Hi, I very enjoy your videos, but perhaps I have to disagree on this one for many reasons. First, many industries adopt glass/carbon composites in many components. Wind turbine blades are a good example. Second, you don't design to max elongation ever, first because you usually have more constraints on structural failures (like safety factor on strength and buckling) that restrain your design. Therefore, it is doubtful that any part of your structure reaches the elongations that you show in the video under nominal conditions. Third, fibreglass is more resilient to impact, and it can extend your laminate life when something not predicted happens. This means that if there is a crack somewhere, glass fibres will prevent that to spread in the laminate. Finally, since under nominal conditions, the laminate life span is only linked to the time required to micro-cracks (which are there since consolidation) to bridge and become macro-cracks (a.k.a. broken part), we can definitely state that those glass fibres will increase the fatigue capabilities. Each and every good design must consider fatigue, and glass is way better in that than basically any other fibre. Therefore a well designed glass-carbon hybrid aims to find that sweet spot between pure stiffness and long life span, which could correspond to an overall lighter structure. Ultimately, I suggest adding another layer on top of the carbon for a glossy finish. Once wet, it will become crystal clear while protecting the laminate underneath. In other words, I would like to let you notice that if your component has reached the point at which the carbon is broken (like you say in this video), your structure must be considered failed. The fact that you still have some fibres that can carry some load means that if that was your structure, it is now less stiff, but it is still one piece! I am sure that in F1 the safety coefficients might be very close to one and that resilience has a different meaning than for aerospace structural engineers like myself. However, trust me... If that was the hull of your boat in the middle of the ocean, you would have been glorifying and blessing the carbon-glass mix that keeps your boat afloat! You might not be able to cruise at full speed anymore, but you are not on the bottom of the ocean as it would have happened with a carbon hull that cracks in a blink of an eye... Please go and search some interesting peer-reviewed papers on hyperduct... it is an ongoing work on glass-carbon laminate to simulate yielding for highly resilient composites. Cheers,
e glass and finer glass are not for the same purpose ... e glass is used in high bending parts like wings on a jet liner ... while fiber glass and S glass are used for high strength parts like engine nacelles and tail planes ... if he compared E glass to EDR glass and carbon fiber to S glass he would have made one point ... carbon fiber is expensive and s glass is cheaper ... E glass and EDR glass are BOTH flexible edr glass can be made conductive like carbon fiber .. which is why it is used in wings ... while carbon fiber in engine nacelles need strength over flex ... where carbon fiber comes in handy because it is less weight for the same strength as S glass ... and of course Galvanic corrosion will happen with carbon fiber and edr glass so using s glass or e glass as a boundary layer between metal and the conductive fibers is mandatory to avoid that ... but then you also make a capacitor and need to channel the charge off the fiber ...
In the example he gives, the carbon would likely weaken the structure. The surface crack would cause a stress concentration in the underlying layers. (Always a consideration if you have layers of material; e.g. chrome plating suspension parts is a bad idea unless there's lots of something ductile like copper underneath to smooth out the cracks from the surface.)
It is not related with Chrome plating here, plating is chemical process which is not physical/mechanical related topic. But in general, Chrome plating weakens most of the metal materials because of acidic process damages the surface finishing of the part, causes micro cracks in surface weakens fatigue strengths of part.
he is comparing a strength fiber with little flex against a flex fiber with lower strength ... he should have used S glass ... as it is a strength fiber with minimal flex ... and instead of carbon fiber for e glass EDR glass ... as it is also high flex and conductive ... one fiber is not the same as the other ... he is literally comparing a rubber band to an I beam and saying the I beam sucks as a spring ... which is true ... but the rubber band sucks as a support ...
This is correct and incorrect depending on the application. Look at a Mongolian short bow it uses a lamination of substances with different stretch and strength properties to achieve it's goal. So adding a layer of CF may actually be desirable if you wish to alter the flexing of a component in one direction like on a wing.
For an archery bow, I would add the carbon on the belly side, and the fiberglass on the back side, so the fiberglass could elongate more. Or sandwich fiberglass on the outside, with layers of carbon fiber on the inside, since most elongation is on the outside, so you could use both materials for strength.
My use of carbon fiber "beauty" layer for non-loadbearing panels that need the stiffness...hoods, bumper covers, rear deck lids, fenders, etc. allows me to avoid painting those panels and keep cost down by using fiberglass for the core structure. I use S-glass for loadbearing structure and carbon fiber alone for interior panels...dash, door cards, pillar skins, etc. and other parts that need to be lightweight but aren't subjected to high stresses or impacts. Probably not necessary but, so far, no unexpected issues. Thanks for your expertise. I learn a lot from your videos.
Structures break from stress points caused by deformation under load far before reaching the tensile strength of the material. A layer of carbon on the exterior can greatly in crease stiffness helping a structure to maintain its shape. Strength should be in the design more so than the material.
Not completely true if the structure is under significant load due to the difference between carbon and glass fiber. Fiberglass wants to stretch a little bit before it takes a lot of force, carbon fiber on the other hand doesn't really like to stretch at all. So by having an exterior layer of carbon fiber in parallel to the fiberglass under the same load, the carbon fiber will take all the load, while the fiberglass will only take a little bit. This means the carbon fiber will break before the fiberglass takes any significant load, which then transfers all that load to the fiberglass and it will fail too. Comparing that to the same structure made completely out of fiberglass or carbon fiber, it becomes much stronger as all the fibers will be spreading out the load throughout the whole piece instead of just the individual layers.
Another feature is the stress concentration which will occur when the carbon fiber breaks. At that point, the load the carbon fiber was carrying will be taken up by the remaining layers of fiberglass at the break. The result will be similar to nicking a sheet of plastic: once there is a stress concentration, there will be accelerated total failure. Destructive testing will easily show this.
There is a specific case where a combination of carbon fibre and fibre glass in sandwich construction on boats resulted in much greater impact resistance than either material alone however I don't remember where I found the research paper and I don't know how that would translate without the foam middle layer of marine sandwich construction or above water.
A lot of composite parts are stiffness driven and strength is secondary. Eg car body panels if it's stiff enough not to flop around then it's most likely strong enough to survive rocks or whatever debris you normally throw at it. Using fibreglass as the core to build thickness and carbon fibre at the edges is still a valid cheaper way to make composite panels with 90% of the bending stiffness of a homogeneous carbon composite.
well he is only talking about something that will be receiving tensile stress. i don't think a door or a hood is going to see that much... but things like wings and what not definitely would and it would concentrate a lot of force at a single point.... so if across the surface its receiving a 2% tension.... the fiber would break... and now instead of across the whole body the tension is focused at the break.... and that 2% goes up to something like 6%.... well you just snapped your spoiler
If your goal was to build thickness, and not to provide strength, surely you'd go for a lightweight core material? Again, I'm not sure of any case where you'd want to do this for performance reasons. You're not getting the extra strength of the fiberglass until the carbon fiber fails, and once that happens, you're not getting the stiffness of the carbon fiber. If stiffness is critical, you wouldn't want a fiberglass core in your carbon fiber, and if strength is critical, you wouldn't want a carbon fiber skin on your fiberglass.
incorrect. I made parts for FSAE cars out of carbon fibre. and although they were stiff as hell the rocks from the wheels made the edges crack a lot. just because something is stiff doesnt mean it's strong. Maybe watch the video again because it seems you didn't listen or understand what's been said This is the reason why wheel arches on GTE cars are not carbon fibre but rather kevlar and glass composites
And he throws out the exception of chopped strand mat, but doesn't address woven + mat layup. Or foam core, honeycomb, or any other variable layup that is most composites.
A hybrid fabric is designed to work with itself quite nicely. LOL If you're building a critical part you're not using E glass, you're using S Class! Since S glass either meets or exceeds both Kevlar and carbon fiber. Once again you wouldn't make a critical part out E Class. And if you build all your strength first and then want to put a pretty layer of carbon fiber on it, it matters or not, since you're not relying on any strength of the carbon fiber. I have built a few sets of composite landing gear. The heaviest plane having a gross of 1300 pounds. And I have done that with alternating layers of S-Glass and foam. you can't destroy this landing gear. LOL and then to make it look exotic I top it off with the layer of textream and zylon hybrid. It would be nice to build everything out of textream and zilon . But it's 70 - $80 + a yard....
Loads of people have commented on your video with some very good points, the main one that seems to make the most important point is that when the layers of e-glass and carbon fibre are bonded together they become a singular entity. If one portion of the composite fails under any kind of stresses, the other layers withstand it somewhat so as not to have a complete failure. Also remember why carbon fibre is used in the first place, strength to weight ratio and stiffness.
I agree I know this has nothing to do with it. It's just an example for myself to reply and agree with yourself. [ Gold & Siver ] Strength in their own materials. But, adding Silver to Gold or the other way around. One will weaken the other right? Which is heavier? Not sure I would think Gold is or would be heavier than Silver.
Katanas have a flexible core steel, and a more brittle steel hotdog bunned around it for a sharper more durable edge. Infinity CMMD technology is also worth checking out, it uses an aluminum core of 60% sandwiched between 20% alumina(ceramic) on both sides. They do this so that the layers constrain each other as they each have different speeds of sound propagation, the layers dampen each other’s resonant vibrations, and it is also a stiff and light weight combo. Great for speakers.
