Frame configurations for an aircraft fuselage

[AF1307]

Hi, I'm trying to look into the benefits and disadvantages of different types of frame configurations for an aircraft fuselage assignment. The three options I have at the moment
1) is a mechanically fastened C+L Frames,
2)a Z Frame with some local pad ups on the web and
3)a one piece C+L Frame.

All parts are to be made from CFRP.

Structurally options 1 and 2 should be the most appropriate as the have a significant moment of inertia component. Whereas the 2nd option is not as structurally sound however, would be easier to manufacture. Option 1 would allow for ease of manufacturing but assembly time would increase. Whilst option 3 would be a little more difficult to manufacture and if the part fails to confirm and needs to be redone the material wastage is higher.

Are the points above valid and are there any other significant points I should consider?

If we divide the overall input into firstly
1) pros/cons from the structural perspective then
2) manufacturing/assembly input

This will help to make a rounded decision.

Please see attached for diagrams.

Thanks

 

[drawoh]

You asked this question in the structural forum. At least you included the figure this time.

What are you trying to do, support a floor?

You can work out the cost of your supports, and the ease of manufacture. You can work out the strength and rigidity of your parts. This will answer your question.

--
JHG

 

[WKTaylor]

A few points to consider...

Ref the these shapes would be a 'no-brainer' if MF extruded metal alloys.

HOWEVER...

CFRP shapes as You described [in the simplified illustrations] can be very complex to produce 'high quality/defect-free'... so start 'there'.

Joining composites is also an 'art-form' backed-by a lot of science, regardless of joining methods: Fastened or adhesive-bonded or fastened-bonded.

Hopefully some of the composite guys will enlighten us on the subject.

NOTE. Be 'open' to considering alternative designs!

Do You have a copy of CY Niu's book Composite airframe structures: practical design information and data ISBN 9627128066 ???????

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[AF1307]

The Frame is there to support the entire fuselage skin. Whilst there are locations whereby floor beams and struts will be connected, the focus is mainly on a general approach in the acreage area. The indicated topics (Cost, Ease of manufacture and strength) are of course the main focus in the evaluation. It is these specific topics I am hoping to gain feedback from the said experts in these fields. Cost will be a contentious topic based on the limited input (material type, labor costs, utilities etc) but structures and manufacturing input will be greatly appreciated.

 

[AF1307]

Thank you for the pointers.

 

[drawoh]

AF1307,

You have isolated a tiny part of your design problem. How will your structures be attached to your frame? How many of those things will use use around a given circumference of frame? What kind of airplane is this? How will you abuse the airplane? Are you building the next Airbus A380, the next stealth fighter, or a new bush plane for Alaska.

--
JHG

 

[AF1307]

The aim is for the frame to be mechanically fastened to the skin of the aircraft and in the case of scenario 1 the L frame (Cleat) will be fastened to the C Frame. As for the abuse of the aircraft, it will serve as a commercial aircraft similar in size, payload and operational conditions to a wide body (787, A350).

 

[RPstress]

Option 2 should be most weight efficient and lowest cost too.