

the average rate at which the initial stress (nominal) carried by the test

specimen is applied. It is affected by the elasticity and ﬂow characteristics

of the materials being tested. At the yield point, the rate of stressing (true)

may continue to have a positive value if the cross-sectional area is

decreasing.

A2.16 secant modulus—the ratio of stress (nominal) to

corresponding strain at any speciﬁed point on the stress-strain

curve. It is expressed in force per unit area, usually megapas-

cals (pounds-force per square inch), and reported together with

the speciﬁed stress or strain.

NOTE A2.7—This measurement is usually employed in place of

modulus of elasticity in the case of materials whose stress-strain diagram

does not demonstrate proportionality of stress to strain.

A2.17 strain —the ratio of the elongation to the gage length

of the test specimen, that is, the change in length per unit of

original length. It is expressed as a dimensionless ratio.

A2.17.1 nominal strain at break—the strain at the moment

of rupture relative to the original grip separation.

A2.18 tensile strength (nominal)—the maximum tensile

stress (nominal) sustained by the specimen during a tension

test. When the maximum stress occurs at the yield point

(A2.22), it shall be designated tensile strength at yield. When

the maximum stress occurs at break, it shall be designated

tensile strength at break.

A2.19 tensile stress (nominal)—the tensile load per unit

area of minimum original cross section, within the gage

boundaries, carried by the test specimen at any given moment.

It is expressed in force per unit area, usually megapascals

(pounds-force per square inch).

NOTE A2.8—The expression of tensile properties in terms of the

minimum original cross section is almost universally used in practice. In

the case of materials exhibiting high extensibility or necking, or both

(A2.16), nominal stress calculations may not be meaningful beyond the

yield point (A2.22 ) due to the extensive reduction in cross-sectional area

that ensues. Under some circumstances it may be desirable to express the

tensile properties per unit of minimum prevailing cross section. These

properties are called true tensile properties (that is, true tensile stress, etc.).

A2.20 tensile stress-strain curve—a diagram in which val-

ues of tensile stress are plotted as ordinates against correspond-

ing values of tensile strain as abscissas.

A2.21 true strain (see Fig. A2.2) is deﬁned by the following

equation for ε

dL/L5 ln L/L

(A2.1)

where:

dL = increment of elongation when the distance between the

gage marks is L,

= original distance between gauge marks, and

L= distance between gauge marks at any time.

A2.22 yield point—the ﬁrst point on the stress-strain curve

at which an increase in strain occurs without an increase in

stress (Fig. A2.2).

NOTE A2.9—Only materials whose stress-strain curves exhibit a point

of zero slope may be considered as having a yield point.

NOTE A2.10—Some materials exhibit a distinct "break" or discontinuity

in the stress-strain curve in the elastic region. This break is not a yield

point by deﬁnition. However, this point may prove useful for material

characterization in some cases.

A2.23 yield strength—the stress at which a material exhibits

a speciﬁed limiting deviation from the proportionality of stress

to strain. Unless otherwise speciﬁed, this stress will be the

stress at the yield point and when expressed in relation to the

tensile strength shall be designated either tensile strength at

yield or tensile stress at yield as required in A2.18 ( Fig. A2.3).

(See offset yield strength.)

FIG. A2.2 Illustration of True Strain Equation

D638 − 14

A2.24 Symbols —The following symbols may be used for

the above terms:

Symbol Term

WLoad

∆W Increment of load

LDistance between gage marks at any time

Original distance between gage marks

Distance between gage marks at moment of rupture

∆L Increment of distance between gage marks = elongation

AMinimum cross-sectional area at any time

Original cross-sectional area

∆A Increment of cross-sectional area

Cross-sectional area at point of rupture measured after

breaking specimen

Cross-sectional area at point of rupture, measured at the

moment of rupture

tTime

∆t Increment of time

σTensile stress

∆σ Increment of stress

True tensile stress

Tensile strength at break (nominal)

Tensile strength at break (true)

