Testing standard
ISO 1827
Rubber, vulcanized or thermoplastic — Determination of shear modulus and adhesion to rigid plates — Quadruple-shear methods
Written and technically reviewed by Dak System Inc. engineeringLast reviewed
ISO 1827 determines the shear modulus of a rubber and the strength of its bond to rigid plates, using a quadruple-shear arrangement — four rubber blocks bonded between plates so the load path is symmetric and the rubber sees pure shear. It gives two answers from one specimen: how stiff the rubber is in shear, and whether the bond survives.
At a glance
- Test type
- Peel & adhesion — a bonded joint is pulled apart
- Published by
- ISO
- Edition
- ISO 1827:2022
- Material
- Rubber, elastomers & foams
- Runs on
- Series 7200 and Series 9000
What the test does
Four rubber blocks are vulcanised between rigid plates in a symmetric arrangement — two inner faces that move together and two outer faces that are held. The assembly is pulled through its central plate at a slow constant rate while the outer plates are restrained, so each block is deformed in shear. Force and relative plate displacement are recorded. Shear stress comes from the force and the bonded area, shear strain from the displacement and the rubber thickness, and the modulus from the initial straight portion of the resulting curve. Loading can then continue to failure to give the bond strength as well.
What it measures, and why it matters
Two things from one specimen: the shear modulus of the compound, and the strength of its bond to the plates. The modulus is what an anti-vibration mount is actually designed on. A mount working in shear is chosen for a target stiffness — high enough to carry the static load, low enough to isolate the frequency that matters — and shear modulus is the material input to that calculation. Hardness is commonly used as a proxy and is a poor one, since two compounds of the same durometer can differ appreciably in shear. The bond result, meanwhile, is a manufacturing check on the same specimen.
Specimen and jig
Shear is the awkward loading to produce cleanly. Four blocks rather than one, and symmetry throughout, is how this method gets there.
- Arrangement
- Four rubber blocks between rigid platesTwo inner faces move, two outer faces are held. The symmetry cancels the bending couple a single or double block would produce.
- Bonded area
- Measured on each block
- Bonding
- Vulcanised to the plates in one operation
- Plate preparation
- As production does itFor the adhesion result, preparation is the dominant variable.
- Alignment
- Central plate must pull truly axially
- Check for barrelling
- Before accepting a modulusDakA block that bulges is no longer in simple shear, and the modulus taken from it is low.
Two results, two purposes. The shear modulus is a material property for design; the bond strength is a manufacturing check. A specimen that fails at the interface has given you the second and forfeited the first.
Test speed
- Rate
- Slow and constant, per the edition in force
- Modulus range
- From the initial straight portion of the curve
- Preconditioning
- Where the specification requires itFilled compounds soften over the first cycles, so a first-cycle modulus is not the one the mount will live on.
- Record which cycle
- AlwaysDak
Calculations
τ = F / (2 × A)
- F
- applied force, N
- A
- bonded area of one block pair, mm²
The factor accounts for the load being shared across the symmetric arrangement. Getting it wrong is the commonest arithmetic error in this test.
γ = d / t
- d
- relative displacement of the plates, mm
- t
- rubber thickness, mm
G = τ / γ over the initial straight portion
Only meaningful while the blocks remain in simple shear. Once they barrel, the geometry has changed and the slope is no longer a modulus.
How the test runs
- 01Bond four rubber blocks between the plates, vulcanising in one operation.
- 02Measure the bonded area of each block.
- 03Condition in the standard laboratory atmosphere.
- 04Assemble the jig and check the central plate pulls axially.
- 05Apply any preconditioning cycles the specification requires.
- 06Load at the specified rate, recording force and displacement.
- 07Watch for barrelling and stop taking modulus once it appears.
- 08Take the modulus from the initial straight portion.
- 09Continue to failure where bond strength is required.
- 10Examine the failed faces and estimate rubber retention.
- 11Report the cycle the modulus came from.
