Curiosity is the principal driver behind many of my projects and studies. In this case I was particularly interested in carbon fiber and kevlar. Strangely, the inspiration came from watching a youtube video of someone making car parts from carbon fiber, a video which was randomly suggested but the presenter was affable made the process sound incredibly simple. Well, turns out he is mostly right. The process of laminating carbon fibre is pretty simple, and for simple projects you don't need to bother with anything as complex as vacuum bags.
What is carbon fiber?
Carbon fiber is a light material which can be made strong and stiff. Its natural form the material is found as a woven fabric which can be easily bent to any shape. It is lighter and stronger than glass fiber but also more expensive.
Typically, it is used in its woven form: a large flexible sheet of carbon fiber is made up of strands of carbon, each may be a millimetre thick but say 50 mm wide. The strands are woven in an overlapping structure which eventually provides the strength. To make the fabric stiff and strong it needs to be treated with a mix of epoxy resin (basically superglue) and a hardening substance.
What is it used for?
It is still considered an exotic material although it is edging closer to mainstream use. It features prominently in Formula One cars and in luxury / sports cars but not at the lower end of the market. That said, pretty much anything can make made out of it. It is essentially plastic.
Other cool things made from carbon fiber include bikes, boats, canoes, planes and so on. Obviously popular with transport where you need something lightweight yet strong.
How do you obtain it / work with it?
Fortunately it isn't that hard to laminate carbon fibre and starter kits can be purchased from the net. In the UK you can buy from carbonmods / easycomposites (same company). The starter kit provides everything you need: a piece of carbon fiber (and a piece of fibre glass) plus all the chemicals (which are are more than enough for the materials provided). Price is good compared to other suppliers and delivery is fast.
The company's website also provides a link to a instructional video about how to laminate the materials. I watched the video once through then watched it again as I was making up the laminate. There is a slight alteration to the video in that the chemicals are no longer mixed 50:50 but (I think) 100:30.
5 step process
1) Prepare the mould or surface of the object which you will cover with carbon fibre. Clean it up / sand it down and remove any grime/dirt. The surface probably shouldn't be porous either. Now cover this surface with releasing agent, it is important to give it a generous covering in order to allow the finished product to easily come loose. In the simple phone case that I made I actually covered my mould with brown sticky tape: the shiny side isn't naturally sticky so it helps the releasing agent do its work. This is where a porous surface would pose a problem (as well as cause potential air bubbles). Sharp edges and tight corners are not something that carbon fibre likes. Edges should be rounded and can be filled in with (something like) bathroom sealant. Carbon fibre is flexible but it doesn't do sharp corners well.
2) Let the release agent dry until it is tacky (no longer runny but not bone dry). Then cover the surface in the laminating matrix (see next paragraph). This is also supposed to be left to dry until tacky but I think you could potentially avoid putting down this layer, or you can not leave it to dry for so long.
3) Put 100g of epoxy resin into a plastic container. Add 30g of Hardener. Mix vigorously, making sure to scrape any residue from the walls of the container. This is the matrix that laminates the carbon fibre.
Paint can be added for colour but otherwise you should have a clear resin. If left unattended/unused then this matrix mixture will eventually hardened and become unusable. This is one problem that I found when I put down my initial layer of matrix: I left it to dry until tacky but in doing so the left over matrix in the pot had hardened and wasted the remaining mix. Fortunately it wasn't a lot but I had hoped to be able to just mix up one batch and then use that for the entire process. In a later experiment I think I didn't wait for the first laminate layer to fully dry and the result was mostly fine.
4) Place the carbon fibre onto the mould and then brush matrix on to it with an even covering. Place down more layers of carbon fibre as necessary and with each layer apply more matrix. Then leave it to dry for at least 8 hours, although 24 hours should remove all doubt.
5) Removing the newly created reinforced carbon fibre from the mould can be tricky and is partly related to how much releasing agent you put down. It is tricky but it shouldn't be incredibly difficult. Take a look at some videos on youtube and then gauge how difficult it should be.
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Last Updated (Saturday, 17 August 2013 13:44)
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