εStrain

∆ε Increment of strain

Total strain, at break

True strain

%El Percentage elongation

Y.P. Yield point

EModulus of elasticity

A2.25 Relations between these various terms may be

deﬁned as follows:

σ=W/A

=W/A

(where W is breaking load)

=W/A

(where W is breaking load)

ε= ∆L/L

=( L− L

)/L

=( L

−L

)/L

dL/L5 lnL/ L

%El =[( L−L

)/L

] × 100 = ε × 100

Percent reduction of area (nominal) = [(A

−A

)/A

] × 100

Percent reduction of area (true) = [(A

−A

)/A

] × 100

Rate of loading = ∆ W⁄ ∆t

Rate of stressing (nominal) = ∆σ ⁄∆=( ∆W] ⁄A

)/∆t

Rate of straining = ∆ε ⁄ ∆ t=( ∆L⁄L

)∆t

For the case where the volume of the test specimen does not

change during the test, the following three relations hold:

5σ

11ε

5σL/ L

(A2.2)

5σ

11ε

5σ

A5 A

11ε

A3. MEASUREMENT OF POISSON'S RATIO

A3.1. Scope

A3.1.1 This test method covers the determination of Pois-

son's ratio obtained from strains resulting from uniaxial stress

only.

A3.1.2 Test data obtained by this test method are relevant

and appropriate for use in engineering design.

A3.1.3 The values stated in SI units are regarded as the

standard. The values given in parentheses are for information

only.

NOTE A3.1—This standard is not equivalent to ISO 527-1.

A3.2. Referenced Documents

A3.2.1 ASTM Standards:

D618 Practice for Conditioning Plastics for Testing

D883 Terminology Relating to Plastics

D5947 Test Methods for Physical Dimensions of Solid

Plastics Specimens

E83 Practice for Veriﬁcation and Classiﬁcation of Exten-

someter Systems

E132 Test Method for Poisson's Ratio at Room Temperature

E691 Practice for Conducting an Interlaboratory Study to

Determine the Precision of a Test Method

FIG. A2.3 Tensile Designations

D638 − 14

E1012 Practice for Veriﬁcation of Testing Frame and Speci-

men Alignment Under Tensile and Compressive Axial

Force Application

A3.2.2 ISO Standard:

ISO 527–1 Determination of Tensile Properties

A3.3. Terminology

A3.3.1 Deﬁnitions —Deﬁnitions of terms applying to this

test method appear in Terminology D883 and Annex A2 of this

standard.

A3.4. Signiﬁcance and Use

A3.4.1 When uniaxial tensile force is applied to a solid, the

solid stretches in the direction of the applied force (axially), but

it also contracts in both dimensions perpendicular to the

applied force. If the solid is homogeneous and isotropic, and

the material remains elastic under the action of the applied

force, the transverse strain bears a constant relationship to the

axial strain. This constant, called Poisson's ratio, is deﬁned as

the negative ratio of the transverse (negative) to axial strain

under uniaxial stress.

A3.4.2 Poisson's ratio is used for the design of structures in

which all dimensional changes resulting from the application

of force need to be taken into account and in the application of

the generalized theory of elasticity to structural analysis.

NOTE A3.2—The accuracy of the determination of Poisson's ratio is

usually limited by the accuracy of the transverse strain measurements

because the percentage errors in these measurements are usually greater

than in the axial strain measurements. Since a ratio rather than an absolute

quantity is measured, it is only necessary to know accurately the relative

value of the calibration factors of the extensometers. Also, in general, the

value of the applied loads need not be known accurately.

A3.5. Apparatus

A3.5.1 Refer to 5.1 and 5.3 of this standard for the require-

ments of the testing machine and micrometers.

A3.5.2 For measurement of Poisson's Ratio use either a

bi-axial extensometer or an axial extensometer in combination

with a transverse extensometer. They must be capable of

recording axial strain and transverse strain simultaneously. The

extensometers shall be capable of measuring the change in

strains with an accuracy of 1 % of the relevant value or better.

NOTE A3.3—Strain gages are used as an alternative method to measure

axial and transverse strain; however, proper techniques for mounting

strain gauges are crucial to obtaining accurate data. Consult strain gauge

suppliers for instruction and training in these special techniques.

