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VIDEO TUTORIAL

How to Laminate Complex Split-Mouldings using Prepreg Carbon Fibre

Professional video tutorial explaining the process for making complex parts from a multi-part split-mould using out-of-autoclave prepreg carbon fibre.

In this video tutorial we use the multi-part split-mould we made in the previous tutorial in the series to make a single-piece carbon fibre airbox. The airbox shape itself is quite complicated and requires a slightly unusual vacuum bagging technique to ensure the vacuum bag is correctly positioned and exerts even pressure onto the laminate, inside the airbox mould.

The part is laminated using the now discontinued Easy-Preg™ and Vari-Preg™ prepregs which were designed to provide a pin-hole free surface finish when cured under vacuum pressure in an oven, without the need for an expensive 'autoclave'. Both of these pre-pregs have now been replaced with our new far superior XPREG® range of pre-pregs - which are still capable of producing a pin-hole free finish out of autoclave.

Towards the end of the video we cure the part in our OV301 Benchtop Curing Oven.

Using Uni-Mould moulds with Prepregs

At the time this video was produced, the pre-preg system offered, worked well with Uni-Mould moulds for out of autoclave use up to 90°C. That pre-preg system has now been discontinued and replaced with the superior XPREG® range of pre-pregs. Although it is possible to use Uni-Mould moulds with out-of-autoclave (oven cure) prepregs (such as XPREG® XC110) we no longer recommend Uni-Mould moulds for this purpose.

Instead – for prepreg use – better results will be achieved using high temperature epoxy moulds made using our EG160 / EMP160 tooling system or XPREG® XT135 Tooling Prepreg. These high temperature epoxy tooling systems allow the prepreg to be cured at the optimum 120°C which reduces the cure time and improves the mechanical properties of the component. Additionally, epoxy tools have been found to result in a better surface finish with prepregs such as XPREG® XC110.

DISCUSSION (21)

Please share any questions or comments you may have about this video tutorial.

Mr Dee

can you cook in home oven?

Easy Composites› Matt

Domestic ovens usually lack the control and accuracy necessary to follow a pre-preg cure cycle so we would not recommend the use of a standard oven.

windthropp grumman

No de-bulk after the first ply?

Easy Composites› Matt

No. Debulk of this prepreg at this weight is unnecessary. Results will be pinhole free without and won't be improved by (a time consuming) debulk so we don't suggest it.

Gary Leafty

Can you use pre-preg e-glass to make molds?

Easy Composites› Matt

In theory yes you can as long as you have a suitable surface layer pre-preg to give a good quality mould surface.

Royal REvue

Is there a way to soften prepreg carbon fiber ?

Easy Composites› Matt

You can gently apply a small amount of heat using a heat gun which will slightly soften the pre-preg and make it more tacky.

pimpachu

Can carbon fiber stand up to turbo charger set-ups?

Easy Composites› Matt

Yes, certainly - providing your laminate thickness and the design of the component is appropriate. Depending on the location of the component, you might need to consider heat shielding and you would certainly need to ensure that you've post-cured the prepreg to increase its Tg (Glass Transition temperature). Our prepreg system can be post cured up to around 130'C which should mean the finished part can withstand hot engine bay temperatures.

FearOfPlanet

Do you guys have different colour carbon fibre weaves? Thanks

Easy Composites› Matt

In pre-preg format no. However we do have a selection of standard (dry) fabric reinforcement cloths in a 50/50 hybrid color/carbon.

Lluis Alsina

What's the best adhesive to use to bond carbon fibre parts like this?

Easy Composites› Matt

We generally choose to bond carbon fibre parts (to each other or to other fixings/fittings etc.) using a methyl methacrylate adhesive such as VuduGlu VM100.

Mato Commissions

Do you refreeze XC110 surplus XC110 when you don't need it for a while?

Easy Composites› Matt

Yes, you can do that. The out-life of the material is around 6 weeks at room temperature but if you think you might not use the material in that time then you can freeze it for at least 12 months, quite possibly a lot longer.

Riseuhh

Can you do a tutorial on how to do this but with an enclosed 2 part mold? So no holes at all

Easy Composites› Matt

Well, you would always have to have some sort of a hole if you want to make the part in one piece, even if it was just a small one that you could put an inflatable bladder into otherwise there is no means of creating pressure inside to consolidate the reinforcement. Alternatively, you make the part in two halves, totally separately, and then bond them together. A lot of seemingly two sided '3D' parts are made in this way.

Fairlady Driver Dk

What level of vacuum does a vacuum pump need to achieve, for prepreg and resin infusion processes?

Easy Composites› Matt

Vacuum level is very critical for both prepreg and resin infusion. The higher the vacuum, the better the results you will achieve. You really need to be as close to -1 bar as you can possibly get. Our DVP pumps achieve 99.98% vacuum (2 mbar / 29.92" Hg) and this produces great results. On a conventional vacuum gauge you would need to be showing basically -1bar.

Grant Goldner

Could this same process be followed using non-prepreg resin carbon fibre, resin infusion for example?

Easy Composites› Matt

Yes, in theory. For a complex component like this though, especially where you need to work inside a small cavity, resin infusion would be practically very difficult; imagine trying to get the reinforcement to stay in place, then the peel-ply, mesh, spiral and other consumables. You would have to contend with the issue of setting up and positioning the infusion lines which really would have required larger flanges. In reality, a part like this is easy to achieve using a prepreg layup but would be REALLY tricky for infusion. On the other hand, larger, flatter components (like body panels) lend themselves very well to resin infusion and are as easy to do that way as prepreg would be. The exception, for tube production, would be scale; for a really large diameter tube, such as those used for water or gas in civil engineering, resin infusion is often the preferred method of production.

