Motorsport Composite Fundamentals: Fiber Glass
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Fiber Glass
05.26
| 00:00 | The first motorsport composite we'll discuss is fiberglass, which is perhaps the most accessible due to its relatively low expense. |
| 00:08 | Fiberglass often gets a bit of a bad rap, but it's mostly unwarranted and simply a result of it being a cheaper option, which tends to mean less care is taken in the quality of the construction. |
| 00:20 | Before we get into why, we first need to understand what fiberglass really is. |
| 00:24 | In basic terms, the glass fiber filaments are made by melting minerals like silica sand into a liquid form and extruding them into long, thin lengths with constant cross section. |
| 00:35 | Depending on the designation of the glass, these are around 10 to 20 microns thick, and for reference human hairs are around 80 microns in diameter. |
| 00:45 | The solidified glass filaments are then collected into strands and bundled together into what's called rovings. |
| 00:51 | From here they can be used directly for manufacturing by gun roving, which is where an automated gun chops the fibers into short lengths while mixing it with a jet of resin and spraying it into a mold. |
| 01:03 | Alternatively and more relevant to our applications, the fibers are arranged into a woven or unidirectional fabric, or for a less uniform approach, they can be also made into chop strand mat or CSM, which is randomly oriented small cut lengths of fiber bonded together. |
| 01:20 | With either the woven or non-woven fabrics, these can be laid up in a mold and combined with resin to create the composite or FRP, the processes of which we'll be covering later in the course. |
| 01:32 | Glass reinforced polymers are also common in injection molded plastic parts to increase the strength and stiffness. |
| 01:38 | However, this isn't the focus of this course, it's a totally needed, it's much more industrial equipment, typically designed for mass production, and this means it's generally extremely expensive and not particularly accessible. |
| 01:51 | Moving on, let's discuss the properties of fiberglass, and naturally it makes sense to compare them to those of other materials and composites, which we'll be discussing more in the following modules. |
| 02:02 | It's important to understand that every property we discuss is typically as a ratio, so for example strength to weight or stiffness to weight. |
| 02:11 | So, the advantage of each really comes down to how these properties are considered in the design of the parts. |
| 02:17 | In other words, if material A has a better strength to weight ratio than material B, the part could either be lighter for the same strength or stronger for the same weight. |
| 02:27 | But if the part hasn't been designed well, then this might not be the case. |
| 02:31 | So, when comparing materials, we always assume that all things are equal. |
| 02:36 | There are many different grades of fiberglass, but the two key ones of interest to us are E -glass and S-glass. |
| 02:42 | E-glass, where the E stands for electrical grade, was originally developed for wire insulation, but later found to have good reinforcing strength when coupled with resin. |
| 02:52 | This is by far the most commonly used and it's also the cheaper option that's a lot easier to get hold of. |
| 02:59 | S-glass on the other hand was originally designed for military and ballistic applications and as such is around 30 percent stronger and 10 percent stiffer than E-glass, although very similar in density. |
| 03:11 | The manufacturing process requires higher temperatures and specialist machinery, so it's naturally significantly more expensive. |
| 03:18 | Comparing the strength to other reinforcing fibers like carbon and kevlar starts to get a bit messy as there are so many different grades of each. |
| 03:27 | In some cases the strength per unit area of fiberglass can actually be higher than that of carbon or kevlar, both of which we'll discuss in more detail in the following modules. |
| 03:38 | With that said, in general fiberglass is considered to have significantly lower tensile strength than carbon for the same weight. |
| 03:45 | The key difference really lies in the strength to weight ratio as fiberglass is about half that of carbon fiber, meaning a carbon fiber part with equal strength can be around half the weight of the equivalent fiberglass part. |
| 03:59 | Fiberglass is a lot less stiff than carbon fiber but this isn't always a negative thing, it just means that it's suited to different applications. |
| 04:07 | Fiberglass is a great choice for composites that need to flex but where strength isn't the primary concern. |
| 04:13 | It's considered tougher than carbon fiber so it's better for parts that need to withstand physical abuse from impact and is significantly cheaper to repair and replace. |
| 04:23 | Body panels on the likes of drift cars are a good example, they aren't structural but they'll probably be the first part to take a hit. |
| 04:30 | But if stiffness is a primary concern like aero or suspension components, then the weight will have to increase to gain this back and in some cases the increase in weight to recover the strength wouldn't be justified though, like for suspension components where adding the unsprung weight is especially detrimental. |
| 04:47 | In summary, fiberglass consists of reinforcing glass fibers in a resin matrix. |
| 04:52 | There are many different grades of glass fibers with E-glass being the most widely used and available, while S-glass is more expensive but around 30% stronger and 10% stiffer. |
| 05:03 | Fiberglass is significantly cheaper than carbon fiber but also has a strength to weight ratio of around half. |
| 05:09 | It's also a lot less stiff, meaning it's not as suitable for applications where strength and stiffness are paramount, however its flexibility and toughness can be an advantage in applications where impact is possible. |
