PPRuNe Forums - View Single Post - Fired engineer calls 787's plastic fuselage unsafe
Old 21st Sep 2007, 00:15
  #58 (permalink)  
Join Date: Mar 2002
Location: Florida
Posts: 5,247
The thing about race cars (especially F1) is that although the body is made out of carbon fibre, it is bonded to an Aluminium honeycomb structure (at least in the nose cone). Its the honeycomb that helps absorb the energy, crumpling in a crash.
In other race cars like Nascar the driver is sitting in a huge steel cage onto which the body is attached.
Overall though I would rather be in an aircraft than a race car (parent of a 24 year old son who wants to take father round the nurburgring before son turns 25).
I doubt that the honeycomb absorbs any significant energy. Crushing absorbs squat, it's deformation under the stress/strain curve that absorbs energy. You can take the honeycomb out lay it on a table and slap it flat with your hand, it's sole purpose is to provide stiffness to the supporting structure.

However I won't argue about the energy absorption capabilities of the race car composite cockpit shell. It simply provides lots of stiffness to distribute the g-loads evenly to the occupant. the real energy absorption takes place by the surrounding mangling of the frame and time extending bounces. One of the things that is applied is a basic crash recorder attached to the shell which records max G-loads. For the very serious crashes this is consulted before removing the occupant so as to lessen the internal trauma. (cutting out vs lifting the body out)

The argument about the composite was not it's excelent energy absorption but's it longevity throught the crash impact scenario.

So in simple opinion, in the same type of crash, both an aluminum airframe and a composite aircraft will protect or not protect the occupants relatively to the same level of survivability. in my experience I have seen both.
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