Testing standard
ASTM D3787
Standard Test Method for Bursting Strength of Textiles—Constant-Rate-of-Traverse (CRT) Ball Burst Test
Written and technically reviewed by Dak System Inc. engineeringLast reviewed
ASTM D3787 measures the bursting strength of textiles by pushing a 25.4 mm steel ball through a clamped circle of fabric. What defines this method rather than its close relative is which member moves: here the ring clamp traverses onto a fixed ball, on a constant-rate-of-traverse machine. One figure comes out — the maximum force needed to push the ball through.
At a glance
- Test type
- Puncture & burst
- Published by
- ASTM
- Edition
- D3787-16(2020)
- Runs on
- Series 7200 and Series 9000
What the test does
A square of fabric is clamped between the halves of a grooved ring so that a circle of it a little over 44 mm across is exposed and held all the way round. The ring assembly is then driven along the axis of a polished steel ball of 25.4 mm diameter, fixed to the machine, pressing the ball into the centre of that circle. The fabric stretches over the ball's crown in every in-plane direction at once until it ruptures, and peak force is the result. What defines the method is which member moves: the clamp traverses, on a constant-rate-of-traverse machine.
What it measures, and why it matters
One figure comes out: the maximum force needed to push the ball through the clamped fabric. Displacement at rupture may be recorded as supplementary data but is not required.
That number is a proxy for how a fabric resists being pushed out of plane by a blunt object: a knee inside a knitted panel, a load in the corner of a bag, a finger through mesh. Because the ball loads every direction at once, the result is governed by the weaker yarn system and by how well the structure shares load between wales and courses — behaviour a strip test cannot show. It serves lot acceptance and the ranking of knits, nonwovens and stretch wovens with no single strong direction, rather than as a design allowable.
Specimen and clamp
- Specimen
- A square of fabricLarge enough to be gripped all the way round the ring.
- Exposed circle
- A little over 44 mm across
- Clamp
- Grooved ring halves, gripping right round the rimSlippage at the rim inflates the result, because the fabric draws in rather than stretching.
- Ball
- 25.4 mm polished steel
- Moving member
- The CLAMP traverses onto a fixed ballThis is the distinction from ASTM D6797, where the ball moves.
- Displacement
- Supplementary, not required
The fabric is stretched in every in-plane direction at once, so there is no warp or weft result — one figure describes the fabric as a whole. That is the point of a burst test and the reason it is not a substitute for a directional tensile test.
Test speed
- Machine type
- Constant rate of traverseCRT — which is what the method name distinguishes.
- Rate
- Constant, from the standard's text
- Recorded
- Peak force
Calculations
F = peak force, in newtons
Reported as a force, not a pressure. That is the difference from the hydraulic diaphragm methods, which report the pressure at burst — the two are not convertible without assumptions about the fabric.
How the test runs
- 01Condition the fabric in the textile standard atmosphere.
- 02Cut squares large enough for the ring to grip all the way round.
- 03Clamp between the grooved ring halves, taut but not stretched.
- 04Check the fabric cannot slip at the rim.
- 05Traverse the clamp onto the fixed ball at the constant rate.
- 06Continue until the fabric ruptures.
- 07Record peak force.
- 08Discard any specimen that slipped in the clamp rather than bursting.
What the report has to contain
- Reference to ASTM D3787
- Fabric identification, construction and finish
- Ring and ball dimensions
- Conditioning atmosphere
- Rate of traverse
- Bursting strength in newtons
- Displacement at rupture where recorded
- Number of specimens, mean and standard deviation
- Any specimen discarded for clamp slippage
What the machine must be capable of
The method calls for a constant-rate-of-traverse tensile testing machine conforming to Specification D76/D76M, with the ball-burst attachment replacing the usual clamp assembly; D76/D76M-21 is the current edition of that specification, and its accuracy tolerances sit in that document rather than in this method.
No force capacity is prescribed. Apparel knits, wovens and nonwovens generally burst between roughly 100 N and 1 kN, and fixture suppliers size ball-burst work for fabrics failing below about 2.2 kN, so a frame of a few kN with a load cell matched to the fabric class covers ordinary acceptance testing. The cell matters more than the frame, since only the peak is used and a small burst read at the bottom of an oversized cell is noisy exactly where it counts.
Traverse speed is fixed at 305 ± 13 mm/min (12 ± 0.5 in./min); textiles are rate-sensitive enough that this is part of the method, not a convenience setting.
The fixture is the test. Ring bore is 44.450 ± 0.025 mm and the ball 25.400 ± 0.005 mm, tolerances kept tight because the exposed area and the radius the fabric is drawn over together set the force. A scratched ball, or a ring whose grooves have flattened, changes the answer while still looking serviceable. No extensometer is used, and the laboratory must hold the conditioning atmosphere.