Laminating Carbon fiber on top of fiberglass(usually S glass not E glass) comes from the aerospace world. When trying to maximize certain characteristics while keeping weight extremely low you can add a layer or two of carbon fiber. The introduction of cheaper Kevlar has made this less used but still a completely viable way to remove flex from “bouncy” items in a racing plane. I’ve saw a few Formula 1 racing planes that use this on the fuselage and wings. They are painted afterwards so look is definitely not the goal.
I used carbon fiber over few fiberglass parts with great success. The secret is to lay couple of layers in different direction and use epoxy rather than polyester. The part was twice stronger than the flimsy original. Especially when is applied on both sides. Also, built couple diffusers with foam and carbon fiber that were very strong...actually couple of racing boats were built with the same materials with incredible strength.
Carbon fiber over foam is a completely different thing, and if you're adding enough carbon fiber to be stronger than the fiberglass, of course that would strengthen it. You're probably confusing stiffness with strength though.
You forgot to mention the load distribution before failure. Based on stiffness and strength the 3 GF to 1 CF, carbon fibre will still carry ~60% of imposed load until failure at 1.4% strain when structure will experience rapid jump of stress on GF from 40% to 100% of imposed load.
Great video. Great advice. There isn't some people that do this, there is alot of people and even most well known aftermarket companies. They combine fiberglass(strand Mat) and fiberglass together. They also put black pigment in the resin so the back side is all black. I understand the cost can be really high but it defeats the purpose of an actual carbon fiber part. I will admit, when I was younger I did by a cf hood that was made like this not knowing. You can also tell by drilling into the part. If its a spoiler and are making mounting points. You will see the white fiberglass shavings come out. They also make dyed black woven mat. About the cracking, I see it all the time on hoods. And alot of people buy carbon mainly for the looks. Im a bit of a sleeper, I paint my cf parts. But thats just me.
I have been trying to figure out how to make 4x4 chassis armor without a welder and plasma cutter. This video and the last one have been very helpful. I would have never considered s glass on my own without seeing the charts.
If you needed a part that required tensile strength, rigidity, puncture resistance, thin lightweight, impact and chemical resistance and abrasive resistance, combining different materials would be necessary right? But as you said wrapping s-glass with carbon fibre looks good however not so great functionally. S-glass over carbon fibre would seem to be a better choice. The s-glass would receive and absorb the initial force and distribute it before hitting the carbon fibre right? This would allow the carbon to act like a bone under softer tissues. If you covered the s-glass with Kevlar the structure would gain abrasive and puncture resistance. That could then be covered by Mylar and gain thermal, chemical, dielectric and impact resistance. I would think it better that the Mylar be between the Kevlar and s-glass but to my knowledge resins will not bond properly to Mylar causing separations in the layers. You can layer the carbon fibre, s-glass then Kevlar sheets then cover it with the Mylar. NASA studies have shown using "Sure Bonder 9001" to secure the Mylar to other surfaces works best. Stack and vacuum form the first three layers, apply adhesive and Mylar to the dried unit and vacuum seal the Mylar. The vacuum forming will help maintain consistency and uniformity in the projects thickness as well as help remove excess resin reducing weight. Just Thinkingoutloud
This talk needs a demonstration of layups on a test rig. When I've seen talk of mixed layups I've normally seen the carbon added for stiffness when a part is already strong enough, with the fiberglass for toughness and cst savings.
Depends on the channel check out engineering explained if you are interested in basically the car equivalent to this (I'm not affiliated just a fan his videos are very interesting)
Carbon over Fiberglass works great for looks... and for some people, aesthetics are far more important than everything else on a daily, not a track car. So... even if is weaken than a real carbon piece, or less lighter... I don't even care about. It is by miles, the cheapest :)
I 100% agree if you're making a structural part, however, if it's mostly a cosmetic or lightly loaded part then it's a cheaper way to simulate the look without any down sides.
1) Amazing timing with the sub accident for this to be recommended 2) Also this is being discussed in the cycling community as companies are putting fiber glass in the forks to prevent galvanic corrosion
What would happen if you alternated the layers of two different materials? Or what if someone made a carbon-glass composite? Also, does resin effect the numbers in any way?
Love the video! What if I went for the reverse configuration (carbon inside, glass outside) to provide strength against bending? The outer layers will elongate more than the inner layers, allowing the glass to take more of the stress. Just curious. Thanks!
Cool. True, some RUclipsrs carbon fiber people (do it for a living) alternate the layers of fiberglass and carbon fiber with cf on top but for me I'd like to make it all out of carbon fiber like Koenigsegg and Pagani. This feels like Jason's Engineering Explained and my automotive + shop high school class. God bless.
seems to me that coating fiberglass in carbon fiber would actually make it worse, because when the carbon fiber breaks, the fiberglass is suddenly taking all the force in a sort of shockwave as it suddenly flexes, plus the carbon fiber is still stabilizing the two sections on either side, creating a weak point where the split is that becomes almost like a hinge, ready to snap it
As opposite to the fiberglass taking the entire force from the source? The initial force already creates a "shockwave". It seems more intuitive that the carbon layer will dissipate some of the initial force from the source, leaving only the remainder of the force to be taken by the fiberglass. Either way, wrapping fiberglass with a layer of CF would negate the purpose of using CF as explained in the video.
no you can make fiberglass backed bows so snapping force isn't a big deal the flexibility and strength is great for it. where as carbon fiber wouldn't work.
I don't want to say this video is pointless, because elongation is actually a point. But there are other things why I will continue doing this. There are many points why it is actually good to combine various mats.
@@seigeengine The video is good and makes a valid point. Your point is also valid. Some of the other properties you may want include increased rigidity, buckling resistance, flutter control, abrasion protection. Each design is different, so I am certain that I am missing some properties.
Awesome video as always kyle. I want to note as well that the microphone quality is absolutely astounding in this video!! The improvements youve been making have been well worth it on that front. Cheers!
Thanks Chris! This was my first video with my new camera, it had better preamps in it which allows me to use my nicer mic. Also has 60fps and 4k capabilities! I still haven't gotten used to the exposure settings on it though, as you can probably tell in the video.
Why do people wrap wood cores in fiberglass then? Wood bends more and is heavier - so what is the point of fiberglass as the outer layer? Boats, wakeboards, skis, snowboards, aircraft (before aluminum), etc, etc.....They all use that type of construction. What do you know that all of those engineers don't? Or is it something they know that you don't?
If it's engrain balsa wood, that's a core. The core is there to prevent the skin from buckling. Wood/mass is also good at absorbing vibration. This video is saying don't skin your wood with glass and then lastly carbon.
E (young's modulus) for wood is about 10 to 15 GPa (depending on grade/species etc). E for fibreglass is 70-80 GPa which gives it much more stiffness in bending applications. It gives the wood strength in cross grain applications. It helps water proof the wood. The design strength of fibre glass is also much higher than soft woods and you get much higher strengths in bending applications.
@@yodaiam1000 - *Thanks for proving my point!* Fiberglass gives rigidity to wood cores, just like carbon fiber would give rigidity to fiberglass cores. As far as your "cross grain" argument - wood cores are layered perpendicular, so there is no "cross grain".
@@ezraboren2069 - Not true. Epoxy, enamel, or some kind of urethane would achieve the waterproofing - there is no need for fiberglass in waterproofing.
what composites are best to make a crash structure, something that can crumple but only in like a car crash? how would you align the fibers' sheets? how much resin? what kind of resin? do we need a controlled environment for resin application on sheets? Is there a composite with even lower density that can allow for more crash structure volume but without compromising strength and integrity of passenger cell?
so fibreglass wrapping a cf piece would be of use if you wanted to increase the parts ability to hold together without cracking without compromising it's stiffness?
Surely it's enhancing stiffness at low deformation (say airflow over a bumper) regardless? By placing it on the face of a bumper it would help it keep shape at speed then by thinning the carbon at bolt holes, force a hit bumper to tear off the bolts rather than in half. While it doesn't make it ultimately stronger, as mentioned in the materials video, people use "strength" rather loosely and they could be referring to it's resistance to deformation.
I think the problem is that most people don't know the difference between stiffness and strength. And what homebuilders most certainly dont know is which one of the two they actually need for their application thus they just slap carbon on top of their fibreglass
5:42 at this case I think it would also help in the case of carbon kevlar fabrics when the carbon breaks the broken piece could hang from the kevlar that would just bend and stay in place till you repair it.
wouldn't it be stiffer if you make carbon fiber the inner layer and fiber glass the outer layer since fiber glass has the higher tensile strength so it will make it hard for the outer layer to stretch when you bend it
This reminds me of Forged In Fire. They like to see the high carbon steel in the middle and the mild steel on the out side of their billets to minimize cracks. Lol
You do not mix them for the same reason why we do not use titanium reinforcement for concrete walls: steel and concrete have the same thermal expansion, hence you can mix them.
I have actually used these kinds of printers, that embed carbon fiber strands within nylon material. It is actually extremely useful for creating very stiff prints. You cannot compare it to this, because you are not using different materials in the same composite. The best way to explain it, is that the nylon material acts as the resin. As you probably know most composites are classed as 'fiber reinforced polymers', meaning that there's fibers (glass/carbon/kevlar etc) embedded in what is called a 'matrix'. The fibers are for strength/stiffness, and the matrix is there for coherence. Usually the matrix used is an epoxy resin, however in the case of these 3D printers the nylon acts as the matrix. It is very difficult to attain high stiffness and strength 3D printed parts, and by using embedded fibers you can create parts that are not possible with just polymers.
