Motorsport Composite Fundamentals: Kevlar & Aramid Fibers
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Kevlar & Aramid Fibers
03.53
| 00:00 | Kevlar or other aramid fiber composites are somewhat less understood than fiberglass and carbon fiber, likely because they're less commonly used in motorsport, but with that said the properties are still well suited to certain applications in racing. |
| 00:15 | Kevlar is a type of aramid fiber developed in the 1960s by DuPont and is probably the most well known but not the only aramid fiber used in high performance composites. |
| 00:27 | Aramid is short for aromatic polyamide and is a class of synthetic fibers. |
| 00:32 | For clarity, synthetic in very basic terms means that they're made by humans. |
| 00:37 | Similar materials are Tuaron, Nomex and Technora. |
| 00:41 | Some have very similar properties while others are quite different. |
| 00:45 | Kevlar will be the focus in this course though. |
| 00:47 | Like carbon fibers, aramids involve long chains of molecules bonded together and the result is a highly resistant and strong fiber which can be used in a resin matrix to construct a composite. |
| 00:59 | The reinforcement is most commonly available in woven cloth, although it's also possible to get yarns or rovings and braids as well as prepreg, but this is relatively rare. |
| 01:10 | An epoxy resin is best used for aramids to ensure a good bond between the reinforcement and the matrix but we'll come back to this later in the course. |
| 01:19 | Like carbon, these composites have a great strength to weight ratio and amazing corrosion and temperature resistance, essentially being flame resistant. |
| 01:27 | It isn't as stiff as carbon fiber though which tends to make it prone to micro buckling and compression where the reinforcement will quickly bow under load. |
| 01:36 | For this reason in motorsport we mostly see the use of carbon kevlar weaves where the two reinforcement fibers are woven together to combine the high strength and stiffness of carbon with the qualities of kevlar. |
| 01:49 | These distinguishing properties are its very high toughness, giving it great impact and abrasion resistance. |
| 01:56 | With this in mind, it's easy to see why kevlar is commonly used on the underside of race cars, particularly in flat floors in the wheel wells of rally cars that are exposed to extremely abrasive conditions. |
| 02:08 | They're also great for body panels on vehicles that are likely going to be in contact with others, like on drift cars for example. |
| 02:16 | These panels can take an impact and just flex out of the way without being damaged, while still being an extremely lightweight solution. |
| 02:23 | Carbon kevlar composites are also used for race seat shells as the toughness offered by kevlar provides an extra level of safety over a pure carbon fiber shell. |
| 02:34 | The monocoque or survival cell in a Formula One car uses a layer of kevlar reinforcement for the same reason. |
| 02:41 | For stress critical applications, it's ideal to limit the use of kevlar to surfaces that'll be in tension only. |
| 02:48 | For example, if we expect something to flex in a certain direction, then we should use kevlar on the convex side of the part that will be in tension. |
| 02:56 | Whether this is possible or not will depend on the application because we still want kevlar on the impact surface, which is commonly loaded in compression. |
| 03:05 | So, it's really just something to keep in mind. |
| 03:08 | As you'd imagine though, this all comes with a price tag, generally a small amount more than the equivalent carbon fiber weave. |
| 03:15 | The key things to remember about kevlar is that it's a type of aramid, which, similar to carbon fiber, involves longer chains of molecules bonded together to create the fibers. |
| 03:25 | It's often woven with carbon fiber to combine its impact and abrasion resistance with carbon fiber's strength and stiffness. |
| 03:33 | The result is a very durable but lightweight composite that's generally more flexible than carbon fiber, but also more tough. |
| 03:40 | Because of this, carbon kevlar composites lend themselves to highly abrasive conditions or parts subject to impact or where safety is a concern. |
