Motorsport Composite Fundamentals: Preparation

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Preparation

09.39

00:00	In this worked example, we'll be making carbon fibre fenders for our CRX using the fibreglass moulds that we made in the body of the course.
00:07	We've already made some composite fenders using fibreglass chopstrand mat.
00:12	Again, check back to the main body of the course if you need a refresher.
00:15	Much of the process we'll be using for our wet laid carbon fibre fenders will be the same as with our fibreglass fenders.
00:21	However, we thought it would be worth showing the similarities and highlighting any differences.
00:26	In all honesty, we'd more likely use resin infusion to make some carbon fibre fenders from these moulds or at the very least vacuum bagging the wet layout.
00:35	But with that said, wet laying carbon fibre is still commonly done.
00:39	We're familiar with our moulds already.
00:41	We can show some slightly different methods.
00:43	More spare parts are always good.
00:45	And when we're done, it'll be interesting to directly compare our carbon fibre and fibreglass composite fenders.
00:50	Keep in mind, this section of the course isn't about teaching you anything new.
00:54	This is about understanding how to implement everything you've already learnt into a real world composite construction.
01:01	So, if anything has you scratching your head, check back to the relevant section of the course for a refresher.
01:07	Let's start with the first step in the process, preparation.
01:10	Every successful project starts with a solid plan.
01:13	We'll assume that the correct PPE is worn at all times throughout this worked example.
01:18	We have a suitable place to do the work.
01:20	And we have suitable tools on hand.
01:22	This includes consumables and ancillaries like mixing cups, sticks, plasticine and so on.
01:29	It's important to think through what's involved at each step, make a list of what's required and ensure you have it on hand.
01:36	We've included a list of all the tools and consumables used in this worked example that you can download and use as a reference.
01:43	Keep in mind that while some of these are essential, others are not and there's almost always alternatives.
01:48	The first stage of the practical work will be applying release agents.
01:51	We used a semi-perm chemical release agent called Chemlease on the mould during the course.
01:57	And at this stage we've only performed one pull so it's fair to say that there should be more life left in it.
02:03	We could apply another fresh coat of Chemlease but we'll use some plasticine to fix a few chips in the mould around the door jam mounting tab as we did in the course.
02:12	And then use a few coats of Meguiar's mould release wax over this and the rest of the surfaces.
02:17	This can be done at this stage to prepare the mould.
02:20	As per usual we should follow the mould wax supplies instructions.
02:24	As we covered in detail in the course, this involves wiping the wax on in a thin film with a clean cloth, giving it 5-10 minutes to haze and then buffing it with a different clean cloth.
02:35	With 20 minutes between each layer we'll build up 3 layers to ensure we get an easy release.
02:40	I like to do this with the mould sections separated so it's easy to get into all the details.
02:45	Then we can bolt our mould sections together.
02:48	The next practical job could be applying the gel coat if we were going to use one.
02:52	However, for this example we're actually going to skip the gel coat and laminate straight onto the mould surface.
02:58	The reason for this is to show an alternative option of clear coating our parts after it cures.
03:03	This way we can compare it to the gel coat process and the results from the fibreglass fenders in the course.
03:08	I also expect this to result in some surface voids, clearly something that we'd always be trying to avoid.
03:14	And while we will try to minimise them during the layup, the fact is it's very hard to wet lay a part like this and avoid them completely.
03:22	The benefit is that we'll be able to show you how to fix these voids if you end up with them.
03:27	We'll also forgo the use of resin bog that's used in the course for the same reason.
03:32	We'll laminate these fenders with the same wax polyester laminating resin used in our fibreglass fenders.
03:37	Vinyl ester is also a good option here, although it's a bit more expensive, but so is carbon reinforcement and we'll get slightly better mechanical properties.
03:46	Regardless, the process is much the same as with polyester, although we'll likely add wax to the vinyl ester to achieve a hard surface cure.
03:54	But we'll look at this in another worked example.
03:57	This brings us to the carbon fibre reinforcement.
04:00	These will be the first carbon fenders made in this mould.
04:03	And the first parts we make from a mould often serve as a bit of a trial to determine the laminate.
04:08	But, as always, we can use some critical thinking to get in the ballpark.
04:12	The thickness of the composite panel should approximately match the original steel panel to ensure good fitment.
04:18	We've also got some benefit of learning from our fibreglass fenders, which consisted of two layers of 225 GSM and three of 450 GSM, bringing us to just under 3mm total thickness.