Peter Gal

Is it possible to use an FDM 3D printed mould with this material ? for example a mould made out of ASA Acrylonitrile styrene acrylate

Easy Composites› Matt

We haven't tried this specifically but I would have two concerns; one being any outgassing from a Styrene based material and secondly being whether the ASA has a suitable enough HDT to be able to work at the higher curing temperatures required to cure the Prepreg.

Matt Apple

I wonder how important the temperature during the curing process of the carbon fibre really is, does it make´s the material really that much stronger ?

Easy Composites› Matt

Yes Matt, in the case of curing a prepreg material like we used in this video it simply won't cure without elevated temperature. The precision on the temperature (in terms of ramps and dwells) is more important for out of autoclave prepregs (like our XC110) but you will always find that prepregs have a cure cycle. It's often not a matter of the exact cure cycle making the cured laminate stronger but rather controlling the temperature in order to prevent an exotherm or to ensure proper resin flow.

Dattatreyer Mayala

When forming the overlaps, the thickness of the carbon fibre is doubled. What can be done to ensure an even wall thickness without these thickener areas?

Easy Composites› Matt

For the majority of the 'overlap' the thickness of the laminate is not increased because where one side is cut longer the opposite side is cut correspondingly shorter. There is a tiny fraction of the overlap where there is an 'overlap of the overlap' but this is just a few millimetres and eliminates the weak point that would be caused if it was just a butt-join. Unless you're using a continuous piece of material, such as a woven sleeve, then you will always have a join. At the join, you must decide between a tiny overlap - resulting in no weak point, or no overlap - resulting in completely consistent wall thickness.

Kevin Ross

Why use the tape template to cut the signboard template, then the signboard template to cut the prepreg? Why not tape template direct to the prepreg? To reuse?

Easy Composites› Matt

Yes, it's so that they can be retained and used over and over. If it was just a one-off then we wouldn't bother.

Big Yak

Could this process and material be used to make a motocross clutch cover? It has a hard life! Would I need more layers to make it stronger, and if yes, how many?

Easy Composites› Matt

In theory, yes, it should be possible - you would need to incorporate some of the fibres at +/-45 degrees as well as 0/90 to ensure you had uniform mechanical strength in each direction. As a starting point, I would recommend matching the thickness of the original part if made in metal - doing so will result in a lighter finished piece but with similar overall strength.

Faruk SANAL

Does the final product have all the benefits of carbon fibre? Sure lighter but is it now really stronger than steel? Or, is this just a quick way of making exotic parts?

Easy Composites› Matt

The final product has all the benefits of carbon fibre because it is carbon fibre. There is really not much further you can go in terms of the performance of a composite part. The only step left would be exactly the same process but curing with positive pressure rather than vacuum pressure (i.e. in an autoclave) but realistically that would improve the mechanical performance by maybe a couple of percent at most.

streets1994

How do F1 teams make their carbon fibre chassis with aluminium honeycomb? Is the aluminium just glued into place and the curing of the carbon fibre layers on each side hold it together?

Easy Composites› Matt

There are a number of different ways in which aluminium honeycomb is incorporated into composite structures, like an F1 monocoque, but most typically the inside skin and the outside skin are laminated and made separately. Once cured, the skins are assembled either side of the honeycomb core and a prepreg adhesive film (such as our XA120) is used to bond the skins to the honeycomb. The whole assembly is then vacuum bagged again and then heated again in an oven or autoclave to cure the adhesive film. Because the inside skin, outside skin and honeycomb bonding are all done as separate stages, this process is commonly known as a 3-shot cure.

DersNoNem

I was wondering if a hollow carbon fibre part could be strong enough to be used as a swingarm on a motorcycle. How many layers of carbon fibre would be needed to achieve the required strength?

Easy Composites› Matt

Yes, it would be possible to make even a highly structural component like a motorcycle swingarm as a 'hollow' component (in fact, this is how they are made) however you would need be 100% confident of your calculations regarding the thickness, shape and ply orientation to ensure a strong and safe component. If you're new to carbon fibre fabrication then a safety critical and highly loaded component like a motorcycle swing-arm would not make a good starting point but there's no reason you can't work towards these sort of components as your skill and knowledge increases. As the for the laminate thickness itself, there is just so much that would need to go into this calculation, particularly in terms of the geometry of the arm and the specifics of the load, that it would be inappropriate to even give a suggestion as to the right number of plies without an awful lot more information.

TIM MONTANO

How much suction is needed when vacuum bagging the wrapped part? Would attaching the suction hose to a common heavy duty shop-vac be sufficient or does it require much greater amounts of suction to pull out any air bubbles?

Easy Composites› Matt

To properly vacuum bag prepregs your vacuum pump needs to be capable of high levels of vacuum (99.95%/29.9 in hg) or better. A vacuum cleaner unfortunately is more like 25% vacuum and so nowhere near the vacuum level needed for prepregs.

mirceaandreighinea

Once the oven/part reached the desired temperature, say 80°C degrees, can you shut down the pump, so that the remaining hours in the oven is without pump working (having made sure, of course, there is no leak in the bagging)?

Easy Composites› Matt

In an ideal world, with a perfectly sealed bag, you would not need to run the pump continuously through the cure. In reality though, sometimes caused by a bit of settling with the heat in the oven, or otherwise just down to microscopic leaks, it would be quite common for a vacuum bag to lose some bag pressure over the time of the cure, if there was not a continuous vacuum supply to the bag, the consequences of which would be a ruined part. By having the pump running throughout, tiny leaks like this are not a problem. Most good quality pumps, such as our DVP EC.4, are quite happy running very long duty cycles are so are more than capable of running for the duration of a prepreg cue cycle.