1 ноября, 2015 
Pokraskin Inaccurate temperature control during the autoclaving process may indeed be the cause for adhesive failure. This is demonstrated by the delamination of a tail rotor blade (Figure 7.69).
During inspection, a delaminated area was found in the bonding between honeycomb and outer cover sheet which was opened during a failure analysis in the laboratory. The distinct brown discoloration of the thermosetting adhesive, with large bubbles and separation from the honeycomb core cells, is shown in Figure 7.70.
In this case the adhesive must have been overheated for very short period oftime while in the low-molecular-weight state — that is, during manufacture. An elevated temperature exposure after cure would have induced polymer decomposition instead of the observed large-pore formation in the cured thermosetting duroplastic resin. Furthermore, examination of the coatings on the external surface of the rotor blade did not reveal any signs of an external thermal damage due to operation.
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Figure 7.71 Delamination of a bonded glass-fiber patch. |
7.8.6
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