How can the strength of an adhesive joint be tested in a repeatable way? One of the most widely used comparison methods is the tensile loading of a single-lap bonded specimen, commonly described as a lap-shear test.
The method is covered by standards including ISO 4587:2003 and EN 1465:2009. Both describe testing of rigid-to-rigid bonded assemblies, but they should not be treated as one standard replacing the other.
The result is useful for comparing adhesive systems, surface preparation, cure conditions and ageing effects. It is not, however, a direct design value for a real production joint.
Key takeaways
- ISO 4587:2003 is still current. It was not replaced by EN 1465.
- The older PN-EN 1465:2003 was replaced by PN-EN 1465:2009.
- Both methods concern tensile lap-shear testing of rigid bonded assemblies.
- A commonly used metal specimen geometry is approximately 100 × 25 × 1.6 mm with a 12.5 mm overlap.
- The result depends on substrate, surface preparation, overlap geometry, bond-line thickness, cure and test conditions.
- After testing, evaluate not only maximum force or calculated stress, but also the failure mode.
- ISO 4587 is a test method. ISO explicitly states that it does not provide design information.
What does ISO 4587 define?
ISO 4587:2003 specifies a method for determining the tensile lap-shear strength of rigid-to-rigid bonded assemblies using a standard specimen under specified conditions of preparation and testing.
An important correction to the old English article is that ISO 4587 has not been withdrawn. The earlier ISO 4587:1995 edition was withdrawn and replaced by the current ISO 4587:2003 edition.
ISO also states that this test procedure does not provide design information. The value obtained from a standard lap specimen should therefore be treated as a controlled comparison result, not as an allowable design stress for every real joint.
ISO 4587 and EN 1465 – what is the difference?
Older materials sometimes state that ISO 4587 was replaced by PN-EN 1465. That is not correct.
ISO 4587:2003 and EN 1465:2009 are separate standards describing very similar tensile lap-shear test concepts for rigid bonded assemblies.
| Standard | Status | Practical meaning |
|---|---|---|
| ISO 4587:2003 | Current | International method for tensile lap-shear strength of rigid-to-rigid bonded assemblies. |
| PN-EN 1465:2003 | Withdrawn | Older Polish adoption of EN 1465. |
| PN-EN 1465:2009 | Current Polish edition replacing the 2003 edition | Method for tensile shear strength of lap joints. |
If a customer, quality plan or laboratory procedure requires a specific standard, the report should identify the exact document and edition used.
How is a lap-shear specimen prepared?
The method uses two rigid adherends bonded together with a defined overlap.
A typical geometry used for metal specimens includes:
- length of each adherend: approximately 100 mm,
- width: approximately 25 mm,
- thickness: approximately 1.6 mm,
- overlap length: approximately 12.5 mm.
The exact dimensions and tolerances should always be checked in the standard and laboratory procedure used for the test.
Surface preparation must be repeatable
Before bonding, define the complete surface-preparation procedure. Depending on the system, this may include cleaning, degreasing, abrasion, chemical treatment or primer.
If two adhesives are compared using different surface-preparation procedures, the test is no longer comparing only the adhesives. It is comparing two complete bonding systems.
Control the overlap and bond-line thickness
Alignment, overlap length and adhesive-layer thickness should be controlled as consistently as possible. Fixtures or dedicated bonding jigs are commonly used for this purpose.
Do not assume that a thinner bond line always produces a stronger joint. Bond-line thickness changes the stress distribution and interacts with adhesive chemistry, substrate stiffness and joint geometry.
How is the lap-shear test performed?
After bonding and full cure, the specimen is mounted in the grips of a tensile-testing machine. The tensile load is applied along the main axis of the specimen and increased until the joint or one of the adherends fails.
The machine records the maximum force reached during the test.
How is the result calculated?
The nominal lap-shear strength can be expressed as:
τ = Fmax / A
where:
- τ – nominal lap-shear strength,
- Fmax – maximum recorded force,
- A – nominal bonded overlap area.
If force is expressed in newtons and area in mm², the result is obtained in N/mm², which is equivalent to MPa.
What does the failure mode tell you?
Maximum force alone does not describe the complete behaviour of the joint. After the test, both fracture surfaces should be examined and the failure pattern should be documented.
ISO 10365:2022 defines designations for the main failure patterns used in mechanical testing of bonded assemblies.
| Failure mode | What is observed? | What may need investigation? |
|---|---|---|
| Adhesive failure | The adhesive separates mainly from one substrate. | Surface preparation, contamination, compatibility, coating quality or adhesion at the interface. |
| Cohesive failure | The adhesive fractures within its own layer and remains on both substrates. | Adhesive strength, cure, bond-line thickness and applied load. |
| Substrate failure | The adherend itself fails before the bonded interface. | Whether the substrate has become the limiting element and whether that failure mode is acceptable. |
| Mixed failure | More than one failure mechanism appears on the specimen. | Process repeatability, local surface variation and stress concentration. |
Cohesive failure is often a positive sign because the adhesive–substrate interface was not the weakest part of the specimen. It does not, however, automatically mean that the entire system meets the application requirements.