Glass fiber is not used for strength or elongation in composition laminates. It is used to electrically isolate aluminum cores from galvanically corroding against the carbon fiber. Otherwise the epoxy acts as an electrolyte between the aluminum and graphite.
Another thing about CF: Without the right process it is not that light, without accounting for the CF. For budget i hear it's much better to have good process and resin for fiberglass, rather than poor process for carbon fiber.
Correct, the only thing to take note of is that pretty much all of the force is applied to the carbon layer as the glass only takes real load when stretched, instead of spreading out across all fibers in a part made out of one material. So it is basically much weaker as it doesn't use the whole objects material to take the load. You would have to take account for the thickness and amount of layers of carbon fiber to bear all the load, at which point the fiberglass is pretty redundant.
okay but if you have carbon fiber on top of fiberglass the carbon fiber will flex less than it would have by itself. You could use the fiberglass as a cheap stiffener and reinforcement for the carbon fiber and the last layer would be carbon fiber to give you a lot of stiffness for interacting with the air. Also although over time you would develop flaws in the final layer and the strength of the product would decline, the breaks in the carbon fiber would not be uniform, it would be compromised in the direction of the most travel but would still give some stiffness in other directions of travel. I would think if you calculated your load and found barely adequate fiberglass with carbon fiber on either side you would get a torsion box effect that would give you a lot of stiffness, and on top of that you are basically making a part that you don't expect to use forever. I'm thinking the sandwiched fiberglass would be less expensive than a comparable strength panel of carbon fiber. I'm curious to know what you think. Like foam board wrapped with poor man's fiberglass or actual fiberglass, the fiberglass reinforced with carbon fiber would end up far superior to the fiberglass by itself.
Seems that if you are for going for looks alone or weight savings, not considering maximum strength, a layer of CF still makes sense. Since most of "Carbon Fiber hood" manufactures often do this to cut cost, since the hood usually is not a structural part.
You’d think, on the stress-strain graph, that the force would have to increase before anything happens. So the elongation of the “limiting” material is not relevant at that point. The carbon fibre protects the fibreglass from further elongation.
A few years ago I remember a guy that made front lip air dams from cf and he added a layer of Kevlar in his words strengthen the cf, they didn't last at all. Now I know why, thanks.
There is another problem. When the carbon breaks, all the strain is focused at the break, so all the elongation is happening right where the carbon broke. This means that in terms of energy absorbed before total failure, the fiberglass alone would be much tougher than is it when carbon fiber is added.
Wrong! What if your just looking for a low cost cosmetic look for a non critical part like a dash board on a car? If you use an elastic glue like contact cement it will give at the seem and still stick like Hells-Hinges as the part expands and then bounce when it cools! It's a great way of making a great looking part at low costs. Just do not use a rigid adhesive. 3M makes some really good high temp and super sticky rubbery contact cements that are designed to glue two dissimilar surfaces together.
There are many composite panels that are made with stiff skins sandwiching a softer core, for a panel with a high general stiffness without much weight. The most common example would be most plywoods. But there are a lot of panels made of CF sandwiching corrugated plastics or NOMEX. Many aircraft panels made just this way. Many aluminum panels made with corrugated plastic or foam cores as well. I think the key is to "balance" the panel by applying the same skin on top and bottom; the bottom panel can be a lower grade...
Yes, there are. Fiberglass isn't generally the core material for a reason though. You want something capable of transferring force between the skins that is lightweight, since the force gets concentrated in the skins anyway. Some plywood has more of a filler core, but that isn't really most plywood, unless I'm mistaken.
Most all plywood is made of cheaper, or lighter weight core material. Even particleboard and MDF has a higher density material toward the outside as opposed to the core.
I don't know where you are getting your MDF but you should consider finding a better source. This is\ a basic starting material in Material Science classes when learning how to run the test equipment for finding material properties. We found no appreciable difference in the entire population of samples we tested and our MDF came from a standard big box store.
If it's made with a filler material, it is not plywood. Plywood is a composite of multiple layers of wood sandwiched together with different grain directions.
When the carbon breaks, all remaining elongation will be focused on the crack because the carbon prevents the rest of the fiber glass from stretching. Instant failure when the carbon let's go is the likely outcome
to be fair your not stretching or bending your cars FG/CF panels. so of course there would be no problem. if its on something that needs to flex a great deal like a bow backing you might run into problems with the CF layer cracking. CF does flex but it has lower limits than FG
As always, great video! I've seen the same principle on gliders. The whole glider is made of carbon fiber and in the cockpit are a also a few? layers of kevlar, to keep it all together in an outlanding.
Martin S. The wings are usually made of carbon these days. Glass could take the load in regards to strength, but modern wings are so thin that the lack of stiffness would mean that the wings would bend so far up that they would not create vertical lift any more. Look at videos of Open Class gliders like ASH25 or EB 28 or EB 29 in flight. You see a lot of flex in these wings. But they are made of carbon fiber, and still flex that much because they are so thin. Imagine the samt made out of glass fiber. They would flex almost straight up, thus probably blocking all control push rods on the way or permanently scraping on the ground when at Stillstand. The fuselage in contrast is a pretty thick pipe in comparison. It also needs to absorb a lot of torsion forces due to the mounting of the elevator on top of the rudder. Thus strength and flexibility and even distribution of loads is more important. The fuselage is usually not a sandwich of an inner and outer fiber layer separated by a thick foam layer but one fiber shell also allowing for more flexibility.
It's probably weaker than just skipping the graphite layer, because once the carbon cracks, the remaining carbon layer still bonded to the lower layers forms a stress riser at the crack, where otherwise it would be uniform.
I tell people Carbon is mostly for Rigidity, not strength. You can make a rigid part much more easily with carbon instead of fiberglass, but carbon does not like to flex and will show signals of failure sooner than a equal component in fiberglass. When it comes to amateur or hobbyist uses of Carbon, fiberglass and kevlar, it involves lots of testing with your materials of choice to find their optimim use.
Idk the kit car I want comes in a fiberglass body. I wanna carbon it to hopefully help it not shift over time and for the looks. But mostly for the looks. Wanna have some raw carbon with clear over top to bury it with the colored sections. Think like the Pagani Zonda.
=edit:= the answer to my question below is found mainly clearified in the previously held discussions i later found among the comments so no need for additional reply here... =end edit= Very good lecture on this topic. i learned a lot of things to take into consideration. 👍🏼 However i do remain confused about the argument to "never layer carbon fiber on top of a glass fiber layered base" 🤔?? pls correct me if I am not interpreting your words properly but it seems like a perfectly good way to build large, light weight, cost-effective "strong" panel out glass fiber base layers that may need some additional "stiffness" properties for its application and size, while keeping weight consequence to a minimum..? I don't see how that's not going to be achieved in this way... no, it will not add any strength to the glass base panel, as to be expected. but replacing the carbon withthe equivalent mass of additional glass would not never yield as much stiffness either right? so as long as strength of the carbon fiber layer is sufficient for the application, it should be a successful improvement. wouldn't it? true enough that a full carbon fiber panel will be just as strong and much stiffer and lighter, it would also add multiple times the cost. alternatively, using a carbon base with a glass top layer would yield a stronger stiff light weight, but still too expensive. and taking out glass mass would improve the weight but at the compromise of strengt right? And in most cases that ive seen, the CF "wrapping goes around both sides, creating a favorable shell construction around a inexpensive core. could you give you math a go at that situation too?, for comparison? cheers
What about putting cf down first and then fg layers. Shouldn't the outer layers of fg have a longer stretch than the cf and all of the layers work together to stiffen a structure
There is a material available at TAP plastics in the US which appears to be a plaid made from carbon fiber and Kevlar. But is it bad to use the different materials in a composite to take advantage of the strengths of the different materials? The plaid carbon fiber / Kevlar cloth seems to me like it would be a good transition material between say a carbon stiffening layer and some fiberglass filler layers or Kevlar base layers.
You usually don't simply add the strength. Kevlar is very good at taking abrasive treatment. so its a good protection for other fibres, but it won't add much to the strenght or stiffness. Its not the point that there is no way of combining different fibres, but you should know what you are doing or you will end up with a not optimal result.
Personally I laminate several carbon layers with a thin layer of fiberglass. The fiberglass is transparent and will add some durability to the surface. This video however; only considers the mechanical aspects of the material. What about heat displacement/ relfection, corrosion resistance, toughness, flex, and torsion? Video is a complete oversimplification, and I feel like you should never say never.
Man. How often do you have stretch loads and how often you have bending? And in bending calculating moment of inertia of cross section you have r^3. Just make materiał symmetrical and calculate only carbon layers, assuming glass inside is not existing and only keeps carbon in place, a filler so it won't collapse. Having for example 25% carbon, 50% glass, 25% carbon, taking into account only carbon and empty space in between you get almost 90% moment of inertia of cross section for having 50% material at maybe 10-15% cost and maybe just a little bit heavier so please explain how it is a bad idea? And most things people do are rather body parts etc that are mostly bent, not stretched. If you want part that will be stretched then yeah, you're right, whole cross section works the same, but you just took one example and based on it made conclusion about all possible cases.
Incomplete analysis. You didn’t consider bending which is the more likely loading and failure mode condition for panels. The tensile loading analysis is somewhat true but the fiberglass is carrying some of the load along with the carbon fiber at 1.4% elongation. Was that included in the 1000 N estimate? Needs clarification.
