ASTM D1388-96e1
(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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e1
Designation: D 1388 – 96
Standard Test Method for
Stiffness of Fabrics
This standard is issued under the fixed designation D 1388; 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 (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Table 4 was corrected editorially in September 1999.
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 Option A—Cantilever Test, employing the principle of
interaction between fabric weight and fabric stiffness as shown
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.
woven fabrics, air bag fabrics, blankets, napped fabrics, 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.
either end of a strip of unit width bent into unit curvature in the
2. Referenced Documents absence of any tension.
3.1.5 machine direction, MD, n—the direction in the plane
2.1 ASTM Standards:
of the fabric parallel to the direction of manufacture.
D 123 Terminology Relating to Textiles
3.1.5.1 Discussion—The term machine direction is used to
D 1776 Practice for Conditioning Textiles for Testing
refer to the direction analogous to walewise or warp direction
D 2904 Practice for Interlaboratory Testing of a Textile Test
2 in knitted or woven fabrics, respectively.
Method That Produces Normally Distributed Data
3.1.6 stiffness, n—resistance to bending.
D 2906 Practice for Statements on Precision and Bias for
2 3.1.7 For definitions of other textile terms used in this test
Textiles
method, refer to Terminology D 123.
D 3776 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
its leading edge projects from the edge of a horizontal surface.
The length of the overhang is measured when the tip of the
specimen is depressed under its own mass to the point where
This test method is under the jurisdiction of ASTM Committee D13 on Textiles
the line joining the top to the edge of the platform makes a
and is the direct responsibility of Subcommittee D13.60 on Fabric Test Methods,
Specific.
Current edition approved April 10, 1996. Published June 1996. Originally
published as D 1388 – 56 T. Discontinued 1995 and reinstated as D 1388 – 96. PC programs on floppy disks for analyzing Committee D-13 interlaboratory
Annual Book of ASTM Standards, Vol 07.01. data are available through ASTM. For 3 ⁄2 in. disks request PCN: 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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D 1388
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—A strip 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
acceptance testing.
5.1.1 In case of a dispute arising from differences in
FIG. 1 Example of a Motorized Cantilever Test Apparatus
reported test results when using this test method for acceptance
testing of commercial shipments, the purchaser and the sup-
plier should conduct comparative tests to determine if there is 6.1.1.2 Movable Slide, consisting of a metal bar not less
a statistical bias between their laboratories. Competent statis- than 25 by 200 mm (1 by 8 in.) by approximately 3 mm ( ⁄8 in.)
tical assistance is recommended for the investigation of bias. thick and having a mass of 270 6 5 g (0.6 6 0.01 lb).
As a minimum, the two parties should take a group of test 6.1.1.3 Scale and Reference Point, to measure the length of
specimens that are as homogeneous as possible and that are the overhang.
from a lot of material of the type in question. Test specimens 6.1.1.4 Specimen Feed Unit, motorized (see Fig. 1) set to
should then be randomly assigned in equal numbers to each 120 mm/min (4.75 in./min) 65 %, or manual equivalent.
laboratory for testing. The average results from the two 6.1.2 Cutting Die—25 6 1mmby200 6 1mm(1 6 0.04
laboratories should be compared using the appropriate statis- in. by 8 6 0.04 in.).
tical analysis and an acceptable probability level chosen by the 6.2 Option B—Heart Loop Tester.
two parties before testing is begun. If a bias is found, either its
6.2.1 Clamp and Stand, for hanging the specimen.
cause must be found and corrected or the purchaser and the 6.2.2 Scale, suitably mounted on the stand for measuring the
supplier must agree to interpret future test results with consid-
length of the specimen loop and calibrated either in cm (in.) or
eration to the known bias. directly in bending length.
5.2 In general, these procedures are more suitable for testing
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 3 3 3 0.1256 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
with their inner edges parallel and at a distance from each other
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.
randomly select the number of rolls or pieces of fabric directed
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
provided at the edge. Consequently, the wider the strip, the less
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
6.1 Option A—Cantilever Bending Tester (Fig. 1 and Figs. 2 purchaser and supplier requires taking into account the variability between
rolls or pieces of fabric and between specimens from a swatch from a roll
).
or piece of fabric to provide a sampling plan with a meaningful producer’s
6.1.1 Horizontal Platform, with a minimum area of 38 by
risk, consumer’s risk, acceptable quality level, and limiting quality level.
200 mm (1.5 by 8 in.) and having a smooth low-friction, flat
surface such as polished metal or plastic. A leveling bubble
shall be incorporated in the platform.