What goes wrong in practice
Running the wrong class of machine matters most and is hardest to detect afterwards. Most frames in service are constant-rate-of-extension; fit a ball-burst attachment to one and the result belongs to D6797 whatever the report says.
Slippage under the ring shows as a curve that climbs gently instead of peaking sharply, with the fabric drawn inward all round; smooth, coated or heavy knitted fabrics are the usual culprits. The remedy is clamp condition, not more clamp force — crushing the fabric at the ring moves the failure to the clamp line, where it is no longer a fabric result.
The ball is neglected because it looks indestructible, but it is a wear part: a burr picked up from a fabric containing glass or metal yarn cuts rather than stretches, and figures fall by a margin that reads as a material change.
Off-centre mounting is the last. If ball and ring are not concentric the fabric reaches its limit on one side first, and peaks come in low and scattered.
The burst family
| ASTM D3787 CRT | ASTM D6797 CRE | ISO 13938-1 hydraulic | |
|---|---|---|---|
| Moving member | The clamp | The ball | A fluid-driven diaphragm |
| Result | Force, N | Force, N | Pressure, kPa |
| Directionality | None — all directions at once | None | None |
| Comparable with the others | No | No | No |
Three burst methods, three sets of numbers, none convertible. A specification quoting a bursting strength without naming the method has not specified a test — and the CRT and CRE ball methods differ only in which member moves, which is easy to overlook and enough to change the result.
Questions we are asked about this test
What is ASTM D3787?
It is the ASTM constant-rate-of-traverse ball burst test for textiles. A square of fabric is clamped between grooved rings leaving a circle a little over 44 mm exposed, and the clamp is driven onto a fixed 25.4 mm steel ball until the fabric ruptures. The result is the maximum force required.
What is the difference between D3787 and D6797?
Which member moves. In D3787 the ring clamp traverses onto a fixed ball, on a constant-rate-of-traverse machine; in D6797 the ball rides on the crosshead and advances into a held clamp, on a constant-rate-of-extension machine. The distinction sounds trivial and is not — the two give different numbers, so a specification must name which.
Why is there no warp and weft result?
Because the ball stretches the fabric in every in-plane direction at once. A burst test deliberately produces a single figure describing the fabric as a whole, which is useful for knitted and nonwoven materials that have no clear directional structure — and it is exactly why a burst result cannot substitute for a directional tensile test.
Why is the result a force rather than a pressure?
Because a ball pushed through fabric applies a force, and there is no meaningful area to divide it by. The hydraulic diaphragm methods report a pressure because a fluid genuinely applies one. The two families are not convertible, which is another reason the method has to be named.
What causes a wrong burst result?
Slippage at the clamp rim, almost always. If the fabric draws in rather than stretching, more material is being deformed than the method intends and the peak force comes out high. The grooved ring exists to prevent it, and a specimen that visibly drew in should be discarded rather than recorded.
Is the ball burst test suitable for knitted fabrics?
It is one of the better choices for them. A knitted fabric has no fixed warp and weft directions in the way a woven one does, and it extends a great deal before failing, so a strip tensile test is awkward and direction-dependent. Pushing a ball through a clamped circle loads the fabric in every direction at once, which is closer to how a knit actually fails in use.
Why does the clamping ring matter so much?
Because whatever slips through the ring is counted as fabric extension and is not resisting the ball. A fabric that draws in at the clamp produces a low, scattered result, and the slippage is easy to miss because the specimen still bursts convincingly. Ring surfaces have to grip the fabric without cutting it, which for slick or coated goods often means changing the ring facing rather than tightening it further.
Running ASTM D3787 on the Series 7200 and Series 9000
Dak verifies against whichever standard the method names, and where a class applies our frames sit a class tighter than it asks.
| The method asks for | Dak supplies | |
|---|---|---|
| Capacity | No force capacity is prescribed; the machine requirement is conformity with Specification D76/D76M. Knitted, woven and nonwoven apparel fabrics generally burst between roughly 100 N and 1 kN, and fixture suppliers size ball-burst work for fabrics failing below about 2.2 kN, so a machine of a few kN with a well-matched load cell covers ordinary acceptance testing. | Load cells from 1 kg to 60 ton on the Series 7200, and 0.5 to 100 kN on the Series 9000 |
| Force accuracy | ASTM D76/D76M | ISO 7500-1 Class 0.5, verified to ASTM E4, DIN 51221 and BS 1610 |
| Gripping | Ball-burst attachment: grooved ring clamp driven against a fixed polished steel ball | Our compression anvils, built to the specimen |
This page describes the method as practised. The governing text is the current edition from the issuing body. Tell us what you are testing and we will answer with the machine, the fixture and a quotation.