I wonder how good Kevlar is at reducing resonance in a car body? I wonder if body panels made of kevlar would ever have the same properties as sound deadener? That alone would cut down on weight as having a composite that was strong enough for Body panels, while also being able to cut down on noise and resonance would be the way to go. I wonder how acoustically dense it would perform in something like a speaker box? I have seen many Acrylic and a Few Glass speaker enclosures , but no so much Kevlar as that's used for speaker drivers. I wonder how Areogel would fit into this compostite matrix? And weather that would work well as a Light weight replacement or something like body panels ?
Good video, excellent points. Thank you. A maker of wood strip kayaks was using a layer of carbon fiber on the inside of the hull, fiberglass on the outside. This probably doesn't violate what you're saying (if it seems to, then likely I've left out some important detail.) The point I want to make is I've always paddled wood strip kayaks that I've made. I just got a really nice kevlar/fiberglass kayak that's been damaged. Compared to the wood core kayaks this one seems incredibly fragile, (but I know it's well made.) I'm trying to figure out if I can repair it with just fiberglass. The incredible flexibility of the hull/deck is new to me. The kayaks I've made you could stand on. One thing that does happen after a few years and some minor leaks, is the western red cedar core and the fiberglass (6 oz e-glass) after cycles of wetting, swelling and drying, shrinking, starts separating the exterior glass from the wood core. The interior seems never to do this. Makes sense on a macro scale, the core is essentially a wooden bubble, when it swells it swells outward, never inward. The epoxy still holds, but there's a layer of wood fibers in the fiberglass skin that's peeling off.
Well this reminds me of sword making technology where hard steel is forged(sandwiched) into a soft steel spine (katana), the eye of the blade which is hardsteel would obviously endure all the abuse of contacts, and spine which is soft steel would absorb.
You didn't mention the most significant problem: Shear failure of the resin. Due to the vastly different stiffness of carbon and glass, the glass will elongate way more at a given force. As they are glued together, the glue will be highly strained and will likely break first.
I don't think this actually makes sense. The glass won't elongate more than the carbon fiber, because it's bonded to the carbon fiber. Each strand isn't being pulled individually, but the whole composite together. The carbon fiber will limit the elongation, and therefor the amount of load on the fiberglass.} Sort of like if I hold a steel wire with a hand at both ends, and a rubber band as well, it doesn't matter that the rubber band will stretch more under the load I'm using, because the steel wire is limiting how much the rubber band can stretch. The rubber band can only take up the load that the steel wire's elongation allows it to.
Moral of the story: Always use due diligence when considering two dissimilar materials being adjoined, especially composites. I think we can also safely assume that most of the reasons people would apply CF to E-Glass are for aesthetics, overall cost reduction or skill-set limitations. Why wouldn't people just use Oracle CF vinyl over E-glass, absolutely mental not to have just started from CF alone lol!? Plus adding weight for aesthetics has got to be the OG loon move.
I am going to build a 6 meter length and 1.2 meter width trimaran boat with foam glass fiberglass metod. I want to have an seaworthy ,strong and light weight structure. How to apply my material?and what material is better to use with fiberglass? And wat material to use for outside of boatr skin ?
From what i saw in plants that manufacture European aircrafts, they use a layer of glass fiber base and then lay the carbon fiber film in different orientations. Most of the structures like the spar joints and door joints are basically carbon fiber parts that are reinforced with titanium and glass fiber. can you explain why such key components will not fail.?
I believe his carbon tensile is way too low (reckon 4-7000mpa) which is why it makes the case. You can also wrap "around" parts which is a proper way - outer surface take higher stress.
Hi, I am building a 50 foot free standing ( no wires) yacht mast. I am building a thin (22 mm) walled Douglas fir mast and want to cover it with many layers of 600 g biaxial glass and 330 g unidirectional carbon, both of which I have. Have you any recommendations to the layering. It will be hand wet lay without vacuum bagging. I expect to have a heavy mast which is fine for this application. As it is unstayed I am trying to build the mast as strong as possible. Thanks, Jim
This is correct in the instance he is discussing from a load distribution standpoint. However, he is not discussing FORCE itself that must be applied to actually cause the break. He is only discussing the elongation point of breakage. If I have 3 sticks of wood at 4 mills in circumference and 1 stick in the bundle at 2 mills circumference, the over all force to break the bundle is not equal to the 2 mill nor the 4 mill pieces. This is discussing ELONGATION. Many times, carbon is added as a skin for aesthetics and stiffness while being backed by E-glass. Of course, I guess the High performance super car guys are just wrong? No. It is like anything else, it depends on the PART and what FORCES the parts are subjected to. In fairness, a video was made discussing those uses, however, he certainly doesn't seem to like Carbon Fiber and loves him some E-galss.
What about making a composite structure of Fiberglass and Kevlar? If I were to build a racecar's monocoque out of a mix of Fiberglass and Kevlar woven or knitted together, would the fiberglass make up for the Kevlar's weakness in compression? How much fiberglass would you need to achieve this, and would there still be enough Kevlar to give it a similar weight to Carbon Fiber?
You are the right guy to ansewer properly some old questton and myths in the 2 stroke engine industry\tuning. -Knife edge porting of the transfers(good or bad, faster or slower flow)? -Drilling airbox, more air or not compared to a stock airbox with a snorkel like the rotax 122 airbox.
Then what to use in the middle of the sandwich? If the outside is glass then the inside needs to be hard and light like CF, but less expensive than GF. Is there such a material?
wouldn't the fact that they are bonded together with adhesive transfer energy between them, making them more like one another and gain a little in their lacking properties?
Yeah, wasn't sure if he was trying to simplify it or whether it was an oversight. Because the carbon fiber has a higher modulus, it would see less strain. You wouldn't see 1.4% in one layer and then 4.8% in the next layer... if you did you screwed up.
krap101 when i wrote that comment i realised for the first time that the elements and materials at least in part become a new hybrid element when together than when apart. the combinations and expressions of the forces of this universe are trippy, reality / existence is trippy.
I bet in bending it's going to be close to what the video describes. Plus in many cases in real life, even if we design our structure to be purely in tension/compression, we're going to get bending anyway.
He wasn't saying the strain on one would be 1.4% and 4.8% on the other. He said that the carbon fiber fails at 1.4% elongation, and the fiberglass fails at 4.8% elongation, so when the part reaches 1.4% elongation, the carbon fiber will fail, and the fiberglass will then take all the load.
My question is if you are doing this to save cost and the part is purely for cosmetics is there any reason not to do it? For example if you're making a switch plate. It's not design to take any stress but you still want the Cosmetics of carbon fiber with the added benefit of the low cost of fiberglass
Dude....this is insanly helpful..... been trying to understand some things for weeks with lots of hours of reading but it doesnt get easier... please i beg you, in the boat building forums i try to find some proper info, i even try to read definisions about shear strain/modulous/strenght/elongate etc.... It only gets more complicated.... can you maybe make a video talking about the SAN-PVC-PET foam cores ? my numbers dont add up. I see for example that a stiff correcell is more flexible than PET (58% vs 7%) yet PET is advertised as the future and replacement of PVC and SAN. What is going on mate....i am confused :(
Hi, I very enjoy your videos, but perhaps I have to disagree on this one for many reasons.
First, many industries adopt glass/carbon composites in many components. Wind turbine blades are a good example. Second, you don't design to max elongation ever, first because you usually have more constraints on structural failures (like safety factor on strength and buckling) that restrain your design. Therefore, it is doubtful that any part of your structure reaches the elongations that you show in the video under nominal conditions. Third, fibreglass is more resilient to impact, and it can extend your laminate life when something not predicted happens. This means that if there is a crack somewhere, glass fibres will prevent that to spread in the laminate. Finally, since under nominal conditions, the laminate life span is only linked to the time required to micro-cracks (which are there since consolidation) to bridge and become macro-cracks (a.k.a. broken part), we can definitely state that those glass fibres will increase the fatigue capabilities. Each and every good design must consider fatigue, and glass is way better in that than basically any other fibre. Therefore a well designed glass-carbon hybrid aims to find that sweet spot between pure stiffness and long life span, which could correspond to an overall lighter structure. Ultimately, I suggest adding another layer on top of the carbon for a glossy finish. Once wet, it will become crystal clear while protecting the laminate underneath.
In other words, I would like to let you notice that if your component has reached the point at which the carbon is broken (like you say in this video), your structure must be considered failed. The fact that you still have some fibres that can carry some load means that if that was your structure, it is now less stiff, but it is still one piece! I am sure that in F1 the safety coefficients might be very close to one and that resilience has a different meaning than for aerospace structural engineers like myself. However, trust me... If that was the hull of your boat in the middle of the ocean, you would have been glorifying and blessing the carbon-glass mix that keeps your boat afloat! You might not be able to cruise at full speed anymore, but you are not on the bottom of the ocean as it would have happened with a carbon hull that cracks in a blink of an eye... Please go and search some interesting peer-reviewed papers on hyperduct... it is an ongoing work on glass-carbon laminate to simulate yielding for highly resilient composites.
Cheers,
ummm good read, i just wanna add a fiber glass layer to prevent galvanic corrosion to steel body
e glass and finer glass are not for the same purpose ... e glass is used in high bending parts like wings on a jet liner ... while fiber glass and S glass are used for high strength parts like engine nacelles and tail planes ... if he compared E glass to EDR glass and carbon fiber to S glass he would have made one point ... carbon fiber is expensive and s glass is cheaper ...
