ASTM D5034

What the test does

A 100 mm wide fabric strip is clamped between two pairs of jaws set 75 mm apart, but the jaw faces are only 25 mm wide, so just a central band of the fabric is actually held. One clamp moves at constant speed until the fabric ruptures. Peak force and the extension at that point are recorded, giving grab breaking force and elongation.

What it measures, and why it matters

The method reports breaking force in newtons and elongation at that force, separately for warp and filling directions because the two rarely match. Buyers write grab strength into apparel, upholstery, geotextile and protective-clothing specifications, so the number functions as a lot-release gate rather than a design constant. It also ranks candidate constructions during sourcing and diagnoses process faults — a filling-direction drop after a finishing change points at fibre damage in the range. Elongation flags fabrics too extensible for their intended seam or frame.

Strip, jaws and directions

Specimen width

100 mm

Jaw face width

25 mmTHE DEFINING FEATURE. Only a central band is held, and the surrounding fabric shares load through the weave — which is why a grab result is always higher than a strip result on the same cloth.

Gauge length

75 mm between jaws

Both directions

Warp AND filling, reported separatelyThey rarely match, and a single figure does not describe a woven fabric.

Specimen spacing

No two specimens sharing warp or filling yarnsOtherwise the replicates are not independent and the standard deviation is meaningless.

Conditioning

Textile standard atmospherePracticeConditioned to Practice D1776/D1776M, named in this method's referenced documents; the retrievable D1776 record prints no figures, so none are quoted here.

Test speed

Rate

300 mm/minConstant rate of extension.

Recorded

Peak force and the extension at that peak

Calculations

How the test runs

1. 01Condition the fabric in the textile standard atmosphere.
2. 02Cut 100 mm wide specimens in both the warp and filling directions.
3. 03Space specimens so no two share the same yarns.
4. 04Set the jaw faces 25 mm wide and the gauge length at 75 mm.
5. 05Clamp the strip centrally so the held band is in the middle of its width.
6. 06Run at 300 mm/min to rupture.
7. 07Record peak force and the extension at that peak.
8. 08Note where the break occurred; discard a break at the jaw line.
9. 09Repeat for the replicate count and report warp and filling separately.

Grips and fixtures for this method

Rubber facedTJ-34

25mm Square Vice Action Grip

Square vice-action faces 25 mm wide — the exact jaw width the grab method defines, which is the geometry rather than a convenience.

Specifications

Standard 25 mm

Pneumatic Vice Action Grip

Air-driven closure applies identical pressure to every specimen, removing operator grip force as a variable across a long run of replicates.

Specifications

What the report has to contain

• Reference to ASTM D5034
• Fabric identification, construction and finish
• DIRECTION for every result — warp or filling
• Specimen width and gauge length
• Jaw face width
• Conditioning atmosphere
• Rate of extension
• Grab breaking force in newtons
• Elongation at breaking force
• Number of specimens per direction, mean and standard deviation

What the machine must be capable of

The clamped band is narrow, so grab forces sit well below full-width strip values. Most apparel, upholstery and nonwoven fabrics break between roughly 100 N and 1,2 kN, and a 500 N to 1 kN capacity meets most buyer specifications; heavy coated and industrial fabrics push the demand towards 5 kN. The method calls for a constant-rate-of-extension frame at 300 mm/min ±10 mm/min unless a material specification says otherwise. Textiles are rate-sensitive, so a frame that overshoots on acceleration or cannot hold speed under falling load will bias the peak.

No extensometer is required — elongation is taken from crosshead travel over the 75 mm gauge separation, which is why that separation must be set accurately. The fixture is the method: grab clamps with unequal faces, 25 × 25 mm at the front and 25 × 50 mm behind, faced with rubber around 1,5 mm thick or similar so the fabric is held without being cut. Ordinary flat wedge grips clamp the full width and give strip results, not grab results, which are not comparable. Testing outside the standard atmosphere needs a conditioned room or chamber; wet testing needs immersion facilities beside the frame.

What goes wrong in practice

Jaw breaks dominate: the fabric fails at the clamp line rather than in the free band, usually from over-tightening or worn facings, and the recorded force is low. Slippage is the mirror fault — the fabric creeps out under load, inflating elongation and flattening the curve. Off-centre mounting puts the 25 mm band away from the marked line, so the surrounding yarns share load unevenly. Fabrics stretching beyond about 11 % fall outside the method's recommended scope, and the result loses meaning rather than merely losing precision.

Grab or strip

Two fabric tensile methods that give different numbers on the same cloth, on purpose.

A grab figure and a strip figure are not two measurements of one property. The grab test lets surrounding fabric share the load, which is closer to how a garment or geotextile actually carries force — and it is why the two must never be compared or substituted in a specification.

Questions we are asked about this test