F1 body parts - a question.

[El Sid]

I know that Carbon-Fibre is used extensively in the construction of chassis parts but what is used for the "body" parts. In the old days a lot of fibreglass was used but what is the modern trend ? Polycarbonate maybe?

Just wondering.

[raptor22]

Actually the load baring component of the composite in the chassis is the Aluminium honeycomb sandwhiched between the layers of carbon and kevlar. The carbon mostly takes cae of the tensile forces where the AL honeycomb handles the compressive forces. The kevlar will take care of the impat resistance and the resin holds everything together so that they're all nicely aligned as the designer intended.

For the body parts they mostly use carbon fibre. Glass fibre is too heavy. There may be a layer of glass sandwhiched between the carbon to reduce total cost but the main component is Carbon Fibre reinforced Epoxy Resins.

[raptor22]

Ok In responce to a question by Elsid,I'll try to explain what exactly an F1 cars chassis is made of.
The term carbon fibre gets thrown around rather loosely by commentators and F1 engineers alike.
But what is this mystery material?

Well it's more accurate to call them Composite Materials.

Carbon fibre is just that, strands of carbon woven together like string and then held in place by a thermo setting plastic ie Epoxy or polyester or even a phenolic.

But for a race car chassis a sheet of arbon fibres held together with resin is not stiff enough to provide the structural rigidity needed for a race car. These simple sheets are best used for non load carrying components like body work, ie engine covers.

To make any structure stiff you need to give it a property called Resistance to bending or Moment of Inertia (more accurately seocnd moment of area to engineers).
if you take a rectangular shape it's basically the cube of the depth of the section x the width divided by 12.

Clearly to maximise the stiffness yu have to maximise the depth around the plane of bending or simply place as much material away from the axis of bending as possible.
No to build up a composite structure to have great depth to achieve stiffness will give you a vry heavy structure. It will be stiff but heavy. Surely there is a better way?

Yes there is:


Only use the load carrying material at the furthest point away form the axis of bending and use a very light weight low density material to separate those surfaces. And thus the Sandwhich composite structure was born.

This consists of carbon fibre or glass fibre or Kevalr or any other highstrength fibre (wood veneer also works well) placed far away from the axis of bending. The core is the honeycomb structure. This can be polyurethane foam, light weight wood like Balsa, polystyrene foam, or polyaramid Honeycomb which s the lightest, but not the most crush resistant.
So Aluminium honeycomb was created.
Picture a bee hive structure in aluminium and you'll get teh idea here is a picture if you're still confused



The aluminium honey comb carries all the shear stresses and crushing stresses Ie impact resistance and the carbon and aramid fibres carry the tensile loads, the resin carry's the compressive loads.

Now the race car chassis needs to have impact resistance to withstand the impact loads in the crash test. That performance cannot be achieved without a structure such as this. A simple carbon fibre lay up would just not hold up.

Unfortunately many people use carbon fibe for the sake of it and not because thereis actually a benefit.

I hope it's more clear now what this type of structure looks like and why. Any more questions on the subject I'd be very happy to answer.

[Henrik]

And thus the Sandwhich composite structure was born.

Hmm, I usually prefer chicken sandwiches, but ham and cheese composite structure is not bad:

Okay, I'm on my way out, but I'll leave the coat because it is too damn hot here!!!

P.S. Raptor, thanks, very instructive and interesting.

[raptor22]

cheese tomato and onion is my persoanl favourite with lightly buttered brown bread.
Hmmmmmmm nice and composity....
getting hungry now

[daSilva]

Carbonfibre
In the beginning of the sixties, Colin Chapman, chief designer of Lotus, introduced the monocoque to formula one by placing thin plates around the bars of the monocoque. This new technology increased the stiffness of the chassis. Later on in the seventies, aluminium was mostly used for these constructions, but when these structures porved not be be resistant enough for the wings' downforce, John Barnard examined and produced as a first the self supporting chassis from carbonfibre. The engineer fom McLaren he had it produced by the American company " Hercules Aerospace" because McLaren didn't have the materials and knowledge to do this. In 1981, the McLaren drivers proved the safety and advantages of the new way of construction. John Watson finished two times second and once first in that season. Andrea De Cesaris proved the stiffness of the monocoque, with the plenty of crashes he made in that season.

Properties
Carbonfibre is a non isotrope material. That means that all fibres have to point the same direction as the forcelines through the material. If this is not the case, there will be an opposite effect. To be understandable, wood is also not isotrope, aluminium and copper are for sure.
You can also notice on the table that carbon fibres are 3 times stronger and more than 4 times lighter than steel!

Tensile strength Density Specific strength
Carbon fibre 3.50 1.75 2.00
Steel 1.30 7.90 0.17

Production
Most commonly, carbon fibres are produced from the polymere PAN, so we will only consider this type of manufacturing. After an improved Sohio process which involves an amonoxidation reaction between propene and ammonia, the result is acrylonitrile, which transforms into polyacrylonitrile after polymerisation.

Once this polymer has been produced, the manufacture of carbon fibre can proceed. The first step of the process is to stretch the polymer so that it is parallel to what will eventually become the axis of the fibre. Once this has been done, the polymer is oxidised at 200-300°C in air, which removes hydrogen and adds oxygen to the molecule and forms the basis of the hexagonal structure seen above.
The white chain polymer had now become a black ring polymer, that has to be purified by carbonisation. This involves heating the polymer to up to 2500°C in a nitrogen rich environment, which expels impurities until the polymer contains 92 - 100% carbon, depending on the quality required for the fibre. The final stages in the production of carbon fibre involve weaving the fibres into sheets and embedding them in an epoxy resin, also called sizing. The result are sheets of black carbon fibre, that can be used to produce a variety of products.