A3.6. Test Specimen

A3.6.1 Specimen —The test specimen shall conform to the

dimensions shown in Fig. 1. The Type I specimen is the

preferred specimen and shall be used where sufficient material

having a thickness of 7 mm (0.28 in.) or less is available.

A3.6.2 Preparation —Test specimens shall be prepared by

machining operations, or die cutting, from materials in sheet,

plate, slab, or similar form or be prepared by molding the

material into the specimen shape to be tested.

NOTE A3.4—When preparing specimens from certain composite lami-

nates such as woven roving, or glass cloth, care must be exercised in

cutting the specimens parallel to the reinforcement, unless testing of

specimens in a direction other than parallel with the reinforcement

constitutes a variable being studied.

NOTE A3.5—Specimens prepared by injection molding have different

tensile properties than specimens prepared by machining or die-cutting

because of the orientation induced. This effect is more pronounced in

specimens with narrow sections.

A3.6.3 All surfaces of the specimen shall be free of visible

ﬂaws, scratches, or imperfections. Marks left by coarse ma-

chining operations shall be carefully removed with a ﬁne ﬁle or

abrasive, and the ﬁled surfaces shall then be smoothed with

abrasive paper (No. 00 or ﬁner). The ﬁnishing sanding strokes

shall be made in a direction parallel to the long axis of the test

specimen. All ﬂash shall be removed from a molded specimen,

taking great care not to disturb the molded surfaces. In

machining a specimen, undercuts that would exceed the

dimensional tolerances shown in Fig. 1 shall be scrupulously

avoided. Care shall also be taken to avoid other common

machining errors.

A3.6.4 If it is necessary to place gage marks on the

specimen, this shall be done with a wax crayon or India ink that

will not affect the material being tested. Gauge marks shall not

be scratched, punched, or impressed on the specimen.

A3.6.5 When testing materials that are suspected of

anisotropy, duplicate sets of test specimens shall be prepared,

having their long axes respectively parallel with, and normal

to, the suspected direction of anisotropy.

A3.7 Number of Test Specimens

A3.7.1 Test at least ﬁve specimens for each sample in the

case of isotropic materials.

A3.7.2 Test ten specimens, ﬁve normal to, and ﬁve parallel

with, the principle axis of anisotropy, for each sample in the

case of anisotropic materials.

A3.8. Conditioning

A3.8.1 Specimens shall be conditioned and tested in accor-

dance with the requirement shown in Section 9 of this standard.

A3.9. Procedure

A3.9.1 Measure the width and thickness of each specimen

to the nearest 0.025 mm (0.001 in.) using the applicable test

methods in D5947 . Follow the guidelines speciﬁed in 10.1.1

and 10.1.2 of this standard.

A3.9.2 Poisson's Ratio shall be determined at a speed of 5

mm/min.

A3.9.3 Place the specimen in the grips of the testing

machine, taking care to align the long axis of the specimen and

the grips with an imaginary line joining the points of attach-

ment of the grips to the machine. The distance between the

ends of the gripping surfaces, when using ﬂat specimens, shall

be as indicated in Fig. 1. Tighten the grips evenly and ﬁrmly to

the degree necessary to prevent slippage of the specimen

during the test, but not to the point where the specimen would

be crushed.

D638 − 14

A3.9.4 Attach the biaxial extensometer or the axial and

transverse extensometer combination to the specimen. The

transverse extensometer should be attached to the width of the

specimen.

A3.9.5 Apply a small preload (less than 5 N) to the

specimen at a crosshead speed of 0.1 mm/min. This preload

will eliminate any bending in the specimens.

A3.9.6 Rebalance the extensometers to zero.

A3.9.7 Run the test at 5 mm/min out to a minimum of 0.5 %

strain before removing the extensometers, simultaneously re-

cording the strain readings from the extensometers at the same

applied force. The precision of the value of Poisson's Ratio

will depend on the number of data points of axial and

transverse strain taken. It is recommended that the data

collection rate for the test be a minimum of 20 points per

second (but preferably higher). This is particularly important

for materials having a non linear stress to strain curve.

