TechStuff Classic: How Carbon Fiber Works

it was the history of carbon fiber. Now we're going to get into more about what makes carbon fiber special. Hope you enjoy. Let's start really quick with a with a brief overview of what carbon fiber is um. It's it's made up of thin strands of crystalline carbon um, like like a really thin like human hair or thinner, that have been twisted into yarn type stuff and then woven into cloth type stuff and then usually treated with some kind of resin and molded into a final shape,

right which it will then hold. So it's not you know, it's not like you put it in a shape and then like regular cloth that then loses that shape. You Actually that resin helps it hold that that particular shape. So that you end up with a really strong, really light material, right, And I forgot one step at the beginning there, which is you have to create a this.

You have to create this carbonized material, right, This crystalline carbon strand um, which you do with stuff called a precursor, which can be made with it is most commonly made with ryan polyocryllum nitrial a K A PAN, which we're probably going to use more often than polyocrylla nitrial certainly I will um or petroleum pitch yep. So these precursor fibers, with the exception of petroleum pitch, this is all stuff that we are making synthetically. Uh, you know, we're creating polymers.

Polymers are our long chain molecules. They're made up of monomers. A monomer think of that as like a basic unit of a polymer. So you get these really long chains and then we carbonize them. So how do we carbonize Well, for one thing, we use chemicals to alter the molecules in the fiber to create a perfect chain of carbon atoms. And these precursor fibers are pulled through an oxidation oven for a couple of minutes, and that oven's temperature is

about two hundred fifty degrees celsius. So the fibers then take on oxygen atoms from the air while in the this oven. Now this is not the actual carbonization process here. This is just pre treatment, kind of like when you take your car in to get car washed, and this is the pre wash part of the wash. We should probably do an episode about car washes at some point and find out which one which of those stages are

actually necessary. But getting back to the carbon fiber, the incorporation of oxygen atoms into the molecular structure of the fibers make the fibers actually resistant to high heat. It's very import because of an upcoming step. Now. At that time, the color of these precursor fibers changes as it oxidizes and eventually turns black. So whenever you hear something like

carbon black, and yeah, it's that particular color. Like I remember this all the time in video games where you're choosing your like halo, particularly where you're choosing your armor colors, it's because it's taking it from the carbon fiber color and the color tends to be black because that's what

happens through the oxidation phase. So next you put these oxidized fibers, the ones that have been tempered for high heat to go into another furnace, and this one has controlled amounts of other gases, but not oxygen, because you don't want the fibers to burn, right, because in the presence of oxygen, those fibers become fuel and then you just get fire, right, and then an ash is less strong. Yeah. Yeah, if you just burn up your material, you are not

doing it right. So what you have to do is you have to have these other gases that can enter deuce other types of atoms into the molecular structure, for instance hydrogen perhaps, but non oxygen, so that way you don't actually have a fire, you don't end up burning the stuff, right. So, so with this tremendous heat, the the fibers vibrate and the atoms that are not carbon vibrate right out of this stuff, resulting in this carbonized

material exactly. So we get these carbon atoms and they are becoming these tightly packed crystals that run parallel to the length of the fiber. The fibers then go through a bath of electrically charged water which etches the surface of the fibers. It actually carves into the surface of the fiber a little bit, and those etched surfaces create anchor points for resin. Yeah, because otherwise, you know, the resin wouldn't necessarily adhere evenly to the carbon fiber, making

it less useful. This is a way of sort of giving those little hand holds. I think of it like a rock wall with the little handholds in them, similar to that. So net you have to spray the fibers with a light resin. Now that that is important for two reasons. It helps improve the fiber's material strength, and it creates a bonding agent for any future resin that would be applied to that carbon fiber. So this is not the stuff that makes carbon fiber uh adhere to

a specific shape. It's not multiple right. This is just so that if you exactly if you want to apply multiple resin to it, that resin will adhere better. So everything here is all about pre treating this stuff so that it can eventually be put through whatever manufacturing process you want to continue down the road in order to get at whatever you're making, for example, a golf club, um or an airplane. Who knows you could do either

with these sort of stuff. So then you have the finished carbon fiber, which is called a carbon fiber toe, and you wind that on a spool. So this is the stuff that other companies buy as raw material, which then they can braid, eve mold, or otherwise altered to make into their final product. Now, carbon fiber toes can also be grouped together in larger amounts called a web. Now, these webs can be put through a process that ends with a sheet of carbon fiber material. It's kind of cool.

