How to Make a Roll Wrapped Carbon Fibre Tube

[Music] [Applause] [Music] here at easy concerts we carry a huge range of ready-made tubes but what if you're looking for something that we don't have in our stock range so maybe you need a particularly thin or thick wall or you're after a very specific diameter that we just don't carry well it's actually quite easy to manufacture your own tubes and so in this video we're going to be looking at the role wrapped manufacturing process which is particularly well suited to making straight or tapered tubes if you're looking to make more complex shapes such as this s Bend or components on a bicycle maybe handlebars or a frame you need to be looking at a molding process and we've got another video dedicated to this process specifically manufacturing tubes using the roll wrapping method isn't actually very simple and very quick to do in essence it involves tightly wrapping a prepreg reinforcement around a suitable mandrel then consolidating this using a composite shrink tape before curing it in an oven the first thing you need to consider when making a roll wrap tube is what you're going to use as the mandrel there's a few factors that are important in selecting an appropriate material for this the first is the surface finish it needs to be very smooth and consistent and also dimensionally it needs to be very accurate and true this is really important so you don't get a mechanical lock when you come to release the final part another important factor is the material that the mandrel is made from we're using aluminium and that's particularly well suited because it has a high rate of thermal expansion which means having cured at elevated temperature when it cools down it will shrink away making extraction of the final tube easier steel is also suitable but because the thermal expansion isn't quite as high as aluminium you have to pay particular attention to the surface finish and the straightness of the tube to ensure that you will get a release in common with nearly all composite manufacturing processes we need to use a release agent between the mold surface and the part we're using a chemical release agent here which is particularly well-suited because it can be used at elevated temperature and also it builds a very thin film which won't bind or impede the release on this parallel draw surface we're going to be applying around about eight applications and just using the standard method wiping a thin film on allowing that to cure between coats approximately 15 minutes and then repeating when cutting the expert prepreg material it's very straightforward to include almost any fiber type or orientation to suit your particular requirement the width should be cut to the exact circumference of the tube this will need to be extended on each wrap to allow for the increasing diameter as the layup increases in thickness this is the kit of parts for the layup so we have a 210 gram to 212 as the first layer which will be the layer that goes on the inside of the tube then we have unidirectional fiber so this is 300 gram unidirectional and all the fibers running down the length here so that will give us strength down the length of the tube and there's enough material here to do three laps around and then we're going to finish again with another layer of 210 gram 12 so on a clean surface we're going to lay out the materials so that's our first ply our unidirectional and we're just going to put a very very slight overlap to keep these tactic ever and the final layer of how to layer it well on the end there to get the material started onto the mandrel if you use some of the release paper off the back of the prepreg under the first section that will then allow you to take your mandrel firmly press down and if you rock back and forth it should tack it down onto the mandrel you can lift the paper just to help it along and then firmly press it on once it started it's very important to keep a really positive pressure all the time pressing the mandrel down onto the material that ensures that it wraps very tightly so something that can help in is a flat board over the top and as soon as you've got them prepreg there it will allow you to keep it downward pressure and roll forwards in volume production a dedicated rolling press is used for this process as this is quite short tube it's perfectly possible to do single-handed however if you're making a longer tube it would be a good idea to have more people to assist to ensure an even and firm pressure is applied if the carbon is not wrapped tightly enough it will wrinkle when the shrink tape contracts which would structurally and cosmetically compromise the part just prior to doing the shrink wrap I'm going to wrap a few extra layers of material just around the end here and what that's going to do is provide a step which if we have difficulty releasing this from the mandrel will give us something that we can hold on to and actually pull apart from the mandrel this is composites shrink tape and this consolidates the material down onto the mandrel so it's wrapped very tightly the consolidation comes in two ways first is when you actually wrap it you want to maintain a nice consistent tension and then also when it's put into the oven heat makes it contract even more which puts quite a lot of pressure onto the tube so we've got the shrink tape firmly taped in place and then we're going to just tightly wrap around leaving around a three or four millimeter step over between each one doing this by hand is quite a slow process especially on longer tubes in mass production a dedicated machine automatically winds the tape but with a little ingenuity it's also possible to adapt a standard lathe with auto feed to do the job with the partner wrapped it's ready for its final cure we're going to be using a very simple cure cycle which is 120 degrees flat now that's high enough temperature to get the shrink tape to shrink and we're going to be putting it in for an hour and a half which with the XC 110 system is plenty long enough for the resin to reach for cure the tubes now cured and as it's cooling down from being in the oven you might hear it clicking and cracking a bit and that's because of the difference in thermal expansion between aluminium and carbon fiber the aluminium shrinks much more when it cools and that will release it from the carbon and hopefully once it's fully cooled it'll be much easier to extract carbon from the aluminium mandrel in this case I expect the release to be very easy and I should just be able to pull the mandrel out by hand however if it was being more stubborn for any reason this extra bit of material I've got here you could use a bearing puller hooked over the top and actually drive it off the mandrel and so there's the completed roll wrap tube the QuickTrim and deburr to the ends will leave us with the serviceable component if we take a closer look at the finished tube you'll see we've got excellent consolidation throughout we've also got a very even wall thickness and you will notice that it has these ridges and that's what's been left by the shrink tape now that is completely normal for a roll wrap tube in our stock tubes we actually grind that surface finish out and then apply a clear lacquer so if you want a really high surface finish that is an option for you one of the main advantages to using carbon fiber before to production is its incredible mechanical strength so we're going to do a couple of non-scientific tests to see if we can establish just how strong this tube actually is so under my 75 kilos you can see the two barely deflects at all we're going to need a lot more load than this if we want to actually take it to the limit this is our mechanical test machine today I'm going to be doing a very primitive test so I'm not working to any official standards but it will tell us exactly how much load this tube can take over a 320 millimeter span in order to avoid really high concentration of stress and point loadings have made these saddles which will spread the load from the machine into the tube more evenly [Music] you can see on this stress-strain grass that the tube deflected nearly 12 millimeters before it broke but amazingly at that point it was under 700 kilos of load that's over nine times my body weight thanks for watching I hope you found the information in this video interesting and useful if you've not done so already go and check out some of our other videos where we cover a wide range of complex manufacturing processes including other methods of making carbon fiber tube and of course if you want to support our channel and encourage us to make more videos hit like and hit subscribe you

Channel: Easy Composites Ltd

Views: 1,035,442

Keywords: carbon, fibre, tube, fiber, roll wrapped, prepreg, tutorial, diy, composites

Id: vqlR74PlVgM

Length: 10min 13sec (613 seconds)

Published: Wed Apr 08 2020