A3.9.8 Make the toe compensation in accordance with

Annex A1. Determine the maximum strain (proportional limit)

at which the curve is linear. If this strain is greater than 0.25 %

the Poisson's Ratio is to be determined anywhere in this linear

portion of the curve below the proportional limit. If the

material does not exhibit a linear stress to strain relationship

the Poisson's Ratio shall be determined within the axial strain

range of 0.0005 to 0.0025 mm/mm (0.05 to 0.25 %). If the ratio

is determined in this manner it shall be noted in the report that

a region of proportionality of stress to strain was not evident.

NOTE A3.6—A suitable method for determination of linearity of the

stress to strain curve is by making a series of tangent modulus measure-

ments at different axial strain levels. Values equivalent at each strain level

indicate linearity. Values showing a downward trend with increasing strain

level indicate non linearity.

A3.10. Calculation

A3.10.1 Poisson's Ratio—The axial strain, ε

, indicated by

the axial extensometer, and the transverse strain, ε

, indicated

by the transverse extensometers, are plotted against the applied

load, P , as shown in Fig. A3.1.

A3.10.1.1 For those materials where there is proportionality

of stress to strain and it is possible to determine a modulus of

elasticity, a straight line is drawn through each set of points

within the load range used for determination of modulus, and

the slopes dε

/dP and dε

/dP , of those lines are determined.

The use of a least squares method of calculation will reduce

errors resulting from drawing lines. Poisson's Ratio, |µ|, is then

calculated as follows:

µ?5

dε

/dP

dε

/dP

(A3.1)

where:

dε

5change in transverse strain,

dε

5change in axial strain, and

dP 5 change in applied load;

µ?5

dε

(A3.2)

A3.10.1.2 The errors that are introduced by drawing a

straight line through the points are reduced by applying the

least squares method.

A3.10.1.3 For those materials where there is no proportion-

ality of stress to strain evident determine the ratio of dε

/dε

when dε

= 0.002 (based on axial strain range of 0.0005 to

0.0025 mm/mm) and after toe compensation has been made.

µ?5dε

/0.002 (A3.3)

A3.11. Report

A3.11.1 Report the following information:

A3.11.1.1 Complete identiﬁcation of the material tested,

including type, source, manufacturer's code numbers, form,

principal dimensions, previous history, etc.,

A3.11.1.2 Method of preparing test specimens,

A3.11.1.3 Type of test specimen and dimensions,

A3.11.1.4 Conditioning procedure used,

A3.11.1.5 Atmospheric conditions in test room,

A3.11.1.6 Number of specimens tested,

A3.11.1.7 Speed of testing,

A3.11.1.8 Classiﬁcation of extensometers used. A descrip-

tion of measuring technique and calculations employed,

FIG. A3.1 Plot of Strains Versus Load for Determination of Poisson's Ratio

D638 − 14

A3.11.1.9 Poisson's ratio, average value, standard

deviation, and statement of whether there was proportionality

within the strain range,

A3.11.1.10 Date of test, and

A3.11.1.11 Revision date of Test Method D618.

A3.12. Precision and Bias

A3.12.1 Precision —The repeatability standard deviation

has been determined to be the following (see Table A3.1.) An

attempt to develop a full precision and bias statement for this

test method will be made at a later date. For this reason, data

on precision and bias cannot be given. Because this test method

does not contain a round-robin based numerical precision and

bias statement, it shall not be used as a referee test method in

case of dispute. Anyone wishing to participate in the develop-

ment of precision and bias data should contact the Chairman,

Subcommittee D20.10 Mechanical Properties, ASTM

International, 100 Barr Harbor, West Conshohocken, PA

19428.

A3.13 Keywords

axial strain; Poisson's ratio; transverse strain

D638 − 14

SUMMARY OF CHANGES

Committee D20 has identiﬁed the location of selected changes to this standard since the last issue (D638 - 10)

that may impact the use of this standard. (December 15, 2014)

(1) Revised Note 1 since changes were made to ISO 527-1, and

it is no longer equivalent to this standard.

