Tensile strength measures the force needed to pull a strip of woven fabric apart, and tear strength measures the force needed to continue a cut that has already started. Tensile is usually tested under ISO 13934 or ASTM D5034, and tear under ISO 13937 or the ASTM D1424 Elmendorf method. Both are reported separately for warp and weft, because a woven fabric is rarely equally strong in both directions.
For a buyer, these two numbers predict different failures. Low tensile strength shows up as seams and stress points giving way. Low tear strength shows up as a small snag at a pocket corner running into a long rip. A fabric can pass one and fail the other, so it is worth specifying both. Together they also show whether the mill used the yarn it quoted.
Tensile testing
In the strip method under ISO 13934-1, a specimen of fixed width is clamped at both ends and pulled at a constant rate until it breaks. The machine records the breaking force in newtons and the elongation at break as a percentage. The grab method, ISO 13934-2 and ASTM D5034, clamps only the centre of a wider specimen and gives higher readings, so results from the two methods cannot be compared with each other.
Results are affected by yarn count, thread density, weave and finish. A heavier, tighter construction is usually stronger, but harsh finishing such as heavy resin for wrinkle resistance can reduce tensile strength noticeably.
Tear testing
- Elmendorf (ISO 13937-1, ASTM D1424): a pendulum swings through a pre-slit specimen and the energy lost is converted to tear force. It is quick and common for shirting and bottom weights.
- Tongue or trouser tear (ISO 13937-2, ASTM D2261): a slit specimen is pulled apart on a tensile machine. It suits heavier fabrics beyond the pendulum's capacity.
- Wing and trapezoid methods: used for some technical and coated fabrics, and less common for apparel.
What to write in your specification
State the method and the minimum value for each direction, and make sure the method matches your reference fabric's test report. Set minimums with a margin, because finishing and dyeing can reduce strength between greige and finished fabric. Ask for testing after any resin or softener finish, not before, since that is the fabric you will actually receive.
Very light shirting and open-weave fabrics will not reach the numbers a denim does, and demanding denim figures on a lawn only produces failures. Compare against the construction you are buying, and use the figures from your approved sample as the baseline.
How we check strength before loading
We take sealed samples from the finished bulk and send them to an NABL-accredited lab for tensile and tear in both directions, then compare the figures with your specification before we supervise loading. If a mill's own numbers look optimistic, we say so. A free 20-minute sourcing review is the easiest way to decide which tests your product actually needs.