Testing standard
ISO 13938-1
Textiles — Bursting properties of fabrics — Part 1: Hydraulic method for determination of bursting strength and bursting distension
Written and technically reviewed by Dak System Inc. engineeringLast reviewed
ISO 13938-1 measures the bursting strength of fabrics hydraulically. A clamped circle of fabric is driven into a dome by fluid pumped beneath a rubber diaphragm until it ruptures. Both bursting pressure and bursting distension are reported — a pressure rather than a force, which is what separates this family from the ball-burst methods.
At a glance
- Test type
- Puncture & burst
- Published by
- ISO
- Edition
- ISO 13938-1:2019
- Runs on
- Series 7200 and Series 9000
What the test does
A piece of fabric is laid over an expansive rubber diaphragm and clamped round its edge by a rigid ring, leaving a known circle of it unsupported. Fluid is pumped beneath the diaphragm at a controlled rate, so the membrane swells and drives that circle into a growing dome, which rises until the fabric ruptures, abruptly, behind a safety cover. Pressure and dome height are followed throughout, both captured at the instant of burst.
What it measures, and why it matters
Two quantities are reported: bursting strength, the pressure at which the fabric gives way, and bursting distension, how far it rose before it did. Some testers report the volume pumped in instead of height.
Bursting strength is the figure of merit for fabrics not loaded along one axis in service. Knitted, nonwoven and coated fabrics are pushed out of plane by whatever sits behind them, and a multiaxial pressure test represents that better than a strip pulled in one direction. Distension is the more diagnostic result and the more often ignored: two fabrics can burst at the same pressure with one having stretched twice as far getting there, and the stretchier one bags at the knee or blows through a grid the stiffer one bridges.
Specimen and test area
- Clamping
- A rigid ring round the edgeLeaving a known circle unsupported. The clamped area is a defined test area, and results from different areas are not comparable.
- Diaphragm
- Expansive rubber, beneath the fabricThe fluid does not touch the fabric — it inflates the membrane, which drives the dome.
- Diaphragm correction
- Measured and subtractedThe membrane itself takes pressure to inflate, and that is not the fabric's contribution.
- Safety cover
- RequiredThe rupture is abrupt and energetic.
- Recorded
- Bursting pressure and dome height at burst
State the test area. A smaller clamped circle bursts at a higher pressure for the same fabric, so a pressure quoted without its area is not comparable with anything — the commonest error in specifying a hydraulic burst requirement.
Test conditions
- Pumping
- At a controlled rateSo the time to burst falls within a defined window.
- Test area
- Selected from the standard's options
- Conditioning
- Textile standard atmosphere
Calculations
P = pressure at burst − diaphragm correction
- diaphragm correction
- the pressure needed to inflate the membrane alone to the same height, kPa
The subtraction is not optional. On a light fabric the membrane can account for a substantial share of the raw pressure reading.
h = dome height at the instant of burst
The extensibility half of the answer. Two fabrics can burst at the same pressure and reach quite different dome heights, which matters for anything that must conform to a shape.
How the test runs
- 01Condition the fabric in the textile standard atmosphere.
- 02Select the test area and record it.
- 03Measure the diaphragm correction across the range for that area.
- 04Lay the specimen over the diaphragm and clamp round the edge.
- 05Close the safety cover.
- 06Pump fluid at the controlled rate so the dome rises steadily.
- 07Continue until the fabric ruptures.
- 08Record burst pressure and dome height at that instant.
- 09Subtract the diaphragm correction.
- 10Report the test area alongside every result.
What the report has to contain
- Reference to ISO 13938-1
- Fabric identification, construction and finish
- TEST AREA used
- Diaphragm correction applied
- Conditioning atmosphere
- Rate of pressurisation or time to burst
- Bursting strength in kPa, corrected
- Bursting distension
- Number of specimens, mean and coefficient of variation
What the machine must be capable of
The instrument is not a load frame and measures no force: it is a hydraulic bursting tester whose capacity is quoted as pressure against a test area, so sizing starts from the fabric class. General apparel bursts well below 800 kPa, roughly the range over which hydraulic and pneumatic testers agree; the hydraulic method is chosen where speciality technical textiles need more pressure than that.
The clamping ring is the real specification. The preferred test area is 50 cm², and smaller and larger areas are also provided for; bore diameters are held to a tight tolerance, since a worn bore changes the loaded area and the answer with it. Which area was used must be reported, since the same fabric bursts at a higher pressure over a small circle than over a large one. Beneath the ring sits a rubber diaphragm up to 2 mm thick.
The method pins its own rate: volume must increase steadily at between 100 cm³/min and 500 cm³/min, within ±10 % of the indicated value, or, where volume rate cannot be set, at a rate found by trial to burst the fabric in 20 ± 5 s.
