Composite Structures in Aircraft-Are they safe ?

[wonwinglo]

http://www.yachtsurvey.com/composite_troubles_in_aircraft.htm

There has been questions in the past about the use of composites in aircraft structures,many light aircraft have super critical wings which do not allow paint a third of the wing leading edge,there have been structural failures with carbon fibre on the Concorde rudder,now it looks as if more problems have come to light,read this latest report and judge for yourself ?

[Guest]

bloody hell!!!!

[wonwinglo]

***Indeed,and what exactly was the liquid around the rivets and bolts ? are the materials breaking down internally ? this really is a serious problem and should not have been afffected by any heavy boot on the rudder.

bloody hell!!!!

[Guest]

I suspect that the liquid being referred to is propably glue or resin used in the initial construction rather than some core material breaking down into a liquid.

Whereas it looks freightening lets not forget that we have had significant failings in the past with more traditional materials and, when you are taking strengths of materials to the edges of thier envelopes in order to squeeze the last scrap of performance, economy and efficiency out of something, things will occassionally fail.

We have similar situations in the marine world. When I first went to sea and looked after large slow speed diesel engines if anything went wrong you had plenty of time to do something about it and avert a disaster. Nowadays with medium speed engines with all the internals trimmed down to the minimum, cooling water relying on flow rather than volume and every parameter of the engine design taken closer to the edge in the search of increased performance and efficiency, when something goes wrong your best course of action is duck!

[wonwinglo]

Very true what you say Richard,I think that one of the problems that arise with composites is the formers or strengtheners that are added during the build,for example metal encased within fibreglass or composite material does not fair well,chemical reactions attack the formers and slowly degrade them,it is the same with concrete and metal in building roads,the concrete attacks the metal and corrodes it,ok for a few years but then when the concrete blocks start to fall off as they did around this area,then it is cheaper to replace rather than make good.

The problem with the aircrafts rudder assembly is that it is relatively weak in comparison with the other parts of the aircrafts structure,it takes a lot of buffeting as well in the aircrafts slipstream.

This composite failure thing is not new either,there have been cases of complete flap assemblies breaking away in flight on large transport aircraft,like a lot of things it is relative to a lot of factors,ie humidity,vibration,use beyond that originally intended by the manufacturer.

Like a lot of modern materials nobody really knows the lifespan of these materials,that is why they are not very popular with the certification authorities,who knows they could degrade quicker than at first imagined ? only the test of time will tell with a few failures along the way.