Standard 25 mm
Pneumatic Vice Action Grip
Pneumatic vice action grips clamp the full specimen width at a constant, even pressure — which is what stops one side slipping or tearing before the other.
SpecificationsTesting standard
ASTM D4595/D4595M
Standard Test Method for Tensile Properties of Geotextiles by the Wide-Width Method
Written and technically reviewed by Dak System Inc. engineeringLast reviewed
ASTM D4595/D4595M measures the tensile properties of geotextiles on a 200 mm wide specimen. Unlike the grab and strip index tests, it is written to supply design parameters for reinforcement applications — reinforced roadways, embankments over soft subgrade, retaining walls and slopes.
At a glance
- Test type
- Tensile — the specimen is pulled apart
- Published by
- ASTM
- Edition
- D4595/D4595M-24
- Runs on
- Series 7200 and Series 9000
What the test does
A geotextile specimen, recommended at 200 mm wide by at least 200 mm long, is conditioned, clamped across its full width and extended at a constant rate until it fails. Force is recorded against elongation, with strain taken from the specimen wherever a modulus is to be reported. The outputs are force per unit width at maximum load, elongation at that load, and secant modulus at whatever elongation the specification names. Machine and cross-machine directions are tested and reported separately, in one unit system only.
What it measures, and why it matters
The force-elongation behaviour that reinforcement design consumes directly. The method exists because designers of reinforced roadways and pavements, embankments over soft subgrade, retaining walls and reinforced slopes need a force per metre of width and a stiffness at working strain — quantities the quick grab index cannot supply. That is the practical division between this method and D4632: one is a quality check on a delivery, the other produces numbers that go into a calculation. A grab result cannot be converted into a wide-width one, and a specification asking for design values will not accept it.
Specimen and units
Two hundred millimetres wide, and at least as long. The width is what stops the specimen contracting and reading low.
- Width
- 200 mm (8 in) recommendedThe recommended size in the method. Narrower specimens waist and understate the fabric.
- Length
- At least 200 mm (8 in)
- Applies to
- Woven, nonwoven, layered and knit fabrics, and felts
- Units
- SI and inch-pound are separate standardsThe M in the designation is not decoration — the two systems are used independently, never combined in one report.
- Directions
- Machine and cross-machine, separately
- Check the specimen is square in the grips
- Before every testDakA specimen clamped a degree off square loads one edge first and fails there, below the fabric's real capacity.
This method is written for design, not only for acceptance. That is what separates it from the grab test, and it is why the specimen is large and the strain measurement is taken seriously.
Test speed
- Rate
- Constant rate of extension, from the gauge length
- Reported
- Force per unit width, elongation, and modulus
- Strain
- From the specimen where modulus is required
- Report SI or inch-pound, not both
- DakMixing them within a report is the mistake the dual designation exists to warn against.
Calculations
Wide-width tensile strengthTult
Tult = Fmax / B
- Fmax
- maximum force
- B
- nominal specimen width
Force per unit width, because geotextile thickness is compressible and gives no usable area.
Elongation at maximum forceε
ε = (ΔL / L₀) × 100
- ΔL
- extension at maximum force
- L₀
- gauge length
Crosshead-derived strain includes grip take-up, which is a large share of a short gauge length.
Secant modulusJ
J = T / ε at a specified elongation
- T
- force per unit width at that elongation
- ε
- the specified elongation as a fraction
Always reported with the elongation it was taken at, since the curve is not linear.
How the test runs
- 01Cut specimens 200 mm wide and at least 200 mm long, in both principal directions.
- 02Condition the specimens as required.
- 03Fit wide-width grips, using roller or capstan clamping for high-strength fabrics.
- 04Clamp across the full width at an even pressure.
- 05Check the specimen is square to the direction of pull.
- 06Fit an extensometer where modulus is to be reported.
- 07Set the constant rate of extension from the gauge length.
- 08Load to failure, recording force and elongation.
- 09Calculate force per unit width and elongation at maximum force.
- 10Calculate secant modulus at the elongation the specification requires.
- 11Reject jaw breaks, and report the two directions separately in one unit system only.
The fixture this method needs
What the report has to contain
- Reference to ASTM D4595/D4595M and the edition
- Geotextile identification, construction and mass per unit area
- Direction tested and specimen dimensions
- Conditioning applied
- Grip type and clamping arrangement
- Rate of extension
- Force per unit width for each specimen
- Elongation at maximum force, and how strain was measured
- Secant modulus with the elongation it was evaluated at
- Which unit system was used, and the number of specimens rejected
What the machine must be capable of
Capacity set by the strongest product in the range, since reinforcement geotextiles are commonly specified above fifty kilonewtons per metre. Grips must hold the full 200 mm width at an even pressure, and for high-strength fabrics roller or capstan clamping is effectively required — a flat jaw clamped hard enough to hold the load crushes the yarns at the jaw line and moves the failure there. Where modulus is reported, an extensometer on the specimen is needed, because grip take-up is a large share of movement on a short gauge length.