Building in F1
F1 teams use carbon fibres, a pre-impregnated epoxy resin and an aluminium honeycomb layer, which is sandwiched between two layers of carbon fibre.
The chassis is usually the first part of the car to be built, due to the amount of time required. The main chassis usually comprises of about 8 parts (panels). The first stage of the manufacturing process is to build a solid (computercut) pattern, from which a mold for the panel is produced. The molds are constructed by laying a total of 10 layers of pre-impregnated (with resin) carbon fibre on top of each pattern to produce the mold. The production of the mold takes place in several stages, involving vacuum treatments, debulking and heating processes. The mold then has to be thoughroughly cleaned and prepared for use.

The next phase is the actual fabrication of a car part, made from sheets of pre-cut, pre-impregnated carbon fibre, which are carefully laid inside the molds. It is thereby vital orientate the carbon fibre sheets in pre determined directions in order to achieve the desired strength. A total of 5 layers of carbon fibre are laid, forming the outer skin of the chassis (to achieve a final, cured thickness of 1mm, a total of 3-4 layers of carbon fibre must be laid down).

The next stage of the process is to cure the carbon fibre in an autoclave. This exposes the carbon fibre to a number of temperature / pressure cycles according to the specific requirements of the materials and components being processed. During this treatment, the resin impregnated in the carbon fibre flows into the surrounding fibres and is activated, thereby curing the carbon fibre. Once the outer skin has been cured and cooled down, a honeyomb layer of aluminium is fixed onto the outer skin by a sheet of resin to ensure the materials stick stongly together. The chassis panel then returns to the autoclave for curing. After having cooled down again, one more layer, consisting of a number of pre-impregnated carbon fibre sheet is placed on top the existing skin, and again treated in the autoclave for a final time.

When the part is completely produced, it is sent to an evaluation department, and when proven good, it can be used for racing.

[DeadCat]

da silva,

You may be forgetting the chassis design of a certain Aussie driver….. (Think it was ’66)

(DeadCat)

[raptor22]

Hmm,
Would you mind if I have a go at correcting the inaccuracies in that article? The general process is right but theres detail there thats incorrect.
Also judging by the langage it's not your original work Da Silva, your use of the english language is a lot better. I suspect thats where the inaccuracies come in.

[El Sid]

Just give me a little bit of time to pull myself towards myself. It's difficult to think while your mind is boggled. Maybe I should say, "Yes I know that, but how does it work?"

No, I really have to confess that the whole business is a lot more complicated than what I would have imagined. My structural analysis/design/theory goes back quite a long time but some of the terminology used here brings back quite a few good memories of my bridge building days.

One, at least, is this: "Pre-Stressing". Pre-stressing is extensively used in obtaining slender and aesthetically appealing bridge decks. Whether by pre-tensioning or post-tensioning of steel strands (cables) embedded in the concrete. Sorry if this snippet seems to distract the attention from the carbon-fibre/chassis subject. I brought this in to pose a question. A while back Eddie Irvine was saying something about Ferrari's flexible floor pan. Maybe this is a wild shot in the dark from me, but would it not be possible to pre- or post-tension the chassis such as to remotely control the characteristics of the floor-pan? If you could, would it have advantages? Would it be legal? Would the FIA be able to police it?

Now, just another question; Do I have nuts or am I nuts? In the meantime I'll get all of my belongings and leave. Yes, and I will shut the door behind me.

[raptor22]

ElSid,
The design process for a composite structure is similar to that used for reinforced concrete. So yes you can prestress certain elementsto obtain greater stiffness in a certain plane.
The problem with Eddies theory is that even if they prestress certain oriented fibrs in the composite the external control of the deflection still requires outside energy which has to come from the engine via a generator.

One, at least, is this: "Pre-Stressing". Pre-stressing is extensively used in obtaining slender and aesthetically appealing bridge decks. Whether by pre-tensioning or post-tensioning of steel strands (cables) embedded in the concrete. Sorry if this snippet seems to distract the attention from the carbon-fibre/chassis subject. I brought this in to pose a question. A while back Eddie Irvine was saying something about Ferrari's flexible floor pan. Maybe this is a wild shot in the dark from me, but would it not be possible to pre- or post-tension the chassis such as to remotely control the characteristics of the floor-pan? If you could, would it have advantages? Would it be legal? Would the FIA be able to police it?

part of the contruction phase of the chassis is prestressing the material to gain stiffness and strength. So to manufacture the structure to bend where under piezo electric control or not would be counter productive to achieving a stiff chassis.

However that said, the most obvious application for smart materials is in active vibration and noise damping.
What the material does is sense the bibration of the structure and apply a 180degree out of phase pulse to create a cancelling vibration thus making the surface less active to the airflow.

If the underside of a race car chassis is damped in this manner it will improve the efficiency of the airflow by reducing the turbulence transferred to it from the chassis.

This is legal and is what every designer strives to achieve.

If these materials were ever built into a Ferrari then this I would guess is it's function, not to bend the underside, but to dampen the vibration of the floor.

[daSilva]

No it is not mine, I apologise for not referencing it. The most interesting part and the reason I posted it was for the production paragraph.

[raptor22]

Ok 'll leave it that then. That part of the article is pretty accurate.

[Topcontender]

OK for us non tech folk, all you are saying is that they make a aluminum honeycomb middle, and placed some kevlar or other hard/stiff on the outside. is that about right?

[raptor22]

bingo