(2) Removed permissive language.

(3) Made some editorial changes.

(4) Moved Tables 2-5 to Section 13 on Precision and Bias.

(5) Revised Summary of Changes section.

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in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk

of infringement of such rights, are entirely their own responsibility.

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if not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standards

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TABLE A3.1 Poisson's Ratio Based on One Laboratory

Material Extensometer Type Average V

PP Copolymer 2–point 0.408 0.011 0.031

PP Copolymer 4–point 0.392 0.010 0.028

PP Homopolymer with 20 % Glass 2–point 0.428 0.013 0.036

PP Homopolymer with 20 % Glass 4–point 0.410 0.015 0.042

= within laboratory standard deviation for the indicated material. It is obtained by ﬁrst pooling the with-laboratory standard deviations of the test results from all the

participating laboratories:

1{{ 1

1/2

= between-laboratories reproducibility, expressed as standard deviation: S

=[S

)

1/2

r = within-laboratory critical interval between two test results = 2.8 × S

R = between-laboratories critical interval between two test results = 2.8 × S

D638 − 14

... The newly mixed material was processed using a 3.5 mL microinjection molder (DSM, Geleen, The Netherlands). The microinjection molder was used to create 5 dog-bone shaped samples (ASTM D638 Type-V) for each condition [14]. The barrel temperature was set to 165 and 190 • C for LLDPE and PP, respectively, and the mold temperature was 65 • C for all cases. ...

Collin Coben
Erol Sancaktar

In the competitive market of plastic fillers, inexpensive and reliable materials are always sought after. Using a method of thermal conversion called pyrolysis, a potential contender was created from a plant biomass known as soybean hulls (SBH). SBH are a byproduct of the soybean farming industry and represent an abundant and inexpensive feedstock. The thermal conversion of SBH material gives rise to a lightweight carbon-rich filler called pyrolyzed soybean hulls (PSBH). We created two separate lots, lots A and B, with lot A corresponding to SBH pyrolyzed at 450 °C (PSBH-A) and lot B corresponding to SBH pyrolyzed at 500 °C (PSBH-B). Both lots of PSBH were also milled to reduce their particle size and tested against the as-received PSBH fillers. These milled materials were designated as ground soybean hulls (GSBH). Two different polyolefins, linear low-density polyethylene (LLDPE) and polypropylene (PP), were used for this study. The PSBH fillers were added to the polyolefins in weight percentages of 10%, 20%, 30%, 40%, and 50%, with the resulting plastic/PSBH composites being tested for their mechanical, thermal, and water absorption properties. In general, the addition of filler increased the maximum stress of the LLDPE/PSBH composites while reducing maximum stress of the PP/PSBH composites. The strain at maximum stress was reduced with increasing amounts of the PSBH filler for all composites. The modulus of elasticity generally increased with increasing filler amount. For thermal properties, the addition of the PSBH filler increased the heat distortion temperature, increased the thermal decomposition temperature, and reduced the heat of fusion of the composites compared to the neat polyolefins. The liquid absorption and thickness swelling in the materials were small overall but did increase with increasing amounts of the PSBH filler and with the time spent submerged in liquid. Milling the PSBH material into GSBH generally had small effects on the various tested material properties and led to easier mixing and a smoother finish on the surface of processed samples. The differences observed between lot A and lot B composites were often small or even negligible.

... However, a higher density of 3.0 kg/m 2 was still preferred in laboratory studies because it could guarantee more stable test results. [26] was adopted to investigate its mechanical properties. Details of the test were exhibited in Figure 5. Epoxy resin specimens were prepared in a dumbbell-shaped mold with a thickness of 3.5 mm. ...