What the report has to contain
- Reference to ISO 1827 and the edition
- Rubber compound and plate material
- Plate preparation and primer
- Vulcanisation schedule
- Bonded area and rubber thickness
- Conditioning and test temperature
- Rate and any preconditioning cycles
- Shear modulus, and the cycle it was read from
- Bond strength where determined
- Percentage rubber retention
- Number of specimens and the median
What the machine must be capable of
Modest force — commonly a few hundred newtons to a few kilonewtons — with a slow, steady, genuinely axial pull. The axiality is the demanding part: the jig relies on symmetry to keep the rubber in pure shear, and a central plate drawn off-axis reintroduces exactly the couple the four-block arrangement exists to cancel. Displacement must be measured between the plates rather than taken from crosshead travel, since the jig and the load string are both elastic and their compliance would otherwise be read as rubber strain, understating the modulus.
What goes wrong in practice
Accepting a modulus from a barrelled specimen is the characteristic error. Once a block bulges, part of the deformation is compression and extension rather than shear, the slope no longer describes a shear modulus, and the figure reads low. Nothing corrects it afterwards. The arithmetic is the second trap: the applied force is shared across the symmetric arrangement, and getting that factor wrong produces a plausible number that is out by a factor of two. Beyond those, reporting a first-cycle modulus on a filled compound overstates the stiffness the mount will actually have, and taking displacement from the crosshead rather than the plates buries the rubber's strain inside the jig's compliance.
ISO 1827 or ISO 813
| ISO 1827 | ISO 813 | |
|---|---|---|
| Loading | Pure shear | 90° peel |
| Gives | Shear modulus and bond strength | Bond strength only |
| Represents | A mount working in shear | A bonded lining or facing |
| Specimen | Four blocks, symmetric | One strip on one plate |
They answer different questions. ISO 813 asks only whether the bond holds; ISO 1827 also gives the stiffness a designer needs. Where a mount works in shear, the second is the relevant geometry.
Questions we are asked about this test
What is ISO 1827?
It is the ISO method for determining the shear modulus of a rubber and the strength of its bond to rigid plates, using a quadruple-shear arrangement. Four rubber blocks are bonded between plates so that the load path is symmetric, and the assembly is pulled through its central plate while the outer plates are held.
Why four blocks rather than one?
Symmetry. A single bonded block loaded in shear produces a bending couple, because the applied force and the reaction are not in the same plane — so the rubber sees shear plus bending and the modulus that comes out is not a shear modulus. Four blocks arranged symmetrically cancel that couple, which is the whole reason for the geometry.
What does shear modulus actually get used for?
Sizing anti-vibration mounts. A mount working in shear is chosen for a target stiffness — enough to carry the load, low enough to isolate the frequency of concern — and shear modulus is the material input to that calculation. Hardness is often used as a proxy and is a poor one, because two compounds of the same durometer can differ appreciably in shear.
Why does barrelling invalidate the modulus?
Because it means the blocks are no longer in simple shear. Once a block bulges, part of the deformation is compression and extension rather than shear, and the slope of the curve is describing a mixed state. The modulus taken from it reads low, and no correction recovers the true value — the specimen has to be within its valid range.
Can I get both results from one specimen?
Usually, and that is the method's economy — load to get the modulus, then continue to failure for the bond. But a specimen that fails at the interface early gives you the bond result and forfeits the modulus, so where both are required it is worth running enough specimens that an early bond failure does not lose the material property as well.
Why does the cycle number matter?
Because filled rubber softens over its first few deformations — the Mullins effect — and then stabilises. A first-cycle modulus is higher than anything the compound will produce again, so it overstates the stiffness of a mount in service. Which cycle the figure came from belongs beside it.
How does this relate to dynamic testing?
ISO 1827 is a static or quasi-static measurement: it gives the stiffness under a slow, one-directional load. A mount in service sees oscillation, where the modulus is frequency- and amplitude-dependent and energy is lost each cycle. Dynamic methods such as ASTM D945 address that, and the static modulus is the starting point rather than the whole answer.
Running ISO 1827 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 | Low to moderate — commonly 100 N to 3 kN depending on the bonded area and compound | 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 E4 | Verified to ASTM E4, and to ISO 7500-1 Class 0.5 |
| Gripping | A quadruple-shear jig: four rubber blocks bonded between rigid plates, two moving and two fixed, so the load path is symmetric | Our shear fixtures, 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.