Accuracy is specified per output: pressure to ±2 % of full-scale range above the first fifth of the range, height at burst up to 70 mm to ±1 mm, volume to ±2 %. Metrological confirmation follows ISO 10012; no ISO 7500-1 force class applies, since nothing measures force, and no extensometer is used. The conditioned atmosphere and a guard over the test head are both requirements.
What goes wrong in practice
The commonest invalid result is a burst that runs into the clamp. Ruptures at the clamping line report the ring's condition rather than the fabric's, and they cluster when clamp pressure is too high, when the bore has been nicked, or when a heavy coated fabric is crushed at the edge before it ever domes.
Slippage is the opposite defect and harder to spot. Slick or heavily finished fabrics creep inward under the ring as the dome grows, so distension reads high and pressure low; drag marks outside the clamp line are the giveaway.
Diaphragms get treated as permanent. A membrane cycled for months stiffens and takes a set, and the tester drifts quietly long before the rubber splits.
Hydraulic against ball burst
| ISO 13938-1 hydraulic | ASTM D3787 / D6797 ball | |
|---|---|---|
| Load applied by | Fluid through a diaphragm | A 25.4 mm steel ball |
| Result | Pressure, kPa | Force, N |
| Also reports | Distension at burst | Nothing else |
| Deformation | A smooth dome | Conforming to a sphere |
| Convertible | No | No |
A pressure and a force are different quantities, and no conversion between the two families exists that does not smuggle in assumptions about the fabric. A specification naming a bursting strength must name the method, and for the hydraulic method the test area as well.
Questions we are asked about this test
What is ISO 13938-1?
It is the international standard for bursting strength of fabrics using a hydraulic method. Fluid inflates a rubber diaphragm beneath a clamped circle of fabric, driving it into a growing dome until it ruptures, and both bursting pressure and bursting distension are reported.
Why does the test area have to be reported?
Because a smaller clamped circle bursts at a higher pressure for the same fabric — less material is being deformed to reach the same dome geometry. A pressure quoted without its test area therefore cannot be compared with another laboratory's result, and specifying a burst requirement without an area is the commonest error in this method.
What is the diaphragm correction?
The pressure needed to inflate the rubber membrane on its own to the same height, measured separately and subtracted from the raw reading. It is not an optional refinement: on a light fabric the membrane can account for a substantial share of the total pressure, so omitting it overstates the fabric considerably.
What is bursting distension and why is it useful?
The height the dome reached at the instant of burst — the extensibility half of the result. Two fabrics can burst at the same pressure while reaching very different dome heights, and that difference matters for anything that has to conform to a shape rather than merely resist a pressure.
How does this compare with a ball burst test?
It reports a pressure where the ball methods report a force, and the two are not convertible — no conversion exists that does not smuggle in assumptions about the fabric. The hydraulic method also deforms the fabric into a smooth dome rather than making it conform to a sphere, which is closer to how a pressurised membrane actually behaves.
Why hydraulic rather than pneumatic bursting?
Because a liquid is effectively incompressible, so the pressure applied to the diaphragm is transmitted immediately and predictably, and the energy stored in the system at burst is small. A pneumatic system stores a great deal of energy in the compressed gas, which releases violently at burst and makes the moment of failure harder to capture accurately.
What does a diaphragm correction actually remove?
The pressure needed to inflate the rubber diaphragm on its own, with no fabric clamped over it. That pressure is a property of the apparatus rather than the fabric, so it is measured in a blank run and subtracted. On strong fabrics it is a small proportion of the total and easily ignored; on light or open fabrics it is a significant share, and omitting it inflates the reported bursting strength.
Running ISO 13938-1 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 | The instrument reads pressure, not force, so no newton figure applies. General apparel fabrics burst well below 800 kPa, which is the range over which hydraulic and pneumatic testers agree; the hydraulic apparatus is chosen precisely because speciality technical textiles need more pressure than that, and capacity is quoted in kPa or MPa against the chosen test area. | Load cells from 1 kg to 60 ton on the Series 7200, and 0.5 to 100 kN on the Series 9000 |
| Force accuracy | ISO 10012 | ISO 7500-1 Class 0.5, verified to ASTM E4, DIN 51221 and BS 1610 |
| Gripping | Circular clamping ring over an expansive rubber diaphragm, under a safety cover | Our a fixture built for this method, built to the specimen |
| Environment | ISO 139 standard atmosphere, 20 ± 2 °C and 65 ± 4 % RH; wet tests use a 1 h soak in grade 3 water at 20 ± 2 °C | 3009 series chambers, −150 °C to +400 °C — temperature only |
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.