Xiaoguang Zheng
Qi Ren
Huan Xiong
Xiaoming Song

As one of the major contributors to the early failures of steel bridge deck pavements, the bonding between steel and asphalt overlay has long been a troublesome issue. In this paper, a novel composite bonding structure was introduced consisting of epoxy resin micaceous iron oxide (EMIO) primer, solvent-free epoxy resin waterproof layer, and ethylene-vinyl acetate (EVA) hot melt pellets. A series of strength tests were performed to study its mechanical properties, including pull-off strength tests, dumbbell tensile tests, lap shear tests, direct tension tests, and 45°-inclined shear tests. The results suggested that the bonding structure exhibited fair bonding strength, tensile strength, and shear strength. Anisotropic behaviour was also observed at high temperatures. For epoxy resin waterproof layer, the loss of bonding strength, tensile strength, and shear strength at 60°C was 70%, 35%, and 39%, respectively. Subsequent pavement performance-oriented tests included five-point bending tests and accelerated wheel tracking tests. The impacts of bonding on fatigue resistance and rutting propagation were studied. It was found that the proposed bonding structure could provide a durable and well-bonded interface and was thus beneficial to prolong the fatigue lives of asphalt overlay. The choice of bonding materials was found irrelevant to the ultimate rutting depth of pavements. But the bonding combination of epoxy resin waterproof and EVA pellets could delay the early-stage rutting propagation.

... The mixed resin was added to the hopper of a production-scale injection molder, as seen in Fig. 1 , (Battenfeld HM90/350 90-ton horizontal, Wittmann Battenfeld, Torrington, CT) with an injection profile of 185 °C-195 °C. At least 15 Type I dog bone injection-molded specimens were produced according to ASTM D638-14 [2] . ...

This paper compiles polymer characterization data collected from polyethylene (PE) blends composed of different densities (low-density, LDPE, linear low-density, LLDPE, medium-density, MDPE, and high-density, HDPE) and post-consumer recycled polyethylene (PCRPE), as presented by Cecon et al. [1]. The data were collected from injection molded samples submitted to several physical, thermal, and mechanical characterization techniques, including density, melt flow rate (MFR), thermogravimetric analysis, mechanical testing, and Fourier transform infrared spectroscopy. As there is a significant urgency in recycled polymer utilization in new consumer products from consumers, companies, and governments, the dataset herein presented can be a valuable tool for manufacturers, brand owners, and polymer engineers to model and anticipate different polymer properties associated with the increased use of PCRPE.

... Tensile tests of Fused Deposition Modeling (FDM) printed ABS specimens were performed for model calibration and estimation of random field parameters on experimental data. Specimen geometry was chosen according to ASTM D638 specimen type IV [38] with a specimen thickness of 4 mm. Three specimens were printed with an infill density of 50 % and a hexagonal infill pattern (see Figure 6a). ...

Simulations quantifying the uncertainty in structural response and damage evolution require accurate representation of the randomness of the underlying material stiffness and strength behaviors. In this paper, the mean and variance descriptions of variability of strength and stiffness of additively manufactured composite specimens are augmented with random field correlation descriptors that represent the process dependence on the property heterogeneity through microstructure variations. Two correlation lengths and a rotation parameter are introduced into randomized stiffness and strength distribution fields to capture the local heterogeneities in the microstructure of Additively Manufactured (AM) composites. We formulated a simulation and Artificial Intelligence (AI)-based technique to calibrate the correlation length and rotation parameter measures from relatively few samples of experimentally obtained strain field observations using Digital Image Correlation (DIC). The neural networks used for calibrating the correlation lengths of Karhunen-Loève Expansion (KL expansion) from the DIC images are trained using simulated stiffness and strength fields that have known correlation coefficients. A virtual DIC filter is used to add the noise and artifacts from typical DIC analysis to the simulated strain fields. A Deep Neural Network (DNN), whose architecture is optimized using Efficient Neural Architecture Search (ENAS), is trained on 150,000 simulated DIC images. The trained DNN is then used for calibration of KL expansion correlation lengths for additively manufactured composite specimens. The AM composites are loaded in tension and DIC images of the strain fields are generated and presented to the DNNs, which produce the correlation coefficients for the random fields as outputs. Compared to classical optimization methods to calibrate model parameters iteratively, neural networks, once trained, efficiently and quickly predict parameters without the need for a robust simulator and optimization methods.