What goes wrong in practice
Substituting a grab result where design values were asked for, which is not a shortcut but a different measurement. Mixing SI and inch-pound values within one report, which the dual designation exists specifically to warn against, since the two systems are used independently rather than converted. Quoting a secant modulus without the elongation it was evaluated at. Accepting jaw breaks. And skewed specimens, which fail early from one edge and produce scatter that looks like material variability. A subtler one is reporting a mean without saying how many specimens were rejected on the way to it: wide-width testing on strong fabrics can lose a substantial fraction of specimens to jaw breaks, and a mean drawn from the survivors of a difficult clamping arrangement is a different statistic from one drawn from a clean set. The rejection count belongs in the report for the same reason the grip type does.
ASTM D4595 or ASTM D4632
| ASTM D4595/D4595M | ASTM D4632 | |
|---|---|---|
| Specimen | 200 mm wide | Narrow, grabbed centrally |
| Purpose | Design parameters for reinforcement | Quality index and acceptance |
| Reported | Force per unit width | Grab breaking force |
| Substitutable | No | No |
These answer different questions and neither replaces the other. A grab result cannot be converted into a wide-width one, because the narrow specimen contracts and the wide one is prevented from doing so.
Questions we are asked about this test
What is ASTM D4595?
It is the ASTM wide-width tensile test for geotextiles, applicable to woven, nonwoven, layered and knit fabrics and to felts. A 200 mm wide specimen is pulled at a constant rate of extension and the force-elongation behaviour recorded, giving force per unit width, elongation at maximum force and secant modulus. The current designation is D4595/D4595M-24, and the title dropped the word Strip in a recent revision.
How is it different from the grab test?
In purpose, not just in specimen size. D4632 grab strength is a quality index for acceptance — quick, cheap, and adequate for confirming a delivery matches what was ordered. D4595 is written to supply design parameters for reinforcement applications: reinforced roadways and pavements, embankments over soft subgrade, retaining walls and slope reinforcement. A grab result cannot be converted into a wide-width one, and specifications that call for design values will not accept it.
Why 200 mm wide?
Because a narrow specimen contracts as it stretches. The edge yarns pull inwards, the specimen waists, and the recorded strength is well below what the fabric delivers in the ground, where it is continuous in every direction and cannot narrow. Two hundred millimetres of width, with a length that does not exceed it by much, suppresses that contraction so the measurement reflects the material rather than the specimen shape.
What does the M in D4595/D4595M mean?
That the standard exists in two unit systems — SI and inch-pound — which are to be regarded separately and used independently. It is not a conversion. The two sets of values are not exact equivalents of each other, so a report must state which system was used and must not mix them. The dual designation is there specifically to prevent that mixing.
Why does modulus need the elongation quoted with it?
Because a geotextile's force-elongation curve is not a straight line, so the secant modulus depends on where along the curve it is taken. A modulus at 2 % elongation and one at 10 % are different numbers describing the same fabric. Specifications name the elongation, and a modulus reported without it cannot be checked against anything.
Why is a jaw break rejected?
Because it reports the clamping rather than the fabric, and it always reads low. Wide-width specimens of high-strength reinforcement products are especially prone to it: a flat jaw clamped hard enough to hold fifty kilonewtons per metre crushes the yarns exactly where it grips. Roller or capstan clamping spreads the holding force along a curve instead of concentrating it at a line, which is why it is used on strong fabrics.
Does it matter if the specimen sits slightly askew in the grips?
Yes, more than it looks. A specimen clamped a degree off square loads one edge before the other, so that edge reaches its limit first and failure propagates from it at a force below the fabric's real capacity. On a 200 mm width a small angular error puts a substantial length difference between the two edges, which is why squaring the specimen is a check rather than an assumption.
Running ASTM D4595/D4595M 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 | Moderate to high — reinforcement geotextiles are commonly specified above 50 kN/m | 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 requirements for textile testing machines | ISO 7500-1 Class 0.5, verified to ASTM E4, DIN 51221 and BS 1610 |
| Strain measurement | An extensometer of the class the method specifies | Certified to ISO 9513 Class 1 and ASTM E83 — non-contact video, clip-on and high-elongation |
| Gripping | Wide-width grips holding the full 200 mm specimen width; roller or capstan clamping for high-strength products | Our eccentric roller grips or split capstan grips, built to the specimen |
| Environment | 23 ± 2 °C standard laboratory atmosphere | 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.