ASTM D1388-96(2002)
(Test Method)Standard Test Method for Stiffness of Fabrics
Standard Test Method for Stiffness of Fabrics
SCOPE
1.1 This test method covers the measurement of stiffness properties of fabrics. Bending length is measured and flexural rigidity is calculated. Two procedures are provided.
1.1.1 Option A—Cantilever Test, employing the principle of cantilever bending of the fabric under its own mass.
1.1.2 Option B—Heart Loop Test, employing the principle of a loop formed in a fabric strip and hung vertically.
1.2 This test method applies to most fabrics including woven fabrics, air bag fabrics, blankets, napped fabrics, knitted fabrics, layered fabrics, pile fabrics. The fabrics may be untreated, heavily sized, coated, resin-treated, or otherwise treated.
1.3 The values stated in SI units are to be regarded as the standard. The U.S. customary units may be approximate.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:D1388–96 (Reapproved 2002)
Standard Test Method for
Stiffness of Fabrics
This standard is issued under the fixed designation D1388; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope TEX-PAC
1.1 This test method covers the measurement of stiffness
3. Terminology
properties of fabrics. Bending length is measured and flexural
3.1 Definitions:
rigidity is calculated. Two procedures are provided.
3.1.1 bending length, n—in textiles, a measure of the
1.1.1 OptionA—CantileverTest,employingtheprincipleof
interactionbetweenfabricweightandfabricstiffnessasshown
cantilever bending of the fabric under its own mass.
by the way in which a fabric bends under its own weight.
1.1.2 Option B—Heart Loop Test, employing the principle
3.1.1.1 Discussion—Bending length reflects the stiffness of
of a loop formed in a fabric strip and hung vertically.
a fabric when bent in one plane under the force of gravity and
1.2 This test method applies to most fabrics including
is one component of drape.
wovenfabrics,airbagfabrics,blankets,nappedfabrics,knitted
3.1.2 cross-machine direction, CD, n—the direction in the
fabrics, layered fabrics, pile fabrics. The fabrics may be
plane of the fabric perpendicular to the direction of manufac-
untreated, heavily sized, coated, resin-treated, or otherwise
ture.
treated.
3.1.2.1 Discussion—The term cross-machine direction is
1.3 The values stated in SI units are to be regarded as the
used to refer to the direction analogous to coursewise or filling
standard. The U.S. customary units may be approximate.
direction in knitted or woven fabrics, respectively.
1.4 This standard does not purport to address all of the
3.1.3 fabric, n—in textiles, a planar structure consisting of
safety concerns, if any, associated with its use. It is the
yarns or fibers.
responsibility of the user of this standard to establish appro-
3.1.4 flexural rigidity, n—a measure of stiffness, where two
priate safety and health practices and determine the applica-
equal and opposite forces are acting along parallel lines on
bility of regulatory limitations prior to use.
eitherendofastripofunitwidthbentintounitcurvatureinthe
2. Referenced Documents absence of any tension.
3.1.5 machine direction, MD, n—the direction in the plane
2.1 ASTM Standards:
2 of the fabric parallel to the direction of manufacture.
D123 Terminology Relating to Textiles
3.1.5.1 Discussion—The term machine direction is used to
D1776 Practice for Conditioning Textiles for Testing
refer to the direction analogous to walewise or warp direction
D2904 PracticeforInterlaboratoryTestingofaTextileTest
in knitted or woven fabrics, respectively.
Method That Produces Normally Distributed Data
3.1.6 stiffness, n—resistance to bending.
D2906 Practice for Statements on Precision and Bias for
3.1.7 For definitions of other textile terms used in this test
Textiles
method, refer to Terminology D123.
D3776 Test Methods for Mass Per Unit Area (Weight) of
Woven Fabric
4. Summary of Test Method Options
2.2 ASTM Adjuncts:
4.1 Option A, Cantilever Test—A specimen is slid at a
specified rate in a direction parallel to its long dimension, until
1 its leading edge projects from the edge of a horizontal surface.
ThistestmethodisunderthejurisdictionofASTMCommitteeD13onTextiles
and is the direct responsibility of Subcommittee D13.60 on Fabric Test Methods, The length of the overhang is measured when the tip of the
Specific.
Current edition approved Sept. 10, 2002. Published June 1996. Originally
published as D1388–56T. Discontinued 1995 and reinstated as D1388–96. PC programs on floppy disks for analyzing Committee D-13 interlaboratory
Annual Book of ASTM Standards, Vol 07.01. dataareavailablethroughASTM.For3 ⁄2in.disksrequestPCN:12-429040-18,for
Annual Book of ASTM Standards, Vol 07.02. 5 ⁄4 in. disk request PCN: 12-429041-18.
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D1388–96 (2002)
specimen is depressed under its own mass to the point where
the line joining the top to the edge of the platform makes a
0.924 rad (41.5°) angle with the horizontal. From this mea-
sured length, the bending length and flexural rigidity are
calculated.
4.2 Option B, Heart Loop Test—Astrip of fabric is formed
into a heart-shaped loop. The length of the loop is measured
when it is hanging vertically under its own mass. From this
measured length, the bending length and flexural rigidity are
calculated.
