Wildcard Week
Composites (Carbon Fibre)
I want to build my finalproject out of a carbon fibre exo-skeleton. This Idea came to my mind not because it is necessary, but because of the fact that we want to share how easy it is to work with.
At the very first, there was a lot of research on how to cut the untreated carbon fibre. Of course scissors would work, but there was the need for a digital fabrication technique, so I ended up using the laser cutter to get the basic shape of my parts.
Carbon fibre can be easily cut by any C02/fibre laser and won't produce any kind of dangerous gas while being cut.
To be able to actually get the carbon inside the laser, you have to measure how big of a piece you need, frame it on your stock with scotch tape and cut it out (in the middle of the tape, so the edges of your stock and the cut out piece stay suppored by it.) with a pair of sharp scissors.
After that, you can carefully take it, (it's very delicate and wants to lose its structure whenever i can.) put it on a sacrificial layer of wood and tape it to it as flat as possible.
Now it was time to actually test cutting it with the laser.
It took a little while, but I eventually managed to figure out the fastest and cleanest settings for our setup, which is Speed: 10%, Power: 100%, Frequency: 65%.
The Carbon fibre I used had interweaved strands that are arranged perpendicular to each other, they are also quite loosely packed, and therefore very fragile. That fragility is especially noticable, when you try to seperate a cut piece from the rest of the stock. More often than not I ripped my whole part (or at the very least it's edges) while trying to lift it up with a pair of tweezers. I thought a lot about that problem and tried a lot of things to remedy that, but what helped in the end was to cut everything at a 45° angle. That way the parts had much more strength because the woven pattern couldn't come apart as easily and it therefore solved my problem for up to 80% of cases.
So now that I figured out the right settings for cutting, I can cut the design I made for the rings. I made three different ones, but am only going to cut out one of them because this is just supposed to be a test.
Now let's look at actually making the composite. I used epoxy resin to create the composite, it has a mixing ratio of 100/30, where 100 parts are resin and 30 parts are hardener.
Since I don't want to waste any of the material, I mix up really small batches of roughtly 7 or 8 grams. I usually used 5 grams of resin, which called for 1,6 grams (5/3) of hardener. Once mixed, I put one of my cut out parts on a piece of ceran wrap and carefully coat it with the resin. After I have an even layer, I put the second one of my parts right on top of the first one and press it down, so it gets soaked in resin all the way and bonds with the other part. After that is done, I leave the part for a few minutes, because that way it gets easier to work with. Then I lift it up with the ceran wrap and wrap it tightly around a pipe which I cut to shape earlier to give it it's final shape.
Now it's just a matter of waiting 6-10 hours for the resin to set and then the part is done.
Small pieces of overhanging resin can simply be broken off and for a smoother sufrace finish with this technique, brushing the finished part with another layer of resin is recommended.
download the design
At the very first, there was a lot of research on how to cut the untreated carbon fibre. Of course scissors would work, but there was the need for a digital fabrication technique, so I ended up using the laser cutter to get the basic shape of my parts.
Carbon fibre can be easily cut by any C02/fibre laser and won't produce any kind of dangerous gas while being cut.
To be able to actually get the carbon inside the laser, you have to measure how big of a piece you need, frame it on your stock with scotch tape and cut it out (in the middle of the tape, so the edges of your stock and the cut out piece stay suppored by it.) with a pair of sharp scissors.
After that, you can carefully take it, (it's very delicate and wants to lose its structure whenever i can.) put it on a sacrificial layer of wood and tape it to it as flat as possible.
Now it was time to actually test cutting it with the laser.
It took a little while, but I eventually managed to figure out the fastest and cleanest settings for our setup, which is Speed: 10%, Power: 100%, Frequency: 65%.
The Carbon fibre I used had interweaved strands that are arranged perpendicular to each other, they are also quite loosely packed, and therefore very fragile. That fragility is especially noticable, when you try to seperate a cut piece from the rest of the stock. More often than not I ripped my whole part (or at the very least it's edges) while trying to lift it up with a pair of tweezers. I thought a lot about that problem and tried a lot of things to remedy that, but what helped in the end was to cut everything at a 45° angle. That way the parts had much more strength because the woven pattern couldn't come apart as easily and it therefore solved my problem for up to 80% of cases.
So now that I figured out the right settings for cutting, I can cut the design I made for the rings. I made three different ones, but am only going to cut out one of them because this is just supposed to be a test.
Now let's look at actually making the composite. I used epoxy resin to create the composite, it has a mixing ratio of 100/30, where 100 parts are resin and 30 parts are hardener.
Since I don't want to waste any of the material, I mix up really small batches of roughtly 7 or 8 grams. I usually used 5 grams of resin, which called for 1,6 grams (5/3) of hardener. Once mixed, I put one of my cut out parts on a piece of ceran wrap and carefully coat it with the resin. After I have an even layer, I put the second one of my parts right on top of the first one and press it down, so it gets soaked in resin all the way and bonds with the other part. After that is done, I leave the part for a few minutes, because that way it gets easier to work with. Then I lift it up with the ceran wrap and wrap it tightly around a pipe which I cut to shape earlier to give it it's final shape.
Now it's just a matter of waiting 6-10 hours for the resin to set and then the part is done.
Small pieces of overhanging resin can simply be broken off and for a smoother sufrace finish with this technique, brushing the finished part with another layer of resin is recommended.
download the design