What affects the test result?
Two laboratories can obtain different results for the same adhesive if the specimens or test conditions are different.
| Parameter | Why it matters |
|---|---|
| Adherend material | Affects stiffness, surface chemistry and possible failure mode. |
| Surface preparation | Directly affects adhesion and process repeatability. |
| Overlap geometry | Changes bonded area and stress distribution. |
| Bond-line thickness | Changes the stress state and mechanical behaviour of the joint. |
| Cure conditions | Time, temperature and pressure can affect the degree of cure. |
| Conditioning and ageing | Temperature, moisture, water and chemicals can change joint properties. |
| Test temperature | Polymeric adhesives can change mechanical behaviour significantly with temperature. |
| Test speed | Influences material response and should follow the selected procedure. |
This is why a value from an adhesive technical data sheet should not be compared directly with an in-house laboratory result without checking how both specimens were prepared and tested.
What should a test report include?
The report should contain enough information to reconstruct the important test conditions and determine whether results from different specimen series can be compared.
Depending on the standard, laboratory procedure and purpose of the test, the report should include information such as:
- exact standard and edition used,
- adhesive identification and, where relevant, product batch,
- adherend material, dimensions and specimen quantity,
- surface-preparation procedure,
- overlap geometry,
- bond-line-thickness control method,
- cure conditions and cure time,
- conditioning or ageing procedure,
- test conditions and test speed,
- maximum force and/or calculated strength,
- individual specimen results and appropriate statistical summary,
- failure-mode description,
- any deviations from the standard procedure.
DIN 2304, DIN 6701 and ISO 21368 – what has changed?
The old English article referred to DIN 2304 and DIN 6701 as current quality frameworks. That information now needs updating.
DIN 2304-1
DIN 2304-1:2020 has been withdrawn. In the German standards system it has been replaced by DIN EN ISO 21368:2024-10, based on ISO 21368.
DIN 6701 and railway bonding
The former DIN 6701 series for adhesive bonding of rail vehicles has been replaced by EN 17460:2022 for current railway applications.
A lap-shear test according to ISO 4587 or EN 1465 may form part of material qualification, process validation, quality control or failure analysis, but the required test programme should come from the actual quality system and application risk.
For a broader quality-management perspective, see How to implement adhesive bonding in production – DIN 2304 and ISO 21368.
Why test adhesive joints?
Compare adhesives and surface-preparation methods
Testing allows different adhesives and preparation procedures to be compared on the actual production substrate.
Validate process parameters
Cure temperature, cure time, bond-line thickness, primer and application parameters can be evaluated systematically.
Assess durability after ageing
Testing before and after exposure to temperature, humidity, water or process chemicals can reveal whether the joint remains stable over time.
Monitor process repeatability
Regularly prepared control specimens can help identify process drift before it becomes a production failure.
Analyse failures
Maximum force combined with failure-mode analysis helps determine whether the weak point was the adhesive layer, the interface, the substrate or another part of the system.
For a broader overview of qualification methods, see How to test an adhesive bond – test methods and failure-mode analysis.
FAQ – ISO 4587 and EN 1465 adhesive-joint testing
Has ISO 4587 been withdrawn?
No. ISO 4587:2003 remains current. The withdrawn edition was ISO 4587:1995.
Is PN-EN 1465:2003 still current?
No. It was replaced by PN-EN 1465:2009.
What does ISO 4587 test?
It specifies a method for determining tensile lap-shear strength of rigid-to-rigid bonded assemblies using a standard specimen.
What dimensions are used for a typical specimen?
A commonly used metal specimen geometry is approximately 100 × 25 × 1.6 mm with an overlap of about 12.5 mm. Always check the detailed requirements and tolerances in the standard edition used by the laboratory.
What does the result in MPa mean?
It is a nominal stress calculated from the maximum force divided by the nominal bonded overlap area. It should not be treated as a direct allowable design stress for a real structure.
Is cohesive failure always the best result?
Not automatically. It often shows that the adhesive–substrate interface was not the weakest part of the specimen, but the achieved strength, scatter and application requirements still have to be evaluated.
Can ISO 4587 be used to design a real bonded joint?
No. ISO explicitly states that the procedure does not provide design information. Real joint design must account for actual geometry, loading, environment, durability and safety factors.
Does a laboratory have to be accredited to perform ISO 4587?
Not every comparative test must be performed by an accredited laboratory. If the customer, project or quality system requires an accredited report, confirm that the specific method is included in the laboratory’s accreditation scope.
Summary
ISO 4587 and EN 1465 lap-shear tests are valuable tools for comparing and controlling industrial bonding processes.
Their value comes from repeatable specimen geometry and controlled test conditions. To interpret the result properly, however, you must consider the complete bonding system: substrate, surface preparation, bond-line thickness, cure, ageing and test conditions.
The most useful assessment combines the mechanical result, scatter between specimens and the observed failure mode.
Need to verify an adhesive joint?
If you are selecting an adhesive, changing surface preparation, analysing a failure or comparing several process variants, define the test method before preparing the specimens.
Log in with Facebook
Log in with Google