... Modification of the manufacture of composites by mixing the matrix with fiber, 70 g of matrix moistened with 20 ml of 0.25% BPO, stirred until homogeneous over the entire surface of the matrix, 30 g of filler was moistened with 20 ml of 2.5% MAH. Furthermore, the matrix and filler are mixed and stirred until homogeneous, then the mold is put in a compression mold to obtain a composite specimen of ASTM D-638 type IV [8]. Composite quality tests carried out include Tensile Strength, SEM, and DSC. ...

Zulnazri Zulnazri
W Atmaja
S Maliki
C Ramadhan

This study examines the composite quality of PP and HDPE plastic waste materials using Microfiber Oil palm empty fruit bunches (OPEFB) as filler, the fiber used is 90 µm. The ratio of matrix: filler used is 60:40 and 70:30 for each type of PP and HDPE polymer. The method used is a melt blending screw extruder, where plastic and fiber materials are dissolved with a compatibilizer and then melt blended in an extruder by providing temperatures of 160 and 170 oC. Tensile tests showed the strength of the PP composite with a filler ratio of 60:40 and 70:30, respectively, of 313.25 N and 336.35 N, while the HDPE composite with a filler ratio of 60:40 and 70:30, respectively are 392.93 N and 187.90 N. The maximum force required to break HDPE composites reaches 21.10 Mpa while for PP composites it reaches 18.56 Mpa. From the morphology of the PP and HDPE composite samples, the overall surface structure of HDPE looks regular with a width from 1 to 13.5 mm. The PP composite shows a uniform and regularly arranged surface structure and the bond between the fibers and the filler looks more compatible but the surface pores are rougher. Heat resistance can be seen from the melting point of PP composites which can reach 163.81oC while HDPE composites only reach 134.21oC.

Sang-U Bae
Young-Rok Seo
Birm-June Kim
Min Lee

Fused deposition modeling (FDM) 3D printing technology is the most common system for polymer additive manufacturing (AM). Recent studies have been conducted to expand both the range of materials that can be used for FDM and their applications. As a filler, wood flour was incorporated into poly lactic acid (PLA) polymer to develop a biocomposite material. Composite filaments were manufactured with various wood flour contents and then successfully used for 3D printing. Morphological, mechanical, and biodegradation properties of FDM 3D-printed PLA composites were investigated. To mitigate brittleness, 5 phr of maleic anhydride grafted ethylene propylene diene monomer (MA-EPDM) was added to the composite blends, and microstructural properties of the composites were examined by scanning electron microscopy (SEM). Mechanical strength tests demonstrated that elasticity was imparted to the composites. Additionally, test results showed that the addition of wood flour to the PLA matrix promoted pore generation and further influenced the mechanical and biodegradation properties of the 3D-printed composites. An excellent effect of wood flour on the biodegradation properties of FDM 3D-printed PLA composites was observed.

siti noor hidayah binti Mustapha
wan joe shin

The objective of this work was to develop a plastic film from food sources with excellent thermal, mechanical, and degradability performance. Corn starch (CS)/nata de coco (NDC) were hybridized with addition of glycerin as plasticizer at different weight ratio and weight percent, respectively. Sample analysis found that the hybridization of CS with NDC improved the film forming properties, mechanical and thermal, degradation properties, as well as hydrophobicity and solubility of the film up to 0.5:0.5 wt. hybrid ratio. The properties of the films were highly affected by the homogeneity of the sample during hybridization, with high NDC amount (0.3:0.7 wt. CS:NDC) showing poor hydrophobicity, and mechanical and thermal properties. The glycerin content, however, did not significantly affect the hydrophobicity, water solubility, and degradability properties of CS/NDC film. Hybridization of 0.5:0.5 wt. CS/NDC with 2 phr glycerin provided the optimum Young's modulus (15.67 MPa) and tensile strength (1.67 MPa) properties.

