Overview
EN 15336:2007 (CEN) specifies a laboratory procedure to determine the time to rupture of bonded lap-shear joints subjected to a static load. The method measures how long a bonded specimen endures a specified stress before failure and is intended for comparative evaluation of adhesives rather than for structural design. Key outcomes include time-to-failure, failure pattern classification and stress-vs-time relationships useful for product assessment and quality control.
Key Topics
- Principle: Measure time to rupture of a lap-shear specimen under a defined static load.
- Apparatus: A vertical test rig that secures specimens at one end and applies weights at the other. The rig must avoid cross-specimen vibration and maintain controlled environmental conditions. A timer with ±1 % accuracy is required.
- Specimens:
- Adherends: metal, rigid plastic or rigid fibre-reinforced plastic.
- Shape: lap-shear geometry per the standard (see Figure 1 in the standard document).
- Bond-line control: use glass spheres (≤ 0.5 % mass of adhesive) or wire spacers (excluded from final test area).
- Surface preparation: follow adhesive or adherend manufacturer instructions or EN 13887.
- Conditioning: use one of the standard atmospheres in EN ISO 291.
- Quantity: at least three specimens per stress level.
- Procedure: Attach specimens, allow equilibrium in the chosen atmosphere, apply defined loads (often a percentage of tensile lap-shear strength from EN 1465), and record time to failure and failure mode (EN ISO 10365).
- Results: Plot stress (ordinate) against average time to failure (abscissa) on a logarithmic time scale.
Applications
This method provides practical value in contexts such as:
- Comparative adhesive testing: rank adhesives by time-to-rupture under given stresses.
- Quality control: verify consistent adhesive performance between batches or processes.
- R&D: evaluate formulation changes, surface treatments, or curing regimes on long-term static performance.
Note: EN 15336:2007 results are specifically for comparison and test method development - they are not suitable for direct structural design or service-life prediction without additional data.
Related Standards
The standard references and complements these documents:
- EN 1465 - tensile lap-shear strength determination
- EN 13887 - surface preparation guidelines for metals and plastics
- EN ISO 291 - standard atmospheres for conditioning and testing
- EN ISO 10365 - designation of main failure patterns
Practical considerations
- Ensure accurate bond-line thickness and consistent surface treatment for comparable data.
- Maintain controlled environment during conditioning and testing to reduce variability.
- Record all identification details, specimen preparation, atmosphere, bond-line thickness, number of specimens, failure patterns and the stress vs time-to-failure graph in the test report as required by the standard.
This structured approach helps laboratories produce repeatable comparative data for adhesive selection, process control and formulation optimization while complying with CEN requirements.