ASTM D4964 Tensile Fixture – Universal Grip Data Sheet (PDF)
Introduction
ASTM D4964 is the standard test method for tension and elongation of elastic fabrics on a constant-rate-of-extension (CRE) universal testing machine. It covers wide and narrow elastic fabrics made with natural or man-made elastomers, alone or blended with other yarns: waistbands, narrow elastics, compression garments, activewear, shapewear and medical wraps.
Unlike a strip tensile test, the specimen is sewn into a loop and stretched around two round bars, and it is cycled three times so the results show how the fabric behaves once it has been worked in. The values to report are agreed between buyer and seller. Results are not comparable with ASTM D1775, which runs the same kind of test on a constant-rate-of-load (CRL) tester.
What the Test Measures
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Loop tension at specified elongations (commonly 30%, 50% and 70%), read from the extending part of the third cycle.
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Elongation at a specified loop tension (commonly the 100 N / 20 lbf cycle limit), read from the loading part of the third cycle.
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Optional recovery curves for each cycle or for the third cycle only.
Equipment
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CRE tensile tester with a force–extension recorder and cycling controls, and a low-capacity load cell suited to a 100 N (20 lbf) cycle limit.
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Two band clamps (anvils): round bars 13.0 ± 0.25 mm (0.5 in) or 6.5 ± 0.25 mm (0.25 in) in diameter and at least 76 mm (3 in) long. The loop wraps around the bars; flat-faced jaw grips are not used.
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Single-needle sewing machine to close the loop.
Specimen Preparation
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Wide fabrics: cut specimens 350 × 100 mm (14 × 4 in) and trim or ravel them to 75 ± 2 mm (3 in) wide. Take five specimens per test direction along a diagonal of the swatch, no closer to the selvage than one tenth of the fabric width.
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Narrow fabrics: cut five specimens 350 mm (14 in) long at the full fabric width.
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Mark two gauge lines 250 ± 2 mm (10 in) apart, fold the strip into a loop and sew along the marks with two rows of single-needle stitching. The loop circumference around the bars is 250 mm.
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Relax the specimens free of tension for at least 16 hours, then condition and test them in the standard textile atmosphere of ASTM D1776 (21 ± 2 °C, 65 ± 5% RH).
Test Procedure
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Set the bars so the 250 mm loop is just snug: 118 mm (4.7 in) from the top of the upper bar to the bottom of the lower bar with 13 mm bars, or 121 mm (4.9 in) with 6.5 mm bars.
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Set the crosshead to 500 ± 15 mm/min (20 in/min) for loading and unloading. For fabrics with less than 100% elongation, 300 mm/min may be agreed.
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Set the cycle limit, usually 100 N (20 lbf) maximum force, or an agreed extension.
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Run three load–unload cycles and record at least the third cycle.
Calculations
Because the loop has two layers between the bars, crosshead travel is half the change in loop circumference. To read the tension at a given elongation, first convert that elongation to extension:
L = (E × C) ÷ 200
where L is the extension in mm, E is the elongation in % and C is the loop circumference (250 mm).
Example: for 50% elongation on a 250 mm loop, L = (50 × 250) ÷ 200 = 62.5 mm. Read the loop tension at 62.5 mm on the extending curve of the third cycle.
Reporting
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Fabric description and test direction
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Bar diameter, rate of extension and cycle limit (machine set-up must be reported, because different set-ups give different results)
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Loop tension at each specified elongation and/or elongation at the specified tension, from the third cycle
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Number of specimens and any deviations from the method
Band Clamps for ASTM D4964
Universal Grip supplies band clamps with 13 mm and 6.5 mm bars that mount to standard universal testing machine clevises. Contact us for the bar size, length and adapters that match your tester and fabric width.
Related Standards
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ASTM D1775 – tension and elongation of elastic fabrics on a CRL tester
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ASTM D1776 – conditioning and testing textiles
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ASTM D2594 – stretch properties of knitted fabrics with low power
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ASTM D3107 – stretch properties of fabrics woven from stretch yarns
ASTM D4964 FAQ
What test speed does ASTM D4964 use?
500 ± 15 mm/min (20 in/min) for both loading and unloading. For fabrics with less than 100% elongation, buyer and seller may agree on 300 ± 15 mm/min (12 in/min).
What is the ASTM D4964 specimen?
A 350 mm (14 in) strip, 75 mm (3 in) wide for wide fabrics or full width for narrow elastics, sewn into a loop with a 250 mm (10 in) circumference and mounted over two round bars (band clamps).
How many cycles does ASTM D4964 require?
Three load–unload cycles. Loop tension and elongation are read from the third cycle, after the fabric has been worked in.
How do you convert elongation to crosshead extension?
Use L = (E × C) ÷ 200, where E is elongation in % and C is the loop circumference. On a 250 mm loop, 30%, 50% and 70% elongation correspond to 37.5, 62.5 and 87.5 mm of crosshead travel.
For other fabric tests on a universal testing machine, read our guide to textile testing on a universal testing machine.