E glass and EDR glass are BOTH flexible edr glass can be made conductive like carbon fiber .. which is why it is used in wings ... while carbon fiber in engine nacelles need strength over flex ... where carbon fiber comes in handy because it is less weight for the same strength as S glass ...
and of course Galvanic corrosion will happen with carbon fiber and edr glass so using s glass or e glass as a boundary layer between metal and the conductive fibers is mandatory to avoid that ... but then you also make a capacitor and need to channel the charge off the fiber ...
In the example he gives, the carbon would likely weaken the structure. The surface crack would cause a stress concentration in the underlying layers. (Always a consideration if you have layers of material; e.g. chrome plating suspension parts is a bad idea unless there's lots of something ductile like copper underneath to smooth out the cracks from the surface.)
It is not related with Chrome plating here, plating is chemical process which is not physical/mechanical related topic. But in general, Chrome plating weakens most of the metal materials because of acidic process damages the surface finishing of the part, causes micro cracks in surface weakens fatigue strengths of part.
he is comparing a strength fiber with little flex against a flex fiber with lower strength ... he should have used S glass ... as it is a strength fiber with minimal flex ... and instead of carbon fiber for e glass EDR glass ... as it is also high flex and conductive ...
one fiber is not the same as the other ... he is literally comparing a rubber band to an I beam and saying the I beam sucks as a spring ... which is true ... but the rubber band sucks as a support ...
This is correct and incorrect depending on the application. Look at a Mongolian short bow it uses a lamination of substances with different stretch and strength properties to achieve it's goal. So adding a layer of CF may actually be desirable if you wish to alter the flexing of a component in one direction like on a wing.
the method to making those composite bows also applied to make wing plane.
Or a razor blade, including layer of soft metal inside. Somehow it is much better than steel itself.
Yes, as long as the stress of the product is less than the maximum of carbon not fibreglass.
For an archery bow, I would add the carbon on the belly side, and the fiberglass on the back side, so the fiberglass could elongate more. Or sandwich fiberglass on the outside, with layers of carbon fiber on the inside, since most elongation is on the outside, so you could use both materials for strength.
@@RMWeinberg yep, this is how some wind turbine blades are designed, carbon beam on the inside of glass layers for added stiffness.
My use of carbon fiber "beauty" layer for non-loadbearing panels that need the stiffness...hoods, bumper covers, rear deck lids, fenders, etc. allows me to avoid painting those panels and keep cost down by using fiberglass for the core structure. I use S-glass for loadbearing structure and carbon fiber alone for interior panels...dash, door cards, pillar skins, etc. and other parts that need to be lightweight but aren't subjected to high stresses or impacts. Probably not necessary but, so far, no unexpected issues. Thanks for your expertise. I learn a lot from your videos.
Structures break from stress points caused by deformation under load far before reaching the tensile strength of the material. A layer of carbon on the exterior can greatly in crease stiffness helping a structure to maintain its shape. Strength should be in the design more so than the material.
Not completely true if the structure is under significant load due to the difference between carbon and glass fiber. Fiberglass wants to stretch a little bit before it takes a lot of force, carbon fiber on the other hand doesn't really like to stretch at all. So by having an exterior layer of carbon fiber in parallel to the fiberglass under the same load, the carbon fiber will take all the load, while the fiberglass will only take a little bit. This means the carbon fiber will break before the fiberglass takes any significant load, which then transfers all that load to the fiberglass and it will fail too. Comparing that to the same structure made completely out of fiberglass or carbon fiber, it becomes much stronger as all the fibers will be spreading out the load throughout the whole piece instead of just the individual layers.
If your making critical parts yes. Most parts are body panels and noload parts and interior ttim ehich isnt going to matter.
Great video !
At that point just use fake carbon fibre because you don’t care about it’s properties
Another feature is the stress concentration which will occur when the carbon fiber breaks. At that point, the load the carbon fiber was carrying will be taken up by the remaining layers of fiberglass at the break. The result will be similar to nicking a sheet of plastic: once there is a stress concentration, there will be accelerated total failure. Destructive testing will easily show this.
There is a specific case where a combination of carbon fibre and fibre glass in sandwich construction on boats resulted in much greater impact resistance than either material alone however I don't remember where I found the research paper and I don't know how that would translate without the foam middle layer of marine sandwich construction or above water.
A lot of composite parts are stiffness driven and strength is secondary. Eg car body panels if it's stiff enough not to flop around then it's most likely strong enough to survive rocks or whatever debris you normally throw at it. Using fibreglass as the core to build thickness and carbon fibre at the edges is still a valid cheaper way to make composite panels with 90% of the bending stiffness of a homogeneous carbon composite.
well he is only talking about something that will be receiving tensile stress. i don't think a door or a hood is going to see that much... but things like wings and what not definitely would and it would concentrate a lot of force at a single point.... so if across the surface its receiving a 2% tension.... the fiber would break... and now instead of across the whole body the tension is focused at the break.... and that 2% goes up to something like 6%.... well you just snapped your spoiler
If your goal was to build thickness, and not to provide strength, surely you'd go for a lightweight core material? Again, I'm not sure of any case where you'd want to do this for performance reasons. You're not getting the extra strength of the fiberglass until the carbon fiber fails, and once that happens, you're not getting the stiffness of the carbon fiber. If stiffness is critical, you wouldn't want a fiberglass core in your carbon fiber, and if strength is critical, you wouldn't want a carbon fiber skin on your fiberglass.
incorrect. I made parts for FSAE cars out of carbon fibre. and although they were stiff as hell the rocks from the wheels made the edges crack a lot.
just because something is stiff doesnt mean it's strong. Maybe watch the video again because it seems you didn't listen or understand what's been said
This is the reason why wheel arches on GTE cars are not carbon fibre but rather kevlar and glass composites
I would be very interested in your thoughts on Carbon Kevlar hybrid cloths and their use.
Like he said he has another video on that....
@@walkertongdee he said carbon fiber vs fiberglass vs kevlar, nothing about carbon kevlar hybrid cloths...
From what I understand, carbon/kevlar is good for applications where flexibility is needed.
And he throws out the exception of chopped strand mat, but doesn't address woven + mat layup. Or foam core, honeycomb, or any other variable layup that is most composites.
A hybrid fabric is designed to work with itself quite nicely. LOL If you're building a critical part you're not using E glass, you're using S Class! Since S glass either meets or exceeds both Kevlar and carbon fiber. Once again you wouldn't make a critical part out E Class. And if you build all your strength first and then want to put a pretty layer of carbon fiber on it, it matters or not, since you're not relying on any strength of the carbon fiber. I have built a few sets of composite landing gear. The heaviest plane having a gross of 1300 pounds. And I have done that with alternating layers of S-Glass and foam. you can't destroy this landing gear. LOL and then to make it look exotic I top it off with the layer of textream and zylon hybrid. It would be nice to build everything out of textream and zilon . But it's 70 - $80 + a yard....
Loads of people have commented on your video with some very good points, the main one that seems to make the most important point is that when the layers of e-glass and carbon fibre are bonded together they become a singular entity. If one portion of the composite fails under any kind of stresses, the other layers withstand it somewhat so as not to have a complete failure. Also remember why carbon fibre is used in the first place, strength to weight ratio and stiffness.
I agree I know this has nothing to do with it. It's just an example for myself to reply and agree with yourself. [ Gold & Siver ] Strength in their own materials. But, adding Silver to Gold or the other way around. One will weaken the other right?
Which is heavier? Not sure I would think Gold is or would be heavier than Silver.
Katanas have a flexible core steel, and a more brittle steel hotdog bunned around it for a sharper more durable edge. Infinity CMMD technology is also worth checking out, it uses an aluminum core of 60% sandwiched between 20% alumina(ceramic) on both sides. They do this so that the layers constrain each other as they each have different speeds of sound propagation, the layers dampen each other’s resonant vibrations, and it is also a stiff and light weight combo. Great for speakers.
Laminating Carbon fiber on top of fiberglass(usually S glass not E glass) comes from the aerospace world. When trying to maximize certain characteristics while keeping weight extremely low you can add a layer or two of carbon fiber. The introduction of cheaper Kevlar has made this less used but still a completely viable way to remove flex from “bouncy” items in a racing plane. I’ve saw a few Formula 1 racing planes that use this on the fuselage and wings. They are painted afterwards so look is definitely not the goal.
but still, 1 layer of such carbon fiber can take 170kg attached and not break, and it's just 1 layer, that is epic
I used carbon fiber over few fiberglass parts with great success. The secret is to lay couple of layers in different direction and use epoxy rather than polyester. The part was twice stronger than the flimsy original. Especially when is applied on both sides. Also, built couple diffusers with foam and carbon fiber that were very strong...actually couple of racing boats were built with the same materials with incredible strength.
Carbon fiber over foam is a completely different thing, and if you're adding enough carbon fiber to be stronger than the fiberglass, of course that would strengthen it.
You're probably confusing stiffness with strength though.
You forgot to mention the load distribution before failure.
Based on stiffness and strength the 3 GF to 1 CF, carbon fibre will still carry ~60% of imposed load until failure at 1.4% strain when structure will experience rapid jump of stress on GF from 40% to 100% of imposed load.
Great video. Great advice.
