Carbon fibre questions
10-28-08, 04:43 AM
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Carbon fibre questions
Hey guys, i half work in a composite workshop on the blackhawks and chinooks over here in aus for a defence contractor. Basically the way you repair these things is pretty basic there is no carbon on em so i have no experience with the stuff, we repair the kevlar with normal glass anyway.
Thing is i went to a composite shop and brought 3m of twill weave carbon and wanna make a few bits for my car and cant get the finish right, even under vacumn they still seem to have tiny air bubbles in the top of the skin, do you just spray em with clear coat when your done?
I have discovered the carbon is a real ***** to work with. I ripped the skin and frame outta my sun visors and am currently making little carbon ones for now just to see how hard it is to work before i get too carried away, im just using normal glass for most of it with carbon for the final layer as I cant afford to use full carbon and the first one was a complete disaster. The vac bag didn't wanna seal around the little part that connects it to the roof and it took us 45 min to get a proper seal and the resin was a bit thick by then to spread nicely. But we already came up with a way to get around that was just a stupid way to bag it first time. Anyway whats the trick to getting the best finish? I should be finished on my sun visors tomorrow, ill post some pics up lemme know what u think
Thing is i went to a composite shop and brought 3m of twill weave carbon and wanna make a few bits for my car and cant get the finish right, even under vacumn they still seem to have tiny air bubbles in the top of the skin, do you just spray em with clear coat when your done?
I have discovered the carbon is a real ***** to work with. I ripped the skin and frame outta my sun visors and am currently making little carbon ones for now just to see how hard it is to work before i get too carried away, im just using normal glass for most of it with carbon for the final layer as I cant afford to use full carbon and the first one was a complete disaster. The vac bag didn't wanna seal around the little part that connects it to the roof and it took us 45 min to get a proper seal and the resin was a bit thick by then to spread nicely. But we already came up with a way to get around that was just a stupid way to bag it first time. Anyway whats the trick to getting the best finish? I should be finished on my sun visors tomorrow, ill post some pics up lemme know what u think
10-28-08, 08:01 AM
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My father has been in composites ALL his life. 30+ Years, he and I own and run a Composite shop here in TEXAS. I would be happy to answer your questions and help you but first I need to know a few things...
What grade carbon are you working with ?? Is it a 3k, 6k, 12k ?
Whats the TG# of that carbon...
Typically inside the roll of the carbon there is a sticker with a number on it
EX: Tg-15N-20
Find that and PM the number to me. THEN I need to know what kind of RESIN system you have access to... Normal boat repair resin/all purpose resins DO NOT WORK WELL with Carbon. ALSO, If you are trying or attempting any sort of RTM or RTM Lite process involving Vaccuum you need to be aware of many diffrent aspects of the process before you begin. As you will waste a good amount of carbon with trial and error... Catalyst also plays an important role in the creation of QUALITY Carbon Fibre. Not to mention that HEAT/Humidity can play a detrimental role in your CURE/Barcol times.
This is not an area of composites you can just JUMP into and make it work either WELL or with any QUALITY finish. ALSO, If you are not using a UV Stabilized resin system the clear shine of the finished part WILL YELLOW with exposure to UV Rays. PM me if you want to chat some more, let me know what you are doing and maybe I can help you complete your project.
ONE MORE THING... It seems from your post that you are using a Vaccuum BAG (Plastic FILM over the part to contain/create your Vaccuum cavity)... There are many diffrent ways to smooth out the air pockets created by this method. However the preferred way is to NOT have AIR at all..
-DallasFC1
What grade carbon are you working with ?? Is it a 3k, 6k, 12k ?
Whats the TG# of that carbon...
Typically inside the roll of the carbon there is a sticker with a number on it
EX: Tg-15N-20
Find that and PM the number to me. THEN I need to know what kind of RESIN system you have access to... Normal boat repair resin/all purpose resins DO NOT WORK WELL with Carbon. ALSO, If you are trying or attempting any sort of RTM or RTM Lite process involving Vaccuum you need to be aware of many diffrent aspects of the process before you begin. As you will waste a good amount of carbon with trial and error... Catalyst also plays an important role in the creation of QUALITY Carbon Fibre. Not to mention that HEAT/Humidity can play a detrimental role in your CURE/Barcol times.
This is not an area of composites you can just JUMP into and make it work either WELL or with any QUALITY finish. ALSO, If you are not using a UV Stabilized resin system the clear shine of the finished part WILL YELLOW with exposure to UV Rays. PM me if you want to chat some more, let me know what you are doing and maybe I can help you complete your project.
ONE MORE THING... It seems from your post that you are using a Vaccuum BAG (Plastic FILM over the part to contain/create your Vaccuum cavity)... There are many diffrent ways to smooth out the air pockets created by this method. However the preferred way is to NOT have AIR at all..
-DallasFC1
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