F1 chassis thickness

[marcush.]

+1 that was implied in my responses as well.
but actually the thickness of a monocoque in F1 is currently 28.55mm .I only forgot where ....and core thickness and ply weight, modulus ,fibreorientation and resin system..also I have just dropped the curing processparameters .

[xpensive]

I think the fact of the matter is that none of you members have a living clue of how an F1 monocoque is built up whatsoever,
just casually dropping xpressions like plies, core, modulus, fibre orientation...oh wait, you forgot surface inertia!

[Italy88]

Jersey Tom
It is obvious that we can not know every parameter of a f1 chassi..in fact in my question I've specified that the thickness is a value that changes point by point..but I'm shure that today f1 monocoque are very similar in building process and have ''typical''value of thickness for every point of them, it may be 50mm from a to B and 20 mm from C to D, for exalmple.
Of sure having images os cross sections or similar it wight be usefull..
For example, in the pdf posted by Marcush we can see that the kevlar layer is placed on the outer carbon skin of the honeycomb. It can't help me to design a chassi but my curiosity need to be satisfated

thanks

[marcush.]

I think the fact of the matter is that none of you members have a living clue of how an F1 monocoque is built up whatsoever,
just casually dropping xpressions like plies, core, modulus, fibre orientation...oh wait, you forgot surface inertia!

I´m not so sure if it is a ssophisticated as we are made to believe, remember allmost all teams experiencing cracking issues at the beginning of the year...so it still seems to be a lot of gut feeling development involved and strengthening where you find issues creeping up...

[riff_raff]

I think the fact of the matter is that none of you members have a living clue of how an F1 monocoque is built up whatsoever

xpensive,

That's a bit harsh.

Composite F1 tub structures are designed, analyzed, and manufactured using well established processes. While the members may not have intimate knowledge of the precise core thickness dimensions, ply stack and fiber orientations, anyone with a current working knowledge of autoclaved composites can probably make a good guesstimate.

The main purpose of core is to increase the buckling properties of the structure by stabilizing the inner/outer composite laminates. A secondary function is to improve impact performance. The core thickness at any given point on the tub varies, and is typically kept to the minimum required. The core thickness is usually around 2 to 3 times the skin thickness, except at the edges where it is tapered down to nothing. The skins themselves are probably 2mm or less, over the cored areas.

As for the laminate's plies and orientation, the plies are mostly unidirectional. A few 45 deg weaves are used to help stabilize the uni plies, mostly at the laminate edges and around any inserts, attachments, or open holes.

The fibers used are mostly medium and high modulus PAN materials like T800 (42Msi) and M46 (63Msi).

riff_raff

[xpensive]

Thanks for your input riff, just two things;

- I would have thought that the primary purpose of the core was to increase the surface-inertia of the sandwich profile?

- If the skin is two millimeters, I xpected the core to be more like 8 to 10?

[polarboy]

When you say thickness,you could mean the overall thickness of a finnished tub or the cores used within,an both are variable and as every composite designer has his own way of doing things it varies from team to team
Few "genral" guidelines that may help ?

1-ply thickness,averages about 1.5mm but varies throughout the whole structure,thinnest plies through the base of the fuel tank area,lots of areas where you have local reinforcement plies i.e engine mounts,nosebox mounts cockpit opening etc.Some may be very local (Top wishbone,rear mount is a good example)or you can have extra plies that cover several areas for example you fuel tank opening in the back of the tub may be near enough to the engine mounts that those reinforcements combine

