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 ...
That Why you put the Carbon fiber under the first or second later of glass. Because when watten out the carbon fiber will be seen thrue the wet fiberglass
Okay so I've got a question now. when I was building a fibreglass yacht. for the helipad we use carbon double bias ,carbon quad ,fibreglass quad. fibreglass quad. carbon quad foam. then the exact same on the top but opposite starting from carbon quad up. that's how most panels are made. unless it's full carbon or full fibreglass. if your correct then why yacht companies use that carbon/fibreglass procedure? as it all gets painted so the carbon isn't for show.
I am left with more questions than answers, in theory everything sounds good,even on paper,but if we actually made some items and ran tests would the outcome of failure be as he said or as some of us predict? I was looking for info on composites for mountain boards ,skateboards and such ,trying to start a small business so I too can build a yacht for I am in the ground lol, but seriously, I thought why not do s glass with carbon, the resis would become all one unit to speak of in liquid and then when dry...your yacht is a good example of what I want to do,seems it will be safe,guess testing will tell all.
liam gibbens I think the answer is damage resistance. You can't rely on just a few layers because rock chips, sand, grit, combined with a rough landing could delaminate the structure. So in that case, think of the glass as being a sandwich core between the layers of carbon to add thickness at lower cost, with the carbon providing the necessary stiffness to handle the stress/shock of landing. then you have your foam in the middle and the plies on the bottom side which mirror the topside in order to create a balanced panel to support the weight of the aircraft.
theres another reason: carbon fibres have a slightly negative heat elongation (thats why its possible to make carbon beams with 0 heat elongation e.g. for mirrors in large telescopes) while glass has a positive one so combining them on a bonnet could end badly
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 ...
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....
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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 :)
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!
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?
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.
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.
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.
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.
Even if the carbon fiber layer is the stiffer part of your laminate it won't take 100% of the load. I guess you should invest some time into Classical Laminate Theory and Stress Strain Variation across Laminates... Also you should understand the ABD Matrix so you can predict the connection between loads and deformation for laminates before posting a video like this.
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.
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?
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.
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 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.
Cool. True, some UA-camrs 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.
This is all well meaning and good for mathamatical model's sake. But the models are mostly wrong. I've used carbon and fiberglass on surfboards for many years. Surfboards ALWAYS BREAK ! THEY ALWAYS DO !!! BUT NONE of my carbon fiber surfboards have ever broken. I always put many stringers in the foam and I have used fiberglass in between layers of carbon. Carbon always gets PINHOLES in hand layup and the fiberglass (Smallest weight) seals better than the carbon. I have also used Kevlar in between the layers. None of my carbon fiber boards have ever broken after many years of use. The worst example is waterlogging from dings.(after 15 years) This has saved me so much money because it costs $300 in carbon to lay up a board. Regular boards cost $600 to $1000 brand new...and their life span is about 6 months average. I could never afford to surf if I had to buy a new board every 6 months. I've had some carbon boards for 20 years ! I have built average one new surfboard every 2 to 3 years. Now I make kitesurfing equipment. Kite equip. has to be superlight and ext. strong. Now I have the skills to have at ~ ALOHA !!!
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.
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
Ha just want i deeded. I dont know what im doing. Time to stick with just fibreglass for now. Im still in the experimental phase to no point wasting good carbon yet
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 :(
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
Seems that Carbon fiber on the inside wrapped in s glass could be a good move...Any thoughts people smarter than me? My reasoning being that there would be less flex in the center than there would be on the perimeter in applications not needing so much compression or tensile strength but more on bending and sheer strengths. Did I do good? ha
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?
This guy does not know what he is talking about. Even carbon fibber from the 70's had a tensile strength of 4000 MPA. Modern carbon fiber is around 5800 MPA. When you start with bad data, you get bad conclusions. Find some one who knows what they are talking about (probably not going to find them on youtube!). Yes there is a strength mismatch, but the carbon will not break, it will take the load. It is also much stiffer than glass. Better solution, if you need the strength, use all carbon (and maybe sandwich construction. You'll be lighter, stiffer and stronger. And if you are building a part for show, it probably will never come close to a load high enough to worry about the strength of either material.
