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840csi
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Hi, I’m looking to make a carbon fibre bonnet for my car. First time project, have done fibreglass panels before but not carbon fibre. I watched the video on YouTube on making a bonnet using the 200gsm cloth soric cloth and 200gsm cloth. Would I be able to use 200gsm first layer and a 600gsm second layer to make the bonnet? Would this have same or better strength? Secondly roughly speaking how much resin is required per sq metre? Thanks
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Steve Broad
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+xHi, I’m looking to make a carbon fibre bonnet for my car. First time project, have done fibreglass panels before but not carbon fibre. I watched the video on YouTube on making a bonnet using the 200gsm cloth soric cloth and 200gsm cloth. Would I be able to use 200gsm first layer and a 600gsm second layer to make the bonnet? Would this have same or better strength? Secondly roughly speaking how much resin is required per sq metre? Thanks Ok, this is coming from a pure amateur and there are far more qualified people on here, but until they turn up......:-) Prepreg carbon fibre has a fibre:resin ratio of between 100:38 to 100:42 of the stuff I have used. That is for every 100gms of carbon fibre it has around 40gms of resin impregnated into it as its ideal ratio. However, when using cloth and adding resin you won't be able to get this low without the risk of voids and dry fibres. When I did wet lay up I aimed for a maximum of 50% or a little lower if possible. So, I weighed my cloth and added resin at a ratio of 100:60. This is to allow for the excess resin to be soaked up by the breather cloth when the mould is placed under vacuum. I tended to end up with around 100:45 to 100:50. However, if you are not vacuuming then the accepted ratio is 100:100 so as to make sure that all of the fibres are saturated with resin. This is what I was taught a few years ago. So, for 200gsm cloth that would be 200gms of resin per m2. if using 200 and 600gsm then that would be 800gms per m2. If you are infusing the process will sort out the amount of resin required by itself :-) but make sure that you have enough, ie make more than you think you will need so that you don't run out. With regard to how to construct the bonnet, that depends on why you are doing it. Soric is used with infusion and will give you a ligher end product than 800gms of pure carbon and it will probably be stiffer. If you are just after the carbon look and using wet layup with or without a vacuum, then 800gsm will be plenty IMO. I used two layers of 200gsm on my flip front (with some localised reinforcement) and it is fine, if a little flimsy :-)
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MarkMK
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If using a core material like Soric, you are very likely going to get 'print through' on the surface, especially if you're looking to go quite light on fabric weight. This could possibly be overcome after production with flatting and clear coat, but it would add quite a bit of additional expense and labour time. Given the heat it would likely see afterwards, which could quickly cause some shrinkage of the resin and a less than flat appearance, it would be a good idea to post-cure it and then look to have it clear-coated after flatting down again. It would mean additional time and expense, but such a part can quickly begin to look less than perfect if left to the elements without any additional steps taken, given the application.
Are you intending to mould and replicate the inner structure of the bonnet? If so, this should allow you to go a little lighter on the skin, as it will be supported much like the original. However, this calls for an additional mould to be made but might allow you to utilise fixings for the finished part more in line with the original fitment.
Large flat-ish panels on their own will be quite flexible if choosing to go with a 200g surface layer backed up by something like a 600/650g fabric. This would probably work okay with the inner structure bonded to the underside and a little additional localised reinforcement but it might be worth considering another layer of lighter fabric, at least, if you're thinking of replicating the bonnet as a single skin.
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oekmont
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"Strong" has a much more complex meaning than you might think in think.
With 800 g/m^2 combined you will have double the carbon of the 200+soric+200 layup. So your layup will be twice as strong, but ony if you try to pull the bonnet appart in a straight line. And this is not the type of load you are looking for.
The real deal here is the thickness of the layup. Your 800g will be less than 1mm in thickness, the one with soric will be almost 3,5mm. In regard of bending forces (This is the main problem here) this means the soric layup will be 49 times as rigid.
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840csi
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Group: Forum Members
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+xIf using a core material like Soric, you are very likely going to get 'print through' on the surface, especially if you're looking to go quite light on fabric weight. This could possibly be overcome after production with flatting and clear coat, but it would add quite a bit of additional expense and labour time. Given the heat it would likely see afterwards, which could quickly cause some shrinkage of the resin and a less than flat appearance, it would be a good idea to post-cure it and then look to have it clear-coated after flatting down again. It would mean additional time and expense, but such a part can quickly begin to look less than perfect if left to the elements without any additional steps taken, given the application. Are you intending to mould and replicate the inner structure of the bonnet? If so, this should allow you to go a little lighter on the skin, as it will be supported much like the original. However, this calls for an additional mould to be made but might allow you to utilise fixings for the finished part more in line with the original fitment. Large flat-ish panels on their own will be quite flexible if choosing to go with a 200g surface layer backed up by something like a 600/650g fabric. This would probably work okay with the inner structure bonded to the underside and a little additional localised reinforcement but it might be worth considering another layer of lighter fabric, at least, if you're thinking of replicating the bonnet as a single skin. Hi guys, thanks for the advise you have both given. The bonnet I’m wanting to make is for a Range Rover (Large😞) I have made my own body kit for the car and hence had to modify and make a new bonnet using fibreglass (wet laid). This came out perfect fits and looks good only problem is that it is very heavy being fibreglass. For this reason I’m wanting to take the next step and try carbon fibre to reduce weight. I have moulds for the bonnet and the under structure and will be making both parts and bonding together. I’m also looking to purchase the infusion and vacuum bagging kits here, so I can infuse it rather than wet lay. What would be best layout for the bonnet for strength and weight? eg: several layers of carbon only or carbon with soric layer using the infusion method to make parts. Thanks
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840csi
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+x"Strong" has a much more complex meaning than you might think in think. With 800 g/m^2 combined you will have double the carbon of the 200+soric+200 layup. So your layup will be twice as strong, but ony if you try to pull the bonnet appart in a straight line. And this is not the type of load you are looking for. The real deal here is the thickness of the layup. Your 800g will be less than 1mm in thickness, the one with soric will be almost 3,5mm. In regard of bending forces (This is the main problem here) this means the soric layup will be 49 times as rigid. Hi oekmont, thank you for your response. That makes sense as I will need the rigidity for the bonnet, this I think is the reason the fibreglass one is so heavy as I gave it several layers to give it strength and rigidity. Am I correct in thinking now that a 200+soric+200 layup would be more than sufficient for a bonnet as I will also have the under structure as well for added strength and rigidness which will also be made using carbon fibre. Thanks
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MarkMK
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As you're intending to replicate the inner.skin as well and bond both panels together, this will provide support.and stiffness to the whole part. If lightness is important, then a 240g surface twill (looks and handles much better) backed with a 650g backing will work well. Some additional local reinforcement around fixing points would be a good idea, plus some around the outer.lip if the support skin doesn't extend right to the edge. Going down the Soric route will give you a very rigid panel, but you'll get a very noticeable hexagon-contoured print at the surface and possibily a little more weight from the resin uptake. I don't think I'd use it personally, unless it was a single skin structiure but you.can always re-make if you're not happy with the results?
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