A motorized bending tester such as described in Section 6.1 and Fig. 1 is being
6.1.1.1 Indicator, inclined at an angle of 0.724 6 0.01 rad
developed. Contact Instrument Marketing Services, a subsidiary of U.S. Testing
(41.5 6 0.5°) below the plane of the platform surface. Company, Inc., 291 Fairfield Avenue, Farfield, NJ 07004.
NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 1388
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
5.2 1.56 3.03 4.71
7.2 Laboratory Sample—For acceptance testing, take a
5.4 1.45 2.90 4.53
swatch extending the width of the fabric and approximately 1
5.6 1.35 2.80 4.36
m (1 yd) along the machine direction from each roll or piece in
5.8 1.25 2.67 4.20
the lot sample. For rolls of fabric, take a sample that will 6.0 1.14 2.57 4.06
6.2 1.04 2.47 3.92
exclude fabric from the outer wrap of the roll or the inner wrap
6.4 0.93 2.37 3.80
around the core of the roll of fabric, or any end piece.
6.6 0.81 2.26 3.67
6.8 0.69 2.16 3.56
7.3 Direction of Test—Consider the long dimension of the
7.0 0.53 2.06 3.45
specimen as the direction of test.
7.2 . 1.96 3.34
7.4 Number of Test Specimens—From each laboratory sam-
7.4 . 1.86 3.21
7.6 . 1.76 3.12
pling unit, take four specimens from the machine direction and
7.8 . 1.66 3.02
four specimens from the cross-machine direction as applicable
8.0 . . 2.91
to a material specification or contract order.
8.2 . . 2.82
8.4 . . 2.72
7.5 Cutting Test Specimens—Cut the specimens to be used
for the measurement of machine direction with the longer
dimension parallel to the machine direction. Cut the specimens
8. Preparation of Test Apparatus and Calibration
to be used for the measurement of the cross-machine direction
8.1 Option A—Cantilever Test:
with the longer dimension parallel to the cross-machine direc-
8.1.1 Set the tester on a table or bench with the horizontal
tion. Label to maintain specimen identity.
platform and inclined reference lines. Adjust the platform to
7.5.1 Take specimens, representing a broad distribution
horizontal as indicated by the leveling bubble.
across the width and length, preferably along the diagonal of
8.1.2 Verify that the bend angle indicator is at the 0.724 rad
the laboratory sample, and no nearer the edge than one-tenth its
(41.5°) angle marked on the scale.
width. Ensure specimens are free of folds, creases, or wrinkles.
Avoid getting oil, water, grease, etc. on the specimens when
9. Conditioning
handling.
9.1 Precondition the specimens by bringing them to ap-
7.5.2 Cantilever Test—Cut test specimens 25 by 200 mm,
proximate moisture equilibrium in the standard atmosphere for
61mm(1by8in. 6 0.04 in.).
preconditioning textiles as directed in Practice D 1776, unless
7.5.3 Heart Loop Test—No standard size for the test speci-
otherwise directed in a material specification or contract order.
men is required. Cut test specimens 50 mm (2 in.) longer than
9.2 After preconditioning, bring the test specimens to mois-
the selected strip length to allow for clamping at the ends. See
ture equilibrium for testing in the standard atmosphere for
Table 2.
testing textiles as directed in Practice D 1776 or, if applicable,
7.5.3.1 Select a specimen width at least 25 mm (1 in.) and
in the specified atmosphere in which the testing is to be
no more than 75 mm (3 in.) with respect to the tendency of the
performed, unless otherwise directed in a material specification
fabric to curl. For fabrics having a slight tendency to curl, a 25
or contract order.
6 1mm(1 6 0.04 in.) wide specimen has been found to be
satisfactory. As the tendency to curl becomes greater, increase
10. Procedure
the width up to a maximum of 75 mm (3 in.).
10.1 Test the conditioned specimens in the standard atmo-
7.5.3.2 Make several trial tests using various strip lengths
sphere for testing textiles, which is 21 6 1°C (70 6 2°F) and
selected from Table 2. Select a suitable strip length for a
65 6 2 % relative humidity, unless otherwise directed in a
corresponding loop length from Table 2, such that the bending
material specification or contract order.
length is relatively independent of strip length.
10.2 Option A—Cantilever Test:
NOTE 3—Strip length is the circumferential length of the unclamped
10.2.1 Remove the movable slide. Place the specimen on
portion of the specimen.
the horizontal platform with the length of the specimen parallel
NOTE 4—Specimen strip widths greater than 75 mm (3 in.) have not
to the platform edge. Align the edge of the specimen with the
been investigated and are not recommended since reliability of results are
line scribed on the right-hand edge of the horizontal platform.
questionable.
NOTE 5—The bending length using the heart loop option is not entirely NOTE 6—When known, place the specimen face-side up.
independent of the strip length. In general, the bending length rises
...
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