There isn't some people that do this, there is alot of people and even most well known aftermarket companies. They combine fiberglass(strand Mat) and fiberglass together. They also put black pigment in the resin so the back side is all black. I understand the cost can be really high but it defeats the purpose of an actual carbon fiber part. I will admit, when I was younger I did by a cf hood that was made like this not knowing.
You can also tell by drilling into the part. If its a spoiler and are making mounting points. You will see the white fiberglass shavings come out. They also make dyed black woven mat.
About the cracking, I see it all the time on hoods. And alot of people buy carbon mainly for the looks. Im a bit of a sleeper, I paint my cf parts. But thats just me.
I have been trying to figure out how to make 4x4 chassis armor without a welder and plasma cutter. This video and the last one have been very helpful.
I would have never considered s glass on my own without seeing the charts.
If you needed a part that required tensile strength, rigidity, puncture resistance, thin lightweight, impact and chemical resistance and abrasive resistance, combining different materials would be necessary right? But as you said wrapping s-glass with carbon fibre looks good however not so great functionally. S-glass over carbon fibre would seem to be a better choice.
The s-glass would receive and absorb the initial force and distribute it before hitting the carbon fibre right? This would allow the carbon to act like a bone under softer tissues.
If you covered the s-glass with Kevlar the structure would gain abrasive and puncture resistance. That could then be covered by Mylar and gain thermal, chemical, dielectric and impact resistance. I would think it better that the Mylar be between the Kevlar and s-glass but to my knowledge resins will not bond properly to Mylar causing separations in the layers.
You can layer the carbon fibre, s-glass then Kevlar sheets then cover it with the Mylar. NASA studies have shown using "Sure Bonder 9001" to secure the Mylar to other surfaces works best.
Stack and vacuum form the first three layers, apply adhesive and Mylar to the dried unit and vacuum seal the Mylar.
The vacuum forming will help maintain consistency and uniformity in the projects thickness as well as help remove excess resin reducing weight.
Just Thinkingoutloud
This talk needs a demonstration of layups on a test rig. When I've seen talk of mixed layups I've normally seen the carbon added for stiffness when a part is already strong enough, with the fiberglass for toughness and cst savings.
I love your video's mate, it's very rare even on youtube that someone actually posts numbers and can confirm it.
Depends on the channel check out engineering explained if you are interested in basically the car equivalent to this (I'm not affiliated just a fan his videos are very interesting)
Carbon over Fiberglass works great for looks... and for some people, aesthetics are far more important than everything else on a daily, not a track car. So... even if is weaken than a real carbon piece, or less lighter... I don't even care about. It is by miles, the cheapest :)
I 100% agree if you're making a structural part, however, if it's mostly a cosmetic or lightly loaded part then it's a cheaper way to simulate the look without any down sides.
1) Amazing timing with the sub accident for this to be recommended
2) Also this is being discussed in the cycling community as companies are putting fiber glass in the forks to prevent galvanic corrosion
your channel is amazing for FSAE team members
What would happen if you alternated the layers of two different materials? Or what if someone made a carbon-glass composite?
Also, does resin effect the numbers in any way?
@KYLE.ENGINEERS pls answer
The resin does effect the strength very much.
Love the video! What if I went for the reverse configuration (carbon inside, glass outside) to provide strength against bending? The outer layers will elongate more than the inner layers, allowing the glass to take more of the stress. Just curious. Thanks!
To prevent corrosion problems an outer layer of glass may be sensible.
Cool. True, some RUclipsrs carbon fiber people (do it for a living) alternate the layers of fiberglass and carbon fiber with cf on top but for me I'd like to make it all out of carbon fiber like Koenigsegg and Pagani.
This feels like Jason's Engineering Explained and my automotive + shop high school class.
God bless.
seems to me that coating fiberglass in carbon fiber would actually make it worse, because when the carbon fiber breaks, the fiberglass is suddenly taking all the force in a sort of shockwave as it suddenly flexes, plus the carbon fiber is still stabilizing the two sections on either side, creating a weak point where the split is that becomes almost like a hinge, ready to snap it
As opposite to the fiberglass taking the entire force from the source? The initial force already creates a "shockwave".
It seems more intuitive that the carbon layer will dissipate some of the initial force from the source, leaving only the remainder of the force to be taken by the fiberglass.
Either way, wrapping fiberglass with a layer of CF would negate the purpose of using CF as explained in the video.
I wouldn't even go by shock load. The de-lamination of the carbon fiber would ad a defect crack in the resin. Blamo. The setup is damaged.
no you can make fiberglass backed bows so snapping force isn't a big deal the flexibility and strength is great for it. where as carbon fiber wouldn't work.
I don't want to say this video is pointless, because elongation is actually a point. But there are other things why I will continue doing this. There are many points why it is actually good to combine various mats.
And yet you have stated none.
@@seigeengine The video is good and makes a valid point. Your point is also valid. Some of the other properties you may want include increased rigidity, buckling resistance, flutter control, abrasion protection. Each design is different, so I am certain that I am missing some properties.
Kyle, have you ever used basalt fibers or composites based on basalt fibers?
awesome video! very informative than just showing "how-to" for me it's more important to answer "why" and rationale.
Awesome video as always kyle. I want to note as well that the microphone quality is absolutely astounding in this video!! The improvements youve been making have been well worth it on that front. Cheers!
Thanks Chris! This was my first video with my new camera, it had better preamps in it which allows me to use my nicer mic. Also has 60fps and 4k capabilities! I still haven't gotten used to the exposure settings on it though, as you can probably tell in the video.
Why do people wrap wood cores in fiberglass then? Wood bends more and is heavier - so what is the point of fiberglass as the outer layer? Boats, wakeboards, skis, snowboards, aircraft (before aluminum), etc, etc.....They all use that type of construction. What do you know that all of those engineers don't? Or is it something they know that you don't?
If it's engrain balsa wood, that's a core. The core is there to prevent the skin from buckling.
Wood/mass is also good at absorbing vibration.
This video is saying don't skin your wood with glass and then lastly carbon.
Wood absorbs water. The fiberglass is like a waterproof layer.
E (young's modulus) for wood is about 10 to 15 GPa (depending on grade/species etc). E for fibreglass is 70-80 GPa which gives it much more stiffness in bending applications. It gives the wood strength in cross grain applications. It helps water proof the wood. The design strength of fibre glass is also much higher than soft woods and you get much higher strengths in bending applications.
@@yodaiam1000 - *Thanks for proving my point!*
Fiberglass gives rigidity to wood cores, just like carbon fiber would give rigidity to fiberglass cores. As far as your "cross grain" argument - wood cores are layered perpendicular, so there is no "cross grain".
@@ezraboren2069 - Not true. Epoxy, enamel, or some kind of urethane would achieve the waterproofing - there is no need for fiberglass in waterproofing.
Really interesting, it confirms what I have learnt in the last few years making fibre fins for underwater hockey, lots of flexing...
I can't believe people blew by this comment. Underwater hockey? WTF? I've got to go look this up. I wanna play!
what composites are best to make a crash structure, something that can crumple but only in like a car crash? how would you align the fibers' sheets? how much resin? what kind of resin? do we need a controlled environment for resin application on sheets? Is there a composite with even lower density that can allow for more crash structure volume but without compromising strength and integrity of passenger cell?
so fibreglass wrapping a cf piece would be of use if you wanted to increase the parts ability to hold together without cracking without compromising it's stiffness?
Surely it's enhancing stiffness at low deformation (say airflow over a bumper) regardless? By placing it on the face of a bumper it would help it keep shape at speed then by thinning the carbon at bolt holes, force a hit bumper to tear off the bolts rather than in half. While it doesn't make it ultimately stronger, as mentioned in the materials video, people use "strength" rather loosely and they could be referring to it's resistance to deformation.
I think the problem is that most people don't know the difference between stiffness and strength. And what homebuilders most certainly dont know is which one of the two they actually need for their application thus they just slap carbon on top of their fibreglass
Not information that I really needed, but it makes perfect sense.
Buy some black pigment to add to the resin for your fiberglass. Your friends will never know.
5:42 at this case I think it would also help in the case of carbon kevlar fabrics when the carbon breaks the broken piece could hang from the kevlar that would just bend and stay in place till you repair it.
wouldn't it be stiffer if you make carbon fiber the inner layer and fiber glass the outer layer since fiber glass has the higher tensile strength so it will make it hard for the outer layer to stretch when you bend it
This reminds me of Forged In Fire. They like to see the high carbon steel in the middle and the mild steel on the out side of their billets to minimize cracks. Lol
You do not mix them for the same reason why we do not use titanium reinforcement for concrete walls: steel and concrete have the same thermal expansion, hence you can mix them.
This video was preceded by an advertisement for carbon fiber 3D printing where you add a layer of carbon fiber to other objects lol.
I have actually used these kinds of printers, that embed carbon fiber strands within nylon material. It is actually extremely useful for creating very stiff prints.
You cannot compare it to this, because you are not using different materials in the same composite. The best way to explain it, is that the nylon material acts as the resin. As you probably know most composites are classed as 'fiber reinforced polymers', meaning that there's fibers (glass/carbon/kevlar etc) embedded in what is called a 'matrix'. The fibers are for strength/stiffness, and the matrix is there for coherence. Usually the matrix used is an epoxy resin, however in the case of these 3D printers the nylon acts as the matrix.
It is very difficult to attain high stiffness and strength 3D printed parts, and by using embedded fibers you can create parts that are not possible with just polymers.
