Motorsport Composite Fundamentals: Cutting Reinforcements & Core Materials

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Cutting Reinforcements & Core Materials

05.13

00:00	As we know, composite construction involves two main ingredients, the resin and the reinforcement.
00:06	In the previous module we covered the tools involved around the preparation of our resin, more specifically measuring and mixing.
00:14	So, in this module we'll look at the tools needed to prepare our reinforcement.
00:18	This discussion will extend to core materials as well, as this can be considered a form of reinforcement.
00:24	We won't however be talking about cutting cured parts here, we'll leave that to later.
00:29	For now let's look at the usual tools used for cutting reinforcements, shears, scissors and snips.
00:35	You might be wondering what the difference between them is, so let's clarify that first.
00:40	To be honest there's a lot of small technicalities that just aren't important for our practical use.
00:46	The key difference we need to understand is the length and the impact this has on how they cut, or rather how easily they cut thick material.
00:55	Shears generally have the largest blades, making them the go-to for efficiently cutting long lengths of heavy reinforcement, including prepreq.
01:04	Compared to shears, scissors are smaller and typically more useful for making detailed cuts, like more complex outlines in the reinforcement for example.
01:13	They can however have longer handles that provide good leverage for cutting heavy or multiple layers of reinforcement.
01:20	Snips are smaller again and are often spring loaded.
01:23	These are designed for small neat cuts like around sharp corners or folds in the fabric called darts.
01:30	Due to their compact size, they're easy to maneuver so they're well suited to making cuts when the reinforcement has already been laid into the molt.
01:37	What's important for all these cutting tools is that they remain as sharp as possible to provide the best results.
01:43	While sharpening them is outside the scope of this course, we'll touch on how to keep them in good condition in just a moment.
01:50	There are a few key considerations here that might not necessarily be obvious past what we've just mentioned though.
01:56	One of these is that carbon fiber is extremely abrasive and while it might not necessarily be difficult to cut, it will cause the blade to dull faster than cutting most other materials.
02:07	Kevlar on the other hand is very difficult to cut with normal shears or scissors, to the point where it can almost seem uncuttable.
02:14	This type of work can require shears designed specifically for composite work, which have specific angles of the blades and serrations that are tailored to cutting carbon fiber or kevlar.
02:25	Kevlar shears will typically have a flatter pitch on the grind which puts more pressure on the material as it shears, helping it cut easier and preventing slipping and pulling of the fabric.
02:36	However, this makes them more susceptible to blunting when used to cut abrasive carbon fiber, so it's best to use these shears solely for cutting aramids.
02:45	Quality shears and scissors are likely to be coated in PTFE, also known as Teflon, to help them stay sharp for longer and provide a non -stick surface so it's easy to clean off any resin.
02:58	Some shears might only have serrations on the upper blade rather than the lower to prevent snagging when they're slid under the fabric.
03:05	While in an ideal world it would be nice to have all the options in a workshop, if you're on a budget then investing in a good quality pair of shears should be high on your list to cover all the bases when it comes to cutting.
03:17	Before wrapping up let's briefly discuss a few other options for cutting other materials, like foam core for example.
03:23	Thinner core material can be cut with shears or a sharp blade, we just need to be careful of what we're cutting on.
03:30	A hobby cutting board or a mat is a good option for a base.
03:34	Thicker foam can be cut in various ways.
03:37	Longer blades can work well, typically something with serrations makes this process much easier.
03:42	Likewise, a hacksaw can be an effective option.
03:45	A hot wire cutter is a go-to for cutting styrofoam especially if we find ourselves needing a little more control.
03:52	As you've probably guessed these feature a thin wire that's heated by an electrical circuit so it essentially mounts its way through the foam resulting in a nice clean cut.
04:02	These can be bench mounted so we can work with both hands on the material we're cutting or handheld for more control which is particularly useful for profiling core material for aero parts.
04:13	The final type of core material we need to cut is honeycomb structures.
04:17	For aluminium or nomex materials the go-to here is a sharp blade like a stanley knife that's long enough to pass through the thickness of the structure.
04:26	We can also make use of a metal ruler to guide the blade because as you probably imagine cutting through the honeycomb structure can make it challenging to hold a straight line.
04:35	In summary when cutting reinforcement fabrics and thinner core materials we use shears, scissors or snips.
04:42	Shears offer the most efficiency when cutting long lengths where scissors and especially snips are more agile for detailed cutting.
04:49	Shears designed specifically for cutting kevlar are best used solely for that purpose as they'll dull quickly from cutting abrasive materials like carbon fiber.
04:58	Thicker foams can be cut with long serrated blades or hot wire cutters for the likes of styrofoam and we'll typically use something like a stanley knife with a metal ruler for honeycomb structures.