PPRuNe Forums - View Single Post - Fired engineer calls 787's plastic fuselage unsafe
Old 20th Sep 2007, 07:40
  #52 (permalink)  
Orographic
 
Join Date: Dec 2006
Location: head in the clouds
Posts: 27
fish

The issue is as Weldon succinctly puts it, the very low amount of linear strain before the composite material fails. In other words, it's main failure mode is a brittle fracture. My observation is that the considerable number of carbon hull and mast failures I've seen are consistent with this failure mode, and as a result, are "spectacular" compared to the failure of, say, an Aluminium structure.
I shall look at the composite construction components on my aircraft now with abject terror. They have been twisted, bent, stretched and despite this they have been on the aircraft for God knows how long without rectification.
They're called helicopter rotor blades.
yes, but in rotor blade, and props, this Brittle Fracture Failure mode is desirable. They are less likely to dig in and cause more problems for a crew, who it must be said, have enough on their plates. assuming there isn't some poor sod under them, then having them shatter and nicely dissipate their excess energy in a ballistic arc is , while spectacular, generally safer for the a/c as a whole.

The question is, is it as desirable when we are talking about the fuselage itself, and indeed is it a more desirable set of traits than aluminium shows?

One question that is partly tangential, is the mass savings of moving to this material significant as opposed to aluminium, and if so, how significant or otherwise would that change be in terms of impact energy? It seems a stupid question, but I am not an engineer, and I am sure Boeing has information that I don't.
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