Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Lighter, Arched Cabin Floors?  
User currently offlineFaro From Egypt, joined Aug 2007, 1572 posts, RR: 0
Posted (5 years 5 months 2 weeks 6 days 9 hours ago) and read 2673 times:

Would a slightly up-arched passenger cabin floor be a practical way to reduce airframe weight?

I may be wrong but from what I recall, metals have greater resistance to compressive than to bending or tensile loads. Conceivably, if an arched cabin floor were to involve mainly compressive loads (or a greater proportion of compressive loads), one could make it lighter for a given floor load than a normal, level floor. The degree of convexity need not be significant and would not be too apparent to passengers, perhaps only resulting in seat sides which are slightly divergent instead of being perfectly parallel to each other.

If the floor's points of attachment to the fuselage can handle the lateral loads resulting from such an arrangement, could this be feasible?

Faro


The chalice not my son
4 replies: All unread, jump to last
 
User currently offlinePhollingsworth From United Kingdom, joined Mar 2004, 825 posts, RR: 5
Reply 1, posted (5 years 5 months 2 weeks 6 days 5 hours ago) and read 2623 times:



Quoting Faro (Thread starter):
I may be wrong but from what I recall, metals have greater resistance to compressive than to bending or tensile loads. Conceivably, if an arched cabin floor were to involve mainly compressive loads (or a greater proportion of compressive loads), one could make it lighter for a given floor load than a normal, level floor.

Actually they do better with tensile loads. The ultimate tensile stress for most metals is significantly above the compressive yield stress (in most cases the tensile yield stress is also greater). Add to that the fact that when dealing with compresive loads you often get a buckling or crippling failure are stress levels below yield, you want to avoid tom much compression. Remember the upper spar or skin is usually the first part of the wing to fail. That being said, the reason you see a lot of "arched" members is because you are starting with what is effectively a negative stress in the member. In this case the upper beam cap would start in compression and the lower cap in tension, then as it is loaded the stress would move from tension to compression and vice versa. This is what pre-stressed concrete is all about. The thing about most floor beams is not the load from above, but the tensile load that is transmitted across them to maintain fuselage barrel integrity as a result of the cusp.


User currently offlineFaro From Egypt, joined Aug 2007, 1572 posts, RR: 0
Reply 2, posted (5 years 5 months 2 weeks 1 day 6 hours ago) and read 2288 times:



Quoting Phollingsworth (Reply 1):
Actually they do better with tensile loads. The ultimate tensile stress for most metals is significantly above the compressive yield stress (in most cases the tensile yield stress is also greater). Add to that the fact that when dealing with compresive loads you often get a buckling or crippling failure are stress levels below yield, you want to avoid tom much compression. Remember the upper spar or skin is usually the first part of the wing to fail.

Thanx for the feedback, learned something there.

Does the above also hold true for CFRP or this a more complex issue?

Faro



The chalice not my son
User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 3, posted (5 years 5 months 2 weeks 13 hours ago) and read 2207 times:



Quoting Faro (Reply 2):
Does the above also hold true for CFRP or this a more complex issue?

It's true in general, but CFRP lets you tailor the properties along different axes, and also has the yield stress much closer to the ultimate stress, so it tends to perform better.

Tom.


User currently offlinePhollingsworth From United Kingdom, joined Mar 2004, 825 posts, RR: 5
Reply 4, posted (5 years 5 months 1 week 3 days 2 hours ago) and read 2030 times:



Quoting Tdscanuck (Reply 3):
It's true in general, but CFRP lets you tailor the properties along different axes, and also has the yield stress much closer to the ultimate stress, so it tends to perform better.

Yes, the beauty of an-isotropic materials. Also because they typically have a higher stiffness many composites have higher buckling and crippling stresses.

Oh, it looks like I swapped my upper and lower beam caps in the previous statement. The upper cap should be in tension and the lower in compression prior to loading (for a floor or bridge beam).


Top Of Page
Forum Index

Reply To This Topic Lighter, Arched Cabin Floors?
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
737 Cabin Crew Manual? posted Tue Mar 3 2009 12:07:19 by Dogfighter2111
Cabin Air, From Which Direction? posted Sun Feb 15 2009 12:29:28 by Readytotaxi
Boeing 787 Dreamliner Cabin, How Silent / Noisy? posted Wed Feb 4 2009 04:34:43 by Keesje
Cabin Cleaning posted Tue Feb 3 2009 19:40:44 by ChewingPlastic
First Choice Cabin Service posted Sat Dec 6 2008 09:01:37 by Rdwootty
744 Upper Deck Cabin Width posted Wed Nov 19 2008 14:20:15 by LY777
Luggage Bin Replacement On Cabin Upgrade? posted Sun Nov 16 2008 04:29:38 by Sandyb123
Does JetBlue Remotely Monitor The Pax Cabin? posted Thu Nov 13 2008 16:39:19 by Luv2cattlecall
757 Cabin CRT Replacement With LCD - Why Not? posted Wed Oct 22 2008 16:29:37 by Nuggets
Unique Cabin Smell In Days Past posted Sat Sep 20 2008 10:11:47 by SmokinL1011

Sponsor Message:
Printer friendly format