It looks like just an enormous black sheet of fabric, but that fabric is actually carbon fiber. So that fabric is five times stronger than steel and lighter than steel, and more more, it can be stiffer than steel if you apply the resin to it. I mean, it's it's interesting to think that something that looks like cloth could have these properties. Now, see the web is sandwich between sheets of paper to have a resin coating on them. Sounds familiar, right, got a lot of resin in this process.

But these sheets are pulled through a high temperature pair of rollers. So think of the ringers we talked about with the washing machines, same sort of thing. You're putting this whole thing. Those those rollers are are at a high temperature. They're pressed together really tightly. And what this does is you get this protective layer over that that carbon fiber sheet, and then you remove the two pieces

of paper. They just peel away because part of the material in there is kind of like a nose stick coating, sort of like teflon. And so you pull the paper away and you roll the the carbon fiber material, like the big sheet of material onto giant, giant spools. You do have to put a little polyvinyl coating on them

so that way it's actually like to itself exactly. But they look like, and I am not the only one to have used this comparison enormous fruit roll ups, and like enormous fruit roll ups, they have that little plastic coating to keep it from sticking to it or fruit leather if you prefer, let's proprietarily yeah, um, but but yeah, that that that resin job there reminds me a lot of if you, as a child ever made ever preserved leaves or flowers and wax paper by by ironing it

down so that so that you've got that thin layer of wax similar to similar, very similar. So now this entire process, Uh, does have some downsides to it. Not the flower pressing thing. No, no, no, no, carbon fiber if you're not careful, the flower pressing thing too. But no, I'm specifically talking about creating carbon fiber and not just the carbon fiber sheets. I'm just talking about the whole

process of carbon fiber in general. One of those is that it tends to give off a lot of dangerous gases, including carbon monoxide. So the smokes and tars that are given off in this process are not necessarily poisonous, but

can contribute to serious health issues with prolonged exposure. So one of the things that's really important in the facilities that make carbon fibers is that they have really good ventilation so that the people who work inside them don't get sick over time, sure, and really good collections so that you're not polluting the environment. Yeah, So this is a process that could potentially be harmful to the environment

just through the production process. Now, we talked in the last podcast about how the fact that it's lighter and stronger than steel means that using it for vehicles means you use less fuel for that vehicle, which efficient. Yeah, and it makes it environmentally friendly from a fuel consumption process. But like all things, you have to look at the

enormous picture, which you know. It's one of those things where every time I start getting really excited about technology, thinking oh, clean energy, and then I start looking beyond about how do you make the clean energy? And then I think, yeah, there needs to be a magic button. That's all I'm saying. But anyway, you you classify this stuff according to the tent sile modulus of the fiber tent file modulus. It's a measure of how stiff the fiber is. Yeah, but that's that's the term within the

industry is tensile modulus. And I bet because because of the way the world works, there is both an English system and an international system for dealing with this. Yeah, you are absolutely correct. So the English them would be pounds of force per square inch of cross sectional area also known as p S I PI, and then the international system of units would be the PASCAL, which is also known as force per unit area. So one pascal is one newton of force per square meter, meaning that

it is interesting to try and convert between the two. Fortunately, the the various sources we looked at spelled it all out for us, so we didn't have to see, we didn't have to do Yeah, we didn't have to worry about being the ones who messed up a conversion. So if these conversions are just let Google do that for me. Not the Google usually messes up conversion. If I mess up a conversion, it's because I accidentally didn't realize I put the wrong unit in on one side of the conversion.

