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AAFES TEST METHOD
A-19: Seam Strength For Knit Fabrics
| Issue Date: 13 Sep 1994 |
Revision Date:
08/18/2004 |
- PURPOSE AND SCOPE:
To determine strength of seams in knit fabrics. Seam failure in a
garment can occur because of either the failure of the sewing thread, leaving the fabric
intact, or fabric rupture, leaving the seam intact or both breaking at the same time.
- PRINCIPLE:
The breaking force and elongation at break required to effect
rupture of sewn seams is measured by applying force parallel to the seam.
- REFERENCE:
ASTM D 1683-93a, Standard Test Method for
Failure in Sewn Seams of Woven Fabrics.
- APPARATUS:
Tensile testing machine, constant rate of traverse (CRT), such as
Instron Model #4206.
- PROCEDURE:
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5.1 |
Cut three specimens 100 mm (4
in.) long parallel to the stitch line and 50 mm (2 in.) wide. |
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5.2 |
Condition the specimens for a
minimum of 2 hours at 21° +/- 1C (70° +- 2F) temperature and 65% +/- 2%
relative humidity. |
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5.3 |
Set the gauge at 25 mm (1 in.)
with 100 lbs. capacity tension load cell. |
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5.4 |
Set the speed at 30.5 cm (12
in.) per minute. |
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5.5 |
Place the test specimen in the
jaws. |
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5.6 |
Press "up" key on crosshead
control panel. |
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5.7 |
When the seam thread breaks,
stop the machine, and read breaking force and percent elongation at break on
the digital readout panel. Sometimes, sewing thread may not break but fabric
may rupture, or the fabric and sewing thread may break. |
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5.8 |
Return the jaws to the original
gauge length 25 mm (1 in.). |
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5.9 |
Repeat Steps 5.5 to 5.8 on the
remaining test specimens.
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- EVALUATION:
Calculate the average seam strength and percent
elongation at break of the three specimens.
- REPORT:
Report the above figure as the seam strength and percent elongation
at break of the sample tested. Seam strength can be reported in either pounds or grams. If
there was no clear seam break, also indicate nature of the failure such as fabric rupture.
_^_
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