Motorsport Composite Fundamentals: Preparation

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Preparation

09.51

00:00	In this section we're going to cover the practical construction of composite parts.
00:04	We've already had a taster of composite construction with our mould making in the last section, using the same wet layout, hand lamination and open cure techniques that we'll be using in this section.
00:15	We'll continue with our CRX fenders example using these moulds that we pulled from our modified CRX fenders to produce some fiberglass fenders.
00:24	If you'd planned on making carbon fiber parts, don't worry, we'll also be producing some carbon fiber fenders as a worked example, so be sure to check that out in the library, which will also be added to over time.
00:36	We've simply chosen fiberglass in this case because it's the most accessible, affordable and arguably easy to work with option, making it a good fit for our fundamentals course.
00:46	Fiberglass parts are also tough, so it's not a bad choice for fenders that will be used in wheel to wheel racing and that will likely take some damage.
00:54	But just understand that the ideas are the same, whether wet laying fiberglass or carbon fiber, any of the differences will be shown in the worked example.
01:03	With that out of the way, the first step is to get ready for our practical work.
01:07	This includes our tools and consumables, our workspace and PPE, as well as the materials we'll be using in the construction, like the gel coat, resin and reinforcement.
01:17	This might seem trivial, but it's very important to ensure that we have everything we need on hand, as we don't want to get part of the way through it and run into a roadblock.
01:27	Don't just make sure that you have the product on hand, but also that the chemicals like gel coats and resins aren't outside their shelf lives, which is often only about six months.
01:37	I'm speaking from experience here, during the filming of this course we opened a tooling gel coat we planned on using to find a solidified mess in the tin.
01:46	It's an easy mistake to make and a big waste of time sourcing another batch.
01:50	If we're going to be doing a lot of composite work, it's worth keeping a spreadsheet or at least a list with the quantities of the materials we have, as well as the dates we should be using them by.
02:00	We'll cover off the tools as we use them, but for now let's discuss the materials we'll be using for this project.
02:06	We'll start by preparing the mold with release agents.
02:09	When making the mold, we use release wax and PVA parting film on the pattern surface.
02:14	While this is also a suitable way of making our parts from the mold, we'll use a slightly different approach to show an alternative.
02:22	Specifically we'll be using a semi-permanent chemical release agent called Chemlease 4190 Easy to prep our mold for multiple releases.
02:31	Before this is used, the mold needs to be cleaned and a mold sealer needs to be applied to new or porous molds.
02:37	So, we'll be using a product from the same supplier and family of products called Chemlease 15 Sealer Easy.
02:44	After the semi-perm release agent is applied, we'll use the same plasticine that we use for the pattern and mold making stages to fill a few small details of our mold surface.
02:55	We'll also back up the chemical release agent with some coats of the same Meguiars Miracle Gloss mold release wax.
03:02	This isn't technically required, but we've got it on hand and a few coats never hurts to ensure an easy release.
03:08	The process of applying release agents will all be shown in detail in the next module.
03:13	After this we'll have another module dedicated to applying gel coat.
03:17	Not all composite construction projects need a gel coat, but for a body panel like this it's nice to have a durable surface with some material that we can polish up.
03:26	We'll be using Neo Pro Marine Clear gel coat that's compatible with the polyester resin that we'll be laminating with.
03:33	But we'll discuss this soon.
03:35	First it's worth mentioning that clear gel coat, while often used for carbon fiber parts to show off the weave, isn't typically used for CSM fiberglass parts.
03:45	These will usually have a white or gray opaque gel coat to hide the CSM.
03:49	The process is no different, but for the purpose of this course we'll simply use a clear gel coat so we can see the laminate and any possible voids, or hopefully the absence of any voids.
04:01	This specific gel coat is designed to be sprayed on, which would usually be our choice for efficiency and to achieve an even coating.
04:08	But we'll brush it on in this case to show the most accessible approach.
04:12	It'll probably be runnier than we'd like, but we'll manage.
04:15	This will be catalyzed with MEKP, as will our laminating resin, for which we'll be using an isopolyester laminating waxed resin.
04:24	As we'll be laminating in one stage and this will allow a nice hard surface cure.
04:29	We'll also use a resin bulg or filler based on the same resin and thickened with cabosyl.
04:34	As previously discussed, some consider this controversial, but we've covered why, so check back into the mould making lamination stage if you're hazy on the details.