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.
This exact same logic would apply to any laminate composite panel, like aluminium foam sandwich panels, or in fact human skin over meat. It is wrong. You seem to miss that outer layer is not a homogenous bag over the substrate, it's cross-linked throughout its surface, and you've entirely ignored the relative Young's Modulii of the materials -- and that of the resin. Most importantly this is not whiteboard science. The only way to prove or disprove anything in the is space is with a strain gauge (Which I've done on a few occasions). Reality is the best simulation for reality.
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.
You are complete wrong, since, the fiber glass and carbon fiber reinforced with polymers are orthotropic materials (you have multiple Young Module, depending of the orientation), your approach is if these materials was isotropic. This is the reason, many thing are a mix between different materials (CF, FG, Kevlar), like helmets, beams, propulsion axles, you need to find the best material for each stress direction. Refer to MIL-17 Composite Handbook
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.
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.
Around the end you said, "dont mix and match unless you really know what your doing." So what do you think of this mixed repair job?? ua-cam.com/video/IjwHq6h-5Fk/v-deo.html
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.
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.
You are assuming that the stress exceeds the carbon while falling with the the limit of the glass. Seems niche. the resin adds properties and your "unless you know what you're doing" caveat, you know you aren't not telling the whole story. Seem like a but of a carbon fiber snob. Like the cool kid does like people playing in his back yard
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.
Too much of theoretic bs. In reality for example windsurf mast with some percentage of carbon is stronger and lighter then pure glass. Products are not made for breaking, but for working... Young modulus is way more important than max strenght.
I still would rather look at Carbon fiber then Fiber glass. Fiberglass always ends up a pissy yellow :-(. Now for the primer and paint and more labor. Not to mention more weight on my airplane wings leading edge. I agree with the science NOT the appearance. I haven't tried epoxy dye's yet maybe that will work.
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 ?
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
Annoyingly, carbon fiber as the under-layer would have some benefits (lightness and stiffness) but of course nobody wants that cos you don't get the pretty pattern.
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 ?
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?
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
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.
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.
Thats brilliant. Thanks for the discussion. I have a safety project that desperately needs a materials/composites guy to direct. I am building my first in the garage (not pyrotech, don't worry). But figuring what and where to but the EXTRA important bits is a big deal. It may not be marketable; but I have to do it for me in the interim; so there is a rush on that. PM me if it is reasonable to chat. Thanks.
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
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.
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.
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 ...
That Why you put the Carbon fiber under the first or second later of glass. Because when watten out the carbon fiber will be seen thrue the wet fiberglass
Okay so I've got a question now. when I was building a fibreglass yacht. for the helipad we use
carbon double bias ,carbon quad ,fibreglass quad. fibreglass quad. carbon quad foam. then the exact same on the top but opposite starting from carbon quad up. that's how most panels are made. unless it's full carbon or full fibreglass. if your correct then why yacht companies use that carbon/fibreglass procedure? as it all gets painted so the carbon isn't for show.
I am left with more questions than answers, in theory everything sounds good,even on paper,but if we actually made some items and ran tests would the outcome of failure be as he said or as some of us predict? I was looking for info on composites for mountain boards ,skateboards and such ,trying to start a small business so I too can build a yacht for I am in the ground lol, but seriously, I thought why not do s glass with carbon, the resis would become all one unit to speak of in liquid and then when dry...your yacht is a good example of what I want to do,seems it will be safe,guess testing will tell all.
liam gibbens I think the answer is damage resistance. You can't rely on just a few layers because rock chips, sand, grit, combined with a rough landing could delaminate the structure. So in that case, think of the glass as being a sandwich core between the layers of carbon to add thickness at lower cost, with the carbon providing the necessary stiffness to handle the stress/shock of landing. then you have your foam in the middle and the plies on the bottom side which mirror the topside in order to create a balanced panel to support the weight of the aircraft.
good video, good info! id subscribe, but looking at your videos, they are all way over my head lol.
theres another reason: carbon fibres have a slightly negative heat elongation (thats why its possible to make carbon beams with 0 heat elongation e.g. for mirrors in large telescopes) while glass has a positive one so combining them on a bonnet could end badly
I'd imagine that wouldn't be a problem, actually, as the fibers should be strong enough to counteract this. I may be mistaken though.