Glass fiber is not used for strength or elongation in composition laminates. It is used to electrically isolate aluminum cores from galvanically corroding against the carbon fiber. Otherwise the epoxy acts as an electrolyte between the aluminum and graphite.
Could you elaborate? Real world example, layup structure etc?
Another thing about CF: Without the right process it is not that light, without accounting for the CF.
For budget i hear it's much better to have good process and resin for fiberglass, rather than poor process for carbon fiber.
Until the carbon fiber breaks, doesn't it add more rigidity?
Correct, the only thing to take note of is that pretty much all of the force is applied to the carbon layer as the glass only takes real load when stretched, instead of spreading out across all fibers in a part made out of one material. So it is basically much weaker as it doesn't use the whole objects material to take the load. You would have to take account for the thickness and amount of layers of carbon fiber to bear all the load, at which point the fiberglass is pretty redundant.
okay but if you have carbon fiber on top of fiberglass the carbon fiber will flex less than it would have by itself. You could use the fiberglass as a cheap stiffener and reinforcement for the carbon fiber and the last layer would be carbon fiber to give you a lot of stiffness for interacting with the air. Also although over time you would develop flaws in the final layer and the strength of the product would decline, the breaks in the carbon fiber would not be uniform, it would be compromised in the direction of the most travel but would still give some stiffness in other directions of travel. I would think if you calculated your load and found barely adequate fiberglass with carbon fiber on either side you would get a torsion box effect that would give you a lot of stiffness, and on top of that you are basically making a part that you don't expect to use forever. I'm thinking the sandwiched fiberglass would be less expensive than a comparable strength panel of carbon fiber.
I'm curious to know what you think.
Like foam board wrapped with poor man's fiberglass or actual fiberglass, the fiberglass reinforced with carbon fiber would end up far superior to the fiberglass by itself.
Now coat it with resin. What is the elongation of the resin?
What is the point that your making, most of the time, ppl mix just for the look..
Seems that if you are for going for looks alone or weight savings, not considering maximum strength, a layer of CF still makes sense. Since most of "Carbon Fiber hood" manufactures often do this to cut cost, since the hood usually is not a structural part.
You’d think, on the stress-strain graph, that the force would have to increase before anything happens. So the elongation of the “limiting” material is not relevant at that point. The carbon fibre protects the fibreglass from further elongation.
What is the load at which the fiberglass would stretch to 1.4% ?
A few years ago I remember a guy that made front lip air dams from cf and he added a layer of Kevlar in his words strengthen the cf, they didn't last at all.
Now I know why, thanks.
have no sense without study of the structure and forces what is composite are made for.
There is another problem. When the carbon breaks, all the strain is focused at the break, so all the elongation is happening right where the carbon broke. This means that in terms of energy absorbed before total failure, the fiberglass alone would be much tougher than is it when carbon fiber is added.
Wrong! What if your just looking for a low cost cosmetic look for a non critical part like a dash board on a car? If you use an elastic glue like contact cement it will give at the seem and still stick like Hells-Hinges as the part expands and then bounce when it cools! It's a great way of making a great looking part at low costs. Just do not use a rigid adhesive. 3M makes some really good high temp and super sticky rubbery contact cements that are designed to glue two dissimilar surfaces together.
There are many composite panels that are made with stiff skins sandwiching a softer core, for a panel with a high general stiffness without much weight. The most common example would be most plywoods. But there are a lot of panels made of CF sandwiching corrugated plastics or NOMEX. Many aircraft panels made just this way. Many aluminum panels made with corrugated plastic or foam cores as well. I think the key is to "balance" the panel by applying the same skin on top and bottom; the bottom panel can be a lower grade...
Yes, there are. Fiberglass isn't generally the core material for a reason though. You want something capable of transferring force between the skins that is lightweight, since the force gets concentrated in the skins anyway.
Some plywood has more of a filler core, but that isn't really most plywood, unless I'm mistaken.
Most all plywood is made of cheaper, or lighter weight core material. Even particleboard and MDF has a higher density material toward the outside as opposed to the core.
I don't know where you are getting your MDF but you should consider finding a better source. This is\ a basic starting material in Material Science classes when learning how to run the test equipment for finding material properties. We found no appreciable difference in the entire population of samples we tested and our MDF came from a standard big box store.
If it's made with a filler material, it is not plywood. Plywood is a composite of multiple layers of wood sandwiched together with different grain directions.
When the carbon breaks, all remaining elongation will be focused on the crack because the carbon prevents the rest of the fiber glass from stretching. Instant failure when the carbon let's go is the likely outcome
Are you sure about this? Your explanation seems very reasonable but carbon fiber looks so cool it's a shame if it makes a part weaker.
I was thinking to do a "carbon layer" over a fiber/glass part instead of painting it, surely that is stronger combination...
This video left me wondering if the carbon fibre would make the part weaker or not. As you suggest, carbon fiber would make a nice cosmetic layer.
they both well together i made my hole car like this. 18 years later and still no problems.
What`s a `hole` car?
@@pyroarch57 if its for looks who cares... now if its for anything that's going to take load...
to be fair your not stretching or bending your cars FG/CF panels. so of course there would be no problem. if its on something that needs to flex a great deal like a bow backing you might run into problems with the CF layer cracking. CF does flex but it has lower limits than FG
As always, great video! I've seen the same principle on gliders. The whole glider is made of carbon fiber and in the cockpit are a also a few? layers of kevlar, to keep it all together in an outlanding.
i think the kevlar is there for abrasion resistance but i may be wrong
dvirus2000 abrasion, and impact, particularly the occasional rock on a field.
Martin S. The wings are usually made of carbon these days. Glass could take the load in regards to strength, but modern wings are so thin that the lack of stiffness would mean that the wings would bend so far up that they would not create vertical lift any more.
Look at videos of Open Class gliders like ASH25 or EB 28 or EB 29 in flight. You see a lot of flex in these wings. But they are made of carbon fiber, and still flex that much because they are so thin. Imagine the samt made out of glass fiber. They would flex almost straight up, thus probably blocking all control push rods on the way or permanently scraping on the ground when at Stillstand.
The fuselage in contrast is a pretty thick pipe in comparison. It also needs to absorb a lot of torsion forces due to the mounting of the elevator on top of the rudder. Thus strength and flexibility and even distribution of loads is more important. The fuselage is usually not a sandwich of an inner and outer fiber layer separated by a thick foam layer but one fiber shell also allowing for more flexibility.
It's probably weaker than just skipping the graphite layer, because once the carbon cracks, the remaining carbon layer still bonded to the lower layers forms a stress riser at the crack, where otherwise it would be uniform.
I tell people Carbon is mostly for Rigidity, not strength. You can make a rigid part much more easily with carbon instead of fiberglass, but carbon does not like to flex and will show signals of failure sooner than a equal component in fiberglass.
When it comes to amateur or hobbyist uses of Carbon, fiberglass and kevlar, it involves lots of testing with your materials of choice to find their optimim use.
Idk the kit car I want comes in a fiberglass body. I wanna carbon it to hopefully help it not shift over time and for the looks.
But mostly for the looks. Wanna have some raw carbon with clear over top to bury it with the colored sections. Think like the Pagani Zonda.
So if I understand this correctly it would make more sense to wrap carbon fiber with fiber glass for Optimal strength?
=edit:=
the answer to my question below is found mainly clearified in the previously held discussions i later found among the comments so no need for additional reply here...
=end edit=
Very good lecture on this topic. i learned a lot of things to take into consideration. 👍🏼 However i do remain confused about the argument to "never layer carbon fiber on top of a glass fiber layered base" 🤔??
pls correct me if I am not interpreting your words properly but it seems like a perfectly good way to build large, light weight, cost-effective "strong" panel out glass fiber base layers that may need some additional "stiffness" properties for its application and size, while keeping weight consequence to a minimum..? I don't see how that's not going to be achieved in this way...
no, it will not add any strength to the glass base panel, as to be expected. but replacing the carbon withthe equivalent mass of additional glass would not never yield as much stiffness either right? so as long as strength of the carbon fiber layer is sufficient for the application, it should be a successful improvement. wouldn't it?
true enough that a full carbon fiber panel will be just as strong and much stiffer and lighter, it would also add multiple times the cost. alternatively, using a carbon base with a glass top layer would yield a stronger stiff light weight, but still too expensive. and taking out glass mass would improve the weight but at the compromise of strengt right?
And in most cases that ive seen, the CF "wrapping goes around both sides, creating a favorable shell construction around a inexpensive core. could you give you math a go at that situation too?, for comparison?
cheers
What about putting cf down first and then fg layers. Shouldn't the outer layers of fg have a longer stretch than the cf and all of the layers work together to stiffen a structure
There is a material available at TAP plastics in the US which appears to be a plaid made from carbon fiber and Kevlar. But is it bad to use the different materials in a composite to take advantage of the strengths of the different materials? The plaid carbon fiber / Kevlar cloth seems to me like it would be a good transition material between say a carbon stiffening layer and some fiberglass filler layers or Kevlar base layers.
You usually don't simply add the strength. Kevlar is very good at taking abrasive treatment. so its a good protection for other fibres, but it won't add much to the strenght or stiffness.
Its not the point that there is no way of combining different fibres, but you should know what you are doing or you will end up with a not optimal result.
Personally I laminate several carbon layers with a thin layer of fiberglass. The fiberglass is transparent and will add some durability to the surface. This video however; only considers the mechanical aspects of the material. What about heat displacement/ relfection, corrosion resistance, toughness, flex, and torsion? Video is a complete oversimplification, and I feel like you should never say never.