04:44	Again, while some will argue that if your laminating is good enough you won't need filler, this is a fundamentals course and while we're not all beginners, many of us will be new to these practical skills.
04:55	A small amount of filler in our relatively basic fenders is much better than the voids we'd likely get laminating parts with details like these.
05:04	With that out of the way, let's discuss the final form of material we'll be using, our reinforcement.
05:09	There are a few things to consider in choosing our reinforcement.
05:13	The mould surface on the mounting flange is the top side of the part, not the surface that's in contact with the car.
05:20	So, the thicker the laminate gets, the more this shifts the mould surface from the mounting surface, essentially shifting the main body of the fender relative to its mounts, leading to poor fitment of the body panel.
05:33	The thickness of the laminate needs to roughly match the thickness of the original part, so we can be sure the fitment and panel gaps of the composite panel will be reasonable.
05:42	The geometry of the part has a large impact on the strength and stiffness, but past this it mostly comes down to the reinforcement used.
05:50	Since we're limiting ourselves to mostly chopstrand matte for this project, it's as simple as what weight matte we use, and how many layers of it we use.
05:59	Typically the first layout will be somewhat of a trial, and if it's too flimsy we'll add more next time, or if it feels overkill we can always take some out.
06:08	But we can still get in the ballpark by making some educated guesses.
06:12	For fibreglass body panels using e-glass, we can generally match the thickness of an equivalent aluminium panel.
06:18	The factory fenders are just under one millimetre thick steel, so to account for the strength and stiffness difference to aluminium and fibreglass, we'll aim for between two and four millimetres.
06:30	Because our fender has a large arch and flanges, these will help with the stiffness, so we'll start at the lower end of this.
06:36	We'll be using the same 225 and 450 gsm chopstrand matte that we use to make our mould.
06:42	The lighter matte is used for the first layer to conform to the details and ensure we have reinforcement as close to the surface as possible, and the heavier matte can then be used to back this up for the bulk of the structure.
06:54	A lighter matte on the first layers also helps reduce print through from the reinforcement on the surface of the part.
07:01	Recalling from our mould making section of the course, 225 gsm matte is around 0.4 millimetres thick and 450 gsm is around 0.7 millimetres thick.
07:13	So, we'll be aiming for about two layers of 225 gsm and three of 450 gsm, bringing us to a total of just under three millimetres of thickness.
07:23	Again, we need to make sure we have enough of each matte on hand to cover the area of our parts in one laminating stage.
07:30	It's fair to say each fender is less than half a square metre in area, so two metres of 225 and four metres of 450 will be more than enough.
07:39	To prepare the reinforcement we can cut and tear some sections, the cut edges for positioning into sharp corners and the torn edges to overlap, just like our mould making process, but it's always easy to cut more as we go.
07:53	Since we don't want our mounting flanges to be three millimetres thick, as this would cause panel misalignment issues, we'll use a slightly different approach for these areas, using some 200 gsm plain weave, also commonly known as six ounce boat cloth.
08:08	This is more expensive than csm but will be able to achieve similar strength with a lower thickness.
08:14	At only 0.25 millimetres thick per layer, we'll use two layers of this and one layer of 225 csm to be just under one millimetre's thickness like the original panel.
08:26	The woven fabric will also conform to the details better when laying up the reinforcement and if cut and laid up at 45 degrees we'll be able to achieve good strength through the corner of the flange.
08:37	That covers all the materials we'll be needing for this project, so let's summarise what we've looked at before we get started working.
08:44	Preparation is foundational to the success of any composites project.
08:48	We need to make sure we've got everything we need on hand and a plan in place before we dive in, especially with the time limits imposed by the pot life of our resin when hand laminating.
08:59	Our process will start by applying a mould sealer, followed by multiple coats of a semi -perm release agent.
09:06	We'll then use plasticine to fill in some details and a few coats of mould release wax for good measure.
09:12	After the gel coat is applied and cured, we're ready to start laminating.
09:16	A resin bog thickened with cabosil will be painted around detailed areas first to prevent any void.
09:22	This will be based on the iso-polyester laminating resin, which in this case is waxed, as we're to be laminating in a single stage and want a nice hard surface cure.
09:31	The layers of reinforcement will include 225 gsm and 450 gsm trop strand matte, as well as some 200 gsm plain weave.
09:40	These have been selected based on considerations of laminate strength, stiffness and ensuring the panel will fit the car properly.