Tensile strength is the maximum force a fabric can take when pulled in one direction before it breaks. It is the basic strength test for woven fabrics and is usually measured separately in the warp and weft directions.
Strip and grab methods#
| Method | How the specimen is held | Standards |
|---|---|---|
| Strip | The full width of a narrow strip is clamped. For some fabrics, yarns are removed from the edges to get an exact width (ravelled strip). | ISO 13934-1, ASTM D5035 |
| Grab | Only the center part of a wider specimen is gripped, so neighbouring yarns also help carry load | ISO 13934-2, ASTM D5034 |
Grab results are usually higher than strip results for the same fabric, because more yarns contribute. The two are not interchangeable.
How the test works (principle)#
- Specimens are cut in the warp and weft directions, conditioned in a standard atmosphere.
- Each specimen is clamped in the jaws of a tensile tester at a set gauge length.
- The tester pulls at a constant rate of extension until the specimen breaks.
- The maximum force (N) and the elongation at maximum force (%) are recorded.
- Several specimens are tested in each direction and the average is reported.
Breaks at the jaws are usually recorded separately or rejected, as the method describes.
Reading a result#
| Direction | Maximum force (N) | Elongation (%) |
|---|---|---|
| Warp | 620 | 18 |
| Weft | 410 | 22 |
The weft is often weaker than the warp in many shirting and bottom-weight fabrics, because warp yarns are usually stronger (sized, higher twist) and more numerous per inch. The buyer's requirement usually gives a minimum force for each direction.
What affects tensile strength#
- Yarn strength and count: stronger, coarser yarns give higher strength.
- Threads per inch: more yarns in the direction tested increase strength.
- Weave: the weave affects how yarns share load.
- Fiber: polyester blends are generally stronger than 100% cotton of similar construction.
- Processing damage: over-bleaching, strong acid or enzyme treatments, resin finishes (such as easy-care finishes on cotton) and harsh garment washing can reduce strength.
Related tests#
- Tear strength (ISO 13937 series, ASTM D1424 and others): force needed to continue a tear.
- Seam strength and seam slippage: how seams hold. See seam strength.
- Bursting strength: used for knits. See bursting strength.
When results are low#
- Check the fabric construction (EPI, PPI, counts) against the specification. See fabric construction analysis.
- Review finishing: resin finish level, curing, bleaching and washing processes.
- Test greige and finished fabric to see where strength was lost.
Related guides#
- ISO, ASTM and AATCC test methods: strip and grab methods by standard.
- Fabric testing standards and methods: strength tests within the full test program.
- Different types of fabric for dresses and clothing: the woven fabrics most often tested for tensile strength.
Frequently asked questions#
Why test warp and weft separately? Yarns, counts and densities often differ in the two directions, so strength does too.
Are grab and strip results convertible? No reliable conversion exists. Report the method used, and compare results only within the same method.
Should wet strength be tested? Some buyers require it for fabrics such as viscose, where wet strength is much lower than dry strength.
What elongation is normal? It varies widely with fiber, yarn and weave. Stretch wovens with elastane show much higher elongation than rigid cotton fabrics.