04:30	For the mounting flanges, however, an area that's most critical to panel fitment, we use two layers of 200 GSM weave with one layer of 225 GSM chop strand mat to be just under 1mm thickness like the original panel.
04:46	The resulting part was relatively stiff without being overkill and weighed about 0.9 kgs or 40% of the original panel weight at 2.3 kgs.
04:56	Given carbon fibre has about five times higher stiffness to weight ratio than e-glass and also around 20% higher strength to weight ratio, it's fair to assume that we'll be able to get away with a lighter laminate.
05:08	Strength isn't overly important for these fenders, they're not structural, they might need to handle some impact, but this isn't their purpose.
05:16	The main purpose is to guide the airflow, so they'll still need to be relatively stiff.
05:20	With all of this in mind, we'll be using three layers of 200 GSM 3K 2x2 twill weave.
05:27	Lightweight twill will conform easily to the mould surface to help prevent any bridging and as the layers are relatively light, it'll minimise print through.
05:35	200 GSM 3K carbon weave has a consolidated thickness of about 0.3mm.
05:41	So, three layers, which brings us to a total of about 0.9mm.
05:47	Bang on the original steel panel, which will help with panel gaps and fitment.
05:51	Each fender is less than half a square metre in area, so two square metres of reinforcement per fender will be plenty.
05:58	We want to avoid damaging the fabric from unnecessary handling, but it's best to prepare the reinforcement to limit the amount of work that we need to do when the resin starts to cure.
06:07	A common technique is to stabilise the fabric.
06:10	This will help prevent distorting the weave when handling, while also making it possible to cut crisp, neat edges without them fraying.
06:18	To do this, we pull some material off the roller and onto a flat surface covered in a drop sheet, ideally something like release film.
06:25	We can then use a spray adhesive designed for temporary bonding, like AirTac 2 Mega, and mist a light and even coat over the fabric from about 300mm away.
06:35	After 20 minutes or so, this should dry and be tack free, and we can see how much more stable the fabric is to handle, while still being relatively drapeable.
06:44	While we're at it, we can then make some templates from our mould using masking paper.
06:49	The plan is to have a single piece of reinforcement over the outer surface of the fender, so on the first layer into the mould.
06:56	This will push into the tight corners to get the reinforcement as close as possible to the mould surface and avoid bridging, and then we'll overlap fabric from the flanges to tie into this.
07:06	We'll transfer these templates to the reinforcement, laying them on so the toe is running at 45 degrees.
07:13	Most carbon fibre fenders we'll see on the market have the toes running at 45 degrees, rather than straight down and across the part, and there's a few good reasons for this.
07:22	Most importantly, it means that the fibres run through the bend lines for the flanges at 45 degrees, which makes these areas significantly stronger and stiffer.
07:31	Another reason is that it generally looks better, but this of course only matters for the first layer, and we can alternate between 0 or 90 degrees for each layer to get more isotropic properties.
07:42	So, with that in mind, we cut around the outside of our templates on our twill, leaving some excess material that can be trimmed off quickly as we lay it up in the mould.
07:51	We'll also cut a section of peel ply off the roll that we can lay over the back of the laminate as a final layer.
07:57	This isn't necessary, but it will help provide a consistent surface texture on the back of the laminate that simply looks a bit nicer.
08:05	The peel ply will also help soak up a bit of excess resin, and we'll be able to tear it away from the laminate once cured.
08:12	Rounding back to our resin, a 1mm thick laminate with half a square metre of surface area and target resin to fibre ratio of 50% means we'll be using around 500ml of resin.
08:24	But realistically, these fenders probably have less surface area than this, so as long as we have about a litre on hand, we'll be good.
08:32	That concludes the preparation stage, so let's summarise the key considerations for our first step.
08:37	The first things to consider are the workspace we'll use, having the correct PPE, as well as tools and consumables that will be used at each step.
08:45	To prepare the mould, we filled some details with plasticine, and then followed this with a few coats of mould release wax for good measure.
08:52	We're foregoing the use of gel coat and resin bog for this example to show a different approach to our fibreglass fenders, show you how to fix any surface voids if we end up with them, as well as apply clear coats.
09:04	We're going to use a waxed polyester laminating resin and catalyse it with MEKP.
09:09	It's always important to ensure that we have enough resin on hand and it's within its shelf life.
09:14	For our carbon fibre reinforcement, we'll be using 3 layers of 200gsm 3k twill.
09:21	This should provide plenty of stiffness, while also matching the original panel thickness for good fitment.
09:26	We've also stabilised our reinforcement fabric for easier handling and cut some sections from templates to reduce the amount of work once the resin begins to cure.