5. Significance and Use
5.1 Both test options in this test method are considered
satisfactory for acceptance testing of commercial shipments
since current estimates of between-laboratory precision are
acceptable and the method is used extensively in the trade for
FIG. 1 Example of a Motorized Cantilever Test Apparatus
acceptance testing.
5.1.1 In case of a dispute arising from differences in
6.1.1.1 Indicator, inclined at an angle of 0.724 6 0.01 rad
reportedtestresultswhenusingthistestmethodforacceptance
(41.5 6 0.5°) below the plane of the platform surface.
testing of commercial shipments, the purchaser and the sup-
6.1.1.2 Movable Slide, consisting of a metal bar not less
plier should conduct comparative tests to determine if there is
than25by200mm(1by8in.)byapproximately3mm( ⁄8in.)
a statistical bias between their laboratories. Competent statis-
thick and having a mass of 270 6 5 g (0.6 6 0.01 lb).
tical assistance is recommended for the investigation of bias.
6.1.1.3 Scale and Reference Point, to measure the length of
As a minimum, the two parties should take a group of test
the overhang.
specimens that are as homogeneous as possible and that are
6.1.1.4 Specimen Feed Unit, motorized (see Fig. 1) set to
from a lot of material of the type in question. Test specimens
120 mm/min (4.75 in./min) 65%, or manual equivalent.
should then be randomly assigned in equal numbers to each
6.1.2 Cutting Die—25 61mmby200 61mm(1 6 0.04
laboratory for testing. The average results from the two
in. by 8 6 0.04 in.).
laboratories should be compared using the appropriate statis-
6.2 Option B—Heart Loop Tester.
tical analysis and an acceptable probability level chosen by the
6.2.1 Clamp and Stand, for hanging the specimen.
two parties before testing is begun. If a bias is found, either its
6.2.2 Scale,suitablymountedonthestandformeasuringthe
cause must be found and corrected or the purchaser and the
length of the specimen loop and calibrated either in cm (in.) or
supplier must agree to interpret future test results with consid-
directly in bending length.
eration to the known bias.
5.2 Ingeneral,theseproceduresaremoresuitablefortesting
NOTE 1—If a constant strip length is adopted, the scale may be
woven fabrics than knit fabrics.
calibrated to read directly in units of bending length.
5.3 The Cantilever Test Option is the preferred procedure
6.2.3 Brass Bars, two, 25 3 75 3 3 6 0.1 mm
because it is simpler to perform. It is, however, not suitable for
(1 33 30.1256 0.005 in.).
very limp fabrics or those that show a marked tendency to curl
6.2.4 Pressure Sensitive Tape.
or twist at a cut edge.
6.2.5 Jig, constructed to allow positioning of the two bars
5.4 The Heart Loop Test Option is suitable for fabrics that
withtheirinneredgesparallelandatadistancefromeachother
show a tendency to curl or twist.
equal to the selected strip length.
5.5 Both options can provide a correlation with a subjective
evaluation of a given fabric type. That is, a higher number
7. Sampling and Test Specimens
represents a stiffer fabric.
7.1 Lot Sample—As a lot sample for acceptance testing,
5.6 The stiffness of a fabric may change with storage.
randomlyselectthenumberofrollsorpiecesoffabricdirected
5.7 No evidence has been found showing that bending
in an applicable material specification or other agreement
length is dependent on the width. The tendency for specimens
between the purchaser and the supplier. Consider the rolls or
to curl or twist will affect the result, because of the rigidity
pieces of fabric to be the primary sampling units. In the
providedattheedge.Consequently,thewiderthestrip,theless
absence of such an agreement, take the number of fabric rolls
important is the edge effect.
specified in Table 1.
6. Apparatus
NOTE 2—An adequate specification or other agreement between the
purchaserandsupplierrequirestakingintoaccountthevariabilitybetween
6.1 OptionA—CantileverBendingTester(Fig.1andFigs.2
rolls or pieces of fabric and between specimens from a swatch from a roll
).
6.1.1 Horizontal Platform, with a minimum area of 38 by
200 mm (1.5 by 8 in.) and having a smooth low-friction, flat
Amotorized bending tester such as described in Section 6.1 and Fig. 1 is being
surface such as polished metal or plastic. A leveling bubble
developed. Contact Instrument Marketing Services, a subsidiary of U.S. Testing
shall be incorporated in the platform. Company, Inc., 291 Fairfield Avenue, Farfield, NJ 07004.
D1388–96 (2002)
TABLE 1 Number of Rolls, or Pieces, of Fabric in the Lot Sample TABLE 2 Table of Bending Lengths
Number of Rolls or Pieces Bending Length, cm
Number of Rolls or Pieces in Lot Sample
Loop Length,
in Lot, Inclusive
15-cm Strip 20-cm Strip 25-cm Strip
cm
1to3 all Length Length Length
4to24 4
4.0 2.19 . .
25 to 50 5
4.2 2.07 . .
over 50 10 % to a max of 10 rolls or pieces
4.4 1.99 . .
