The two principle materials used in aircraft manufacturing, metals and polymers, tote particularly reactive surfaces. This leaves them highly susceptible to contamination. As adhesive bonded repairs become more and more popular in the industry, knowing and understanding surface preparation and surface habits becomes crucial.
BTG Labs' Chief Scientist Dr. Giles Dillingham produced the paper, "Qualification of Surface Preparation Processes for Bonded Aircraft Repair," to present at an annual SAMPE Conference. This paper discusses the use of adhesive bonding in the field of aircraft manufacturing and the importance of surface monitoring.
As metals and polymers experience exposure to contamination on the manufacturing floor and in the field, it is necessary to know and understand the relationship between contaminants and the surface. The difference between a well cleaned and a poorly cleaned surface may only be a few molecular layers, and may be the determining factor of a successful bond or a weak bond.
Qualification of Surface Preparation Processes
The aircraft manufacturing industry uses various surface preparation processes, including grit-blasting and hand sanding. While grit-blasting via a robot shows high reproducibility, polymers are still highly sensitive to damage from too much abrasion and hand sanding. Thus, maintaining uniform coverage and reproducible results can be difficult. BTG's Surface Analyst™ provides quality assurance in these situations. It verifies on the manufacturing floor whether or not a surface--may it be metal or composite--is properly prepared for adhesive bonding.
The experiment conducted in this paper examines nut plates treated with different surface preparation processes, followed by a deliberate contamination, time to age, or immediate examination. The nut plates then underwent bond strengthening tests. The results show the level of contamination that can reach a surface and how detrimental those contaminants can be.
Click here to read the full paper on the significance of contaminants and their effects on even the top few molecular layers of a surface.
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