That's why i vinyl wrap it in carbon fiber hehe
worse sin
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 ...
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....
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.
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.
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
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.
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.
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.
but still, 1 layer of such carbon fiber can take 170kg attached and not break, and it's just 1 layer, that is epic
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
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.
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.
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.
Kyle, have you ever used basalt fibers or composites based on basalt fibers?
What is the point that your making, most of the time, ppl mix just for the look..
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.
Buy some black pigment to add to the resin for your fiberglass. Your friends will never know.
To prevent corrosion problems an outer layer of glass may be sensible.
What is the load at which the fiberglass would stretch to 1.4% ?
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 :)
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!
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.
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.
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.
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.
have no sense without study of the structure and forces what is composite are made for.
Can the carbon skinned over fiverglass delinate any different if dagaed compared to pure carbon and resin?
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.
Even if the carbon fiber layer is the stiffer part of your laminate it won't take 100% of the load. I guess you should invest some time into Classical Laminate Theory and Stress Strain Variation across Laminates... Also you should understand the ABD Matrix so you can predict the connection between loads and deformation for laminates before posting a video like this.
IEleMenTIx way to Go. Again, you are correct. The presenter does not seem to know much about compósites.
He didn't say the carbon fiber would take 100% of the load? What?
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.
your channel is amazing for FSAE team members
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?
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.
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 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.
Cool. True, some UA-camrs 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.
This is all well meaning and good for mathamatical model's sake. But the models are mostly wrong. I've used carbon and fiberglass on surfboards for many years. Surfboards ALWAYS BREAK ! THEY ALWAYS DO !!! BUT NONE of my carbon fiber surfboards have ever broken. I always put many stringers in the foam and I have used fiberglass in between layers of carbon. Carbon always gets PINHOLES in hand layup and the fiberglass (Smallest weight) seals better than the carbon. I have also used Kevlar in between the layers. None of my carbon fiber boards have ever broken after many years of use. The worst example is waterlogging from dings.(after 15 years) This has saved me so much money because it costs $300 in carbon to lay up a board. Regular boards cost $600 to $1000 brand new...and their life span is about 6 months average. I could never afford to surf if I had to buy a new board every 6 months. I've had some carbon boards for 20 years ! I have built average one new surfboard every 2 to 3 years. Now I make kitesurfing equipment. Kite equip. has to be superlight and ext. strong. Now I have the skills to have at ~ ALOHA !!!
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.
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
Ha just want i deeded. I dont know what im doing. Time to stick with just fibreglass for now. Im still in the experimental phase to no point wasting good carbon yet
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 :(
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
Seems that Carbon fiber on the inside wrapped in s glass could be a good move...Any thoughts people smarter than me? My reasoning being that there would be less flex in the center than there would be on the perimeter in applications not needing so much compression or tensile strength but more on bending and sheer strengths. Did I do good? ha
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?
awesome video! very informative than just showing "how-to" for me it's more important to answer "why" and rationale.
Good points but very flawed video
This guy does not know what he is talking about. Even carbon fibber from the 70's had a tensile strength of 4000 MPA. Modern carbon fiber is around 5800 MPA. When you start with bad data, you get bad conclusions. Find some one who knows what they are talking about (probably not going to find them on youtube!).
Yes there is a strength mismatch, but the carbon will not break, it will take the load. It is also much stiffer than glass. Better solution, if you need the strength, use all carbon (and maybe sandwich construction. You'll be lighter, stiffer and stronger. And if you are building a part for show, it probably will never come close to a load high enough to worry about the strength of either material.
