'Forged Carbon Fibre' in F1?

Here are our CFD links and discussions about aerodynamics, suspension, driver safety and tyres. Please stick to F1 on this forum.
FightingHellPhish
0
Joined: Wed May 10, 2017 9:47 am

Re: 'Forged Carbon Fibre' in F1?

Post by FightingHellPhish » Mon Mar 12, 2018 8:43 pm

Tim.Wright wrote:
Mon Mar 12, 2018 8:20 pm
e36jon wrote:
Mon Mar 12, 2018 3:11 pm
I don't want to oversell myself on here. I worked for a couple of years at Hexcel composites R&D as an engineer, but am no longer in the field.
So is forged carbon basically an evolution of Hexcel's Hexply tooling material which I came across around 10 years ago?

I've recently seen some forged carbon parts on some luxury sports cars but in non structural applications where fibre to resin ratio isn't as critical.

Using the term forged in this application is a bit of a misnomer. Forged metallic parts benefit from a compressed outer layer of material to give improved fatigue resistence. As far as I know forging a composite part doesn't compress anything, it just squeezes resin out to help the part conform to the mould so there is no performance benefit. It's done for cost reasons as it's cheaper than a manual layup.
Isn't the sesto elementos chassis forged carbon?

What I havent seen mentioned is what sort of pressures are used in forging composite material together. I would think with the right pressures and relief for resin to flow out the ratios could be fairly easily controlled but hey thats why I'm wondering out loud.

Rodak
5
Joined: Wed Oct 04, 2017 2:02 am

Re: 'Forged Carbon Fibre' in F1?

Post by Rodak » Mon Mar 12, 2018 9:26 pm

Full disclosure: I was involved in composite toolmaking in aerospace for quite a few years and worked on the B2 bomber producing the (stupid) rotating refueling receptacle, was involved in the C-17 wing to body fairing program and duct work, worked in a company that produced composite engine nacelles and various other composite parts, worked for a company that produced parts for Boeing, etc.

I think the term 'forged carbon fiber' is a VERY poor descriptor; what's actually being done, as some one mentioned above, is making parts with both an inner and outer mold line, obviating the necessity for vacuum bagging with bleed cloth or release film. An acquaintance of mine was producing motorcycle muffler shrouds in carbon and used such a process. The prepreg was laid up on an aluminum mandrel then an outer steel mold with a slight taper was placed over the layup and it was bagged. When autoclaved to 350°F the aluminum expanded much more than the steel, compressing the layup and producing a very nice surface finish. It was pretty slick and saved a load of time and material. I think the 'forging' process is similar.

As far as resin ratios, prepreg is manufactured to an optimum ratio; excess resin just adds weight and reduces strength. When the layup is bagged, an absorbent layer is incorporated to capture any excess bleed resin during the cure as well as provide a path for air to be removed by the vacuum ports; don't forget that the autoclave is pressurized to more than 100 psi with nitrogen. There isn't much resin coming out, however. Resins are designed for different temperature cures, from fairly low temperatures to very high, depending on what use the part is designed for. The layup orients carbon direction for carry loads; for example, unidirectional tape has fibers parallel to each other and can be used to direct loads. Many weaves are available and ply orientation is very critical for strength. A layup might have ply orientations of ±90°, 45°, etc, depending on what is required of the part. Layups can be many layers and incorporate nomex honeycomb or other materials for stiffness. An adhesive layer without fibers can be used as the first ply to provide a clean, smooth finish.

Forged carbon fiber? I'd like to see a press or forging hammer work cured carbon material.......

e36jon
39
Joined: Mon Apr 25, 2016 1:22 am
Location: California, USA

Re: 'Forged Carbon Fibre' in F1?

Post by e36jon » Tue Mar 13, 2018 3:29 pm

Rodak has it nailed.

I don't know about the Hexcel tooling compound, sorry. My time there was mostly focused on 'Advanced Fiber Placement', and the prepreg tow that the process uses.

With the forged carbon, having done zero research, I don't know if it's a thermoplastic resin, or a thermoset. If it's thermoplastic then 'Forged' feels a bit more real, as the process would start with a block of material that is fully cured. It would be heated to soften the resin, and then 'forged' with the matched dies. Dies retract and boom, there's your part. If it's thermoset it would be a frozen block of material that would be heated to room temp and then 'forged' into shape, but then have to be cured in the tool. In both cases the resin ratio was set when they made the precursor blocks, so no resin bleed during the forging process. (Guessing. Total speculation. Your results may vary. Etc.)

The closest thing to the 'Forged Carbon' process is probably working with 'bulk molding compound'. (There's another name for this I can't recall.) The compound is chopped glass and resin in a pre-cured sheet that can then be pressed into all kinds of shapes that are 'done' when the press opens. Corvette body panels are made this way.

FightingHellPhish: I don't know about the Sesto Elementos chassis. I doubt that it's this exact 'Forging' process. There is a version of 'chopped' carbon fiber that is a more deluxe version of how you make a bass boat hull. That would make more sense and look almost identical.

OK, off to work...

Jon

Maritimer
9
Joined: Wed Sep 06, 2017 8:45 pm

Re: 'Forged Carbon Fibre' in F1?

Post by Maritimer » Tue Mar 13, 2018 5:09 pm

It's just a marketing term, people read too much into it. Leftover scraps loosely oriented like OSB, moulded and cured in a form. If anything it's closer to die-stamping than forging as you aren't hammering it into shape.