William King
Gary L. Bowlin

Near-field electrospinning (NFES) is a direct fiber writing sub-technique derived from traditional electrospinning (TES) by reducing the air gap distance to the magnitude of millimeters. In this paper, we demonstrate a NFES device designed from a commercial 3D printer to semi-stably write polydioxanone (PDO) microfibers. The print head was then programmed to translate in a stacking grid pattern, which resulted in a scaffold with highly aligned grid fibers that were intercalated with low density, random fibers. As the switching process can be considered random, increasing the grid size results in both a lower density of fibers in the center of each grid cell as well as a lower density of "rebar-like" stacked fibers. These scaffolds resulted in tailorable as well as greater surface pore sizes as given by scanning electron micrographs and 3D permeability as indicated by fluorescent microsphere filtration compared to TES scaffolds of the same fiber diameter. Furthermore, ultimate tensile strength, percent elongation, yield stress, yield elongation, and Young's modulus were all tailorable compared to the static TES scaffold characterization. Lastly, the innate immune response of neutrophil extracellular traps (NETs) was attenuated on NFES scaffolds compared to TES scaffolds. These results suggest that this novel NFES scaffold architecture of PDO can be highly tailored as a function of programming for a variety of biomedical and tissue engineering applications.

Ashirbad Jana
Senthilvelan Selvaraj
Kanagaraj Subramani

Life of a metal on ultra‐high molecular weight polyethylene (UHMWPE) total hip replacement is often limited to 10–15 years, due to wear loss and aseptic loosening. Due to its high melt flow index, UHMWPE is typically processed by ram extrusion or compression molding technique, but yet to be processed to the full potential of its mechanical integrity in acetabular shape without any fusion defects or weak bonding. The main objective of the present study is to develop a novel technique to fabricate defect‐free acetabular cups with desired bearing characteristics and surface finish by sintering medical‐grade UHMWPE GUR 1050 powder after its cold isostatic compaction with optimum processing parameters. Sintering kinetics of UHMWPE is studied comprehensively using a thermomechanical analyzer. The influence of compaction pressure, sintering temperature, and sintering duration on sintering kinetics of UHMWPE is explored to realize their optimum. The optimally processed UHMWPE has the relative density of 97% and Vickers hardness of 5.4 with tensile yield strength and elastic modulus of 21.5 and 625 MPa, respectively. The newly developed acetabular cup exhibited inherent plateau‐finished bearing surface with an average surface roughness of <100 nm, having good bearing characteristics and desired dimension. (I) 3D model of sintering kinetics of UHMWPE. (II) Novel technique for manufacturing of UHMWPE acetabular cup. (III) Developed UHMWPE acetabular cup and the inherent features of its bearing surface.

Fused Deposition Modelling (FDM) is the most common 3D printing technology. An object formed through continuous layering until completion is known as an additive process while other processes with different methods are also relevant. In this paper, mechanical properties were analysed using two distinct kinds of printed polyethylene terephthalate (PET) as tensile test specimens. The materials used consist of recycled PET and virgin PET. An assessment of all the forty test pieces of both kinds of PET was undertaken. A comparison of the test samples' tensile strength values, difference in stress-strain curves, and elongation at break was also carried out. The reasoning behind the fracturing of test pieces that printed with different settings is presented in part by the depiction of the fractured specimens following the tensile test. An optimal route was revealed to be 3D printing with recycled PET, as per the mechanical testing. The hardness of the recycled filament decreased to 6%, while the tensile strength and shear strength increased to 14.7 and 2.8%, respectively. Nonetheless, no changes occurred to the tensile modulus elasticity. Despite notable differences being observed in the results of the recycled PET filament, no substantial differences were found prior or post-recycling in the mechanical properties of the PET filament. In conclusion, the demand for improved recycled 3D printing filament technologies is heightened due to the comparable mechanical features of the specimens of both the 3D printed recycled and virgin materials. With tensile strength figures reaching as high as 43.15MPa at Recycled PET and 3.12% being the greatest elongation at 40% Recycled PET, 100% Recycled is the ideal printing setting.

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Source: https://www.researchgate.net/publication/330713593_Standard_Test_Method_for_Tensile_Properties_of_Plastics_1

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