Uh So fortunately this case, we didn't have to worry about that. So low modulus carbon fiber have a tensile modulus below thirty four point eight million p s i or two hundred forty million k p a that's kilo pascals. And on the other end of the spectrum is the ultra high modulus. There's a tensile modulus of seventy two point five to one forty five million p s i or five hundred million to one billion kilo pascals. Now, in between those two extremes are levels like standard modulus,

intermediate modulus, and high modulus. And if you wanted to compare it to steel, yeah, yeah, so for you know, for baseline comparison, right, because often that's what we like to look at right, carbon fiber versus steel. I mean, otherwise why use carbon fiber at all if steel were better. So steel has a tensile modulus of around twenty nine million p s i or two hundred million kilo pascals,

so close, but but not even reaching the low modulus. Yeah. Yeah, the low modulus was thirty four point eight million p s i or two d forty million kilo pascals. So that means that if you go with the strongest carbon fibers, you get ten times the strength of steel, right, the tin style modulus if you want to be really picky, but yes, strength is how we usually call it. So steel is five times heavier than carbon fiber, and carbon fibers ten times stronger than steel. Yeah, if you're using

the ultra high version. So that's pretty cool, and that is I mean again one of the big reasons why everyone is is really excited by this this particular type of material. Oh absolutely, but but okay, So aside from those pollution related drawbacks that we mentioned earlier, there are unfortunately some others with this material. We touched on them briefly in the previous episode, but let's go a little bit further into them. However, before we do so, let

us take a quick break to thank our sponsor. I like saving the negative stuff for after the sponsor break. Let's talk about some drawbacks. All right. So we mentioned earlier in our first episode in fact, that carbon fiber is expensive, and we mean really expensive. It's like ten dollars a pound on the low end, whereas steel is something like a dollar per pound. Now we should say

this is an improvement from twenty years ago. In right, carbon fiber back then cost a hundred and fifty bucks a pound, So the prices dropped precipitously, one might say, since the nineties, still more expensive than steel. Yeah, and and the price is because of that really intricate manufacturing process that we've just talked through. Um, the raw materials are more like four dollars per pound, which, to be fair, is still four times what steel costs. Yeah, I mean,

you're you. And that's just to make those raw materials I mean, or by those raw materials before you put them through the carbon fiber process. So what exactly is making the process expensive? Okay? First off, those furnaces, uh, not the original furnaces, but the carbonization, right, they run around or even an excess of a thousand degrees celsius, which is over eighteen hundred degrees fahrenheit, meaning you've got a really big power bill. I always worry if I've

let the oven on. Yeah, the process uses some five times more energy than steel production. Okay. Also, venting the waste materials safely is expensive. We talked about how carbon monoxide is one of the big things that's led out in this process, right right, Um, and weaving the stuff for maximum safety is expensive. You have to use a lot of fibers to compensate for for potential imperfections in the weave that could cause strain and eventual breakage within

the fabric. Um. Also, it takes longer to create a piece than it does to just stamp out a piece of steel. You know. It's it's this huge three part process. Um. It takes an hour to cure the resin alone. So we're talking we're talking about bunches of time. Okay, But all right, I see here you actually looked more into the reson itself. I'm really interested in this process, right Okay. So if you make it with the most common resin,

which is thermos set resin, it's in that shape forever. UM. It's it's really difficult to reef or melt down or recycle thermo set resin carbon fiber. UM. If you do try to recycle this stuff, that the resulting carbon fiber is weaker, it's too weak to be used, for example, in a car body for for safety standards. So there's greater potential for waste in both manufacturing and the post

consumer market. I mean, if if you set this thing wrong, it's I mean you've basically just wasted this huge, expensive process. So if your molds are off even by a little bit, then you're you're stuck with the shape that you've got, and you can't easily break it down and just make a new one because it's going to be less strong. It'll be too weak to really possibly depending upon what

the application was. Yeah. Yeah, so that that's a big draw. Yeah. UM. There are some possible solutions to this that the industry is looking into other than the manufacturing streamlining that Jonathan was talking about earlier. UM, and those are using strong acrylics in place of carbon fibers, or perhaps in combination with carbon fibers. UM. They're experimenting with heating the stuff with plasma instead of the thermal furnaces that are currently

in use. You know, I love plasma furnaces. They're pretty they're pretty cool. Not literally length about plasma furnaces, so um or or possibly using re multiple thermoplastic resins in place of the permanent thermoset resins that are currently in use. Now that's interesting. Now, obviously with that particular approach, you would have to make sure whatever application you are using, uh the carbon fiber for wasn't going to bring it

into contact with temperatures too high. So obviously, like exactly that would be. That would be one where I think the permanent thermo set would definitely be the way to go because they undergo such extremes and temperature that anything that could potentially weaken the the structure would be a

