7.1 Troubleshooting: Failure Modes

There are four different types of assembly failure modes: adhesive, cohesive, substrate and adhesive/cohesive. When analysing a failed assembly, it is essential to determine which failure mode has occurred. A thorough understanding of these failure modes will help identify the root cause of the failure, as well as contributing factors.

Figure 207 Examples of the different failure modes

7.1.1 Adhesive Failure

Adhesive failure occurs when the bonded assembly is subjected to a load that exceeds the adhesion, causing failure at the interface between the adhesive and the substrates. In this failure mode, there is visible adhesive residue remaining on one of the substrates, or it may be more localised, with each side having a piece of the adhesive layer. This localised adhesive failure often appears with adhesive segments on the two substrates mirroring each other as in Figure 209.

Figure 208 Adhesive failure

If this is the adhesive failure mode, a stronger bond can be achieved by reconsidering either the surface preparation or the adhesive selection.

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