4.6 1.86 3.44 5.43
4.8 1.76 3.30 5.16
5.0 1.65 3.17 4.91
orpieceoffabrictoprovideasamplingplanwithameaningfulproducer’s
5.2 1.56 3.03 4.71
risk, consumer’s risk, acceptable quality level, and limiting quality level.
5.4 1.45 2.90 4.53
5.6 1.35 2.80 4.36
7.2 Laboratory Sample—For acceptance testing, take a
5.8 1.25 2.67 4.20
swatch extending the width of the fabric and approximately 1 6.0 1.14 2.57 4.06
6.2 1.04 2.47 3.92
m(1yd)alongthemachinedirectionfromeachrollorpiecein
6.4 0.93 2.37 3.80
the lot sample. For rolls of fabric, take a sample that will
6.6 0.81 2.26 3.67
excludefabricfromtheouterwrapoftherollortheinnerwrap 6.8 0.69 2.16 3.56
7.0 0.53 2.06 3.45
around the core of the roll of fabric, or any end piece.
7.2 . 1.96 3.34
7.3 Direction of Test—Consider the long dimension of the
7.4 . 1.86 3.21
7.6 . 1.76 3.12
specimen as the direction of test.
7.8 . 1.66 3.02
7.4 Number of Test Specimens—From each laboratory sam-
8.0 . . 2.91
plingunit,takefourspecimensfromthemachinedirectionand
8.2 . . 2.82
four specimens from the cross-machine direction as applicable 8.4 . . 2.72
to a material specification or contract order.
7.5 Cutting Test Specimens—Cut the specimens to be used
for the measurement of machine direction with the longer
for much longer strip lengths. Whenever possible, compare fabrics in the
dimensionparalleltothemachinedirection.Cutthespecimens
range where bending length is independent of strip length.
to be used for the measurement of the cross-machine direction
with the longer dimension parallel to the cross-machine direc-
8. Preparation of Test Apparatus and Calibration
tion. Label to maintain specimen identity.
8.1 Option A—Cantilever Test:
7.5.1 Take specimens, representing a broad distribution
8.1.1 Set the tester on a table or bench with the horizontal
across the width and length, preferably along the diagonal of
platform and inclined reference lines. Adjust the platform to
thelaboratorysample,andnonearertheedgethanone-tenthits
horizontal as indicated by the leveling bubble.
width.Ensurespecimensarefreeoffolds,creases,orwrinkles.
8.1.2 Verify that the bend angle indicator is at the 0.724 rad
Avoid getting oil, water, grease, etc. on the specimens when
(41.5°) angle marked on the scale.
handling.
7.5.2 Cantilever Test—Cut test specimens 25 by 200 mm,
9. Conditioning
61mm(1by8in. 6 0.04 in.).
9.1 Precondition the specimens by bringing them to ap-
7.5.3 Heart Loop Test—No standard size for the test speci-
proximate moisture equilibrium in the standard atmosphere for
men is required. Cut test specimens 50 mm (2 in.) longer than
preconditioning textiles as directed in Practice D1776, unless
the selected strip length to allow for clamping at the ends. See
otherwise directed in a material specification or contract order.
Table 2.
9.2 After preconditioning, bring the test specimens to mois-
7.5.3.1 Select a specimen width at least 25 mm (1 in.) and
ture equilibrium for testing in the standard atmosphere for
no more than 75 mm (3 in.) with respect to the tendency of the
testing textiles as directed in Practice D1776 or, if applicable,
fabric to curl. For fabrics having a slight tendency to curl, a 25
in the specified atmosphere in which the testing is to be
61mm(1 6 0.04 in.) wide specimen has been found to be
performed,unlessotherwisedirectedinamaterialspecification
satisfactory.As the tendency to curl becomes greater, increase
or contract order.
the width up to a maximum of 75 mm (3 in.).
7.5.3.2 Make several trial tests using various strip lengths
10. Procedure
selected from Table 2. Select a suitable strip length for a
corresponding loop length from Table 2, such that the bending 10.1 Test the conditioned specimens in the standard atmo-
sphere for testing textiles, which is 21 6 1°C (70 6 2°F) and
length is relatively independent of strip length.
65 6 2% relative humidity, unless otherwise directed in a
NOTE 3—Strip length is the circumferential length of the unclamped
material specification or contract order.
portion of the specimen.
10.2 Option A—Cantilever Test:
NOTE 4—Specimen strip widths greater than 75 mm (3 in.) have not
10.2.1 Remove the movable slide. Place the specimen on
been investigated and are not recommended since reliability of results are
questionable.
thehorizontalplatformwiththelengthofthespecimenparallel
NOTE 5—The bending length using the heart loop option is not entirely
to the platform edge. Align the edge of the specimen with the
independent of the strip length. In general, the bending length rises with
line scribed on the right-hand edge of the horizontal platform.
the strip length up to a value that remains relatively constant as the strip
length is further increased.An additional rise may further be encountered NOTE 6—When known, place the specimen face-side up.
D1388–96 (2002)
10.2.2 Place the movable slide on the specimen, being 11. Calculation
careful not to change its initial position.
11.1 Option A, Length of Overhang, Individual
10.2.3 F
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