big negative for that particular application. Sure, one more downside before we get onto happier news though, Um, the a lot of the precursor materials are petroleum based and so you know which which obviously, petroleum is an expensive and non renewable resource unless you've got a few billion years to play with. Yeah, if you don't mind you know, stretching out your lifespan too. Beyond what is conceivable, then you're fine. But otherwise you could reach a point where

in years we're gonna have the singularities. That's true, that's true. So I guess millions of years. I guess it's really millions, not billions of years. I apologize, guys, hundreds of millions of years. So it's fine. I was overstating things exaggeration in order to make a point. But but so researchers are looking into renewable precursors like lignant, which is a

would by product that would be really useful. So it's kind of funny too, because in a way, it's look back to the earliest days of carbon fibers where we were using cotton and bamboo to create carbon fiber. Time for another quick break, and we'll be right back. Now. Let's talk about some of the other benefits when when you treat this carbon fiber with the right resin ends up being resistant to corrosives, which makes it an ideal material for pipes that tend to carry corrosive liquids, and

their fatigue properties are better than any metal. So by having these pipes, you don't have to worry about them wearing out a quickly. They're not going to corrode based upon whatever materials moving through them, and they are themselves in nerts, so you don't have to worry about chemical reactions going on in there. So that would be one of the big benefits if we were able to make enough of it to be used in that kind of infrastructure. Sure. Also,

that strength really is impressive. Formula one race cars are made all of carbon fiber. Well, I guess not all of carbon fiber. I mean, you know they've got pieces, right, but the body is uh, and that's more as a safety regulation than anything else. So so if we could bring down the cost of the manufacturer, it could potentially save lives. Sure yeah, yeah, you know, you end up making even basic car designs much stronger just by switching

the materials they're made out of. And then, uh, something kind of cool that I read before we started, uh really getting into this podcast. It was just a neat little little news item, and uh, I encourage folks are interested to go and look up the Mark one three D printer. It's built as the world's first three D

printer designed to print continuous carbon fiber. So it uses a process called composite filament fabrication or CFF, which embeds continuous strands of fibers in a thermoplastic matrix, So you could actually print carbon fiber pieces like you could print various components in carbon fiber, right with that thermoplastic that I was talking about being being remultiple and remultiple, And so you might be thinking, hey, how much would one

of these things run me? So if you want to pre order one of these, because they don't they haven't been out on the market yet, you can pre order one. Uh the cost is a lowly four thousand nine dollars, which you know, printers really isn't that expensive. I mean, if you're looking at at three D printers that are printing in UH an a BS plastic, which is typically what other three D printers use, those tend to be

less expensive, but ABS plastic is not as strong. In fact, the print of material materials are supposed to be up to twenty times stiffer and five times stronger than a BS plastic parts. So if you are building things that have a lot of wear to them over time, this could be a good solution because it means you don't have to print replacements as frequently. Sure, although I mean I imagine that the cash to purchase the materials to

put into your printer. Yeah, it might be more expensive to get the actual like quote unquote the toner than a BS, So that is something else to take into consideration. But yeah, so this material has has a huge amount of current use and future promise. Yeah. In fact, I remember some people even going so far as to look into the use of carbon fibers as a potential tether material for space elevator. But as it turns out when you do the math, it looks like, uh, carbon fibers

wouldn't be strong enough. It wouldn't have the tin stile strength to withstand the forces. Yeah, because it's not quite as strong as carbon nanotubes. I mean, the problem with carbon nano tubes being there that you know, you can't get them as long as you can carbon. Yeah, producing

carbon nanotubes is a big problem right now. Like, while we're getting closer and closer to to really efficient means of making carbon fiber more plentiful due to the manufacturing process improvements over time, we're a long way with carbon nanotubes. I mean, we've seen some promising develop elements, but you know it's still gonna be a while. I hope you enjoyed that classic episode of tech Stuff. We're going to uh take another look at carbon fiber soon. I think

I was considering it earlier. I think I'm pretty firm on that. If you have suggestions for things I should tackle in future episodes of tech Stuff, reach out to me. The best way to do that is over on Twitter. The handle for the show is text Stuff H s W and I'll talk to you again really soon. Text Stuff is an I Heart Radio production. For more podcasts from my Heart Radio, visit the i Heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows