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coleio
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some of you have probably seen me floating about the forum, asking silly noob questions so heres another one for you. i recently found a page that compared strength of carbon and kevlar as far as i can remember it was on two planes, rigidity and flex. or something to that effect anyhow. i cant find the page but it stated that kevlar was about 20percent less rigid but much much better when it came to breaking points and flex. so, after reading this and thinking about it for a while, taking costs into account i thought of removing carbon from the equation and going for a combination of kevlar and fibreglass. looking into it a bit more i came across this page which goes into much more detail than the first i came across http://www.performance-composites.com/carbonfibre/mechanicalproperties_2.aspso my question here is how much of these details are really relevant? i was going to look each one up but thought id ask here first. i know that with the use of kevlar, woven fibreglass and a good core material like soric sf2 i can make a product better than many aftermarket cf panels. is my thinking wrong here? Bear in mind there are some atrociously poor quality carbon panels out there oh, the application is car panels by the way, bonnets, bumpers etc...
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FLD
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These properties should really be treated as indicative measures only IMO. Far too much will depend on the moulding ability of the laminator and the resin properties.
For car panels most aftermarket ones just have an outer layer of carbon and the rest is just glass. It looks pretty which is what most people go for. If you are wanting to sell panels this is a useful approach for keeping costs down. It will depend on the aim though. If lightness is the key factor then carbon is top dog.
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wozza
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coleio (17/03/2014)
some of you have probably seen me floating about the forum, asking silly noob questions so heres another one for you. i recently found a page that compared strength of carbon and kevlar as far as i can remember it was on two planes, rigidity and flex. or something to that effect anyhow. i cant find the page but it stated that kevlar was about 20percent less rigid but much much better when it came to breaking points and flex. so, after reading this and thinking about it for a while, taking costs into account i thought of removing carbon from the equation and going for a combination of kevlar and fibreglass. looking into it a bit more i came across this page which goes into much more detail than the first i came across http://www.performance-composites.com/carbonfibre/mechanicalproperties_2.aspso my question here is how much of these details are really relevant? i was going to look each one up but thought id ask here first. i know that with the use of kevlar, woven fibreglass and a good core material like soric sf2 i can make a product better than many aftermarket cf panels. is my thinking wrong here? Bear in mind there are some atrociously poor quality carbon panels out there oh, the application is car panels by the way, bonnets, bumpers etc... thanks guys Hi, what you are proposing is exactly how quality parts should be made, the use of core materials is a fundamental part of composites. I for one won't make or sell a part that is going on the outside of a car, especially a road car that is made from pure CF. If the worst happens and a pedestrian is hit I don't want to be the reason they are pierced by shards of carbon fibre. A well designed and constructed composite part will reduce the splintering dramatically. It also makes economic sense from a business perspective. Just my opinion obviously.  Warren
Carbon Copies Ltd
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coleio
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couldnt agree more wozza. my head is wrecked trying to decide which materials and composition to use. at the end of the day its my name on the product. i had started off with the idea of 1 outer layer carbon/kevlar, reinforced with heavier carbon fabric and soric. then i was thinking a layer that goes carbon 200gsm kevlar 200gsm then soric and carbon 600gsm then there was this brain fart above. i think ill settle with carbon outer skin with fibreglass and soric reinforcing but that leaves the splintering problem. is there a really cheap material i could add to this mix to reduce the chance of splintering? without adding much weight?
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wozza
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coleio (17/03/2014)
couldnt agree more wozza. my head is wrecked trying to decide which materials and composition to use. at the end of the day its my name on the product. i had started off with the idea of 1 outer layer carbon/kevlar, reinforced with heavier carbon fabric and soric. then i was thinking a layer that goes carbon 200gsm kevlar 200gsm then soric and carbon 600gsm then there was this brain fart above. i think ill settle with carbon outer skin with fibreglass and soric reinforcing but that leaves the splintering problem. is there a really cheap material i could add to this mix to reduce the chance of splintering? without adding much weight? Soric or 3D Core is your friend in this situation. It will reduce the chances of splintering, increase the strength to weight ratio and if you a planning on using infusion then you won't need flow mesh in the stack, well not all over. For a core to work at its best it really needs to be sandwiched between equal layers. If you can try and balance the weight of reinforcement either side of the core. Warren
Carbon Copies Ltd
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coleio
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yeah i had thought about the equal fabrics either side of the core. would really annoy me if it was 200gsm cf 600gsm fg core then another 200gsm cf the best to do is cf/fg/core/fg/cf but i dont know how thick that would be, cant get my hands on the accurate thicknesses.
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Hanaldo
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Well it would be roughly 1mm on top of your core thickness. Give or take. So if you're using 2mm Soric then it will be roughly 3mm or so.
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wozza
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coleio (17/03/2014)
yeah i had thought about the equal fabrics either side of the core. would really annoy me if it was 200gsm cf 600gsm fg core then another 200gsm cf the best to do is cf/fg/core/fg/cf but i dont know how thick that would be, cant get my hands on the accurate thicknesses. My standard lay up for body panels is GC50 Gelcoat - 2x200grm CF - 3mm Soric or 3D Core - 1x 450grm CF. That gives a pretty balanced composite with a nominal thickness of 4.5mm using infusion. Wet lay would come out a bit thicker. If you want to reduce cost's you can swap the second 200grm layer of CF for Diolen as its only really there to stop the white of the core showing through on the finished part.
Carbon Copies Ltd
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coleio
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wozza (17/03/2014)
coleio (17/03/2014)
yeah i had thought about the equal fabrics either side of the core. would really annoy me if it was 200gsm cf 600gsm fg core then another 200gsm cf the best to do is cf/fg/core/fg/cf but i dont know how thick that would be, cant get my hands on the accurate thicknesses. My standard lay up for body panels is GC50 Gelcoat - 2x200grm CF - 3mm Soric or 3D Core - 1x 450grm CF. That gives a pretty balanced composite with a nominal thickness of 4.5mm using infusion. Wet lay would come out a bit thicker. If you want to reduce cost's you can swap the second 200grm layer of CF for Diolen as its only really there to stop the white of the core showing through on the finished part. i had thought about diolen briefly but couldnt find suppliers who could do 1.5m widths as cheap as fibreglass, is diolen much stronger than fibreglass? wow if that adds up to 4.5mm im probably best to reduce the fg to 400gsm. would the fibreglass show up through the 200gsm cf outer layer? i could get slated for asking this but could i spray the fibreglass layer with matt black aersol spray? or would it react?
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wozza
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Group: Forum Members
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coleio (17/03/2014)
wozza (17/03/2014)
coleio (17/03/2014)
yeah i had thought about the equal fabrics either side of the core. would really annoy me if it was 200gsm cf 600gsm fg core then another 200gsm cf the best to do is cf/fg/core/fg/cf but i dont know how thick that would be, cant get my hands on the accurate thicknesses. My standard lay up for body panels is GC50 Gelcoat - 2x200grm CF - 3mm Soric or 3D Core - 1x 450grm CF. That gives a pretty balanced composite with a nominal thickness of 4.5mm using infusion. Wet lay would come out a bit thicker. If you want to reduce cost's you can swap the second 200grm layer of CF for Diolen as its only really there to stop the white of the core showing through on the finished part. i had thought about diolen briefly but couldnt find suppliers who could do 1.5m widths as cheap as fibreglass, is diolen much stronger than fibreglass? wow if that adds up to 4.5mm im probably best to reduce the fg to 400gsm. would the fibreglass show up through the 200gsm cf outer layer? i could get slated for asking this but could i spray the fibreglass layer with matt black aersol spray? or would it react? Because the Diolen is not the "seen" layer it can be laid down in pieces from a standard width roll. Most E Glass or woven glass cures clear so you still run the risk of the core showing through, especially around any tight curves/corners etc. Not really sure how/when you plan on spraying the fg but I wouldn't be putting any rattle can products in the stack. Warren
Carbon Copies Ltd
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