Friday, April 16, 2010

Gluing a Plane Together

It is not widely known by the general public that aircraft wings are usually glued on to the plane, not rivoted, bolted, or using some other mechanical fasteners. Which means that a thin layer of polymeric material is what is holding the plane up in the sky. It's not the wing or the engine or the Bernoulli principle [1], it's the polymer adhesive.

I've little experience in aircraft construction, so I don't know about how other parts are attached, specfically the tail section, so this report on a new welded thermoplastic tail section caught my interest. Thermoplastics tend to deform more easily than thermosets [2] so I thought that their use would be avoided - although the tail is made of PPS, a pretty tough plastic. But more than that, I'm not sure what advantage there would be in the welding operation, as it would require more expensive equipment than a standard adhesive bond (again, I am assuming that it is an adhesive that is used). Apparently the entire tail is made of PPS, cetainly a weight/fuel saving move.

[1] O.k., so I'm overplaying my hand a bit. There is a chain of linkages that holds a plane up - but the adhesive, being small and invisible, doesn't get the credit it deserves.
[2] A plot of the mechnanical properties for thermoplastics and thermosets would show two peaks with overlapping tails. The averages are clearly offset, but there are still specific examples that contradict the averages.

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