2-Core,havent seen nomex in a tub for about 15 yrs its all Ali. 12mm/15mm 48 grade is round about the average but everyones diffrent
Core stiffness varies greatly thou,someone mentioned the squeeze tests.you dont increase your core thickness just its stiffness.If you looked at a side view of a tub it might be all 12mm but there would be a section of 48 grade,strip of 8.1 in the squeeze area (15cm wide running through the chassis top to bottom) another area of 48 till you get to the next squeeze area etc,You might find stiffer core where bulkheads are fitted but its normally taken down to single skin in such areas to avoid the problems of core crush
You might find thicker core due to insert design (i.e engine mounts) but its a lot more common now that the inserts themselves are blended outto match the joining core detail
The only place you will find any really thick core is the cockpit opening/sides where 50/70mm thick core is machined to do some trick shapes to create a laminate to pass the latest tests
Hope this helps any questions just ask

[riff_raff]

polarboy,

You'll have to excuse my relative ignorance on current F1 composite design. I'm a mechanical systems engineer working in aerospace. So my (limited) composite structures knowledge is more oriented to what you might see in current aircraft. I actually spent a few years doing engine/trans design engineering for a race team, but back then the monocoque tubs were still aluminum honeycomb.

In aircraft composite structures, nomex honeycomb is still most common, since it has a CTE close to carbon and there is no problem with galvanic corrosion like aluminum cores would have.

As for the skin ply thicknesses, this is mostly determined by impact/buckling requirements. A very thin composite skin composed mostly of uni-directional graphite fibers can carry massive loads when those fibers are loaded in tension. But those same fibers when side loaded or put into compression, are only as good as the resin matrix or core supporting them.

Another issue with aircraft composite structures is the connection between composites and metal. Adhesive joints almost always require a series of rivets as back-up, to prevent a peel failure.

Enjoying the discussion.
riff_raff

[marcush.]

I found this about Composite chasis ..quite new...:

http://www.google.de/imgres?imgurl=http ... s%3Disch:1

http://www.google.de/imgres?imgurl=http ... s%3Disch:1

[marcush.]

Not F1 but those pics are telling a lot:



surprisingly the bulkheads are not touching in the corners..






no seat bulkhead?

[ringo]

Well there is a realistic thickness. It can't be 3 feet or 1mm thick.

It is as thick as it needs to be yes, but then what it needs is indirectly stipulated by the technical regulations.
As long as the regulations relating to the forces that the tub should be able to take etc. So i think there should be a general range of thicknesses.

[ringo]

Not F1 but those pics are telling a lot:



surprisingly the bulkheads are not touching in the corners..






no seat bulkhead?

any videos of the laying up ?

[Italy88]

hi Ringo

http://www.youtube.com/watch?v=GVYZDsc6XWo
At the end of this video you can see the built of an F1 tube and we can notice that the thikness is nearly the same of the car in the pictures you posted. It is not clear the link of the bulkhead to te chassi. I think because is a''prototype chassi'', in fact also the head side protections are missing.

[polarboy]

Very sorry for not posting a reply sooner to Riff Raffs questions to my previous reply but work is soooooooooooo busy,but since we have some shiney new pics on the thread i thought i better add some more
Dont know if the chassis in the pic is a 1st off ? normally bulkheads are made over size an the flanges have extre sacraficial plies on the outside as you know you will be grinding them down to fit,corners are the worst as you have all the joins in the material on the chassis itself making the laminate thicker in that area(might be 2/3 mm if you have several layers of 600g material in that area)could be a bit of a design flaw leaving too big of a glue gap but normally you would of built up the flange on the bulkhead if it was a problem before you glued the bulkhead to get an acceptable glue thickness
If you look in the 1st pic in the top r/h corner above the nose of the 2nd tub you will see the bulkheads on the table ready to fit
They are fitted in one after the 2 halfs of the tub are joined,they go in sideways an are turned to fit into the chassis and are a taper fit-see the taper on the tub as it goes from the fueltank area to the seat area
Main reason for this is so the inertia of the fuel dosent punch the seatback out off the tub in the event off a crash
Main part of the tub is structual,head restraints are superficial parts bonded on afterwards
Build vid for a f1 tub would take ages,about 6 weeks build time but a tub like the one in the pics or a1GP or world series your talking5/6 days

[marcush.]

as always the longer I look the less impressed I am .