This test evaluates if a finished wire/cable specimen will block (stick to itself) when subjected to the specimen’s rated temperature. While on an aircraft, wires may be exposed to high temperatures and it is important to check if the finished wire specimens are prone to blocking (in other words, the test examines whether the wire will melt and adhere to itself at the rated temperature).
The test’s pass/fail criteria is based on the sample’s post-elevated temperature exposure visual examination. If the specimen shows no adhesion between layers of the wire spooled on itself, then the specimen has passed. If adhesion is observed, the specimen will have failed the test (this may mean that a lower temperature rating is necessary for the specimen).
Parameters that can be changed with this test include:
- Mandrel diameter
- Exposure duration
- Post-test assessment
For the combined Blocking and Lamination testing as outlined in EN3475, please refer to the Delamination and Blocking page