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.
This exact same logic would apply to any laminate composite panel, like aluminium foam sandwich panels, or in fact human skin over meat.
It is wrong.
You seem to miss that outer layer is not a homogenous bag over the substrate, it's cross-linked throughout its surface, and you've entirely ignored the relative Young's Modulii of the materials -- and that of the resin.
Most importantly this is not whiteboard science. The only way to prove or disprove anything in the is space is with a strain gauge (Which I've done on a few occasions).
Reality is the best simulation for reality.
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.
You are complete wrong, since, the fiber glass and carbon fiber reinforced with polymers are orthotropic materials (you have multiple Young Module, depending of the orientation), your approach is if these materials was isotropic. This is the reason, many thing are a mix between different materials (CF, FG, Kevlar), like helmets, beams, propulsion axles, you need to find the best material for each stress direction. Refer to MIL-17 Composite Handbook
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.
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.
Around the end you said, "dont mix and match unless you really know what your doing." So what do you think of this mixed repair job??
ua-cam.com/video/IjwHq6h-5Fk/v-deo.html
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.
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.
You are assuming that the stress exceeds the carbon while falling with the the limit of the glass. Seems niche. the resin adds properties and your "unless you know what you're doing" caveat, you know you aren't not telling the whole story. Seem like a but of a carbon fiber snob. Like the cool kid does like people playing in his back yard
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.
Too much of theoretic bs. In reality for example windsurf mast with some percentage of carbon is stronger and lighter then pure glass. Products are not made for breaking, but for working... Young modulus is way more important than max strenght.
I still would rather look at Carbon fiber then Fiber glass. Fiberglass always ends up a pissy yellow :-(. Now for the primer and paint and more labor. Not to mention more weight on my airplane wings leading edge. I agree with the science NOT the appearance. I haven't tried epoxy dye's yet maybe that will work.
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 ?
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
Annoyingly, carbon fiber as the under-layer would have some benefits (lightness and stiffness) but of course nobody wants that cos you don't get the pretty pattern.
I'm not sure where got your numbers from but the s1 strength of CFRP is considerably higher than the s1 of gfrp...
You’re not including the stress riser that’s caused by the separation, or the potential overload from the transferred shock due to breakage.
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 ?
Solution: take some black pigments in acetone and spread the roving with it. It looks almost as carbon fiber and you have an homogeneous material!
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.
So if I understand this correctly it would make more sense to wrap carbon fiber with fiber glass for Optimal strength?
This guy obviously paid attention in math class... unfortunately for me, I didn't. LoL.
anyway I understand your theoretical explanation but I am asking you to prove it please by making a part in both ways.
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?
So, the solution is make the structure in fiberglass and glue a vinyl carbon fiber like style on top of it! LOL
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'd be better off just adding a twill weave of e-glass for the look of carbon and use a coloured gel coat to get the effect.
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.
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.
What about carbon fiber as the first or base layer, and then another couple of layers of fiberglass?
Ideally the carbon gets wrapped in the glass.
And the max strength of this without damage would be way lower than if it didn't have the carbon at all
how about a partition have carbon fiber frame and fiberglass finished outside?
You should prove your theory. Carbon Fiber is way stronger in tension than FG.
Thats brilliant. Thanks for the discussion. I have a safety project that desperately needs a materials/composites guy to direct. I am building my first in the garage (not pyrotech, don't worry). But figuring what and where to but the EXTRA important bits is a big deal. It may not be marketable; but I have to do it for me in the interim; so there is a rush on that. PM me if it is reasonable to chat. Thanks.
What if the carbon layer is in the centre, would that be stiffer but not weaker ?
Never though of that, and the carbon crack would localise a the new stress
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.
If E-Glass density were as you have written nobody would use carbon
Not information that I really needed, but it makes perfect sense.
do you have a video on cores? Say, carbon fiber with end grain balsa?
Why doesnt car manufacturing use fiberglass anymore?
Does he look high
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 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.
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.