Man. How often do you have stretch loads and how often you have bending?
And in bending calculating moment of inertia of cross section you have r^3. Just make materiał symmetrical and calculate only carbon layers, assuming glass inside is not existing and only keeps carbon in place, a filler so it won't collapse. Having for example 25% carbon, 50% glass, 25% carbon, taking into account only carbon and empty space in between you get almost 90% moment of inertia of cross section for having 50% material at maybe 10-15% cost and maybe just a little bit heavier so please explain how it is a bad idea?
And most things people do are rather body parts etc that are mostly bent, not stretched.
If you want part that will be stretched then yeah, you're right, whole cross section works the same, but you just took one example and based on it made conclusion about all possible cases.
Incomplete analysis. You didn’t consider bending which is the more likely loading and failure mode condition for panels. The tensile loading analysis is somewhat true but the fiberglass is carrying some of the load along with the carbon fiber at 1.4% elongation. Was that included in the 1000 N estimate? Needs clarification.
I wonder how good Kevlar is at reducing resonance in a car body? I wonder if body panels made of kevlar would ever have the same properties as sound deadener?
That alone would cut down on weight as having a composite that was strong enough for Body panels, while also being able to cut down on noise and resonance would be the way to go.
I wonder how acoustically dense it would perform in something like a speaker box?
I have seen many Acrylic and a Few Glass speaker enclosures , but no so much Kevlar as that's used for speaker drivers. I wonder how Areogel would fit into this compostite matrix? And weather that would work well as a Light weight replacement or something like body panels ?
Good video, excellent points. Thank you. A maker of wood strip kayaks was using a layer of carbon fiber on the inside of the hull, fiberglass on the outside. This probably doesn't violate what you're saying (if it seems to, then likely I've left out some important detail.) The point I want to make is I've always paddled wood strip kayaks that I've made. I just got a really nice kevlar/fiberglass kayak that's been damaged. Compared to the wood core kayaks this one seems incredibly fragile, (but I know it's well made.)
I'm trying to figure out if I can repair it with just fiberglass. The incredible flexibility of the hull/deck is new to me. The kayaks I've made you could stand on. One thing that does happen after a few years and some minor leaks, is the western red cedar core and the fiberglass (6 oz e-glass) after cycles of wetting, swelling and drying, shrinking, starts separating the exterior glass from the wood core. The interior seems never to do this. Makes sense on a macro scale, the core is essentially a wooden bubble, when it swells it swells outward, never inward. The epoxy still holds, but there's a layer of wood fibers in the fiberglass skin that's peeling off.
How about some motorcycle helmet? i see some of the major brand use a mixture fiberglass, carbon fiber and kelvar
I don’t believe this guy has any actual proof. Just paper numbers. There are reasons thousands of manufacturers build hybrid parts.
@@jordanf2022 well he got a job in Formula 1 so...
@@jordanf2022 a hybrid and just one layer on top is totally different
What about carbon fiber as the first or base layer, and then another couple of layers of fiberglass?
What if the carbon layer is in the centre, would that be stiffer but not weaker ?
How about fixing/wrapping carbon fiber with fiberglass?
Oh, stop it.
Well this reminds me of sword making technology where hard steel is forged(sandwiched) into a soft steel spine (katana), the eye of the blade which is hardsteel would obviously endure all the abuse of contacts, and spine which is soft steel would absorb.
You didn't mention the most significant problem: Shear failure of the resin. Due to the vastly different stiffness of carbon and glass, the glass will elongate way more at a given force. As they are glued together, the glue will be highly strained and will likely break first.
I don't think this actually makes sense. The glass won't elongate more than the carbon fiber, because it's bonded to the carbon fiber. Each strand isn't being pulled individually, but the whole composite together. The carbon fiber will limit the elongation, and therefor the amount of load on the fiberglass.}
Sort of like if I hold a steel wire with a hand at both ends, and a rubber band as well, it doesn't matter that the rubber band will stretch more under the load I'm using, because the steel wire is limiting how much the rubber band can stretch. The rubber band can only take up the load that the steel wire's elongation allows it to.
Yes, exactly. So the bond fails in shear first.
Moral of the story: Always use due diligence when considering two dissimilar materials being adjoined, especially composites. I think we can also safely assume that most of the reasons people would apply CF to E-Glass are for aesthetics, overall cost reduction or skill-set limitations. Why wouldn't people just use Oracle CF vinyl over E-glass, absolutely mental not to have just started from CF alone lol!? Plus adding weight for aesthetics has got to be the OG loon move.
I am going to build a 6 meter length and 1.2 meter width trimaran boat with foam glass fiberglass metod. I want to have an seaworthy ,strong and light weight structure. How to apply my material?and what material is better to use with fiberglass? And wat material to use for outside of boatr skin ?
From what i saw in plants that manufacture European aircrafts, they use a layer of glass fiber base and then lay the carbon fiber film in different orientations. Most of the structures like the spar joints and door joints are basically carbon fiber parts that are reinforced with titanium and glass fiber. can you explain why such key components will not fail.?
I believe his carbon tensile is way too low (reckon 4-7000mpa) which is why it makes the case. You can also wrap "around" parts which is a proper way - outer surface take higher stress.
Hi, I am building a 50 foot free standing ( no wires) yacht mast. I am building a thin (22 mm) walled Douglas fir mast and want to cover it with many layers of 600 g biaxial glass and 330 g unidirectional carbon, both of which I have. Have you any recommendations to the layering. It will be hand wet lay without vacuum bagging. I expect to have a heavy mast which is fine for this application. As it is unstayed I am trying to build the mast as strong as possible. Thanks, Jim
First of all typical layers
Nomex core,3 C.F.3, Kevlar, 2 S-Glass
So if you put the C.F. in the center it would be better.
This is correct in the instance he is discussing from a load distribution standpoint. However, he is not discussing FORCE itself that must be applied to actually cause the break. He is only discussing the elongation point of breakage. If I have 3 sticks of wood at 4 mills in circumference and 1 stick in the bundle at 2 mills circumference, the over all force to break the bundle is not equal to the 2 mill nor the 4 mill pieces. This is discussing ELONGATION. Many times, carbon is added as a skin for aesthetics and stiffness while being backed by E-glass. Of course, I guess the High performance super car guys are just wrong? No. It is like anything else, it depends on the PART and what FORCES the parts are subjected to. In fairness, a video was made discussing those uses, however, he certainly doesn't seem to like Carbon Fiber and loves him some E-galss.
Interesting presentation, but are you taking the resin into account here, or just considering the material properties of the fibres?
Very helpful, TY! Layer it from most to least stiff.
What about making a composite structure of Fiberglass and Kevlar?
If I were to build a racecar's monocoque out of a mix of Fiberglass and Kevlar woven or knitted together, would the fiberglass make up for the Kevlar's weakness in compression? How much fiberglass would you need to achieve this, and would there still be enough Kevlar to give it a similar weight to Carbon Fiber?
You are the right guy to ansewer properly some old questton and myths in the 2 stroke engine industry\tuning.
-Knife edge porting of the transfers(good or bad, faster or slower flow)?
-Drilling airbox, more air or not compared to a stock airbox with a snorkel like the rotax 122 airbox.
Then what to use in the middle of the sandwich? If the outside is glass then the inside needs to be hard and light like CF, but less expensive than GF. Is there such a material?
wouldn't the fact that they are bonded together with adhesive transfer energy between them, making them more like one another and gain a little in their lacking properties?
Yeah, wasn't sure if he was trying to simplify it or whether it was an oversight. Because the carbon fiber has a higher modulus, it would see less strain. You wouldn't see 1.4% in one layer and then 4.8% in the next layer... if you did you screwed up.
krap101 when i wrote that comment i realised for the first time that the elements and materials at least in part become a new hybrid element when together than when apart. the combinations and expressions of the forces of this universe are trippy, reality / existence is trippy.
I bet in bending it's going to be close to what the video describes. Plus in many cases in real life, even if we design our structure to be purely in tension/compression, we're going to get bending anyway.
Strain would be the same across all layers. So for the same strain the carbon fiber layer will have much higher stress than the glass layers.
He wasn't saying the strain on one would be 1.4% and 4.8% on the other.
He said that the carbon fiber fails at 1.4% elongation, and the fiberglass fails at 4.8% elongation, so when the part reaches 1.4% elongation, the carbon fiber will fail, and the fiberglass will then take all the load.
My question is if you are doing this to save cost and the part is purely for cosmetics is there any reason not to do it? For example if you're making a switch plate. It's not design to take any stress but you still want the Cosmetics of carbon fiber with the added benefit of the low cost of fiberglass
Innegra video does a good job of proving Kyle's points
Am not to sure of your logic here. Are you suggesting to apply all layer in the same direction? Also makes big difference what you use for reson.
Dude....this is insanly helpful..... been trying to understand some things for weeks with lots of hours of reading but it doesnt get easier...
please i beg you, in the boat building forums i try to find some proper info, i even try to read definisions about shear strain/modulous/strenght/elongate etc....
It only gets more complicated.... can you maybe make a video talking about the SAN-PVC-PET foam cores ? my numbers dont add up. I see for example that a stiff correcell is more flexible than PET (58% vs 7%) yet PET is advertised as the future and replacement of PVC and SAN. What is going on mate....i am confused :(